Stereochemistry of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium

Accepted Manuscript Title: Stereochemistry of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium Authors: Ruven L. Davidovich Dmitry V. Marinin Vitalie Stavila Kenton H. Whitmire PII: DOI: Reference:

S0010-8545(13)00140-9 http://dx.doi.org/doi:10.1016/j.ccr.2013.06.016 CCR 111740

To appear in:

Coordination Chemistry Reviews

Received date: Revised date: Accepted date:

6-5-2013 26-6-2013 27-6-2013

Please cite this article as: R.L. Davidovich, D.V. Marinin, V. Stavila, K.H. Whitmire, Stereochemistry of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium, Coordination Chemistry Reviews (2013), http://dx.doi.org/10.1016/j.ccr.2013.06.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Review

Stereochemistry of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium Ruven L. Davidovich,a,* Dmitry V. Marinin,a Vitalie Stavila,b Kenton H. Whitmirec,** Institute of Chemistry, Far-Eastern Branch, Russian Academy of Sciences, 159 Prosp. 100-Letiya Vladivostoka,

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a

690022 Vladivostok, Russia

Sandia National Laboratories, MS-9161, 7011 East Avenue, Livermore, CA 94551, USA

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Department of Chemistry, MS-60, Rice University, 6100 Main Street, Houston, TX 77005, USA

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b

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Contents Abstract

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1. Introduction

2. Structures of fluoride complexes of zirconium and hafnium 2.1. Framework structures 2.3. Chain structures 2.5. Dimeric structures

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2.4. Oligomeric structures

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2.2. Layered structures

2.6. Monomeric structures

3. Structures of mixed-ligand fluoride complexes of zirconium and hafnium

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3.1. Structures of anionic mixed-ligand fluoride complexes of zirconium and hafnium 3.1.1. Layered structures 3.1.2. Chain structures

3.1.3. Dimeric structures

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3.1.4. Monomeric structures

3.2. Structures of coordination compounds ZrF4 and HfF4 with neutral O- and N-donor ligands

3.2.1. Structures of coordination compounds ZrF4 and HfF4 with O-donor ligands 3.2.1.1. Chain structures 3.2.1.2. Dimeric structures 3.2.1.3. Monomeric structures 3.2.2. Structures of coordination compounds ZrF4 and HfF4 with N-donor ligands

4. Conclusions Acknowledgements References ___________________________________________________________________________________________

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Abbreviations: CN, coordination number; V, vertex; E, edge; TF, triangular face; SAPR-8, square antiprism; PBPY7, pentagonal bipyramid; DD-8, dodecahedron; TPRS-7, monocapped trigonal prism; OCF-7, monocapped octahedron; TPRS-8, bicapped trigonal prism; OC-6, octahedron; [H2(en)]2+, ethylenediammonium dication; [NH3Me]+, [Hmeam]+, methylammonium cation; [H(gly)] +, glycinium cation; [H(ala)]+, alaninium cation; [H2dap]2+, propane-1,2-diaminium dication; [H2dabco]2+, 1,4-diazabicyclo(2.2.2)octane dication; (CH7N4)+, aminoguanidinium monocation; [NHMe3]+, trimethylammonium cation; [NEt4]+, tetraethylammonium cation; [H(ida)]+, iminodiacetic acid cation; L, ligand; Lʹ, 4,4ʹ-bipyridine-N,Nʹ-dioxide; [H2(pipz)]2+, piperazinium dication; (CH8N4)2+, aninoguanidinium dication; [H2bpz]2+, 4,4ʹ -bipyrazolium dication; tren, tris-(2-aminoethyl)amine; en, ethane-1,2diamine; HD-, dimethylglyoxime monoanion; Sam, para-aminobenzenesulfamide (sulfanilamide); Anil, aniline; (HNiox)-, 1,2-cyclohexanedionedioxime monoanion; tu, thiourea; [NMe 4]+, tetramethylammonium cation; [H(en)] +, ethylenediammonium monocation; [NH2Me2]+, dimethylammonium cation; (18-C-6), 18-crown-6; (A18C6), aza-18crown-6; (DA18C6), diaza-18-crown-6; (C2H5N4)+, 4-amino-1,2,4-triazolium cation; dmso, dimethyl sulfoxide; 2,2ʹ-bpy, 2,2ʹ-bipyridine; IDiPP-1,3-(2,6-di-isopropylphenyl)imidazol-2-ylidene; OPPh3, triphenylphosphine oxide; OAsPh3, triphenylarsine oxide; OPMe3, trimethylphosphine oxide; dmf, dimethylformamide; thf, tetrahydrofuran.

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* Corresponding author. Tel.: +7 423 2311 889; fax: +7 423 2311 889. ** Corresponding author. Tel.:+1 713 348 5650; fax: + 1 713 348 5155. E-mail addresses: [email protected] (R.L. Davidovich), [email protected] (K.H. Whitmire).

ABSTRACT

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As a continuation of the published reviews dedicated to the stereochemistry of fluoride complexes (1998) and mixed-ligand fluoride complexes of zirconium and hafnium (1999), the stereochemistry of 93 fluoride and 34 mixed-ligand fluoride complexes of zirconium and hafnium, whose structures were

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published since 1998, has been considered. The structure of complex anions (complexes) of structurally studied fluoride and mixed-ligand fluoride complexes of zirconium and hafnium and the dependence of the structural motif of the complex anion (complex) on the F(L):Zr(Hf) ratio in the compound and the

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central atom coordination number have been discussed. Comprehensive tables containing the chemical formula of the compound, the configuration of the central atom polyhedron reflecting its coordination number, polyhedron composition, the structural motif of the complex, the character of polyhedra association in the structure, and references are presented.

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Keywords: zirconium, hafnium, fluoride complex, mixed-ligand, crystal structure

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1. Introduction

Significant success has been achieved in recent years in chemistry and structure of metal fluoride complexes, in particular of hybrid organic-inorganic fluoride complexes [1]. A multitude of structures have been isolated, including monomers, dimers, oligomers and

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coordination polymers of various dimensionality [1,2]. Unlike fluoride complexes of titanium(IV) and the group V and VI transition metals, zirconium and hafnium fluoride complexes have contributed greatly to the observed structural diversity, displaying a particularly

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rich and interesting stereochemistry with various coordination numbers (6, 7, and 8) and different structural motifs [3,4].

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In addition to the fundamental interest in elucidating the topological relationship between the structure of zirconium and hafnium fluoride complexes and the nature of the counter-ion and

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reaction conditions, these compounds and the fluoride glasses based on them have many important practical applications. Due to the low phonon energies and high optical transparency,

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fluoridozirconate glasses are potential candidates for optical telecommunication devices, optical fibers, up-conversion lasers, optical amplifiers, and sensors [5]. Moreover, various fluoride complexes of Zr(IV) and Hf(IV) have been examined in recent years for their potential use as

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ionic conductors [6], ferroelectrics [7] and luminophores [8,9]. Therefore, understanding the structure-property relationship for zirconium and hafnium fluoride complexes has a cardinal

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importance in rational design of a material’s properties. The stereochemistry of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium studied prior to 1998 was considered in [3] and [4], . Since the publication of the abovementioned reviews [3,4], a number of papers devoted to studies of crystal structures of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium have appeared. The present

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review discusses the stereochemistry of these complexes. The systematization of the recently reported crystal structures of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium has been performed on the basis of the structural motif of the compound complex anion (complex): from polymer to oligomer, dimer and monomeric species, and the correlation with the observed F(L):Zr(Hf) ratio in the compounds. The comprehensive Tables contain the chemical formula of the compound, the configuration of the central atom polyhedron reflecting its coordination number (CN), polyhedron composition, the structural motif of the complex, the character of polyhedra association in the structure, and references.

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2. Structures of fluoride complexes of zirconium and hafnium

The structurally studied fluoride complexes of zirconium and hafnium and their stereochemical characteristics are presented in Table 1.

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Table 1 here

Fluoride complexes of zirconium and hafnium with the F:Zr(Hf) ratio in the range from 4 to

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5 have not yet been structurally studied. So far, only the synthesis of ammonium fluoridozirconate NH4Zr2F9 obtained in the form of rosette-like aggregates was described [59].

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The compound’s powder X-ray pattern, IR spectrum, and the data of thermal decomposition in

possibility of its thermal conversion into ZrO2. Framework structures

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2.1.

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nitrogen atmosphere and in air were presented. The compound was investigated to test the

In the structures of fluoride complexes of zirconium and hafnium, the formation of a framework motif is realized by linking metal fluoride polyhedra to each other through all or a

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major part of fluorine atoms that have the role of bridges. In these structures, cations are located in the framework voids or channels. Only a few crystal structures of fluoride complexes of

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zirconium and hafnium having the framework anion structure have been studied. In the series of structurally studied fluoride complexes of zirconium and hafnium with the ratio F:Zr(Hf)=5, only the compound Ag7Zr6F31 [10] has a framework structure similar to that of Na7Zr6F31 [60]. As in the structure of Na7Zr6F31, the Zr atom in Ag7Zr6F31 is surrounded by eight F atoms forming a square antiprism polyhedron. Six of these coordination polyhedra are linked

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through F atom vertices forming an octahedron with a disordered F atom in its center. Each of these octahedra is linked to six similar ones, thus forming a framework structure. In the structure of Ag7Zr6F31, the Ag(1)+ cations are surrounded by six F atoms in a distorted octahedral arrangement, whereas the Ag(2)+ cations are coordinated by eight F atoms. From the powder Xray data, the compound Ag7Hf6F31 [10] is isotypic to Ag7Zr6F31. The compound KVZrF7 [11] is isotypic to KPdZrF7 [61]. The main structural unit of KVZrF7 constitutes double VZrF11 polyhedra formed from octahedral VF6 and pentagonalbipyramidal ZrF7 units that share a common edge. Through the common F vertex, the double VZrF11 polyhedra are linked into layers, which, in their turn, are linked into a three-dimensional structure through trans-fluorine atoms. The K+ cations are located in the structure channels. In

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5 the pentagonal-bipyramidal ZrF7 polyhedron, the Zr-F bond lengths fall into the range 1.9492.116 Å. Synthesis and crystal structures of four fluoridozirconates ABZrF7 (A = Rb, Tl, B = Ca, Cd) have been described [12]. The structures of RbCdZrF7 and TlCdZrF7 were determined by singlecrystal X-ray diffraction, whereas the structures of RbCaZrF7 and TlCaZrF7 were found from Xray powder patterns using the Rietveld method [62]. In all four structures the B2+ and Zr4+

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cations are seven-coordinate, forming nearly regular pentagonal bipyramids. Each pentagonal bipyramid ZrF7 or BF7 shares two edges with two adjacent BF7 or ZrF7 pentagonal bipyramids

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and three vertices with three other BF7 or ZrF7 ones. By sharing common edges, the alternating ZrF7 and BF7 pentagonal bipyramids form infinite zigzag chains along the a direction.

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Furthermore, the chains linked by a common F-vertex form BZrF11 layers that are linked into a three-dimensional framework. Along the c direction, the structure contains pseudo hexagonal channels containing Rb+ or Tl+ cations.

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Crystals of Ag2ZnZr2F14 [13], isotypical to those of Ag3Zr2F14 (Ag(1)2Ag(2)Zr2F14) [63], were also studied by the Rietveld method [62]. The Zn atoms in the structure occupy the

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positions of Ag(2) in Ag(1)2Ag(2)Zr2F14 and are surrounded by 6 F atoms, thus forming slightly compressed ZnF6 octahedra. The Ag2+ ions form square-plane AgF4 units. By linking through a common vertex, the AgF4 units form Ag2F7 dimers. In their turn, these dimers are linked with

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dimensional structure.

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discrete ZnF6 octahedra and ZrF7 pentagonal bipyramids with the formation of a three-

Layered structures

A number of fluoride complexes of zirconium and hafnium with the ratio F:Zr(Hf)=5 have a layered structure. The compound RbHfF5 was obtained in the form of colorless crystals as a side

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product during studies of the synthesis of RbCuZrF7 and RbCuHfF7, and its crystal structure was determined [14]. The monoclinic crystals are isotypic to monoclinic (NH4)ZrF5 [64] and TlZrF5 [65]. The coordination polyhedron of the Hf atom in the structure of RbHfF5 can be described as a slightly distorted dodecahedron. The Hf-F distances fall into the range 1.999-2.195 Å. Two HfF8 polyhedra share a common edge, form a bipolyhedron, which is linked by common vertices to four other HfF8 dodecahedra. In this way, layers parallel to (100) are formed with rubidium ions surrounded by 11 F atoms located between them. A number of hybrid organic-inorganic fluoride complexes of zirconium have layered crystal structures. The compound [H2(en)]Zr2F10H2O synthesized from the HF solution [66] was obtained as a crystal powder, which prevented determining its crystal structure. Crystals of [H2(en)]Zr2F10·H2O were obtained by a hydrothermal method and its structure was investigated Page 5 of 59

6 by single-crystal X-ray diffraction [15]. The zirconium atoms in the structure are dodecahedral. The ZrF8 polyhedra share three common edges with neighboring dodecahedra to form polymer layers [(Zr2F10)2-]∞ (Fig. 1) separated by ethylenediammonium(2+) cations and H2O molecules. Fig. 1 here

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Each ZrF8 polyhedron contains two terminal F atoms located between the layers. The lengths of the terminal Zr-F bonds fall into the range 1.958(1)-2.018(1) Å, whereas the lengths of the Zr-F bridge bonds change from 2.076(1) up to 2.291(1) Å. In [H2(en)]Zr2F10 H2O, the

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terminal fluorine atoms hydrogen bond to the cations [H2(en)]2+ (N∙∙∙F 2.741(5)-2.871(5) Å). The

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water oxygen atom forms four hydrogen bonds with lengths O···N(F) 2.689(5)-2.862(5) Å. Hybrid organic-inorganic compounds [NH3Me]ZrF5·0.5H2O, [H(gly)]ZrF5·2H2O, and [H(ala)]ZrF5 [2,16] (Table 1) have crystal structures similar to the polymer layered structure of

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[H2(en)]Zr2F10·H2O. The structures of these compounds are formed from planar polymer anion layers [(ZrF5)-]∞ and layers located between them that contain the protonated organic cations and

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H2O molecules. As in the layered structure of [H2(en)]Zr2F10·H2O, the anionic polymer layers in [NH3Me]ZrF5·0.5H2O, [H(gly)]ZrF5·2H2O, and [H(ala)]ZrF5 are built up from ZrF8 units having a slightly distorted dodecahedral configuration. Each zirconium polyhedron has three common

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edges with three neighboring polyhedra, thus forming hexanuclear rings. The structures of [NH3Me]ZrF5·0.5H2O, [H(gly)]ZrF5·2H2O, and [H(ala)]ZrF5 [2,16] are similar to those of

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(H3O)ZrF5·H2O and (H3O)ZrF5·2H2O [67].

The crystal structure of [NH3Me]ZrF5·0.5H2O denoted in [17] as [Hmeam]2(Zr2F10)·H2O was studied independently. The results obtained in [17] are in good agreement with the [NH3Me]ZrF5·0.5H2O data [16]. In addition to the crystal structure of [Hmeam]2(Zr2F10)·H2O

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[17], the structure of [H2dap](Zr2F10)·H2O was described; the latter also displays a polymer layered structure, but different from that of [Hmeam]2(Zr2F10)·H2O. The structure of [H2dap](Zr2F10)·H2O [17] is built up from Zr(1)F7 and Zr(2)F8 polyhedra,

[H2dap]2+ cations, and H2O molecules. The Zr(2)F8 polyhedra, sharing opposite edges, form infinite [Zr(2)F6]∞ chains. Two Zr(1)F7 polyhedra linked by a common edge form dimers (Zr(1)2F12). The latter are linked to [Zr(2)F6]∞ chains with the formation of polymer layers [(Zr2F10)2-]∞, in which polyhedra form ten-membered rings with rectangular windows of ~710 Å2. The [H2dap]2+ cations and H2O molecules are located between the [(Zr2F10)2-]∞ layers as well. The compounds K3Ag2Zr4F23 and K3Ag2Hf4F23 with the ratio F:Zr(Hf)=5.75 adopt layered crystal lattices as well. The structure of K3Ag2Zr4F23 [18] contains two crystallographically Page 6 of 59

7 independent Zr atoms, each dodecahedrally surrounded by eight fluorine atoms. The Ag2+ polyhedra have the configuration of a distorted pentagonal bipyramid. The two independent Zr(1)F8 and Zr(2)F8 polyhedra share a common F-F edge, forming double Zr2F14 dodecahedra. The double Zr2F14 dodecahedra are linked into zigzag chains. Two bridging F atoms link the chains into layers parallel to <101>. The layers, in their turn, are linked through bridging F atoms of Ag2+ and Zr polyhedra into a three-dimensional structure containing hexagonal channels

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occupied by K+ cations. From the X-ray powder data, K3Ag2Hf4F23 is isotypic to K3Ag2Zr4F23

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[18].

2.3. Chain structures

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A large number of Zr and Hf fluoride compounds possess chain structures in which the F:Zr(Hf) ratio changes in the range 5-6. The compound [H2dabco](Zr2F10)·1.5H2O [19] is composed of ZrF7 and ZrF8 polyhedra, just like that of [H2dap](Zr2F10)·H2O [17]. The character

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of their linking is different in the structure [H2dabco](Zr2F10)·1.5H2O, as compared to that of [H2dap](Zr2F10)·H2O. The structure of [H2dabco](Zr2F10)·1.5H2O consists of infinite double

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chains [(Zr2F10)2-]∞ separated by [H2dabco]2+ cations and water molecules. Two independent zirconium atoms in the structure have the coordination numbers 7 (Zr(1)) and 8 (Zr(2)). The Zr(1)F7 polyhedra comprise slightly distorted pentagonal bipyramids, whereas the Zr(2)F8 are

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trigonal dodecahedra. Two Zr(2)F8 polyhedra share one edge to form dimers (Zr2F14F2/2). Two adjacent dimers are linked to two Zr(1)F7 polyhedra, resulting in the formation of double

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polymer chains. The chains are comprised of prolonged hexagonal rings similar to those in polymer layered structures [(Zr2F10)2-]∞ built form ZrF8 polyhedra [15-17]. N-H···F hydrogen bonds link the [H2dabco]2+ cations in two inorganic chains. The cations and the [(Zr2F10)2-]∞ double polymer chains form infinite pseudo-layers linked by O-H···F hydrogen bonds into a

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framework.

The compound (CH7N4)ZrF5 has a polymer chain structure [68]. It is built up from separated

infinite chains [(ZrF5)-]∞ directed along the x axis and aminoguanidinium(1+) cations located between the chains. The polyhedron of the zirconium atom in the structure comprises a slightly distorted pentagonal bipyramid. The ZrF7 polyhedra sharing common F-F edges are linked into infinite chains. N-H···F hydrogen bonds link the chains into a three-dimensional framework. The crystal structure of (CH7N4)ZrF5 was repeatedly studied on several single crystals [20]. Corrected data on the structure and its geometrical characteristics were obtained. Polymeric chains [(ZrF5)-]∞, similar to those in (CH7N4)ZrF5, were found for [NHMe3]ZrF5, [NEt4]ZrF5·0.5H2O, and [H(ida)]ZrF5·H2O [2] (Table 1). A large group of coordination polymers with 4,4ʹ-bipyridine-N,Nʹ-dioxide, where Lʹ Page 7 of 59

8 4,4ʹ-bipyridine-N,Nʹ-dioxide, have been described [21]. One particular example is the compound [{Cu(OHMe)2(-Lʹ)}2](ZrF5)2. According to [21], the (ZrF5)- anion is formed in situ from the [ZrF6]2- dianion and has a chain structure built from vertex-linked octahedra. Indeed, the polymeric chains [(ZrF5)-]∞ in the structure of [{Cu(OHMe)2(-Lʹ)}2](ZrF5)2 (Fig. 2) are built up from seven-coordinated polyhedra linked through common edges as in the (CH7N4)ZrF5

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[68].

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Fig. 2 here

The compounds NaTiHf2F11, NaVHf2F11 [11], and NaVZr2F11 [69] with the ratio F:Zr(Hf) =

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5.5 are isotypic to AgPdZr2F11 [70] and have a polymer chain structure. The Hf atoms in NaTiHf2F11 and NaVHf2F11 are surrounded by seven fluorine atoms form distorted pentagonalbipyramidal polyhedra. The HfF7 polyhedra are linked by shared F-F edges into Hf2F12

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bipolyhedra. Common vertices (bridging F atoms) link the bipolyhedra into infinite chains, between which the Na+ and MII (Ti2+, V2+) cations are located.

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The crystal structures of fluoride complexes of zirconium and hafnium have a general formula MMʹ4A3F17·2HF: Li(NH4)4Zr3F17·2HF, LiRb4Zr3F17·2HF, Na(NH4)4Zr3F17·2HF, and

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NaCs4Hf3F17·2HF, and are built up from polymer chains formed from trinuclear fragments A(1)F7-A(2)F8-A(3)F7 [22] (Table 1). The coordination polyhedron of the A(1) atom is a monocapped trigonal prism A(1)F7, the A(2)F8 polyhedron has a dodecahedral configuration,

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and the A(3)F7 polyhedron comprises a pentagonal bipyramid. The A(2)F8 polyhedron is linked to A(1)F7 and A(3)F7 polyhedra through common edges. The trinuclear fragments are linked into the polymer chain through common vertices. The Li and Na atoms link the polymer chains into layers. In their turn, the layers are linked by strong hydrogen bonds F-H···F (2.323-2.370 Å)

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formed with the participation of HF molecules. The F:Zr(Hf) ratios in the compounds Li(NH4)6Zr4F23 [23] and K3Ag2Zr4F23 [18] are

identical (5.75), but the structures of these compounds are fundamentally different. Li(NH4)6Zr4F23 is built up from polymer chains [(Zr4F23)7-]∞ and NH4+ and Li+ cations located between the chains. Two crystallographically independent Zr atoms form coordination polyhedra Zr(1)F8 and Zr(2)F7 having configurations of a dodecahedron and monocapped trigonal prism, respectively. In the polymer chain, one can observe tetranuclear fragments -(Zr(2)F7-Zr(1)F8Zr(1)F8-Zr(2)F7)-. Within the fragment, the coordination polyhedra are joined by common edges, while common vertices link the fragments into polymer chains. The compound LiK10Zr6F35·2H2O [24] has also a polymer chain structure built from infinite chains [(Zr6F35)11-]∞, K+ and Li+ cations, and H2O molecules. The structure of LiK10Zr6F35·2H2O Page 8 of 59

9 contains 6 crystallographically independent Zr atoms. One of them (Zr(6)) has CN = 8 and forms a distorted trigonal dodecahedron. The remaining Zr atoms are surrounded by seven F atoms forming distorted monocapped octahedral coordination polyhedra. In the polymer chain [(Zr6F35)11-]∞, one can mark out two types of trinuclear fragments. One of them is composed of polyhedra Zr(1)F7-Zr(2)F7-Zr(3)F7 linked through common vertices. In the second trinuclear fragment Zr(4)F7-Zr(6)F8-Zr(5)F7, the polyhedra share common edges. The trinuclear fragments

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are linked into a polymer chain through common vertices. The trinuclear fragment Zr(4)F7Zr(6)F8-Zr(5)F7 in LiK10Zr6F35·2H2O is structurally similar to the A(1)F7-A(2)F8-A(3)F7

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fragment in the polymer chain structure of MMʹ4A3F17·2HF (A - Zr, Hf) [22].

The crystal structure of Li2ZrF6 [25,26] obtained under high pressure (11 GPa) and high

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temperature (1063 K) was investigated by synchrotron X-ray powder diffraction. At normal conditions, the Li2ZrF6 crystals are hexagonal and are composed of octahedral LiF6 and ZrF6 groups [71]. Above 10 GPa, Li2ZrF6 transforms into a new polymorph, in which the Zr

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coordination polyhedron comprises a distorted square antiprism, whereas the Li atoms have octahedral coordination. The LiF6 octahedra form layers parallel to (100) linked by common

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edges to zigzag chains of zirconium polyhedra.

The crystal structure of K2ZrF6 was re-determined and the structure of mixed crystals K2-x(NH4)xZrF6 (x = 0.244, 0.782, 1.520, and 1.619), in which ammonium cations substitute

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potassium cations, were investigated [27] (Table 1). The mixed crystals K1.756(NH4)0.244ZrF6 are isostructural to K2ZrF6 [72]. The crystal structure of mixed crystals K1.218(NH4)0.782ZrF6 is built

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up from ZrF8 dodecahedra linked through common F-F edges into linear polymer chains. The structure contains four crystallographically independent cation positions, in which ammonium cations statistically replace those of potassium. In contrast, mixed crystals K0.480(NH4)1.520ZrF6 and K0.381(NH4)1.619ZrF6 are isostructural to (NH4)2ZrF6 [73], with the potassium cations

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statistically substituted for the ammonium cations. Mixed crystals of rubidium-ammonium hexafluoridozirconates Rb0.322(NH4)1.678ZrF6, Rb0.416(NH4)1.584ZrF6, and Rb0.447(NH4)1.553ZrF6, which are isostructural to (NH4)2ZrF6 [73], are also known [28]. The compound MgZrF6·5H2O [29] is isostructural to MnZrF6·5H2O [74,75]. It is built from

infinite chains formed by ZrF8 dodecahedral units linked through common F-F edges. Octahedral MgF2(H2O)42+ cations and uncoordinated H2O molecules reinforce the chains. A polymer crystal structure was observed in the recently reported Li2Mg(ZrF6)24H2O [30]. Similar to MgZrF65H2O, the structure consists of infinite linear chains, built from dodecahedral ZrF8 polyhedra connected by shared F-F edges. The polymeric chains in turn form a threedimensional framework of MgF4(H2O)2 octahedra and LiF4(H2O) square pyramids. Slightly bent chains formed from edge-sharing distorted bicapped trigonal prismatic ZrF8 Page 9 of 59

10 and Sn2+ cations constitute SnZrF6 [31]. The isolated chains of zirconium polyhedra are linked into layers through Sn atoms. Although in the isostructural compounds (NH4)SnZrF7 and KSnZrF7 [32] the ratio F:Zr(Hf) is 7, their structures are designated as hexafluorocomplex structures. The crystal structures of (NH4)SnZrF7 and KSnZrF7 contain infinite zigzag chains built from ZrF8 polyhedra that share common F-F edges. The coordination polyhedron of the Zr atom comprises a distorted dodecahedron. The Sn atoms are linked into dimers through fluorine

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atoms not coordinated by the zirconium atom. The polyhedra of Sn atoms are bonded to the zirconium atoms via three bridging fluorine atoms, thus linking the isolated polymer zirconium

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chains into a framework. The outer-sphere cations are located in the framework channels. In the isostructural compounds KCuZrF7 and KCuHfF7 [33] the F:Zr ratio is 7, just like in

us

(NH4)SnZrF7 and KSnZrF7. In the KCuZrF7 and KCuHfF7 structures the Zr atoms coordinated by eight F atoms form strongly distorted cubic antiprisms. The octahedral Cu2+ cations are surrounded by six fluorine atoms and linked via common vertices into zigzag chains. The ZrF8

an

polyhedra share common edges and form zigzag chains as well. Both types of zigzag chains share a common F-F edge form layers. The layers are linked into double layers through a

M

common vertex. The K+ cations are located in the hexagonal channels formed in the structure. Zigzag polymer chains [(ZrF6)2-]∞ built from dodecahedral ZrF8 groups that share opposite edges with neighboring units form the crystal structure of [H2(pipz)]ZrF6·H2O [15]. The

ed

protonated piperazinium dications and H2O molecules responsible for the formation of a hydrogen bonding network are located between the chains.

ce pt

The compound (NH3OH)2HfF6 [34] is isomorphic to (NH3OH)2ZrF6 [76]. In the former, the HfF8 dodecahedra share common F-F edges forming polymer chains bound together by hydrogen N-H···F and O-H···F bonds.

Ac

2.4. Oligomeric structures

The crystal structure of [HIDiPP]3[M3F15]·4thf·0.55CH2Cl2 (M = Zr, Hf) (IDiPP - 1,3-(2,6

diisopropylphenyl)imidazol-2-ylidene) [35] is composed of [HIDiPP]+ cations, trimeric cyclic complex anions [M3F15]-, and solvate tetrahydrofuran and CH2Cl2 molecules. The formation of discrete trimeric cyclic complex anions [M3F15]-, that are composed from octahedral MF6 units linked by two cis-vertices (Fig. 3), was established for the first time.

Fig. 3 here

The compounds [Co(NH3)5(H2O)]2[Zr3F18]·6H2O and [Co(NH3)6]2[Zr3F18]·6H2O have Page 10 of 59

11 isotypic structures built up from octahedral complex cations [Co(NH3)5(H2O)]3+ or [Co(NH3)6]3+, isolated trimeric chain complex anions [Zr3F18]6-, and lattice water molecules [36]. In the [Zr3F18]6-, the terminal Zr atoms are seven-coordinate and form distorted pentagonal-bipyramidal polyhedra. The central Zr atom is coordinated by eight F atoms forming of a distorted square antiprism. Trimeric chain complex anions [Zr3F18]6- in both are structurally similar to those found in MMʹ4A3F17·2HF [22]; however, for these compounds the trimeric anions [Zr3F18]6- are share common vertices to produce a polymer chain (Table 1).

ip t

isolated, whereas in the structure of MMʹ4A3F17·2HF the trimeric fragments -ZrF7-ZrF8-ZrF7-

cr

Isolated tetrameric cyclic [Zr4F24]8- anions (Fig. 4) were established for the first time in the

Fig. 4 here

us

crystal structure of (CH8N4)ZrF6·H2O [77].

an

The structure of (CH8N4)ZrF6·H2O was re-determined [37] to correct the compound synthesis conditions and the localizations of hydrogen atoms that had not been located

M

previously [77]. All fluorine atoms in this compound, beside the bridging ones, form hydrogen bonds with H···F distances ranging from 1.760(3) up to 2.080(3) Å. The oxygen atoms of the

ed

H2O molecules form hydrogen bonds with O∙∙∙F distances from 2.678(18) up to 2.999(7) Å. 2.5. Dimeric structures

ce pt

A large group of zirconium and hafnium hexafluorocomplexes have dimeric structures with the coordination number of the central atom equal to 7. The compound K2[Ni(H2O)6][ZrF6]2 [38] is isostructural to K2[Cu(H2O)6](ZrF6)2 [78] and K2[Zn(H2O)6](ZrF6)2 [79]. The structure is built up from K+ cations, slightly elongated

Ac

octahedral complex cations [Ni(H2O)6]2+ and isolated dimeric complex anions [Zr2F12]4-. This anion is formed from the association of two distorted pentagonal-bipyramidal ZrF7 coordination polyhedra sharing an equatorial F-F edge. The [Ni(H2O)6]2+ cations and [Zr2F12]4- anions are linked into a three-dimensional structure by eight-coordinated K+ cations. A branched system of hydrogen bonds O-H···F with the distances in the range 2.6375(13)-3.4527(16) Å stabilize the structure. Dimeric complex anions [Zr2F12]4- similar to that in K2[Ni(H2O)6][ZrF6]2 are found in Cs2[Zn(H2O)6](ZrF6)2 [39] and ferroelastic Cs2[Cu(H2O)6](ZrF6)2 [40]. Ferroelasticity is a phenomenon in which a material exhibits a spontaneous strain due to a phase change. When stress is applied to a ferroelastic material, a phase transition between ferroelastic and paraelastic states occurs. At room temperature, the structure of Cs2[Cu(H2O)6](ZrF6)2 is monoclinic and Page 11 of 59

12 isomorphic to K2[Cu(H2O)6](ZrF6)2 [78]. Around 320 K, the crystals of Cs2[Cu(H2O)6](ZrF6)2 undergo a ferroelastic phase transition with a change to rhombic symmetry. The crystal structure of the high-temperature phase of Cs2[Cu(H2O)6](ZrF6)2 determined at 327 K is built up from Cs+ and [Cu(H2O)6]2+ cations and complex [Zr2F12]4- anions linked through hydrogen bonds [40]. In addition to the previously studied crystal structures of hybrid organic-inorganic fluoride complexes of zirconium, namely [H(gly)]2ZrF6 and [H(ala)]2ZrF6 [2] that contain dimeric

ip t

complex anions [Zr2F12]4-, the structures of a number of new dimeric hybrid fluoridozirconates were determined (Table 1). The structure of [H2dap]2[Zr2F12] [41] is composed of [Zr2F12]4anions and diprotonated [H2dap]2+ cations. The [Zr2F12]4- dimers are surrounded by eight

cr

[H2dap]2+ cations. Each cation is connected, in its turn, to five Zr2F12 units. A three-dimensional

us

branched system of hydrogen bonds is formed between F atoms of Zr2F12 dimers and diprotonated organic cations.

The crystal structures of 18 inorganic salts with protonated cations of 4,4ʹ-bipyrazol (bpz)

an

and tetramethyl-4,4ʹ-bipyrazol (bpzMe4), including that of [H2bpz]2[Zr2F12], were investigated [42]. These contain dimeric complex anions [Zr2F12]4-. In [H2bpz]2[Zr2F12], the 4,4ʹ-

M

bipyrazolium cations and dimeric complex anions [Zr2F12]4- are linked into a three-dimensional structure by N-H···F hydrogen bonds with N···F distances of 2.672(2)-2.975(2) Å. Dimeric complex anions [Zr2F12]4- are also found in the structures of [H4tren](Zr2F12)·H2O, -

ce pt

ed

[H4tren](Zr2F12), and -[H4tren](Zr2F12) as well (Fig. 5) [43].

Fig. 5 here

The [H4tren]4+ cations form hydrogen bonds with fluorine atoms of seven dimers in [H4tren](Zr2F12)·H2O and -[trenH4](Zr2F12) and eight dimers in -[H4tren](Zr2F12). In the

Ac

[H4tren](Zr2F12)·H2O structure, the H2O molecules are linked by strong hydrogen bonds with fluorine atoms from two different dimers (O-H···F = 2.65 and 2.66 Å). The compounds [Co(en)3]2[Zr2F12][SiF6]·4H2O [44] and [Co(en)3]2[Zr2F12][ZrF6(H2O)] [45]

contain, in addition to dimeric complex anions [Zr2F12]4-, discrete anions [SiF6]2- and [ZrF6(H2O)]2-, respectively. The isolated pentagonal-bipyramidal complex anion [ZrF6(H2O)]2with a coordinated H2O molecule was established for the first time. An extensive N-H···F hydrogen bonding network connects the discrete complex cations [Co(en)3]3+ and anions [Zr2F12]4-, [SiF6]2-, [Zr2F12]4-, and [ZrF6(H2O)]2-. Each dimeric complex anion [Zr2F12]4- interacts through H-bonds with six nearby complex cations [Co(en)3]3+. The N···F distances in both structures fall into the ranges 2.766(7)-3.106(7) Å and 2.793(6)-3.121(6) Å, respectively. The H2O molecules also participate in the formation of H-bonds as with F atoms as between each Page 12 of 59

13 other. However, these bonds are rather weak (2.935(7)-3.487(7) Å): just one O-H···F(1) bond length is equal to 2.736(7) Å. Unlike the dimeric anions [Zr2F12]4- discussed above that are formed from two pentagonal bipyramids and linked through a common F-F edge, centrosymmetric dimeric complex anions [Zr2F12]4- in the structure of K2ZrF6·HF [46] are built up from distorted monocapped octahedra and, in the structure of Rb2-xKxZrF6·2HF (x=0.4171) [47], from monocapped trigonal prisms.

ip t

Strong F-H···F hydrogen bonds (2.3865(10), 2.326(2), and 2.402(2) Å) formed with participation of HF molecules to stabilize the structures.

cr

The structure of the zirconium fluoride complex Na5Zr2F13 with the ratio F:Zr = 6.5 was originally determined using the Weissenberg method [80] and later refined by single-crystal X-

us

ray diffraction [48]. The structure is built up from alternating layers of complex [Zr2F13]5- anions, each of which is built from monocapped trigonal ZrF7 prisms linked by a common vertex. The Na+ cations occupy intermediate positions in the lattice, thus forming vertex- and edge-shared

an

units. In the dimeric [Zr2F13]5- anion, the distance from the Zr atom to the bridging F atom is 2.1044(3) Å, while the average Zr-F bond length is 2.050 Å.

M

The crystal structure of Na5Hf2F13 [9] is isostructural to Na5Zr2F13 [48]. The hafnium atom, like the Zr atom in Na5Zr2F13, forms a seven-coordinate slightly distorted square monocapped trigonal prism. Pairs of seven-coordinate hafnium polyhedra are arranged with the capping atoms

ed

facing each other, and they corner share a F atom to form the dimeric anion [Hf2F13]5−. The average Hf-F distance in Na5Hf2F13, and the average Zr-F distance in Na5Zr2F13, are similar

ce pt

(2.054(3) and 2.050 Å, respectively).

The coordination polyhedron of the Hf atom in (NH3OH)3HfF7 [34], which is isotypic to (NH3OH)3ZrF7 [76], has a dodecahedral configuration (CN 8). Two HfF8 polyhedra share a common edge to form a dimeric complex anion [Hf2F14]6-. The anion [Hf2F14]6- and the cations

Ac

(NH3OH)+ are linked by hydrogen bonds. The structure of [H3tren]2[ZrF6][Zr2F12] [49] can be considered as a transition from a dimeric

to monomeric structure (Fig. 6). Three crystallographically independent Zr atoms form polyhedra of different configurations. The Zr(1)F6 polyhedra are isolated and have a distorted octahedral coordination. The Zr(2) atoms form distorted pentagonal bipyramidal coordination polyhedra, whereas the Zr(3) atoms adopt distorted octahedra. The Zr(2)F7 and Zr(3)F6 units share a common vertex giving [Zr2F12]4-. This type of dimeric complex anion, [Zr2F12]4-, was established for the first time. Both independent protonated cations [H3tren]3+ participate in the formation of a system of N-H···F hydrogen bonds with four [Zr2F12] dimers and two [Zr(1)F6] octahedra. The H···F distances range from 1.96(2) up to 2.48(2) Å.

Page 13 of 59

14 Fig. 6 here

2.6. Monomeric structures

Among the monomeric structures of zirconium and hafnium fluoride complexes, octahedral anions [MF6]2- (M = Zr, Hf) (CN 6) are the most common, but those with CN 7 and 8 are also

ip t

known. The compounds Ag2ZrF6·8NH3 and Ag2HfF6·8NH3 [50] were synthesized by reaction between Ag3M2F14 (M = Zr, Hf) [63] and liquid NH3 at -40 oC. The zirconium and hafnium atoms in isotypical compounds Ag2ZrF6·8NH3 and Ag2HfF6·8NH3 are each surrounded by F

cr

atoms to form isolated [ZrF6]2- and [HfF6]2– anions. The Ag atoms are coordinated by NH3

us

molecules and form [Ag(NH3)4(-NH3)Ag(NH3)3]2+ cations. The complex anions [MF6]2- are completely surrounded by NH3 molecules from the cations, forming a branched system of NH···F hydrogen bonds linking octahedral [MF6]2- anions into a complex three-dimensional

an

framework with the complex Ag+ cations located in the voids.

During studies of the systems MF2/KF/MF4 and MF2/NaF/MF4 (M2+ = Ti2+, V2+, M4+ = Zr4+,

M

Hf4+) [11], VZrF6, VHfF6, TiZrF6, and TiHfF6 were obtained. Their structures contain ideally regular octahedral [M4+F6]2- anions with Zr-F distances of 1.996 (6), 1.998 (6) Å in VZrF6 and TiZrF6 and Hf-F distances of 1.970 (6), 1.962 (6) Å in VHfF6 and TiHfF6, respectively.

ed

Regular octahedral [HfF6]2- anions are found in Li2HfF6, [9], which is isostructural to the lowtemperature modification of Li2ZrF6 [71]. Similar to Li2ZrF6, the Li2HfF6 structure consists of

ce pt

hexagonal close packed F ions with Li and Hf atoms occupying octahedral holes in a 2:1 ratio, giving rise to a three-dimensional layered framework of [LiF6] and [HfF6] octahedra. The previously investigated crystal structure of (CH7N4)2ZrF6 [81] is built up from slightly distorted octahedral complex [ZrF6]2- anions and (CH7N4)+ cations linked into a three-

Ac

dimensional framework by hydrogen bonds N-H···F. A more recent single-crystal X-ray study [51] confirmed the original structure (Fig. 7).

Fig. 7 here

A series of papers [52-55] describes the synthesis and determination of the crystal structures for Co(III) dioximate complexes with isolated centrosymmetric octahedral [ZrF6]2- anions (Table 1). The [ZrF6]2- anions in these compounds have the main role in structural organization due to the formation of a branched system of N-H···F and O-H···F hydrogen bonds. Synthesis and X-ray diffraction studies of a new type of fluoride complex of zirconium and hafnium [NMe4]2AF6∙(H2O∙HF) (A = Zr, Hf) has been described [56]. The structures are built up Page 14 of 59

15 of discrete slightly distorted octahedral [ZrF6]2-, [HfF6]2- anions, tetramethylammonium cations, and solvate adducts H2O∙HF. In the H2O∙HF units, the H2O and HF molecules are linked by strong F-H∙∙∙O hydrogen bonds: 2.4327(9) and 2.434(2) Ǻ, respectively (Table 1). These adducts are linked via O-H···F hydrogen bonds to fluorine atoms of two complex anions [AF6]2- with distances of 2.6340(8), 2.6379(7) Å and 2.629(2), 2.6363(19) Å, respectively. The structural units of the compound [NMe4]2AF6∙(H2O∙HF) are linked into a three-dimensional framework

ip t

through a branched system of O-H···F and C-H···F hydrogen bonds and ionic interactions. The synthesis and crystal structure of [NMe4]2ZrF6 were also reported [56]. The compound is built of

cr

virtually ideal ZrF6 octahedra and NMe4 tetrahedra.

The [Zn(2,2ʹ-bpy)2(H2O)2](ZrF6)·3H2O structure contains slightly distorted octahedral

us

complex anions [ZrF6]2-, [Zn(2,2ʹ-bpy)2(H2O)2]2+ complex cations, and uncoordinated H2O molecules [57]. Both the free and coordinated water molecules participate in the formation of OH···F hydrogen bonds (2.652(3)-2.669(3) Å). The coordinated water molecule forms a hydrogen

an

bond with the free molecule as well (O-H···O = 2.678(4) Å) (PLATON, [82]). The compounds [H3tren]2(ZrF7)2·9H2O and [H3tren]6(ZrF7)2(TaOF6)4·3H2O [58] crystallize

M

in the same rhombohedral space group with very similar lattice parameters. In both structures, the x and y atomic coordinates of F, C, and N atoms, as well as those of Zr atoms and disordered (Zr, Ta) atoms, are almost identical. It was concluded that the Zr or (Zr, Ta) coordination

ed

polyhedra in [H3tren]2(ZrF7)2·9H2O and [H3tren]6(ZrF7)2(TaOF6)4·3H2O were similar. In both structures, the Zr atoms and disordered ones (Zr, Ta) are seven-coordinated and form isolated

ce pt

polyhedra with the configuration of a monocapped trigonal prism (Fig. 8).

Fig. 8 here

Ac

In the [H3tren]2(ZrF7)2·9H2O structure, the [H3tren]3+ cations and (ZrF7)3- anions form layers of [H3tren]2(ZrF7)2·H2O, with solvent water molecules sandwiched between the layers. Dehydration of [H3tren]2(ZrF7)2·9H2O occurs in the range from room temperature up to 90 oC with formation of [H3tren]2(ZrF7)2·H2O, which is isostructural to [H3tren]6(ZrF7)2(TaOF6)4·3H2O [58]. The layers in the product remain essentially the same as in the starting fully hydrated compound. The only complex fluoride of zirconium with an protonated organic cation and the ratio F:Zr = 8 reported to date is [H3tren]4(ZrF8)3·4H2O. It has a cubic structure [43]. The Zr atoms in this compound are eight-coordinate and form slightly distorted isolated dodecahedra (Fig. 9). Fig. 9 here Page 15 of 59

16

3. Structures of mixed-ligand fluoride complexes of zirconium and hafnium

This section includes the crystal structures of mixed-ligand fluoride complexes of Zr and Hf, in which the F(L):Zr(Hf) ratio is 4 and higher. The structures mainly contain coordinated H2O molecules in addition to the fluoride ions. The crystal structures of a number of tetrafluoride

ip t

complexes of zirconium and hafnium with neutral O- and N-donor ligands were determined as well (Table 2). As in the case of fluoride complexes of Zr and Hf, the structures of mixed-ligand fluoride complexes are considered along with the increase of the ratio of total ligand number to

us

cr

the central atom (L:Zr(Hf)) for the considered type of the structure.

Table 2 here

an

3.1. Structures of anionic mixed-ligand fluoride complexes of zirconium and hafnium

M

3.1.1. Layered structures

The crystal structures of Rb2Hf3F12O and Rb2Zr3F12O [14] with the ratio L:Zr(Hf) = 4.33 contain an unusual trigonal planar MO3 group. The structures are isotypic, the metal atoms

ed

having CN 8 and forming distorted square antiprisms. Three M-polyhedra are linked into an M3F18O cluster through the common (O, F) edge, in which the O atom is surrounded by three M

ce pt

atoms. The M3F18O cluster is linked to another such unit through three common (F-F) edges, forming M6F30O4, in which the M atoms are located on the vertices of a trigonal prism. In turn, the M6F30O4 groups are linked through common vertices (F) and edges (O, F) into double layers with Rb+ cations located between them. The compound K2Hf3F12O [9] and K2Zr3F12O [95] are

Ac

isostructural to Rb2Hf3F12O and Rb2Zr3F12O [14]. 3.1.2. Chain structures The compound [H(en)][Zr(OH)2F3] can be considered as a pentaate, in which two F atoms

are substituted by OH-groups. It has a chain structure composed of polymer complex anions [(Zr(OH)2F3)-]∞ and monoprotonated ethylenediammonium cations, [H(en)]+ [83]. The structure of the complex anion [(Zr(OH)2F3)-]∞ is built up from pentagonal-bipyramidal polyhedra Zr(OH)4F3, in which both axial positions are occupied by F atoms. The bipyramid equatorial plane contains 4 bridging OH-groups and a terminal F atom. The Zr atoms are linked through alternatively located bridging OH-groups by common edges into zigzag polymer chains [(Zr(OH)2F3)-]∞ (Fig. 10). The structure is similar to that of (CH7N4)ZrF5 [68] containing Page 16 of 59

17 polymer chains [(ZrF5)-]∞ built up from pentagonal-bipyramidal polyhedra. Fig. 10 here

The crystal structure of [H4tren][Zr3F16(H2O)] [49] contains three crystallographically independent zirconium atoms: Zr(1), Zr(2), and Zr(3). Zr(1) and Zr(3) are eight-coordinate and

ip t

form distorted square antiprisms. The Zr(2) atoms are seven-coordinate and their coordination polyhedra are close to a distorted pentagonal bipyramid. The coordination sphere of the Zr(1)

cr

atoms includes seven F atoms and a coordinated H2O molecule, whereas Zr(2) and Zr(3) are coordinated only by F atoms. The coordination polyhedra of Zr(1)F7(H2O), Zr(3)F8, and Zr(2)F7

us

share common F-F edges to form infinite spiral-like [Zr3F16(H2O)4-]∞ chains. Structurally similar polymer chains [(Zr3F17)5-]∞ formed from ZrF8 and ZrF7 coordination polyhedra are found in the

an

crystal structure of LiCs4Zr3F17·HF [96]. 3.1.3. Dimeric structures

M

The compound [NMe4]2[Hf2F10(H2O)2] [84] is isostructural to its zirconium analog [NMe4]2[Zr2F10(H2O)2] [97]. The crystal structure of [NMe4]2[Hf2F10(H2O)2] is built up from [NMe4]+ (Fig. 11).

ed

centrosymmetric dimeric complex anions [Hf2F10(H2O)2]2- and tetramethylammonium cations

ce pt

Fig. 11 here

The Hf atoms in the structure are seven-coordinate and form pentagonal-bipyramidal polyhedra. The hafnium atoms are symmetrically linked into dimeric complex anion

Ac

[Hf2F10(H2O)2]2- by a double bridges having a common equatorial F-F edge. One of the equatorial positions in each polyhedron is occupied by the coordinated H2O molecule. The compounds [NH2Me2]2[Zr2F10(H2O)2]·2H2O and [NH2Me2]2[Hf2F10(H2O)2]·2H2O [2], (18-C-6)(H3O)2[Hf2F10(H2O)2]·4H2O [85], and a number of hydrates of dimeric pentafluorocomplexes of zirconium and hafnium with the monoprotonated cation of azacrownether (HA18C6)+ and the diprotonated cation of diazacrown-ether (H2DA18C6)2+ [86] (Table 2) have structures similar to [NMe4]2[Hf2F10(H2O)2]. The asymmetric unit of [Co(en)3][Zr2F11(H2O)] ([Co(en)3]2[Zr4F22(H2O)2]) [87] contains one Co(III) atom and two unique Zr atoms. The Zr atoms are surrounded either by seven F atoms or seven F atoms and the O atom of the coordinated water molecule to form pentagonalbipyramidal and dodecahedral polyhedra, respectively. Each pentagonal-bipyramidal ZrF7 shares edges (two bridge F atoms) with one dodecahedron ZrF7(H2O) giving dimeric [Zr2F12(H2O)]4Page 17 of 59

18 units, which is linked through a common F-F edge with the identical dimeric unit to form a tetrameric chain complex anion [Zr4F22(H2O)2]6- (Fig. 12) with inversion symmetry. The ZrF7 polyhedra are located at the ends of the tetrameric chain, while the ZrF 7(H2O) polyhedra are located in the middle of the tetramer. This complex anion was found earlier in the crystal structure of diethylenetriaminium(3+) undecafluoridodizirconate dihydrate, [H3(dien)][Zr2F11(H2O)] H2O [98].

ip t

Fig. 12 here

cr

Isolated binuclear [Hf2F10(O2)]4- complex anions linked into a framework by K+ cations and

us

H2O2 molecules comprise the structure of K4Hf2F10(O2)·2H2O2 [88]. In the binuclear complex anion [Hf2F10(O2)]4-, each Hf atom is surrounded by five F atoms and two O atoms of the peroxide anion, forming pentagonal bipyramidal polyhedra that linked on an edge through the

an

peroxide group. The crystal structure of K4Hf2F10(O2)·2H2O2 is very similar to that of K4Hf2F10(O2)·2H2O [99]. In both structures, the complex anion [Hf2F10(O2)]4- has the same

3.1.4. Monomeric structures

M

dimeric structure with similar values of the polyhedron geometrical parameters.

ed

A new type of monomer fluoride pentagonal-bipyramidal complex anion containing five F atoms and two coordinated H2O molecules was established in the crystal structure of

ce pt

(C2H5N4)[HfF5(H2O)2]·H2O [89] (Table 2). The structure contains two crystallographically nonequivalent formula units. It is built up from monomeric complex anions [HfF5(H2O)2]- (Fig. 13), 4-amino-1,2,4-triazolium, (C2H5N4)+ cations and lattice H2O molecules. A branched system of hydrogen bonds of the types O-H···F, O-H···N, O-H···O, and N-H···F as well as electrostatic

Ac

interactions link the structural units [HfF5(H2O)2]-, (C2H5N4)+ , and H2O molecules into a threedimensional structure.

Fig. 13 here

The first hafnium-based oxyfluoride elpasolites K3HfOF5 and (NH4)3HfOF5, displaying a monomeric cubic structure were reported along with the hafnium fluoride compounds Li2HfF6, Na5Hf2F13 and K2Hf3F12O [9]. These structures feature octahedral six-coordinate hafnium atoms having identical Hf-F and Hf-O bond distances 1.953(19) and 1.957(14), respectively. The K+ and NH4+ cations are six- and twelve-coordinate, respectively

Page 18 of 59

19

3.2. Structures of coordination compounds ZrF4 and HfF4 with neutral O- and N-donor ligands

In coordination compounds of ZrF4 and HfF4 with neutral O-donor ligands, the CN of the central atom ranges from 6 to 8, whereas in the compounds with N-donor ligands, only CN = 8 is

ip t

observed. For ZrF4 and HfF4 with O-donor ligands different structural motifs (polymeric chains, dimers and monomers) are realized, while in those with N-donor ligands show only monomeric

cr

compounds.

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3.2.1. Structures of coordination compounds ZrF4 and HfF4 with O-donor ligands 3.2.1.1. Chain structures

an

The monoclinic modification of ZrF4·3H2O (marked as -ZrF4·3H2O) [90] is isostructural to monoclinic HfF4·3H2O [100]. The compound -ZrF4·3H2O was obtained and studied in [101].

M

The F atoms, two of the three H2O molecules and two symmetry related F atoms are included into the coordination sphere of the Zr atom, forming a slightly distorted square antiprism (Table

ed

2). Unlike the triclinic modification of ZrF4·3H2O (denoted as -ZrF4·3H2O) [102], in which the Zr atom polyhedra are linked by common F-F edges into discrete dimeric groups [Zr2F8(H2O)6], in -ZrF4·3H2O the polyhedra are linked through common F-F edges into isolated

ce pt

[(ZrF4(H2O)2)0]∞ chains alternating along the a axis (Fig. 14). The H2O molecules not included into the coordination sphere of the central atom are located between the chains.

Ac

Fig. 14 here

The crystal structure of HfF4·3H2O was originally determined by the Weissenberg method

[100]. The positions of the hydrogen atoms were not determined and the R-value of the structure model was relatively high at 0.130. The single-crystal structure of HfF4·3H2O was recently redetermined using direct methods [90]. The results are in agreement with the earlier structure, with minor changes in bond distances and angles.

3.2.1.2. Dimeric structures A large group of ZrF4 and HfF4 complexes with neutral O-donor ligands (dmso, dmf, OPPh3, OPMe3, and OAsPh3) have been synthesized and structurally studied [35]. The crystal structure of [ZrF4(dmso)2] was studied independently previously [103-105]. The monoclinic Page 19 of 59

20 crystals of [ZrF4(dmso)2] are built up from isolated centrosymmetric dimeric units [(dmso)2F3Zr(-F)2ZrF3(dmso)2]

formed

through

linking

two

pentagonal-bipyramidal

ZrF5(dmso)2 polyhedra through a common F-F edge. The two dmso oxygen atoms occupy transpositions in the equatorial plane. The axial positions in the bipyramid are occupied by fluorine atoms. The crystals of [HfF4(dmso)2] [35] are isomorphic to the monoclinic form of [ZrF4(dmso)2] [103-105] (Table 2).

ip t

During the synthesis of ZrF4 with N-donor ligands in dmso, a small number of crystals having a tetragonal cell were obtained, which belong to the cis-[ZrF4(dmso)2] isomer [35]. The

cr

crystal structure of cis-[ZrF4(dmso)2] contains centrosymmetrical dimeric [(dmso)2F3Zr(F)2ZrF3(dmso)2] units built up from pentagonal-bipyramidal polyhedra ZrF5(dmso)2 linked

us

through common F-F edges. The O atoms of the dmso ligands occupy cis-positions in the polyhedron.

The compound [Zr2F8(dmso)2(H2O)2] [91] was obtained by partial dehydration of

an

[ZrF4(dmso)(H2O)2]·2H2O [103]. Its structure was determined by the non-empirical method from powder diffraction data. It is formed from [Zr2F8(dmso)2(H2O)2] bipolyhedra built up from edge-

M

linked [ZrF5(dmso)(H2O)] bipyramids. These ZrF5O2 bipyramids are the result of condensation of isolated ZrF4O3 pentagonal bipyramids from the initial [ZrF4(dmso)(H2O)2]·2H2O compound.

ed

Similar to [Zr2F8(dmso)2(H2O)2], the structure of [Zr2F8(urMe4)2(H2O)2]·2H2O [92] consists

ce pt

dimeric complexes, built from pentagonal-bipyramidal polyhedra connected by a F-F edge.

3.2.1.3. Monomeric structures

Beside the synthesis of dimeric complexes, a number of discrete octahedral complexes of ZrF4 and HfF4 with dmf, OPPh3, OAsPh3, and OPMe3 were obtained and structurally

Ac

investigated [35]. Unlike the dimeric structure of cis-[ZrF4(dmf)2] [106], the crystal structure of [HfF4(dmf)2] shows discrete monomeric cis-octahedral complexes (Fig. 15). Fig. 15 here

The isomorphic compounds [ZrF4(OEPh3)2]·2CH2Cl2 (E = P, As) [35] (Table 2) contain monomeric centrosymmetric trans-octahedral complexes [ZrF4(OEPh3)2]. In both complexes, the lengths of the Zr-F and Zr-O bonds are very similar, and the O(1)-Zr-O(1a) angles between oxygen atoms of both ligands are equal to 180.00o. The crystal structures of cis[ZrF4(OAsPh3)2]·2CH2Cl2 and cis-[HfF4(OPMe3)2] were determined as well (Table 2) [35].

Page 20 of 59

21

3.2.2. Structures of coordination compounds ZrF4 and HfF4 with N-donor ligands The recently synthesized complex [HfF4(2,2ʹ-bpy)2] was investigated by means of the

19

F

NMR and a single crystal X-ray structural analysis [93]. The coordination number of the Hf atoms is equal to 8, whereas the coordination is a square antiprism. Four F atoms and four N

ip t

atoms of two chelating 2,2ʹ-bpy molecules form the coordination sphere of the Hf atom (Fig. 16). The complexes [HfF4(2,2ʹ-bpy)2] are linked into a three-dimensional structure through C-

cr

H···F hydrogen bonds and van der Waals interactions. The crystals of [ZrF4(2,2ʹ-bpy)2] [35] are

Fig. 16 here

us

isomorphic with the Hf analog. Both compounds have very similar bond lengths and geometries.

an

Upon a prolonged standing of a reaction vessel containing Ag3M2F14 (M = Zr, Hf) [63] in liquid NH3, crystals of [MF4(NH3)4]·NH3 (M - Zr, Hf) were isolated [94] in which the Zr and Hf

M

atoms display a CN of 8. Their coordination polyhedra, just like that of the Hf atom in the structure of [HfF4(2,2ʹ-bpy)2], comprise distorted square antiprisms. In both structures, the vertices of the coordination polyhedra are alternately occupied by four symmetrically equivalent

ed

F atoms and four symmetrically equivalent N atoms, forming discrete [MF4(NH3)4] complexes. In addition to [MF4(NH3)4], the structure of [MF4(NH3)4]·NH3 also contains solvate NH3

ce pt

molecules that are well separated from the M atoms at 4.476(1) and 4.483(3) Å, respectively.

4. Conclusions

Ac

The crystal structures of fluoride and mixed-ligand fluoride complexes of zirconium and hafnium reported since 1998 have enriched the understanding of the stereochemistry of this rather interesting class of inorganic fluorides and revealed a number of new structural motifs. The formation of new complex anions and neutral mixed-ligand fluoride complexes of Zr and Hf has been established: monomeric pentagonal-bipyramidal complex anions [HfF5(H2O)2]-·[89] and [ZrF6(H2O)]2- [45]; a new type of isolated dimeric complex anion [Zr2F12]4- formed from ZrF7 and ZrF6 polyhedra linked through common vertex [49]; a cyclic trimeric complex anion [M3F15]3- built up from octahedral groups linked to each other through bridging F atoms [35]; isolated trimeric complex anions [Zr3F18]6- [36]; monomeric neutral mixed-ligand octahedral complexes of ZrF4 and HfF4 of cis- and trans-configurations with O-donor ligands of dmf, OPPh3, OPMe3, and OAsPh3 [35]; and monomeric eight-coordinated mixed-ligand complexes of Page 21 of 59

22 ZrF4 and HfF4 with N-donor ligands of [MF4(2,2ʹ-bpy)2] and [MF4(NH3)4]·NH3 (M = Zr, Hf) [35, 93, 94]. New motifs were established in crystal structures of a number of polymer fluoride complexes of Zr and Hf: double layers in the structures of M2Hf3F12O and M2Zr3F12O (M = K, Rb) [9,14, 95] containing trigonal-planar groups MO3 unusual for fluoride complexes of Zr and Hf; double chains in the structure of [H2dabco](Zr2F10)·1.5H2O [19]; a polymer chain [(Zr6F35)11-

ip t

]∞ in the structure of LiK10Zr6F35·2H2O [24] built up from two types of trinuclear fragments Zr(1)F7-Zr(2)F7-Zr(3)F7 and Zr(4)F7-Zr(6)F8-Zr(5)F7. In the first one polyhedra are linked through common vertices, while in the second one they are linked through common F-F edges;

cr

and zigzag polymer chains [(Zr(OH)2F3)-]∞ from pentagonal-bipyramidal polyhedra Zr(OH)4F3

us

linked by alternatively located OH-groups [83].

The results of these crystal structures studies show a dependence of the complex anion structure on the F(L):Zr(Hf) ratio and CN of the central atom. Complexes of Zr and Hf showing

an

a framework structure are characterized by large CN of the central atom (8 and 7) and involvement of all or almost all of polyhedron’s fluorine atoms in the formation of bridging

M

bonds with neighboring polyhedra (Table 1). In the layered structures of Zr and Hf fluoride complexes, the F:Zr(Hf) ratio is mainly equal to 5, while the CN of the central atom is equal to 8. The linking of the polyhedra into polymer chains is accomplished by six bridging F atoms,

ed

mostly through three common F-F edges.

In the crystal structures that have a F:Zr(Hf) molar ratio in the range 5 to 5.83 and exhibit a

ce pt

chain structure, the CN of the central atom is 7 and the coordination polyhedron is a pentagonal bipyramid or a monocapped trigonal prism. The chain structural motif is realized through linking through two common F-F edges (Table 1). For the compounds with the anion chain structure, in which the F(L):Zr(Hf) ratio is equal to 6, the CN is 8 and the coordination polyhedron is a square

Ac

antiprism or a dodecahedron. The polyhedra are linked into polymer chains via common F-F edges.

In the structures of dimeric fluoride and mixed-ligand fluoride complexes of Zr and Hf, the

F(L):Zr(Hf) ratio is equal to 6 and CN of the central atom is 7 (Table 1, 2). The coordination polyhedra have the configuration of a pentagonal bipyramid. Two pentagonal bipyramids form dimeric complex anions through a common edge. The CN of the central atom in the structures of monomeric fluoride and mixed-ligand fluoride complexes of Zr and Hf can be 6, 7, or 8, and the observed polyhedra are the octahedron, pentagonal bipyramid, and dodecahedron, respectively (Table 1, 2). In the monomeric mixed-ligand fluoride complexes of ZrF4 and HfF4 with N-donor ligands, the CN of Zr and Hf is 8, and the polyhedra are square antiprisms (Table 2). Page 22 of 59

23

Acknowledgements RLD acknowledges Prof. A. Le Bail for providing reprint of a publication on the crystal structure of a zirconium fluoride complex. KHW is grateful to the Robert A. Welch Foundation (C-0976) for financial support. Sandia National Laboratories is a multi-program laboratory

ip t

managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration

cr

under contract DE-AC04-94AL85000.

us

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Teplukhina, Koord. Khim. 19 (1993) 526. [80] R.M. Herak, S.S. Malčić, Lj.M. Manojlovič, Acta Crystallogr. 18 (1965) 520. [81] B.V. Bukvetskii, A.V. Gerasimenko, R.L. Davidovich, Koord. Khim. 16 (1990) 1479. [82] A.L. Spek, J. Appl. Crystallogr. 36 (2003) 7. [83] D.P. Brennan, P.Y. Zavalij, S.R.J. Oliver, J. Solid State Chem. 179 (2006) 665. [84] A.V. Gerasimenko, R.L. Davidovich, V.V. Tkachev, S.W. Ng, Acta Crystallogr. E 62 (2006) m196. [85] V.O. Gel’mbol’dt, E.V. Ganin, L.V. Koroeva, M.S. Fonar’, Yu.A. Simonov, V.Kh. Kravtsov, Ya. Lipkovski, Zh. Neorg. Khim. 46 (2001) 1833. V.O. Gel’mbol’dt, E.V. Ganin, L.V. Koroeva, M.S. Fonar’, Yu.A. Simonov, V.Kh. Kravtsov, Ya. Lipkovski, Russ. J. Inorg. Chem. 46 (2001) 1666. Page 27 of 59

28 [86] M.S. Fonari, V.Ch. Kravtsov, Yu.A. Simonov, S.S. Basok, E.V. Ganin, V.O. Gelmboldt, K. Suwinska, J. Lipkowski, O.A. Alekseeva, N.G. Furmanova, Polyhedron 27 (2008) 2049. [87] Y. Du, J. Yu, Y. Chen, Y. Yang, Dalton Trans. (2009) 6736. [88] B.V. Bukvetskii, A.V. Gerasimenko, B.N. Chernyshov, N.A. Didenko, N.G. Bakeeva, Zh. Neorg. Khim. 44 (1999) 528.

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[89] R.L. Davidovich, M.A. Pushilin, V.B. Logvinova, A.V. Gerasimenko, Zh. Struk. Khim. 54 (2013) 696.

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R.L. Davidovich, M.A. Pushilin, V.B. Logvinova, A.V. Gerasimenko, J. Struct. Chem. 54 (2013) .

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[90] R.L. Davidovich, M.A. Pushilin, V.B. Logvinova, A.V. Gerasimenko, Zh. Struk. Khim. 54 (2013) 497.

R.L. Davidovich, M.A. Pushilin, V.B. Logvinova, A.V. Gerasimenko, J. Struct. Chem. 54

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(2013) 488.

[91] Y. Gao, A. Le Bail, Powder Diffr. 25 (2010) 329.

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[92] E.G. Il’in, V.V. Kovalev, G.G. Aleksandrov, I. Grenthe, Dokl. Akad. Nauk 401 (2005) 196.

(2004) 639.

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[93] E.G. Il’in, V.V. Kovalev, G.G. Aleksandrov, A.V. Sergeev, Dokl. Akad. Nauk 398

[94] F. Kraus, S.A. Baer, M.B. Fichtl, Eur. J. Inorg. Chem. (2009) 441.

ce pt

[95] M.A. Saada, A. Hemon-Ribaud, V. Maisonneuve, L.S. Smiri, M. Leblanc, Acta Crystallogr. E 59 (2003) i131.

[96] A.V. Gerasimenko, T.F. Antokhina, S.S Sergienko, Koord. Khim. 24 (1998) 822; A.V. Gerasimenko, T.F. Antokhina, S.S Sergienko, Russ. J. Coord. Chem. 24 (1998)

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769.

[97] B.V. Bukvetskii, A.V. Gerasimenko, R.L. Davidovich, M.A. Medkov, Koord. Khim. 11 (1985) 77.

[98] V.V. Tkachev, R.L. Davidovich, L.O. Atovmyan, Koord. Khim. 19 (1993) 292. V.V. Tkachev, R.L. Davidovich, L.O. Atovmyan, Russ. J. Coord. Chem. 19 (1993) 271. [99] B.N. Chernyshov, N.A. Didenko, N.G. Bakeeva, B.V. Bukvetskii, A.V. Gerasimenko, Zh. Neorg. Khim. 36 (1991) 1112. [100] D. Hall, C.E.F. Rickard, T.N. Waters, J. Inorg. Nucl. Chem. 33 (1971) 2395. [101] M.M Godneva, D.L. Motov, V.Y. Kuznetsov, M.P. Rys’kina, Zh. Neorg. Khim. 48 (2003) 329. M.M Godneva, D.L. Motov, V.Y. Kuznetsov, M.P. Rys’kina, Russ. J. Inorg. Chem. 48 Page 28 of 59

29 (2003) 271. [102] F. Gabela, B. Kojić-Prodić, M. Ńljukić, Ņ. Ruņić-Toroń, Acta Crystallogr. B 33 (1977) 3733. [103] Y. Gao, J. Guery, C. Jacoboni, Acta Crystallogr. C 49 (1993) 963.

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[104] N.W. Alcock, W. Errington, S.L. Golby, S.M.C. Patterson, M.G.H. Wallbridge, Acta Crystallogr. C 50 (1994) 226. [105] E.G. Il’in, H.W. Roesky, G.G. Alexandrov, V.V. Kovalev, A.V. Sergeev, V.G. Yagodin, V.S. Sergienko, R.N. Shchelokov, Y.A. Buslaev, Dokl. Akad. Nauk 355 (1997) 349.

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[106] W. Errington, M.A. Ismail, Acta Crystallogr. C 50 (1994) 1540.

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30 Figure Captions: Fig. 1. An ORTEP drawing of a fragment of the polymer layer [(ZrF5)-]∞ in [H2(en)]Zr2F10·H2O (CSD code: QUSNAT)* [15].

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Fig. 2. An ORTEP drawing of a fragment of the polymer chain [(ZrF5)-]∞ in [(Cu(OHMe)2(Lʹ)2](ZrF5)2 (CSD code: XOHRIW) [21] * The Figures were redrawn from the corresponding references using the software package CrystalMaker, version 2.7.4.

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Fig. 3. An ORTEP drawing of the structure of the discrete trimeric cyclic complex anion [Zr3F15]- in [HIDiPP]3[Zr3F15]·4thf·0.55CH2Cl2 (CCDC Deposition Number 890609 ) [35]

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Fig. 4. An ORTEP drawing of the structure of the tetrameric complex anion [Zr4F24]8- in (CH8N4)ZrF6·H2O (CSD code: NUNQES) [37]

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Fig. 5. An ORTEP drawing of the structure of the dimeric complex anion [Zr2F12]4- in [H4tren](Zr2F12)·H2O (CCDC Deposition Number 824421) [43].

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Fig. 6. An ORTEP drawing of the structure of dimeric [Zr2F12]4- (A) and monomeric [ZrF6]2- (B) complex anions in [H3tren]2[ZrF6][Zr2F12] (CSD code: QAJJER) [49].

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Fig. 7. An ORTEP drawing of a fragment of the structure (CH7N4)2ZrF6 (CSD code: KOJVAG01) [51]. Fig. 8. An ORTEP drawing of a fragment of the structure [H3tren]2(ZrF7)2·9H2O (CSD code: DASKOJ) [58].

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Fig. 9. An ORTEP drawing of a fragment of the structure [H3tren]4(ZrF8)3·4H2O (CCDC Deposition Number 824424) [43]. Fig. 10. An ORTEP drawing of a fragment of the polymer chain [(Zr(OH)2F3)-]∞ in [H(en)][Zr(OH)2F3] (CSD code: XOTYEL) [83].

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Fig. 11. An ORTEP drawing of the structure of the dimeric complex anion [Hf2F10(H2O)2)]2- in [NMe4]2[Hf2F10(H2O)2] (CSD code: REBGIP) [84]. Fig. 12. An ORTEP drawing of the structure of the tetrameric complex anion [Zr4F22(H2O)2]6- in [Co(en)3]2[Zr4F22(H2O)2] (CSD code: IGOZEK) [87] Fig. 13. An ORTEP drawing of the structure of the complex anion [HfF5(H2O)2]- in (C2H5N4)[HfF5(H2O)2]·H2O (CCDC Deposition Number 888107) [89].

Fig. 14. An ORTEP drawing of a part of the polymer chain [(ZrF4(H2O)2)0]∞ in the structure of -ZrF4·3H2O [90]. Fig. 15. An ORTEP drawing of the structure of the monomeric octahedral complex [HfF 4(dmf)2] in the structure of cis-[HfF4(dmf)2] (CCDC Deposition Number 890605) [35] Page 30 of 59

31

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Fig. 16. An ORTEP drawing of the structure of the monomeric complex [HfF4(2,2ʹ-bpy)2] in the structure of [HfF4(2,2ʹ-bpy)2] (CSD code: NANCEL) [93].

Page 31 of 59

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Graphical Abstract (for review)

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HIGHLIGHTS 

Structural chemistry of 93 fluoride and 34 mixed-ligand fluoride Zr and Hf complexes are reviewed. The structures show systematic variations with the F(L):Zr(Hf) ratio and CN of the metal ion.



Common coordination polyhedra include octahedron, pentagonal bipyramid and dodecahedron.

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

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Figure(s)

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Figure(s)

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Figure(s)

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Figure(s)

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Figure(s)

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Figure(s)

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Figure(s)

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Figure(s)

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Table(s)

Table 1. Stereochemistry of fluoride complexes of zirconium and hafnium. Polyhedron, composition

Anion motifs, nature of association 1 2 3 Zirconium and hafnium fluoride complexes Frameworks F:Zr(Hf)=5 Ag7Zr6F31 SAPR-8, ZrF2/1F6/2 Framework, (6V) Ag7Hf6F31 SAPR-8, HfF2/1F6/2 Framework, (6V) F:Zr=7 KVZrF7 PBPY-7, ZrF1/1F6/2 Framework, (E+4V) RbCdZrF7 PBPY-7, ZrF0/1F7/2 Framework, (2E+3V) TlCdZrF7 PBPY-7, ZrF0/1F7/2 Framework, (2E+3V) RbCaZrF7 PBPY-7, ZrF0/1F7/2 Framework, (2E+3V) TlCaZrF7 PBPY-7, ZrF0/1F7/2 Framework, (2E+3V) Ag2ZnZr2F14 PBPY-7, ZrF3/1F4/2 Framework

References 4

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Compound

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Layers F:Zr(Hf)=5 DD-8, HfF2/1F6/2 DD-8, ZrF2/1F6/2 DD-8, ZrF2/1F6/2 DD-8, ZrF2/1F6/2 DD-8, ZrF2/1F6/2 DD-8, ZrF2/1F6/2 PBPY-7, ZrF3/1F4/2 DD-8, ZrF2/1F6/2

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RbHfF5 [H2(en)]Zr2F10·H2O [NH3Me]ZrF5·0.5H2O [H(gly)]ZrF5·2H2O [H(ala)]ZrF5 [Hmeam]2(Zr2F10)·H2O [H2dap](Zr2F10)·H2O

K3Ag2Zr4F23

K3Ag2Hf4F23

F:Zr(Hf)=5.75 (2) DD-8, ZrF2/1F6/2 (2) DD-8, HfF2/1F6/2

[10] [10] [11] [12] [12] [12] [12] [13]

Layer, (E+4V) Layer, (3E) Layer, (3E) Layer, (3E) Layer, (3E) Layer, (3E) Layer, (2E) (3E)

[14] [15] [2,16] [2,16] [2,16] [17] [17]

Layer, (2E+2V)

[18]

Layer, (2E+2V)

[18]

Double chains

[19]

Chains F:Zr(Hf)=5 [H2dabco](Zr2F10)·1.5H2O

Page 50 of 59

[20] [2] [2] [2] [21]

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(2E) (3E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E)

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(CH7N4)ZrF5 [NHMe3]ZrF5 [NEt4]ZrF5·0.5H2O [H(ida)]ZrF5·H2O [(Cu(OHMe)2(Lʹ)2](ZrF5)2

PBPY-7, ZrF3/1F4/2 DD-8, ZrF2/1F6/2 PBPY-7, ZrF3/1F4/2 PBPY-7, ZrF3/1F4/2 PBPY-7, ZrF3/1F4/2 PBPY-7, ZrF3/1F4/2 PBPY-7, ZrF3/1F4/2

Page 51 of 59

Table 1 (Continued)

NaTiHf2F11 NaVHf2F11

2 F:Zr(Hf)=5.5 PBPY-7, HfF4/1F3/2 PBPY-7, HfF4/1F3/2

3

4

Chain, (E+V) Chain, (E+V)

[11] [11]

F:Zr(Hf)=5.66

(1) TPRS-7, ZrF4/1F3/2 (1) DD-8, ZrF4/1F4/2 (1) PBPY-7, ZrF4/1F3/2

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[22]

Chain (E+V) (2E) (E+V)

[22]

Chain (E+V) (2E) (E+V)

[22]

Chain (E+V) (2E) (E+V)

[22]

Chain (2E) (E+V)

[23]

Chain (2V) (V+E) (2E)

[24]

(1) TPRS-7, ZrF4/1F3/2 (1) DD-8, ZrF4/1F4/2 (1) PBPY-7, ZrF4/1F3/2

(1) TPRS-7, HfF4/1F3/2 (1) DD-8, HfF4/1F4/2 (1) PBPY-7, HfF4/1F3/2

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NaCs4Hf3F17·2HF

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Na(NH4)4Zr3F17·2HF

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LiRb4Zr3F17·2HF

(1) TPRS-7, ZrF4/1F3/2 (1) DD-8, ZrF4/1F4/2 (1) PBPY-7, ZrF4/1F3/2

Chain (E+V) (2E) (E+V)

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Li(NH4)4Zr3F17·2HF

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1

Li(NH4)6Zr4F23

F:Zr=5.75

(2) DD-8, ZrF4/1F4/2 (2) TPRS-7, ZrF4/1F3/2 F:Zr=5.83

LiK10Zr6F35·2H2O

(3) OCF-7, ZrF5/1F2/2 (2) OCF-7, ZrF4/1F3/2 (1) DD-8, ZrF4/1F4/2

Page 52 of 59

[25,26] [27] [27] [27] [27] [27] [28] [28] [28]

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Chain, (2E) Chain, (2E) Chain, (2E) Layer, (2E) Chain, (V+TF) Chain, (V+TF) Chain, (V+TF) Chain, (V+TF) Chain, (V+TF)

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Li2ZrF6 K2ZrF6 K1.756(NH4)0.244ZrF6 K1.218(NH4)0.782ZrF6 K0.480(NH4)1.520ZrF6 K0.381(NH4)1.619ZrF6 Rb0.322(NH4)1.678ZrF6 Rb0.416(NH4)1.584ZrF6 Rb0.447(NH4)1.553ZrF6

F:Zr(Hf)=6 SAPR-8, ZrF4/1F4/2 DD-8, ZrF4/1F4/2 SAPR-8, ZrF4/1F4/2 DD-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2

Page 53 of 59

[HIDiPP]3[Hf3F15]·4thf·0.55CH2Cl2

OC-6, HfF4/1F2/2

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4 [29] [30] [31] [32] [32] [33] [33] [15] [34]

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[HIDiPP]3[Zr3F15]·4thf·0.55CH2Cl2

Oligomers F:Zr=5 OC-6, ZrF4/1F2/2

3 Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E) Chain, (2E)

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2 DD-8, ZrF4/1F4/2 DD-8, ZrF4/1F4/2 TPRS-8, ZrF4/1F4/2 DD-8, ZrF4/1F4/2 DD-8, ZrF4/1F4/2 SAPR-8, ZrF4/1F4/2 SAPR-8, HfF4/1F4/2 DD-8, ZrF4/1F4/2 DD-8, HfF4/1F4/2

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Table 1 (Continued) 1 MgZrF6·5H2O Li2Mg(ZrF6)2·4H2O SnZrF6 (NH4)SnZrF7 KSnZrF7 KCuZrF7 KCuHfF7 [H2(pipz)]ZrF6·H2O (NH3OH)2HfF6

Trimer (2V) Trimer (2V)

[35]

Trimer (E) (2E)

[36]

Trimer (E) (2E)

[36]

Tetramer (2E) (2E)

[37]

Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E) Dimer, (E)

[38] [39] [40] [2] [2] [41] [42] [43] [43]

[35]

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F:Zr=6

[Co(NH3)5(H2O)]2[Zr3F18]· 6H2O

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ZrF5/1F2/2 SAPR-8, ZrF4/1F4/2

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[Co(NH3)6]2[Zr3F18]·6H2O

(2) PBPY-7,

(2) PBPY-7, ZrF5/1F2/2

SAPR-8, ZrF4/1F4/2

(CH8N4)ZrF6·H2O

K2[Ni(H2O)6][ZrF6]2 Cs2[Zn(H2O)6](ZrF6)2 Cs2[Cu(H2O)6](ZrF6)2 [H(gly)]2ZrF6 [H(ala)]2ZrF6

[H2dap]2[Zr2F12] [H2bpz]2[Zr2F12] [H4tren](Zr2F12)·H2O -[H4tren](Zr2F12)

(2) SAPR-8, ZrF4/1F4/2 (2) TPRS-8, ZrF4/1F4/2

Dimers F:Zr=6 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2

Page 54 of 59

[Co(en)3]2[Zr2F12][SiF6]·4H2O [Co(en)3]2[Zr2F12][ZrF6(H2O)]

Dimer, (E) Dimer, (E) Dimer, (E) Monomer

[43] [44] [45]

Dimer, (E) Dimer, (E)

[46] [47]

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K2ZrF6·HF Rb2-xKxZrF6·2HF (x=0.4171)

PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF5/1F2/2 PBPY-7, ZrF6/1H2O1/1 OCF-7, ZrF5/1F2/2 TPRS-7, ZrF5/1F2/2

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-[H4tren](Zr2F12)

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Table 1 (Continued)

Na5Zr2F13 Na5Hf2F13

F:Zr(Hf)=7 DD-8, HfF4/1F4/2 (1), OC-6, ZrF6/1 (1) PBPY-7, ZrF6/1F1/2 (1), OC-6, ZrF5/1F1/2

4

Dimer, (V) Dimer, (V)

[48] [9]

Dimer, (E) Monomer Dimer, (V) Dimer, (V)

[34] [49]

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(NH3OH)3HfF7 [H3tren]2[ZrF6][Zr2F12]

3

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2 F:Zr(Hf)=6.5 TPRS-7, ZrF6/1F1/2 TPRS-7, HfF6/1F1/2

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1

Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer Monomer

[50] [50] [11] [11] [11] [11] [9] [51] [52] [53] [53] [54] [54] [55] [56] [56] [56] [57]

[H3tren]2(ZrF7)2·9H2O [H3tren]6(ZrF7)2(TaOF6)4·3H2O

F:Zr=7 TPRS-7, ZrF7/1 TPRS-7, ZrF7/1

Monomer Monomer

[58] [58]

F:Zr=8 DD-8, ZrF8/1

Monomer

[43]

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Ag2ZrF6·8NH3 Ag2HfF6·8NH3 VZrF6 VHfF6 TiZrF6 TiHfF6 Li2HfF6 (CH7N4)2ZrF6 [Co(HD)2(Sam)2]2(ZrF6)·5H2O [Co(HD)2(Anil)2]2(ZrF6)·2H2O [Co(HNiox)2(Anil)2]2(ZrF6)·3H2O [Co(HD)2(tu)2]2(ZrF6)·H2O [Co(HNiox)2(tu)2]2(ZrF6)·3H2O [Co(HD)2(Seu)(Se-Seu)]2(ZrF6)·3H2O [NMe4]2ZrF6∙(H2O∙HF) [NMe4]2HfF6∙(H2O∙HF) [NMe4]2ZrF6 [Zn(2,2ʹ-bpy)2(H2O)2](ZrF6)·3H2O

Monomers F:Zr(Hf)=6 OC-6, ZrF6/1 OC-6, HfF6/1 OC-6, ZrF6/1 OC-6, HfF6/1 OC-6, ZrF6/1 OC-6, HfF6/1 OC-6, HfF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1 OC-6, HfF6/1 OC-6, ZrF6/1 OC-6, ZrF6/1

[H3tren]4(ZrF8)3·4H2O

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Table(s)

Table 2. Stereochemistry of mixed-ligand fluoride complexes of zirconium and hafnium. References Polyhedron, Nature of composition association 1 2 3 4 Zirconium and hafnium mixed-ligand fluoride complexes

[14]

Chain, (2E)

[83]

Chain

[49]

an

K2Hf3F12O

cr

Rb2Zr3F12O

Double layers, (E+4V) Double layers, (E+4V) Double layers, (E+4V)

us

L:Zr(Hf)=4.33 SAPR-8, HfF1/1F6/2O1/3 SAPR-8, ZrF1/1F6/2O1/3 SAPR-8, HfF1/1F6/2O1/3

Rb2Hf3F12O

ip t

Compound

Chains L:Zr=5 PBPY-7, ZrF3/1(OH)4/2

M

[H(en)][Zr(OH)2F3]

[14] [9]

d

L:Zr=5.66

Zr(1) SAPR-8, ZrF3/1F4/2O1/1

Ac ce p

te

[H4tren][Zr3F16(H2O)]

[NMe4]2[Hf2F10(H2O)2]

[NH2Me2]2[Zr2F10(H2O)2]·2H2O

[NH2Me2]2[Hf2F10(H2O)2]·2H2O (18-C-6)(H3O)2[Hf2F10(H2O)2]·4H2O

Zr(3), SAPR-8, ZrF4/1F4/2 Zr(2) PBPY-7, ZrF3/1F4/2 Dimers L:Zr(Hf)=6 PBPY-7, HfF4/1F2/2O1/1 PBPY-7, ZrF4/1F2/2O1/1 PBPY-7, HfF4/1F2/2O1/1 PBPY-7, HfF4/1F2/2O1/1

(2E) (2E) (2E)

Dimer, (E)

[84]

Dimer, (E)

[2]

Dimer, (E)

[2]

Dimer, (E)

[85]

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Table 2 (Continued)

[H2(DA18C6)] [Hf2F10(H2O)2]·2H2O

[Co(en)3][Zr2F11(H2O)] ([Co(en)3]2[Zr4F22(H2O)2])

4 [86]

Dimer, (E)

[86]

Dimer, (E)

[86]

Dimer, (E)

[86]

Tetramer (2E) (E) Dimer, (E)

[87]

Monomer

[89]

Monomer Monomer

[9] [9]

us

DD-8, ZrF5/1F2/2O1/1 PBPY-7, ZrF5/1F2/2 PBPY-7, HfF5/1O2/2 Monomer L:Hf=7 PBPY-7, HfF5/1(H2O)2/1

an

K4Hf2F10(O2)·2H2O2

M

(C2H5N4)[HfF5(H2O)2]·H2O

L:Hf=6 OC-6, HfF5/1O1/1 OC-6, HfF5/1O1/1

d

K3HfOF5 (NH4)3HfOF5

3 Dimer (E)

ip t

[H2(DA18C6)][Zr2F10(H2O)2]·2H2O

2 PBPY-7, ZrF4/1F2/2O1/1 PBPY-7, HfF4/1F2/2O1/1 PBPY-7, ZrF4/1F2/2O1/1 PBPY-7, HfF4/1F2/2O1/1

cr

1 [H(A18C6)(H2O)](H3O) [Zr2F10(H2O)2]·H2O [H(A18C6)(H2O)](H3O) [Hf2F10(H2O)2]·H2O

[88]

Ac ce p

te

Coordination compounds of ZrF4 and HfF4 with neutral O- and N-donor ligands Chains L:Zr(Hf)=6 SAPR-8, Chain, (2E) [90] -[ZrF4(H2O)2]·H2O [HfF4(H2O)2]·H2O

trans-[Hf2F8(dmso)4] cis-[Zr2F8(dmso)4]

[Zr2F8(dmso)2(H2O)2] [Zr2F8(urMe4)2(H2O)2]·2H2O

ZrF2/1F4/2(H2O)2/1

SAPR-8,

Chain, (2E)

[90]

Dimer, (E)

[35]

Dimer, (E)

[35]

Dimer, (E)

[91]

Dimer, (E)

[92]

HfF2/1F4/2(H2O)2/1

Dimers L:Zr(Hf)=6 PBPY-7, HfF3/1F2/2O2/1 PBPY-7, ZrF3/1F2/2O2/1 PBPY-7, ZrF3/1F2/2O2/1 PBPY-7, ZrF3/1F2/2O2/1 Monomers L:Zr(Hf)=6

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OC-6, HfF4/1O2/1 OC-6, ZrF4/1O2/1 OC-6, ZrF4/1O2/1 OC-6, ZrF4/1O2/1 OC-6, HfF4/1O2/1

Monomer Monomer Monomer Monomer Monomer

[HfF4(2,2ʹ-bpy)2] [ZrF4(2,2ʹ-bpy)2] [ZrF4(NH3)4]·NH3 [HfF4(NH3)4]·NH3

L:Zr(Hf)=8 SAPR-8, HfF4/1N4/1 SAPR-8, ZrF4/1N4/1 SAPR-8, ZrF4/1N4/1 SAPR-8, HfF4/1N4/1

Monomer Monomer Monomer Monomer

[35] [35] [35] [35] [35] [93] [35] [94] [94]

Ac ce p

te

d

M

an

us

cr

ip t

cis-[HfF4(dmf)2] trans-[ZrF4(OPPh3)2]·2CH2Cl2 trans-[ZrF4(OAsPh3)2]·2CH2Cl2 cis-[ZrF4(OAsPh3)2]·2CH2Cl2 cis-[HfF4(OPMe3)2]

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