Preparative and structural investigation of crown ether adducts of potassium fluorenides

Accepted Manuscript Preparative and structural investigation of crown ether adducts of potassium fluorenides Ahmad Zaeni, Ulrich Behrens, Phil Liebing, Falk Olbrich, Frank T. Edelmann PII:

S0022-328X(16)30576-9

DOI:

10.1016/j.jorganchem.2016.12.017

Reference:

JOM 19740

To appear in:

Journal of Organometallic Chemistry

Received Date: 8 June 2016 Revised Date:

9 December 2016

Accepted Date: 16 December 2016

Please cite this article as: A. Zaeni, U. Behrens, P. Liebing, F. Olbrich, F.T. Edelmann, Preparative and structural investigation of crown ether adducts of potassium fluorenides, Journal of Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2016.12.017. 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.

ACCEPTED MANUSCRIPT

Graphical Abstract

Preparative and Structural Investigation of Crown Ether Adducts of

Ahmad Zaeni a, Ulrich Behrens

b.*

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Potassium Fluorenides , Phil Liebing c, Falk Olbrich

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Edelmann c,*

b,*

, Frank T.

ACCEPTED MANUSCRIPT

Full Paper submitted to Journal of Organometallic Chemistry Preparative and Structural Investigation of Crown Ether Adducts of Potassium Fluorenides b.*

, Phil Liebing c, Falk Olbrich

b,*

, Frank T. Edelmann

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Ahmad Zaeni a, Ulrich Behrens c,*

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Dedicated to Professor Erwin Weiss on the Occasion of his 90th birthday

Chemistry Department, Haluoleo University, Kendari, Indonesia

b

Institut für Anorganische und Angewandte Chemie der Universität Hamburg, Martin-

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a

Luther-King-Platz 6, D-20146 Hamburg, Germany c

Chemisches Institut, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2,

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D-39106 Magdeburg, Germany

____________________ * Corresponding authors. Fax: +49-40-42838-2893; E-mail addresses: [email protected] (U. Behrens); [email protected] (F. Olbrich) Fax: +49-391-67-12933; E-mail address: [email protected] (F.T. Edelmann).

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ACCEPTED MANUSCRIPT ABSTRACT ___________________________________________________________________________ Three crystalline adducts of potassium fluorenides with 18-crown-6, KC13H9(18-crown6)·0.5py (1, py = pyridine), KC13H9(18-crown-6)·2THF (2), and K(9-Me3SiC13H8)(18-crown6) (3), have been synthesized and structurally characterized through single-crystal X-ray

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diffraction. The complexes form orange to orange-brown, highly air- and moisture-sensitive crystals. In 1, the potassium ion is coordinated to the carbon atoms C4, C10 and C11 of the fluorenide anion in an η3-allyl-like fashion. In contrast, the solid-state structure of 2 consists of [K(18-crown-6)(THF)2]+ cations and free fluorenide anions. In the ring-substituted

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potassium fluorenide derivative 3, only C4 and C11 of the fluorenyl moiety are bonded to the potassium ion. Agostic methyl interactions between the SiMe3 substituents and the [K(18crown-6)]+ cations lead to the formation of a polymeric chain structure.

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___________________________________________________________________________

Keywords: Fluorenyl ligands; Fluorenide anion; Potassium; 18-Crown-6; Crystal Structure

1. Introduction

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Fluorenyl ligands (= dibenzocyclopentadienyl, C13H9–, cf. Scheme 1) play a significant role in the design of highly selective early transition metal and lanthanide metallocene

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catalysts for olefin polymerization [1,2].

Scheme 1. The fluorenide anion.

A general synthetic protocol leading to such metallocene catalysts involves treatment

of suitable metal halide precursors with alkali metal fluorenides [3]. Previous X-ray diffraction studies had already revealed that the structural chemistry of these alkali metal fluorenides is surprisingly diverse. This is due to the fact that both the five- and six-membered rings can be coordinated to the alkali metal ions and that hapticities can range from η2 to η6. Besides the unsolvated alkali metal fluorenides LiC13H9 [4] and [K(9-Ph3SiC13H8)]n [5], various adducts with ethers [6], chelating amines [7] and 18-crown-6 [8] have been prepared

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ACCEPTED MANUSCRIPT and structurally investigated by X-ray diffraction. In some cases it has been shown that slight changes in the crystallization conditions can lead to the formation of different structural modifications and coordination modes. For example, two structural modifications have been reported for the adducts of potassium fluorenide with N,N,N',N'-tetramethylethylenediamine (= tmeda) [7b,c]. Crystals of the polymeric form {[K(µ,η1,η1-tmeda)2][µ-C13H9]}∞ were

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obtained by evaporation of a benzene/tmeda (1:1) solution of [K(tmeda)2][C13H9] [7b]. In this structure, the tmeda molecules do not act as chelating ligands but bridge two potassium ions to give a polymeric network. Crystallization of [K(tmeda)2][C13H9] from the more polar solvent mixture tmeda/THF/Et2O (1:1:1) afforded

a monomeric modification of

[K(tmeda)2][C13H9] in which the two tmeda molecules act as chelating ligands and the

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potassium ion is η5-coordinated to the central five-membered ring of the fluorenide anion [7c]. Previously reported adducts of potassium fluorenide with 18-crown-6 include

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KC13H9(18-crown-6)·0.5toluene, [{KC13H9(18-crown-6)}{KC13H9(18-crown-6)(THF)}] and the binuclear complex (µ-DME)[KC13H9(18-crown-6)]2 [8]. Typical for all three complexes is an η6-interaction of the potassium ion with one six-membered ring of the fluorenyl ligand. The observation of this unusual η6-coordination has been explained by repulsive interactions between the fluorenyl benzo rings and the 18-crown-6 ligand if η5-coordination to the central

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cyclopentadienyl ring occurred [8]. We report here the synthesis and crystal structure determination of three new adducts of potassium fluorenides with 18-crown-6, namely KC13H9(18-crown-6)·0.5py (1), KC13H9(18-crown-6)·2THF (2), and K(9-Me3SiC13H8)(18crown-6) (3). In all three compounds, the fluorenyl coordination mode differs from that of the

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previously reported complexes.

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2. Results and discussion

2.1. Syntheses and characterization The title compounds KC13H9(18-crown-6)·0.5py (1) and KC13H9(18-crown-6)·2THF

(2) were easily prepared by recrystallizing the known potassium fluorenide derivative KC13H9(18-crown-6)·0.5toluene [8] from either pyridine or THF after layering the saturated solutions with n-pentane. Alternatively, compound 1 could be prepared directly by deprotonation of fluorene with potassium hydride in a toluene/pyridine mixture (3:1 vol/vol) followed by addition of 18-crown-6. In a similar manner, the new 9-trimethylsilyl-substituted potassium fluorenide derivative K(9-Me3SiC13H8)(18-crown-6) (3) was made by treatment of 9-(trimethylsilyl)fluorene subsequently with potassium hydride and 18-crown-6 in a toluene/THF mixture. Scheme 2 summarizes the synthetic results.

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ACCEPTED MANUSCRIPT All new compounds form orange, air- and moisture-sensitive crystals which dissolve freely in donor solvents like THF, DME, and pyridine, but are only slightly soluble in toluene and insoluble in n-pentane. The products were characterized via the usual set of spectroscopic and analytical methods, although most of these data were rather uninformative and did not clearly reveal the coordination modes of the fluorenyl ligands to potassium. For example, the

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IR spectrum of KC13H9(18-crown-6)·0.5py (1) shows a very strong band at ν 1109 cm-1 which can be assigned to the C-O stretching vibrations of the crown ether ligand. Other characteristic bands are found at ν 3036 cm-1 (aromatic C-H stretching), 2885 cm-1 (aliphatic C-H stretching), 1469 cm-1 (C=C), and 1570 cm-1 (C-N of pyridine). In the case of 2, the

H

R

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18-crown-6 and two THF ligands per formula unit.

1. KH toluene/THF 2. 18-crown-6

R = H, SiMe3 1. KH toluene/pyridine 2. 18-crown-6 - H2

1. KH toluene/THF - H 2 2. 18-crown-6

O

O

O K

O

O

O

O

O x 0.5 py

K

O

O

O

O

O

O

O

2 (R=H)

CH 3 Si Me 2

O K

O

O O n

3 (R=SiMe 3)

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1 (R=H)

- H2

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O

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integration pattern in the 1H NMR spectrum is in good agreement with the presence of one

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Scheme 2. Synthesis of the potassium fluorenide complexes 1-3.

2.2. X-Ray diffraction studies All three title compounds were structurally characterized through single-crystal X-ray

diffraction. Orange-brown single-crystals of 1 were obtained directly from the reaction mixture as described in the Experimental Section. The compound crystallizes in the monoclinic space group P21/n. Crystallographic data of all three compounds are listed in Table 1, and the molecular structure of 1 along with selected bond lengths is depicted in Figure 1. The central potassium ion is coordinated to the 18-crown-6 ligand in a slightly unsymmetrical fashion with K-O distances ranging from 282.3(2) to 293.6(2) pm. Due to the additional aryl-π coordination of the fluorenide anion, the K atom is slightly displaced from the O6 plane. The [C13H9]– anion is arranged parallel to the [K(18-crown-6)]+ cation where

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ACCEPTED MANUSCRIPT one of the aromatic C6 rings is situated above the apex of the KO6 pyramid in a somewhat irregular fashion. This K-fluorenide contact can be described as η3-C4,C10,C11, with the K-C distances in a range from 314.5(7) to 329.7(6) pm. The remaining free coordination site at the K atom opposite to the fluorenide anion is occupied by a very weak interaction with a pyridine molecule. This is situated on an inversion center between two symmetry-equivalent

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[K(18-crown-6]+ cations and therefore disordered over two orientations. As a result, the pyridine molecule is either coordinated to potassium via the N atom or the para-C atom,

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where the coordinative distance is 359.0 pm (cf. Figure 2).

Fig. 1. Molecular structure of KC13H9(18-crown-6)·0.5py (1) in the crystalline state. Ellipsoids drawn at the 30% probability level, H atoms and the disordered pyridine molecule omitted for clarity. The fluorenide anion is disordered over two positions. Selected bond

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lengths [pm]: K-O1 284.2(2), K-O2 290.1(2), K-O3 282.3(2), K-O4 293.6(2), K-O5 290.4(2),

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K-O6 283.6(2), K-C4 325.5(9), K-C10 329.7(6), K-C11 314.5(7).

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ACCEPTED MANUSCRIPT Fig. 2. Representation of the coordinative saturation of two symmetry-equivalent [K(18crown-6)]+ cations (orange) by two [C13H9]– anions and one disordered pyridine molecule (blue) in compound 1. The K-N/K-C(para) distance is 359.0 pm.

The bonding situation changes completely when the precursor KC13H9(18-crown-

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6)·0.5toluene [8] is recrystallized from THF under formation of KC13H9(18-crown-6)(THF)2 (2). As illustrated in Figure 3, the strong donor THF adds to the K(18-crown-6) unit to form a formally octa-coordinated [K(18-crown-6)(THF)2]+ cation in which the potassium ion is coordinatively saturated. The coordination sphere around potassium can be described as

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hexagonal-bipyramidal with K-O bond lengths to the crown ether in the range of 275.1(1) 286.3(1) pm. With an average of 270.6(2) pm the K-O distances to the THF ligands in transpositions are significantly shorter. Due to the coordinative saturation of potassium in the

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[K(18-crown-6)(THF)2]+ cation, the salt-like structure of 2 contains free fluorenide anions without any significant K-C interactions. A similar solid-state structure comprising uncoordinated fluorenide anion has been previously reported for the barium fluorenide

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complex [BaC13H9(18-crown-6)(pyridine)]+[C13H9]-·pyridine [9].

Fig. 3. Molecular structure of KC13H9(18-crown-6)(THF)2 (2) in the crystalline state. Ellipsoids drawn at the 30% probability level, H atoms omitted for clarity. The fluorenide anion is disordered over two positions. Selected bond lengths [pm]: K-O1 285.6(1), K-O2 284.3(1), K-O3 275.1(1), K-O4 286.3(1), K-O5 282.6(1), K-O6 275.7(1), K-O7 270.8(1), KO8 270.4(2), C1-C2 138.2(5), C1-C10 142.8(4), C2-C3 140.4(5), C3-C4 138.6(5), C4-C11 138.7(4), C5-C6 139.4(4), C5-C12 139.2(4), C6-C7 140.7(5), C7-C8 136.8(5), C8-C13 143.1(4), C9-C10 140.5(4), C9-C13 140.1(4), C10-C11 144.3(3), C11-C12 144.2(4), C12C13 144.5(3).

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ACCEPTED MANUSCRIPT Compound K(9-Me3SiC13H8)(18-crown-6) (3) was prepared in order to study the influence of the bulky SiMe3 substituent in 9-position of the fluorenyl ring on the coordination of potassium. X-Ray-quality single-crystals of 3 were grown by cooling of a saturated solution in THF/toluene (1:1) to 5 °C. The compound crystallizes in the orthorhombic space group Pca21. Crystallographic data for 3 are listed in Table 1. Figure 4

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shows the molecular structure along with selected bond lengths. At the first glance, the crystal structure analysis of 3 revealed no major difference in the potassium-fluorenyl interactions as compared to compound 1. With bond lengths of 326.8(3) and 317.2(3) pm, respectively, only C4 and C11 of the fluorenyl ligand are coordinated to potassium, although this η2-interaction

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is not very different from the allyl-like η3-C4,C10,C11 coordination in 1. The K-O distances found in 3 are well within the typical range reported earlier for related potassium fluorenide derivatives [5,7,8]. This finding is in agreement with a theoretical investigation by Janiak,

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which suggested that the enery surfaces for metal cations above a delocalized anionic ring such as fluorenide can be quite flat. A comparison of the effective electrostatic potentials on the van der Waals surface revealed that there is no obvious difference between the

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unsubstituted fluorenide anion and 9-tert-butylfluorenide [7c].

Fig. 4. Molecular structure of K(9-Me3SiC13H8)(18-crown-6) (3) in the crystalline state. Ellipsoids drawn at the 30% probability level, H atoms omitted for clarity. Selected bond lengths [pm]: K-O1 295.0(2), K-O2 279.8(3), K-O3 289.3(3), K-O4 284.8(3), K-O5 291.6(3), K-O6 279.9(3), K-C4 326.8(3), K-C11 317.2(3), K-H152 294.8, C1-C2 138.5(6), C1-C10 141.6(5), C2-C3 139.3(7), C3-C4 137.9(6), C4-C11 139.3(4), C5-C6 138.1(5), C5-C12 141.1(5), C6-C7 138.8(6), C7-C8 137.8(5), C8-C13 140.8(5), C9-C10 142.7(5), C9-C13

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ACCEPTED MANUSCRIPT 143.9(5), C10-C11 144.6(5), C11-C12 142.6(5), C12-C13 144.3(4). Symmetry operator to generate equivalent atoms: ‘ 0.5 –x, y, –0.5+z.

However, an important structural difference between 1 and 3 was found upon a closer examination of the crystal structure of 3. As illustrated in Figure 5, the packing diagram of 3

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clearly shows an agostic methyl interaction between the potassion ions and methyl groups of adjacent SiMe3 substituents due to the absence of additional donor ligands such as in 1 and 2. This results in the formation of a supramolecular polymeric zig-zag structure in the solid state. Similar agostic methyl interactions have previously been reported e.g. for the tris(trimethylsilyl)silanides MSi(SiMe3)3 (M = Na, K, Rb, Cs) [10] and alkali metal arene

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complexes comprising [K(ar)2]+ and [Rb(toluene)3]+ cations (ar = benzene, toluene, o-xylene,

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p-xylene) combined with [M{N(SiMe3)2}3]- anions (M = Mg, Zn) [11].

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Fig. 5. Representation of the interconnection of the [K(18-crown-6)]+ cations (orange) by the [(9-Me3SiC13H8)]– anions (blue) in compound 3. The polymeric chain structure extends along

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the crystallographic c axis.

In summarizing the results reported here, we succeeded in the straightforward

preparation and structural characterization of three crystalline 18-crown-6 adducts of potassium fluorenides, namely KC13H9(18-crown-6)·0.5py (1), KC13H9(18-crown-6)·2THF (2), and (9-Me3SiC13H8)(18-crown-6) (3). The X-ray diffraction study showed that the crystal structures of these organopotassium complexes are significantly influenced by both the presence of additional donor solvents (THF, pyridine) as well as substituents on the fluorenide ring system.

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ACCEPTED MANUSCRIPT 3. Experimental section 3.1. General procedures All experiments were performed using glovebox (<1 ppm O2, <1 ppm H2O) and standard Schlenk line techniques under an inert atmosphere of dry argon. THF and toluene were distilled from sodium/benzophenone under nitrogen atmosphere prior to use, while pyridine

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was dried over CaH2. All glassware was oven-dried at 120 ºC for at least 24 h, assembled while hot, and cooled under vacuum prior to use. The starting materials KC13H9(18-crown6)·0.5toluene [8] and (9-trimethylsilyl)fluorene [12] were prepared according to the literature methods. Fluorene and 18-crown-6 were obtained from commercial sources and used as

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received after drying under vacuum. A commercially available suspension of potassium hydride in mineral oil was separated by filtration and the KH residue was washed oil-free with n-pentane, dried under vacuum and transferred into a dry-box. 1H NMR (400 MHz) and

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NMR (100.6 MHz) were recorded on a Bruker DPX 400 spectrometer at 25 ºC. Chemical shifts were referenced to TMS. Microanalyses of the compounds were performed using a Leco CHNS 932 apparatus.

3.2. Synthesis of KC13H9(18-crown-6)·0.5py (1)

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To a solid mixture of fluorene (5.0 g, 30.1 mmol) and potassium hydride (1.2 g, 29.9 mmol) were added subsequently 60 ml of toluene and 20 ml of pyridine. Gas evolution (H2) started immediately, while the reaction mixture turned orange. The suspension was stirred at r.t. until the gas evolution had ceased (ca. 2 h). A solution of 18-crown-6 (7.92 g, 30.0 mmol) in n-

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pentane (25 ml) was added and the reaction mixture was heated to reflux for 6 h. The resulting orange-brown solution was quickly filtered while hot. Cooling of the filtrate to 5 °C for 2 d afforded 8.8 g (58%) of 1 as orange-brown, air- and moisture-sensitive crystals. M.p.

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132–133 °C. Soluble in THF and pyridine, slightly soluble in toluene, and virtually insoluble in aliphatic hydrocarbons. Anal. calcd. for C27.5H35.5KN0.5O6 (508.18): C 65.00, H 7.04, N 1.38; found: C 64.55, H 6.80, N 1.60%. IR (Nujol): ν 3046 (w), 2885 (s), 2821 (m), 1977 (vw), 1884 (vw), 1773 (vw), 1655 (vw), 1570 (m), 1469 (s), 1438 (m), 1349 (s), 1321 (vs), 1221 (s), 1109 (vs), 982 (m), 963 (s), 836 (m), 747 (s), 720 (s), 572 (vw), 528 (vw), 493 (vw), 427 (w) cm-1. 1H-NMR (600.1 MHz, pyridine-d5, 25 °C): δ 8.63 (d, 2H, CH-C13H9), 8.06 (d, 2H, CH-C13H9), 7.42 (t, 2H, CH-C13H9), 7.04 (t, 2H, CH-C13H9), 6.93 (s, 1H, CH-C13H9), 3.24 (s, 24H, OCH2 18-c-6) ppm.

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C-NMR (150.9 MHz, pyridine-d5, 25 °C): δ 137.9 (C-

C13H9), 123.8 (C-C13H9), 119.8, 119.7, 117.1, 108.7, 84.1 (CH-C13H9), 70.1 (OCH2, 18-c-6) ppm.

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ACCEPTED MANUSCRIPT 3.3. Synthesis of KC13H9(18-crown-6)·2THF (2) 1.0 g (1.63 mmol) KC13H9(18-crown-6)·0.5toluene was dissolved in 25 ml of THF and the resulting orange-red solution was concentrated in vacuum until crystals began to form. Crystallization was completed by cooling the solution to 5 °C for 2 d to give orange crystals

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of 2 (ca. 80% isolated yield) which were suitable for X-ray diffraction. Anal. calcd. for C33H49KO8 (612.84): C 64.68, H 8.06; found: C 63.98, H 7.88%. IR (Nujol): ν 3448 (w br), 3064 (w), 2886 (s), 1977 (vw), 1655 (vw), 1599 (vw), 1570 (m), 1469 (s), 1439 (m), 1350 (s), 1321 (vs), 1284 (w), 1249 (m), 1221 (s), 1111 (vs), 983 (m), 964 (s), 837 (m), 747 (s), 720

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(s), 572 (vw), 530 (vw), 493 (vw), 467 (vw), 427 (vw) cm-1. 1H-NMR (400.1 MHz, THF-d8, 25 °C): δ 7.91 (d, 2H, CH-C13H9), 7.30 (d, 2H, CH-C13H9), 6.79 (t, 2H, CH-C13H9), 6.41 (t, 2H, CH-C13H9), 6.01 (s, 1H, CH-C13H9), 3.29 (m, 8H, THF), 3.22 (s, 24H, OCH2 18-c-6), 13

C-NMR (100.6 MHz, THF-d8, 25 °C): δ 137.6 (C-C13H9), 122.9

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1,38 (m, 8H, THF), ppm.

(C-C13H9), 119.5, 119.4, 116.9, 108.4, 83.5 (CH-C13H9), 86.0 (THF), 70.7 (CH2-18-c-6), 26.2 (THF) ppm.

3.3. Synthesis of K(9-Me3SiC13H8)(18-crown-6) (3)

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Toluene (50 ml) and THF (10 ml) were added to a mixture of (9-trimethylsilyl)fluorene (3.0 g, 12.6 mmol) and potassium hydride (0.5 g, 12.6 mmol). Hydrogen evolution started immediately and the mixture turned orange. Stirring at r.t. was continued until the gas evolution had ceased. 18-Crown-6 (3.33 g, 12.6 mmol) was added as a solid, the resulting

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mixture was stirred at reflux temperature for 6 h and filtered while hot. Cooling to 5 °C for 3 d afforded 4.9 g (72%) of 3 as orange, air- and moisture-sensitive crystals. M.p. 165–167 °C. Anal. calcd. for C28H41KO6Si (540.81): C 62.19, H 7.64; found: C 61.80, H 7.54%. IR (KBr):

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ν 3165 (vw), 3055 (m), 2886 (vs), 2826 (m), 1975 (vw), 1600 (w), 1568 (m), 1470 (m), 1450 (s), 1434 (vs), 1351 (vs), 1324 (s), 1307 (s), 1297 (s), 1284 (m), 1251 (s), 1237 (s), 1217 (s), 1108 (vs, ), 988 (m), 964 (vs), 836 (vs), 755 (vs), 718 (vs), 677 (w), 621 (w), 528 (vw), 516 (vw), 434 (w), 426 (w) cm-1. 1H NMR: δ 8.44 (d, 1H, H-4), 8.35 (d, 1H, H-5), 8.14 (d, 1H, H1), 7.90 (d, 1H, H-8), 7.35 (m, 2H, H-2,7), 7.00 (m, 2H, H-3,6), 2.71 (s, 24H, OCH2 18-c-6), 0.76 (s, 9H, Si(CH3)3) ppm. 13C NMR: δ 144.2 (C-10), 138.1 (C-11), 127.0 (C-11), 125.8 (C2,3,6,7), 118.9 (C-4), 116.8 (C-5), 108.7 (C-4,5), 83.6 (C-9), 71.1 (OCH2 18-c-6), 2.9 (Si(CH3)3) ppm.

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ACCEPTED MANUSCRIPT 5

4

3

11

6

12

2

7

10

13

1

8

9

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SiMe3 3.5. X-ray Single Crystal Structure Analysis.

The datasets for the compounds 1 - 3 were collected on a SIEMENS axs SMART CCD

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diffractometer with Mo-Kα radiation, graphite monochromator, and ω-scans. Absorption correction was applied by the multi-scan method (program SADABS [13]). All structures were solved with direct methodes (SHELXS-97) [14] and refined with full-matrix least-

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squares on Fo2, using the program SHELXL-2013 [15]. The non-hydrogen atoms were refined with anisotropic temperature factors. Hydrogen atoms were fixed geometrically and refined using a riding model with isotropic temperature factors. For special refinement procedures see Supporting Information.

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Table 1. Crystal data and structure refinement for KC13H9(18-crown-6)·0.5py (1), KC13H9(18-crown-6)(THF)2 (2), and K(9-Me3SiC13H8)(18-crown-6) (3). __________________________________________________________________________________________ compound

1

2

3

C27.5H35.5KN0.5O6

C33H49KO8

C28H41KO6Si

508.18

612.84

540.80

173

173

173

71.073

71.073

71.073

crystal size/mm

0.6 x 0.4 x 0.3

0.7 x 0.5 x 0.3

0.5 x 0.5 x 0.2

crystal system

monoclinic

monoclinic

orthorhombic

space group

P21/n

P21/c

Pca21

a/pm

948.09(2)

1301.57(4)

1948.94(5)

1540.40(4)

1815.44(5)

958.30(2)

1835.57(3)

1559.27(4)

15.7872(3)

90.9621(9)

114.523(1)

-

2680.36(10)

3352.08(16)

2948.53(11)

4

4

4

1.259

1.214

1.218

absorption coefficient µ/mm

0.238

0.205

0.258

2θmax/°

54

54

54

empirical formula formula weight/g mol temperature/K

b/pm

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wavelength/pm

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–1

c/pm β/o 6

3

volume/ 10 pm Z

–3

density (calcd.)/g cm

-1

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ACCEPTED MANUSCRIPT –13 ≤ h ≤ 16,

–22 ≤ h ≤ 24,

–13 ≤ k ≤ 19,

–20 ≤ k ≤ 23,

–9 ≤ k ≤ 12,

–16 ≤ l ≤ 23

–19 ≤ l ≤ 19

–20 ≤ l ≤ 19

reflections collected

16242

20115

17466

independent reflections

5832

7297

6392

independent refl. with I>2σ(I)

3870

5711

5334

completeness of dataset

99.7%

99.7%

99.9%

parameters

386

396

R1 (all data, I>2σ(I))

0.0831, 0.0489

0.0620, 0.0452

wR2 (all data, I>2σ(I))

0.1453, 0.1222

0.1154, 0.1051

goodness of fit (F )

1.001

1.027

Flack-Parameter

-

-

0.27 and –0.23

0.34 and –0.31

2

largest diff. peak and hole 6

3

(max/min, e/10 pm )

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–12 ≤ h ≤ 11,

329

0.0545, 0.0398

0.0949, 0.0868 1.001

–0.01(2)

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Index ranges

0.18 and –0.17

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__________________________________________________________________________________________

Acknowledgements

This work was financially supported by the Otto-von-Guericke-Universität Magdeburg. A. Z. thanks the DAAD (Deutscher Akademischer Austauschdienst) for a Ph.D. scholarship. F. O.

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wishes to thank the Government of Sachsen-Anhalt for a habilitation fellowship.

Appendix A. Supplementary material

CCDC 247476 (1), CCDC 178658 (2), and CCDC 232075 (3) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the

[1]

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References

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Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

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(c) E. Kirillov, N. Marquet, M. Bader, A. Razavi, V. Belia, F. Hampel, T. Roisnel, J.A. Gladysz, J.-F. Carpentier, Organometallics 30 (2011); (d) R. Tanaka, C. Yanase, Z. Cai, Y. Nakayama, T. Shiono, J. Organomet. Chem. 804 (2016) 95. [2]

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ACCEPTED MANUSCRIPT (c) G.W. Coates, Chem. Rev. 100 (2000) 1223; (d) L. Resconi, L. Cavallo, A. Falt, F. Piemontesi, Chem. Rev. 100 (2000) 1253: (e) J.A. Gladysz, Chem. Rev. 100 (2000) 1167; (f) A. Razavi, U. Thewalt, Coord. Chem. Rev. 250 (2006) 155; (g) E. Kirillov, A.K. Dash, A.-S. Rodrigues, J.-F- Carpentier, Compt. Rend. Chim. 9

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(c) S. Neander, J. Körnich, F. Olbrich, J. Organomet. Chem. 656 (2002) 89. (a) S. Corbelin, J. Kopf, E. Weiß, Chem. Ber. 124 (1991) 2417;

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(b) R. Zerger, W. Rhine, G. D. Stucky, J. Am. Chem. Soc. 96 (1974) 5441; (c) C. Janiak, Chem. Ber. 126 (1993) 1603. (a) S. Neander, F.E. Tio, R. Buschmann, U. Behrens, F. Olbrich, J. Organomet. Chem.

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Sheldrick, G. M. SADABS: Program for area detector absorption correction, Univ. Göttingen, 1996.

14

ACCEPTED MANUSCRIPT [14]

Sheldrick, G. M. SHELXS-97: Program for the Solution of Crystal Structures, Univ. Göttingen, 1997. Sheldrick, G. M. SHELXL-2013: Program for the Refinement of Crystal Structures,

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Univ. Göttingen, 2013.

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[15]

ACCEPTED MANUSCRIPT

Research Highlights Preparative and Structural Investigation of Crown Ether Adducts of

Ahmad Zaeni a, Ulrich Behrens

b.*

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Potassium Fluorenides , Phil Liebing c, Falk Olbrich

Edelmann c,*

b,*

, Frank T.

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Three crystalline adducts of potassium fluorenides with 18-crown-6 have been synthesized.

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Three different potassium-fluorenide coordination modes have been found.
Compound KC13H9(18-crown-6)·2THF (2) contains a free fluorenide anion.
Compound

K(9-Me3SiC13H8)(18-crown-6)

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interactions.

(3)

comprises

agostic

methyl