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S donor ligands
Polyhedron 26 (2007) 2777–2785 www.elsevier.com/locate/poly
Synthesis and structures of cadmium(II) complexes of a series of multinucleating N/S donor ligands Tanya K. Ronson a, Harry Adams a, Lindsay P. Harding b, Ross W. Harrington c, William Clegg c,d, Michael D. Ward a,* b
a Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK Department of Chemistry and Biological Sciences, University of Huddersfield, Huddersfield, HD1 3DH, UK c School of Natural Sciences (Chemistry), Newcastle University, Newcastle upon Tyne, NE1 7RU, UK d CCLRC Daresbury Laboratory, Warrington WA4 4AD, UK
Received 2 January 2007; accepted 16 January 2007 Available online 21 January 2007
Abstract The coordination chemistry of a series of bis-bidentate ligands with cadmium(II) ions has been investigated. The ligands, containing two N,S-donor chelating (pyrazolyl/thioether) fragments, have afforded complexes of a variety of structural types (dinuclear M2L2 ‘mesocate’ complexes, a one-dimensional chain coordination polymer and a simple mononuclear complex) according to whether the bisbidentate ligands act as bridges spanning two metal ions, or a tetradentate chelate to a single metal ion. The p-phenylene and m-biphenyl spaced ligands L1 and L3 form dinuclear M2L2 complexes where the ligands are arranged in a ‘side-by-side’ fashion. In contrast the mphenylene spaced ligand L2 forms a one-dimensional coordination polymer where the ligands adopt a highly folded conformation. The 1,8-naphthalene spaced ligand L4 adopts a tetradendate chelating mode and affords a simple mononuclear complex. 2007 Elsevier Ltd. All rights reserved. Keywords: Cadmium; Coordination chemistry; Crystal structure; Mesocate; Coordination polymer
1. Introduction The self-assembly of elaborate metallosupramolecular assemblies from relatively simple bridging ligands and labile metal ions continues to be an intensely popular area of study, partly because of the insight that these systems offer into control of self-assembly processes, and partly because the resulting assemblies can have a range of useful properties in materials and host-guest chemistry [1]. With regard to the ligands, a minimum condition is that the binding sites must be arranged so that they bridge two or more metal ions, otherwise simple mononuclear complexes may result. If a ligand is flexible, the competition between bridging and chelating coordination modes is an important *
Corresponding author. Tel.: +44 0114 2229484; fax: +44 0114 2229346. E-mail address: m.d.ward@sheffield.ac.uk (M.D. Ward). 0277-5387/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2007.01.012
factor in determining the course of a self-assembly reaction [2]. As part of our continuing studies into the coordination chemistry of flexible ligands containing bidentate chelating groups, we have recently reported the synthesis of a series of new ligands with potentially N,S-chelating arms derived from 3-[2-(methylsulfanyl)phenyl]pyrazole linked to central aromatic spacers by methylene units [3]. The reaction of these ligands with Ag(I) and Cu(I) ions resulted in a series of complexes with 1:1 metal:ligand stochiometry, in which each four-coordinate metal centre is bound by two coordinating arms to give one of three general structural types depending on the structure of the ligand and the nature of the spacer unit separating the two N,S-donor termini. These structural types are (i) dinuclear M2L2 complexes – either helicates, in which the ligands are twisted around one another, or mesocates, in which the ligands adopt a ‘side-by-side’ arrangement; (ii) infinite one-dimensional
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Fig. 1. Molecular structure of L3. Symmetry operation to generate equivalent atoms: (x, y, z + 1).
Scheme 1.
coordination chains [ML]n which contain an alternating sequence M-(l-L)-M-(l-L). . . along the chain, which may also have a chiral helicate structure; (iii) mononuclear complexes ML in which the ligand is flexible enough to coordinate both N,S-donor units to the same metal centre in a tetradentate chelating mode [3]. In this paper we describe the synthesis and structural characterisation of complexes of the potentially bis-bidentate ligands L1–L4 (see Scheme 1) with Cd(II). This metal ion commonly adopts a six-coordinate environment, so we may see either complexes with a M2L3 stoichiometry (or some higher multiple), or the involvement of additional ligands in the coordination sphere to complete the octahedral coordination environment. We note that bridging ligands based on two or more N,S-donor chelating units have recently been studied by several groups because of their propensity to form coordination networks and chains when coordinated to ‘soft’ metal ions [4]. 2. Results and discussion The ligands L1–L4 were prepared according to the previously described method, by reaction of 3-[2-(methylsulfanyl)phenyl]pyrazole with an appropriate bromomethylated aromatic compound (the spacer unit) in the presence of hydroxide ion under phase transfer conditions [3]. The crys-
tal structures of L1, L2 and L4 were reported previously [3]. The crystal structure of L3 is shown in Fig. 1. The individual bond distances and angles within the molecule are unremarkable. The molecule lies across a centre of symmetry, such that the two halves are crystallographically equivalent. The (methylsulfanyl)phenyl/pyrazole units adopt a cisoid configuration with the methyl group pointing away from the lone pairs of the pyrazole nitrogen atoms resulting in an intramolecular N S interaction. This is consistent with the known tendency of divalent S (and Se) atoms to interact with nucleophilic atoms [in this case the pyrazolyl N(2) nitrogen atom] giving short non-bonded contacts [5]. The non˚ is similar to that bonded N(2) S(1) distance of 2.878(2) A observed for L1 [3] and the N(2)–S(1)–C(17) angle of 167.1(1) shows a small deviation from linearity. The reaction of tetradentate ligands L1–L4 with a metal ion that commonly displays six-fold coordination would be expected, in the absence of any coordinating anions or solvent molecules, to afford a complex with a 2:3 metal/ligand ratio. The reaction of the p-phenylene spaced ligand L1 with Cd(ClO4)2 Æ H2O in nitromethane gave a colourless solution; diisopropyl ether diffusion into this solution afforded crystals which analysed with a 1:1 metal/ligand ratio, independently of the starting M:L ratio used in the synthesis (2:3 or 1:1). The ES mass spectrum showed peaks at m/z 1489.0, 695.0 and 430.4 corresponding to the dinuclear species [Cd2(L1)2(ClO4)4-x]x+ (x = 1, 2, 3) showing sequential loss of ClO4 anions. An m/z value of 695.0 may also correspond to the mononuclear species [CdL1(ClO4)]+, but the other two peaks are unambiguous. There are also peaks for fragmentation products at m/z 1177.2 and 1006.8 corresponding to [Cd(L1)2(ClO4)]+ and [Cd2(L1)(ClO4)3]+, respectively. The X-ray crystal structure shows that the crystalline material is the dinuclear complex [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 (Fig. 2, Table 1). The complex is achiral with both bridging ligands spanning both metal centres in a ‘side-by-side’ arrangement commonly called a ‘mesocate’ [6]. This discrete dinuclear complex is in contrast to the polymeric coordination chains obtained from reaction of Cu(I) and Ag(I) with the same ligand [3]. The asymmetric unit contains one complete [Cd2(L1)2(ClO4)2(H2O)2]2+ cation [containing Cd(1) and Cd(2)], and another half-cation [containing Cd(3)] from which the second similar but crystallographically independent cation is generated by a two-
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
Fig. 2. Structure of the metal complex unit of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 Æ 4MeNO2. Only one of the two similar independent molecules is shown.
Table 1 ˚ ) and angles () for [Cd2(L1)2(ClO4)(H2O)](ClO4) Selected bond lengths (A Cd(1)–O(30) Cd(1)–N(1) Cd(1)–O(1) Cd(1)–N(101) Cd(1)–S(101) Cd(1)–S(1) Cd(2)–O(31) Cd(2)–N(104) Cd(2)–N(4) Cd(2)–O(5) Cd(2)–S(2) Cd(2)–S(102) Cd(3)–O(32) Cd(3)–O(9) Cd(3)–N(202) Cd(3)–N(204) Cd(3)–S(202) Cd(3)–S(201) O(32)–Cd(3)–O(9) O(32)–Cd(3)–N(202) O(9)–Cd(3)–N(202) O(32)–Cd(3)–N(204) O(9)–Cd(3)–N(204) N(202)–Cd(3)– N(204) O(32)–Cd(3)–S(202) O(9)–Cd(3)–S(202) N(202)–Cd(3)–S(202) N(204)–Cd(3)–S(202) O(32)–Cd(3)–S(201) O(9)–Cd(3)–S(201) N(202)–Cd(3)–S(201) N(204)–Cd(3)–S(201) S(202)–Cd(3)–S(201)
2.308(3) 2.321(4) 2.349(3) 2.355(4) 2.6642(12) 2.6803(12) 2.285(4) 2.321(4) 2.340(4) 2.362(4) 2.6723(14) 2.6933(14) 2.296(4) 2.328(4) 2.329(4) 2.358(4) 2.6872(13) 2.6979(13) 83.64(16) 91.86(15) 89.86(14) 168.61(15) 95.68(15) 99.51(14) 94.78(11) 92.47(10) 173.17(10) 73.87(10) 90.57(13) 169.39(11) 81.42(10) 91.73(10) 96.88(4)
O(30)–Cd(1)–N(1) O(30)–Cd(1)–O(1) N(1)–Cd(1)–O(1) O(30)–Cd(1)–N(101) N(1)–Cd(1)–N(101) O(1)–Cd(1)–N(101) O(30)–Cd(1)–S(101) N(1)–Cd(1)–S(101) O(1)–Cd(1)–S(101) N(101)–Cd(1)–S(101) O(30)–Cd(1)–S(1) N(1)–Cd(1)–S(1) O(1)–Cd(1)–S(1) N(101)–Cd(1)–S(1) S(101)–Cd(1)–S(1) O(31)–Cd(2)–N(104) O(31)–Cd(2)–N(4) N(104)–Cd(2)–N(4) O(31)–Cd(2)–O(5) N(104)–Cd(2)–O(5) N(4)–Cd(2)–O(5) O(31)–Cd(2)–S(2) N(104)–Cd(2)–S(2) N(4)–Cd(2)–S(2) O(5)–Cd(2)–S(2)
92.18(13) 78.93(13) 92.37(13) 170.96(13) 95.44(13) 95.87(13) 98.02(9) 169.66(10) 91.25(9) 74.55(10) 91.83(9) 82.30(10) 169.18(9) 94.00(10) 95.63(4) 92.46(15) 169.88(15) 95.74(14) 78.99(15) 93.13(14) 94.61(15) 97.65(11) 169.44(11) 74.55(10) 91.81(10)
O(31)–Cd(2)–S(102) N(104)–Cd(2)–S(102) N(4)–Cd(2)–S(102) O(5)–Cd(2)–S(102) S(2)–Cd(2)–S(102)
91.53(11) 81.79(11) 95.50(10) 169.09(11) 94.83(4)
fold rotation. The six-coordinate Cd(II) ions are coordinated by one N,S-chelating arm from each ligand, with a water molecule and a ClO4 anion completing the distorted octahedral coordination. The Cd Cd separations within ˚ [between Cd(1) the dinuclear complex cations of 10.8 A ˚ and Cd(2)] and 10.4 A [between Cd(3) and its symmetry equivalent] are longer than those observed in the polymeric ˚ ) and Ag(I) (7.6 A ˚ ). The complexes of L1 with Cu(I) (9.8 A
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˚ ) bonds are longer than the Cd–N Cd–S (average 2.68 A ˚ ) and ˚ (average 2.34 A), Cd–Operchlorate (average 2.30 A ˚ Cd–Owater bonds (average 2.35 A). The bidentate (methylsulfanyl)phenyl/pyrazole units show large deviations from planarity with torsion angles between the rings in the range 32–53. The central phenylene spacers of the ligands are inclined parallel to each other [angle of approx. 1 between the rings for the molecule with Cd(1) and Cd(2) and exactly parallel by symmetry for the molecule with Cd(3)] and show a p–p stacking interaction. The distance ˚ for the molecule between these stacked rings is 3.5–3.6 A ˚ containing Cd(1) and Cd(2) and 3.2 A for the molecule containing Cd(3). The 1H NMR spectrum of the redissolved crystals of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 shows a two-fold-symmetric environment for L1 in solution. The pyrazole H5 signal is shifted downfield by ca. 0.3 ppm compared to the free ligand but there is little shift in the other signals. The reaction of the m-phenylene spaced ligand L2 with Cd(ClO4)2 Æ H2O in acetonitrile resulted in a colourless solution. Diethylether diffusion into the reaction mixture gave colourless crystals whose elemental analysis indicated a 1:1 metal/ligand ratio. The FAB mass spectrum showed peaks at m/z 596 for {CdL2}+ and 695 {CdL2(ClO4)}+. The X-ray crystal structure shows that the crystalline material is the infinite one-dimensional coordination polymer {[CdL2(CH3CN)2](ClO4)2}1 (Figs. 3 and 4, Table 2). Each Cd(II) ion is coordinated by an N,S-chelating arm from each of two separate ligands. Two cis-coordinated acetontrile molecules make up the distorted octahedral coordination. The Cd–S and Cd–N bond lengths are similar to those of [Cd2(L1)2(ClO4)(H2O)](ClO4). The Cd Cd separation between metals linked by the same bridging ligand ˚ , slightly longer than in the copper complex is 7.33 A ˚ ) [3]. The ligands are folded such {[CuL2](BF4)}1 (6.17 A that the pyrazole rings are almost perpendicular to the central phenyl spacer (angles of 94 and 96 between the mean planes of the rings). This folding brings the Cd(II) ions closer together than in the complex with L1 [the average Cd Cd separation in [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 is
Fig. 3. Structure of the metal complex unit of {[CdL2(CH3CN)2](ClO4)2}1 showing the coordination geometry around the Cd(II) centres.
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Fig. 4. Structure of the one-dimensional polymeric chain of {[CdL2(CH3CN)2](ClO4)2}1, with alternate ligands shaded differently for clarity. Only the N atoms of the coordinated MeCN ligands are shown.
˚ ] in which the ligand adopted a more extended con10.6 A formation. The twist angles between the rings within each bidentate (methylsulfanyl)phenyl/pyrazole unit are ca. 34 and 28. There is an angle of 24 between the planes of the pyrazole ring containging N(3) and a (methylsulfanyl)phenyl from the next ligand, for which the inter-ring ˚ , possibly indicative separation covers the range 3.2–4.3 A of a weak p–p stacking interaction. The 1H NMR spectrum of {[CdL2(CH3CN)2](ClO4)2}1 shows a two-fold-symmetric environment for L2 in solution. The fact that the crystals dissolve in acetonitrile is indicative of the coordination polymer breaking up to form solvated {CdL2}2+ units. The reaction of the m-biphenyl spaced ligand L3 with one equivalent of Cd(ClO4)2 Æ H2O in dry acetonitrile under an N2 atmosphere followed by evaporation gave the crude complex as an oil. Recrystallisation by diethylether vapour diffusion into an acetonitrile/nitromethane (1:1) solution gave a crystalline material which was found to be the discrete dinuclear complex [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 (Fig. 5, Table 3), in contrast to the coordination polymers obtained from the reaction of the same ligand with Cu(I)
Table 2 ˚ ) and angles () for {[CdL2(CH3CN)2](ClO4)2}1 Selected bond lengths (A Cd(1)–N(4) Cd(1)–N(2) Cd(1)–N(5) Cd(1)–N(6) Cd(1)–S(2) Cd(1)–S(1) N(4)–Cd(1)–N(2) N(4)–Cd(1)–N(5) N(2)–Cd(1)–N(5) N(4)–Cd(1)–N(6) N(5)–Cd(1)–S(2) N(6)–Cd(1)–S(2) N(4)–Cd(1)–S(1) N(2)–Cd(1)–S(1) N(2)–Cd(1)–N(6) N(5)–Cd(1)–N(6) N(4)–Cd(1)–S(2) N(2)–Cd(1)–S(2) N(5)–Cd(1)–S(1) N(6)–Cd(1)–S(1) S(2)–Cd(1)–S(1)
2.300(13) 2.376(11) 2.389(11) 2.389(14) 2.636(4) 2.699(4) 96.8(4) 100.7(4) 97.5(4) 166.5(4) 85.3(3) 91.7(3) 96.0(2) 70.0(3) 95.7(4) 82.7(4) 75.6(3) 172.3(3) 160.3(3) 83.4(3) 109.15(11)
Fig. 5. Structure of the [Cd2(L3)2(MeCN)2(H2O)2](ClO4).
metal
complex
unit
of
and Ag(I) [3]. The complex lies astride a centre of symmetry such that the asymmetric unit contains one Cd(II) ion and one complete ligand; clearly therefore it is achiral and not a helicate. Both ligands bridge both metal centres ˚ , almost identical to that with a Cd Cd distance of 10.8 A
Table 3 ˚) Selected bond lengths (A [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 Cd(1)–N(5) Cd(1)–O(1) Cd(1)–N(4A) Cd(1)–N(1) Cd(1)–S(1) Cd(1)–S(2A) N(5)–Cd(1)–O(1) N(5)–Cd(1)–N(4A) O(1)–Cd(1)–N(4A) N(5)–Cd(1)–N(1) O(1)–Cd(1)–N(1) N(4A)–Cd(1)–N(1) N(5)–Cd(1)–S(1) O(1)–Cd(1)–S(1) N(4A)–Cd(1)–S(1) N(1)–Cd(1)–S(1) N(5)–Cd(1)–S(2A) O(1)–Cd(1)–S(2A) N(4A)–Cd(1)–S(2A) N(1)–Cd(1)–S(2A) S(1)–Cd(1)–S(2A)
and
angles
()
for
2.297(5) 2.307(3) 2.314(4) 2.347(4) 2.6263(15) 2.7678(15) 82.06(15) 102.06(17) 99.39(13) 95.43(15) 168.43(13) 92.18(13) 86.87(14) 92.34(10) 166.08(10) 76.21(10) 162.55(13) 84.16(10) 69.71(10) 100.15(10) 104.37(4)
Symmetry transformations used to generate equivalent atoms: (x + 1, y + 1, z + 1).
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
in [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 despite the longer spacer in L3. The Cd(II) ions are in a distorted octahedral geometry with one acetonitrile and one water molecule completing the coordination. The acetonitrile molecules are attached at an angle with the Cd–N–C angles being 142.8(5). The bond lengths to Cd(II) are typical of complexes in this series. The twist angles within the biphenyl spacers are 41.8 and the twist angles within each bidentate (methylsulfanyl)phenyl/pyrazole units are 34.2 and 28.8. There is a p–p stacking interaction between the pyrazole ring containing N(1) and the (methylsulfanyl)phenyl ring of the other ligand (angle of 20.6 between the mean planes ˚ between the rings). of the two rings, distance of 3.2–4.1 A The biphenyl spacers are not involved in any p–p stacking interactions. The electrospray mass spectrum of the crystals shows peaks at m/z 1641.1, 771.1 and 480.7 corresponding to the dinuclear species [Cd2(L3)2(ClO4)4-x]x+ (x = 1, 2, 3) with sequential loss of perchlorate anions. The m/z value of 771.1 may also correspond to the mononuclear species {Cd(L3)ClO4}+ but the other peaks are unambiguous. There are also peaks for Cd2L3 and Cd(L3)2 fragments. The 1H NMR spectrum of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 is broad, indicative of a dynamic process in solution. The reaction of L4 with one equivalent of Cd(ClO4)2 Æ H2O in dry acetonitrile under an N2 atmosphere resulted in a colourless solution. Diethylether diffusion into the reaction mixture gave colourless crystals whose elemental analysis was consistent with the formulation [CdL4(H2O)2](ClO4)4. The electrospray mass spectrum showed peaks at m/z 744 [{CdL4(ClO4)}+] and 343 [{CdL4(MeCN)}2+], consistent with formation of a mononuclear complex. The X-ray crystal structure confirms that the crystalline material [CdL4(MeCN)2](ClO4)2 is a mononuclear complex (Fig. 6, Table 4) in contrast to the dinuclear structures obtained with L1 and L3 and the polymeric structure obtained with L2. The complex has two-fold rotation symmetry such that the asymmetric unit contains half of a
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Table 4 ˚ ) and angles () for [Cd2(L1)2(ClO4)(H2O)](ClO4) Selected bond lengths (A Cd(1)–N(3) Cd(1)–N(2) Cd(1)–S(1) N(3)–Cd(1)–N(3A) N(3)–Cd(1)–N(2) N(3A)–Cd(1)–N(2) N(3)–Cd(1)–N(2A) N(3A)–Cd(1)–N(2A) N(2)–Cd(1)–N(2A) N(3)–Cd(1)–S(1A) N(3A)–Cd(1)–S(1A) N(2)–Cd(1)–S(1A) N(2A)–Cd(1)–S(1A) N(3)–Cd(1)–S(1) N(3A)–Cd(1)–S(1) N(2)–Cd(1)–S(1) N(2A)–Cd(1)–S(1) S(1A)–Cd(1)–S(1)
2.329(4) 2.344(4) 2.7013(14) 175.1(2) 87.49(14) 95.60(14) 95.60(14) 87.49(14) 101.8(2) 85.64(11) 91.29(11) 173.12(9) 78.38(11) 91.29(11) 85.64(11) 78.38(11) 173.12(9) 102.30(7)
Symmetry transformations used to generate equivalent atoms: (y, x, z).
Cd(II) ion and half of a ligand. The Cd(II) ion is in a distorted octahedral N4S2 environment with L4 acting as a tetradentate chelate. The donor atoms of L4 form an approximate equatorial plane with an angle of 10.9 between the two Cd(NS) planes. The coordination environment is completed by two axially coordinated acetonitrile molecules. It is likely, on the basis of the elemental analysis, that these weakly bound solvent molecules are removed upon drying under vacuum and replaced by water from the atmosphere. The N,S-donor bidentate arms are not individually coplanar, with a substantial dihedral twist of 40.1 between the pyrazolyl and (methylsulfanyl)phenyl rings. The 1H NMR spectrum [CdL4(MeCN)2](ClO4)2 shows two-fold symmetry in solution. The signals are shifted downfield from those of the free ligand and are consistent with complexation being retained in solution. In conclusion this set of ligands has afforded an interesting range of structural types in the complexes with Cd(II) ions. Depending on the separation between the N,S-donor units they can either bind to separate metal ions giving dinuclear complexes or one-dimensional chains, or chelate to a single Cd(II) centre giving a simple mononuclear complex. In all cases the Cd(II) centres are six-coordinate, bound by two N,S-donor units and two additional ligands (water, acetonitrile or perchlorate). 3. Experimental 3.1. General details
Fig. 6. Molecular structure of the metal complex unit of [CdL4(MeCN)2](ClO4)2. Symmetry transformations used to generate equivalent atoms: (y, x, z).
The ligands L1–L4 were prepared as previously described [3]. All other organic reagents and metal salts were purchased from Aldrich or Avocado and used as received. 1H NMR spectra were recorded on Bruker AC250, AMX-400 or DRX-500 spectrometers. Mass spectra (FAB and EI) were recorded on a VG AutoSpec magnetic sector instrument. Electrospray mass spectra were measured
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at the University of Huddersfield on a Bruker MicroTOF instrument in positive ion mode, with capillary exit and first skimmer voltages of 30 V and 60 V, respectively. Samples were prepared at a concentration of ca. 2 mg/ml in MeCN or MeNO2 and analysed by direct infusion using a Cole Parmer syringe pump at a flow rate of 3 ll/min. Spectra were acquired over an m/z range of 50–3000; several scans were averaged to provide the final spectrum. IR spectra were recorded on a Perkin–Elmer Spectrum One instrument. Samples for elemental analysis were vacuum-dried. 3.2. Preparation of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 A solution of Cd(ClO4)2 Æ H2O (58 mg, 0.19 mmol) in MeNO2 (2 cm3) was added to a solution of L1 (90 mg, 0.19 mmol) in MeNO2 (2 cm3). The colourless solution was stirred for 4 h. Diisopropyl ether diffusion into the solution gave colourless crystals of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 which were suitable for X-ray crystallography (Yield: 103 mg, 68%). Anal. Calc. for C56H52Cd2Cl4N8O16S4(H2O)2 (1623.98): C, 41.42; H, 3.48; N, 6.90. Found: C, 41.39; H, 3.44; N, 6.82%. ES MS: m/z 1489.0 {Cd2(L1)2(ClO4)3}+, 1177.2 {Cd(L1)2(ClO4)}+, 1006.84 {Cd2L1(ClO4)3}+, 695.0 {Cd2(L1)2(ClO4)2}2+ and/or {CdL1ClO4}+, 430.4 {Cd2(L1)2ClO4}3+. 1H NMR (500 MHz, MeNO2): d (ppm) 7.65 (2H, d; pyrazolyl H5), 7.48 (2H, m; methylthiophenyl H3), 7.31–7.37 (4H, m; methylthiophenyl H5, H6), 7.25 (4H, s; phenyl), 7.20 (2H, ddd; methylthiophenyl H4), 6.59 (2H, d; pyrazolyl H4), 5.34 (4H, s; CH2), 2.40 (6H, s; SMe). IR (KBr disk): m (cm1) 3143 (w), 3054 (w), 2932 (w), 1627 (m), 1591 (w), 1519 (m), 1501 (m), 1465 (w), 1433 (s), 1407 (m), 1347 (m), 1331 (m), 1291 (w), 1278 (w), 1262 (w), 1222 (w), 1171 (m), 1121 (s), 1066 (s), 1039 (s), 1027 (s), 978 (m), 949 (w), 915 (m), 854 (w), 832 (w), 792 (m), 760 (s), 747 (m), 727 (w), 622 (s), 496 (w). 3.3. Preparation of {[CdL2(CH3CN)2](ClO4)2}1 Cd(ClO4)2 Æ H2O (64 mg, 0.21 mmol) was added to a solution of L2 (99 mg, 0.21 mmol) in dry MeCN (20 cm3) under N2. The colourless solution was stirred overnight and the volume reduced to 10 cm3. Diethylether diffusion into the solution gave off-white crystals of {[CdL2(CH3CN)2](ClO4)2}1 which were suitable for X-ray crystallography (Yield: 124 mg, 74%). Anal. Calc. for C28H26CdCl2N4O8S2 Æ (H2O) (811.99): C, 41.42; H, 3.48; N, 6.90. Found: C, 41.49; H, 3.34; N, 7.21%. FAB MS: m/z 596 {CdL2}, 695 {CdL2(ClO)4}. 1H NMR (500 MHz, CD3CN): d (ppm) 7.64 (2H, d, pyrazolyl H5), 7.47 (2H, ddd, methylthiophenyl H3), 7.31–7.37 (5H, m, methylthiophenyl H5, H6, phenyl), 7.16–7.23 (5H, m, methylthiophenyl H4, phenyl), 6.58 (2H, d, pyrazolyl H4), 5.34 (4H, s, CH2), 2.39 (6H, s, SMe).IR (KBr disk): m (cm1) 3143 (w), 2932 (w), 1627 (m), 1614 (m), 1592 (w), 1517 (m), 1504 (m), 1433 (s), 1406 (m), 1350 (m), 1328 (m),
1278 (w), 1221 (m), 1113 (s), 949 (w), 917 (m), 787 (w), 758 (s), 740 (w), 727 (w), 624 (s). 3.4. Preparation of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 Cd(ClO4)2 Æ H2O (40 mg, 0.13 mmol) was added to a solution of L3 (72 mg, 0.13 mmol) in dry MeCN (15 cm3). The colourless solution was stirred overnight under N2 and the solvent removed in vacuo. The crude product was recrystallised by diethylether diffusion into an acetonitrile/nitromethane (1:1) solution to give colourless crystals of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 which were suitable for X-ray crystallography (yield: 90 mg, 75%). Anal. Calc. for C72H70Cd2Cl4N10O18S4(H2O)3 (1912.33): C, 45.22; H, 4.01; N, 7.32. Found: C, 45.27; H, 3.73; N, 7.14%. ES MS: m/z 1641.1 {Cd2(L3)2(ClO4)3}+, 1329.3 {Cd(L3)2(ClO4)}+, 1080.9 {Cd2L3(ClO4)3}+, 771.1 {Cd2(L3)2(ClO4)2}2+ and/or {CdL3ClO4}+, 480.7 {Cd2(L3)2ClO4}3+. 1 H NMR (500 MHz, CD3CN): d (ppm) 7.67 (2H, br s; pyrazolyl H5), 7.43–7.56 (10H, br m), 7.36 (2H, br s), 7.29 (2H, br d), 7.01 (2H, br d), 6.61 (2H, br s; pyrazolyl H4), 5.48 (4H, br s; CH2), 2.41 (6H, br s; SCH3). IR (KBr disk): m (cm1) 3397 (s, br), 3141 (w), 3124 (w), 3014 (w), 2925 (w), 1676 (w), 1633 (w), 1605 (w), 1590 (w), 1517 (m), 1503 (m), 1463 (w), 1438 (m), 1404 (m), 1350 (m), 1343 (w), 1322 (w), 1223 (m), 1119 (s), 1104 (s), 1075 (s), 1016 (w), 931 (w), 882 (w), 789 (m), 770 (w), 754 (s), 727 (w), 695 (w), 623 (s). 3.5. Preparation of [CdL4(MeCN)2](ClO4)4 Cd(ClO4)2 Æ H2O (47 mg, 0.15 mmol) was added to a solution of L4 (80 mg, 0.15 mmol) in dry MeCN (20 cm3) under N2. The colourless solution was stirred overnight and the volume reduced to 10 cm3. Diethylether diffusion into the solution gave off-white crystals of [CdL4(MeCN)2](ClO4)2 which were suitable for X-ray crystallography. The crystals were dried in vacuo to yield, after exposure to air, [CdL4](ClO4)2 Æ 2H2O as a white powder (yield: 89 mg, 67%). Anal. Calc. for CdC32H28N4S2Cl2O8 Æ (H2O)2 (880.07): C, 43.67; H, 3.66; N, 6.37%. Found: C, 44.09; H, 3.42; N, 6.44%. ES MS: 744 {CdL4ClO4}+, 343 {CdL4(CH3CN)}2+. 1H NMR (500 MHz, CDCl3): d (ppm) 8.17 (2H, dd), 7.77 (2H, d), 7.67 (2H, dd), 7.61 (2H, dd), 7.60 (2H, dd), 7.54 (2H, td), 7.47 (2H, td), 7.43 (2H, d; pyrazolyl H5), 6.66 (2H, d, pyrazolyl H4), 5.78 (4H, s, CH2), 2.63 (6H, s, SMe). IR (KBr disk): m (cm1) 3146 (w), 3063 (w), 2932 (w), 1621 (w), 1600 (w), 1519 (m), 1505 (m), 1487 (m), 1460 (w), 1433 (s), 1406 (w), 1370 (m), 1328 (s), 1214 (m), 1101 (s), 961 (w), 950 (w), 849 (w), 823 (w), 785 (s), 769 (s), 729 (m), 681 (w), 623 (s). 3.6. X-ray crystallography X-ray crystallographic data are summarised in Table 5. For each compound a suitable crystal was coated with hydrocarbon oil and attached to the tip of a glass fibre
Table 5 Crystallographic data for the five crystal structuresa L3
Formula Formula weight T (K) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a () b () c () ˚ 3) V (A Z Dcalc (Mg/m3) l (mm1) Crystal size (mm) Reflections collected Independent reflections [Rint] Data/restraints/parameters Final R indicesb
C34H30N4S2 558.74 100(2) orthorhombic Pbca 9.4207(8) 8.8218(8) 33.408(3) 90 90 90 2776.4(4) 4 1.337 0.224 0.22 · 0.09 · 0.04 39 267 3180 [0.0794] 3180/0/182 R1 = 0.0377, wR2 = 0.1138 0.228 and 0.233
Largest difference in peak and ˚ 3) hole (e A a b
[Cd2(L1)2(H2O)2(ClO4)2] (ClO4)2 Æ 4MeNO2 C60H68Cd2Cl4N12O26S4 1868.10 100(2) monoclinic C2/c 75.521(4) 18.1666(9) 17.5515(9) 90 91.682(2) 90 24069(2) 12 1.547 0.848 0.32 · 0.22 · 0.12 362 445 21 186 [0.0483] 21186/62/1467 R1 = 0.0551, wR2 = 0.1377 1.686 and 1.205
{[CdL2(MeCN)2](ClO4)2}1 C34H35CdCl2N7O8S2 917.11 150(2) monoclinic Cc 21.489(13) 12.675(7) 14.589(9) 90 90.855(10) 90 3973(4) 4 1.533 0.847 0.24 · 0.20 · 0.10 17 606 6962 [0.1173] 6962/34/486 R1 = 0.0861, wR2 = 0.2297
[Cd2(L3)2(H2O)2(MeCN)2] (ClO4)4a C72H66Cd2Cl4N10O18S4 1854.19 120(2) triclinic P 1 11.874(3) 12.599(3) 14.684(4) 74.058(2) 89.679(2) 63.440(2) 1871.7(8) 1 1.645 0.900 0.10 · 0.02 · 0.02 19 014 9907 [0.0459] 9907/22/518 R1 = 0.0670, wR2 = 0.1880
[Cd(L4)(MeCN)2](ClO4)2 C36H34CdCl2N6O8S2 926.11 150(2) tetragonal P4(3)2(1)2 11.1155(9) 11.1155(9) 32.624(4) 90 90 90 4030.9(7) 4 1.526 0.835 0.40 · 0.32 · 0.18 46 277 4657 [0.0599] 4657/0/252 R1 = 0.0499, wR2 = 0.1368
1.642 and 2.160
2.874 and 1.288
0.828 and 0.617
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
Compound
˚ (Mo Ka) in all cases except for [Cd2(L3)2(H2O)2(MeCN)2](ClO4)4 where it was 0.6709 A ˚. The X-ray wavelength was 0.71073 A The value of R1 is based on selected data with I > 2r(I); the value of wR2 is based on all data.
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and transferred to a Bruker-SMART 1000 or APEX-2 CCD diffractometer (graphite- monochromated Mo Ka ˚ ) under a stream of cold N2. The radiation, k = 0.71073 A 3 data for [Cd2(L )2(MeCN)2(H2O)2](ClO4)4were collected at the Daresbury Synchrotron Radiation Source (station 9.8) using a Bruker SMART-APEX2 diffractometer and Si(1 1 1)-monochromated synchrotron radiation with a wavelength close to the Zr absorption edge. In all cases the data were corrected for Lorentz and polarisation effects and for absorption by semi-empirical methods (SADABS) [7] based on symmetry-equivalent and repeated reflections. The structures were solved by direct methods or heavy atom Patterson methods and refined by full-matrix leastsquares methods on F2. Hydrogen atoms were placed geometrically and refined with a riding model and with Uiso constrained to be 1.2 (1.5 for methyl groups) times Ueq of the carrier atom. Structures were solved and refined using the SHELX suite of programs [8]. Significant bond distances and angles for the structures of the metal complexes are in Tables 1–4. Specific special features or problems associated with the structure determinations are as follows. [Cd2(L1)2(ClO4)(H2O)](ClO4) Æ 4CH3NO2: the asymmetric unit consists of one complete complex molecule, one half of another complex molecule, three non-coordinated anions and six nitromethane molecules. One of the ClO4 anions is disordered over two sites and was heavily restrained to ensure stable refinement. The SQUEEZE option of PLATON was used to account for severely disordered solvent molecules which could not be satisfactorily modelled. Diffraction was weak and only data with 2h 6 50 were used in the final refinement. {[CdL2(CH3CN)2](ClO4)2 Æ MeCN}1: the asymmetric unit contains one Cd(II) ion, two half-ligands, two coordinated acetonitrile molecules, one acetonitrile solvent and two disordered ClO4 anions. Both anions were modelled with two parts and heavily restrained to ensure a stable refinement. Diffraction was weak and only data with 2h 6 50 were used in the final refinement. [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4. The asymmetric unit contains one Cd(II) ion (with a coordinated MeCN and H2O), one complete ligand and two ClO4 anions. One ClO4 anion is disordered over two parts and has been restrained accordingly. The hydrogen atoms on the coordinated H2O molecule have not been located. Acknowledgements We thank the New Zealand Tertiary Education Commission for a Top Achiever Doctoral scholarship to T.K.R., EPSRC (UK) for funding of the UK National Crystallography Service, and CCLRC (UK) for access to synchrotron facilities. Appendix A. Supplementary material CCDC 631343, 631344, 631345, 631346 and 631347 contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge via http:// www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.poly.2007.01.012. References [1] (a) J.-C.G. Bu¨nzli, C. Piguet, Chem. Rev. 102 (2002) 1897; (b) G.F. Swiegers, T.J. Malefetse, Coord. Chem. Rev. 225 (2002) 91; (c) F.A. Cotton, C. Lin, C.A. Murillo, Account Chem. Res. 34 (2001) 759; (d) C.H.M. Amijs, G.P.M. van Klink, G. van Koten, Dalton Trans. (2006) 308; (e) D. Fiedler, D.H. Leung, R.G. Bergman, K.N. Raymond, Account Chem. Res. 38 (2005) 349; (f) M. Fujita, M. Tominaga, A. Hori, B. Therrien, Account Chem. Res. 38 (2005) 369; (g) S.R. Seidel, P.J. Stang, Account Chem. Res. 35 (2002) 972; (h) N.W. Ockwig, O. Delgado-Friedrichs, M. O’Keeffe, O.M. Yaghi, Account Chem. Res. 38 (2005) 176; (i) M. Eddaoudi, D.B. Moler, H.L. Li, B.L. Chen, T.M. Reineke, M. O’Keeffe, O.M. Yaghi, Account Chem. Res. 34 (2001) 176; (j) O. Mamula, A. Zelewsky, Coord. Chem. Rev. 242 (2003) 87; (k) J.-M. Lehn, Science 295 (2002) 2400. [2] E.C. Constable, Polynuclear transition metal helicates, in: J.-P. Sauvage (Ed.), Comprehensive Supramolecular Chemistry, vol. 9, Elsevier, Oxford, 1996, p. 213. [3] T.K. Ronson, H. Adams, M.D. Ward, Eur. J. Inorg. Chem. (2005) 4533. [4] (a) M.C. Hong, W.P. Su, R. Cao, M. Fujita, J.X. Lu, Chem. Eur. J. 6 (2000) 427; (b) C.Y. Su, S. Liao, H.L. Zhu, B.S. Kang, X.M. Chen, H.Q. Liu, J. Chem. Soc., Dalton Trans. (2000) 1985; (c) S. Liao, C.Y. Su, H.X. Zhang, J.L. Shi, Z.Y. Zhou, H.Q. Liu, A.S.C. Chan, B.S. Kang, Inorg. Chim. Acta 336 (2002) 151; (d) S. Tavacoli, T.A. Miller, R.L. Paul, J.C. Jeffery, M.D. Ward, Polyhedron 22 (2003) 507; (e) Y. Zheng, M. Du, J.-R. Li, R.-H. Zhang, X.-H. Bu, Dalton Trans. (2003) 1509; (f) M. Oh, C.L. Stern, C.A. Mirkin, Chem. Commun. (2004) 2684; (g) Y.-B. Xie, C. Zhang, J.-R. Li, X.-H. Bu, Dalton Trans. (2004) 562; (h) D.A. McMorran, C.M. Hartshorn, P.J. Steel, Polyhedron 23 (2004) 1055. [5] (a) A.M.W. Cargill Thompson, D.A. Bardwell, J.C. Jeffery, L.H. Rees, M.D. Ward, J. Chem. Soc., Dalton Trans. (1997) 721; (b) R.E. Rosenfeld Jr., R. Parthasarathy, J.D. Dunitz, J. Am. Chem. Soc. 99 (1977) 4860; (c) F.T. Burling, B.M. Goldstein, J. Am. Chem. Soc. 114 (1992) 2313; (d) F.T. Burling, B.M. Goldstein, Acta Crystallogr. B49 (1993) 738; (e) G.R. Desiraju, V. Nalini, J. Mater. Chem. 1 (1991) 201; (f) D. Britton, J.D. Dunitz, Helv. Chim. Acta 63 (1980) 1068; (g) M. Iwaoka, S. Tomoda, J. Am. Chem. Soc. 118 (1996) 8077; (h) M. Iwaoka, S. Takemoto, M. Okada, S. Tomoda, Bull. Chem. Soc. Jpn. 75 (2002) 1611; (i) I. Vargas-Baca, T. Chivers, Phosphorus, Sulfur, Silicon Related Elements 164 (2000) 207; (j) R.M. Minyaev, V.I. Minkin, Can. J. Chem. 76 (1998) 776. [6] (a) A.M. Garcia-Deibe, J.S. Metalobos, M. Fondo, M. Vazquez, M.R. Bermejo, Inorg. Chim. Acta 357 (2004) 2561; (b) X. Sun, D.W. Johnson, K.N. Raymond, E.H. Wong, Inorg. Chem. 40 (2001) 4504; (c) Y.P. Cai, C.Y. Su, C.L. Chen, Y.M. Li, B.S. Kang, A.S.C. Chan, W. Kaim, Inorg. Chem. 42 (2003) 163;
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785 (d) W. Schuh, H. Kopacka, K. Wurst, P. Peringer, Eur. J. Inorg. Chem. (2002) 2202; (e) M. Albrecht, I. Janser, H. Houjou, R. Frohlich, Chem. Eur. J. 10 (2004) 2839; (f) M. Albrecht, Chem. Eur. J. 3 (1997) 1466;
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Synthesis and structures of cadmium(II) complexes of a series of multinucleating N/S donor ligands Tanya K. Ronson a, Harry Adams a, Lindsay P. Harding b, Ross W. Harrington c, William Clegg c,d, Michael D. Ward a,* b
a Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK Department of Chemistry and Biological Sciences, University of Huddersfield, Huddersfield, HD1 3DH, UK c School of Natural Sciences (Chemistry), Newcastle University, Newcastle upon Tyne, NE1 7RU, UK d CCLRC Daresbury Laboratory, Warrington WA4 4AD, UK
Received 2 January 2007; accepted 16 January 2007 Available online 21 January 2007
Abstract The coordination chemistry of a series of bis-bidentate ligands with cadmium(II) ions has been investigated. The ligands, containing two N,S-donor chelating (pyrazolyl/thioether) fragments, have afforded complexes of a variety of structural types (dinuclear M2L2 ‘mesocate’ complexes, a one-dimensional chain coordination polymer and a simple mononuclear complex) according to whether the bisbidentate ligands act as bridges spanning two metal ions, or a tetradentate chelate to a single metal ion. The p-phenylene and m-biphenyl spaced ligands L1 and L3 form dinuclear M2L2 complexes where the ligands are arranged in a ‘side-by-side’ fashion. In contrast the mphenylene spaced ligand L2 forms a one-dimensional coordination polymer where the ligands adopt a highly folded conformation. The 1,8-naphthalene spaced ligand L4 adopts a tetradendate chelating mode and affords a simple mononuclear complex. 2007 Elsevier Ltd. All rights reserved. Keywords: Cadmium; Coordination chemistry; Crystal structure; Mesocate; Coordination polymer
1. Introduction The self-assembly of elaborate metallosupramolecular assemblies from relatively simple bridging ligands and labile metal ions continues to be an intensely popular area of study, partly because of the insight that these systems offer into control of self-assembly processes, and partly because the resulting assemblies can have a range of useful properties in materials and host-guest chemistry [1]. With regard to the ligands, a minimum condition is that the binding sites must be arranged so that they bridge two or more metal ions, otherwise simple mononuclear complexes may result. If a ligand is flexible, the competition between bridging and chelating coordination modes is an important *
Corresponding author. Tel.: +44 0114 2229484; fax: +44 0114 2229346. E-mail address: m.d.ward@sheffield.ac.uk (M.D. Ward). 0277-5387/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2007.01.012
factor in determining the course of a self-assembly reaction [2]. As part of our continuing studies into the coordination chemistry of flexible ligands containing bidentate chelating groups, we have recently reported the synthesis of a series of new ligands with potentially N,S-chelating arms derived from 3-[2-(methylsulfanyl)phenyl]pyrazole linked to central aromatic spacers by methylene units [3]. The reaction of these ligands with Ag(I) and Cu(I) ions resulted in a series of complexes with 1:1 metal:ligand stochiometry, in which each four-coordinate metal centre is bound by two coordinating arms to give one of three general structural types depending on the structure of the ligand and the nature of the spacer unit separating the two N,S-donor termini. These structural types are (i) dinuclear M2L2 complexes – either helicates, in which the ligands are twisted around one another, or mesocates, in which the ligands adopt a ‘side-by-side’ arrangement; (ii) infinite one-dimensional
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Fig. 1. Molecular structure of L3. Symmetry operation to generate equivalent atoms: (x, y, z + 1).
Scheme 1.
coordination chains [ML]n which contain an alternating sequence M-(l-L)-M-(l-L). . . along the chain, which may also have a chiral helicate structure; (iii) mononuclear complexes ML in which the ligand is flexible enough to coordinate both N,S-donor units to the same metal centre in a tetradentate chelating mode [3]. In this paper we describe the synthesis and structural characterisation of complexes of the potentially bis-bidentate ligands L1–L4 (see Scheme 1) with Cd(II). This metal ion commonly adopts a six-coordinate environment, so we may see either complexes with a M2L3 stoichiometry (or some higher multiple), or the involvement of additional ligands in the coordination sphere to complete the octahedral coordination environment. We note that bridging ligands based on two or more N,S-donor chelating units have recently been studied by several groups because of their propensity to form coordination networks and chains when coordinated to ‘soft’ metal ions [4]. 2. Results and discussion The ligands L1–L4 were prepared according to the previously described method, by reaction of 3-[2-(methylsulfanyl)phenyl]pyrazole with an appropriate bromomethylated aromatic compound (the spacer unit) in the presence of hydroxide ion under phase transfer conditions [3]. The crys-
tal structures of L1, L2 and L4 were reported previously [3]. The crystal structure of L3 is shown in Fig. 1. The individual bond distances and angles within the molecule are unremarkable. The molecule lies across a centre of symmetry, such that the two halves are crystallographically equivalent. The (methylsulfanyl)phenyl/pyrazole units adopt a cisoid configuration with the methyl group pointing away from the lone pairs of the pyrazole nitrogen atoms resulting in an intramolecular N S interaction. This is consistent with the known tendency of divalent S (and Se) atoms to interact with nucleophilic atoms [in this case the pyrazolyl N(2) nitrogen atom] giving short non-bonded contacts [5]. The non˚ is similar to that bonded N(2) S(1) distance of 2.878(2) A observed for L1 [3] and the N(2)–S(1)–C(17) angle of 167.1(1) shows a small deviation from linearity. The reaction of tetradentate ligands L1–L4 with a metal ion that commonly displays six-fold coordination would be expected, in the absence of any coordinating anions or solvent molecules, to afford a complex with a 2:3 metal/ligand ratio. The reaction of the p-phenylene spaced ligand L1 with Cd(ClO4)2 Æ H2O in nitromethane gave a colourless solution; diisopropyl ether diffusion into this solution afforded crystals which analysed with a 1:1 metal/ligand ratio, independently of the starting M:L ratio used in the synthesis (2:3 or 1:1). The ES mass spectrum showed peaks at m/z 1489.0, 695.0 and 430.4 corresponding to the dinuclear species [Cd2(L1)2(ClO4)4-x]x+ (x = 1, 2, 3) showing sequential loss of ClO4 anions. An m/z value of 695.0 may also correspond to the mononuclear species [CdL1(ClO4)]+, but the other two peaks are unambiguous. There are also peaks for fragmentation products at m/z 1177.2 and 1006.8 corresponding to [Cd(L1)2(ClO4)]+ and [Cd2(L1)(ClO4)3]+, respectively. The X-ray crystal structure shows that the crystalline material is the dinuclear complex [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 (Fig. 2, Table 1). The complex is achiral with both bridging ligands spanning both metal centres in a ‘side-by-side’ arrangement commonly called a ‘mesocate’ [6]. This discrete dinuclear complex is in contrast to the polymeric coordination chains obtained from reaction of Cu(I) and Ag(I) with the same ligand [3]. The asymmetric unit contains one complete [Cd2(L1)2(ClO4)2(H2O)2]2+ cation [containing Cd(1) and Cd(2)], and another half-cation [containing Cd(3)] from which the second similar but crystallographically independent cation is generated by a two-
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
Fig. 2. Structure of the metal complex unit of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 Æ 4MeNO2. Only one of the two similar independent molecules is shown.
Table 1 ˚ ) and angles () for [Cd2(L1)2(ClO4)(H2O)](ClO4) Selected bond lengths (A Cd(1)–O(30) Cd(1)–N(1) Cd(1)–O(1) Cd(1)–N(101) Cd(1)–S(101) Cd(1)–S(1) Cd(2)–O(31) Cd(2)–N(104) Cd(2)–N(4) Cd(2)–O(5) Cd(2)–S(2) Cd(2)–S(102) Cd(3)–O(32) Cd(3)–O(9) Cd(3)–N(202) Cd(3)–N(204) Cd(3)–S(202) Cd(3)–S(201) O(32)–Cd(3)–O(9) O(32)–Cd(3)–N(202) O(9)–Cd(3)–N(202) O(32)–Cd(3)–N(204) O(9)–Cd(3)–N(204) N(202)–Cd(3)– N(204) O(32)–Cd(3)–S(202) O(9)–Cd(3)–S(202) N(202)–Cd(3)–S(202) N(204)–Cd(3)–S(202) O(32)–Cd(3)–S(201) O(9)–Cd(3)–S(201) N(202)–Cd(3)–S(201) N(204)–Cd(3)–S(201) S(202)–Cd(3)–S(201)
2.308(3) 2.321(4) 2.349(3) 2.355(4) 2.6642(12) 2.6803(12) 2.285(4) 2.321(4) 2.340(4) 2.362(4) 2.6723(14) 2.6933(14) 2.296(4) 2.328(4) 2.329(4) 2.358(4) 2.6872(13) 2.6979(13) 83.64(16) 91.86(15) 89.86(14) 168.61(15) 95.68(15) 99.51(14) 94.78(11) 92.47(10) 173.17(10) 73.87(10) 90.57(13) 169.39(11) 81.42(10) 91.73(10) 96.88(4)
O(30)–Cd(1)–N(1) O(30)–Cd(1)–O(1) N(1)–Cd(1)–O(1) O(30)–Cd(1)–N(101) N(1)–Cd(1)–N(101) O(1)–Cd(1)–N(101) O(30)–Cd(1)–S(101) N(1)–Cd(1)–S(101) O(1)–Cd(1)–S(101) N(101)–Cd(1)–S(101) O(30)–Cd(1)–S(1) N(1)–Cd(1)–S(1) O(1)–Cd(1)–S(1) N(101)–Cd(1)–S(1) S(101)–Cd(1)–S(1) O(31)–Cd(2)–N(104) O(31)–Cd(2)–N(4) N(104)–Cd(2)–N(4) O(31)–Cd(2)–O(5) N(104)–Cd(2)–O(5) N(4)–Cd(2)–O(5) O(31)–Cd(2)–S(2) N(104)–Cd(2)–S(2) N(4)–Cd(2)–S(2) O(5)–Cd(2)–S(2)
92.18(13) 78.93(13) 92.37(13) 170.96(13) 95.44(13) 95.87(13) 98.02(9) 169.66(10) 91.25(9) 74.55(10) 91.83(9) 82.30(10) 169.18(9) 94.00(10) 95.63(4) 92.46(15) 169.88(15) 95.74(14) 78.99(15) 93.13(14) 94.61(15) 97.65(11) 169.44(11) 74.55(10) 91.81(10)
O(31)–Cd(2)–S(102) N(104)–Cd(2)–S(102) N(4)–Cd(2)–S(102) O(5)–Cd(2)–S(102) S(2)–Cd(2)–S(102)
91.53(11) 81.79(11) 95.50(10) 169.09(11) 94.83(4)
fold rotation. The six-coordinate Cd(II) ions are coordinated by one N,S-chelating arm from each ligand, with a water molecule and a ClO4 anion completing the distorted octahedral coordination. The Cd Cd separations within ˚ [between Cd(1) the dinuclear complex cations of 10.8 A ˚ and Cd(2)] and 10.4 A [between Cd(3) and its symmetry equivalent] are longer than those observed in the polymeric ˚ ) and Ag(I) (7.6 A ˚ ). The complexes of L1 with Cu(I) (9.8 A
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˚ ) bonds are longer than the Cd–N Cd–S (average 2.68 A ˚ ) and ˚ (average 2.34 A), Cd–Operchlorate (average 2.30 A ˚ Cd–Owater bonds (average 2.35 A). The bidentate (methylsulfanyl)phenyl/pyrazole units show large deviations from planarity with torsion angles between the rings in the range 32–53. The central phenylene spacers of the ligands are inclined parallel to each other [angle of approx. 1 between the rings for the molecule with Cd(1) and Cd(2) and exactly parallel by symmetry for the molecule with Cd(3)] and show a p–p stacking interaction. The distance ˚ for the molecule between these stacked rings is 3.5–3.6 A ˚ containing Cd(1) and Cd(2) and 3.2 A for the molecule containing Cd(3). The 1H NMR spectrum of the redissolved crystals of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 shows a two-fold-symmetric environment for L1 in solution. The pyrazole H5 signal is shifted downfield by ca. 0.3 ppm compared to the free ligand but there is little shift in the other signals. The reaction of the m-phenylene spaced ligand L2 with Cd(ClO4)2 Æ H2O in acetonitrile resulted in a colourless solution. Diethylether diffusion into the reaction mixture gave colourless crystals whose elemental analysis indicated a 1:1 metal/ligand ratio. The FAB mass spectrum showed peaks at m/z 596 for {CdL2}+ and 695 {CdL2(ClO4)}+. The X-ray crystal structure shows that the crystalline material is the infinite one-dimensional coordination polymer {[CdL2(CH3CN)2](ClO4)2}1 (Figs. 3 and 4, Table 2). Each Cd(II) ion is coordinated by an N,S-chelating arm from each of two separate ligands. Two cis-coordinated acetontrile molecules make up the distorted octahedral coordination. The Cd–S and Cd–N bond lengths are similar to those of [Cd2(L1)2(ClO4)(H2O)](ClO4). The Cd Cd separation between metals linked by the same bridging ligand ˚ , slightly longer than in the copper complex is 7.33 A ˚ ) [3]. The ligands are folded such {[CuL2](BF4)}1 (6.17 A that the pyrazole rings are almost perpendicular to the central phenyl spacer (angles of 94 and 96 between the mean planes of the rings). This folding brings the Cd(II) ions closer together than in the complex with L1 [the average Cd Cd separation in [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 is
Fig. 3. Structure of the metal complex unit of {[CdL2(CH3CN)2](ClO4)2}1 showing the coordination geometry around the Cd(II) centres.
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Fig. 4. Structure of the one-dimensional polymeric chain of {[CdL2(CH3CN)2](ClO4)2}1, with alternate ligands shaded differently for clarity. Only the N atoms of the coordinated MeCN ligands are shown.
˚ ] in which the ligand adopted a more extended con10.6 A formation. The twist angles between the rings within each bidentate (methylsulfanyl)phenyl/pyrazole unit are ca. 34 and 28. There is an angle of 24 between the planes of the pyrazole ring containging N(3) and a (methylsulfanyl)phenyl from the next ligand, for which the inter-ring ˚ , possibly indicative separation covers the range 3.2–4.3 A of a weak p–p stacking interaction. The 1H NMR spectrum of {[CdL2(CH3CN)2](ClO4)2}1 shows a two-fold-symmetric environment for L2 in solution. The fact that the crystals dissolve in acetonitrile is indicative of the coordination polymer breaking up to form solvated {CdL2}2+ units. The reaction of the m-biphenyl spaced ligand L3 with one equivalent of Cd(ClO4)2 Æ H2O in dry acetonitrile under an N2 atmosphere followed by evaporation gave the crude complex as an oil. Recrystallisation by diethylether vapour diffusion into an acetonitrile/nitromethane (1:1) solution gave a crystalline material which was found to be the discrete dinuclear complex [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 (Fig. 5, Table 3), in contrast to the coordination polymers obtained from the reaction of the same ligand with Cu(I)
Table 2 ˚ ) and angles () for {[CdL2(CH3CN)2](ClO4)2}1 Selected bond lengths (A Cd(1)–N(4) Cd(1)–N(2) Cd(1)–N(5) Cd(1)–N(6) Cd(1)–S(2) Cd(1)–S(1) N(4)–Cd(1)–N(2) N(4)–Cd(1)–N(5) N(2)–Cd(1)–N(5) N(4)–Cd(1)–N(6) N(5)–Cd(1)–S(2) N(6)–Cd(1)–S(2) N(4)–Cd(1)–S(1) N(2)–Cd(1)–S(1) N(2)–Cd(1)–N(6) N(5)–Cd(1)–N(6) N(4)–Cd(1)–S(2) N(2)–Cd(1)–S(2) N(5)–Cd(1)–S(1) N(6)–Cd(1)–S(1) S(2)–Cd(1)–S(1)
2.300(13) 2.376(11) 2.389(11) 2.389(14) 2.636(4) 2.699(4) 96.8(4) 100.7(4) 97.5(4) 166.5(4) 85.3(3) 91.7(3) 96.0(2) 70.0(3) 95.7(4) 82.7(4) 75.6(3) 172.3(3) 160.3(3) 83.4(3) 109.15(11)
Fig. 5. Structure of the [Cd2(L3)2(MeCN)2(H2O)2](ClO4).
metal
complex
unit
of
and Ag(I) [3]. The complex lies astride a centre of symmetry such that the asymmetric unit contains one Cd(II) ion and one complete ligand; clearly therefore it is achiral and not a helicate. Both ligands bridge both metal centres ˚ , almost identical to that with a Cd Cd distance of 10.8 A
Table 3 ˚) Selected bond lengths (A [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 Cd(1)–N(5) Cd(1)–O(1) Cd(1)–N(4A) Cd(1)–N(1) Cd(1)–S(1) Cd(1)–S(2A) N(5)–Cd(1)–O(1) N(5)–Cd(1)–N(4A) O(1)–Cd(1)–N(4A) N(5)–Cd(1)–N(1) O(1)–Cd(1)–N(1) N(4A)–Cd(1)–N(1) N(5)–Cd(1)–S(1) O(1)–Cd(1)–S(1) N(4A)–Cd(1)–S(1) N(1)–Cd(1)–S(1) N(5)–Cd(1)–S(2A) O(1)–Cd(1)–S(2A) N(4A)–Cd(1)–S(2A) N(1)–Cd(1)–S(2A) S(1)–Cd(1)–S(2A)
and
angles
()
for
2.297(5) 2.307(3) 2.314(4) 2.347(4) 2.6263(15) 2.7678(15) 82.06(15) 102.06(17) 99.39(13) 95.43(15) 168.43(13) 92.18(13) 86.87(14) 92.34(10) 166.08(10) 76.21(10) 162.55(13) 84.16(10) 69.71(10) 100.15(10) 104.37(4)
Symmetry transformations used to generate equivalent atoms: (x + 1, y + 1, z + 1).
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
in [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 despite the longer spacer in L3. The Cd(II) ions are in a distorted octahedral geometry with one acetonitrile and one water molecule completing the coordination. The acetonitrile molecules are attached at an angle with the Cd–N–C angles being 142.8(5). The bond lengths to Cd(II) are typical of complexes in this series. The twist angles within the biphenyl spacers are 41.8 and the twist angles within each bidentate (methylsulfanyl)phenyl/pyrazole units are 34.2 and 28.8. There is a p–p stacking interaction between the pyrazole ring containing N(1) and the (methylsulfanyl)phenyl ring of the other ligand (angle of 20.6 between the mean planes ˚ between the rings). of the two rings, distance of 3.2–4.1 A The biphenyl spacers are not involved in any p–p stacking interactions. The electrospray mass spectrum of the crystals shows peaks at m/z 1641.1, 771.1 and 480.7 corresponding to the dinuclear species [Cd2(L3)2(ClO4)4-x]x+ (x = 1, 2, 3) with sequential loss of perchlorate anions. The m/z value of 771.1 may also correspond to the mononuclear species {Cd(L3)ClO4}+ but the other peaks are unambiguous. There are also peaks for Cd2L3 and Cd(L3)2 fragments. The 1H NMR spectrum of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 is broad, indicative of a dynamic process in solution. The reaction of L4 with one equivalent of Cd(ClO4)2 Æ H2O in dry acetonitrile under an N2 atmosphere resulted in a colourless solution. Diethylether diffusion into the reaction mixture gave colourless crystals whose elemental analysis was consistent with the formulation [CdL4(H2O)2](ClO4)4. The electrospray mass spectrum showed peaks at m/z 744 [{CdL4(ClO4)}+] and 343 [{CdL4(MeCN)}2+], consistent with formation of a mononuclear complex. The X-ray crystal structure confirms that the crystalline material [CdL4(MeCN)2](ClO4)2 is a mononuclear complex (Fig. 6, Table 4) in contrast to the dinuclear structures obtained with L1 and L3 and the polymeric structure obtained with L2. The complex has two-fold rotation symmetry such that the asymmetric unit contains half of a
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Table 4 ˚ ) and angles () for [Cd2(L1)2(ClO4)(H2O)](ClO4) Selected bond lengths (A Cd(1)–N(3) Cd(1)–N(2) Cd(1)–S(1) N(3)–Cd(1)–N(3A) N(3)–Cd(1)–N(2) N(3A)–Cd(1)–N(2) N(3)–Cd(1)–N(2A) N(3A)–Cd(1)–N(2A) N(2)–Cd(1)–N(2A) N(3)–Cd(1)–S(1A) N(3A)–Cd(1)–S(1A) N(2)–Cd(1)–S(1A) N(2A)–Cd(1)–S(1A) N(3)–Cd(1)–S(1) N(3A)–Cd(1)–S(1) N(2)–Cd(1)–S(1) N(2A)–Cd(1)–S(1) S(1A)–Cd(1)–S(1)
2.329(4) 2.344(4) 2.7013(14) 175.1(2) 87.49(14) 95.60(14) 95.60(14) 87.49(14) 101.8(2) 85.64(11) 91.29(11) 173.12(9) 78.38(11) 91.29(11) 85.64(11) 78.38(11) 173.12(9) 102.30(7)
Symmetry transformations used to generate equivalent atoms: (y, x, z).
Cd(II) ion and half of a ligand. The Cd(II) ion is in a distorted octahedral N4S2 environment with L4 acting as a tetradentate chelate. The donor atoms of L4 form an approximate equatorial plane with an angle of 10.9 between the two Cd(NS) planes. The coordination environment is completed by two axially coordinated acetonitrile molecules. It is likely, on the basis of the elemental analysis, that these weakly bound solvent molecules are removed upon drying under vacuum and replaced by water from the atmosphere. The N,S-donor bidentate arms are not individually coplanar, with a substantial dihedral twist of 40.1 between the pyrazolyl and (methylsulfanyl)phenyl rings. The 1H NMR spectrum [CdL4(MeCN)2](ClO4)2 shows two-fold symmetry in solution. The signals are shifted downfield from those of the free ligand and are consistent with complexation being retained in solution. In conclusion this set of ligands has afforded an interesting range of structural types in the complexes with Cd(II) ions. Depending on the separation between the N,S-donor units they can either bind to separate metal ions giving dinuclear complexes or one-dimensional chains, or chelate to a single Cd(II) centre giving a simple mononuclear complex. In all cases the Cd(II) centres are six-coordinate, bound by two N,S-donor units and two additional ligands (water, acetonitrile or perchlorate). 3. Experimental 3.1. General details
Fig. 6. Molecular structure of the metal complex unit of [CdL4(MeCN)2](ClO4)2. Symmetry transformations used to generate equivalent atoms: (y, x, z).
The ligands L1–L4 were prepared as previously described [3]. All other organic reagents and metal salts were purchased from Aldrich or Avocado and used as received. 1H NMR spectra were recorded on Bruker AC250, AMX-400 or DRX-500 spectrometers. Mass spectra (FAB and EI) were recorded on a VG AutoSpec magnetic sector instrument. Electrospray mass spectra were measured
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at the University of Huddersfield on a Bruker MicroTOF instrument in positive ion mode, with capillary exit and first skimmer voltages of 30 V and 60 V, respectively. Samples were prepared at a concentration of ca. 2 mg/ml in MeCN or MeNO2 and analysed by direct infusion using a Cole Parmer syringe pump at a flow rate of 3 ll/min. Spectra were acquired over an m/z range of 50–3000; several scans were averaged to provide the final spectrum. IR spectra were recorded on a Perkin–Elmer Spectrum One instrument. Samples for elemental analysis were vacuum-dried. 3.2. Preparation of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 A solution of Cd(ClO4)2 Æ H2O (58 mg, 0.19 mmol) in MeNO2 (2 cm3) was added to a solution of L1 (90 mg, 0.19 mmol) in MeNO2 (2 cm3). The colourless solution was stirred for 4 h. Diisopropyl ether diffusion into the solution gave colourless crystals of [Cd2(L1)2(ClO4)2(H2O)2](ClO4)2 which were suitable for X-ray crystallography (Yield: 103 mg, 68%). Anal. Calc. for C56H52Cd2Cl4N8O16S4(H2O)2 (1623.98): C, 41.42; H, 3.48; N, 6.90. Found: C, 41.39; H, 3.44; N, 6.82%. ES MS: m/z 1489.0 {Cd2(L1)2(ClO4)3}+, 1177.2 {Cd(L1)2(ClO4)}+, 1006.84 {Cd2L1(ClO4)3}+, 695.0 {Cd2(L1)2(ClO4)2}2+ and/or {CdL1ClO4}+, 430.4 {Cd2(L1)2ClO4}3+. 1H NMR (500 MHz, MeNO2): d (ppm) 7.65 (2H, d; pyrazolyl H5), 7.48 (2H, m; methylthiophenyl H3), 7.31–7.37 (4H, m; methylthiophenyl H5, H6), 7.25 (4H, s; phenyl), 7.20 (2H, ddd; methylthiophenyl H4), 6.59 (2H, d; pyrazolyl H4), 5.34 (4H, s; CH2), 2.40 (6H, s; SMe). IR (KBr disk): m (cm1) 3143 (w), 3054 (w), 2932 (w), 1627 (m), 1591 (w), 1519 (m), 1501 (m), 1465 (w), 1433 (s), 1407 (m), 1347 (m), 1331 (m), 1291 (w), 1278 (w), 1262 (w), 1222 (w), 1171 (m), 1121 (s), 1066 (s), 1039 (s), 1027 (s), 978 (m), 949 (w), 915 (m), 854 (w), 832 (w), 792 (m), 760 (s), 747 (m), 727 (w), 622 (s), 496 (w). 3.3. Preparation of {[CdL2(CH3CN)2](ClO4)2}1 Cd(ClO4)2 Æ H2O (64 mg, 0.21 mmol) was added to a solution of L2 (99 mg, 0.21 mmol) in dry MeCN (20 cm3) under N2. The colourless solution was stirred overnight and the volume reduced to 10 cm3. Diethylether diffusion into the solution gave off-white crystals of {[CdL2(CH3CN)2](ClO4)2}1 which were suitable for X-ray crystallography (Yield: 124 mg, 74%). Anal. Calc. for C28H26CdCl2N4O8S2 Æ (H2O) (811.99): C, 41.42; H, 3.48; N, 6.90. Found: C, 41.49; H, 3.34; N, 7.21%. FAB MS: m/z 596 {CdL2}, 695 {CdL2(ClO)4}. 1H NMR (500 MHz, CD3CN): d (ppm) 7.64 (2H, d, pyrazolyl H5), 7.47 (2H, ddd, methylthiophenyl H3), 7.31–7.37 (5H, m, methylthiophenyl H5, H6, phenyl), 7.16–7.23 (5H, m, methylthiophenyl H4, phenyl), 6.58 (2H, d, pyrazolyl H4), 5.34 (4H, s, CH2), 2.39 (6H, s, SMe).IR (KBr disk): m (cm1) 3143 (w), 2932 (w), 1627 (m), 1614 (m), 1592 (w), 1517 (m), 1504 (m), 1433 (s), 1406 (m), 1350 (m), 1328 (m),
1278 (w), 1221 (m), 1113 (s), 949 (w), 917 (m), 787 (w), 758 (s), 740 (w), 727 (w), 624 (s). 3.4. Preparation of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 Cd(ClO4)2 Æ H2O (40 mg, 0.13 mmol) was added to a solution of L3 (72 mg, 0.13 mmol) in dry MeCN (15 cm3). The colourless solution was stirred overnight under N2 and the solvent removed in vacuo. The crude product was recrystallised by diethylether diffusion into an acetonitrile/nitromethane (1:1) solution to give colourless crystals of [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4 which were suitable for X-ray crystallography (yield: 90 mg, 75%). Anal. Calc. for C72H70Cd2Cl4N10O18S4(H2O)3 (1912.33): C, 45.22; H, 4.01; N, 7.32. Found: C, 45.27; H, 3.73; N, 7.14%. ES MS: m/z 1641.1 {Cd2(L3)2(ClO4)3}+, 1329.3 {Cd(L3)2(ClO4)}+, 1080.9 {Cd2L3(ClO4)3}+, 771.1 {Cd2(L3)2(ClO4)2}2+ and/or {CdL3ClO4}+, 480.7 {Cd2(L3)2ClO4}3+. 1 H NMR (500 MHz, CD3CN): d (ppm) 7.67 (2H, br s; pyrazolyl H5), 7.43–7.56 (10H, br m), 7.36 (2H, br s), 7.29 (2H, br d), 7.01 (2H, br d), 6.61 (2H, br s; pyrazolyl H4), 5.48 (4H, br s; CH2), 2.41 (6H, br s; SCH3). IR (KBr disk): m (cm1) 3397 (s, br), 3141 (w), 3124 (w), 3014 (w), 2925 (w), 1676 (w), 1633 (w), 1605 (w), 1590 (w), 1517 (m), 1503 (m), 1463 (w), 1438 (m), 1404 (m), 1350 (m), 1343 (w), 1322 (w), 1223 (m), 1119 (s), 1104 (s), 1075 (s), 1016 (w), 931 (w), 882 (w), 789 (m), 770 (w), 754 (s), 727 (w), 695 (w), 623 (s). 3.5. Preparation of [CdL4(MeCN)2](ClO4)4 Cd(ClO4)2 Æ H2O (47 mg, 0.15 mmol) was added to a solution of L4 (80 mg, 0.15 mmol) in dry MeCN (20 cm3) under N2. The colourless solution was stirred overnight and the volume reduced to 10 cm3. Diethylether diffusion into the solution gave off-white crystals of [CdL4(MeCN)2](ClO4)2 which were suitable for X-ray crystallography. The crystals were dried in vacuo to yield, after exposure to air, [CdL4](ClO4)2 Æ 2H2O as a white powder (yield: 89 mg, 67%). Anal. Calc. for CdC32H28N4S2Cl2O8 Æ (H2O)2 (880.07): C, 43.67; H, 3.66; N, 6.37%. Found: C, 44.09; H, 3.42; N, 6.44%. ES MS: 744 {CdL4ClO4}+, 343 {CdL4(CH3CN)}2+. 1H NMR (500 MHz, CDCl3): d (ppm) 8.17 (2H, dd), 7.77 (2H, d), 7.67 (2H, dd), 7.61 (2H, dd), 7.60 (2H, dd), 7.54 (2H, td), 7.47 (2H, td), 7.43 (2H, d; pyrazolyl H5), 6.66 (2H, d, pyrazolyl H4), 5.78 (4H, s, CH2), 2.63 (6H, s, SMe). IR (KBr disk): m (cm1) 3146 (w), 3063 (w), 2932 (w), 1621 (w), 1600 (w), 1519 (m), 1505 (m), 1487 (m), 1460 (w), 1433 (s), 1406 (w), 1370 (m), 1328 (s), 1214 (m), 1101 (s), 961 (w), 950 (w), 849 (w), 823 (w), 785 (s), 769 (s), 729 (m), 681 (w), 623 (s). 3.6. X-ray crystallography X-ray crystallographic data are summarised in Table 5. For each compound a suitable crystal was coated with hydrocarbon oil and attached to the tip of a glass fibre
Table 5 Crystallographic data for the five crystal structuresa L3
Formula Formula weight T (K) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a () b () c () ˚ 3) V (A Z Dcalc (Mg/m3) l (mm1) Crystal size (mm) Reflections collected Independent reflections [Rint] Data/restraints/parameters Final R indicesb
C34H30N4S2 558.74 100(2) orthorhombic Pbca 9.4207(8) 8.8218(8) 33.408(3) 90 90 90 2776.4(4) 4 1.337 0.224 0.22 · 0.09 · 0.04 39 267 3180 [0.0794] 3180/0/182 R1 = 0.0377, wR2 = 0.1138 0.228 and 0.233
Largest difference in peak and ˚ 3) hole (e A a b
[Cd2(L1)2(H2O)2(ClO4)2] (ClO4)2 Æ 4MeNO2 C60H68Cd2Cl4N12O26S4 1868.10 100(2) monoclinic C2/c 75.521(4) 18.1666(9) 17.5515(9) 90 91.682(2) 90 24069(2) 12 1.547 0.848 0.32 · 0.22 · 0.12 362 445 21 186 [0.0483] 21186/62/1467 R1 = 0.0551, wR2 = 0.1377 1.686 and 1.205
{[CdL2(MeCN)2](ClO4)2}1 C34H35CdCl2N7O8S2 917.11 150(2) monoclinic Cc 21.489(13) 12.675(7) 14.589(9) 90 90.855(10) 90 3973(4) 4 1.533 0.847 0.24 · 0.20 · 0.10 17 606 6962 [0.1173] 6962/34/486 R1 = 0.0861, wR2 = 0.2297
[Cd2(L3)2(H2O)2(MeCN)2] (ClO4)4a C72H66Cd2Cl4N10O18S4 1854.19 120(2) triclinic P 1 11.874(3) 12.599(3) 14.684(4) 74.058(2) 89.679(2) 63.440(2) 1871.7(8) 1 1.645 0.900 0.10 · 0.02 · 0.02 19 014 9907 [0.0459] 9907/22/518 R1 = 0.0670, wR2 = 0.1880
[Cd(L4)(MeCN)2](ClO4)2 C36H34CdCl2N6O8S2 926.11 150(2) tetragonal P4(3)2(1)2 11.1155(9) 11.1155(9) 32.624(4) 90 90 90 4030.9(7) 4 1.526 0.835 0.40 · 0.32 · 0.18 46 277 4657 [0.0599] 4657/0/252 R1 = 0.0499, wR2 = 0.1368
1.642 and 2.160
2.874 and 1.288
0.828 and 0.617
T.K. Ronson et al. / Polyhedron 26 (2007) 2777–2785
Compound
˚ (Mo Ka) in all cases except for [Cd2(L3)2(H2O)2(MeCN)2](ClO4)4 where it was 0.6709 A ˚. The X-ray wavelength was 0.71073 A The value of R1 is based on selected data with I > 2r(I); the value of wR2 is based on all data.
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and transferred to a Bruker-SMART 1000 or APEX-2 CCD diffractometer (graphite- monochromated Mo Ka ˚ ) under a stream of cold N2. The radiation, k = 0.71073 A 3 data for [Cd2(L )2(MeCN)2(H2O)2](ClO4)4were collected at the Daresbury Synchrotron Radiation Source (station 9.8) using a Bruker SMART-APEX2 diffractometer and Si(1 1 1)-monochromated synchrotron radiation with a wavelength close to the Zr absorption edge. In all cases the data were corrected for Lorentz and polarisation effects and for absorption by semi-empirical methods (SADABS) [7] based on symmetry-equivalent and repeated reflections. The structures were solved by direct methods or heavy atom Patterson methods and refined by full-matrix leastsquares methods on F2. Hydrogen atoms were placed geometrically and refined with a riding model and with Uiso constrained to be 1.2 (1.5 for methyl groups) times Ueq of the carrier atom. Structures were solved and refined using the SHELX suite of programs [8]. Significant bond distances and angles for the structures of the metal complexes are in Tables 1–4. Specific special features or problems associated with the structure determinations are as follows. [Cd2(L1)2(ClO4)(H2O)](ClO4) Æ 4CH3NO2: the asymmetric unit consists of one complete complex molecule, one half of another complex molecule, three non-coordinated anions and six nitromethane molecules. One of the ClO4 anions is disordered over two sites and was heavily restrained to ensure stable refinement. The SQUEEZE option of PLATON was used to account for severely disordered solvent molecules which could not be satisfactorily modelled. Diffraction was weak and only data with 2h 6 50 were used in the final refinement. {[CdL2(CH3CN)2](ClO4)2 Æ MeCN}1: the asymmetric unit contains one Cd(II) ion, two half-ligands, two coordinated acetonitrile molecules, one acetonitrile solvent and two disordered ClO4 anions. Both anions were modelled with two parts and heavily restrained to ensure a stable refinement. Diffraction was weak and only data with 2h 6 50 were used in the final refinement. [Cd2(L3)2(MeCN)2(H2O)2](ClO4)4. The asymmetric unit contains one Cd(II) ion (with a coordinated MeCN and H2O), one complete ligand and two ClO4 anions. One ClO4 anion is disordered over two parts and has been restrained accordingly. The hydrogen atoms on the coordinated H2O molecule have not been located. Acknowledgements We thank the New Zealand Tertiary Education Commission for a Top Achiever Doctoral scholarship to T.K.R., EPSRC (UK) for funding of the UK National Crystallography Service, and CCLRC (UK) for access to synchrotron facilities. Appendix A. Supplementary material CCDC 631343, 631344, 631345, 631346 and 631347 contain the supplementary crystallographic data for this paper.
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