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DALTON J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 1639 Hard–soft interactions in early transition-metal thioether macrocyclic chemistry spectroscopic and extended X-ray absorption fine structure studies on chromium(III) thioether complexes Simon J. A. Pope Neil R. Champness and Gillian Reid * Department of Chemistry University of Southampton Highfield Southampton SO17 1BJ UK A series of chromium(III) thioether macrocyclic complexes of the form [CrX3([9]aneS3)] [CrX3([10]aneS3)] [(CrX3)2(m-[18]aneS6)] (X = Cl or Br) [CrX2(14]aneS4)]PF6 and [CrX2([16]aneS4)]PF6 (X = Cl Br or I) ([9]aneS3 = 1,4,7-trithiacyclononane [10]aneS3 = 1,4,7-trithiacyclodecane [18]aneS6 = 1,4,7,10,13,16- hexathiacyclooctadecane [14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane [16]aneS4 = 1,5,9,13-tetrathiacyclohexadecane) has been prepared and characterised by IR and UV/VIS spectroscopy microanalyses and in some cases electrospray mass spectrometry.Chromium K-edge extended X-ray absorption fine structure studies have provided information on the Cr]X and Cr]S bond-length distributions in a selection of these compounds and these together with the relatively low Dq values derived from UV/VIS spectroscopy confirm rather weak chromium(III)–thioether interactions in these unusual species involving hard metal and soft ligand combinations. In contrast to the vast number of chromium(III) complexes with hard nitrogen- and oxygen-donor ligands,1 there are very few examples of complexes with soft donor ligands such as phosphines 2–5 or thioethers.6–9 This is principally due to the severe incompatibility of the hard chromium(III) centre with the soft phosphine or thioether functions.Thioether macrocycles have been intensively studied in recent years since the ability of these ligands to stabilise unusual oxidation states and co-ordination geometries was noted. Notably however to date thioether macrocyclic chemistry has been dominated by middle and late d- and p-block ions.10 Most signifi- cantly it has been noted that while acyclic thioethers act as relatively poor ligands to metal ions when the thioether functions are included within a macrocyclic framework they tend to co-ordinate much more readily often to yield quite stable complexes. We have become interested in the possibility of utilising the additional stability characteristic of macrocyclic complexes to stabilise metal/ligand combinations which are usually considered incompatible.In this context we have been investigating the reactions of CrIII with various thioether macrocycles to determine whether the incorporation of macrocyclic environments would render such hard–soft interactions more accessible and to establish the nature of the S (thioether) to CrIII interaction. A few examples of macrocyclic thioether complexes of early transition-metal ions have been reported. These include carbonyl derivatives of Mo0 and W0,11,12 [MoCl3([9]aneS3)] ([9]aneS3 = 1,4,7-trithiacyclononane),12 the metal(II) species [MI(CO)3([9]aneS3)]1 (M = Mo or W),13 [CrCl3([9]aneS3)] [Cr(SO3CF3)3([9]aneS3)] 7 and some examples with the formula [CrCl3L] (L = S4 S5 or S6 donor macrocycle) which are thought to involve tridentate co-ordination.8 The crystal structure of the vanadium(IV) species [VOCl2([9]aneS3)] has also been reported and shows fac tridentate [9]aneS3 ligation giving V]S (trans to O) 2.634(5) (trans to Cl) 2.470(5) (mean) V]Cl 2.295(5) (mean) and V]O 1.579(4) Å.14 Very recently we have also reported the synthesis and crystal structure of the corresponding vanadium(III) species [VCl3([9]aneS3)] which also involves fac tridentate [9]aneS3 co-ordination giving V]S 2.486(3) 2.515(2) 2.500(2) V]Cl 2.279(3) 2.310(3) 2.281(3) Å.15 The only structurally characterised examples of chromium(III) thioether macrocyclic species are [CrCl3([18]aneS6)] ([18]aneS6 = 1,4,7,10,13,16-hexathiacyclooctadecane) which involves fac tridentate co-ordination of the hexathia crown to CrIII leaving three free thioether donors (see text below)8 and cis- [CrCl2([14]aneS4)]PF6 ([14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane) the structure of which we have reported involving S4Cl2 co-ordination at CrIII with Cr]S 2.393(1) 2.407(2) Cr]Cl 2.295(1) Å.9 We now report the preparation and spectroscopic characterisation of a series of chromium(III) thioether macrocyclic complexes incorporating [9]aneS3 [10]aneS3 (1,4,7- trithiacyclodecane) [14]aneS4 [16]aneS4 (1,5,9,13-tetrathiacyclohexadecane) and [18]aneS6 together with chromium K-edge extended X-ray absorption fine structure (EXAFS) studies on selected examples.Results and Discussion Reaction of [CrX3(thf )3] (X = Cl or Br thf = tetrahydrofuran) with [9]aneS3 or [10]aneS3 in a 1 1 molar ratio in CH2Cl2 solution gives the products [CrX3([9]aneS3)] or [CrX3([10]aneS3)] as powdered solids in high yield.Similarly using [CrX3(thf )3] and [18]aneS6 in a 2 1 molar ratio yields the binuclear species [(CrX3)2(m-[18]aneS6)]. We found that in order to promote coordination through the thioether donors it was necessary to remove the thf from the reaction mixture otherwise the harder O-donor thf ligand would bind preferentially. These neutral highly coloured products proved to be very poorly soluble in both chlorinated and organic solvents and attempts to dissolve them in dimethyl sulfoxide (dmso) resulted in decomposition. 1640 J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 They are relatively stable in the solid state when stored in a dry atmosphere hence all were stored in an N2-purged glove-box. The IR spectra of these species provided evidence for the presence of co-ordinated thioether and in the case of the chloro and bromo derivatives peaks were observed in most cases in the region 200–400 cm21 which might be assigned tentatively to n(Cr]X).However given that in some cases these peaks were rather weak and since n(Cr]S) would also be expected to appear in this region definitive assignments were not possible. Owing to their poor solubilities and sensitivity to moisture FAB and electrospray mass spectra proved unhelpful. However microanalytical data and UV/VIS spectroscopic data consistent with the proposed formulations were obtained in all cases. Reaction of [CrX3(thf )3] (X = Cl or Br) with [14]aneS4 or [16]aneS4 in dry MeNO2 solution in the presence of 1 molar equivalent of TlPF6 resulted in the formation of an intense blue-green or green solution for [14]aneS4 and [16]aneS4 respectively and a white precipitate of TlCl.Following removal of the TlCl by filtration the complexes [CrX2([14]aneS4)]PF6 and [CrX2([16]aneS4)]PF6 were isolated by reducing the volume of solvent to ca. 3 cm3 in vacuo and addition of dry diethyl ether. The complexes [CrI2([14]aneS4)]BF4 and [CrI2([16]- aneS4)]BF4 were obtained by addition of the tetrathioether macrocycle to a solution of [Cr(thf )6][BF4]3 in dry MeNO2. This precursor was generated in situ by treatment of [CrCl3(thf )3] with 3 molar equivalents of AgBF4 in thf solution followed by removal of the AgCl by filtration addition of MeNO2 and removal of the thf in vacuo.16 Treatment of this MeNO2 solution with 2 molar equivalents of NEt4I gave a green-brown solution from which the products were obtained by addition of diethyl ether.These cationic tetrathioether compounds are considerably more soluble than the neutral species described above dissolving readily in dry MeCN and MeNO2 and partially in dry acetone. Also the ionic products are noticeably more sensitive to hydrolysis especially in solution. Attempts to prepare similar cationic species using the smaller tetrathioether macrocycle [12]aneS4 (1,4,7,10-tetrathiacyclododecane) under similar conditions were not successful yielding only a purple insoluble product thought to be [CrX3- ([12]aneS4)] involving tridentate co-ordination of the macrocycle. The IR spectra of the cationic tetrathioether complexes con- firmed the presence of PF6 2 anion [n(PF6 2) 840 d(PF6 2) 558 cm21] and co-ordinated macrocycle in each case.For X = Cl and Br the spectra also revealed weak features in the range 200–400 cm21 which can tentatively be assigned to n(Cr–X) [n(Cr–I) is expected to occur below 200 cm21]. The fast atom bombardment (FAB) or electrospray mass spectra showed that the most intense peaks had the correct isotopic distributions at m/z = 480 corresponding to [Cr79Br81Br([14]aneS4)]1 418 to [Cr35- Cl2([16]aneS4)]1 and 508 to [Cr79Br81Br([16]aneS4)]1 as well as peaks at lower m/z due to loss of Cl or Br. No useful information was obtained from the mass spectra of the iodo derivatives possible due to the increased sensitivity of these particular species to hydrolysis. Satisfactory microanalytical data were obtained for each of these compounds confirming the proposed formulations.There are very few structurally characterised examples of chromium(III) complexes involving thioether co-ordination. Gahan and co-workers 17 reported the structure of a CrIII]S (thioether) complex. In their system the metal ion is encapsulated by an N5S donor caging ligand which enforces the thioether co-ordination [Cr]S 2.399(2) Å]. Chakravorty and coworkers 18 have reported the preparation of a series of octahedral chromium(III) compounds involving S2N2O2 chelating ligands including a crystal structure of one example which shows d(Cr]S) = 2.417(3) and 2.445(3) Å. Both of these systems involve much harder donor sets than those of the present macrocyclic thioether complexes. Of more direct relevance to our work the structure of the mononuclear complex [CrCl3- ([18]aneS6)] which involves an S3Cl3 donor set has been reported Cr]S 2.459(3) 2.442(5) 2.440(5) Cr]Cl 2.305(5) 2.279(5) 2.291(5) Å.8 The Cr]S and Cr]Cl bond lengths compare well with those in cis-[CrCl2([14]aneS4)]PF6 the structure of which we have reported in which the geometry at CrIII is a distorted octahedron with cis-chloride ligands and the tetrathia macrocycle adopting a folded conformation Cr]Cl(1) 2.295(1) Cr]S(1) 2.393(1) Cr]S(2) 2.407(2) Å.9 We noted previously that the trend in d(M]Cl) vs.d(M]S) in this compound is opposite to that observed in complexes of [14]aneS4 with late transition-metal ions. Thus in cis-[CrCl2([14]aneS4)]1 d(Cr]S) > d(Cr]Cl) (by ca. 0.1 Å) whereas in cis- [RhCl2([14]aneS4)]1,19 cis-[IrCl2([14]aneS4)]1 20 and cis-[RuCl2- ([14]aneS4)]21 d(M]S) < d(M]Cl) (by ca.0.1 Å) suggesting rather more favourable M]S interactions in the later transitionmetal complexes compared to the chromium species. In an attempt to confirm the stereochemistry at the CrIII single-crystal X-ray diffraction data were collected † on a small very weakly diffracting crystal of [CrBr2([14]aneS4)]PF6. The data were very weak and hence the final residuals rather high and it was not possible to refine the F and C atoms anisotropically due to the low data parameters ratio. However the analysis was sufficient to establish the stereochemistry of the [CrBr2([14]aneS4)]1 cation. The structure of this species shows (Fig. 1) a very similar arrangement to that seen previously for [CrCl2([14]aneS4)]1 with distorted-octahedral co-ordination at CrIII via two mutually cis-bromide ligands and the four Fig.1 View of the structure of cis-[CrBr2([14]aneS4)]1 with the numbering scheme adopted (atoms marked with * are related by a crystallographic two-fold axis) [Cr]Br(1) 2.441(8) Cr]S(1) 2.41(1) Cr]S(2) 2.39(1) Å; Br(1)]Cr]Br(1*) 95.9(3) S(1)]Cr]S(1*) 179.7(8) S(1)]Cr]S(2) 84.5(4) S(1)]Cr]S(2*) 95.2(5) S(2)]Cr]S(2*) 80.5(6)8] † C10H20Br2CrF6PS4 M = 625.3 monoclinic C2/c a = 10.808(3) b = 11.514(2) c = 15.879(3) Å b = 92.71(2)8 U = 1974 Å3 Z = 4 Dc = 2.104 g cm23 T = 150 K small dark blue block 0.30 × 0.20 × 0.10 mm m = 51.91 cm21 F(000) = 1228. Data collection used a Rigaku AFC7S four-circle diffractometer equipped with an Oxford Systems low-temperature attachment. w–2q Scans; 4571 unique reflections measured (2qmax = 508) 515 with I > 2s(I) used in all calculations.The structure was solved by direct methods22 and refined (based on F) using iterative cycles of full-matrix least squares 23 which revealed one half cation (with the Cr atom lying on a two-fold axis) and one half PF6 2 anion (with the P atom occupying a crystallographic inversion centre) in the asymmetric unit. At isotropic convergence the data were corrected for absorption using DIFABS24 (maximum minimum transmission factors = 1.000 0.582) and the Cr Br P and S atoms were then refined anisotropically and H atoms included in fixed calculated positions. The weighting scheme w21 = s2(F) gave satisfactory agreement analyses. This model refined to R R9 = 0.089 0.090 respectively and S = 2.23 for 71 parameters and the final Fourier-difference map showed residual electron-density peaks of 1.19 and 21.18 e Å23.J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 1641 Table 1 Chromium K-edge EXAFS structural data a for chromium(III) thioether macrocyclic compounds Complex [CrCl3([9]aneS3)] [CrBr3([9]aneS3)] [CrCl3([10]aneS3)] cis-[CrCl2([14]aneS4)]PF6 cis-[CrBr2([14]aneS4)]PF6 [Cr2Cl6([18]aneS6)] [CrCl3(thf )3] [CrBr3(thf )3] d(Cr]S) b/Å 2.396(11) 2.401(4) 2.361(3) 2.394(5) 2.40 (average) f 2.409(3) 2.424(4) 2.009(13) g 1.998(4) g 2s2c/Å2 0.0121(20) 0.0064(14) 0.0076(6) 0.0199(11) 0.0133(7) 0.0162(10) 0.0245(20) 0.0105(8) d(Cr]X)b/Å 2.306(9) 2.450(3) 2.239(8) 2.291(4) 2.295(1) f 2.446(1) 2.291(2) 2.295(4) 2.458(2) 2s2c/Å2 0.0119(16) 0.0095(6) 0.0257(23) 0.0086(6) 0.0072(2) 0.0094(4) 0.0092(41) 0.0110(2) Rd 22.5 21.2 20.1 17.8 16.3 19.8 23.3 18.6 Fit index e 2.9 3.5 3.8 1.9 1.4 1.9 4.1 3.3 a Recorded in transmission mode on station 7.1 or 8.1 using powdered samples diluted with BN; AFAC (a factor compensating for the reduction in amplitude due to multi-electron processes) = 0.80 for all refinements.b Standard deviations in parentheses. Note that the systematic errors in bond distances arising from data collection and analysis procedures are ±0.02–0.03 Å for well defined co-ordination shells. c Debye–Waller factor. d Defined as [e(cT 2 cE)k3 dk/ecEk3 dk] (where T is theoretical and E is experimental) 100%. e Defined as Si[(cT 2 cE)ki 3]2. f X-Ray crystallographic data from ref. 9. g d(Cr]O). thioether donors of the macrocycle which adopts a folded arrangement Cr]Br(1) 2.441(8) Cr]S(1) 2.41(1) Cr]S(2) 2.39(1) Å. As a result of the poor crystal quality the geometric parameters have high associated estimated standard deviations and hence comparisons with related species require caution.However the Cr]S distances are similar to those in both cis- [CrCl2([14]aneS4)]19 and [CrCl3([18]aneS6)],8 while d(Cr]Br) is ca. 0.15 Å longer than d(Cr]Cl) in these compounds. The angles subtended at CrIII show a marked deviated from the 90 and 1808 expected for a regular octahedron. Again this is similar to the case in cis-[CrCl2([14]aneS4)]1. Chromium K-edge EXAFS studies Owing to the limited solubilities displayed by many of the compounds isolated and their sensitivity to moisture in most cases crystals suitable for an X-ray study could not be obtained. However given the lack of structural data on compounds of Fig.2 Background-subtracted chromium K-edge EXAFS data (a) and the corresponding Fourier transform (b) for cis-[CrBr2- ([14]aneS4)]PF6 (solid line experimental; dashed line calculated data) this type we proposed that chromium K-edge EXAFS data would provide useful information regarding the metal–ligand bond lengths for the first co-ordination sphere i.e. d(Cr]S) and d(Cr]X). Importantly the spectroscopic studies carried out in parallel provided key information concerning the donor sets involved in these products. Details of the refined EXAFS data for the complexes are given in Table 1 and Fig. 2 shows a typical example. Chromium K-edge EXAFS spectra were also recorded for the [CrX3(thf )3] model compounds and for [CrCl2([14]aneS4)]PF6 in order to compare the Cr]S and Cr]X distances derived from this method with the average values obtained from X-ray crystallographic studies.The EXAFS data for the thf adducts [CrX3(thf )3] were satisfactorily modelled to a first shell of three oxygens giving Cr]O distances of 2.01 and 2.00 Å for X = Cl and Br respectively with a second shell of three halides giving d(Cr]Cl) = 2.29 and d(Cr]Br) = 2.46 Å. In the case of cis-[CrCl2([14]aneS4)]PF6 the data were satisfactorily modelled to an S4Cl2 donor set with d(Cr]Cl) = 2.29 d(Cr]S) = 2.39 Å. These results correlate very well with the average Cr]S Cr]O or Cr]X distances derived from the X-ray crystallographic studies.9,25 For [CrX3([9]aneS3)] [CrCl3([10]aneS3)] and [(CrCl3)2- (m-[18]aneS6)] the EXAFS data were modelled for three sulfurs and three halogen atoms (Cl or Br as appropriate) while for cis- [CrBr2([14]aneS4)]PF6 two shells were modelled one with four sulfurs and one with two bromides.For the complexes cis- [CrX2([14]aneS4)]PF6 no attempt was made to split the sulfur shell to take account of the slightly different distances expected for the Cr]S (trans to X) and Cr]S (trans to S) since X-ray structural studies have shown that the difference is very small (in this case only ca. 0.01 Å). In all cases the EXAFS data gave d(Cr]S) values very similar to those obtained crystallographically for chromium(III)–thioether interactions (ca. 2.4 Å) and significantly longer than d(Cr]Cl) (ca. 2.3 Å). This is consistent with the thioether interaction being rather weak as might be anticipated for such a hard metal–soft ligand combination. The Cr]Br bond lengths of ca.2.45 Å are in accord with the trend expected on the basis of the increased size of bromine over chlorine and also agree very well with d(Cr]Br) derived from the X-ray crystallographic study on cis-[CrBr2([14]aneS4)]PF6 described above. Electronic spectra The UV/VIS spectra were recorded by diffuse reflectance (and also in solution for the soluble species) and the data for all of the new compounds are presented in Table 2. In an Oh environment three spin-allowed d–d bands are predicted for chromium(III) species 4A2g æÆ 4T2g (n1) 4A2g æÆ 4T1g(F) (n2) and 4A2g æÆ 4T1g(P) (n3) of which the latter is rarely observed as it is often obscured by intense charge-transfer bands.26 1642 J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 Table 2 Electronic spectroscopic data (cm21) a for chromium(III) thioether macrocyclic compounds Compound [CrCl3([9]aneS3)] [CrBr3([9]aneS3)] [CrCl3([10]aneS3)] [CrBr3([10]aneS3)] [(CrCl3)2([18]aneS6)] [(CrBr3)2([18]aneS6)] [CrCl2([14]aneS4)]PF6 b [CrBr2([14]aneS4)]PF6 b [CrI2([14]aneS4)]PF6 [CrCl2([16]aneS4)]PF6 b [CrBr2([16]aneS4)]PF6 b [CrI2([16]aneS4)]PF6 Colour Purple Blue-purple Purple Dark purple Pink-purple Blue-purple Blue-green Dark blue Olive green Green Dark green Light green n1 14 450 14 350 14 750 14 140 14 450 14 250 16 500 16 500 16 700 (sh) 15 820 15 510 16 100 n2 20 080 19 230 20 240 19 120 19 530 18 620 22 400 21 550 — 21 790 20 940 — Dq 1 445 1 435 1 473 1 414 1 445 1 425 1 650 1 650 —1 582 1 551 — B 556 463 590 505 516 491 536 485 — 546 554 — a Recorded for solid diluted with BaSO4 by diffuse reflectance except where indicated; sh = shoulder; C = 4.5B.b Recorded in MeNO2 solution. Noticeable splitting of these bands usually occurs upon reducing the symmetry from Oh to D4h (i.e. a trans-L4X2 donor set) whereas reducing the symmetry to C2v (i.e. a cis-L4X2 donor set) usually just results in some broadening of the transitions. 18 Also reducing the symmetry from Oh to C3v (i.e. a fac- L3X3 donor set as in the trithia and binuclear hexathia species) should theoretically result in splitting of the bands although in practice only broadening of the bands is observed usually. Owing to the geometric constraints of the ligands used only the fac isomer is expected in each of the trithia species. The UV/VIS spectra of the chromium(III) thioether species in this work are typical of chromium(III) complexes with an L4Cl2 donor set showing two d–d transitions.The absence of any noticeable splitting in the UV/VIS spectra of [CrX2([14]- aneS4)]PF6 or [CrX2([16]aneS4)]PF6 either in solution or the solid state suggests that these exist as the cis isomers. This has been confirmed for [CrX2([14]aneS4)]1 through single-crystal structure analyses on the chloride and bromide derivatives however in the absence of such data there is some uncertainty over the geometric arrangement (cis vs. trans) in the complexes of [16]aneS4. For each of the chromium(III) compounds Dq is obtained directly from n1 while the Racah parameter (B) can be extracted from the appropriate Tanabe–Sugano diagram.26 It should be noted however that there is a considerable error associated with B of ca. ±50 cm21.From the values of Dq obtained it can be seen that for the neutral chromium(III) species with S3X3 donor sets Dq is smaller than for the species with S4X2 donor sets consistent with the replacement of pdonor halogen ligands with thioether donors (probably weak s donors only in these compounds). Consistent with this Dq is even smaller for the hexachloro species [CrCl6]32 (1318).27 The values of Dq for the thioether compounds are considerably smaller than for other chromium(III) species with harder Nand O-donor ligands e.g. [Cr(H2NCH2CH2NH2)3]31 (Dq = 2180) [Cr(bipy)3]31 (bipy = 2,29-bipyridine) (Dq = 2340) and [Cr(H2O)6]31 (Dq = 1740).27,28 For chromium(III) compounds with other soft donor sets such as phosphines the Dq values generally compare well with those for the thioether species in this work e.g.for [CrCl3{MeC(CH2PPh2)3}] (P3Cl3 donor set) Dq = 1600.3 The values are also very similar to those for the other chromium(III)–thioether species known e.g. [CrCl3- {MeC(CH2SMe)3}] (S3Cl3 donor set) Dq = 1470 cm21.3 These trends are consistent with only weak interactions between the CrIII and the soft thioether functions. For all of the compounds studied B lies in the range 463–590 cm21. These values are rather smaller than those observed for [Cr(H2O)6]31 (B = 710) and [Cr(dmso)6]31 (B = 685 cm21).27 Conclusion These results confirm that despite the anticipated incompatibility between hard chromium(III) centres and soft thioether functions a series of relatively stable mono- and di-nuclear complexes involving S3X3 and S4X2 donor sets has been successfully synthesized adding considerably to the previously very limited range of such compounds known.Chromium K-edge EXAFS studies have proved to be extremely useful providing structural data on the Cr]S and Cr]X bond distances in this unusual series of compounds. The values derived from the EXAFS measurements compare very well with those from X-ray crystallographic studies where such information is available. In particular the Cr]S bond lengths are apparently largely independent of the macrocycle ring size or number of donor atoms available and the Cr]S bond lengths together with the Dq values indicate relatively weak CrIII–S (thioether) interactions in these compounds. Current work investigating the possibility of substituting the halide ligand to generate organometallic chromium–thioether macrocyclic derivatives is underway.Experimental Infrared spectra were measured as KBr or CsI discs or as Nujol mulls between CsI plates using a Perkin-Elmer 983 spectrometer over the range 200–4000 cm21 mass spectra by FAB using 3-nitrobenzyl alcohol as matrix on a VG Analytical 70- 250-SE normal-geometry double-focusing spectrometer or by electrospray using a Hewlett-Packard Series 1050 spectrometer and UV/VIS spectra in solution using 1 cm path length quartz cells or by diffuse reflectance using samples diluted with BaSO4 on a Perkin-Elmer Lambda19 spectrophotometer. Microanalytical data were obtained using a F & M model 185 C H and N analyser. The EXAFS measurements were made at the Daresbury Laboratory operating at 2.0 GeV (ca. 3.2 × 1027 J) with typical currents of 200 mA.Chromium K-edge data were collected on stations 7.1 and 8.1 using a silicon(111) order-sorting monochromator with harmonic rejection achieved by stepping off the peak of the rocking curve by 50% of the full height level. Data were collected in transmission mode from samples diluted with boron nitride and mounted between Sellotape in 1 mm aluminium holders. Diethyl ether was dried over sodium wire. The compounds [CrCl3(thf )3],29 [CrBr3(thf )3] [Cr(thf )6][BF4]3 16 and cis-[CrCl2- ([14]aneS4)]PF6 9 were prepared by the literature methods. Preparations (a) [CrCl3([9]aneS3)]. To a solution of [CrCl3(thf )3] (0.104 g 0.28 mmol) in dry degassed CH2Cl2 (15 cm3) was added [9]aneS3 (0.05 g 0.28 mmol). The resulting purple solution was stirred at room temperature under N2 for 2 h and Et2O was added to afford a purple solid which was filtered off and dried in vacuo.Yield = 0.066 g 70% (Found C 21.5; H 3.7. C6H12Cl3CrS3 requires C 21.3; H 3.5%). IR (CsI disc) 2970w 1445s 1405s 826m 349 (br) m and 293w cm21. J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 1643 (b) [CrBr3([9]aneS3)]. Method as for (a) using [CrBr3(thf )3] (0.101 g 0.20 mmol) and [9]aneS3 (0.036 g 0.20 mmol) giving a blue-purple solid. Yield = 0.059 g 62% (Found C 14.9; H 2.7. C6H12Br3CrS3 requires C 15.3; H 2.6%). IR (Nujol mull) 346m and 324m cm21. (c) [CrCl3([10]aneS3)]. Method as for (a) using [CrCl3(thf )3] (0.108 g 0.29 mmol) and [10]aneS3 (0.056 g 0.29 mmol) giving a purple solid. Yield = 0.077 g 75% (Found C 24.0; H 4.1. C7H14Cl3CrS3 requires C 23.9; H 4.0%). IR (Nujol mull) 359m and 346m cm21.(d) [CrBr3([10]aneS3)]. Method as for (a) using [CrBr3(thf )3] (0.091 g 0.018 mmol) and [10]aneS3 (0.035 g 0.18 mmol) giving a dark purple solid. Yield = 0.037 g 68% (Found C 17.1; H 3.0. C7H14Br3CrS3 requires C 17.3; H 2.9%). IR (Nujol mull) 342w 325m and 300m cm21. (e) [(CrCl3)2(Ï-[18]aneS6)]. Method as for (a) using [CrCl3(thf )3] (0.066 g 0.18 mmol) and [18]aneS6 (0.03 g 0.09 mmol) giving a pink-purple solid. Yield = 0.080 g 66% (Found C 21.6; H 3.5. C12H24Cl6Cr2S6 requires C 21.3; H 3.5%). IR (Nujol mull) 340 (br) m and 298w cm21. ( f ) [(CrBr3)2(Ï-[18]aneS6)]. Method as for (a) using [CrBr3(thf )3] (0.07 g 0.14 mmol) and [18]aneS6 (0.025 g 0.07 mmol) giving a blue-purple solid. Yield = 0.07 g 52% (Found C 15.1; H 2.6. C12H24Br6Cr2S6 requires C 15.3; H 2.5%). IR (Nujol mull) 310m and 301w cm21.(g) [CrBr2([14]aneS4)]PF6. To a solution of [CrBr3(thf )3] (0.12 g 0.24 mmol) in dry degassed MeNO2 (15 cm3) was added TlPF6 (0.085 g 0.24 mmol) and [14]aneS4 (0.065 g 0.24 mmol). After stirring for ca. 12 h the white TlCl precipitate was filtered off leaving a blue-green solution. Addition of Et2O gave a deep blue solid which was filtered off washed with Et2O and dried in vacuo. Yield = 0.06 g 41% (Found C 18.8; H 3.4. C10H20Br2CrF6PS4 requires C 19.2; H 3.2%). Electrospray mass spectrum (MeCN solution) m/z = 480 {calc. for [Cr79Br81Br([14]aneS4)]1 m/z = 480}. IR (Nujol mull) 839vs 557s 346w and 323w cm21. (h) [CrI2([14]aneS4)]BF4. The salt AgBF4 (0.156 g 0.80 mmol) and [CrCl3(thf )3] (0.10 g 0.27 mmol) were stirred in dry thf (25 cm3) for ca. 2 h to give a white AgCl precipitate which was filtered off to leave a pale green solution of [Cr(thf )6][BF4]3.Dry MeNO2 (25 cm3) was then added and the thf removed in vacuo. The compounds [14]aneS4 (0.072 g 0.27 mmol) and NEt4I (0.139 g 0.54 mmol) were added and the deep green reaction mixture stirred for 1 h. The volume was then reduced in vacuo to <3 cm3. Addition of Et2O yielded an olive-green solid which was filtered off and dried. Yield = 0.04 g 22% (Found C 21.1; H 3.9. C10H20BCrF12I2S4 requires C 21.8; H 3.6%). IR (Nujol mull) 1077s 839m 564m and 351w cm21. (i) [CrCl2([16]aneS4)]PF6. As for (g) using [CrCl3(thf )3] (0.06 g 0.16 mmol) TlPF6 (0.056 g 0.16 mmol) and [16]aneS4 (0.048 g 0.016 mmol) giving a light green solid. Yield = 0.03 g 30% (Found C 25.0; H 4.6. C12H24Cl2CrF6PS4 requires C 25.5; H 4.3%).Electrospray mass spectrum (MeCN solution) m/z = 418 {calc. for [Cr35Cl2([16]aneS4)]1 m/z = 418}. IR (Nujol mull) 840vs 558s and 366 (br) w cm21. ( j) [CrBr2([16]aneS4)]PF6. As for (g) using [CrBr3(thf )3] (0.08 g 0.16 mmol) TlPF6 (0.056 g 0.16 mmol) and [16]aneS4 (0.048 g 0.016 mmol) giving a dark green solid. Yield = 0.03 g 29% (Found C 22.4; H 3.9. C12H24Br2CrF6PS4 requires C 22.0; H 3.7%). Electrospray mass spectrum (MeCN solution) m/z = 508 {calc. for [Cr79Br81Br([16]aneS4)]1 m/z = 508}. IR (Nujol mull) 841vs 558s and 302w cm21. (k) [CrI2([16]aneS4)]BF4. Method as for (h) using [Cr(thf )6]- [BF4]3 (0.25 mmol) [16]aneS4 (0.08 g 0.27 mmol) and NEt4I (0.139 g 0.54 mmol) giving a green solid. Yield = 0.03 g 16% (Found C 21.5; H 3.8. C12H24BCrF12I2S4 requires C 20.9; H 3.5%).IR (Nujol mull) 1056s 846m 562m and 359w cm21. EXAFS Refinements Typically two or three data sets were collected for each complex and the analyses were carried out on the averaged spectra. The raw data were background-subtracted using the program PAXAS30 by fitting a sixth- or eighth-order split polynomial to the pre-edge subtracted spectrum between k = 2 and to 13–15 Å21. Curve fitting was carried out using the program EXCURV 92.31 Ground-state potentials of the atoms were calculated using Von Barth theory and phase shifts using Hedin– Lundqvist potentials. Two shells (either 3 S and 3 X or 4 S and 2 X) were fitted in each case. Refinements were also carried out using 6 S or 6 X as well as other combinations and in the case of X = Br the results clearly supported the S3Br3 or S4Br2 donor sets expected.In the case of the chloro derivatives the very similar backscattering from S and Cl made the assignment of the donor set difficult on the basis of the EXAFS data alone although a better fit was obtained using two shells (either 3 S and 3 Cl or 4 S and 2 Cl as appropriate) and in addition the UV/VIS IR and mass spectometric data provide very strong evidence for the donor sets chosen. The distances and Debye– Waller factors were refined for all the shells as well as the Fermi energy difference. No attempt was made to refine the carbons of the ligand backbones since these occur over a range of distances and are not expected to be well defined. Acknowledgements We thank the EPSRC for an Earmarked Studentship (S. J. A. P.) and for funding the X-ray diffractometer and the University of Southampton for support.We also thank the Director of the Synchrotron Radiation Source at Daresbury for the use of the facilities and we are indebted to Dr. W. Levason and Professor J. Evans (University of Southampton) for help in collecting the EXAFS data and the former for microanalytical measurements. References 1 D. A. House and C. S. Garner Transition Met. Chem. 1970 6 59; Comprehensive Coordination Chemistry eds. G. Wilkinson R. D. Gillard and J. A. McCleverty Pergamon Oxford 1987 vol. 3. 2 See for example A. L. Hale W. Levason and F. P. McCullough Inorg. Chem. 1982 21 3570; L. R. Gray A. L. Hale W. Levason F. P. McCullough and M. Webster J. Chem. Soc. Dalton Trans. 1983 2573. 3 L. R. Gray A. L. Hale W. Levason F. P. McCullough and M. Webster J.Chem. Soc. Dalton Trans. 1984 47. 4 A. L. Hale and W. Levason J. Chem. Soc. Dalton Trans. 1983 2569. 5 M. A. Bennett R. J. H. Clark and A. D. J. Goodwin J. Chem. Soc. A 1970 541. 6 R. J. H. Clark and G. Natile Inorg. Chim. Acta 1970 4 533. 7 H.-J. Kuppers and K. Wieghardt Polyhedron 1989 8 1770. 8 G. J. Grant K. E. Grant W. N. Setzer and D. G. VanDerveer Inorg. Chim. Acta 1995 234 35. 9 N. R. Champness S. R. Jacob G. Reid and C. S. Frampton Inorg. Chem. 1995 34 396. 10 A. J. Blake and M. Schröder Adv. Inorg. Chem. 1990 35 1; S. R. Cooper and S. C. Rawle Struct. Bonding (Berlin) 1990 72 1. 11 See for example M. T. Ashby and D. L. Lichtenberger Inorg. Chem. 1985 24 636; D. Sellman and L. Zapf Angew. Chem. Int. Ed. Engl. 1984 23 807; D. Sevdic M. Curic and Lj. Tusak- Bozic Polyhedron 1989 8 505; T.Adachi N. Sasaki T. Ueda M. Kaminaka and T. Yoshida J. Chem. Soc. Chem. Commun. 1989 1320; T. Yoshida T. Adachi T. Ueda M. Kaminaka N. Sasaki T. Higuchi T. Aoshima I. Mega Y. Mizobe and M. Hidai Angew. Chem. Int. Ed. Engl. 1989 28 1040. 12 D. Sellmann and L. Zapf J. Organomet. Chem. 1985 289 57. 1644 J. Chem. Soc. Dalton Trans. 1997 Pages 1639–1644 13 P. K. Baker S. J. Coles M. C. Durranr S. D. Harris D. L. Hughes M. B. Hursthouse and R. L. Richards J. Chem. Soc. Dalton Trans. 1996 4003. 14 G. R. Willey M. T. Lakin and N. W. Alcock J. Chem. Soc. Chem. Commun. 1991 1414. 15 M. C. Durrant S. Davies D. L. Hughes C. Le Floc’h R. L. Richards J. R. Sanders N. R. Champness S. J. Pope and G. Reid Inorg. Chim. Acta 1996 251 13. 16 P. J. Jones A. L. Hale W. Levason and F.P. McCullough Inorg. Chem. 1983 22 2642. 17 J. I. Bruce L. R. Gahan T. W. Hambley and R. Stranger J. Chem. Soc. Chem. Commun. 1993 702. 18 S. Pattanayak D. Kumar Das P. Chakravorty and A. Chakravorty Inorg. Chem. 1995 34 6556. 19 A. J. Blake G. Reid and M. Schröder J. Chem. Soc. Dalton Trans. 1989 1675. 20 A. J. Blake R. O. Gould G. Reid and M. Schröder J. Organomet. Chem. 1988 356 389. 21 T.-F. Lai and C.-K. Poon J. Chem. Soc. Dalton Trans. 1982 1465. 22 SHELXS 86 program for crystal structure solution G. M. Sheldrick Acta Crystallogr. Sect. A 1990 46 467. 23 TEXSAN Crystal Structure Analysis Package Molecular Structure Corporation Houston TX 1992. 24 N. Walker and D. Stuart Acta Crystallogr. Sect. A 1983 39 158. 25 F. A. Cotton S. A. Duraj G. L. Powell and W. J. Roth Inorg. Chim. Acta 1986 113 81. 26 A. P. B. Lever Inorganic Electronic Spectroscopy Elsevier Amsterdam 2nd edn. 1984. 27 L. S. Forster Transition Metal Chemistry Marcel Dekker New York 1969 vol. 5 p. 1. 28 N. Serpone M. A. Jamieson M. S. Henry M. Z. Hoffman F. Bolletta and M. Maestri J. Am. Chem. Soc. 1979 101 2907. 29 W. Herzig and H. H. Zeiss J. Org. Chem. 1958 23 1404. 30 N. Binsted PAXAS Program for the analysis of X-ray absorption spectra University of Southampton 1988. 31 N. Binsted J. W. Campbell S. J. Gurman and P. C. Stephenson EXCURV 92 SERC Daresbury Laboratory 1992. Received 11th December 1996; Paper 6/08332C

ISSN:1477-9226    

DOI:10.1039/a608332c

出版商:RSC    

年代:1997

数据来源: RSC