TETRAHYDROFURAN (THF) SOLVATES OF TIN(IV) HALIDES: CRYSTAL STRUCTURES ÖF TRANS-SnX4(THF)2 WHERE X =...

TETRAHYDROFURAN (ΤΗF) SOLVATES OF TIN (IV) HALIDES: CRYSTAL STRUCTURES OF TRANS-SnX 4 (THF) 2 WHERE X = CI, Br.

MOLECULAR MODELLING OF THE CIS/TRANS ISOMERS OF SnX 4 (THF) 2

Gerald R. Willey*, Timothy J. Woodman, Robert J. Deeth* and William Errington

Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK

Abstract. From studies of the SnX4-thf reaction system (thf = tetrahydrofuran; X = F, CI, Br, I) we

have established adduct formation, SnX4(thf)2 for X = CI (I) and Br (II) but recovery of unchanged starting materials for X = F and I. X-ray crystallography confirms a six coordinate structure with regular octahedral metal geometry for both (I) and (II) with the two solvent (thf) molecules in a mutually frans-arrangement in each case. Modelling studies of the cis-/ trans- isomers of SnX4(thf)2 where X = CI, Br and of SnCI4(H20)2 have been carried out and comparisons drawn with the observed structural chemistry of these systems.

Introduction. The chemistry of tin (IV) halides as reference Lewis acids is dominated by adduct

formation of the type SnX4L2 where X = halogen, L = monodentate involving oxygen- , 1

ni t rogen-,2 phosphorus-3 and, to a lesser extent, sulphur-4 and se len ium- 5 donor l igands. Perhaps the major point of interest in these bis adducts is the question of cis-ltrans- isomerism in the resulting metal geometries. A search of the Cambridge Crystallographic database6

reveals 36 examples divided as trans (17) and c/'s (19); Table 1 provides prominent examples of SnX4L2 systems.

Since, surprisingly, tetrahydrofuran solvates of the tin (IV) halides have not been structurally characterised, we have investigated the reactions of SnX4 (X = F, CI, Br, I) with this familiar O-donor solvent. As a complimentary approach we have carried out molecular modelling studies of viable structures and herein include some general comments on the existence of cis-/trans- isomers of SnX4(thf)2.

Materials and Methods. All manipulations were performed under a dinitrogen and/or argon atmosphere using

standard Schlenk, vacuum- l ine and glove box techniques. Tetrahydrofuran was pre-dried over sodium wire and then freshly distilled over potassium prior to use. Hexane was pre-dried over CaH2 and also distilled from potassium. The tin (IV) halides were purchased from Aldrich Chemical Co. and used without further purification. The IR spectra were recorded as Nujol mulls sandwiched between Csl plates using a Perkin-Elmer 580B instrument and e lementa l analyses were carried out using a Leeman Labs Inc. CE 440 elemental (C, Η, N) analyser.

SnF4. Tin (IV) fluoride (1.00 g, 5.14 mmol) was added to tetrahydrofuran (50 cm3) and the

mixture stirred at 70 °C for 5 hours. The resulting solid obtained by filtration was washed with hexane (2x20 cm3) and then pumped to dryness in vacuo. The IR spectrum confirmed the absence of coordinated thf and a combustion analysis confirmed that the starting tetrafluoride had been recovered unchanged. Calc. Sn 60.97 %; Found: Sn 60.24 %.

SnCI4(thf)2 (I). SnCI4 (2.02 g, 7.75 mmol, 0.90 cm3) was added dropwise to tetrahydrofuran (50 cm·3)

to provide a cloudy solution and a small amount of a white precipitate. The reaction mixture was stirred for 2 hours at room temperature, then heated to 70 °C. The solution was f i l tered whilst still hot, and then cooled to 0 °C to provide colourless oblong crystals. These were isolated by filtration, washed with hexane (3x20 cm3) and pumped to dryness in vacuo. Y ie ld 1.21 g, 39 %.

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Vol. 21, No. 10, 1998 Tetrahydrofuran(THF) Solvates ofTin(IV) Halides: Crystal Structures

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Gerald R. Willey et al. Main Group Metal Chemistry

Found: C, 23.92; Η, 4.03 %. Calculated for C 8H 1 60 2Cl4Sn: C, 23.74; H, 3.98 % IR :V m a x / cm- 1 (Nujol): 1250w, 1171w, 1040w, 1002s vas(COC), 919m, 833s vs(COC), 680w, 350m br v(SnCt)

SnBr4(thf)2 (II). SnBr4 (2.21 g, 5.04 mmol) was added to tetrahydrofuran (40 cm3) and the mixture

warmed for 2 hours at 70 °C. The resulting slightly cloudy solution was filtered whilst still hot, and the filtrate was cooled to 0 °C. The pale green oblong crystals which deposited were washed with hexane (3x20 cm3) and pumped to dryness in vacuo. Yield 1.32 g, 45 %. Found: C, 16.52; H, 2.71 %. Calculated for C 8 H 1 6 0 2 Br 4 Sn: C, 16.50; H, 2.77 %. IR: Vmax/cm-1 (Nujol): 1299m, 1170m, 1039m, 1001s vas(COC), 918m, 828s vs(COC), 676m, 240m and 220m v(SnBr)

Snl4 (III). Snl4 (1.25 g, 2.00 mmol) was added to tetrahydrofuran (30 cm3) and the mixture

heated to 70 °C. The resulting solution was filtered rapidly and on cooling to room temperature provided a crop of orange-red cuboid crystals. Identification of this product as the starting tetraiodide was obtained by an X-ray (diffraction) structure determination.

X-ray crystallography. Crystals of the title compounds were placed under a film of dry oil in a nitrogen-f i l led

glove-box, allowing for scrutiny of the crystals under a microscope. The most suitable crystals were mounted onto fibres, and immediately placed in a nitrogen cryostream.

Crystal data and details of structure refinement for compounds (I), (II) and (III) are given in Table 2. Data were collected using a Siemens SMART CCD area-detector diffractometer. A full hemisphere of reciprocal space was scanned by a combination of three sets of exposures; each set had a different φ angle for the crystal and each exposure of 10 s covered 0.3 0 in ω. The crystal to detector distance was 5.01 cm. Crystal decay was monitored by repeating the initial frames at the end of the data collection and analyzing the duplicate reflections; in all cases the decay was negligible. A mul t i -scan absorption correction was applied using SADABS.16 Each structure was solved by direct methods using SHELXTL-PC 1 7 and refined by full matrix least-squares on F2 for all data using SHELXL-97. Hydrogen atoms were added at calculated positions and refined using a riding model . Anisotropic temperature factors were used for all non-H atoms; Η-atoms were given isotropic temperature factors equal to 1.2 times the equivalent isotropic displacement parameter of the atom to which the Η-a tom is attached.

Computational details. Molecular structures and heats of formation were computed at the semi-empir ical

molecular orbital level using the MOPAC6 program.19 Both PM3 and MNDO Hamil tonians were considered and the PRECISE keyword was specified throughout. Ecl ipsed configurations of the tetrahydrofuran ligands in SnX4(thf)2 were enforced by constraining the C-O-Sn-C' dihedral angles to zero degrees. (C' is the carbon atom next to the oxygen of the other thf group.)

Results and Discussion. Treatment of SnX4 (X = F, CI, Br, I) with an excess of tetrahydrofuran, involv ing

heating at 70 °C over a period of several hours, provided the following results: For X = F there is no adduct formation, under these experimental conditions, and the

parent halide is recovered unchanged. There are no literature reports of structurally characterised SnF4L2 systems, and only one featuring a c/s-bidentate ligand i.e., SnF4(2,2'-bipyridyl).20 An early report by Wilkins et al21 provides infra-red data for SnF4L2 complexes with L (monodentate) = pyridine, tetrahydrofuran, pyr id ine-N-oxide and tr iphenylphosphine oxide and SnF4B complexes where Β (bidentate) = 2,2'—bipyridyl, NNN'N'-tetramethylethylenediamine and dme. For SnF4(thf)2 a fra/is-octahedral structure was proposed on the evidence of a single v(Sn-F) halide stretching band at 600 cm'1. A later report by Tudela and Rey22 describes the preparation of this bis-adduct following prolonged stirring of SnF4(MeCN)2 with an excess of thf with, again, a proposed trans-structure based on




infra-red and Mössbauer spectroscopic data. Equally no adduct formation was observed with X = I under these experimental conditions. The deep orange-red tetrahydrofuran solution provided glistening cuboid crystals of unreacted Snl4. A previous X-ray (diffraction) study (1955)23 revealed discrete tetrahedra of Snl4 in a cubic unit cell, but with only poor refinement. Our redetermination at 180 Κ shows uniform agreement with this previous study, but with excellent refinement viz., R1 = 0.023, wR2 = 0.051. As before the unit cell is cub ic , in space group Pa3. The four Sn - I bond lengths are 2.6585(5), 2.6651(2) (x3) A and the individual tetraheda are almost ideal, with l - S n - l angles in the narrow range 109.166(9)-109.775(9)°.

Table 2. Crystal data and structure refinement for compounds (I), (II) and (III).

Compound (1) (ID (III)

Formula C8Hi602Cl4Sn C8Hi602Br4Sn SnU Μ 404.70 582.54 626.29 Crystal system Tr ic l in ic Tr ic l in ic Cubic Space Group Ρ Γ Ρ Γ Pa3 a/A 7.0314(5) 7.2641(5) 12.1697(2) b/k 7.3870(6) 7.5049(5) 12.1697(2) c/A 7.7537(6) 7.9810(6) 12.1697(2) α 1° 86.917(1) 84.698(2) 90.00 β/° 69.287(1) 68.749(2) 90.00 γ / Ο 68.874(2) 69.909(2) 90.00 V/A3 350.13(5) 380.58(5) 1802.35(5) Τ/Κ 180(2)

ι 180(2) ι

180(2) g

λ/Α 0.71073 0.71073 0.71073 p(calcd.)/Mg/m3 1.919 2.542 4.616 μ/mm"1 2.567 12.160 16.436 hkl ranges -7, 9; -9, 8; -10, 10 -9, 6; -9, 9; -10,10 -16,16; -15,15; -15,12 Number of data 1958 2033 10164 co l lec ted Independent 1375 (Rint = 0.015) 1354 (Rint = 0.045) 749 (Rint = 0.032) reflections Transmission 0.694, 0.547 0.694, 0.187 0.139, 0.072 coeff ic ients R(F) Π > 2σ(Ι)] 0.029 0.030 0.023 wR(F0 (all data) 0.075 0.080 0.051 Goodness of fit on F2 1.082 1.072 1.136 Peak diff. & hole/eA3 0.608, -0.879 0.813, -1.326 0.666, -0.628 Data, restraints, 1375, 0, 70 1354, 0, 71 749, 0, 17 parameters Extinction coefficient N/A N/A 0.00102(4) Crystal size/mm 0.20, 0.14, 0.12 0.30, 0.15, 0.10 0.24, 0.20, 0.20

The products obtained for X = CI (colourless oblong crystals) and X = Br (green oblong crystals) have been identified as the 1:2 adducts. These are extremely moisture-sensitive; previous experience shows the hydrolysis reaction of SnCU in thf solution with just the merest trace of water present results in the formation of the dimeric complex [Sn2CI6^-OH)2(thf)2]-2thf.24,25 The structures of SnX4(thf)2, for X = CI (I), and X = Br (II), confirm six coordinate Sn (IV) centres with a planar surround of four halogen atoms and two mutual ly trans tetrahydrofuran molecules. See Fig. 1 for X = CI. Selected bond lengths and angles for (I) and (II) are listed in Table 3.

Both (I) and (II) exhibit an extremely regular octahedral metal geometry; the O-Sn-O linkages are linear and the interligand angles around the metal are close to the ideal e.g., for (I) Cl-Sn-CI 89.90(3)-90.10(3) O-Sn-CI 89.33(7)-90.67(7) for (II) Br-Sn-Br 89.89(2)-90.11(2) O-Sn-Br 89.43(9)-90.57(9)




Table 3. Selected bond lengths and angles for compounds (I) and (II).

Compound (I): Sn(1)-0(1)#1 2.166(2) Sn(1)-0(1) 2.166(2) Sn(1)-CI(2)#1 2.3735(9) Sn(1)-CI(2) 2.3735(9) Sn(1)-CI(1) 2.3828(8) Sn(1)-CI(1)#1 2.3829(8) 0(1)#1-Sn(1)-0(1) 180.0 0(1)-Sn(1)-CI(1) 90.67(7) 0(1)-Sn(1)-CI(2)#1 90.09(8) 0(1)#1-Sn(1)-CI(2) 90.09(8) 0(1)-Sn(1)-CI(2) 89.91(8)

Symmetry transformations used to generate equivalent atoms: #1 -x+1, -y+1, -z+1 Compound (II):

Sn(1)-0(1) 2.200(3) Sn(1)-0(1)#1 2.200(3) Sn(1)-Br(2) 2.5307(5) Sn(1)-Br(2)#1 2.5307(5) Sn(1)-Br(1)#1 2.5427(5) Sn(1)-Br(1) 2.5428(5) 0(1)-Sn(1)-0(1)#1 180.0 0(1)-Sn(1)-Br(2) 89.95(10) 0(1)-Sn(1)-Br(2)#1 90.05(10) 0(1)-Sn(1)-Br(1)#1 89.43(9) 0(1)#1-Sn(1)-Br(1)#1 90.57(9) Br(2)-Sn(1)-Br(1)#1 89.89(2) 0(1)-Sn(1)-Br(1) 90.57(9) Br(2)-Sn(1)-Br(1) 90.11(2)

Symmetry transformations used to generate equivalent atoms: #1 -x+1, -y+1, -z+1

The metal-ligand (thf) bond distances show some variation with compound (I) Sn-0 2.166(2) A < Compound (II) S n - 0 2.200(3) A as a reflection of the relative acceptor order SnCI4 > SnBr4. Comparisons of Sn-CI bond distances for similar systems show little variation, irregardless of the ligand. (See Table 1). For example frans-SnCI4(C6Hi-|OH)2-2C6HiiOH7

2.367(1)-2.387(1) A and fra/7S-SnCI4(H20)2- 15-crown-51 0 2.364(2)-2.391(2) A compare very well with 2.3735(9)-2.3828(8) A in (I). Even for cis octahedral systems there is not a great deal of difference, e.g., c/s-SnCI4(H20)2-18-crown-6-2H208 2.37(1)-2.40(1) A and cis-SnCI4(C2H6SO)2

1<a> 2.369(3)-2.406(3) A. Direct comparisons can be made with other Sn(IV)chloride-thf systems e.g., [Sn2CI5(H-OH)2(thf)2]-2thf Sn-Ow 2.206(5) A, mean Sn-CI 2.356(3) A24, and the six coordinate anion [SnCI5(thf)]", Sn-0 2.69(8) A mean Sn-CI




2.399(4) A26 and Sn-0 2.276(7) A, mean Sn-CI 2.399(2) A.27 In a similar fashion there is also precious little variation in Sn-Br bond distances. (See Table 1). Typically frans-SnBr4(0=PPh3)212 mean 2.557(2) A and cis-SnBr4(0=SMe2)2

14 2.531 (3)-2.549(4) A, compare favourably with the range 2.5367(5)-2.5428(5) A found in (II).

Fig. 2. Calculated structure using the PM3 Hamiltonian of SnCI4(thf)2 (I) starting from a trans arrangement.

For SnX4L2 systems in general, Kepert28 has shown that there is no great preference for either the cis- or trans-isomer unless there is a large difference in bond lengths Sn-X/Sn-L when the latter is preferred. There are several examples where both arrangements have been crystallographically characterised e.g., c/s-SnBr4(OPPh3)2

12 and trans-SnBr4(OPPh3)2,13 and one example where the two isomers have been found in the same crystal domain e.g. for SnBr4(SMe2)24(b) there are two [c/s-SnBr„(SMe2)2] molecules and one [trans-S η Β r4(S Μ e2)2] molecule located in the unit cell. Solvent effects have been shown to be important in the isolation of particular adducts; both cis and trans forms of SnCI4(tht)2 (tht = tetrahydrothiophen) have been prepared, the cis from dichloromethane and the trans from n-pentane. The implication is that solvent polarity can influence adduct formation, with cis isomers favoured by a more polar media. Interestingly it has been shown that adducts can undergo isomerisation in the solid state, e.g., SnX4L2 for X = CI, L = dmf (dimethylformamide), dma (dimethylacetamide), dmso (dimethylsulphoxide) and for X = Br with L = dmf or dma were all obtained from solution as the cis isomer, and converted to the trans form by heating.29 Clearly a number of competing factors are present. The elegant work of Ruzicka and Merbach30·3 ' on the comparative stabilities of cis and trans isomers in solution is instructive. Using NMR integrations to provide a ratio of trans to cis species in solution ( K j S 0 ) allows the relative stabilities to be probed (Kiso is defined as [trans]/[cis]). The isomerisation constant, K j S 0 is shown to be largely independent of temperature, and hence Δ Η isomerisation must be small. However K j S 0 varies strongly with changes in solvent polarity, so that trans isomers are preferred in weakly polar solvents, and, as stated above, cis are favoured for polar media. Arguments used to explain the isolation of one isomer over the other have typically been based upon solid adducts but this is clearly unsatisfactory since many systems show the co-existence of both forms in the solid state. Zahrobsky32 has employed a stereochemical model based on nonbonded intramolecular interactions to show that irrespective of the relative solid angles of the ligands in a MA4B2 complex, the cis isomer will always be



Gerald R. Willeyetal. Main Group Metal Chemistry

favoured. This is the case for SnX4L2 ligands, provided that the ligand does not spread out the solid angle of the donor atom.

Further insights can be obtained from the MO calculations. However, the method must first be validated. Accordingly, the structure of SnCI4(thf)2 was optimised using the PM3 Hamiltonian. Starting from the X-ray crystal structure coordinates, the system spontaneously separated into tetrahedral SnCI4 and two effectively isolated thf moieties as shown in Fig. 2. This unexpected result is apparently due to the inadequate parameterisation of Sn within the PM3 method since a stable, trans octahedral geometry was obtained using the older MNDO method. However, even for MNDO, the lowest energy structure has the thf planes staggered both with respect to each other and with repect to the chlorides. Moreover, there is a pronounced D 2 d distortion of the SnCI4 plane (Fig. 3a). In the structure derived from the X-ray analysis, the SnCI4 is almost perfectly planar and the thf groups are mutually eclipsed. A calculation of the vibrational frequencies confirmed that the MNDO structure was a true local minimum. However, by constraining the thf ligands to be eclipsed, the SnCI4 unit became planar while the heat of formation increased by less than 3 kcal mol"1 (Fig. 3b). This is of the order of crystal packing forces and it could be speculated that these are responsible for the crystallographically observed arrangement of thf ligands. Alternatively, there may be a residual error for the MNDO Sn parameters which artificially favours the staggered conformation. Some support for this comes from the fact that the computed Sn-0 distances are around 0.2 A longer than observed. In either case, a trans geometry is predicted to be stable. An MNDO optimisation of a cis complex resulted in the formation of isolated SnCI4

Fig.3. Calculated structures using the MNDO Hamiltonian of trans-SnCI4(thf)2. a) no constraints; b) thf ligands forced to be mutually eclipsed.

The results for SnBr4(thf)2 are very similar to those of the chloride analogue. The staggered arrangement of trans thf ligands is more stable by about 3 kcal moM than the eclipsed form and the cis geometry optimisation dissociates to isolated species. On the other hand, not even a stable trans geometry was found for Snl4(thf)2. Hence, the MNDO calculations correlate very well with experiment and predict that SnCI4(thf)2 and SnBr4(thf)2 should form stable trans complexes while Snl4(thf)2 should not and that none of the complexes will form cis species. As a final check, the structures and relative energies of SnCI4(H20)2 were computed. Both cis and trans forms have been characterised experimentally (see Table 1) and MNDO calculations also locate cis and trans structures (Fig. 4). In agreement with experiment which implies the energies of cis and trans forms must be very similar, the calculated heats of formation differ by less than 0.4 kcal mol"1.




In summary, the MNDO results correlate very well with experiment for these systems. We can thus use the model to probe the factors that determine the balance between c/'s and trans structures.

The simplest interpretation focuses on the energy required to distort the SnX4 tetrahedron. For a trans geometry, the tetrahedron must be flattened to a square plane. MNDO estimates for this process are 45, 45 and 59 kcal moM for SnCI4, SnBr4 and Snl4 respectively. The energy to overcome this barrier is supplied by the Sn-thf interaction. Evidently, the latter lies between 45 and 59 kcal moH since it is strong enough to give trans complexes for X = CI and Br but not enough for X = I. This range can be further refined. It takes about 6 kcal moM more energy to distort a planar SnX4 moiety to the 'see-saw' geometry required for the (ideal) c/'s complex. Thus, the total Sn-thf interaction energy is predicted to be no more than 6 kcal mol"'' greater than the lower limit of 45 kcal mol"1 otherwise the calculations would also predict stable c/'s geometries for the chloride and bromide complexes. The relatively small energy difference between the planar and see-saw arrangements of the SnX4 species is consistent with the frequent observation of both isomers. The trans species should alway be favoured but, given a sufficiently strong Sn-L interaction, the c/'s isomer is also accessible. Note that this interaction will arise from a combination of attractive Sn-L bonding plus non-bonding interactions between L and X, the van der Waals portion of which will usually be repulsive while the electrostatic part may well be attractive. Despite the approximate nature of semi empirical MO theory, the MNDO method describes

(a) (b) Fig. 4. Calculated structures using the MNDO Hamiltonian of SnCI4(H20)2·

a) trans structure; b) c/'s structure.

Acknowledgement. We thank the University of Warwick for a postgraduate scholarship (to T.J.W.) and for

computer hardware. We acknowledge the contributions from Siemens pic, the EPSRC and the University of Warwick for funding of the X-ray facilities. We are grateful to a referee for helpful comments several of which have been incorporated into the text.

i f 6 (a) J.M. Kisenyi, G.R. Willey and M.G.B. Drew, Acta Crystallogr., Sect. C, 1985, 41, 700; (b) S. Calogero, U. Russo, G. Valle, P.W.C. Barnard and J.D. Donaldson, Inorg. Chim. Acta, 1982, 59, 111; (c) D. Tudela, J.D. Tornero, A. Monge and A.J. Sanchez-Herencia, Inorg. Chem., 1993, 32, 3928.

2) H.-D. Hausen, W. Schwartz, G. Rajca and J. Weidlein, Ζ. Naturforsch., Teil Β, 1986, 41, 1223; Τ. Chivers, S.W. Liblong, J.F. Richardson and T. Ziegler, Inorg. Chem., 1988, 27, 860; M. Webster and H.E. Blaydon, J. Chem. Soc. (A), 1969, 2443.

3) N.C. Norman and N.L. Pickett, Coord. Chem. Rev., 1995, 145, 27. 4) (a) S.E. Dann, A.R.J. Genge, W. Levason and G. Reid, J. Chem. Soc., Dalton Trans.,

1996, 4471; (b) N. Bricklebank, S.M. Godfrey, C.A. McAuliffe and R.G. Prichard, J. Chem. Soc., Chem. Commun., 1994, 695.

5) (a) S.E. Dann, A.R.J. Genge, W. Levason and G. Reid, J. Chem. Soc., Dalton Trans., 1997, 2207; (b) S.J. Ruzicka, C.M.P. Favez and A.E. Merbach, Inorg. Chim. Acta, 1977, 23, 239; (c) E.W. Abel, S.K. Bhargava, K.G. Orreil and V. Sik, Inorg. Chim. Acta, 1981, 49, 25.

6) We wish to acknowledge the use of the EPSRC's chemical database service at Daresbury Laboratory (a) for access to the Cambridge Structural database03'.




(a) D.A. Fletcher, R.F. McMeeking and D. Parkin, J. Chem. Inf. Comput. Sei., 1996, 36, 746-749 (b) F.H. Allen and 0 . Kennard, Chem. Des. Autom. News, 1993, 8, 3 1 -37.

7) F. Fournet and F. Theobald, Inorg. Chim. Acta, 1981, 52, 15. 8) G. Valle, A. Cassol and U. Russo, Inorg. Chim. Acta, 1984, 82, 81. 9) P.A. Cusack, B.N. Patel, P.J. Smith, D.W. Allen and I.W. Nowell, J. Chem. Soc., Dalton

Trans., 1984, 1239. 10) E. Hough, D.G. Nicholson and A.K. Vasudevan, J. Chem. Soc., Dalton Trans., 1986,

2335. 11) M.M. Olmstead, K.A. Williams and W.K. Musher, J. Am. Chem. Soc., 1982, 104, 5567. 12) A.I. Tursina, A.V. Yatsenko, S.V. Medvedev, V.V. Chernyshev and L.A. Aslanov, Zh.

Struct. Khim., 1986, 27, 157. 13) D. Tudela, J.D. Tornero, A. Monge, A.J. Sanchez-Herencia, Inorg. Chem., 1993, 32,

3928. 14) M. Gregorkiewitz and D. Tudela, Acta Crystallogr., Sect. C, 1990, 46, 210. 15) A.V. Jatsenko, S.V. Medvedev, K.A. Paseshnitchenko and L.A. Aslanov, J. Organomet.

Chem., 1995, 284, 181. 16) G.M. Sheldrick, SADABS, Empirical Absorption Corrections Program, University of

Göttingen, Germany, 1997. 17) Siemens, SHELXTL-PC Version 5.0 Reference Manual. Siemens Industrial Au tom. ,

Inc., Analytical Instrumentation, Madison, Wisconsin, USA, 1994. 18) G.M. Sheldrick, SHELXL-97 , Program for Crystal Structure Refinement, University of

Göttingen, Germany, 1997. 19) M.B. Coolidge and J.P. Steward, MOOAC 6 Quantum Chem. Program Exch. Bull., 455. 20) A.D. Ad ley, P.H. Bird, A.R. Fräser, M. Onyszchuk, Inorg. Chem., 1972, 11, 1402. 21) C.J. Wilkins and H.M. Haendler, J. Chem. Soc., 1965, 3174. 22) D. Tudela and F. Rey, Z. anorg. allg. Chem., 1989, 575, 202. 23) F. Melier and I. Fankuchen, Acta Crystallogr., 1955, 8, 343. 24) Z. Janas, P. Sobota and T. Lis, J. Chem. Soc., Dalton Trans., 1991, 2429. 25) S.D. Chappel, L.M. Engelhardt, C.L. Raston and A.H. White, Aust. J. Chem., 1988, 41,

1123. 26) Z. Janas, P. Sobota and T. Lis, Polyhedron, 1988, 7, 2655. 27) G.R. Willey, T.J. Woodman, D.J. Carpenter and W. Errington, J. Chem. Soc., Dalton

Trans., 1997, 2677. 28) D.L. Kepert in "Comprehensive Coordination Chemistry" Edit: G. Wilkinson, R.D.

Gillard and J.A. McCleverty, Pergamon Press, UK. 1987, Vol. 1, Ch. 2, ρ 31. 29) C.U. Davanzo and Y. Gushikem, J. Chem. Soc., Dalton Trans., 1981, 843. 30) S.J. Ruzicka and A.E. Merbach, Inorg. Chim. Acta, 1976, 20, 221. 31) S.J. Ruzicka and A.E. Merbach, Inorg. Chim. Acta, 1977, 22, 191. 32) R.F. Zahrobsky, J. Am. Chem. Soc., 1971, 93, 3313.

Received: April 28, 1998 - Accepted: May 19, 1998 -Accepted in revised camera-ready format: May 29, 1998

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Brought to you by | Heinrich Heine Universität DüsseldorfAuthenticated | 134.99.128.41


TETRAHYDROFURAN (THF) SOLVATES OF TIN(IV) HALIDES: CRYSTAL STRUCTURES ÖF TRANS-SnX4(THF)2 WHERE X =...

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