Halide abstraction reactions of tin(IV) chloride and the group 3 chlorides MCl 3 (M  Sc, Y, La) in thf: crystal and molecular structure of [ScCl 2 (thf) 4 ][SnCl 5 (thf)] Gerald R. Willey*, Timothy J. Woodman and William Errington Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK Summary Direct treatment (1:1) of MCl 3 (M  Sc, Y or La) with SnCl 4 in thf provides colourless compounds of the type ScSnCl 7 (thf) 5 and MSnCl 7 (thf) 6 (M  Y, La), which have been characterised by elemental analysis and spectroscopic studies. An X-ray determination of ScSnCl 7 (thf) 5 reveals an ionic structure comprising individual six-coordinate [ScCl 2 (thf) 4 ] + cations and [SnCl 5 (thf)] ) anions. The cations feature an octahedral metal geometry in which a linear ClAScACl unit is surrounded by an equatorial girdle of four solvent (thf) molecules. Introduction Halide transfer between transition metals in thf solution can lead to the formation of novel salts, e.g. the dimeric cations [V 2 (l-Cl) 3 (thf) 6 ] + (1) and [Mg 2 (l-Cl) 3 (thf) 6 ] + (2) as formed in Reactions 1 and 2. 4VCl 3 thf 3  2Zn !V 2 l-Cl 3 thf 6  2 - Zn 2 l-Cl 2 Cl 4  1 2MgCl 2 (thf) 2 TiCl 4 (thf) 2  !Mg 2 l-Cl 3 (thf) 6 - TiCl 5 (thf) 2 Sobota et al. (3) have made extensive use of tin(IV) chloride as a halide abstraction agent for d-block metal halides, leading to ionic compounds of the type [trans- MCl 2 (thf) 4 ][SnCl 5 (thf)] where M  Ti (4) ,V (5) or Cr (5) ; [Ni 2 (l-Cl) 3 (thf) 6 ][SnCl 5 (thf)] (6) ; and [Mn 4 (l-Cl) 6 (thf) 12 ]- [SnCl 5 (thf) 7 2 . In certain cases, redox chemistry precedes halide transfer, e.g. isolation of [Fe 2 (l-Cl) 3 (thf) 6 ]- [SnCl 5 (thf)] from a 2:1 molar ratio of FeCl 3 :SnCl 2 in thf is seen to involve iron(III) chloride reduction to [FeCl 2 (thf) 1.5 ] (8) before reaction with tin(IV) chloride to facilitate the transfer of halide. Recently we have shown that the acceptor properties of SnCl 4 also embrace halide abstraction from the lanthanides LnCl 3 , with the formation of the salts [LnCl 2 (thf) 5 ][SnCl 5 (thf)] for Ln  Ce, Gd and Yb (9) . Herein we report the reactions of the pre-lanthanide trichlorides MCl 3 (M  Sc, Y, La) with SnCl 4 in thf, and the subsequent crystal structure determination of [ScCl 2 (thf) 4 ][SnCl 5 (thf)]. Experimental All manipulations were performed under a N 2 and/or Ar atmosphere using standard Schlenk, vacuum-line and glove box techniques. Thf was pre-dried over Na wire and then freshly distilled over K prior to use. Hexane was dried over CaH 2 and also distilled from K as required. The ScCl 3 (thf) 3 , YCl 3 (thf) 3.5 and LaCl 3 (thf) 2 were prepared from the commercially available hydrates (Aldrich) by heating at re¯ux with SOCl 2 in the presence of an excess of thf (10) . Tin(IV) chloride was purchased from Aldrich and used without further puri®cation. The i.r. spectra were recorded as Nujol mulls sandwiched between CsI plates using a Perkin-Elmer 580B instru- ment and microanalyses were carried out using a Lee- man Labs Inc., CE 440 elemental (C, H, N) analyser. Preparation of the complexes [ScCl 2 (thf) 4 ][SnCl 5 (thf)] ScCl 3 (thf) 3 (0.41 g, 1.12 mmol) was dissolved in THF (40 cm 3 ). To this was added a solution of tin(IV) chlo- ride (0.29 g, 1.12 mmol, 0.13 cm 3 ) in thf (20 cm 3 ). The initial clear solution, which became cloudy over 15 min, was then heated at re¯ux for 6 h. The solution was ®l- tered whilst still hot, and then cooled in ice to 0 °C. This treatment produced a large amount of white precipitate, which was collected by ®ltration, washed with hexane (3 ´ 20 cm 3 ) and then pumped in vacuo for 2 h. The title product was obtained as a white microcrystalline solid. Yield: 0.73 g, 82%. Crystals suitable for X-ray analysis were obtained by slow cooling of a hot, saturated thf solution. (Found: C, 31.34; H, 5.26; C 20 H 40 O 5 Cl 7 ScSn calcd.: C, 31.10; H, 5.22%.) I.r.:  m max =cm 1 (Nujol) 1317w, 1297w, 1246w, 1176w, 1040m, 997s [m as (COC)], 954m, 924m, 834s [m s (COC)], 679m, 576w, 378s [m(ScCl)], 325s, 295s [m(SnCl)]. [YbCl 2 (thf) 5 ][SnCl 5 (thf)] A mixture of YCl 3 (thf) 3.5 (0.50 g, 1.12 mmol) and tin (IV) chloride (0.29 g, 1.11 mmol, 0.13 cm 3 ) in THF (30 cm 3 ) was heated at re¯ux for 6 h. The clear solution was ®l- tered whilst still warm, and then allowed to cool to 0 °C. A large amount of white precipitate formed and this was isolated via ®ltration, washed with hexane (3 ´ 25 cm 3 ) and then pumped to dryness in vacuo. The product was obtained as a white microcrystalline solid. Yield: 0.74 g, 75%. (Found: C, 32.56; H, 5.27; C 24 H 48 O 6 Cl 7 YSn calcd.: C, 32.45; H, 5.45%.) I.r.  m max =cm 1 (Nujol) 1315w, 1298w, 1246w, 1178w, 1039m, 1006s [m as (COC)], 954m, 920m, 834s [m s (COC)] 671m, 579w, 350s, 320s, 300s, 275s, 240s [m(MCl) M  Y and Sn]. [LaCl 2 (thf) 5 ][SnCl 5 (thf)] A solution containing LaCl 3 (thf) 2 (0.50 g, 1.28 mmol) and tin(IV) chloride (0.33 g, 1.28 mmol, 0.15 cm 3 ) and THF (40 cm 3 ) was heated at re¯ux for 6 h. The clear solution was ®ltered whilst still warm, and then allowed to cool to 0 °C. A large amount of white precipitate formed and this was isolated via ®ltration, washed with 0340±4285 Ó 1998 Chapman & Hall Transition Met. Chem., 23, 387±390 (1998) [ScCl 2 (thf) 4 ][SnCl 5 (thf)] structure 387 * Author to whom all correspondence should be directed.