Chemistry of o-xylenediyl-metal complexes: Part 5. Silicon and tin metallacycles derived from o-C6H4([C with combining overline]HR)2(R = H or SiMe3)

Michael F. Lappert, Wing Por Leung, Colin L. Raston, Brian W. Skelton, Allan H. White

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Treatment of SnCl2Ph2 with [Mg(LL)(thf)] 6 or [Li(tmen)]2[o-C6H4{CH(SiMe3)} 2] 7 in OEt2 yields the stannacycle [Sn(LL)Ph2] 1 or [Sn(L′L′-meso)Ph2] 2 {(LL)2- = o-C6H4(C̄H2)2, (L′L′)2- = o-C6H4[C̄H(SiMe3)]2, thf = tetrahydrofuran, tmen = Me2N[CH2]2NMe2}. Likewise, SnCl4 with 6 or 7 at 30 °C in OEt2 affords exclusively the stannaspirobicycle [Sn(LL)2] 3 or [Sn(L′L′-meso)2] 4; by contrast SnCl4 with 7 at -78 °C gives, together with 4 (52%), the yellow, diamagnetic tin(II) metallacycle [{Sn(L′L′-meso)}4](Sn-Sn) 5 (14%). Compound 5 is more conveniently prepared by treating Sn(OC6H2But2-2,6-Me-4)2 with 7; it is tetrameric in the solid and in solution, but monomeric in the gas phase and has a low first ionisation energy (7.6 eV). The compound [Si(LL)Me2] 8 is obtained by an in situ Grignard reaction from SiCl2Me2, o-C6H4(CH2Cl)2 and Mg in thf, while [Si(L′L′-meso)Me2] 9 is prepared from SiCl2Me2 and 7. Each of the metallacycles derived from the ligand (L′L′)2- was obtained stereospecifically as the meso diastereoisomer. X-Ray structure determinations of complexes 1-5 have been performed. The α,α′-unsubstituted metallacycles have shorter 〈Sn-Cα〉 distances (2.144 in 1, 2.147 Å in 3) than the corresponding α,α′-bis(trimethylsilyl) derivatives (2.166 in 2, 2.174 Å in 4). The C6CαCα′ o-xylenediyl plane is folded relative to the MCαCα′ plane, the 'fold angle' θ being 8.5 (1), 19.8 (2), 0.8 and 11.9 (3), 24.1 and 23.0 (4) and 20.8 ° (5). The larger θ values for the SnIVL′L′) complexes 2 and 4 than for the their SnIV(LL) counterparts 1 and 3 (as for comparable Sn-Cα distances) is attributable to greater interligand strain and crowding around the metal centre in 2 and 4. Molecules of 5 have 4 symmetry, with Sn-Sn 2.852(3), Sn-Cα 2.15(3) and Sn-Cα′ 2.09(4) Å.

Original languageEnglish
Pages (from-to)775-785
Number of pages11
JournalJournal of the Chemical Society, Dalton Transactions
Issue number5
DOIs
Publication statusPublished - Mar 1992
Externally publishedYes

Fingerprint Dive into the research topics of 'Chemistry of o-xylenediyl-metal complexes: Part 5. Silicon and tin metallacycles derived from o-C6H4([C with combining overline]HR)2(R = H or SiMe3)'. Together they form a unique fingerprint.

  • Cite this