Subvalent Group 14 metal compounds. Part 16. Synthesis, crystal structure and characterisation of some β-functionalised-alkyltin(II) complexes, SnR(X){R = C5H4N[C(SiMe3)2]-2; X = R, Cl or N(SiMe3)2}
- 1 January 1993
- journal article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 17,p. 2653-2663
- https://doi.org/10.1039/dt9930002653
Abstract
Crystalline monomeric alkyltin(II) compounds were prepared using the β-N-functionalised ligand 2-pyridylbis(trimethylsilyl)methyl, C5H4N[C(SiMe3)2]-2 (R): (a) SnR21 from (LiR)2 and SnCl2 or Sn(OC6H3But 2-2,6)2(b) SnR(Cl)2 from SnCl2 and SnR2 or ½(LiR)2; and (c) SnR[N(SiMe3)2]3 from Sn[N(SiMe3)2]2 and ½(LiR)2. Single-crystal X-ray diffraction data showed that in each of 1–3 R– behaves as a chelating, C,N-centred ligand, and that the lone pair on tin is stereochemically active. The mean Sn–C [and Sn–NC5H4] bond lengths (Å) are 2.35(2)[2.42(2)] in 1, 2.32(2)[2.27(3)] in 2, and 2.356(8)[2.299(5)] in 3. Variable-temperature multinuclear (1H, 13C, 29Si and 119Sn) NMR spectral data were obtained for 1–3 in [2H8]toluene. These showed that dynamic processes were operative, believed to be Sn–N(C5H4) dissociations, with ΔG‡ Tc = 43.5 ± 0.8 for 2 or 42.7 ± 0.8 kJ mol–1 for 3(the coalescence temperature Tc being 220 ± 2 for 2 and 214 ± 2 K for 3); for 3 a further fluxion with ΔG‡ Tc = 76.1 ± 0.8 kJ mol–1(Tc= 368 ± 2 K) is attributed to the barrier to rotation about the tin–amide nitrogen bond. Attempts were made to reduce 2[evidence for (SnR)n], and to prepare analogues of GeII and PbII of 1 and 2. A further β-functionalised complex, SnCl(OCBut 2CH2PMe2)4, was obtained from SnCl2 and ½2[Li(OCBut 2CH2PMe2)]2; there was no evidence for 31P–119Sn coupling, and a plausible structure is [Sn(µ-Cl)(OCBut 2CH2PMe2)]2. A similar metathetical reaction between SnCl2 and Sn(OC6H3But 2-2,6)2 in tetrahydrofuran (thf) gave 1//m [SnCl(OC6H3But 2–2,6)(thf)n]m, whereas SnCl2+ SnR′2[R′= CH(SiMe3)2] yielded SnR′2Cl2+ Sn.Keywords
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