The synthesis and structure of sterically encumbered terphenyl tin(II) halide derivatives: simultaneous existence of monomers and dimers in the crystalline phase

The reaction of Et2O . LiC6H3-2,6-Trip(2) (Trip =C6H2-2,4,6-i-Pr-3) with Sn Cl2 afforded the two coordinate monomer Sn(Cl)C6H3-2,6-Trip(2) (1), and its dimer {Sn(mu -Cl)C6H3-2,6-Trip(2)}(2) (2), as orange and yellow crystals, respectively. Solution Sn-119 NMR spectroscopy of 2 in C6D6 solution showed that it dissociated readily to give 1. The addition of pyridine (py) to a solution of 1 yielded the adduct py.Sn(Cl)C6H3-2.6-Trip(2) (3) which featur ed tin in a three coordinate pyramidal environment. The reaction of the clo sely related bulky terphenyl lithium reagent LiC6H3-2,6-Dipp(2) (Dipp = C6H 3-2,6-i-Pr-2) with SnCl2 afforded the mixed halide species {Sn(mu -Cl)(0.35 )(mu -I)(0.65)C6H3-2,6-Dipp(2)}(2) (4). This arose from the preparation of the lithium aryl precursor in situ from IC6H3-2,6-Dipp(2) and n-BuLi. The m onomeric nature of 1, and the weak association of 2 and 4, were attributed to the large size of the terphenyl ligands. All compounds were characterize d by X-ray crystallography. H-1, C-13 and Sn-119 NMR spectroscopy, and IR a nd UV-Vis spectroscopy. (C) 2001 Elsevier Science B.V. All rights reserved.