Rigid five-coordinate diorganotin derivatives of oxalic acid diamides, studied by 119Sn-NMR and X-ray structural analysis

Bis(2-hydroxy-3, 5-di-tert-butyl-phenylanilido) oxalic acid reacts with diorganotin dichlorides, R2SnCl2, in the presence of triethylamine to give the polycyclic bis(diorganotin) derivatives 1, in which the surroundings of each tin atom correspond to a distorted trigonal bipyramid with one nitrogen and two carbon atoms in the equatorial and two oxygen atoms in the axial positions. The solid state structure was established for la (R = Me) by X-ray analysis, and the agreement between the Sn-119 chemical shift in the solid state and in solution suggests that this structure is retained in solution. It was possible for the first time to determine isotope-induced chemical shifts (1)Delta(12/13)C(Sn-119) for five-coordinate tin nuclei at natural. abundance of C-13. A positive sign of (1)Delta(12/13)C(Sn-119) was found for R = Me (1a), Bu (1b) and Ph (1c). (C) 2000 Elsevier Science S.A. All rights reserved.