Structures, semi-empirical calculations and thermolyses of some five- and six-membered chelate organotin mercaptide complexes

Characterization of Ph2Sn(Cl)(MBT) (1) (HMBT = 2-mercaptobenzothiazole) has been carried out by IR, Mossbauer, H-1, C-13 and Sn-119 spectroscopies and by X-ray crystallography for 1 together with that of Ph2Sn(SCH2CH2S) (2). Compound 1, unexpectedly obtained from the reaction between Ph2SnCl2 and KM BT in a 1:2 mole ratio, has a trigonal-bipyramidal geometry, due to intramo lecular Sn-N interactions, both in the solid state and in solution; the axi al sites are occupied by N and Cl, N(24)Sn-Cl(4) = 155.27(17)degrees, the c helate bite angle, N(24)-SN-S(15), is 64.65(17)degrees. Compound 2 is essen tially monomeric in the solid state and has a distorted tetrahedral structu re; the bond angles at tin vary from 92.50(16)degrees [S(2) Sn-S(5)] to 116 .4(6)degrees [C(6)-Sn-C(12)]. The shortest intermolecular Sn ... S contact in 2 is 3.885 Angstrom, just within the sum of the van der Waals' radii for Sn and S (4.0 Angstrom). PM3 semi-empirical calculations for 2 indicated t hat the geometry at the tin center can be accounted for by a high degree of p-character in the tin bonding orbitals to sulfur; PM3 semi-empirical calc ulations on Ph2Sn(SCH4CH2CH2S) (3) indicated the geometry at tin to be less distorted from tetrahedral, with a S-Sn-S angle of 99 degrees; the calcula tions further indicated that the only stable conformation of the six-member ed ring in 3 is the chair form. (C) 2000 Published by Elsevier Science S.A. All rights reserved.