MIXED GROUP-14-GROUP-14 BONDS .6. HEXA-ORTHO-TOLYLETHANE ANALOGS ORTHO-TOL6PBSN AND ORTHO-TOL6PB2 - COMPARISON OF BOND STRENGTH AND POLARITY FOR THE PARIS SN-SN, PB-SN, PB-PB

The lead-tin compounds o-Tol6PbSn. o-Tol3PbSnPh3 and MeS3PbSnPh3 have been synthesized from Li and halide precursors in THF/ether at low tem peratures. The crystal structures of the S4 symmetric o-Tol4Pb and of the three isomorphous title compounds have been determined (d(Sn-Sn) 2 .883 (1), d (Pb-Sn) 2.845 (2), d (Pb-Pb) 2.895 (2) angstrom). The long Sn-Sn distance is in accordance with the Raman data for the pairs of p-Tol6/o-Tol6 substituents (nu(Sn-Sn) 131/123, nu(Pb-Sn) 114/114. nu(P b-Pb) 105/103 cm-1). The sequence of the Sn-119 and Pb-207 chemical sh ifts shows clearly a polarity Pb(delta-)-Sn(delta+ for all lead-tin co mpounds investigated. The 1J(Sn-119-Pb-207) and 1J(Sn-119-Sn-119) coup lings of identically substituted compounds depend upon another in a ne arly linear manner.