Structural Diversity of Sn(II) Phosphine Oxide Complexes with Weakly Coordinating Anions and Comparisons with Related Ge(II) and Pb(II) Species

Abstract

A series of tin(II) triflate phosphine oxide complexes has been prepared from the reaction of Sn(OTf)2 (OTf− = [O3SCF3]−) with various ratios of OPPh3, OPMe3 or dppmO2 (dppmO2 = Ph2(O)PCH2P(O)Ph2). The complexes [Sn(OPPh3)n][OTf]2 (n = 2, 3 or 4), [Sn(OPMe3)n][OTf]2 (n = 2 or 3) and [Sn(dppmO2)n][OTf]2 (n = 1 or 2) have been isolated in moderate to good yields. Selected germanium(II) and lead(II) analogues have been made for comparison, namely [Ge(OPPh3)n][OTf]2 (n = 2 or 3) and [Pb(OPR3)4][OTf]2 (R = Me, Ph). The effect of changing the weakly coordinating OTf− anion for the non-coordinating [BArF]− anion was investigated through anion metathesis, furnishing the complexes [Sn(OPPh3)n][BArF]2 (n = 3 or 4) and [Ge(OPPh3)3][BArF]2. The isolated solids were characterised by 1H, 19F{1H}, 31P{1H} and IR spectroscopy and microanalysis. Crystal structures were obtained for all complexes except [Ge(OPPh3)2][OTf]2 and [Sn(OPPh3)3][BArF]2, allowing comparisons of the structural features of these divalent group 14 complexes down the group and as a function of coordination number, ligand sterics and electronics.