Synthesis and Structure of Pentavalent Bismuth(V) Alkoxides and Ligand Redistribution Equilibria in Solution

Abstract

The six new pentavalent Bi(V) alkoxide complexes Ph3Bi(OR)2, 1, Ph3BiBr(OR), 2, and Ph4Bi(OR), 3 (a, R = C6F5; b R = C6Cl5) have been prepared. Ph4Bi(OR) was synthesized by alcoholysis of BiPh5 with ROH. Ph3Bi(OR)2 and Ph3BiBr(OR) were products of the salt elimination reaction between Ph3BiBr2 and NaOR. These compounds were characterized spectroscopically and by single-crystal X-ray diffraction. In the solid state, they possess distorted trigonal bipyramidal coordination geometries. Although the mixed species Ph3BiBr(OR) may be isolated in pure form as crystalline solids, they do not exist as pure compounds in solution owing to the very rapid redistribution equilibrium Ph3Bi(OR)2 + Ph3BiBr2 ⇌ 2Ph3BiBr(OR). The equilibrium constants were measured using VT NMR spectroscopy. For comparison, the equilibrium constants for the previously unreported cross-exchange reactions between the dihalides Ph3BiX2 (X = F, Cl, Br) were also measured at 226 K. Trends observed in the values of Keq correlate with the differenc...