Lithium bridged cyclosiloxy-niobium(V) and -tantalum(V) complexes: thermal decomposition, solid-state and solution structural studies †

Abstract

Treatment of MCl 5 (M = Nb or Ta) with 3 equivalents of dilithium tetraphenyldisiloxanediolate, [(Ph 2 SiOLi) 2 O], gave the lithium-bridged metallasiloxane complex, [M{O(SiPh 2 O) 2 } 3 ]-µ-[Li(L) 2 ] (M = Nb 1 or M = Ta 2; L = pyridine). The solid-state structure of compound 2 determined by single crystal X-ray diffraction is reported. Variable-temperature 7 Li NMR of 2 revealed two separate exchange processes which may account for the equilibration of non-equivalent silicon environments in 1 and 2. Preparative scale thermal decomposition of the solid samples with L = tetrahydrofuran (thf) gave crystalline LiNbO 3 and LiTaO 3 .