Synthesis and Structural Characterization of Transition Metal Oxo (Hydroxo) Siloxides: Reactions of Transition Metal Dialkylamides with Diphenylsilanediol

摘要

A systematic approach to the synthesis of molecular metallosiloxanes was investigated via the reaction of transition metal dialkylamides with diphenylsilanediol. Reaction of Ti(NEt sub 2 ) sub 4 with Ph sub 2 Si(OH) sub 2 yielded the molecular complexes (H sub 2 NEt sub 2 ) sub 2 (Ti sub 4 O sub 2 (OH) sub 2 (OSiPh sub 2 O) sub 6 ) and (H sub 2 NEt sub 2 ) sub 2 (Ti sub 4 O sub 2 (OH) sub 2 (OSiPh sub 2 O) sub 5 ((OSiPh sub 2 ) sub 2 O)). Reaction of the vanadium(V) dialkylamide, OV(NEt sub 2 ) sub 3 with Ph sub 2 Si(OH) sub 2 afforded (H sub 2 NEt sub 2 ) sub 2 (V sub 2 O sub 4 (OSiPh sub 2 O) sub 2 ) and (H sub 2 NEt sub 2 )(VO sub 2 (OSiPh sub 2 ) sub 3 O)), a bridged dimer and a chelated monomer, respectively. Reaction of the vanadium(IV) dialkylamide V(NEt sub 2 ) sub 4 gave (Li(THF) sub 2 ) sub 2 (VO((OSiPh sub 2 ) sub 2 O) sub 2 ). Infrared studies on the new metallosiloxanes allowed differentiation between mononuclear and polynuclear structures. An Si-O-Si infrared band revealed the presence of the homocondensed form of the ligand, while the position of the band was indicative of the extent of ligand polymerization. The solution molar conductivities of all of the complexes in non-coordinating solvents were anomalously low. Acidification and conversion to tetraalkylammonium derivatives resulted in the expected conductivities for 2:1 electrolytes. Silicon-29 MASNMR spectra of the metallosiloxanes revealed a correlation between the average M-O-Si (M = Si, T, V) bond angle and the chemical shift. Reaction of Ph sub 2 Si(OH) sub 2 with dialkylamides of Cr, Mo, Zr, Si and Al, and with the trimethylsilylamides of Fe and Co gave polymeric products containing M-O-Si structural units. (ERA citation 13:006186)