Reactions of (mesityl)n(methyl)2−nsilylene complexes with pyridine-N-oxide (n = 1 and 0): formation of silanone complexes and a disiloxanyloxy complex

Abstract

Silanones (OSiR₂), a heavier congener of ketones (R₂CO), are highly reactive species that are readily converted to oligomeric siloxane (O–SiR₂)_n. Coordination of silanones to the transition-metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Recently, our group reported the synthesis, structures, and reactivity of dimesityl-substituted silanone complexes Cp*(OC)₂M{OSiMes₂(L)}(SiMe₃) (M = W, Mo, L: Lewis base, Cp*: η⁵-C₅Me₅, Mes: 2,4,6-Me₃C₆H₂). Herein, to investigate the effect of substituents on the silicon atom during the formation of a silanone complex, we demonstrated the use of Mes and smaller Me groups. As a result, the formation of Mes(Me)-substituted silanone molybdenum complex Cp*(OC)₂Mo{OSiMes(Me)(py)}(SiMe₃) (5b, py: pyridine) was suggested, the silanone tungsten complex Cp*(OC)₂W{OSiMes(Me)(DMAP)}(SiMe₃) (4a, DMAP: 4-(dimethylamino)pyridine) was obtained, and a dimethyl-substituted disiloxanyloxy(dioxo) complex Cp*(O)₂W(OSiMe₂OSiMe₃) (9) was formed. The reaction of 4a with PMe₃ proceeded via the elimination of DMAP and migration of the SiMe₃ group to the oxygen atom of the silanone ligand to afford Cp*(OC)₂W(SiMes(Me)OSiMe₃)(PMe₃) (11a). The Mo complex Cp*(OC)₂Mo(SiMes(Me)OSiMe₃)(PMe₃) (11b) was produced by the reaction of Cp*(OC)₂Mo{SiMes(Me)}(SiMe₃) (7b) with pyridine-N-oxide in the presence of PMe₃.