Reactions of (mesityl)(methyl)silylene complexes with pyridine--oxide ( = 1 and 0): formation of silanone complexes and a disiloxanyloxy complex.

Silanones (OSiR), a heavier congener of ketones (RCO), are highly reactive species that are readily converted to oligomeric siloxane (O-SiR). 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)M{OSiMes(L)}(SiMe) (M = W, Mo, L: Lewis base, Cp*: η-CMe, Mes: 2,4,6-MeCH). 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)Mo{OSiMes(Me)(py)}(SiMe) (5b, py: pyridine) was suggested, the silanone tungsten complex Cp*(OC)W{OSiMes(Me)(DMAP)}(SiMe) (4a, DMAP: 4-(dimethylamino)pyridine) was obtained, and a dimethyl-substituted disiloxanyloxy(dioxo) complex Cp*(O)W(OSiMeOSiMe) (9) was formed. The reaction of 4a with PMe proceeded the elimination of DMAP and migration of the SiMe group to the oxygen atom of the silanone ligand to afford Cp*(OC)W(SiMes(Me)OSiMe)(PMe) (11a). The Mo complex Cp*(OC)Mo(SiMes(Me)OSiMe)(PMe) (11b) was produced by the reaction of Cp*(OC)Mo{SiMes(Me)}(SiMe) (7b) with pyridine--oxide in the presence of PMe.