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

Silanones (OSiR 2 ), a heavier congener of ketones (R 2 CO), are highly reactive species that are readily converted to oligomeric siloxane (O-SiR 2 ) 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) 2 M{OSiMes 2 (L)}(SiMe 3 ) (M = W, Mo, L: Lewis base, Cp*: η 5 -C 5 Me 5 , Mes: 2,4,6-Me 3 C 6 H 2 ). 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) 2 Mo{OSiMes(Me)(py)}(SiMe 3 ) (5b, py: pyridine) was suggested, the silanone tungsten complex Cp*(OC) 2 W{OSiMes(Me)(DMAP)}(SiMe 3 ) (4a, DMAP: 4-(dimethylamino)pyridine) was obtained, and a dimethyl-substituted disiloxanyloxy(dioxo) complex Cp*(O) 2 W(OSiMe 2 OSiMe 3 ) (9) was formed. The reaction of 4a with PMe 3 proceeded via the elimination of DMAP and migration of the SiMe 3 group to the oxygen atom of the silanone ligand to afford Cp*(OC) 2 W(SiMes(Me)OSiMe 3 )(PMe 3 ) (11a). The Mo complex Cp*(OC) 2 Mo(SiMes(Me)OSiMe 3 )(PMe 3 ) (11b) was produced by the reaction of Cp*(OC) 2 Mo{SiMes(Me)}(SiMe 3 ) (7b) with pyridine- N -oxide in the presence of PMe 3 .