Facile 1,2-Migration of a Methyl Group on a {Dimethoxy(methyl)silyl}tungsten Complex: Formation of a Base-Stabilized (Dimethoxysilylene)(methyl) Complex

Reactions of Cp*(CO)2W(DMAP)Me [1, Cp*
= η5-C5Me5, DMAP = 4-(dimethylamino)pyridine]
with trialkylsilanes HSiR2Et (R = Me, Et) afforded (DMAP)(trialkylsilyl)tungsten
complexes Cp*(CO)2W(DMAP)(SiR2Et) (2a, R = Me; 2b, R = Et). On the other hand, a reaction
of 1 with dimethoxy(methyl)silane, HSi(OMe)2Me, gave a DMAP-stabilized (dimethoxysilylene)tungsten complex, cis-Cp*(CO)2W(Me){Si(OMe)2·DMAP} (cis-3), through
1,2-migration of a methyl group from silicon to tungsten. Silylene
complex cis-3 isomerized
to its trans-isomer trans-3.