Unexpected Formation of NHC-Stabilized Hydrosilylyne Complexes via Alkane Elimination from NHC-Stabilized Hydrido(alkylsilylene) Complexes

N-heterocyclic carbene (NHC)-stabilized
hydrosilylyne complex Cp*­(CO)2WSiH­(MeIMe)2 (3a) (MeIMe = 1,3,4,5-tetramethylimidazole-2-ylidene)
was formed
by the reaction of an NHC-stabilized silylene complex Cp*­(CO)2(H)­WSiH­(MeIMe)­{C­(SiMe3)3}
(2a) with 1 equiv of MeIMe at 70 °C.
In this reaction, HC­(SiMe3)3 was unexpectedly
eliminated from 2a. A C5Me4Et analogue
of 3a, (C5Me4Et)­(CO)2WSiH­(MeIMe)2 (3b), was also synthesized
by the same method, and the structure of 3b was confirmed
by X-ray crystallography. Although the silicon center of 3b is coordinated by two NHCs, the length of the W–Si bond of 3b [2.363(4) Å] is as short as that of the shortest WSi
double bond (∼2.36 Å). These complexes, 3a and 3b, are the first examples of a base-stabilized
silylyne complex having only a hydrogen on the silicon atom.