A Silylene Stabilized by a σ-Donating Nickel(0) Fragment.

A donor-stabilized silylene 4 featuring a Ni 0 -based donating ligand was synthesized. Complex 4 exhibits a pyramidalized and nucleophilic Si II center and shows a peculiar behavior due to the cooperative reactivity of Si and Ni centers. Calculations indicate that the orientation of Ni-ligands with respect to the silylene moiety is crucial in determining the role of the Ni-fragment (Lewis acid or Lewis base) towards silylene. Indeed, a simple 90° rotation of the Si-Ni bond, reverses the role of Ni, and transforms a classical silylene→Ni 0 complex into an unprecedented Ni 0 →silylene complex.