Does the Schrock-type metal—silylene complex exist?

Abstract

We have studied theoretically the stability and the reactivity of the Schrock-type metal—silylene complexes (CH 3)H 2NbSiR 2 (RH, OH) as well as those of the Fischer-type (CO) 4FeSiR 2 and (CO) 5CrSiR 2 (RH, OH). The stability of the NbSi bond in (CH 3)H 2NbSiR 2 is larger than that of the FeSi and CrSi complexes which have been synthesized recently. This suggests that the Schrock-type metal silylene complex may be synthesized as a stable one. An orbital correlation diagram shows that there is an obvious metal—Si double bond in (CH 3)H 2NbSiR 2. Both electrophiles and nucleophiles will attack Nb, though a possibility of nucleophilic attack on Si also exists. First singlet and triplet excited states of (CH 3)H 2NbSiH 2 lie within 1 eV of the ground state. These excitations do not weaken the NbSi bonding, though the SiH bonds are considerably weakened.