Preparing α,β-unsaturated Fischer-type carbene complexes via an unforeseen route

Abstract

Four 4-(NH-amino)-1-metalla-1,3-diene carbene complexes, two of which contain novel 4-membered heterometallacycles, formed regioselectively from the reaction of a mixture of [(CH₃)₂(CH₃S)S][BF₄], the acetonitrilium electrophile, CH₃CNCH₃⁺, and the deprotonated alkoxycarbene complexes, (CO)₅MC(OCH₃)CH₂Li (M = Cr, W). The preferred Z-configurations of the alkoxy and amino groups are determined by strong H-bonding in the products. The metal–carbene bonds in the chelates are shorter by 0.08 Å than those in the acyclic compounds.