Synthesis of (Vinylallene)rhodium(III) Complex of Planar Structure: Perfect π → σ Conversion of 1,3-Diene System

摘要

The structures of conjugated diene-transition metal eom-plexes have attracted considerable attention owing to the great diversity of the binding modes. For example, most middle and late transition metal-diene complexes assume the conventional π~2-bonded structures 1. On the other hand, early transition metals prefer the bent σ~2,π -bonded metallacyclo-3-pentene form 2. The s-trans binding has been also reported. Stereochemical fluxionality of s-cis complexes has been often obser-ved and explainedby a ring-flipping mechanism. Although implicated as a tran.sitoiy species in the ring flipping, examples of thennodynamically stable planar σ~2-bonded complexes (3) remain few in number and are mostly limited to perfluoro-1,3-butadiene and vinyl ketene complexes.