Alkeneamino-carbene complexes of chromium: unexpected ring-expansion and ring-contraction reactions upon alkyne insertions

Abstract

The cycloaminocarbene complex (1)(OC)5CrC(Me)([graphic omitted]H2) reacts in boiling benzene with diphenylacetylene to give, upon alkyne insertion, C–N bond cleavage, rearrangement, and CO insertion, two new arene chromium complexes of unsaturated lactams (3) and (4) which result from, respectively, a ring contraction and a ring expansion reaction, and which have been fully characterized by X-ray analysis.