Stepwise transition metal promoted ring expansion reactions of vinylcyclopropenes to give cyclopentadienes and cyclohexa-2,4-dienones. The first example of a 1-metallacyclohexa-2,4-diene complex, {[Pt–CH2–CHC(Ph)–C(Ph)C(Ph)](PPh3)2}

Abstract

1,2,3-Triphenyl-3-vinylcycloprop-1-ene (1) reacts with [Pt(η²-C₂H₄)(PPh₃)₂] to give the first example of a 1-platinacyclohexa-2,4-diene complex (2)(the crystal structure of which has been determined), with [Rh(η⁵-C₉H₇)(η-C₂H₄)₂] to give the η⁴-cyclopentadiene compound (3), and with [Fe₂(CO)₉] to give the η⁴-cyclohexa-2,4-dienone complex (5); on heating, the metallacyclohexadiene (2) reductively eliminates 1,2,3-triphenylcyclopentadiene.