Reaction of [{Ir(CO)3(PPh3)}2] with substituted acetylenes. Part 1. Synthesis and crystal and molecular structure of [η-1,1-dicarbonyl-2,3,4,5-tetrakis(ethoxycarbonyl)-1-triphenylphosphineiridacyclopentadienyl]dicarbonyliridium

Abstract

The title compound [Ir(CO)₂{[graphic omitted](CO)₂(PPh₃)}] has been obtained by reaction of [{Ir(CO)₃(PPh₃)}₂] with EtO₂CCCCO₂Et in boiling benzene. The compound crystallizes as orthorhombic prisms in space group P2₁2₁2₁ with a= 20.655(9), b= 18.496(8), c= 10.027(5)Å, and Z= 4. The structure has been refined to R= 0.027 from 5 299 independent reflections. One metal atom is bonded to two carbonyl groups and to a metallacyclopentadienyl moiety via a η⁵ interaction; the other is bonded to two CO, one PPh₃, and to a buta-1,3-diene-1,4-diyl radical. The molecular parameters are compared with those of known cyclopentadienyl and metallacyclopentadienyl complexes of transition metals.