Group 9 bimetallic carbonyl permethylpentalene complexes

Abstract

We describe the synthesis, structure and bonding of the first iridium and rhodium permethylpentalene complexes, syn-[M(CO)₂]₂(μ:η⁵:η⁵-Pn*) (M = Rh, Ir). In fact, [Ir(CO)₂]₂(μ:η⁵:η⁵-Pn*) is the first iridium pentalene complex. An interesting preference for the isolation of the sterically more demanding syn-isomer is observed and substantiated by DFT analysis. Upon photolysis, the rhodium analogue yields an unusual tetrameric species Rh₄(CO)₆(μ:η³:η⁵-Pn*)₂ with bridging carbonyls and Rh–Rh bonds, which has been characterised by single crystal X-ray diffraction and by solution NMR spectroscopy.