Dioxycarbene complexes derived from reactions of tetrairidium carbonyl clusters with oxirane: X-ray crystal structures of and

Some novel cyclic-dioxycarbene derivatives of general formula (L = P^tBu₃, n = 1 (2), PPh₃: n = 1 (3), 2 (4)) and (L-L = PPh₂PCH₂PPh₂, n = 1 (5), norbornadiene, n = 1 (6) and 1,5-cyclooctadiene, n = 1 (7), 2 (8)) have been obtained by reaction of oxirane with the tetrairidium cluster derivatives [Ir₄(CO)₁₁(L)] and [Ir₄(CO)₁₀(L-L)] in the presence of bromide ion as catalyst. Elemental analysis, IR, and NMR spectra (¹H, ³¹P{¹H}, ¹³C{¹H}), and for compounds 2 and 5 also the X-ray crystal structures, were carried out for their characterisation. All the derivatives have 3 edge-bridging CO’s on the basal face of the iridium tetrahedron with non-CO ligands in axial and/or radial positions. For the mixed-ligand cluster compounds, two or three stereoisomers were observed in solution by ¹H, ³¹P and ¹³C NMR spectroscopies at low temperature. All these clusters are fluxional at room temperature.