CARBENE DERIVATIVES OF [IR-4(CO)(12)] - CRYSTAL-STRUCTURES OF [IR-4(CO)(12-X)(COCH2CH2O)(X)] (X=1, 2, 3)

[Ir-4(CO)(12)] reacts with oxirane in the presence of Br- to give [Ir-4(CO)(12-x)(COCH2CH2O)(x)] (x=1, 2, 3). The structures of the three products were established by X-ray diffraction studies. All ligands are in terminal positions in [Ir-4(CO)(11)(COCH2CH2O)]. The di- and tri-substituted cluster compounds have 3 edge-bridging COs and dioxycarbene ligands in axial positions. The fluxional behaviour of these Ir-4 clusters, as studied by 2D C-13 NMR spectroscopy, is due to CO site exchanges localised on one or on three Ir atoms.