Tetraosmium carbonyl clusters

An early example of surface-mediated synthesis led to the conversion of Os3(CO)i2 into [Os5C(CO)i4] [13]. Quantitative characterization of the formation of this cluster on MgO by C NMR spectroscopy [15] showed that the synthesis gave [OssCCCOIm] " in a yield of about 65% other products included triosmium and tetraosmium carbonyl clusters. A schematic representation of the surface chemistry is shown in Fig. 1. 

The neutral tetraosmium carbonyl cluster [Os4(CO)is], mentioned in COMC (1995), has an unusual planar OS4 skeleton with adjacent long and short peripheral metal-metal bonds (i.e., a kite structure). The stability of this planar metallic core configuration has been confirmed by extended Hilckel calculations. ... 

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