Crystal Structure and Catalytic Properties of a Platinum-Iridium Mixed Cluster, [ Pt,lr,(p-CO), ( CO), ( PPh3)3] t

The compound [Pt,lr,(CO),(PPh,),] has been synthesised from [Pt12(C0)24]2- and [Ir(CO)CI(PPh,),]. A single-crystal X-ray structure determination (space group P i, 2 = 2, R = 0.050 for 5 402 reflections) has shown that the metal atoms adopt a 'butterfly ' configuration with the iridium and platinum atoms occupying 'hinge ' and 'wing-tip ' positions respectively. The mixed-metal cluster is an active catalyst for hydrogenation of olefins. Mixed-metal carbonyl clusters are of interest as precursors for the preparation of alloy-type heterogeneous catalysts and also as homogeneous catalysts of high Despite the rapid growth in the number of mixed-metal clusters reported, there appears to be no previous crystallographic study of an iridium-platinum cluster; structures have been reported for two hydrido-bridged binuclear IrPt c o m p l e ~ e s. ~ * ~ Here we report the synthesis and crystal structure determination of [Pt,Ir,(CO),(PPh,),] (l), which is also found to catalyse olefin-hydrogenat ion reactions. Results and Discussio