Hexanuclear Iridium Clusters Supported on Magnesium Oxide

[Ir4(C0)12o] n the surface of MgO reacts to give [HIr4(CO)ll]-,w hich upon treatment with co at 200 OC gives [Ir6(C0)15]2- on the surface in high yield. Treatment of the latter with a solution of [PPN][CI] leads to extraction of [Ir6(C0)15]2b-y cation metathesis. The surface-bound [Ir6(CO)15]2w- as characterized by extended X-ray absorption fine structure (EXAFS) sk :e icnt rcolsocsoep ayg,r weeimthe tnhte w diatht at hined piucabtliinshge adn c rayvsetraalgloeg Irra-plrh icc odoartad ifnoart itohnis naunmiobne rin o tfh 4e. 1so alindd s taant ea.v Terhaeg er eIarc-Itrio ndsi sotfa nthcee iorfi d2iu.7m7 carbonyls on the basic MgO surface closely parallel those of iridium carbonyl anions in basic solutions. Treatment of the MgO-supported [h6(CO)IS]2- in He followed by H2 at 300 OC gives decarbonylated surface species shown by EXAFS spectroscopy to have iridium cluster frames substantially unchanged from those of the carbonyl anion precursor. The decarbonylated iridium clusters are among the most nearly uniform supported metals