Collect. Czech. Chem. Commun. 2001, 66, 1062-1077

Influence of Metal Core Composition on Redox Properties and Photoreactivity of the Clusters [H4-xRu4-xRhx(CO)12] (x = 0, 2, 3, 4)

Maarten J. Bakkera, Tapani A. Pakkanenb and František Hartla,*

a Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
b Department of Chemistry, University of Joensuu, P.O. Box 111, 80101 Joensuu 10, Finland


Electrochemical properties of tetrahedral clusters [H2Ru2Rh2(CO)12], [HRuRh3(CO)12] and [Rh4(CO)12] were investigated in order to evaluate the influence of metal core composition in the series [H4-xRu4-xRhx(CO)12] (x = 0-4). The cluster [H3Ru3Rh(CO)12] was not available in sufficient quantities. As reported for [H4Ru4(CO)12], electrochemical reduction of the hydride-containing clusters [H2Ru2Rh2(CO)12] and [HRuRh3(CO)12] also results in (stepwise) loss of hydrogen, producing the anions [HRu2Rh2(CO)12]-, [Ru2Rh2(CO)12]2- and [RuRh3(CO)12]-. These anions can also be prepared from the neutral parent clusters via chemical routes. Electrochemical reduction of [Rh4(CO)12] does not result in the formation of any stable tetranuclear anion. Instead, [Rh5(CO)15]- and [Rh6(CO)15]2- are the major reduction products detected in the course of IR spectroelectrochemical experiments. Most likely, these cluster species are formed from the secondary CO-loss product [Rh4(CO)11]2- by fast redox condensation reactions. Their reoxidation regenerates parent [Rh4(CO)12], together with some [Rh6(CO)16]. Unlike [H4Ru4(CO)12] that undergoes photochemical CO-dissociation, [H2Ru2Rh2(CO)12] and [Rh4(CO)12] are completely photostable in neat hexane and dichloromethane as well as in the presence of oct-1-ene.

Keywords: Ruthenium; Rhodium; Mixed-metal clusters; Redox properties; Hydrides; Carbonyl complexes; IR spectroscopy; Spectroelectrochemistry; Electrochemistry; Photochemistry.

References: 38 live references.