Some Aspects of Hydrocarbon Ligand Chemistry

It has been shown that 187Os satellites on H-nmr hydride signals may be used to identify otherwise unobservable dynamic processes. So far, this has not been applied extensively and not to hydrocarbon ligands (374). 

Catalysis by clusters has been a popular topic for discussion in spite of (or because of) our limited knowledge. Analogies with metal surfaces have been developed by some researchers while others have particularly considered supported clusters (see, for example, refs. 575 and 395-399). 

Directly supported clusters of type Os3H(CO)10(O—metal oxide) break down at quite low temperatures to give species which have a high selectivity to methane from CO and H2 (381,400). Similar behavior has been reported for Os3(CO)12 itself (401), but it is difficult to rule out metal as the catalyst. Os3(CO)12 also leads to methanol, methyl and ethyl formate, and acetone by reaction with CO and H 2 (190° C, 180 atm) in glyme solvents (402). The water-gas-shift reaction is catalyzed by Os3(CO)12, using KOH or even sodium sulfide in methanol as the base (403), although ruthenium catalysts are better (404). 

Other reactions that have been found to be catalyzed by Os3 clusters are alkene hydrogenation (51,385,392,407) and hydroformylation (408). Other researchers have considered pathways for alkyne hydrogenation at Os3 clusters (186) and for isonitrile (409) and nitrile (118,213) reduction. Os3-(CO)12 also catalyzes the conversion of dimethylaniline to (4-Me2NC6H4)2-CH2 (203) and exchange of D20 with trialkylamines (410,411). 

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