A high-pressure infrared study of the stability of some ruthenium and osmium clusters to CO and H 2 under pressure

A high-pressure i.r. study has been made of the stability of some high-nuclearity carbonyl clusters of ruthenium and osmium to carbon monoxide and hydrogen, and of the thermal stabilities of these clusters under an inert atmosphere. In solution, the hexanuclear cluster [Os6(CO)18] reacts with CO (90 atm, 160 °C, 1 h) to produce the new pentanuclear cluster [Os5(CO)19] and [Os(CO)5]. In contrast, in the solid state [Os6(CO)18] adds 2 mol of CO to form [Os6(CO)20]. The pentanuclear carbonyl [Os5(CO)19] undergoes reaction with CO to give both [Os3(CO)12] and [Os2(CO)9], and with [Os2(CO)9] to give [Os7(CO)21]. On heating in an inert atmosphere [Os5(CO)19] loses CO to generate [Os5(CO)16]. This reaction is reversible. Reaction of [Os5(CO)16], [Os5H2(CO)16], [Os6(CO)18], or [Os6H2(CO)18] with H2 under moderate pressures and temperatures gives [OS4H4(CO)12] and [OsH2(CO)4]; [Os5(CO)19] first produces [Os5(CO)16] and proceeds to the same products. On carbonylation under pressure [Ru3(CO)12] yields [Ru(CO)5], and [Ru6(CO)17C] gives a mixture of [Ru5(CO)15C] and [Ru(CO)5]. Pyrolysis of [Ru6H2(CO)18] under argon at 120 °C gives the hexanuclear carbide [Ru6(CO)17C] in high yield.