Microwave preparation of osmium clusters with anticancer activity; rapid syntheses of Os6(CO)18, Os3(CO)10(acetonitrile)2, and Os3(μ-H)(μ-OH)(CO)10

Microwave-assisted syntheses of the osmium cluster synthons Os-6(CO)(18), Os-3(CO)(10)(NCMe)(2), and Os-3(mu-H)(mu-OH)(CO)(10) are reported. Microwave irradiation of Os-3(CO)(12) in a small amount of 1,2-dichlorobenzene is shown to be a superior method of preparing Os-6(CO)(18) that produces a relatively high yield in only 35 min of heating instead of many days of pyrolysis. In a simple two-step method requiring less than 1 h, the labile complex Os-3(CO)(10)(NCMe)(2) is prepared in excellent yield (over 90%). This preparation is accomplished without the need to exclude air from the reaction vessel, and with one-tenth as much solvent and one-half as much trimethylamine-N-oxide as the standard method of synthesis. The cluster Os-3(mu-H)(mu-OH)(CO)(10) is also conveniently prepared with a small amount of solvent by heating a mixture of Os-3(CO)(12), silica gel, toluene and water in a microwave reactor for 2 h. (C) 2011 Elsevier B. V. All rights reserved.