USE OF THE MONOCATIONIC FRAGMENT [RU(ETA(5)-C5H5)(MECN)(3)](-METAL CLUSTERS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF [OS3RUH(CO)(11)(ETA(5)-C5H5)] AND [OS3RU2(CO)(9)(ETA(3)-CO)(2)(ETA(5)-C5H5)(2)]() AS ACAPPING REAGENT IN THE SYNTHESIS OF MIXED)

The reaction of the monoanion [Os3H(CO)(11)](-) 1 with 1 equivalent of the cation [Ru(C5H5)(MeCN)(3)](+) 2, in CH2Cl2, formed the mixed-meta l, tetranuclear cluster [Os3RuH(CO)11(eta(5)-C5H5)] 3 in high yield. S ubsequent deprotonation of 3 with 1,8-diazabicyclo[5.4.0]undec-7-ene, in CH2Cl2, afforded the anion [Os3Ru(CO)(11)-(eta(5)-C5H5)](-) 4, and reaction of 4 with a second equivalent of [Ru(C5H5)(MeCN)(3)](+) provi ded the new bis-(cyclopentadienyl) cluster [Os3Ru2(CO)(9)(mu(3)-CO)(2) (eta(5)-C5H5)(2)] 5 in ca. 80% yield. Alternatively, reduction of [Os- 3(CO)(12)] with K/Ph2CO afforded the known cluster dianion [Os-3(CO)(1 1)](2-) 6 which can be treated with 2 equivalents of [Ru(C5H5)(MeCN)(3 )](+) to produce 5 in 75% yield. The clusters 3 and 5 have been fully characterised by both spectroscopic and crystallographic methods. The structure of 3 contains an Os3Ru tetrahedron in which the cyclopentadi enyl ligand is co-ordinated to the Ru atom in an eta(5) terminal mode. The metal framework in 5 is a trigonal bipyramid, but may be viewed a s an Os3Ru tetrahedral unit, as in 3, to which a second Ru atom cappin g an Os2Ru triangular face has been added. Both the cyclopentadienyl l igands remain in eta(5) terminal bonding sites co-ordinated to the two Ru atoms.