Reactions of trifluoromethyl-phosphine and -arsine with a ruthenium carbonyl cluster: synthesis, characterization and reactivity of cluster derivatives capped by trifluoromethyl-phosphinidene and -arsinidene moieties

Reactions of CF3EH2 (E = P or As) with [Ru-3(CO)(12)] under various conditions resulted in the elimination of two hydrogen atoms to afford new trifluoromethyl-phosphinidene and -arsinidene capped ruthenium carbonyl clusters: [Ru-3(CO)(9)(mu-H)(2)(mu(3)-PCF3)] 1, [Ru-4(CO)(13)(mu-H)(2)(mu(4)-PCF3)] 2, [Ru-4(CO)(12)(mu-H)(2)(mu(3)-PCF3)(2)] 3, [Ru-5(CO)(15)(mu-H)(2)(mu(3)-PCF3)(3)] 4, [Ru-5(CO)(15)(mu(4)-PCF3)] 5, [Ru-4(CO)(12)(mu-H)(2)(mu(3)-AsCF3)(2)] 6, [Ru-4(CO)(13)(mu-H)(2)(mu(4)-AsCF3)] 7, [Ru-4(CO)(13)(mu(3)-AsCF3)(2)] 8 and [Ru-5(CO)(15)(mu-H)(2)(mu(3)-AsCF3)(3)] 9. The structures 2 and 7 contain spiked ruthenium frameworks with a phosphinidene or arsinidene group co-ordinated to all four metal atoms. The molecular structures of 4 and 9 have been shown to contain two-metal and three-metal fragments joined together by three mu(3)-phosphinidene (or arsinidene) units. The hydrides in 2 and 7 display similar fluxional behaviour yielding the same values of Delta G double dagger (= 49 kJ mol(-1)). The transformation from 1 to 5, probably via intermediate 2, occurs with increase in nuclearity by the treatment of 1 with [Ru-3(CO)(12)]. Pathways for the formation of cluster 3 from 2, 9 from [Ru-4(CO)(12)(mu-H)(2)(mu(3)-AsCF3)(2)(mu-AsCF3)] 10, and also 6 from 8 by hydrogenation are discussed.