Synthesis and Reactivity of a Dithiolate-Bridged Ruthenium−Rhodium Heterobimetallic Dihydride Complex

The new dithiolate-bridged Ru−Rh heterobimetallic dihydride complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)RuH(PPh3)2] (2) has been prepared, and its reactions with CO and alkynes have been studied. Treatment of the rhodium 1,2-benzenedithiolate complex [Cp*Rh(1,2-S2C6H4)] (Cp* = η5. 5BJ5) with [RuHCl(PPh3)3] in THF produces the hydride- and dithiolate-bridged Ru−Rh heterobimetallic complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)RuCl(PPh3)2] (1), which was further converted to the dihydride complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)RuH(PPh3)2] (2) upon treatment with KOH/i-PrOH. Complex 2 reacts with CO to give the dicarbonyl complex [Cp*Rh(μ2-1,2-S2C6H4)Ru(CO)2(PPh3)] (3). Reaction of 2 with p-tolylacetylene (2 equiv) proceeds with hydrogenation of the alkyne and subsequent oxidative addition of the sp C−H bond to give the alkynyl hydride complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)Ru(C&tbd1;CTol-p)(PPh3)2] (4a). The analogous alkynyl hydride complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)Ru(C&tbd1;CSiMe3)(PPh3)2] (6 ) has also been prepared. Complex 4a reacts with excess p-tolylacetylene to produce the ruthenacyclopentadiene complex [Cp*Rh{μ2-η2:η4-1,3-(p-Tol)2C4H2}Ru(S2C6H4)(PPh3)] (5), whereas similar treatment of 4a with excess diphenylacetylene induces 1:2 coupling of the two different alkynes to form the η6-arene complex [Cp*Rh(μ2-1,2-S2C6H4)Ru{η6. 6SK4H(p-MeC6H4)}] (6). Reaction of 4a with CO proceeds with dissociation of one of the Ru−S bonds and with retention of the alkynyl hydride structure to give the CO adduct [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)Ru(C&tbd1;CTol-p)(CO)(PPh3)2] (7). The structures of 1, 3, 6 , and 5−7 have been determined by X-ray crystallography.