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-C5Me5) 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⋮CTol-p)(PPh3)2] (4a).
The analogous alkynyl hydride complex [Cp*Rh(μ2-1,2-S2C6H4)(μ2-H)Ru(C⋮CSiMe3)(PPh3)2] (4b) 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-C6Ph4H(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⋮CTol-p)(CO)(PPh3)2] (7). The structures of 1, 3, 4b, and
5−7 have been determined by X-ray crystallography.