Structures and Reactivities of Palladium−Ruthenium Mixed-Metal Sulfido Clusters Derived from Disulfido- or Hydrosulfido-Bridged Diruthenium Complexes

The reaction of the disulfido-bridged diruthenium complex [Cp*Ru(μ₂-S₂)(μ₂-SPrⁱ)₂RuCp*] (1; Cp* = η⁵-C₅Me₅) with 2 equiv of [Pd(PPh₃)₄] in boiling toluene resulted in the formation of the palladium−ruthenium mixed-metal sulfido cluster [(Cp*Ru)₂(μ₃-S)₂Pd₂(μ₂-SPrⁱ)(SPrⁱ)(PPh₃)] (2). Upon treatment with benzyl bromide, stepwise substitution of the thiolato ligands in 2 by bromo ligands took place to afford the monobromo cluster [(Cp*Ru)₂(μ₃-S)₂Pd₂(μ₂-SPrⁱ)Br(PPh₃)] (4) and the dibromo cluster [(Cp*Ru)₂(μ₃-S)₂Pd₂(μ₂-Br)Br(PPh₃)] (5). On the other hand, the cationic palladium−ruthenium sulfido cluster [(Cp*Ru)₂(μ₃-S)₂Pd₂(μ₂-Cl)(PPh₃)₂]Cl (7) was obtained by the reaction of the hydrosulfido-bridged diruthenium complex [Cp*RuCl(μ₂-SH)₂RuClCp*] (6) with 2 equiv of [Pd(PPh₃)₄]. The structural feature commonly observed for the 60e clusters 2, 4, 5, and 7 is the presence of a distorted-tetrahedral Pd₂Ru₂ core containing one Pd−Pd (2.780(1)−2.8130(8) Å) and one Ru−Ru bond (2.6231(7)−2.6386(9) Å) as well as four relatively long Pd−Ru contacts (2.831(1)−3.095(2) Å). Furthermore, 7 reacted with CO to afford the 64e carbonyl cluster [{Cp*Ru(CO)}₂(μ₃-S)₂{PdCl(PPh₃)}₂] (8) with a boatlike Pd₂Ru₂(μ₃-S)₂ framework. The detailed structures of 2, 4, 5, 7, and 8 have been determined by X-ray crystallography.