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Synthesis of a Heterometallic Trinuclear Cluster of Ruthenium and Platinum with a Linear Alignment

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posted on 26.07.2016, 21:13 by Takuya Kuzutani, Yushi Torihata, Hiroharu Suzuki, Toshiro Takao
A heterobimetallic trinuclear complex of Ru and Pt in a linear alignment, {Cp*Ru­(H)2}2(Pt)­(μ-PtBu2)2(μ-H)2 (2; Cp* = η5-C5Me5), was synthesized via P–C bond scission upon the photolysis of Cp*Ru­(μ-H)4RuCp* (1) in the presence of Pt­(PtBu3)2. Complex 2 was alternatively synthesized by the reaction of 1 with Pt­(PtBu2H)3, together with the formation of a triangular Ru2Pt complex, (Cp*Ru)2{Pt­(PtBu2H)}­(μ-PtBu2)­(μ-H)3(H)2 (4). X-ray diffraction experiments showed that the structure of 2 could be regarded as a dimer of [Cp*RuH3(PtBu2)] fragments linked by a Pt2+ ion. In contrast to the relevant monometallic trihydrido complex of ruthenium, Cp*RuH3(PtR3), terminal hydrides of 2 were readily substituted by CO and ethylene, leading to the formation of {Cp*Ru­(L)}2(Pt)­(μ-PtBu2)2(μ-H)2 (5; L = CO, 6; L = C2H4). Such high reactivity could be attributed to the facile formation of a coordinatively unsaturated intermediate owing to stabilization by bulky μ-PtBu2 moieties as well as electronic influence of the central Pt atom. In fact, terminal hydrides of 2 were readily removed upon evacuation, leading to the formation of tetra- and dihydrido complexes (Cp*Ru)­{Cp*Ru­(H)2}­Pt­(μ-PtBu2)2(μ-H)2 (3) and (Cp*Ru)2­Pt­(μ-PtBu2)2(μ-H)2 (8), consecutively. Upon hydrogenation, 3 and 8 were smoothly transformed into 2. In contrast with the reactions of 2 with 2e donors, substitution at the Pt atom occurred in reactions with Ph2SiH2 and Et2SiH2, resulting in μ-silylene and μ-silyl complexes {Cp*Ru­(H)}­{Cp*Ru­(PtBu2H)}­Pt­(μ-PtBu2)­(μ-SiPh2)­(μ-H)2 (9) and {Cp*Ru­(H)2}­{Cp*Ru­(PtBu2H)}­Pt­(μ-PtBu2)­(μ-η2-SiEt2)­(μ-H)2 (10), respectively. In these reactions, the μ-phosphido ligand bridging the Ru and Pt atoms was transformed into a terminal phosphine ligand at the peripheral Ru atom, alongside the formation of μ-silylene and μ-silyl ligands via reductive P–H bond formation.