Synthesis of Bimetallic Dinuclear Hydrido Complexes of Re and Rh/Ir Supported by a Direct M-M' Bond: The Role of the M-M' Bond in the Site Exchange of Hydrides.

Heterometallic tetrahydrido complexes [Cp*Re(H)(μ-H)MCp*] (: M = Ir, : M = Rh) were synthesized by the reaction of [Cp*ReH] and [Cp*M(sol)] (M = Ir, Rh) followed by deprotonation. Although possesses four hydrides and adopts a 30-electron configuration as [Cp*Ru(μ-H)RuCp*] () does, the positions of the hydrides in differ from those in : two terminal and two bridging hydrides. In addition, adaptive natural density partitioning (AdNDP) analysis demonstrated that a direct Re-M bond is held in . Although cationic pentahydrido complexes [Cp*Re(H)(μ-H)MCp*] (: M = Ir, : M = Rh) do not contain a direct Re-M bond, the formation of a Re-M bond in the intermediate of the hydride site exchange was also inferred by DFT calculations. DFT calculations suggested that the Re-M bond plays a crucial role in the site exchange of hydrides in and . While μ-phosphido complex [Cp*(PPh)Re(H)(μ-H)(μ-PPh)Ir(H)Cp*] () was obtained by the reaction of with PPh, the treatment of with PMe resulted in the formation of a 1:1 mixture of [Cp*Re(H)(PMe)] and [Cp*Ir(H)PMe] via the rupture of the Re-Ir bond.