dppm and hydrido-bridged dinuclear complexes of iridium.: Synthesis and structures of [(IrCp*)2(μ-dppm)(μ-H)(μ-X)]2+ (X = Cl, OMe, OH, or H)

Reaction of [IrCp*Cl(mu-H)](2) 1 (Cp*=pentamethylcyclopentadienyl) with two equivalents of bis(diphenylphosphino)methane (dppm) gave an unidentate dppm complex IrCp*(H)(Cl)(dppm-P) 2. This reacted with a half equivalent of [IrCp*Cl(mu-Cl)](2) 3 to give a dppm-bridged dinuclear complex (Cl)(H)Cp*Ir(mu-dppm)IrCp*Cl-2 4, in which the two metal centers are distal. Reaction of 4 with two equivalents of AgOTf (OTf=O3SCF3) gave a dppm, hydride and chloride-bridged diiridium complex [(IrCp*)(2)(mu-dppm)(mu-H)(mu-Cl)][OTf](2) 5a. Complex 5a reacted with sodium methoxide in methanol to give [(IrCp*)(2)(mu-dppm)(mu-H)(mu-OMe)][OTf](2) 6a. This reacted with water in refluxing acetone to give a diiridium complex [(IrCp*)(2)(mu-dppm)(mu-H)(mu-OH)][OTf](2) 7a. Heating complex 6a in refluxing toluene gave [(IrCp*)(2)(mu-dppm)(mu-H)(2)][OTf](2) 8a. The structures of the anion exchanged complexes [(IrCp*)(2)(mu-dppm)(mu-H)(mu-X)][BPh4](2) [X=Cl 5b, OMe 6b, OH 7b or H 8b] have been confirmed by X-ray analysis.