The reactions of N,N'-bis(phosphinomethyl)dihydroperimidine pro-ligands HC(NCHPR)CH-1,8 (R = Ph 1a, R = Cy 1b) with iridium(i) substrates have been investigated and shown to readily result in chelate-assisted C-H activation processes. The reaction of 1b with [IrCl(COE)] (COE = cyclo-octene) affords the 18-electron iridium(iii) dihydrido complex [IrHCl{κ-C,P,P'-C(NCHPCy)CH}], which forms [IrHCl{κ-C,P,P'-C(NCHPCy)CH}] under acidic (HCl) conditions. In contrast, reaction of 1a with [IrCl(COD)] (COD = 1,5-cyclo-octadiene) affords the complex [IrCl(COD){κ-P,P'-HC(NCHPPh)CH}], thermolysis of which affords cyclo-octene and the pincer-NHC complex [IrCl{κ-C,P,P'-C(NCHPPh)CH}]. The reaction of 1a with two equivalents of [IrCl(COD)] provides the binuclear complex [Ir{μ-HC(NCHPPh)CH}Cl(COD)] which is also observed to accumulate and then dissipate during the preceding thermolysis. Related binuclear complexes [M{μ-HC(NCHPPh)CH}Cl(η-CMe)] (M = Ir, Rh) which obviate C-H activation were similarly synthesised.
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