Transforming PPh3 into bidentate phosphine ligands at Ru–Zn heterobimetallic complexes

Abstract

The reaction of [Ru(PPh₃)₃Cl₂] with excess ZnMe₂ led to P–C/C–H bond activation and P–C/C–C bond formation to generate a chelating diphenylphosphinobenzene ligand as well as a cyclometallated (diphenylphosphino)biphenyl group in the final product of the reaction, [Ru(dppbz)(PPh₂(biphenyl)′)(ZnMe)] (1; dppbz = 1,2-bis(diphenylphosphino)benzene); PPh₂(biphenyl)′ = cyclometallated PPh₂(biphenyl). The mechanism of reaction was studied and C–C coupling to give a bidentate 2,2′-bis(diphenylphosphino)biphenyl (BIPHEP) ligand was suggested to be one of the key steps of the process. This was confirmed by the reaction of [Ru(BIPHEP)(PPh₃)HCl] with ZnMe₂, which also gave 1. An analogous set of steps took place upon addition of ZnMe₂ to [Ru(rac-BINAP)(PPh₃)HCl] (rac-BINAP = racemic(2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) to give [Ru(dppbz)(PPh₂(binaphthyl)′)ZnMe] (3). H₂ and the C–H bond of PhCCH added across the Ru–Zn bond of 1, and also reversed the phosphine cyclometallation, to give [Ru(dppbz)(Ph₂P(biphenyl))(H)₂(H)(ZnMe)] (4) and [Ru(dppbz)(Ph₂P(biphenyl))(CCPh)₂(H)(ZnMe)] (5) respectively.