Transforming PPh3 into bidentate phosphine ligands at Ru-Zn heterobimetallic complexes.

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 PhC[triple bond, length as m-dash]CH 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))(C[triple bond, length as m-dash]CPh)2(H)(ZnMe)] (5) respectively.