Easy and reversible C-H activation of a substituted benzene

The reaction of either [RhCl(C8H14)(2)](2) or [RhCl(C2H4)(2)](2) with tBu(2 )PCH(2)CH(2)C(6)H(5) (3) affords at room temperature the five-coordinate ar ylhydridorhodium(III) complex 4, the molecular structure of which has been determined by X-ray crystallography. The C-H metalation is completely rever sible, as is shown by the formation of trans-[RhCl(CO)(3)(2)] from 4 and CO . Compound 4 also reacts with PhC=CH, H-2, and AgPF6 to give products 7-9 c ontaining the intact phosphine ligand 3.