Group 9 and 10 Metal Complexes of an Ylide-Substituted Phosphine: Coordination versus Cyclometalation and Oxidative...

Ylide-substituted phosphines (YPhos) have been shown to be excellent ligands for several transition metal catalyzed reactions. Investigations of the coordination behavior of the YPhos ligand Y_SPPh₂ (1) [with Y_S = (Ph₃P)(SO₂Tol)C] toward group 9 and 10 metals revealed a surprisingly diverse coordination chemistry of the ligand. With Ni(CO)₄, the formation of a di- as well as tricarbonyl complex is observed depending on the reaction conditions. In [( κP,η ² -benzene-1)Ni(CO)₂] the phosphine ligand also coordinates via a phosphonium bound phenyl group to the metal leading to a unique nickel η ² -arene interaction, which can be viewed as an intermediate state toward P-C bond activation. Full cleavage of the P-C bond takes place with [Rh(COD)Cl]₂ leading to a complex salt with [( κP,κO-1)Rh(COD)]⁺ as cation and a dirhodium trichloride complex anion. Here, Y_SPPh₂ underwent P-C bond cleavage to thus act as an anionic diphosphine ligand. In contrast, in [( κP,κO-1)Rh(COD)]⁺ as well as [( κP,κO-1)Rh(CO)Cl], formed from the reaction of 1 with [Rh(CO)₂Cl]_2, the YPhos ligand acts as bidentate ligand complexing the metal via the phosphine and sulfonyl moiety with an intact PPh₃ unit. A further type of coordination is observed with [Ir(COD)Cl]₂. Here, phosphine coordination is accompanied by C-H activation at one of the phosphonium bound phenyl groups leading to a cyclometalated complex.