New aryl phosphinite ligands avoiding ortho-metallation: Synthesis and molecular structures of trans-[PdCl2(PPh2OR)2] and trans-[Rh(CO)Cl(PPh2OR)2] (R = 2,4,6-Me3C6H2; 2,6-Ph2C6H3)

The new aryl phosphinites PPh2OR (R = 2,4,6-Me3C6H2, 1; R = 2,6-Ph2C6H3, 2) have been prepared from chlorodiphenylphosphine and the corresponding phenols. In these ligands, the ortho-positions of the aromatic phosphite function are blocked by methyl and phenyl substituents, which allows coordination to metal centres without ortho-metallation. Thus, reaction with [PdCl2(cod)] leads to the complexes trans-[PdCl2(PPh2OR)2] (R = 2,4,6-Me3C6H2, 3; R = 2,6-Ph2C6H3, 4), while the reaction with [Rh2(CO)4Cl2] gives trans-[Rh(CO)Cl(PPh2OR)2] (R = 2,4,6-Me3C6H2, 5; R = 2,6-Ph2C6H3, 6). The single-crystal X-ray structure analyses of 3 and 5 confirm the trans-coordination of the new ligands in these square-planar complexes.