SYNTHESIS, STRUCTURE, AND REACTIVITY OF THE 4-COORDINATE ARYL COMPLEX IR(CO)(2-MESITYL)(DPPE), WHICH DISPLAYS AN UNUSUAL ARYL TO BENZYL REARRANGEMENT

The synthesis, structure, and reaction chemistry of Ir(CO)(2-mesityl)(dppe) (1; dppe = 1,2-bis(diphenylphosphino)ethane) is described. Complex 1 is prepared from the reaction of 2-mesitylmagnesium bromide and IrBr(CO)(dppe). The molecular structure of 1 in the solid state is that of a nearly square-planar four-coordinate complex with cis phosphine donors, a sigma-bound mesityl ligand, and a slight tetrahedral distortion. Complex 1 reacts readily with diphenylsilane and H-2 to yield the respective cis oxidative-addition products IrHY(C6H2(CH3)3)(dppe), where Y = Ph2HSi, H. A unique transformation occurs when 1 is heated in the presence of ethylene at 90-degrees-C in benzene to yield Ir(CO)(eta-2-C2H4)(3,5-dimethylbenzyl)(dppe). The reaction of 1 with CO generates the acyl complex Ir(CO)2(C(O)mesityl)(dppe).