Cyclopalladation of trimesitylarsine. The X-ray crystal structure for

Abstract

The bulky trimesitylarsine ligand, As(mes)3, undergoes facile cyclopalladation to yield the dimeric complex, [Formula: see text], characterized by microanalysis, IR and 1H NMR spectroscopy. This complex is very stable but readily undergoes bridge-cleavage reactions with tertiary phosphine ligands having ligand cone angles less than 170°. The crystal structure for the PPh3 bridge-cleavage product is reported. This complex, [Formula: see text] is monoclinic, space group P21/c with a = 20.469(2), b = 12.702(2), c = 15.401(4) Å, β = 98.46(1)°, V = 3961 Å3Z = 4, R = 0.0284 and Rw = 0.0305. The Pd geometry is distorted square-planar with principal dimensions, Pd—Cl 2.395(1), Pd—P 2.318(1), Pd—C 2.056(3), and Pd—As 2.437(1) Å; As—Pd—Cl 96.5(1), Cl—Pd—P 90.9(1), P—Pd—C 93.7(1), As—Pd—C 78.9(1), As—Pd—P 172.6(1), and Cl—Pd—C 171.7(1)°. The average C—P—C angle (104.3(1)°) is smaller than expected and is rationalized on the basis of steric effects operative within the complex.