Insertion of CO and Alkenes into the (methyl)Pd Complexes of the Bidentate Porphyrin Ligand

Abstract

The (methyl)Pd complex of a bidentate N, 2 1 N 2 2 -1,2-diphenyletheno-bridged porphyrin ligand, Pd I I (Me)(Cl)(N 2 1 ,N 2 2 -(PhC=CPh)(TPP)), gave the (acetyl)Pd complex Pd I I (C(O)Me)-(Cl)(N 2 1 ,N 2 2 -(PhC=CPh)(TPP)) in 85%yield under atmospheric CO pressure. The acetyl-chloro site exchange in the (acetyl)Pd complex was monitored by variable-temperature NMR, and the ΔG3 2 3 value was estimated as 68 kJ mol - 1 . The reaction of the cationic (methyl)Pd complex [PdII(Me)(N 2 1 ,N 2 2 -(PhC=CPh)(TPP))(MeCN)]C104 with CO gave a cationic (acetyl)-(carbonyl)Pd complex which readily lost CO to give the (carbonyl)(methyl)Pd complex [Pd I I (Me)(N 2 1 ,N 2 2 -(PhC=CPh)(TPP))(CO)]ClO 4 . These Pd complexes were easily characterized by the 1 H NMR spectra. The X-ray crystal structures of the (acetyl)Pd complex and the (carbonyl)(methyl)Pd complexes were determined. Insertion of norbornadiene and norbornene into the cationic (carbonyl)(methyl)Pd complex occurred on the exo side. Two isomers with different orientations of the norbornenyl moiety relative to the bidentate porphyrin ligand were observed at low temperature, and isomerization by a ligand rotation mechanism occurred at room temperature to give a single isomer.