ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Hemilabile imino-phosphine palladium(II) complexes: synthesis, molecular structure, and evaluation in Heck reactions

William M. Motswainyana, Martin O. Onani, Roger A. Lalancette, and Paul K. Tarus

Chemistry Department, University of the Western Cape, Private Bag X17, 7535, Bellville, South Africa

E-mail: monani@uwc.ac.za

Abstract: The ligands 2-(diphenylphosphino)benzyl-(2-thiophene)methylimine (V) and 2-(diphenylphosphino) benzyl-(2-thiophene)ethylimine (VI) were prepared from 2-(diphenylphosphino)benzaldehyde and thiophene amines with very good yields. An equimolar reaction of V and VI with either PdCl₂(cod) (cod = cyclooctadiene) or PdClMe(cod) afforded palladium(II) complexes I–IV. The molecular structure of II was confirmed by X-ray crystallography. The coordination geometry around the palladium atom exhibited distorted square planar geometry at the palladium centre. Complexes I, II, and IV were evaluated as catalysts for Heck coupling reactions of iodobenzene with methyl acrylate under mild reaction conditions; 0.1 mole % catalyst, Et₃N base, MeCN reflux for 8 h, 80°C; isolated yield on a 10 mmol scale with catalyst I (64 %), II (68 %), and IV (58 %). They all exhibited significant activities.

Keywords: imino-phosphine – palladium – Schiff-base molecular structures – Heck reaction

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-013-0530-6

Chemical Papers 68 (7) 932–939 (2014)