Tripodal bis(2,6-iminophosphoranyl)pyridine ligands: Iron and cobalt complexes with a potential in ethene polymerisation

By Staudinger Reaction of bis-2,6-diphenylphosphanyl-pyridine with aryl-, alkyl- and silylazides tripodal ligands L= 2,6-(Ph2P=NR)(2)C5H3N (R= Ph 1a, Mes 1b, Ad 1c, SiMe3 1d) are synthesized. The reaction of ligand Ib with equimolar amounts of [CoCl2(THF)(2)] and [FeCl2(THF)(1.5)] in THF does not lead to the expected neutral complexes [(kappa (3)-L)MCl2] but to coordination compounds of the composition L-2(CoCl2)(3) (2a) and L(FeCl2)(2 ()3). By using acetonitrile as solvent or by crystallisation of 2a from hot acetonitrile the cationic complex [(kappa (3)-L)CoCl(MeCN)]Cl (2b) is formed as a second product. The molecular structure 2b has been characterized by an X-ray single crystal structure analysis (triclinic. P (1) over bar, Z = 2, a = 1299.8(1), b = 1488.8(2), c = 1674.2(2) pm, alpha= 82.911(13)degrees, beta= 76.715(12)degrees, gamma= 72.758(11)degrees), A preliminary test with 3 shows, that coordination compounds of the ligand system introduced here have potential as catalysts in methyl alumoxane mediated ethene polymerisation.