Synthesis of cobalt(II) and iron(II) complexes with the ligand bis(2-diphenylphosphinoethyl)methylamine and their catalytic action on ethylene oligomerization.: X-ray crystal structure of [CoCl2{CH3N(CH2CH2PPh2)2}]

Complexes [MCl2{CH3N(CH2CH2PPh2)(2)}] (1, M = Co: 2, Fe) were prepared by a modified procedure. The X-ray structural determination of I reveals that the cobalt(II) complex is four-coordinate with a distorted tetrahedral coordination geometry. The tertiary amine CH3N(CH2CH2PPh2)(2) acts as a bidentate ligand through two phosphorus atoms. The Co-P distances of 2.3666(14) and 2.3731(15) A found in 1 are significantly longer than general Co-P bond lengths. The incoordinate N atom of the ligand locates at the apical position trans to one of the chlorides. The catalytic properties of 1 and 2 in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization were studied, The activities of 89.4 kg oligomers mol(-1) Co h(-1) for 1 and 81.2 kg oligomers mol(-1) Fe h(-1) for 2 (100 equivalents of EAO, 180 degreesC and 1.8 MPa ethylene) were observed with high selectivity to linear C4-10 olefins. (C) 2002 Elsevier Science B.V. All rights reserved.