DINUCLEAR PHOSPHIDO-BRIDGED AND ARSENIDO-BRIDGED EARLY LATE TRANSITION-METAL COMPLEXES - EFFICIENT CATALYSTS FOR ETHYLENE POLYMERIZATION/

The reaction of (eta(5)-C5H5)(2)Zr{P(SiMe(3))(2)}(2) with Ni(CO)(4) yi elds the heterodinuclear phosphido-bridged complex (eta(5)-C5H5)(2)Zr{ mu-P(SiMe(3))(2)}Ni-2(CO)(2) (1), 1 was characterised spectroscopicall y and by X-ray structure determination. The central four-membered ZrP2 Ni ring is slightly puckered (dihedral angle between planes ZrP2/NiP2 = 1.8 degrees). The Zr-P bond lengths are equivalent (Zr-P1 2.655(1), Zr-P2 2.652(1) Angstrom), as are the Ni-P bond lengths (Ni-P1 2.264(1) , Ni-P2 2.266(1) Angstrom). The long Zr ... Ni distance of 3.038(1) An gstrom indicates the absence of a metal-metal bond. The heterodinuclea r phosphido- and arsenide-bridged complexes (eta(5)-C5H5)(2)Zr{mu-E(Si Me(3))(2)}(2) M(CO)(n) [E = P; M(CO)(n) = Ni(CO)(2) (1) or Mo(CO)(4) ( 2); and E = As, M(CO)(n) = Cr(CO)(4) (3)] react rapidly with methylalu minoxane, yielding catalytically active complexes which rival the know n cationic systems for the polymerization of ethylene.