Abstract | dc.description.abstract | Lithium derivatives of substituted cyclopentadiene ligands reacted with CrCl3(THF)(3) in THF solution to afford homodinuclear complexes of the type [{(eta(5)-RCp)CrCl(p-Cl)}2] [R = SiMe3 (1), CH2C(Me)CH2 (2)]. Complex 1 reacts with pyrazole (C3H4N2) to yield the mononuclear half-sandwich complex [(eta(5)-Me3SiCp)CrCl2(pyrazole)] (3). The similar complex [Cp*CrCl2(pyrazole)] (4) was synthesised by reaction of [{Cp*CrCl(mu-Cl)}2] with pyrazole. Complex 2 reacts with bidentate ligands to give binuclear complexes of the type [{(eta(5)-CH2C(Me)CH2Cp)CrCl2}(2)(mu-L-L)] [L-L = Ph2PCH2CH2PPh2 (5), trans-Ph2P(O)CH=CHP(O)Ph-2 (6)]. All complexes were structurally characterised by X-ray diffraction. After reaction with methylaluminoxane these complexes are active in the polymerization of ethylene. At 25 degreesC and 4 bar of ethylene, complex 3 yields polyethylene with a bimodal molecular weight distribution centred at 155,000 and 2000 g/mol. Complex 4 shows similar activity, yielding only the low molecular weight fraction. On the other hand, the binuclear complexes 5 and 6 under the same conditions were three times more active than mononuclear complexes. The melting point of the polymers indicates the formation of linear polyethylene. | en |