DESIGN, SYNTHESES AND APPLICATION OF NEW PHOSPHINE AND DITHIOPHOSPHINATE COMPLEXES OF NICKEL - CATALYST PRECURSORS FOR THE OLIGOMERIZATION OF ETHYLENE

Several new nickel(II) and nickel(0) complexes have been prepared whic h are active and selective for the oligomerization of ethylene to high er alpha-olefins. Nickel(II) complexes of the type NiCl(PR3)S2PR2' (R = Ph, Bu; R' = Me, Ph) contain one bound halide ion, a monodentate pho sphine, and a bidentate chelating dithiophosphinate ligand. The single -crystal X-ray structure of NiCl(PPh3)S2PMe2 is reported. Crystal data : triclinic, space group P (1) over bar (No. 2), a = 10.288 (2) Angstr om, b = 13.205 (3) Angstrom, c = 16.157 (2) Angstrom, alpha = 82.63(1) degrees, beta = 88.29(1)degrees, gamma = 78.87(2)degrees, Z = 4. Final R and R-W values were 0.042 and 0.048, respectively. There are two in dependent molecules A and B in the unit cell. In each case the molecul ar structure is based on a distorted square planar Ni(II) center subte nded with a slightly asymmetrically bound chelated dithiophosphinate l igand with a relatively tight binding angle (S-Ni-S 87.4 degrees). Mol ecule A is slightly more distorted from the square planar geometry (in that the P(V) of the dithiophosphinate chelate deviates more signific antly from the coordination plane) than B. The bond distances (Ni-S (a v) (trans to Cl) 2.205(2) Angstrom, Ni-S (av) (trans to the phosphine ligand) 2.254(5) Angstrom, Ni-Cl (av) 2.179(5) Angstrom and Ni-P (ave) 2.021(3) Angstrom) do not differ significantly in the two molecules. Also prepared were the nickel(0) complexes Ni(Ph2P-N=C(H)Ph)(4) and Ni (Ph2PCH2P(Ph-2)NC6F4CN)(2). Each of the complexes is more active for t he oligomerization of ethylene than are comparable conventional comple xes of nickel with typical phosphine ligands. Batch reactions of the n ickel complexes in combination with a 150 times molar excess of EtnAlC l3-n in toluene oligomerized ethylene at temperatures below 25 degrees C under 0.1-2.8 MPa of ethylene and a lesser amount of inert gas. The catalyst mixtures have high activity (for example, a rate of 7.64 x 1 0(5) mol of C-2(mol of cat)(-1) h(-1) was observed for Ni(Ph(H)NCPPh2) (4) with excess diethylaluminum chloride cocatalyst) and high selectiv ity to alpha-olefins, in particular 1-butene. The selectivity to 1-but ene increases with increasing olefin pressure.