37565-93-8Relevant articles and documents
Design, Syntheses and Application of New Phosphine and Dithiophosphinate Complexes of Nickel: Catalyst Precursors for the Oligomerization of Ethylene
Cavell, Ronald G.,Creed, Beth,Gelmini, Lucio,Law, David J.,McDonald, Robert,Sanger, Alan R.,Somogyvari, Arpad
, p. 757 - 763 (2008/10/08)
Several new nickel(II) and nickel(0) complexes have been prepared which are active and selective for the oligomerization of ethylene to higher α-olefins. Nickel(II) complexes of the type NiCl(PR3)S2PR'2 (R = Ph, Bu; R' = Me. Ph) contain one hound halide ion, a monodentate phosphine, and a bidentate chelating dithiophosphinate ligand. The single-crystal X-ray structure of NiCl(PPh3)S2PMe2 is reponed. Crystal data: triclinic, space group P1 (No. 2), a = 10.288 (2) A?, b = 13.205 (3) A?, c = 16.157 (2) A?, α = 82.63(1)°, β = 88.29(1)°, γ = 78.87(2)°, Z = 4. Final R and Rw values were 0.042 and 0.048, respectively. There are two independent molecules A and B in the unit cell. In each case the molecular structure is based on a distorted square planar Ni(II) center subtended with a slightly asymmetrically bound chelated dithiophosphinate ligand with a relatively tight binding angle (S-Ni-S 87.4°). Molecule A is slightly more distorted from the square planar geometry (in that the P(V) of the dithiophosphinate chelate deviates more significantly from the coordination plane) than B. The bond distances (Ni-S (av) (trans to Cl) 2.205(2) A?, Ni-S (av) (trans to the phosphine ligand) 2.254(5) A?, Ni-Cl (av) 2.179(5) A and Ni - P (ave) 2.021(3) A?) 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(Ph2)NC6F 4CN)2. Each of the complexes is more active for the oligomerization of ethylene than are comparable conventional complexes of nickel with typical phosphine ligands. Batch reactions of the nickel complexes in combination with a 150 times molar excess of EtnAlCl3-n in toluene oligomerized ethylene at temperatures below 25 °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 × 105 mol of C2(mol of cat)-1 h -1 was observed for Ni(Ph(H)NCPPh2)4 with excess diethylaluminum chloride cocatalyst) and high selectivity to α-olefins, in particular I-butene. The selectivity to 1-butene increases with increasing olefin pressure.
