LIGAND DONOR ATOM AND SUBSTITUENT EFFECTS IN OLEFIN OLIGOMERIZATION AND ISOMERIZATION CATALYZED BY NICKEL-BASED CATALYST SYSTEMS

The olefin oligomerization and isomerization catalytic activities and selectivities of catalysts generated by combining [Ni(RC(X)CHC(Y)R)2]n (R = Me, X = Y = O,n = 3; X = O, Y = NH, n = 1; X = O, Y = S, n = 1; X = Y = S, n = 1; and R = Bu(t), n = 1, X = Y = O; X = O, Y = S; X = Y = S) and [Ni(CH3C(S)CHC(S)CH3)(PR3)Cl] (R = alkyl, aryl) precursors with [Et6-xAl2Clx] (x = 0, 2, 3, 4, 6) co-catalysts have been compared. All catalysts exhibit some olefin isomerization activity, but only those generated from precursors containing oxygen-donor ligands exhibit olefin oligomerization activity. Olefin oligomerization is also favoured by the use of [EtAlCl2]2 as a co-catalyst. Almost no activity for either olefin oligomerization or isomerization was observed when using [Ni(CH3 C(S)CHC(S)CH3)2] as a catalyst precursor. However, extremely active olefin oligomerization and isomerization catalysts could be generated from [Ni(CH3C(S)CHC(S)CH3)(PBu3)Cl] and appropriate co-catalysts. The molecular weight of the products could be controlled in these systems by varying the co-catalyst. The catalysts with the most sustained high activity were those generated from [Ni(CH3C(S)CHC(S)CH3)(PBu3)Cl].