CATALYTIC OLEFIN OLIGOMERIZATION ACTIVITY OF A SERIES OF TRIALKYLPHOSPHINE AND TRIPHENYLPHOSPHINE DERIVATIVES OF THE NICKEL (II) COMPLEXES OF 4-THIOXO-2-PENTANOATE AND 2,4-PENTANEDITHIONATE

A series of complexes of the type [Ni(L)(PR3)X] and [Ni(L)(Ph2P(CH2)(n )27PPh2)]BPh4 (where L = 4-thioxo-2-pentanoate (sacac); R = ethyl (Et) , R = n-butyl((n)Bu); X = Cl, Br, n = 1 or 2; where L = 2,4-pentanedit hionate (sacsac); R = methyl (Me), ethyl (Et), cyclohexyl (Cy) and phe nyl (Ph); X = Cl, Br) has been prepared. The complex [Ni (sacac) (P(n) Bu3) Cl] is extremely labile. However, it could be prepared using ultr asound and identified by NMR. Attempts to recrystallize the complex le ad to disproportionation. Several of the complexes were found to be ac tive oligomerisation catalysts when tested for the oligomerisation of propene and 1-hexene. Factors that have been investigated are the effe ct of changing the Lewis acid co-catalyst, phosphine, chelating ligand (L) and halogen on the oligomerisation reaction. It is found that the phosphine ligand influences both the activity and selectivity of the oligomerisation reaction, whilst changing the thio ligand has a marked effect on catalyst activity only. In addition, the crystal structure of [Ni(C5H7OS) (P(C2H5)3)Cl] has been determined. Crystals of [Ni(C5H7 OS)(P(C2H5)3)Cl] are monoclinic, P2(1)/n with a=7.644(4), b=18.005(8), c=11.021 (3) angstrom, beta=96.17(3)degrees V=1508(5) angstrom3, Z=4. The structure was solved using a Patterson map and refined to R=0.056 for 2227 reflections and 162 parameters. The Ni atom has square-plana r coordination with Cl trans to the sulphur atom of the sacac ligand.