The complexes [Ni{R1C(S)CRzC(S)R3},] 1 and [Ni{R1C(S)CR2C(S)R3}(PL1LZL3)X] 2 (R, L = alkyl, aryl or CF, ; X = CI, Br or I) have been prepared. The complexes 2 can be chemically anchored t o polystyrene or silica-alumina supports via pendant phosphine ligands to form the derivatives 3. The species 2 and 3 in combination with a suitable co-catalyst form extremely active catalysts for the oligomerization of ethylene, propylene or butenes. The immobilised systems show no significant signs of leaching after 24 h operation. In general the oligomerization is highly selective to dimers, however, selectivity and catalyst activity are markedly affected by changes in L. Changes in R affect catalyst activity only.Catalytic dimerization/oligomerization is a useful method for the conversion of moderately cheap lower molecular weight (i.e., C2-C4) feed olefins into industrially important olefins of higher molecular weight. The use of organometallic complexes in catalysts for this purpose has been widely studied'-' and several processes have been commercialised.*-' O Branched products from the dimerization and co-dimerization of propylene and butylene are suitable as gasoline blending components. Linear products from the dimerization and oligomerization of C3-C, olefins are desirable for the production of c&', plasticiser and detergent range olefins.We have been seeking new olefin oligomerization catalysts which give improved turnover numbers (i,e., number of converted substrate molecules per active site on the catalyst per unit time) and/or improved selectivity or specificity as to the type or variety of the dimer(s) or oligomer(s) produced from a particular olefin feedstock. Nickel( 11) complexes of the formula [Ni( R ' C(S)CR 2C( S)R 3, -(PL'L2L3)X] 2 (R, L = alkyl, aryl or CF,; X = C1, Br or I) containing dithioacetylacetonate (sacsac) or substituted derivatives form extremely active and highly selective catalysts for the oligomerization of lower olefins when activated by an appropriate co-catalyst. R3' 2The compounds [Ni(sacsac)( PEt,)Cl], [Ni( MeC(S)C(CH 2-CH=CH,)C(S)Me)(PEt,)Cl] and [Ni(sacsac)(PBu,)Cl] have been reported previously and their crystal structures determined. ' '-' ,

of 8 to (Z)-dichloroethylene to give 9 (80%) was accomplished with Pd(PPh3)4/CuI/n-BuNH2.1 234 Protection of 9 (t-BuMe^iOTf/NEt3/CH2Cl2) gave 10 (70%), which was coupled to methyl propargyl ether [Pd(PPh3)4/CuI/n-BuNH2] to give 11 (88%). Selective removal of the MEM ether from 11 using Me2BBr5 at -35 °C gave 12 (99%), from which the derived f-BuMe2Si-ether 13 (94%) (t-BuMe2SiOTf/NEt3) was prepared. When 13 was treated with Co2(CO)8/heptane, the adduct 14 was isolated in 90% yield. Exposure of 14 to TiCl4 (3.0 equiv)/ DABCO (1.0 equiv)/-43 °C to -35 °C gave the bicyclo [7.3.1] ynene-10,11 -dicobalt hexacarbonyl adduct 15 (50%) as a crystalline material. Figure 1 shows an ortep representation of 156 and a small amount (ca. 10%) of the -ketol shift isomer 16.7 Decomplexation of 15 using conditions (I2/PhH) that aromatize 2 gave the 13-ketobicyclo [7.3.1] diyene 5 (70%) as a reasonably stable crystalline compound, Figure 2.6 In going from the cobalt adduct 15 to the diynene 5 the conformation of the cyclohexanone ring changes from a chair to a boat. The bond angles C-6,7,8 and C-9,10,11 in 5 are substantially bent, 168.7°and 165.7°, respectively. In contrast, the double bond angles are 118.95°and 119.13°, which indicates that the strain in 5 is accommodated by the weak bending modes of the triple bonds.8 When 5 was heated in 1,4-cyclohexadiene at reflux (82 °C) for 48 h, the benzenoid derivative 6 was isolated in 72% yield. This should be Supplementary Material Available: Spectroscopic data (IR, and 13C NMR, and HRMS) on compounds 5, 6,15, and 20 and X-ray crystallographic data on compounds 5 and 15 (11 pages). Ordering information is given on any current masthead page.

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