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SynopsisAbstraction of phosphine from the nickel(I1) P, 0-chelated complexes, Ni[Ph, PCH=C(Ph)O] (Ph)(PPh,), and related species converts them from olefin oligomerization to olefin polymerization catalysts. Phosphine acceptors such as Rh(acetylacetonate)(C2H4)2 or Ni(l,5-cyclooctadiene), are most effective. Alternatively, nickel complexes-in which the phosphine ligand is replaced with weakly coordinated pyridine can be prepared. These active, homogeneous catalysts can be tuned to give either low or high molecular weight, linear low or high density polyethylene. Depending on the diluent, the same catalytic complex can be used as heterogeneous or homogeneous catalyst. They are tolerant of oxygenated, hydroxylic, or polar molecules that would poison normal early transition metal-based Ziegler-Natta catalysts. In fact, the polymerizations can be run in solvents such as ethanol or acetone, but hydrocarbon solvents are preferred.

3929sealed at -196 OC. In preparation for each run, the tube was warmed to -78 OC in a C02/2-propanol bath with shaking to assure the complete formation of Sa. The tube was then warmed to room temperature and placed in the probe of an NMR spectrometer maintained at 28.0 f 0.5 OC. Data sets were collected over 3 half-lives of the reaction. A typical data set consisted of 12 acquisitions at 201.947 MHz with a SW = f1113.58 Hz, a pulse width of 20°, and a 5-s delay between pulses. The progress of the reaction was monitored by integrating the Cp resonances of 5a and 6e at 6 5.4 and 5.15, respectively, vs. the ferrocene resonance at 6 4.1. Acknowledgment.Abstract: The full details of experiments on a homogeneous system which successfully converts completely saturated alkanes into hydridoalkylmetal complexes (M + RH -R-M-H) are reported. Irradiation of (~s-CSMe5)(PMe3)IrH2 (5) in saturated hydrocarbons (R-H) using a 500-W Oriel focused-beam mercury lamp leads to extrusion of H2 and production of the hydrido alkyl complexes (7'-C,Me,)(PMe,)Ir(R)(H). Competition experiments have allowed measurement of the relative rates at which the intermediate formed on H2 loss (presumably the coordinatively unsaturated complex (q5-C5Me5)(PMe3)Ir) reacts with different types of C-H bonds. Relative to cyclohexane (l.O), these are as follows: benzene (4.0), cyclopropane (2.65), cyclopentane (1.6), neopentane (1.14), cyclodecane (0.23), and cyclooctane (0.09). Reductive elimination of hydrocarbon occurs at elevated temperature, regenerating (qS-CsMes)(PMe3)Ir, which may then react with another hydrocarbon acting as solvent; thus the C-H activation process can also be induced thermally. C-H bonds having high bond energies react relatively rapidly; this fact, along with crossover experiments, suggests that radical intermediates are not involved in the C-H activation reaction. Treatment of the hydrido neopentyl complex 8 with CHBr, converts it to the corresponding bromo neopentyl complex 10. This material reacts with HgClz to give neopentylmercuric chloride, which forms neopentyl bromide on reaction with Brz. Thus overall stoichiometric conversion of hydrocarbons to functionalized organic molecules is feasible in this system. The factors which have been presumed to influence the rates of reaction of transition-metal complexes with saturated C-H bonds-notably the need for electron-rich metals and close proximity of reacting centers-are discussed in detail.

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