Deuterio-ethylene labeling studies on two homogeneous chromium ethylene oligomerization catalysts show that chain propagation proceeds via metallacyclic intermediates; reactions performed in the presence of 1-nonene show no incorporation of the higher olefin, strongly implicating the involvement of large ring metallacycles.

Ethylene polymerization catalyzed by nickel(II) keto-ylide complexes has been performed in water to yield a latex of linear PE. Colloidal stability is highly enhanced by the use of a miniemulsion technique to disperse the catalyst prior contact with the monomer. Latex of typically 200 nm particle diameters and up to 10% solids are generated by this method. The influence of several factors (temperature, pressure, solids) onto the polymerization is studied in detail. The surfactant adsorption isotherms onto these highly crystalline and nonpolar particles are also presented.

A series of co-oligomerization and co-polymerization reactions of C 2 H 4 /C 2 D 4 (1:1) mixtures have been carried out using various transition metal catalysts based on Cr, Co and Fe in combination with MAO. The oligomeric α-olefin products have been analysed by GC and GC/MS and the experimental results have been compared with the theoretical mass spectra derived from mathematical models. Solid polymer samples have been analysed by 13 C{ 1 H} and 13 C DEPT-135 NMR spectroscopy. C 2 H 4 /C 2 D 4 co-oligomerization can be used as a method to differentiate between a metallacyclic or a Cossee-type chain growth mechanism in oligomerization systems. In the case of a metallacyclic mechanism, no H/D scrambling is observed whereas for a Cossee-type mechanism, similar rates of chain propagation and chain termination (β-H elimination) result in rapid H/D scrambling of the C 2 H 4 /C 2 D 4 feed. This method is therefore limited to oligomerization systems and cannot be applied in polymerization systems where the rate of chain propagation is much faster than the rate of chain termination.

Magnesium and zinc complexes of the monoanionic ligands N,N'-bis(2,6-di-isopropylphenyl)triazenide, L1, N,N'-bis(2,6-di-isopropylphenyl)acetamidinate, L2, and N,N'-bis(2,6-di-isopropylphenyl)tert-butylamidinate, L3, have been synthesized, but only L3 possesses sufficient steric bulk to prevent bis-chelation. Hence, the reaction of L1H with excess ZnEt2 leads to the isolation of (L1)2Zn, 1; L1H also reacts with Bu2Mg in Et2O to afford (L1)2Mg(Et2O), 2. Similar reactivity is observed for L2H, leading to the formation of (L2)2Zn, 3, and (L2)2Mg, 4. The reaction of L2H with ZnR2 may also afford the tetranuclear aggregates {(L2)Zn2R2}2O, 5 (R=Me) and 6 (R=Et). By contrast, the tert-butylamidinate ligand was found to exclusively promote mono-chelation, allowing (L3)ZnCl(THF), 7, [(L3)Zn(micro-Cl)]2, 8, (L3)ZnN(SiMe3)2, 9, (L3)MgiPr(Et2O), 10, and (L3)MgiPr(THF), 11, to be isolated. X-ray crystallographic analyses of 1, 2, 3, 4, 5, 6, 8, and 10 indicate that the capacity of L3 to resist bis-chelation is due to greater occupation of the metal coordination sphere by the N-aryl substituents.