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The generation and properties of nonchelated [d.sup.0] zirconocene-anyl-alkene and alkyne adducts that are stabilized by the presence of beta-Si[Me.sub.3] substituents on the substrates and the weak nucleophilicity of the -[C.sub.6][F.sub.5] ligand are described. The allytrimethylsilane abducts are found to undergo nondissociative alkene face exchange on the nucleomagnetic resonance scale.

An attempt is made to study the nonchelated alkene complexes of the [d.sup.0]-metal species, to probe the [Zr.sup.IV]-alkene interaction. Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the [beta]-Si effect.

The reactions of vinyl chloride (VC) with representative late metal, single-site olefin dimerization and polymerization catalysts are investigated. Termination of chain growth by beta-Cl eliminations is the most significant obstacle of metal-catalyzed insertion polymerization of VC.

Tetraaza macrocycle complexes, (Me4taen)Zr(O(super t)Bu)2 (4) and (Me4taen)Hf(NMe2)2 (5), crystallize in triclinic space groups, and have a cis stereochemistry. The central metal atom has a distorted octahedral metal geometry. (Me4taen)ZnCl2 (1) and (Me4taen)Zr(CH2Ph)2 (2) have trigonal prismatic structures. The complexes 1 and 2 have no pi-component in the M-X covalent bond. The electronic characteristics help in determining the structures of these (Me4taen)MX2 species.

An efficient route to chiral ansa-metallocenes of the type rac-(EBI)ZrX2 where (EBI = ethylene-1,2-bis 1-indenyl) and (X = NMe2,Cl,Me) was developed. The procedure is stereoselective because it involves a reversible amine elimination reaction in toluene between the amide Ze(NMe2)4 and (EBI)H2, otherwise known as 1,2-bis 3-indenyl(ethane). Moreover, the ratio of the rac-(EBI)Zr(NMe2)2 to the meso-(EBI)Zr(NMe2)2 products may be controlled by modifying the reaction conditions.

(PPN)(Tl(C2B9H11)) reacts with (C2B9H11)TaCl3 in a medium of CH2Cl2 to produce (PPN)((C2B9H11)2TaCl2) having a bent-metallocene structure. This complex helps prepare two other complexes having a bent-metallocene structure analogous to those of Cp2MX2 complexes. X-ray and multinuclear NMR studies help characterize these anionic tantalum(V)bis(dicarbollide) complexes.

The d0 carbonyl complex Cp2Zr(CH)(Me)(6-ethlpyrid-2-yl))+ (compound 3) results from the carbonylation of the four-membered cationic azazirconacyle. A terminal CO ligand is evident for compound 3. A chelated structure in Zr(CH(Me)(6-ethylpyrid-2-yl) ligand is evident. In the case of azazirconacyle, back-bonding from only a single bonding orbital is possible.

The zirconocene cationic complex Cp2Zr(Me)(THF)+ mediates the one-pot addition of alkynes to alkylpyrazines in the presence of a proton source. The reaction forms (E)-alkenyl-substituted alkylpyrazines in very high (61-92%) yields. The mechanism involves sequential ortho C-H activation and alkyne insertion, with the stereoselectivity arising from alkyne insertion into the Zr-C bond of the intermediate. Terminal and Me3Si-substituted alkynes give products with the substituent placed on the beta-alkenyl carbon.

Several prominent interactions are seen in neutral eta2-(iminoacyl) complexes of initial transition metals, including isocyanide deinsertion, 1,2-hydrogen shifts, and inter- or intramolecular incorporation and pairing reactions. Nonpolar unsaturated substrates reveal interactions which are unknown. An alternating multiple addition of alkynes and carbon monoxide is conducted on Cp2Zr((eta2-C,O-C double bond O)R)(L)+ eta2-acyl complexes. This reaction is useful in the production of synthetic utilities of Cp2Zr(R)(L)+ complexes. Increased sensitivity is revealed by analogous cationic eta-2-(iminoacyl) species.

([alpha]-Diimine)Pd[Cl.sup.+] species have catalytically dimerized alkyl and silyl vinyl ethers to [beta],[gamma]-unsaturated C[H.sub.2]CHC[H.sub.2]CH[(OR).sub.2] acetals and they have cyclized divinyl ethers to analogous cyclic acetals. ([alpha]-Diimine)Pd[Cl.sup.+] species are used to initiate ethylene polymerization in the presence of vinyl ethers.

The reactions of ([alpha]-diimine)Pd[Me.sup.+] species are examined. [beta]-OR elimination of the mixtures is faster for Sb[F.sub.sup.-] salts than B[([C.sub.6][F.sub.5]).sub.4.sup.-] salts and the implications of the results for olefin/vinyl ether copolymerization are discussed.

The article discusses the synthesis and the properties of the various self-assembled tetranuclear palladium catalysts, which are shown to be extremely useful for the production of high molecular weight linear polyethylene. The polymer is found to exhibit high molecular weight due to the presence of tetrameric assembly in its structure.

([alpha]-Diimine)Pd[Me.sup.+] species ([alpha]-diimine = (2,6-[super i][Pr.sub.2]-[C.sub.6][H.sub.3])N[double bond]CMeCMe[double bond]N(2,6-[super i][Pr.sub.2]-[C.sub.6][H.sub.3])) have undergone up to three sequential insertions of a silyl vinyl ether, thus forming Pd allyl products. The studies have shown that steric crowding might inhibit chain growth.

(Phosphine-sulfonate)Pd(Me)(pyridine) catalysts have incorporated low levels of vinyl fluoride (VF) in ethylene polymerization. The studies have shown that it is possible to increase the polymerization rate and VF incorporation level by modification of the catalyst.

The mechanism of alkyne insertion in a [Cp.sub.2]Zr[(aryl).sup.+] system is analyzed. This method has helped in proving the influence of the properties of the [Cp.sub.2]M unit on alkyne binding and insertion in [Cp.sub.2]M[(aryl).sup.+] species.

The MAO activation of group 4 Tp'MCl(sub 3) complexes that contain sterically bulky tris(pyrazolyl)borate ligands (Tp') generates highly active ethylene polymerization catalysts with interesting properties. Tris(pyrazolyl)borate zirconium benzyl complexes can be generated at low temperature and rearranges rapidly at 0 degree Celsius to the bis(pyrazolyl)borate complex.

The reactions of acrylonitrile (AN) with 'L(sub 2)PdMe(super +)' species were investigated. The results show that most important obstacles to insertion polymerization or copolymerization of AN using L(sub 2)PdR(super +) catalysts are the tendency of L(sub 2)Pd{CH(CH)CH(sub 2)R}(substrate)(super +) species.

The structures and reactivity of LnM(eta1-XR) halocarbon complexes of group 6-11 metals is studied. The result shows that (C5R5)2ZrR'+ species can be stabilized by intermolecular and intramolecular coordination.

X-ray crystallographic studies show that the Zr{PhN(CH2)3(sub 3)NPh} rings in Zr{PhN(CH2)3(sub 3)NPh}Cl2(THF)2 and (C5H5)(sub 2)-Zr{PhN(CH2)(sub 3)NPh} adopt twist conformations that position the N-Ph groups on opposite sides of the N-Zr-N plane. rac-(XBI)Zr{PhN(CH2)3NPh} are converted to the corresponding rac-(XBI)ZrCl2 complexes by reaction with HCl.