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The discrete (phosphinoarenesulfonate)Pd fluoride complex (POBp,OMe)PdF(lutidine), where POBp,OMe=(2-MeOC6H4)(2-{2,6-(MeO)2C6H3}C6H4)(2-SO3-5-MeC6H3)P, inserts vinyl fluoride (VF) to form (POBp,OMe)PdCH2CHF2(lutidine) and inserts multiple ethylene (E) units to generate polyethylene that contains −CH2F chain ends. These results provide strong evidence that the −CHF2 and −CH2F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β-F elimination of Pd(β-F-alkyl) species, VF or E insertion of the resulting (PO)PdF species, and subsequent chain growth. These results also imply that β-F elimination is not an important catalyst deactivation reaction in this system. [ABSTRACT FROM AUTHOR]

Abstract: The ethylene polymerization and ethylene/α-olefin copolymerization behavior of the sterically crowded tris(pyrazolyl)borate group 4 metal complexes TpMs*TiCl3 (1, TpMs* =HB(3-mesitylpyrazolyl)2(5-mesitylpyrazolyl)−), {K[TpMs*TiCl3]}2 (2), TpMs*TiCl2(O-2,4,6-tBu3-Ph) (3), TpMs*ZrCl3 (4), TpMsZrCl3 (5, TpMs =HB(3-mesitylpyrazolyl)3 −), and TpMs*HfCl3 (6) were studied with dried-MAO activation in toluene solution. These catalysts all produce very high molecular weight (M v >106) linear polyethylene. Zirconium catalyst 5 excels in productivity in ethylene homopolymerization and ethylene/1-hexene copolymerization, molecular weight, and hexene incorporation ability. Catalyst 5 produces moderately alternating ethylene/1-hexene copolymer (41mol% hexene) with ultra-high molecular weight (M w =1.3×106), narrow molecular weight distribution (M w/M n =2.2) and narrow composition distribution with high efficiency. [Copyright &y& Elsevier]

The reaction of Cp′2Zr(OtBu)Me (Cp′ = C5H4Me) and [Ph3C][B(C6F5)4] yields the base-free complex [Cp′2Zr(OtBu)][B(C6F5)4] (6), which exists as Cp′2Zr(OtBu)(CIR)+ halocarbon adducts in CD2Cl2 or C6D5Cl solution. Addition of alkenes to 6 in CD2Cl2 solution at low temperature gives equilibrium mixtures of Cp′2Zr(OtBu)(alkene)+ (12aI), 6, and free alkene. The NMR data for 12aI are consistent with unsymmetrical alkene bonding and polarization of the alkene CC bond with positive charge buildup at Cint and negative charge buildup at Cterm. These features arise due to the lack of dπ* back-bonding. Equilibrium constants for alkene coordination to 6 in CD2Cl2 at -89 °C, Keq = [12][6]-1[alkene]-1, vary in the order: vinylferrocene (4800 M-1) ⪢ ethylene (7.0) ≈ α-olefins > cis-2-butene (2.2) > trans-2-butene (<0.1). Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the β-Si effect. Compounds 12aI undergo two dynamic processes: reversible alkene decomplexation via associative substitution of a CD2Cl2 molecule, and rapid rotation of the alkene around the metal-(alkene centroid) axis. [ABSTRACT FROM AUTHOR]

Reports on the facile insertion reaction of a cationic iminoacyl species with alkynes and alkenes which offer an efficient method for the regioselective acetylation of these substrates. Reactions with nonpolar unsaturated substrates; Effort to develop synthetic applications of Cp2Zr(R)(L)+ complexes; Indication of isomer interconversion.

This article focuses on the reactivity of pyrazolyl borate zirconium benzyl complexes. The activation of group 4 complexes that contain sterically bulky tris-(pyrazolyl) borate ligands, generates highly active ethylene polymerization catalysts with interesting properties, including the production of ultra-high molecular weight polyethylene and high hexene incorporation in ethylene/hexene copolymerization. These studies show that this compound can be generated at low temperature and rearranges rapidly to the bis-(pyrazolyl) borate complex.

This article presents information on a study involving alkyne and alkene complexes of a d0 zirconocene aryl cation. (C5R5)2Zr(R)(alkyne)+ and (C5R5)2Zr(R)(alkene)+ complexes are probable key intermediates in zirconocene-catalyzed alkyne oligomerization and alkene polymerization. These species are challenging to study because the insertion of the substrate into the Zirconium and complexes is fast. X-ray and NMR studies of chelated complexes were conducted.

Discusses the coordination of alkenes and alkynes to a cationic d[sup 0] zirconocene alkoxide complex. Synthesis of base-free (C[sub 5]R[sub 5])[sub 2]Zr(O'Bu)[sup +] cations; Observation of nonchelated alkene and alkyne adducts of (C[sub 5]R[sub 5])[sub 2]Zr(O'Bu)[sup +] cations.

Describes a strategy for the synthesis of Cp2Zr(X)(olefin)+ complexes. Generation of alkoxide complexes using alcoholysis; Molecular structure.

Studies the stereoselective olefin reactions of Brintzinger's C2-symmetric ansa zirconocene complexes and (EBHTHI)ZrCl2. Stereodirecting properties of ch Cp2M frameworks; Steric interactions between a pyridal ortho substituent and EBI C6 ring.

The reactions of three types of group 4 metal olefin polymerization catalysts, (C[sub 5]R[sub 5])[sub 2]ZrX[sub 2]/activator, (C[sub 5]Me[sub 5])TiX[sub 3]/MAO (MAO = methylalumoxane), and (C[sub 5]Me[sub 4]SiMe[sub 2]N[sup t]Bu)MX[sub 2]/activator (M = Ti, Zr), with vinyl chloride (VC) and VC/propylene mixtures have been investigated. Two general pathways are observed: (i) radical polymerization of VC initiated by radicals derived from the catalyst and (ii) net 1,2 VC insertion into L[sub n]MR[sup +] species followed by β-Cl elimination, rac-(EBI)ZrMe(µ-Me)B(C[sub 6]F[sub 5])[sub 3] (EBI = 1,2-ethylenebis(indenyl)) reacts with 2 equiv of VC to yield oligopropylene, rac-(EBI)ZrCl[sub 2], and B(C[sub 6]F[sub 5])[sub 3]. This reaction proceeds by net 1,2 VC insertion into rac-(EBI)ZrMe[sup +] followed by fast β-Cl elimination to yield [rac-(EBI)ZrCl][MeB(C[sub 6]F[sub 5])[sub 3]] and propylene. Methylation of rac-(EBI)ZrCl[sup +] by MeB(C[sub 6]F[sub 5])[sub 3, sup -] enables a second VC insertion/β-Cl elimination to occur. The evolved propylene is oligomerized by rac-(EBI)ZrR[sup +] as it is formed. At high Al/Zr ratios, rac-(EBI)ZrMe[sub 2]/MAO catalytically converts VC to oligopropylene by 1,2 VC insertion into rac-(EBI)ZrMe[sup +], β-Cl elimination, and realkylation of rac-(EBI)ZrCl[sup +] by MAO; this process is stoichiometric in Al-Me groups. The evolved propylene is oligomerized by rac-(EBI)ZrR[sup +]. Oligopropylene end group analysis shows that the predominant chain transfer mechanism is VC insertion/β-Cl elimination/ realkylation. In the presence of trace levels of O[sub 2], rac-(EBI)ZrMe[sub 2]/MAO polymerizes VC to poly(vinyl chloride) (PVC) by a radical mechanism initiated by radicals generated by autoxidation of Zr-R and/or Al-R species. Cp[sup *]TiX[sub 3]/MAO (Cp[sup *] = C[sub 5]Me[sub 5]; X = OMe, Cl) initiates radical polymerization of VC in CH[sub 2]Cl[sub 2] solvent at low Al/Ti ratios under anaerobic conditions... [ABSTRACT FROM AUTHOR]

The article presents information on the mechanism of alkyne insertion. In metallocene-catalyzed alkene polymerization and alkyne oligomerization, chain growth proceeds by the coordination of substrate followed by migratory insertion. Due to weak coordination and low insertion barriers, substrate adducts are transient species and there has not been any direct observation on them.

The phosphine-bis-arenesulfonate ligands PR²(2-SO3Li-5-R¹-Ph)(2-SO3--5-R¹-Ph) (Li[OPO-]; Li[1a-e], a: R¹ = Me, R² = Ph, b: R¹ = iPr, R² = Ph, c: R¹ = Cy, R² = Ph, d: R¹ = tBu, R² = Ph, e: R¹ = R² = tBu, f: R¹ = R² = Cy) coordinate as κ²-P,O chelators in (Li-OPO)PdMeL complexes (4a-c,f: L = 4-(5-nonyl)pyridine = py′; 5b-d: L = py; 2e: L = py′). 4a-c,f and 5b-d self-assemble into tetrameric structures in which four (Li-OPO)PdMeL units are arranged around a cubic Li4S4O12 cage formed from the four non-Pd-bound ArSO3Li units and one oxygen from each of the Pd-bound ArSO3- units. The {(Li-OPO)PdMeL}4 assemblies are in equilibrium with monomeric (Li-OPO)PdMeL species in CD2Cl2 and CDCl2CDCl2 solution. Crystallization of 2e from a toluene/pentane mixture at −40 °C yields a trimeric C1-symmetric assembly (6e) in which three (Li-1e)PdMe(py′) units are held together by a Li3S3O9 core. Crystallization of 2e from toluene/pentane at room temperature results in partial loss of py′ and formation of a Pd6 assembly, {(Li-1e)PdMe(py′)}4{(Li-1e)PdMe}2 (7e). 4a-c,f, 5b-d, and 2e exist as monomeric (Li-OPO)PdMeL complexes in CD3OD solution, and under these conditions exchange of the Pd-bound and non-Pd-bound ArSO3- units is much faster for 4a,c (ΔG⧧ = 12.3, 12.2 kcal/mol at −10 °C) than for 2e (ΔG⧧ = 19.2 kcal/mol at 24 °C). This difference in molecular rigidity may contribute to the differences in the self-assembly behavior of these compounds. 4a,f and 5b catalyze the polymerization of ethylene to linear polyethylene. The molecular weight and molecular weight distribution of the polymer are strongly influenced by the extent of dissociation of the Pd4 cage under the polymerization conditions. [ABSTRACT FROM AUTHOR]

The reactions of acrylonitrile (AN) with "L2PdMe+" species were investigated; (L2 = CH2(N-Me-imidazol-2-yl)2 (a, bim), (p-tolyl)3CCH(N-Me-imidazol-2-yl)2 (b, Tbim), CH2(5-Me-2-pyridyl)2 (c, CH2py'2), 4,4'-Me2-2,2'-bipyridine (d), 4,4'-tBu2-2,2'-bipyridine (e), (2,6-iPr2-C6H3)N=CMeCMe=N(2,6-iPr2-C6H3) (f)). [L2PdMe(NMe2Ph)][B(C6F5)4] (2a-c) and [{L2PdMe}2(μ-Cl)][B(C6F5)4] (2d-f) react with AN to form N-bound adducts L2Pd(Me)(NCCH=CH2)+ (3a-f). 3a-e undergo 2,1 insertion to yield L2Pd{CH(CN)Et}2, which form aggregates [L2Pd{CH(CN)Et}]nn+ (n = 1-3, 4a-e) in which the Pd units are proposed to be linked by PdCHEtCN- - -Pd bridges. 3f does not insert AN at 23°C. 4a-e were characterized by NMR, ESI-MS, IR and derivatization to L2Pd{CH(CN)Et}(PR3)+ (R = Ph (5a-e), Me (6a-c)). 4a,b react with CO to form L2Pd{CH(CN)Et}(CO)+ (7a,b). 7a reacts with CO by slow reversible insertion to yield (bim)Pd{C(=O)CH(CN)Et}(CO)+ (8a). 4a-e do not react with ethylene. (Tbim)PdMe+ coordinates AN more weakly than ethylene, and AN insertion of 3b is slower than ethylene insertion of (Tbim)Pd(Me)(CH2=CH2)+ (10b). These results show that most important obstacles to insertion polymerization or copolymerization of AN using L2PdR2 catalysts are the tendency of L2Pd{CH(CN)CH2R}+ species to aggregate, which competes with monomer coordination, and the low insertion reactivity of L2Pd{CH(CN)CH2R}(substrate)+ species. [ABSTRACT FROM AUTHOR]

The reactions of vinyl chloride (VC) with representative late metal, single-site olefin dimerization and polymerization catalysts have been investigated. VC coordinates more weakly than ethylene or propylene to the simple catalyst (Me[sub 2]bipy)PdMe[sup +] (Me[sub 2]bipy = 4,4'-Me[sub 2]-2,2'-bipyridine). Insertion rates of (Me[sub 2]bipy)Pd(Me)(olefin)[sup +] species vary in the order VC > ethylene > propylene. The VC complexes (Me[sub 2]bipy)Pd(Me)(VC)[sup +] and (α-diimine)Pd(Me)(VC)[sup +] (α-diimine = (2,6-[sup j]Pr[sub 2]-C[sub 6]H[sub 3])N=CMeCMe=N(2,6-[sup i]Pr[sub 2]-C[sub 6]H[sub 3])) undergo net 1,2 VC insertion and β-CI elimination to yield Pd-CI species and propylene. Analogous chemistry occurs for (pyridine-bisimine)MCI[sub 2]/MAO catalysts (M = Fe, Co; pyridine-bisimine = 2,6-{(2,6[sup i]Pr[sub 2]-C[sub 6]H[sub 3])N=CMe}[sub 2]-pyridine) and for neutral (sal)Ni(Ph)PPh[sub 3] and (P-O)Ni(Ph)PPh[sub 3] catalysts (sal = 2-{C(H)=N(2,6-[sup i]Pr[sub 2] C[sub 6]H[sub 3])}-6-Ph-phenoxide; P-O = {Ph[sub 2]PC(SO[sub 3]Na)=C(p-tol)O}), although the initial metal alkyl VC adducts were not detected in these cases. These results show that the L[sub n]MCH[sub 2]CHCIR species formed by VC insertion into the active species of late metal olefin polymerization catalysts undergo rapid β-CI elimination which precludes VC polymerization. Termination of chain growth by β-CI elimination is the most significant obstacle to metal-catalyzed insertion polymerization of VC. [ABSTRACT FROM AUTHOR]

Investigates the polymerization of olefins by transition metal catalysts. Influence of L[sub n]M steric and electronic characteristics on metal-olefin bonding; Design and application of the catalysts; Features of chelated d[sub 0] metal-olefin complexes.