A series of palladium/alkylphosphine-sulfonate catalysts were synthesized and examined in the homopolymerization of ethylene and the copolymerization of ethylene and polar monomers. Catalysts with alkylphosphine-sulfonate ligands containing sterically demanding alkyl substituents afforded (co)polymers whose molecular weight was increased by up to 2 orders of magnitude relative to polymers obtained from previously reported catalyst systems. The polymer molecular weight was found to be closely correlated to the Sterimol B5 parameter of the alkyl substituents in the alkylphosphine-sulfonate ligands. Thus, the use of bulky alkylphosphine-sulfonate ligands represents an effective and versatile method to prepare high-molecular-weight copolymers of ethylene and various polar monomers, which are difficult to obtain by previously reported methods.

Coordination-insertion copolymerization of allyl monomers with ethylene was developed by using a palladium/phosphine-sulfonate catalyst. A variety of allyl monomers, including allyl acetate, allyl alcohol, protected allylamines, and allyl halides, were copolymerized with ethylene to form highly linear copolymers that possess in-chain -CH(2)CH(CH(2)FG)- units.

An air- and moisture-stable nickel(II) complex of bis-carbene pincer complex 2 has been synthesized, and its catalytic activity for the Heck reaction and the Suzuki coupling reaction was investigated.

A series of palladium complexes bearing a bisphosphine monoxide with a methylene linker, that is, [κ 2 -(Pd/ BPMO), were synthesized and evaluated as catalysts for the homopolymerization of ethylene and the copolymerization of ethylene and polar monomers. X-ray crystallographic analyses revealed that these Pd/BPMO complexes exhibit significantly narrower bite angles and longer Pd−O bonds than Pd/BPMO complexes bearing a phenylene linker, while maintaining almost constant Pd−P bond lengths. Among the complexes synthesized, menthyl-substituted complex 3f (R 1 = (1R,2S,5R)-2-isopropyl-5-methylcyclohexan-1-yl; R 2 = Me) showed the best catalytic performance in the homo-and copolymerization in terms of molecular weight and polymerization activity. Meanwhile, complex 3e (R 1 = t-Bu; R 2 = Me) exhibited a markedly higher incorporation of comonomers in the copolymerization of ethylene and allyl acetate (≤12.0 mol %) or methyl methacrylate (≤0.6 mol %). The catalytic system represents one of the first examples of late-transition-metal complexes bearing an alkylene-bridged bidentate ligand that afford high-molecular-weight copolymers from the copolymerization of ethylene and polar monomers.

Carbene Catalyst. -A combination of Ni(acac)2 and a precursor of a N-heterocyclic carbene generates an effective catalyst for the Heck reaction. -(INAMOTO*, K.; KURODA, J.-I.; DANJO, T.; SAKAMOTO, T.; Synlett 2005, 10, 1624-1626; Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, Japan; Eng.) -Mais 48-092