Chemical reduction of a series of (η5-thiophene)Mn(CO)3 + complexes (3a−d) under an atmosphere of CO affords dimanganese metallathiacyclic complexes (4 a−d), which have a Mn(CO)4 moiety regioselectively inserted into a C−S bond. Reaction of 4 with H2, the rate of which is strongly influenced by substituents on the thiophene ring, leads to hydrogenolysis of the Mn−C σ-bond and formation of (OC)3Mn(μ-H)(μ-SCRCHCHCHR‘)Mn(CO)3 (8; R, R‘ = H, Me), which contains bridging hydride and thiolate ligands and a Mn−Mn bond. The addition of PhMgBr to 3 occurs at the sulfur to give zwitterionic complexes (6a−c, 14), which undergo regioselective hydrogenolysis of a C−S bond and, in some cases, partial desulfurization with concomitant formation of (OC)4Mn(μ-H)(μ-SPh)Mn(CO)4 (5a). Crystal structures are reported for complexes 4b,d, 5a, 8d, 10, 12c, and 14b,c. It is suggested that the reactions reported herein may be relevant to the general problem of hydrodesulfurization (HDS) of thiophenic molecules.

The activation of a metal alkyl‐free Ni‐based catalyst with B(C6F5)3 was investigated in the polymerization of 1,3‐butadiene. A catalyst of bis(1,5‐cyclooctadiene)nickel (Ni(COD)2)/B(C6F5)3 was found to have high catalytic activity and 1,4‐cis stereoregularity. The catalyst was also found to provide polybutadiene having a molecular weight (Mw) of up to 117,000, even in the absence of AlR3 and MAO. Variations in the mol ratio of B(C6F5)3 to Ni affected catalytic activity, 1,4‐cis stereoregularity, and the Mw of polybutadiene, while the molecular weight distribution (MWD) of polybutadiene showed little correlation with the mol ratio of B(C6F5)3 to Ni. The use of other borane compounds such as B(C6H5)3, BEt3, and BF3 etherate in place of B(C6F5)3 clearly showed the two main functions of B(C6F5)3 in the present catalyst. The high Lewis acidity of B(C6F5)3 enabled it to activate catalytic complexes, thus inducing the polymerization. The steric bulkiness of B(C6F5)3 suppressed chain transfer reactions, contributing to the production of polybutadiene with a high Mw. Kinetic studies showed that the catalyst had an induction period, possibly due to the time needed for the formation of catalytic complexes starting from Ni(COD)2. A plot of −ln (1−X), where X is the fractional conversion, as a function of time resulted in a linear relationship, showing that the present catalyst system followed first‐order kinetics with respect to monomer concentration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1164–1173, 2004

[reaction: see text]. We have demonstrated that a dicobalt octacarbonyl catalyzed double [2 + 2 + 1] carbonylative cycloaddition reaction of triyne can be carried out to yield a novel 5.5.5.6 tetracyclic di-enone system.

Novel 5-5-6 tricyclic compounds containing cyclopentenone have been constructed by the dicobalt octacarbonyl catalyzed tandem [2 + 2 + 1] and [2 + 2 + 2] cycloaddition reaction between a diyne and two phenylacethylene under CO pressure.

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