Novel Rh complexes, Rh[C(C 6H5)dC(C6H5)2](nbd)(4-XC6H4)3P (1a: X ) F; 1b: X ) Cl), were isolated from mixtures of [(nbd)RhCl]2, (C6H5)2CdC(C6H5)Li, and (4-XC6H4)3P, and the polymerization of phenylacetylene thereby was investigated. The polymerization by 1a in toluene at 30 °C in the presence of (4-FC6H4)3P (5 equiv to Rh or more) proceeded with virtually quantitative initiation efficiency to give polymer with low polydispersity (Mw/Mn ∼1.05). The living character of this polymerization was confirmed by means of both the time profile of polymerization and the multistage polymerization. Toluene, benzene, and THF were particularly useful as polymerization solvents; the polydispersity remained 1.05-1.06, while the larger the dielectric constant of the solvent, the slower the polymerization. This polymerization smoothly proceeded in the temperature range 15-60 °C.

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It was proved that a Rh‐based ternary catalyst composed of [(nbd)RhCl]2 (nbd: bicyclo[2.2.1]hepta‐2,5‐diene), (triphenylvinyl)lithium, and triphenylphosphine induces living polymerization of phenylacetylene. [(nbd)RhCl]2 was effective as the main catalyst, whereas neither [(cod)RhCl]2 (cod: 1,5‐cyclooctadiene) nor [(coe)2RhCl]2 (coe: cyclooctene) induced living polymerization. The anionic ligands such as chlorine, methoxy, and acetoxy groups in the Rh complex hardly affected the living polymerization. When vinyllithium as second catalyst component possessed a bulky substituent such as phenyl or t‐butyl group on its α‐carbon, stable vinylrhodium species were generated, which led to living polymerization. At least one substituent was necessary on the β‐carbon of the vinyllithium for the living polymerization. Tris(4‐substituted phenyl)phosphines worked well as third components among various phosphorus ligands. The polymerization was decelerated as the basicity of the phosphine ligand increased.

Thiolato complexes of Rh(III) bearing a hydrotris(3,5-dimethylpyrazolyl)borato ligand (Tp(Me2)) have been prepared, and their reactivity toward H(2) has been investigated. The bis(thiolato) complex [Tp(Me2)Rh(SPh)(2)(MeCN)] (1) reacted with 1 atm H(2) at 20 degrees C to produce the hydrido-thiolato complex [Tp(Me2)RhH(SPh)(MeCN)] (2) and PhSH via heterolytic cleavage of H(2). This process is reversible and in equilibrium in THF and benzene. The bis(selenolato) complex [Tp(Me2)Rh(SePh)(2)(MeCN)] (4) was also converted to [Tp(Me2)RhH(SePh)(MeCN)] and PhSeH under 1 atm H(2), but the equilibrium largely shifted to 4. Reaction of the dithiolato complex [Tp(Me2)Rh(bdt)(MeCN)] (3; bdt = 1,2-C(6)H(4)S(2)) with H(2) occurred in the presence of amine, giving the anionic hydrido complex [Tp(Me2)RhH(bdt)](-) and an equimolar amount of ammonium cations. Catalytic activity for hydrogenation has been examined under 1 atm H(2) at 20-50 degrees C. While 1, 2, and 4 slowly hydrogenated styrene at similar rates at 50 degrees C, activities for the hydrogenation of N-benzylideneaniline increased in the order, 2 < 1 < 4. Complex 3 was found to be the most active and selective catalyst for hydrogenation of imines, and thus a variety of imines were reduced at 20 degrees C under 1 atm H(2), with the C=C and C=O bonds in the substrate molecules completely preserved. An ionic mechanism was involved to explain such high chemoselectivity.

Phenylacetylenes (PAs) with bulky substituents (adamantyl, tert‐butyl, and n‐butyl groups) at the para‐position polymerized in good yields with Fe, Rh, Mo, and W catalysts. The formed polymers were soluble, and their number‐average molecular weights were in the range of thousands to hundred thousands. Whereas it is known that the poly(PA) obtained with the Fe catalyst is an insoluble cis‐cisoidal polymer, the present polymers formed with the same catalyst were totally soluble in many solvents such as benzene and CHCl3. The 1H‐ and 13C‐NMR and DSC data revealed that both of the polymers formed with the Fe and Rh catalysts had virtually all‐cis structures, while those with the Mo and W catalysts had cis‐rich and trans‐rich structures, respectively. Cis‐cisoidal and cis‐transoidal structures of para‐substituted poly(PAs) could not be distinguished because of their good solubility. The bulky substituents raised the temperature of cis–trans isomerization and improved the thermal stability of the polymers. Poly(p‐t‐BuPA) showed gas permeability higher than that of poly(PA). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3157–3163, 1998

The bis(thiolate)Rh(III) complex having a tris(3,5-dimethylpyrazolyl)borate (Tp(Me2)) coligand [Tp(Me2)Rh(SPh)(2)(MeCN)] reacts reversibly with H(2) to form the hydridothiolato complex [Tp(Me2)RhH(SPh)(MeCN)] and PhSH. The benzenedithiolate analogue [Tp(Me2)Rh(o-S(2)C(6)H(4))(MeCN)], which can also heterolytically activate H(2), catalyzes hydrogenation of imines under ambient temperature and pressure with high chemoselectivity.

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