Rh(I)(2,5-norbornadiene)(biphenyl)(tris(4-fluorophenyl)phosphine): Synthesis, Characterization, and Application as an Initiator in the Stereoregular (Co)Polymerization of Phenylacetylenes

Well-Controlled Living Polymerization of N-Propargylamides and Their Derivatives by Rhodium Catalysis

A substantially improved method for living polymerization of N-propargylamides and their derivatives has been developed. Rhodium(I) complexes bearing an aryl-substituted 1,3,5-hexatriene chain can work as excellent initiators of the polymerization of such non-conjugated terminal alkynes to give the corresponding cis-stereoregular polymers having a narrow molecular weight distribution. The typical living nature has been confirmed by investigating the effects of initial feed ratios of the monomer to the initiator on the molecular weight of the resulting polymers as well as multistage polymerization. Moreover, we demonstrated that the present method enables functionalization of both polymer chain ends and synthesis of novel block copolymers consisting of poly(N-propargylamide) and poly(phenylacetylene) blocks with a narrow molecular weight distribution.

Rhodium(I) Complexes Bearing an Aryl-Substituted 1,3,5-Hexatriene Chain: Catalysts for Living Polymerization of Phenylacetylene and Potential Helical Chirality of 1,3,5-Hexatrienes

Unique and bench-stable rhodium(I) complexes bearing an aryl-substituted 1,3,5-hexatriene chain have been synthesized by the reactions of bicyclo[2.2.1]hepta-2,5-diene-rhodium(I) chloride dimer ([Rh(nbd)Cl]2) with aryl boronic acids and diphenylacetylenes in the presence of a 50% aqueous solution of KOH. X-ray crystallographic analysis of the isolated complexes indicated a square-planar structure stabilized by a strong interaction with one of the aryl groups on the 1,3,5-hexatriene chain, which has a helical structure. The helical chirality of the isolated rhodium complexes was confirmed to be sufficiently stable to be resolved by chiral HPLC at room temperature into enantiomers, which showed mirror-imaged CD spectra. It was confirmed that the isolated rhodium complex worked as an initiator for living polymerization of phenylacetylene to give cis-stereoregular poly(phenylacetylene) with a well-controlled molecular weight.

Synthesis of Stereoregular Telechelic Poly(phenylacetylene)s: Facile Terminal Chain-End Functionalization of Poly(phenylacetylene)s by Terminative Coupling with Acrylates and Acrylamides in Rhodium-Catalyzed Living Polymerization of Phenylacetylenes

Various α,β-unsaturated carbonyl compounds, such as acrylates and acrylamides, were quantitatively introduced to the terminal chain end of poly(phenylacetylene)s by C-C bond formation with terminal organorhodium(I) species formed in the living polymerization of phenylacetylenes with a rhodium-based multicomponent catalytic system that we have recently developed, when these carbonyl compounds were used as terminating reagents. This enables the facile and versatile synthesis of stereoregular telechelic poly(phenylacetylene)s with various functional groups at both the initial and terminal chain ends because the components of aryl boronic acid derivatives used as initiators in our multicomponent catalytic system are quantitatively introduced to the initiating end of the resulting polymer.

Facile and Versatile Synthesis of End-Functionalized Poly(phenylacetylene)s: A Multicomponent Catalytic System for Well-Controlled Living Polymerization of Phenylacetylenes

A rhodium-based multicomponent catalytic system for well-controlled living polymerization of phenylacetylenes has been developed. The catalytic system is composed of readily available and bench-stable [Rh(nbd)Cl]₂ , aryl boronic acid derivatives, diphenylacetylene, 50 % aqueous KOH, and PPh₃ . This system offers a method for the facile and versatile synthesis of various end-functionalized cis-stereoregular poly(phenylacetylene)s because components from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the polymers. The polymerization reaction shows a typical living nature with a high initiation efficiency, and the molecular weight of the resulting poly(phenylacetylene)s can be readily controlled with very narrow molecular-weight distributions (M_w /M_n =1.02-1.09). The experimental results suggest that the present catalytic system has a higher polymerization activity than the polymerization activities of other rhodium-based catalytic systems previously reported.