New Approach to the Polymerization of Disubstituted Acetylenes by Bulky Monophosphine-Ligated Palladium Catalysts

Bulky monophosphine-ligated Pd complexes served as unprecedented admirable catalysts for the polymerization of a disubstituted acetylene. The moderately high polymer yields and cis content of the formed polyacetylene contrasted with those observed for traditional Mo catalyst-based polymer. These Pd catalysts are strong tools to promote the understanding of the structure–property relationships of disubstituted acetylenes

New Approach to the Polymerization of Disubstituted Acetylenes by Bulky Monophosphine-Ligated Palladium Catalysts

Bulky monophosphine-ligated Pd complexes served as unprecedented admirable catalysts for the polymerization of a disubstituted acetylene. The moderately high polymer yields and cis content of the formed polyacetylene contrasted with those observed for traditional Mo catalyst-based polymer. These Pd catalysts are strong tools to promote the understanding of the structure–property relationships of disubstituted acetylenes

Polymerization of Phenylacetylenes Using Rhodium Catalysts Coordinated by Norbornadiene Linked to a Phosphino or Amino Group

The novel rhodium (Rh) catalysts [{nbd-(CH₂)₄-X}­RhR] (<b>1</b>, X = PPh₂, R = Cl; <b>2</b>, X = NPh₂, R = Cl; <b>3</b>, X = PPh₂, R = triphenylvinyl; nbd = 2,5-norbornadiene) were synthesized, and their catalytic activities were examined for the polymerization of phenylacetylene (PA) and its derivatives. Rh-103 NMR spectroscopy together with DFT calculations (B3LYP/6-31G*-LANL2DZ) indicated that catalyst <b>1</b> exists in a mononuclear 16-electron state, while <b>2</b> exists in dinuclear states. Catalyst <b>1</b> converted PA less than 1% in the absence of triethylamine (Et₃N). Addition of Et₃N and extension of the polymerization time enhanced the monomer conversion. On the other hand, catalysts <b>2</b> and <b>3</b> quantitatively converted PA in the absence of Et₃N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA

Polymerization of Phenylacetylenes Using Rhodium Catalysts Coordinated by Norbornadiene Linked to a Phosphino or Amino Group

The novel rhodium (Rh) catalysts [{nbd-(CH₂)₄-X}­RhR] (<b>1</b>, X = PPh₂, R = Cl; <b>2</b>, X = NPh₂, R = Cl; <b>3</b>, X = PPh₂, R = triphenylvinyl; nbd = 2,5-norbornadiene) were synthesized, and their catalytic activities were examined for the polymerization of phenylacetylene (PA) and its derivatives. Rh-103 NMR spectroscopy together with DFT calculations (B3LYP/6-31G*-LANL2DZ) indicated that catalyst <b>1</b> exists in a mononuclear 16-electron state, while <b>2</b> exists in dinuclear states. Catalyst <b>1</b> converted PA less than 1% in the absence of triethylamine (Et₃N). Addition of Et₃N and extension of the polymerization time enhanced the monomer conversion. On the other hand, catalysts <b>2</b> and <b>3</b> quantitatively converted PA in the absence of Et₃N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA

Ligand Exchange Reaction for Controlling the Conformation of Platinum-Containing Polymers

Control of the conformation of polymers can be achieved by the <i>ligand exchange reaction</i> of optically active poly­(phenylene­ethynylene) <b>1′</b> containing −Pt­(PPh₃)₂– moieties in the main chain. Polymer <b>1′</b> was reacted with 1,2-bis­(diphenyl­phosphino)­ethane (dppe), 1,3-bis­(diphenyl­phosphino)­propane (dppp), and 1,4-bis­(diphenyl­phosphino)­butane (dppb) to give the corresponding polymers <b>2′</b>, <b>3′</b>, and <b>4′</b> containing −Pt­(dppe)–, −Pt­(dppp)– , and −Pt­(dppb)– moieties in the main chain, respectively. Polymers <b>1′</b> and <b>2′</b> exhibited negligibly small circular dichroism (CD) signals in THF, indicating the absence of regulated chiral structures, while polymers <b>3′</b> and <b>4′</b> exhibited strong CD signals in THF. The dynamic light scattering (DLS) analysis of the polymer solutions indicated that polymer <b>3′</b> formed a chirally regulated one-handed helix intramolecularly bridged with dppp, and polymer <b>4′</b> formed aggregates intramolecularly and/or intermolecularly bridged with dppb