Polymerization of Phenylacetylenes
Using Rhodium Catalysts
Coordinated by Norbornadiene Linked to a Phosphino or Amino Group
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Abstract
The novel rhodium (Rh) catalysts [{nbd-(CH<sub>2</sub>)<sub>4</sub>-X}RhR] (<b>1</b>, X = PPh<sub>2</sub>, R = Cl; <b>2</b>, X = NPh<sub>2</sub>, R = Cl; <b>3</b>, X = PPh<sub>2</sub>, 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 (Et<sub>3</sub>N). Addition of Et<sub>3</sub>N 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 Et<sub>3</sub>N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA
