Characterization of the Polymerization Catalyst [(2,5-norbornadiene)Rh{C(Ph)=CPh2}(PPh3)] and Identification of the End Structures of Poly(phenylacetylenes) Obtained by Polymerization Using This Catalyst

The structures of [(2,5-norbornadiene)Rh{C-(Ph)=CPh2)(PPh3)] (1) and its reaction product with CH3CO2H were elucidated by H-1, C-13, and P-31 NMR spectroscopy, mass spectrometry, and single-crystal X-ray analysis. The presence of two conformational isomers of 1 was verified by NMR spectroscopy, which was well-supported by DFT calculations. Phenylacetylene was polymerized using 1 as a catalyst with [M](0)/[Rh] = 10 and quenched with CH3CO2H and CH3CO2D. The incorporation of H and D at the polymer ends was confirmed by MALDI-TOF mass spectrometry and H-1 and H-1-C-13 HSQC NMR spectroscopy. The polymerization degree was calculated to be 11 by H-1 NMR spectroscopy, which agreed well with the theoretical value.