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 1H, 13C, and 31P 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 1H and 1H–13C HSQC NMR spectroscopy. The polymerization degree was calculated to be 11 by 1H NMR spectroscopy, which agreed well with the theoretical value.