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] (1, X = PPh2, R = Cl; 2, X = NPh2, R = Cl; 3, 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 1 exists in a mononuclear 16-electron state, while 2 exists in dinuclear states. Catalyst 1 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 2 and 3 quantitatively converted PA in the absence of Et3N to afford the polymer in good yields. Catalyst 3 achieved two-stage polymerization of PA.本研究合成了新型铑（Rh）基配合物催化剂[{nbd-(CH2)4-X}­RhR]（其中催化剂1：X=二苯基膦基（PPh2），R=氯原子；催化剂2：X=二苯基氨基（NPh2），R=氯原子；催化剂3：X=二苯基膦基（PPh2），R=三苯基乙烯基；nbd为2,5-降冰片二烯（2,5-norbornadiene）），并考察了其在苯乙炔（PA）及其衍生物聚合反应中的催化活性。通过103铑核磁共振（NMR）光谱结合密度泛函理论（DFT）计算（B3LYP/6-31G*-LANL2DZ）分析可知，催化剂1以单核16电子构型存在，而催化剂2则以双核构型存在。在无三乙胺（Et3N）的条件下，催化剂1对苯乙炔的单体转化率不足1%；加入三乙胺并延长聚合时间可提升单体转化率。与之相对，催化剂2和3在无三乙胺的条件下可定量转化苯乙炔，以较高收率得到聚合物；其中催化剂3可实现苯乙炔的两段式聚合。