Hydrogenation of ring-opening metathesis polymer with ruthenium catalysts

A ring-opening metathesis polymer (ROMP) of 8-methyl-8-methoxycarbonyltetra cyclo[4.4.0.1(2,5).1(7,10)]dodec-3-ene (poly-1) was hydrogenated with homog eneous catalysts. Monohydrido or dihydrido ruthenium(II) complexes achieved high hydrogenation degree which gave thermally stable saturated ROMP of 1 (poly-l-H-2). The kinetics of hydrogenation reactions in the presence of ca rbonylchlorohydridotris(triphenylphosphine)ruthenium, RuHCl(CO)(Ph-3)(3), ( 2) were studied in detail and found to follow first-order kinetics to the c oncentration of double bonds. Apparent activation energy for the overall hy drogenation reaction determined in the temperature range of 155-180 degrees C was smaller than that observed for the hydrogenation of acrylonitrile-bu tadiene copolymer by rhodium catalyst. The stirring rate did not affect hyd rogenation reaction rate, although slower stirring lead to lower conversion at the very beginning of the reaction, indicating diffusion of hydrogen in to the reaction media can be neglected if stirring is efficient. The concen tration of 2 also affected the reaction rate. The reaction rate leveled off at around 3 x 10(-2) mM reaching more than 4300 of turnover number. Applyi ng 100 kg cm(-2) of hydrogen at 160 degrees C in,m-xylene, high hydrogenati on degrees were achieved at ruthenium concentration as low as 20 ppm to the polymer.