摘要:
The complexes (1-Me-Ind)(PR3)Ni-Cl (Ind = indenyl; R = Me (2), Cy (3), Bu (4), and (CH2)(2)(CF2)(5)CF3 (5)) have been prepared by the direct reaction of the corresponding (PR3)(2)NiCl2 with Li(1-Me-Ind) or via phosphine exchange reactions with (1-Me-Ind)(PR ' (3))Ni-CI (R ' = Ph (1) and Me). Solution NMR and single-crystal X-ray diffraction studies of the structures of 2 and 3 have allowed an analysis of the mode of coordination of the 1-Me-Ind ligand both in the solid state and in solution. Kinetic studies have shown that the substitution of PPh3 in (1-Me-Ind)(PPh3)Ni-Cl by PCy3 follows a second-order rate (associative mechanism) with the following kinetic parameters. K-2 (x 10(-2) M-1 s(-1)) = 1.1 +/- 0.1 at 233 K, 1.9 +/- 0.4 at 245 K, 15 +/- 2 at 284 EC, 21 +/- 2 at 293 K, and 34 +/- 7 at 303 K, DeltaH double dagger = 6.40 +/- 0.07 kcal/mol; DeltaS double dagger = -40 +/- 4 eu. The implications of these results for the mechanisms of the polymerization reactions catalyzed by these complexes have been discussed.