Solid State Structures and Phosphine Exchange Reactions of (1-Me-Indenyl)(PR3)Ni−Cl
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.
Solid State Structures and Phosphine Exchange Reactions of (1-Me-Indenyl)(PR3)Ni−Cl
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.
Dehydrogenative Oligomerization of PhSiH<sub>3</sub> Catalyzed by (1-Me-Indenyl)Ni(PR<sub>3</sub>)(Me)
作者:Frédéric-Georges Fontaine、Davit Zargarian
DOI:10.1021/om010757e
日期:2002.1.1
The complexes (1-Me-Ind)Ni(PR3)Me (Ind = indenyl; R = Ph, 1; Cy, 2; Me, 3) can act as single-component precatalysts for the dehydrogenative oligomerization of PhSiH3 to (PhSiH)(n) with M-w up to 1.6 x 10(3) in the case of 3. The catalytic Si-Si bond formation is initiated by a second-order, concerted reaction between the Ni-Me precursor and PhSiH3 which releases CH4. Kinetic studies of this Si-H bond activation step gave the following activation parameters for the reaction of 3 with PhSiH3: DeltaH(double dagger) = 10.7 +/- 0.7 kcal-mol(-1); DeltaS(double dagger) = -42 +/- 2 eu;k(H)/k(D) (for reaction with PhSiD3 at 313 K) = 9.8 +/- 0.5. The Ni-SiPhH2 species presumed to form in this reaction was not detected directly, but the presence of 1-SiPhH2-3-Me-Ind in the reaction mixtures, coupled with the fact that Ni(PMe3)(4) is an active precatalyst for the oligomerization of PhSiH3, suggests that the silyl intermediate undergoes a reductive elimination to generate Ni(O) species which might be involved in the catalysis.