1004983-23-6Relevant articles and documents
Mechanism of ethylene oligomerization by a cationic palladium(II) alkyl complex that contains a (3,5-Me2-pyrazolyl)2CHSi(p-tolyl) 3 ligand
Conley, Matthew P.,Burns, Christopher T.,Jordan, Richard F.
, p. 6750 - 6759 (2007)
The reactivity of the ethylene oligomerization catalyst (NN)Pd(Me)(ethylene)+ (5), which contains a silyl-capped bis-pyrazolyl methane ligand (NN = (3,5-Me2-pyrazolyl) 2CHSi(p-tolyl)3 (1)) was investigated. The reaction of (NN)PdMeCl (3) with Li[B(C6F5)4] and ethylene in CH2Cl2 generates 5. Complex 5 undergoes ethylene insertion at -10 °C with a rate constant of kinsert,Me = 3.3(3) × 10-3 s-1. Complex 5 catalytically oligomerizes ethylene to branched C6-C20 internal olefins (-10 to 20 °C; 2.7-30 atm ethylene). NMR studies show that an equilibrium mixture of base-free β-agostic secondary alkyl (NN)PdR+ species (8) and ethylene adducts (NN)Pd(R)(ethylene)+ (9) is present under oligomerization conditions. Complex 9 decomposes to Pd0 at 20 °C, resulting in catalyst decomposition. (NN)Pd(R)(L) + species containing R groups that can function as internal donors (either η2-acyl or agostic β-H) undergo a dynamic process that exchanges the two pz* rings and are thermally unstable. It is proposed that catalyst decomposition and pz* exchange both involve initial coordination of the internal donor to generate a configurationally labile five-coordinate intermediate, which isomerizes, resulting in pz* site exchange or displacement of one arm of the NN ligand.
