Investigations into the Mechanism of Activation and Initiation of Ethylene Polymerization by Bis(imino)pyridine Cobalt Catalysts: Synthesis, Structures, and Deuterium Labeling Studies
摘要:
The activation of bis(imino)pyridine cobalt(II) precatalysts by MAO leads initially to a bis(imino)pyridine cobalt(I) cationic species with no cobalt-C(alkyl) bond into which insertion can occur. Mechanistic studies have shown that the initiation of polymerization from this species involves incorporation of alkyl groups from the cocatalyst, most likely involving attack of methide anion (from the counteranion) on a cobalt-ethylene species.
The Electronic Structure of (Diiminopyridine)cobalt(
<scp>I</scp>
) Complexes
作者:Quinten Knijnenburg、Dennis Hetterscheid、T. Martijn Kooistra、Peter H. M. Budzelaar
DOI:10.1002/ejic.200300569
日期:2004.3
square-planar (LCoR)-R-I complexes of a diiminopyridine ligand are best regarded as containing low-spin Co-II antiferromagnetically coupled to a ligand radical anion. The lowest triplet state, corresponding to a 3d(z)(2)-->pi* excitation, is calculated to be only a few kcal/mol above the ground state, and is thermally accessible. The anomalous H-1 NMR chemical shifts of the LCoR complexes are suggested to