Chelate Bis(imino)pyridine Cobalt Complexes: Synthesis, Reduction, and Evidence for the Generation of Ethene Polymerization Catalysts by Li<sup>+</sup> Cation Activation
with Li[B(C6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (ligMe)CoCH3 (17) with Li[B(C6F5)4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33
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
Simple and Mild Method for Preparation of .ALPHA.-Pyridinecarboxylates and .ALPHA.-Pyridyl Ketones via Trimethylstannyl Derivatives.
作者:Yutaka YAMAMOTO、Hidekazu OUCHI、Takuo TANAKA
DOI:10.1248/cpb.43.1028
日期:——
Alkoxycarbonylation and acylation at the α-position of pyridine, quinoline, and isoquinoline via the respective trimethylstannyl derivatives were satisfactorily performed by employing ethyl chloroglyoxylate and acylformyl chloride under mild conditions.
Carbonylative cross-coupling of different pyridyl halides with various boronic acids was studied using catalytic systems constituted of N-heterocyclic carbene type ligands and palladium. These systems easily obtained in situ from the corresponding imidazolium salt and palladium acetate appear more efficient toward bromopyridines than catalysts based on hindered and basic alkylphosphines such as tricyclohexylphosphine
The use of N-heterocyclic carbene-type ligands with palladium catalysts allows the activation of chloropyridines and chloroquinoline towards carbonylative cross-coupling with phenylboronic acid for the synthesis of unsymmetrical biaryl ketones.