Palladium(II) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity
Resource
Journal of Organometallic Chemistry 692 (18): 3976-3983
Journal
Journal of Organometallic Chemistry
Journal Volume
692
Journal Issue
18
Pages
3976-3983
Date Issued
2007
Author(s)
Abstract
Coordination chemistry of a pyridine imidazole-2-ylidene ligand (pyN ̂C) with sterically hindered substituents toward palladium(II) metal ions has been investigated. The palladium carbene complex [(C-pyN ̂C)Pd(η3-allyl)Cl] (3) is prepared via the transmetallation from the corresponding silver carbene complexes with [ClPd(η3-allyl)]2. Upon the abstraction of chloride, coordination of pyridinyl-nitrogen becomes feasible to form [C,N-(pyN ̂C)Pd(η3-allyl)](BF4) (4). Ligand substitution reaction of 4 with triphenylphosphine results in the formation of [(C-pyN ̂C)Pd(PPh3)(η3-allyl)](BF4)], which the pyridinyl-nitrogen donor is substituted by the phosphine. This palladium complex appears to be base sensitive. Treatment of 4 with t-butoxide causes the decomposition to yield the metal nano-particles. Furthermore, de-complexation of 4 takes place under hydrogen atmosphere to generate the carbene precursor, 1-(6-mesityl-2-picolyl)-3-mesitylimidazolium salt. Nevertheless, the palladium complex 4 shows good catalytic activity on the Suzuki-Miyaura and Mizoroki-Heck reactions. © 2007 Elsevier B.V. All rights reserved.
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journal article
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