Article ID Journal Published Year Pages File Type
1307815 Inorganica Chimica Acta 2006 10 Pages PDF
Abstract

The palladation of potentially chelating bisimidazolium ligand precursors with palladium acetate gives bridging bimetallic, chelating monometallic, and homoleptic tetracarbene complexes. The coordination mode of the biscarbene ligand has been identified by spectroscopic analysis and crystallographic characterization of representative complexes, including the first example of a biscarbene A-frame structure. Substantial concentrations of free acetate favor the formation of tetracarbene over biscarbene palladium complexes, while in the absence of a base, the concentration of reactants influences the selectivity for bridging bimetallic versus chelating monometallic species. Preliminary kinetic and mechanistic studies indicate that chelating biscarbene palladium acetate complexes are intermediates in the formation of the homoleptic tetracarbene complexes. Probably due to the high trans effect of the biscarbene ligand, such complexes are more efficient palladating agents for bisimidazolium salts than palladium acetate.

Graphical abstractThe reactivity of bisimidazolium salts similar to those used as ionic liquid solvents towards [Pd(OAc)2Pd(OAc)2] under different reaction conditions is reported to provide N-heterocyclic carbene complexes containing different ligand arrangements such as A-frame structures (see figure) and tetracarbene bonding. Mechanistic studies provide further details of the metallation of imidazolium salts.Figure optionsDownload full-size imageDownload as PowerPoint slide

Related Topics
Physical Sciences and Engineering Chemistry Inorganic Chemistry
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