Metal Complexes with a Naphthyridine-Based N-Heterocyclic Carbene (NHC) Lignad: Synthesis and Catalytic Activities
Date Issued
2014
Date
2014
Author(s)
Huang, Hsiao-Ching
Abstract
In this work, we explored the syntheses, characterization and catalytic activity of metal complexes containing a naphthyridine-based N-heterocyclic carbene ligand. The desired rhodium(I), iridium(I) and palladium(II) complexes were obtained via a known carbene transfer method. The reaction of naphthyridine-based NHC ligand 6, silver nitrate and potassium carbonate afforded the silver bis-carbene complex 7. Upon the reaction between the silver NHC complex with [Rh(COD)Cl]2 or [Ir(COD)Cl]2, the carbene fragment readily transferred from silver to rhodium and iridium center, providing the Rh(I) and Ir(I) carbene complex. As revealed in X-ray crystallography, Rh(I) carbene complex 8 adopted a square-planar geometry with the coordination of cyclooctadiene moiety. The rhodium and iridium carbene complex 8 and 9 can be converted to the corresponding ionic ones 10 and 11 by using silver tetrafluoroborate to remove chloride. The palladium(II) complexes 12 was prepared through the reaction of silver complex 7, [Pd(C3H5)Cl]2 and silver tetrafluoroborate. Its structure was confirmed by X-ray crystal structural analysis to illustrate the coordination of a η3-allyl fragment and the square planar geometry around the metal center. The palladium(II) complex 12 acted as an effective catalyst toward hydrogen transfer reaction. The C=C of α, β-unsaturated carbonyl substrates can be selectively reduced to yield saturated carbonyl compounds with formic acid as the proton source. Compared to the Rh(I) and Ir(I) complexes as well as other palladium complexes, it exhibited better catalytic activity and selectivity. With this method, α, β-unsaturated ketones, esters, amides and acids can be selectively hydrogenated to the corresponding saturated compound.
Subjects
萘啶
含氮雜環碳烯
Type
thesis
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