Synthesis, Properties and Application of N-Heterocyclic Carbene Metal Complexes
Date Issued
2009
Date
2009
Author(s)
Chang, Yung-Hung
Abstract
In this thesis, we have synthesized both saturated and unsaturated N-heterocyclic carbene iridium complexes [(NHC)Ir(CO)2Cl] (where NHC = IBn, SIBn) and have studied the difference between these complexes on coordination behavior, stability and catalytic activity. The unsaturated carbene complex cis-[(IBn)Ir(CO)2Cl] was prepared via the carbene transfer from the corresponding silver carbene complex to [Ir(COD)2Cl]2 followed by the ligand substitution with CO, whereas the saturated one cis-[(SIBn)Ir(CO)2Cl] was obtained directly via the carbene transfer from (SIBn)W(CO)5. Treatment of phosphines with [(NHC)Ir(CO)2Cl] resulted the formation of the products with the phosphine ligand trans to the carbene moiety via substitution of CO. X-ray structural determinations show that the distances of Ir-C(carbene) in both [(IBn)Ir(CO)(PR3)Cl] and [(SIBn)Ir(CO)(PR3)Cl] are essentially the same. Analyses of spectroscopic and crystal structural data of iridium complexes (NHC)Ir(CO)(PR3)Cl and the Vaska’s complex reveal that NHC ligands and phosphines have a similar donating ability toward Ir(I) metal center. All iridium complexes studied in this work are good pre-catalysts on N-alkylation of amines with alcohols via hydrogen transfer reduction. It appears no dramatic difference on the catalytic activity among these iridium carbene complexes; but the saturated carbene complex SIBn-Ir(CO)(PR3)Cl appears to be slightly more active. On the second project, 2,7-bis(1-mesitylimidazolium-3-yl)naphthyridine salt was used as a carbene precursor, which reacted with Ag2O to yield the corresponding silver carbene complex. Treatment of this silver complex with Pd(PhCN)2Cl2 in CH3CN yielded the dimeric NHC-Pd(II) complex. Structural determination of the palladium complex was discussed.
Subjects
N-heterocyclic carbene
iridium
dinuclear palladium
Type
thesis
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