title: Synthesis, characterization and catalytic activity of saturated and unsaturated N-heterocyclic carbene iridium(i) complexes.
abstract: Both saturated and unsaturated N-benzyl substituted heterocyclic carbene (NHC) iridum(i) complexes were synthesized. The unsaturated carbene complex [(un-NHC-Bn)Ir(CO)(2)Cl] in the cis form was prepared via the carbene transfer from the corresponding silver complex to [Ir(COD)(2)Cl](2) followed by ligand substitution with CO, whereas the saturated complex was obtained via the transfer from (sat-NHC-Bn)W(CO)(5). The treatment of phosphines with (NHC)Ir(CO)(2)Cl complexes yielded the products with the phosphine ligand trans to the carbene moiety via substitution. X-Ray structural determination shows that distances of Ir-C((carbene)) in both (un-NHC-Bn)Ir(CO)(PR(3))Cl and (un-NHC-Bn)Ir(CO)(PR(3))Cl are essentially the same. Analyses of spectroscopic and crystal structural data of iridium complexes [(NHC)Ir(CO)(PR(3))Cl] and Vaska's complex show similar corresponding data in both types of complexes, suggesting that the studied NHC ligands and phosphines have similar bonding with Ir(i) metal center. All iridium complexes studied in this work illustrated their catalytically activity on N-alkylation of amine with alcohol via hydrogen transfer reduction. It appears no dramatic difference on the catalytic activity among these iridium carbene complexes; but the saturated carbene complex (sat-NHC-Bn)Ir(CO)(PR(3))Cl appears to be slightly more active. For example, the reaction of benzyl alcohol with aniline in the presence of catalyst (1 mol%) under basic conditions at 100 degrees C provided the secondary amine (N-benzylaniline) in 96% yield.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Yung-Hung
authors.initials: YH
authors.lastname: Chang
authors.forename: Ching-Feng
authors.initials: CF
authors.lastname: Fu
authors.forename: Yi-Hong
authors.initials: YH
authors.lastname: Liu
authors.forename: Shei-Ming
authors.initials: SM
authors.lastname: Peng
authors.forename: Jwu-Ting
authors.initials: JT
authors.lastname: Chen
authors.forename: Shiuh-Tzung
authors.initials: ST
authors.lastname: Liu
mesh_terms: D000814:Aniline Compounds / Q000138:chemical synthesis / Q000737:chemistry; D019905:Benzyl Alcohol / Q000737:chemistry; D002384:Catalysis; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000814:Aniline Compounds; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C030011:carbene; D007495:Iridium; D019905:Benzyl Alcohol; D008697:Methane; C028443:benzylaniline; C023650:aniline