The virtually quantitative, room temperature hydration of various terminal and internal alkynes in methanol/water requires between 0.01-0.05 mol% of [AuCl(NHC)] activated with 1.5 equiv. of silver triflate and 45 equiv. of triflic acid (both relative to gold complex) with ton of up to 300.000. Iptycenyl-substituted NHC ligands play the key role and the most efficient NHC ligand is characterized by a hemispherical shape formed by two N-pentiptycenyl substituents.
Based on 1-amino-4-hydroxy-triptycene, new saturated and unsaturated triptycene-NHC (N-heterocyclic carbene) ligands were synthesized from glyoxal-derived diimines. The respective carbenes were converted into metal complexes [(NHC)MX] (M=Cu, Ag, Au; X=Cl, Br) and [(NHC)MCl(cod)] (M=Rh, Ir; cod=1,5-cyclooctadiene) in good yields. The new azolium salts and metal complexes suffer from limited solubility in common organic solvents. Consequently, the introduction of solubilizing groups (such as 2-ethylhexyl or 1-hexyl by O-alkylation) is essential to render the complexes soluble. The triptycene unit infers special steric properties onto the metal complexes that enable the steric shielding of selected areas close to the metal center. Next, chiral and meso-triptycene based N-heterocyclic carbene ligands were prepared. The key step in the synthesis of the chiral ligand is the Buchwald-Hartwig amination of 1-bromo-4-butoxy-triptycene with (1S,2S)-1,2-diphenyl-1,2-diaminoethane, followed by cyclization to the azolinium salt with HC(OEt)3 . The analogous reaction with meso-1,2-diphenyl-1,2-diaminoethane provides the respective meso-azolinium salt. Both the chiral and meso-azolinium salts were converted into metal complexes including [(NHC)AuCl], [(NHC)RhCl(cod)], [(NHC)IrCl(cod)], and [(NHC)PdCl(allyl)]. An in situ prepared chiral copper complex was tested in the enantioselective borylation of α,β-unsaturated esters and found to give an excellent enantiomeric ratio (er close to 90:10).
A thin film of poly-([IrCl(cod)(NHC-onbe)] -(propyl-onbe) ) (onbe=oxanorbornene) coated on filter paper reacts quantitatively with CO to yield 1,5-cyclooctadiene, the unpleasant smell of which can be detected by the human olfactory system with very high sensitivity. Odorless, but toxic CO is thus "translated" into the distinct smell of 1,5-cyclooctadiene. Based on malodorogenic sensing it is possible to smell the presence of CO.
The indirect detection of CO by using impregnated paper strips is reported. The ligand-substitution reaction of cod by CO in an organometallic complex leads to the liberation of 1,5-cyclooctadiene (cod), which can be smelled by the human olfactory system with very high sensitivity. Azolium salts tagged with methoxy polyethylene glycols (MeOPEG; 136, 750, and 2000 g/mol) were converted to the respective [IrCl(cod)- [a]
A new N,N′-bis(triptycenyl)-NHC ligand with methyl groups in the ortho position has been synthesized starting from 2,3-dimethyltriptycene-1,4-quinone. The respective metal complexes [ML(NHC)] [ML = CuBr, AuCl, PdCl(allyl), RhCl(cod), IrCl(cod), RhCl(CO) 2 , IrCl(CO) 2 , and RuCl 2 (=CHC 6 H 4 OiPr)] were [a]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.