No abstract

A set of nickel­(II) Cp complexes with triazolylidenes containing various different wingtip groups (aryl, alkyl, pyridyl, CH2OH) have been synthesized by direct metalation of the corresponding triazolium salt with nickelocene. Distinct effects of the substituents on electronic and steric properties of the formed complexes are demonstrated by NMR spectroscopy and single-crystal structural analysis, as well as by the catalytic activity of the complexes in the hydrosilylation of aldehydes. While all complexes display appreciable catalytic performance, the cyclometalated pyridyl-functionalized triazolylidene nickel complex 2e is highly active and reaches turnover frequencies of >20 000 h–1 with good catalyst stability (full conversion at 0.05 mol % catalyst, maximum turnovers of ∼6000). A variety of functional groups on the benzaldehyde are tolerated. Ketones are not converted, which identifies complex 2e as a highly selective precatalyst for the hydrosilylation of aldehydes in the presence of ketones.

The efficient conversion of electron-poor aryl triflates to the corresponding aromatic amines was accomplished by using ZnCl 2 complexes of organic amines as nitrogen source with K 2 CO 3 as the base in DMSO. The coupling reaction was performed in air and ligand-free without the sealed vessel. A possible mechanism, which was different with aromatic nucleophilic substitution (S N Ar), was proposed. The amination products were confirmed by 1 H NMR, IR and MS techniques.