Structural and NMR spectroscopic studies of 2-phenylsulfanylpyridine and its analogues or derivatives, and their Au(III) chloride complexes

Abstract

2-Phenylsulfanylpyridine (1), its analogues 2-phenylsulfinylpyridine (2), 2-phenylselanylpyridine (3) and 2-phenylseleninylpyridine (4), as well as 4′-substituted derivatives (methyl-, tert-butyl-, bromo- and nitro-, i.e.5–8) were characterized by 1H, 13C, 15N and 77Se NMR, including full assignment of all signals. Au(III) chloride complexes with these heterocycles (except from 4; denoted generally as L2Ar(S/SO/Se)py) of the general formula [Au(L2Ar(S/SO/Se)py)Cl3] (1a-3a and 5a-8a) were also studied by the same NMR methods. During an attempt to prepare 3a in the standard reaction between NaAuCl4 and 3, the new selenoxide 4 was unexpectedly obtained. 1H, 13C, 15N and 77Se NMR chemical shifts of all heterocycles and the resulting coordination shifts of the corresponding Au(III) complexes were discussed in relation to the molecular structures. The catalytic properties of 1a-3a and 5a-8a complexes were exhibited in the three-component reaction between phenylacetylene, benzaldehyde and piperidine, yielding 1-(1,3-diphenylprop-2-yn-1-yl)piperidine. 1a and 7a were also studied by single crystal X-ray diffraction, revealing typical Au(III) square-planar coordination sphere with slight deviations towards tetrahedral geometry.