Yongbao Zhu, B. Cameron, R. Skerlj
Jul 1, 2003
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0
Influential Citations
11
Citations
Journal
Journal of Organometallic Chemistry
Abstract
Direct cycloauration of 2-phenoxypyridines with different substituents at the 5-position of the pyridine ring was carried out in an CH 3 CN/H 2 O medium, leading to isolation of cycloaurated compounds AuCl 2 ( L ) ( HL =substituted 2-phenoxypyridine ligand) with alkyl, substituted alkyl, phenyl, halo, ester and amido groups. The preparation of cycloaurated compounds involves the formation of an intermediate AuCl 3 ( HL ) via coordination reaction between the pyridine ligand and NaAuCl 4 at room temperature and subsequent formation of the Au−C bond at elevated temperature in an CH 3 CN/H 2 O medium. The presence of a bulky lipophilic group decreases the yield of cycloaurated compounds and favors the decomposition of the reaction species to Au(0). No coordination reaction was observed for ligands with a strong electron-withdrawing substituent (nitro or nitrile) in the pyridine ring. The ligand having the electron-donating dimethylamino group is oxidized by NaAuCl 4 at room temperature. The presence of a thienyl or an acetyl group allowed the isolation of the intermediate AuCl 3 ( HL ), but has an adverse effect on the subsequent cycloauration. The result of direct cycloauration of methyl-substituted 2-phenoxypyridine ligands indicated that the presence of a methyl group at the 6-position in the pyridine ring closest to the Au−N(py) bond resulted in poor cycloauration and a decrease in compound stability. The X-ray crystal structure of the cycloaurated compound 25 was determined, depicting a four-coordinate Au atom located in the center of a slightly distorted square.