Organogold(III) complexes derived from auration reactions of thienyl-substituted pyridine derivatives

2-(3-Thienyl)pyridine (3-Hthpy) and 2-(2-thienyl)pyridine (2-Hthpy) reacted with Na[AuCl4]. 2H(2)O to afford the adducts [AuCl3(3-Hthpy)] 1a and [AuCl 3(2-Hthpy)] 1b, respectively. The cycloaurated complex [AuCl2(3-thpy-C-2,N) ] [3-thpy=3-(2-pyridyl)thiophen-2-yl] 2a was obtained by warming 1a at 80 d egrees C in an acetonitrile-water (1:5) mixed solvent, whereas the cycloaur ated complex [AuCl2(2-thpy-C-3,N)] [2-thpy= 2-(2-pyridyl)thiophen-3-yl] 2b was produced by the reaction of 1b with silver(I) tetrafluoroborate in refl uxing dichloromethane. Moreover, when 1b was heated at reflux in dichlorome thane in the absence of silver(I) tetrafluoroborate, the thiophene-C(5) met allated species [{Au(mu-Cl)Cl[(2-thpy-C-5)H]}(2)]Cl-2 [2-thpy=2-(2-pyridyl) thiophen-5-yl] 3b was formed. Thermal degradation of 3b in aqueous acetonit rile yielded 2-(5-chloro-2-thienyl)pyridine and 5,5'-bis(2-pyridyl)-2,2'-bi thienyl. X-Ray structural analyses of [AuCl(3-thpy-C-1,N)(PPh3)]BF4 4a and [AuCl(3-thpy-C-1,N)(PPh3)]BF4 4b, which were obtained by the reactions of 2 a and 2b with triphenylphosphine, have been performed.