CYCLOMETALATION REACTIONS OF 6-(2-THIENYL)-2,2'-BIPYRIDINE WITH D(8) TRANSITION-METAL IONS

The potentially terdentate ligand 6-(2-thienyl)-2,2'-bipyridine (Hthbipy) reacts with [MCl4]2- (M = Pd or Pt) under mild conditions to give cyclometallated complexes in which the thienyl ring is metallated at the 3 position. The metallated complexes [M(thbipy)Cl] (M = Pd or Pt) react with trimethyl phosphite to give phosphonate complexes [M(thbipy){P(=O)(OMe)2)] and with Na[acac] (Hacac = acetylacetone) to give [M(thbipy)(acac)] with a C-bonded acac ligand. Under mild conditions, the non-metallated compound [Pd(Hthbipy)Cl2] can be isolated. In contrast, the reaction of Hthbipy with Na[AuCl4] at ambient temperature yields the non-metallated complex [Au(Hthbipy)Cl3], but upon heating this, or performing the reaction at higher temperatures, the metallated compound [Au(thbipy)Cl2] is obtained. X-Ray structural analysis of this complex reveals it to be dimeric where the ligand has metallated at the 5 position of the thienyl ring and adopts a bridging bidentate NC mode [triclinic, space group P1BAR, a = 9.271(5), b = 14.214(10), c = 16.194(lo) angstrom, alpha = 108.11(5), beta = 96.55(5), gamma = 111.46(5)-degrees, Z = 2, R = 0.075, R' = 0.094].