SYNTHESIS AND CHARACTERIZATION OF GOLD(III) ADDUCTS AND CYCLOMETALATED DERIVATIVES WITH 2-SUBSTITUTED PYRIDINES - CRYSTAL-STRUCTURE OF [AU(NC5H4(CME(2)C(6)H(4))-2)CL-2]

The 2-benzylpyridines HL [NC5H4-(CH(2)Ph)-2, -(CHMePh)-2 and (CMe(2)Ph)-2] reacted with AuCl3 . 2H(2)O or Na[AuCl4] to give adducts [Au(HL)Cl-3] or cyclometallated derivatives [AULCl(2)]. The metallation reaction involves direct activation of a C-H bond of the phenyl substituent. With the 2-alkylpyridines NC5H4(CMe(3))-2 and NC5H4(CH(2)CMe(3))-2 (HL) on ly the tetrachloroaurate (III) salts [H(2)L][AuCl4] were isolated. The structure of [Au{NC5H4(CMe(2)C(6)H(4))-2}Cl-2] has been determined by X-ray diffraction. It reveals a six-membered ring having a boat-like conformation: there is a rather short interaction between one hydrogen of the Me group in axial position and the gold atom. AU ... H 2.56(5) Angstrom. The cyclometallated species react with PPh(3) to give cationic complexes [AUL(PPh(3))Cl](+) and with 1,2-bis(diphenylphosphino)ethane (dppe) to yield [AuL(dppe)Cl](+). Under pressure (50 atm, 60 degrees C) of CO extrusion of the metal occurs. The organic products formed likely arise from insertion of CO into the Au-C bond. The reactivity of the cycloaurated species, is compared with that of analogous palladium(II) derivatives described previously.