Gold(III) derivatives with C(4)-aurated 1-phenylpyrazole

The reaction of 1-phenylpyrazole (HL), with gold(III) chloride has been studied. Besides a 1:1 adduct [Au(HL)Cl 3 ] 1 , where the ligand is bonded through the nitrogen atom, several C(4) aurated species have been isolated. Thus treatment of [AuCl 3 ] 2 with HL in dichloromethane solution affords a complex, [Au(L)Cl 2 . HCl] n , 2 , where the gold atom is bonded to the 4-carbon atom of the pyrazole ligand. Deprotonation of complex 2 by means of the not coordinating base 1,8-bis(dimethylamino)naphthalene (proton sponge), B, affords the salt [BH][Au(L)Cl 3 ], 3 , whereas reaction of 2 with 3,5-Me 2 py and PPh 3 (molar ratio 1:2) gives the neutral species trans -[Au(L)(3,5-Me 2 py)Cl 2 ], 4 , and cis -[Au(L)(PPh 3 )Cl 2 ], 5 , respectively. The structure of compound 4 solved by X-ray diffraction, unambiguously shows the anionic ligand L bonded to the gold ion through the C4 atom. Alternatively, compounds 4 and 5 can be obtained in two steps, i.e. deprotonation of 2 with NaOH to give [Au(L)Cl 2 ] n , 6 , and reaction of 6 with 3,5-Me 2 py and PPh 3 , respectively. The new species were characterized by elemental analyses, conductivity measurements, IR, NMR and FAB-MS spectroscopy.