Coordination Behaviour of Gold and Silver Towards Pyrazole Ligands

Treatment of pyrazole ligands HL (HL = pyrazole or 3,5‐dimethylpyrazole) with the gold(I) compound [Au(C 6 F 5 )(tht)] (tht = tetrahydrothiophene) gives either the complexes [Au(C 6 F 5 )(HL)] or, if the reaction is carried out in a molar ratio of 1:2 and in the presence of a base, the pyrazolate compound [NBu 4 ][{Au(C 6 F 5 )} 2 (μ‐L)]. Binuclear derivatives with bridging pyrazolate ligands have been obtained by treatment of the ligands with [O(AuPPh 3 ) 3 ][ClO 4 ] or [Au 2 Cl 2 (μ‐dppf)] (dppf = 1,1′‐bis(diphenylphosphanyl)ferrocene) and Na 2 CO 3 , to give [(AuPPh 3 ) 2 (μ‐L)][ClO 4 ] or [Au 2 (μ‐L)(μ‐dppf)]Cl. Treatment of [Ag(OTf)(PPh 3 )] with the pyrazole ligands affords the dimeric species [Ag 2 (μ‐OTf) 2 (HL) 2 (PPh 3 ) 2 ]. Gold(III) derivatives have been accessed by treatment of the pyrazole ligands with [Au(C 6 F 5 ) 3 (OEt 2 )] or [Au(C 6 F 5 ) 2 (OEt 2 ) 2 ][ClO 4 ], affording the species [Au(C 6 F 5 ) 3 (HL)] or [Au(C 6 F 5 ) 2 (HL) 2 ][ClO 4 ]. Gold(III) pyrazolate derivatives of the form trans ‐[NBu 4 ][Au(C 6 F 5 ) 2 Cl(L)] or [{Au(C 6 F 5 ) 2 } 2 (μ‐L) 2 ] have been prepared from [NBu 4 ][Au(C 6 F 5 ) 2 Cl 2 ] or [Au(acac)(C 6 F 5 ) 2 ]. X‐ray structural characterization has been carried out for eight compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)