Synthesis, structure and properties of tetrameric gold(I) 3,5-di-tert-butyl–pyrazolate

The reaction of Au(tht)Cl and 3,5-tBu2–pzH (pzH=pyrazole) in the presence of a base gives a tetranuclear complex as its only crystalline product. The latter has been characterized in solution by 1H and 13C NMR, as well as in two crystalline forms—[Au(μ-3,5-tBu2–pz)]4 (1) and [Au(μ-3,5-tBu2–pz)]4·CH2Cl2, (1·CH2Cl2)—by single crystal X-ray diffraction. Under UV irradiation, both 1 and 1·CH2Cl2 solid samples, as well as a CH2Cl2 solution of 1 luminesce with λmax 541, 517 and 550–600 nm, respectively. Attempts to oxidize [Au(μ-3,5-tBu2–pz)]4 by I2 fail, while oxidation reactions by Br2 or aqua regia yield AuBr4 − and AuCl4 −, respectively.