Silver(I) Bis(pyrazolyl)methane Complexes and Their Implementation as Precursors for Metallic Silver Deposition

The following AgIbis(pyrazolyl)methane complexes with BF4–/NO3–as counteranions were synthesized and characterized: [Ag(LpzH)]2(NO3)2(1), [Ag(LpzMe)]2(NO3)2(2), [Ag(LpzH)]n(BF4)n(3), and [Ag(LpzMe)]n(BF4)n(4) [LpzH= bis(pyrazolyl)methane; LpzMe= bis(3,5-dimethylpyrazolyl)methane]. These complexes were prepared to identify optimum precursors for the thermolytic deposition of metallic silver. The crystal structures of 1 and 2 show that the complexes are dinuclear and that the NO3–anions interact with the metals. In contrast, 3 is polymeric and the BF4–does not interact with the metal. When crystallizing 1–4 in non-anhydrous solvents, the presence of adventitious water further reacts with 3 and 4 (but not with 1 and 2) to yield dinuclear complexes [Ag(LpzH)(H2O)2]2(BF4)2(3a) and [Ag(LpzMe)(H2O)2]2(BF4)2(4a). All of the dinuclear species 1, 2, 3a and 4a exhibit an argentophilic interaction with Ag···Ag distances in the range 3.18–2.99 Å. Thermogravimetric analysis (TGA) shows that 1 and 2 have lower decomposition temperatures (231 and 255 °C, respectively) than 3 and 4 (298 and 331 °C, respectively). 2 was further investigated as a precursor for metallic silver deposition by spin-coating solutions (10–3m, THF/DMSO, 4:1), followed by annealing at 310 °C on 52100 steel substrates. According to energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) the metal deposition proceeds primarily via an island growth (Volmer–Weber) mechanism.