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

The following Ag-I bis(pyrazolyl)methane complexes with BF4-/NO3- as counteranions were synthesized and characterized: [Ag(L-pzH)](2)(NO3)(2) (1), [Ag(L-pzMe)](2)(NO3)(2) (2), [Ag(L-pzH)](n)(BF4)(n) (3), and [Ag(L-pzMe)](n)(BF4)(n) (4) [L-pzH = bis(pyrazolyl)methane; L-pzMe = 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(L-pzH)(H2O)(2)](2)(BF4)(2) (3a) and [Ag(L-pzMe)(H2O)(2)](2)(BF4)(2) (4a). All of the dinuclear species 1, 2, 3a and 4a exhibit an argentophilic interaction with AgAg distances in the range 3.18-2.99 angstrom. Thermogravimetric analysis (TGA) shows that 1 and 2 have lower decomposition temperatures (231 and 255 degrees C, respectively) than 3 and 4 (298 and 331 degrees C, respectively). 2 was further investigated as a precursor for metallic silver deposition by spin-coating solutions (10(-3) m, THF/DMSO, 4:1), followed by annealing at 310 degrees 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.