Halide Effects on the Sublimation Temperature of X-Au-L Complexes: Implications for Their Use as Precursors in Vapor Phase Deposition Methods.

Trends in volatility with changes in the halide ligand were established for gold(I) complexes of the type X-Au-L [X = Cl, Br, I; L = CNtBu, CNMe, PMe3, P(NMe2)3, P(OCH2CF3)3] by determining the temperatures for the onset of sublimation (Tsub) at a fixed pressure. Within each series of isocyanide complexes, Tsub decreases with increasing atomic radius of the halide, making the iodide complex the most volatile. For the phosphine and phosphoramidate complexes, the chloride and bromide have similar Tsub values with the bromide slightly higher, but the iodide complex is again the most volatile of the three. The trends in volatility can be correlated to variation in Au-Au bond distances and aggregation patterns in the solid state structures. For the P(OCH2CF3)3 complexes, melting occurred before sublimation, but the iodide complex was still more volatile than the bromide. These trends have implications for the use of these complexes in electron beam induced deposition and chemical vapor deposition, for which precursor volatility is important.