Crystal structure of [CF 3CFC(CF 3)Ag] 4 and its use as a chemical vapor deposition precursor for silver films

Abstract

Silver films have been prepared by the metal-organic chemical vapor deposition of perfluoro-1-methyl-1-propenylsilver tetramer, [CF 3CFC(CF 3)Ag] 4, at 275°C and 10 −4 Torr; the silver films contain only traces (< 1%) of fluorine and oxygen and no carbon. The principal organic byproducts formed during deposition are trans-CF 3CFCH(CF 3) (50%) and CF 3CCCF 3 (40%). It is argued that silver metal is produced by elimination of CF 3CCCF 3 from trans-[CF 3CFC(CF 3)Ag] 4 to form silver(I) fluoride, which defluorinates to form silver metal. The crystal structure of trans-[CF 3CFC(CF 3)Ag] 4 was determined and reveals that this compound is a tetramer that consists of a square plane of silver atoms in which each edge is bridged by a trans-perfluoro-1-methyl-1-propenyl ligand. The average distances and angles are: AgAg = 2.761 Å, AgC = 2.19 Å, AgCAg = 78.3° and CAgC = 166.7°. Crystal data: monoclinic, space group P2 1/ c, a = 9.480(5) Å, b = 15.589(6) Å, c = 18.919(4) Å, β = 90.27(3)°, V = 2796(4) Å 3, Z = 4, R f = 0.070, and R wF = 0.089 on 433 variables and 3617 data with I > 2.58 σ( I).