CRYSTAL-STRUCTURE OF [CF3CF=C(CF3)AG]4 AND ITS USE AS A CHEMICAL-VAPOR DEPOSITION PRECURSOR FOR SILVER FILMS

Silver films have been prepared by the metal-organic chemical vapor deposition of perfluoro-1-methyl-1-propenylsilver tetramer, [CF3CF=C(CF3)Ag]4, at 275-degrees-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-CF3CF=CH(CF3) (50%) and CF3C=CCF3 (40%). It is argued that silver metal is produced by elimination of CF3C=CCF3 from trans-[CF3CF=C(CF3)Ag]4 to form silver(I) fluoride, which defluorinates to form silver metal. The crystal structure of trans-[CF3CF=C(CF3)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 angstrom, Ag-C = 2.19 angstrom, Ag-C-Ag = 78.3-degrees and C-Ag-C = 166.7-degrees. Crystal data: monoclinic, space group P2(1)/c, a = 9.480(5) angstrom, b = 15.589(6) angstrom, c = 18.919(4) angstrom, beta = 90.27(3)-degrees, V = 2706(4) angstrom3, Z = 4, R, = 0.070, and R(wF) = 0.089 on 433 variables and 3617 data with I > 2.58 sigma(I).