Difluorocarbene insertion into SiH bonds: the preparation and properties of difluoromethylsilanes

Preparation and NMR Spectra of Difluoromethylated Silver(I) and Silver(III) Compounds. Structure of [PNP][Ag(CF(2)H)(4)]

The thermally unstable [Ag(CF(2)H)(2)](-) moiety is obtained in solution by reaction of silver(I) salts with Cd(CF(2)H)(2) in DMF/diglyme at -80 degrees C. Oxidation with I(2) leads to the argentate(III) [Ag(CF(2)H)(4)](-), which has been isolated as its PNP salt. According to DSC/TG analysis, the exothermic decomposition of this air-stable salt proceeds in two steps at 121 and 150 degrees C with formal elimination of one and three CFH units, respectively. Difluoromethylation of [Ag(CN)(2)](-) in the presence of acetyl chloride leads to the argentate(I) [Ag(CF(2)H)(CN)](-), which is oxidized by bromine at low temperatures to the thermally labile [trans-Ag(CF(2)H)(2)(CN)(2)](-) anion. Stable argentates(III) containing both difluoromethyl and trifluoromethyl groups are obtained by reaction of [Ag(CF(3))(n)()(CN)(4)(-)(n)()](-) (n = 1, 2-cis, 2-trans, and 3) with Cd(CF(2)H)(2)-the cis and trans configurations of the reactants being retained in their products for n = 2. The compounds are identified and characterized by multinuclear NMR spectroscopy. Crystals of [PNP][Ag(CF(2)H)(4)] belong to the tetragonal space group P4(3) with a = 9.475(1) Å, c = 42.159(6) Å, and Z = 4. The coordination of the silver atom is approximately square-planar with an average Ag-C bond length of 2.083(14) Å. The ligands are so oriented that each C-H bond is geared between the C-F bonds of a neighboring CF(2)H group-the overall symmetry being approximately C(4)(h)().