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Preparation and NMR Spectra of Difluoromethylated Silver(I) and Silver(III) Compounds. Structure of [PNP][Ag(CF2H)4]
Eujen, Reint,Hoge, Berthold,Brauer, David J.
, p. 3160 - 3166 (1997)
The thermally unstable [Ag(CF2H2] moiety is obtained in solution by reaction of silver(I) salts with Cd(CF2H)2 in DMF/diglyme at -80 °C. Oxidation with I2 leads to the argentate(III) [Ag(CF2H)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 °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(CF2H)(CN)]-, which is oxidized by bromine at low temperatures to the thermally labile [trans-Ag(CF2H)2(CN)2]- anion. Stable argentates(III) containing both difluoromethyl and trifluoromethyl groups are obtained by reaction of [Ag(CF3)n(CN)4-n]- (n = 1, 2-cis, 2-trans, and 3) with Cd(CF2H)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(CF2H)4] belong to the tetragonal space group P43 with a = 9.475(1) A, c = 42.159(6) A, and Z = 4. The coordination of the silver atom is approximately square-planar with an average Ag-C bond length of 2.083(14) A?. The ligands are so oriented that each C-H bond is geared between the C-F bonds of a neighboring CF2H group-the overall symmetry being approximately C4h.
