Preparation and NMR Spectra of the (Trifluoromethyl)argentates(III) [Ag(CF(3))(n)X(4-n)](-), with X = CN (n = 1-3), CH(3), C&tbd1;CC(6)H(11), Cl, Br (n = 2, 3), and I (n = 3), and of Related Silver(III) Compounds. Structures of [PPh(4)][trans-Ag(CF(3))(2)(CN)(2)] and [PPh(4)][Ag(CF(3))(3)(CH(3))].
Trifluoromethylation of [Ag(CN)(2)](-) with (CF(3))(2)Cd.diglyme yields [Ag(CF(3))(CN)](-). The anion is readily oxidized by bromine to the argentates(III), [Ag(CF(3))(n)(CN)(4-n)](-), n = 1-4. The stability of these species decreases with an increasing number of CN groups. Halogenation of these complexes with acetyl chloride or with bromine affords the moderately stable (n = 3) or unstable (n = 2) haloargentates of the type [Ag(CF(3))(n)X(4-n)](-), X = Cl or Br. Their dehalogenation with AgNO(3) in a donor solvent D gives the adducts [Ag(CF(3))(3)D] and [Ag(CF(3))(2)D(2)](+), respectively. Decomposition of most argentates(III) proceeds by reductive elimination of CF(3)X (X = Cl, Br, or CN), but ligand exchange with participation of the CF(3) groups is also observed. The latter is used to prepare Ag(CF(3))(3) derivatives from the readily accessible [trans-Ag(CF(3))(2)(CN)(2)](-) anion. The syntheses of methyl(trifluoromethyl)argentates(III) and of (cyclohexylethynyl)(trifluoromethyl)argentates(III) are accomplished by reaction of the cyanoargentates (n = 2, 3) with CH(3)MgCl or LiC&tbd1;CC(6)H(11), respectively. Often multinuclear ((109)Ag, (19)F, (13)C, (1)H) NMR data of transient and stable Ag(III) species establish unambiguously not only their constitution but also the square-planar coordination of the metal. Couplings to the spin-(1)/(2) silver nuclei are interpreted on the basis of 5s(Ag) orbital participation in competition with 4d orbital contributions to Ag-CF(3) bonding. Crystals of [PPh(4)][Ag(CF(3))(2)(CN)(2)] belong to the monoclinic space group C2/c, with a = 18.174(2) Å, b = 7.8881(8) Å, c = 18.881(2) Å, beta = 93.036(8) degrees, and Z = 4, whereas [PPh(4)][Ag(CF(3))(3)(CH(3))] crystallizes in the orthorhombic space group Pca2(1), with a = 24.941(3) Å, b = 7.2629(6) Å, c = 14.9985(14) Å, and Z = 4. The coordination environments of these two argentates are approximately square planar. The Ag-CF(3) bonds in the dicyano complex (2.105(4) Å) are distinctly longer than the Ag-CN linkages (2.013(3) Å). In the [Ag(CF(3))(3)(CH(3))](-) anion, the Ag-CH(3) distance (2.097(5) Å) is slightly shorter than the average Ag-CF(3) bond lengths (2.119(10) Å).
Eujen
Reint
R
Anorganische Chemie, Fachbereich 9, Universität-GH, 42097 Wuppertal, Germany.
Hoge
Berthold
B
Brauer
David J.
DJ