Polyfluorinated Tris(pyrazolyl)borates. Syntheses and Spectroscopic and Structural Characterization of Group 1 and Group 11 Metal Complexes of [HB(3,5-(CF3)2Pz)3]-and [HB(3-(CF3)Pz)3]-

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Abstract
The fluorinated tris(pyrazolyl)borate ligands [HB(3,5-(CF3)2Pz)3]- and [HB(3-(CF3)Pz)3]- (where Pz = pyrazolyl) have been synthesized as their sodium salts from the corresponding pyrazoles and NaBH4 in high yield. These sodium complexes and the related [HB(3,5-(CF3)2Pz)3]K(DMAC) were used as ligand transfer agents in the preparation of the copper and silver complexes [HB(3,5-(CF3)2Pz)3]Cu(DMAC), [HB(3,5-(CF3)2Pz)3]CuPPh3, [HB(3,5-(CF3)2Pz)3]AgPPh3, and [HB(3-(CF3)Pz)3]AgPPh3. Metal complexes of the fluorinated [HB(3,5-(CF3)2Pz)3]- ligand have highly electrophilic metal sites relative to their hydrocarbon analogs. This is evident from the formation of stable adducts with neutral oxygen donors such as H2O, dimethylacetamide, or thf. Furthermore, the metal compounds derived from fluorinated ligands show fairly long-range coupling between fluorines of the trifluoromethyl groups and the hydrogen, silver, or phosphorus. The solid state structures show that the fluorines are in close proximity to these nuclei, thus suggesting a possible through-space coupling mechanism. Crystal structures of the sodium adducts exhibit significant metal−fluorine interactions. The treatment of [HB(3,5-(CF3)2Pz)3]Na(H2O) with Et4NBr led to [Et4N][HB(3,5-(CF3)2Pz)3], which contains a well-separated [Et4N]+ cation and the [HB(3,5-(CF3)2Pz)3]- anion in the solid state. Crystal data with Mo Kα (λ = 0.710 73 Å) at 193 K: [HB(3,5-(CF3)2Pz)3]Na(H2O), C15H6BF18N6NaO, a = 7.992(2) Å, b = 15.049(2) Å, c = 9.934(2) Å, β = 101.16(2)°, monoclinic, P21/m, Z = 2; [{HB(3-(CF3)Pz)3}Na(thf)]2, C32H30B2F18N12Na2O2, a = 9.063(3) Å, b = 10.183(2) Å, c = 12.129(2) Å, α = 94.61(1)°, β = 101.16(2)°, γ = 95.66(2)°, triclinic, P̄1, Z = 1; [HB(3,5-(CF3)2Pz)3]Cu(DMAC), C19H13BCuF18N7O, a = 15.124(4) Å, b = 8.833(2) Å, c = 21.637(6) Å, β = 105.291(14)°, monoclinic, P21/n, Z = 4; [HB(3,5-(CF3)2Pz)3]CuPPh3, C33H19BCuF18N6P, a = 9.1671(8) Å, b = 14.908(2) Å, c = 26.764(3) Å, β = 94.891(1)°, monoclinic, P21/c, Z = 4; [HB(3,5-(CF3)2Pz)3]AgPPh3·0.5C6H14, C36H26AgBF18N6P, a = 13.929(2) Å, b = 16.498(2) Å, c = 18.752(2) Å, β = 111.439(6)°, monoclinic, P21/c, Z = 4; [Et4N][HB(3,5-(CF3)2Pz)3], C23H24BF18N7, a = 10.155(2) Å, b = 18.580(4) Å, c = 16.875(5) Å, β = 99.01(2)°, monoclinic, P21/n, Z = 4.

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