TY - JOUR
T1 - Doubly-Hydrated Hexafluoroacetylacetone as a Tetradentate Ligand
T2 - Synthesis, Magnetochemistry, and Thermal Transformations of a MnIII2 Complex
AU - Bouwman, Elisabeth
AU - Caulton, Kenneth G.
AU - Christou, George
AU - Folting, Kirsten
AU - Gasser, Christophe
AU - Hendrickson, David N.
AU - Huffman, John C.
AU - Lobkovsky, Emil B.
AU - Martin, James D.
AU - Michel, Philippe
AU - Tsai, Hui-Lien
AU - Xue, Ziling
PY - 1993/1/1
Y1 - 1993/1/1
N2 - A convenient synthesis of the doubly-hydrated form of hexafluoroacetylacetone (hfacH) is reported, viz. 1,1,1,5,5,5,-hexafluoropentane-2,2,4,4-tetraol (hfptH4; 1), together with the initial employment of the latter as a ligand. A reaction system in CH2Cl2 comprising [Mn3O(OAc)6(py)3](ClO4), hfacH, hfptH4, and py (py = pyridine) in a 1:6:1.5:9 ratio leads to a 58% yield of (pyH)2[Mn2(hfpt)(hfac)4] (2). Crystal data for 1 at −171 °C: monoclinic, P21/n, a = 11.108(6) Å, b = 5.104(3) Å, c = 14.736(8) Å, β = 90.30(2)°, Z = 4, V= 835.44 Å3, R (Rw) = 6.58% (7.42%). Crystal data for 2 at −130 °C: monoclinic, C2/c, a = 17.884(5) Å, b = 12.573(3) Å, c = 23.715(7) Å, β = 107.77(1)°, Z = 4, V= 5077.62 A3, R (Rw) = 9.80% (9.37%). The structure of 1 confirms a bis(gem-diol) structure with an extended-chain conformation. The anion of 2 consists of two Mn(hfac)2 fragments bridged by the hfpt4−group; the latter functions as a bidentate chelate ligand to each MnIII, employing one alkoxide oxygen atom from each gem-diolate pair. Variable-temperature magnetochemical studies have been performed on powdered samples of 2 in the range 5–320 K. THe MnIIIcenters are weakly interacting; the exchange interaction is ferromagnetic, and fitting of the data leads to the following values for the variables: J = +0.21 cm−1(employing the −2JŜ1·Ŝ2 convention), D = 0.9 cm−1, g = 1.99. Vacuum thermolysis of 2 in the range 111–150 °C yields (py)Mn(hfac)3 (3) and lesser amounts of cis-Mn(py)2(hfac)2 (5), Mn(hfac)3 (4), the tetraol (1), and a manganese(≥IV) oxide. All but the oxide are volatile and have been characterized in part by single-crystal X-ray diffraction. The mechanism of thermolysis is proposed to be initiated by proton transfer from pyH+to the tetraolate oxygen to which it is hydrogen bonded; this process facilitates the electrophilic cleavage of C/O bonds, which furnishes hfac−as well as oxide for the manganese oxide product. Crystal data for 3 (−175 °C): a = 10.487(2) Å, b = 15.790(4) Å, c = 9.356(2) Å, α = 101.78(1)°, β = 106.58(1)°, γ = 108.50(1)° with Z = 2 in space group P1̄. Crystal data for 4 (−159 °C): a = 8.879(0) Å, b = 12.941(1) Å, c = 18.748(1) Å, β = 91.35(0)° with Z = 4 in space group P21/n. Crystal data for 5: a = 9.112(3) Å, b = 16.821(6) Å, c = 16.315(5) Å, β = 105.34(5)° with Z = 4 in space group C2/c.
AB - A convenient synthesis of the doubly-hydrated form of hexafluoroacetylacetone (hfacH) is reported, viz. 1,1,1,5,5,5,-hexafluoropentane-2,2,4,4-tetraol (hfptH4; 1), together with the initial employment of the latter as a ligand. A reaction system in CH2Cl2 comprising [Mn3O(OAc)6(py)3](ClO4), hfacH, hfptH4, and py (py = pyridine) in a 1:6:1.5:9 ratio leads to a 58% yield of (pyH)2[Mn2(hfpt)(hfac)4] (2). Crystal data for 1 at −171 °C: monoclinic, P21/n, a = 11.108(6) Å, b = 5.104(3) Å, c = 14.736(8) Å, β = 90.30(2)°, Z = 4, V= 835.44 Å3, R (Rw) = 6.58% (7.42%). Crystal data for 2 at −130 °C: monoclinic, C2/c, a = 17.884(5) Å, b = 12.573(3) Å, c = 23.715(7) Å, β = 107.77(1)°, Z = 4, V= 5077.62 A3, R (Rw) = 9.80% (9.37%). The structure of 1 confirms a bis(gem-diol) structure with an extended-chain conformation. The anion of 2 consists of two Mn(hfac)2 fragments bridged by the hfpt4−group; the latter functions as a bidentate chelate ligand to each MnIII, employing one alkoxide oxygen atom from each gem-diolate pair. Variable-temperature magnetochemical studies have been performed on powdered samples of 2 in the range 5–320 K. THe MnIIIcenters are weakly interacting; the exchange interaction is ferromagnetic, and fitting of the data leads to the following values for the variables: J = +0.21 cm−1(employing the −2JŜ1·Ŝ2 convention), D = 0.9 cm−1, g = 1.99. Vacuum thermolysis of 2 in the range 111–150 °C yields (py)Mn(hfac)3 (3) and lesser amounts of cis-Mn(py)2(hfac)2 (5), Mn(hfac)3 (4), the tetraol (1), and a manganese(≥IV) oxide. All but the oxide are volatile and have been characterized in part by single-crystal X-ray diffraction. The mechanism of thermolysis is proposed to be initiated by proton transfer from pyH+to the tetraolate oxygen to which it is hydrogen bonded; this process facilitates the electrophilic cleavage of C/O bonds, which furnishes hfac−as well as oxide for the manganese oxide product. Crystal data for 3 (−175 °C): a = 10.487(2) Å, b = 15.790(4) Å, c = 9.356(2) Å, α = 101.78(1)°, β = 106.58(1)°, γ = 108.50(1)° with Z = 2 in space group P1̄. Crystal data for 4 (−159 °C): a = 8.879(0) Å, b = 12.941(1) Å, c = 18.748(1) Å, β = 91.35(0)° with Z = 4 in space group P21/n. Crystal data for 5: a = 9.112(3) Å, b = 16.821(6) Å, c = 16.315(5) Å, β = 105.34(5)° with Z = 4 in space group C2/c.
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U2 - 10.1021/ic00068a014
DO - 10.1021/ic00068a014
M3 - Article
AN - SCOPUS:0001208732
SN - 0020-1669
VL - 32
SP - 3463
EP - 3470
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 16
ER -