The Crystal Structure of the Sodium Pivalate Adduct Na[H(Piv)2](HPiv)2 and the Gas Phase Above Sodium Pivalate NaPivстатья
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Аннотация:Single crystals of the sodium pivalate adduct Na[H(Piv)2](HPiv)2 (HPiv = (CH3)3CCOOH) were
synthesized and structurally studied by X-ray diffraction. The compound crystallizes in the monoclinic system, a = 18.778(8) Å, b = 13.868(6) Å, c = 9.970(3) Å, = 97.28(3), Z = 4, space group C2/c, R1 = 0.0765. The coor-dination environment of sodium is a distorted octahedron NaO6 with Na–O distances of 2.401–2.497 Å. The symmetrical hydrogen bond ······ (O···O 2.464 Å) between the bridging HPiv groups and the pivalate groups gives rise to the [H(Piv)2] anions, which are bound to two terminal HPiv molecules through ···O
hydrogen bonds (O···O 2.649 Å). Due to the coordination to sodium atoms, infinite ribbons stretched along the c axis are produced. According to mass spectrometry, the saturated vapor of sodium pivalate has a complex composition, NanPivn (n = 28), dimers and tetramers being the predominant species. Individual mass spectra of the gas-phase molecules were recorded. The enthalpies of gas-phase and heterogeneous reactions were cal-culated: 2NaPiv(s) = Na2Piv2(g), r = 185 kJ/mol; 4NaPiv(s) = Na4Piv4(g), r = 224 kJ/mol; Na4Piv4(g)= 4NaPiv(g), r = 146 kJ/mol.