ABSTRACT
The 2,2,2-crypt salts of the Tl4Se8(4-) and [Tl2Se4(2-)]infinity1 anions have been obtained by extraction of the ternary alloy NaTl0.5Se in ethylenediamine (en) in the presence of 2,2,2-crypt and 18-crown-6 followed by vapor-phase diffusion of THF into the en extract. The [2,2,2-crypt-Na]4[Tl4Se8].en crystallizes in the monoclinic space group P2(1)/n, with Z = 2 and a = 14.768(3) angstroms, b = 16.635(3) angstroms, c = 21.254(4) angstroms, beta = 94.17(3) degrees at -123 degrees C, and the [2,2,2-crypt-Na]2[Tl2Se4]infinity1.en crystallizes in the monoclinic space group P2(1)/c, with Z = 4 and a = 14.246(2) angstroms, b = 14.360(3) angstroms, c = 26.673(8) angstroms, beta = 99.87(3) degrees at -123 degrees C. The TlIII anions, Tl2Se6(6-) and Tl3Se7(5-), and the mixed oxidation state TlI/TlIII anion, Tl3Se6(5-), have been obtained by extraction of NaTl0.5Se and NaTlSe in en, in the presence of 2,2,2-crypt and/or in liquid NH3, and have been characterized in solution by low-temperature 77Se, 203Tl, and 205Tl NMR spectroscopy. The 1J(203,205Tl-77Se) and 2J(203,205Tl-203,205Tl) couplings of the three anions have been used to arrive at their solution structures by detailed analyses and simulations of all spin multiplets that comprise the 205,203Tl NMR subspectra arising from natural abundance 205,203Tl and 77Se isotopomer distributions. The structure of Tl2Se6(6-) is based on a Tl2Se2 ring in which each thallium is bonded to two exo-selenium atoms so that these thalliums are four-coordinate and possess a formal oxidation state of +3. The Tl4Se8(4-) anion is formally derived from the Tl2Se6(6-) anion by coordination of each pair of terminal Se atoms to the TlIII atom of a TlSe+ cation. The structure of the [Tl2Se4(2-)]infinity1 anion is comprised of edge-sharing distorted TlSe4 tetrahedra that form infinite, one-dimensional [Tl2Se42-]infinity1 chains. The structures of Tl3Se6(5-) and Tl3Se7(5-) are derived from Tl4Se4-cubes in which one thallium atom has been removed and two and three exo-selenium atoms are bonded to thallium atoms, respectively, so that each is four-coordinate and possesses a formal oxidation state of +3 with the remaining three-coordinate thallium atom in the +1 oxidation state. Quantum mechanical calculations at the MP2 level of theory show that the Tl2Se6(6-), Tl3Se6(5-), Tl3Se7(5-), and Tl4Se8(4-) anions exhibit true minima and display geometries that are in agreement with their experimental structures. Natural bond orbital and electron localization function analyses were utilized in describing the bonding in the present and previously published Tl/Se anions, and showed that the Tl2Se6(6-), Tl3Se6(5-), Tl3Se7(5-), and Tl4Se8(4-) anions are electron-precise rings and cages.
ABSTRACT
The closo-[1-M(CO)(3)(eta(4)-E(9))](4-) (E = Sn, Pb; M = Mo, W) anions have been obtained by extracting the binary alloys KSn(2.05) and KPb(2.26) in ethylenediamine (en) in the presence of 2,2,2-crypt or in liquid NH(3) followed by reaction with M(CO)(3).mes (M = Mo, W) or Cr(CO)(3).tol in en or liquid NH(3) solution. Crystallization of the molybdenum and tungsten salts was induced by vapor diffusion of tetrahydrofuran into the en solutions. The salts [2,2,2-crypt-K](4)[1-M(CO)(3)(eta(4)-Sn(9))].en (M = Mo, W) crystallize in the triclinic system, space group P1, Z = 4, a = 16.187(3) A, b = 25.832(4) A, c = 29.855(5) A, alpha = 111.46(1) degrees, beta = 102.84(2) degrees, gamma = 92.87(2) degrees at -95 degrees C (M = Mo) and a = 17.018(3) A, b = 27.057(5) A, c = 28.298(6) A, alpha = 66.42(3) degrees, beta = 76.72(3) degrees, gamma = 87.27(3) degrees at 20 degrees C (M = W). The salts (CO)(3)M(en)(2)[2,2,2-crypt-K](4)[1-M(CO)(3)(eta(4)-Pb(9))].2.5en (M = Mo, W) crystallize in the triclinic system, space group P1, Z = 2, a = 16.319(3) A, b = 17.078(3) A, c = 24.827(5) A, alpha = 71.82(3) degrees, beta = 83.01(3) degrees, gamma = 81.73(3) degrees at -133 degrees C (M = Mo) and a = 16.283(4) A, b = 17.094(3) A, c = 24.872(6) A, alpha = 71.62(2) degrees, beta = 82.91(2) degrees, gamma = 81.35(2) degrees at -153 degrees C (M = W). The [1-M(CO)(3)(eta(4)-Sn(9))](4-) anions were also characterized in liquid NH(3) solution by (119)Sn, (117)Sn, and (95)Mo NMR spectroscopy. Unlike their fluxional precursor, nido-Sn(9)(4-), NMR studies show that the [1-M(CO)(3)(eta(4)-Sn(9))](4-) anions are rigid on the NMR time scale. All possible inter- and intraenvironmental couplings, J((119,117)Sn-(119,117)Sn), J((119,117)Sn-(183)W), and one J((119,117)Sn-(95)Mo) coupling, have been observed and assigned. Complete spin-spin coupling constant assignments were achieved by detailed analyses and simulations of all spin multiplets that comprise the (119)Sn and (117)Sn NMR spectra and that arise from natural abundance tin isotopomer distributions and from natural abundance (183)W, in the case of [1-W(CO)(3)(eta(4)-Sn(9))](4-). Both the solid state and solution structures of the [1-M(CO)(3)(eta(4)-Sn(9))](4-) anions are based on a closo-bicapped square antiprismatic structure in which the transition metal occupies a cap position. The cluster structures are consistent with Wade's rules for 22 (2n + 2) skeletal electron systems. Electron structure calculations at the density functional theory (DFT) level provide fully optimized geometries that are in agreement with the experimental structures. Complete assignment of the NMR spectra was also aided by GIAO calculations. The calculated vibrational frequencies of the E(9)(4-) and [1-M(CO)(3)(eta(4)-E(9))](4-) anions are also reported and are used to assign the solid-state vibrational spectra of the [1-M(CO)(3)(eta(4)-E(9))](4-) anions.