N,N-Dimethylaminopropylsilane: a case study on the nature of weak intramolecular Si...N interactions

N,N-Dimethylaminopropylsilane H(3)Si(CH(2))(3)NMe(2) was synthesised by the reaction of (MeO)(3)Si(CH(2))(3)NMe(2) with lithium aluminium hydride. Its solid-state structure was determined by X-ray diffraction, which revealed a five-membered ring with an SiN distance of 2.712(2) A. Investigation of the structure by gas-phase electron diffraction (GED), ab initio and density functional calculations and IR spectroscopy revealed that the situation in the gas phase is more complicated, with at least four conformers present in appreciable quantities. Infrared spectra indicated a possible SiN interaction in the Si-H stretching region (2000-2200 cm(-1)), as the approach of the nitrogen atom in the five-membered ring weakens the bond to the hydrogen atom in the trans position. Simulated gas-phase IR spectra generated from ab initio calculations (MP2/TZVPP) exhibited good agreement with the experimental spectrum. A method is proposed by which the fraction of the conformer with a five-membered ring can be determined by a least-squares fit of the calculated to experimental absorption intensities. The abundance of this conformer was determined as 23.7(6) %, in good agreement with the GED value of 24(6) %. The equilibrium SiN distance predicted by theory for the gas-phase structure was highly variable, ranging from 2.73 (MP2) to 3.15 A (HF). The value obtained by GED is 2.91(4) A, which could be confirmed by a scan of the potential-energy surface at the DF-LCCSD[T] level of theory. The nature of the weak dative bond in H(3)Si(CH(2))(3)NMe(2) can be described in terms of attractive inter-electronic correlation forces (dispersion) and is also interpreted in terms of the topology of the electron density.     

Structural and conformational properties of fluoroformic acid anhydride, FC(O)OC(O)F

The conformational properties and geometric structures of fluoroformic acid anhydride, FC(O)OC(O)F, have been studied by vibrational spectroscopy, gas electron diffraction (GED), single-crystal X-ray diffraction, and quantum chemical calculations (HF, MP2, and B3LYP methods with 6-31G* and B3LYP/6-311+G* basis sets). Satellite bands in the IR matrix spectra, which increase in intensity when the matrix gas mixture is heated prior to deposition as a matrix, indicate the presence of two conformers at room temperature. According to the electron diffraction analysis, the prevailing conformer is of C(2) symmetry with both C=O bonds synperiplanar with respect to the opposite C-O bond ([sp, sp] conformer). The minor conformer [15(5)% from IR matrix and 6(11)% from GED] is predicted by quantum chemical calculations to possess an [sp, ac] structure. FC(O)OC(O)F crystallizes in the orthorhombic system in the space group P2(1)2(1)2(1) with a = 6.527(1) angstroms, b = 7.027(1) angstroms, and c = 16.191(1) angstroms and four formula units per unit cell. In the crystal, only the [sp, sp] conformer is present, and the structural parameters are very similar to those determined by GED.     

Tautomeric and conformational properties of malonamide, NH2C(O)-CH2-C(O)NH2: electron diffraction and quantum chemical study

The geometric structure of malonamide, NH2C(O)-CH2-C(O)NH2, has been investigated by gas electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximations with 6-311++G(3df,pd) basis sets). Both GED and quantum chemistry result in the existence of a single diketo conformer in the gas phase. According to GED refinement this conformer possesses (sc,ac) conformation with one C=O bond in synclinal orientation (dihedral angle tau(O=C-C-C)=49.0(3.0) degrees) and the other C=O bond in anticlinal orientation (dihedral angle tau(O=C-C-C)=139.5(3.3) degrees). The experimental geometric parameters are reproduced very closely by the B3LYP method.     

Synthesis and characterization of open-framework niobium silicates: Rb2(Nb2O4)(Si2O6).H2O and the dehydrated phase Rb2(Nb2O4)(Si2O6)

A new niobium(V) silicate, Rb(2)(Nb(2)O(4))(Si(2)O(6)).H(2)O, has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and solid-state NMR spectroscopy. It crystallizes in the tetragonal space group P4(3)22 (No. 95) with a = 7.3431(2) A, c = 38.911(3) A, and Z = 8. Its structure contains tetrameric units of the composition Nb(4)O(18), which share corners to form a layer of niobium oxide. The Nb-O layer is a slice of the pyrochlore structure. Neighboring Nb-O layers are linked by vierer single-ring silicates generating eight-ring and six-ring channels running parallel to <100> directions, in which the Rb(+) cations and water molecules reside. The tantalum analogue was prepared and characterized by powder X-ray diffraction. Upon heating to 500 degrees C, Rb(2)(Nb(2)O(4))(Si(2)O(6)).H(2)O loses lattice water molecules, while the framework structure is retained to give the anhydrous compound Rb(2)(Nb(2)O(4))(Si(2)O(6)), whose structure was also characterized by single-crystal X-ray diffraction. The dehydrated sample absorbs water reversibly, as indicated by powder X-ray diffraction. Rb(2)(Nb(2)O(4))(Si(2)O(6)) crystallizes in the tetragonal space group I4(1) (No. 80) with a = 10.2395(6) A, c = 38.832(3) A, and Z = 16.     

Tautomeric and conformational properties of malonamic acid methyl ester, NH2C(O)-CH2-C(O)OCH3: electron diffraction and quantum chemical study

The tautomeric and conformational properties of malonamic acid methyl ester, NH2C(O)-CH2-C(O)OCH3, have been investigated by means of gas-phase electron diffraction (GED) and quantum chemical calculations (HF, B3LYP, and MP2 approximations with different basis sets up to 6-311++G(3df,pd)). Both quantum chemistry and GED at 360(8) K result in the existence of a single diketo conformer in the gas phase. According to GED refinement, this conformer possesses an (ac, sc) conformation with dihedral angles C-C-C(NH2)=O of 140.3(3.0) degrees and C-C-C(OCH3)=O of 31.1(7.2) degrees. The experimental geometric parameters are reproduced very closely by MP2 and B3LYP methods with large basis sets.     

Molecular structures of two metal tetrakis(tetrahydroborates), Zr(BH4)(4) and U(BH4)(4): equilibrium conformations and barriers to internal rotation of the triply bridging BH4 groups

The molecular structures of Zr[(mu-H)(3)BH](4) and U[(mu-H)(3)BH](4) have been investigated by density functional theory (DFT) calculations and gas electron diffraction (GED). The triply bridged bonding mode of the tetrahydroborate groups in the former is confirmed, but both DFT calculations and GED structure refinements indicate that the BH(4) groups are rotated some 12 degrees away from the orientation in which the three bridging B-H bonds are staggered with respect to the opposing ZrB(3) fragment. As a result the symmetry of the equilibrium conformation is reduced from T(d) to T. Bond distances and valence angles are as follows (DFT/GED): Zr-B = 232.2/232.4(5) pm; Zr-H(b) = 214.8/214.4(6) pm; B-H(b) = 125.3/127.8(8) pm; B-H(t) = 119.4/118.8(17) pm; angle ZrBH(b) = 66.2/65.6(3) degrees; the smallest dihedral angle of type tau(BZrBH(b)) = 48/45(2) degrees. DFT calculations on Hf(BH(4))(4) indicate that the structure of this molecule is very similar to that of the Zr analogue. Matrix-isolation IR spectroscopy and DFT calculations on U(BH(4))(4) show that while the polymeric solid-state structure is characterized by terminal triply bridging and metal-metal bridging bidentate BH(4) groups, all BH(4) groups are triply bridging in the gaseous monomer. Calculations with one of the two nonbonding 5f electrons on U occupying an a(1) and the other distributed equally among the three t(2) orbitals indicate that the equilibrium conformation has T(d) symmetry, i.e. that the three B-H(b) bonds of each tetrahydroborate group are exactly staggered with respect to the opposing UB(3) fragment with tau(BUBH(b)) = 60 degrees. Calculations including spin-orbit interactions indicate that Jahn-Teller distortions from T(d) symmetry are either absent or very small. The best agreement between observed and calculated GED intensity data was obtained for a model of T(d) symmetry, but models of T symmetry with dihedral angles tau(BUBH(b)) > 42 degrees cannot be ruled out. Bond distances and valence angles are as follows (DFT/GED): U-B = 248.8/251.2(4) pm; U-H(b) = 227.7/231.5(6) pm; B-H(b) = 126.0/131.6(5) pm, B-H(t) = 119.5/117.8(11) pm; angle UBH(b) = 65.6/63.1(3) degrees. It is suggested that the different equilibrium conformations of the three molecules are determined primarily by repulsion between bridging H atoms in different tetrahydroborate groups.     

Structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide) SF5N=S(O)F2: vibrational analysis, gas electron diffraction, and quantum chemical calculations

The molecular structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide), SF5N=S(O)F2, have been studied by vibrational spectroscopy (IR (gas) and Raman (liquid)), by gas electron diffraction (GED), and by quantum chemical calculations (MP2 and B3LYP with (6-31G(d) and 6-311+G(2df) basis sets). According to GED, the prevailing conformer possesses a syn structure (N-SF5 bond synperiplanar with respect to the bisector of the SF2 group). Splitting of the symmetric N=S=O stretching vibration in gas and liquid spectra demonstrates the presence of a second conformer (11(5)%) with anticlinal orientation of the N-SF5 bond according to quantum chemical calculations. The geometric structure, conformational properties, and vibrational frequencies are well reproduced by quantum chemical calculations.     

Gas phase structure and conformational properties of trifluoroacetic anhydride, CF3C(O)OC(O)CF3

The geometric structure of trifluoroacetic anhydride, CF₃C(O)OC(O)CF₃, has been studied by gas electron diffraction (GED) and quantum chemical calculations (MP2 and B3LYP with 6-31G^* basis sets). The GED analysis results in a single conformer with synperiplanar orientation of the two CO bonds. This analysis, however, cannot discriminate between a planar equilibrium structure (C_2v symmetry) with large amplitude torsional motions around the OC bonds and a nonplanar equilibrium structure (C₂ symmetry) with a low barrier at the planar arrangement. An effective dihedral angle φ(COCO=18(4)° is obtained. Both quantum chemical methods predict a nonplanar equilibrium structure of C₂ symmetry and φ(COCO)=16.5° and 13.9°, respectively.     

Fluoroformyl trifluoroacetyl disulfide, FC(O)SSC(O)CF3: synthesis, structure in solid and gaseous states, and conformational properties

Fluoroformyl trifluoroacetyl disulfide, FC(O)SSC(O)CF3, is prepared by quantitative reaction between FC(O)SCl and CF(3)C(O)SH. The conformational properties and geometric structure of the gaseous molecule have been studied by vibrational spectroscopy (IR(gas), Raman(liquid), IR(matrix)), gas electron diffraction (GED), and quantum chemical calculations (B3LYP and MP2 methods). The disulfide bond length derived from the GED analysis amounts 2.023(3) Angstroms, and the dihedral angle around this bond, phi(CS-SC), is 77.7(21) degrees, being the smallest dihedral angle measured for noncyclic disulfides in the gas phase. The compound exhibits a conformational equilibrium at room temperature having the most stable form C(1) symmetry with a synperiplanar (sp-sp) orientation of both carbonyl groups with respect to the disulfide bond. A second form was observed in IR spectra of the Ar matrix isolated compound at cryogenic temperatures, corresponding to a conformer that possess the carbonyl bond of the FC(O) moiety in antiperiplanar position with respect to the S-S single bond (ap-sp). A DeltaH degrees = - = 1.34(11) kcal/mol has been determined by IR(matrix) spectroscopy. The structure of single crystal of FC(O)SSC(O)CF3 was determinate by X-ray diffraction analysis at low temperature using a miniature zone melting procedure. The crystalline solid (monoclinic, P2(1)/n, a = 5.240(4)Angstroms, b = 23.319(17)Angstroms, c = 6.196(4)Angstroms, beta = 113.14(3) degrees) consists exclusively of the (sp-sp) conformation. The geometrical parameters agree with those obtained for the molecule in the gas phase.     

Preparation and properties of trifluorothioacetic acid-S-(trifluoromethyl)ester, CF3C(O)SCF3

Trifluorothioacetic acid-S-(trifluoromethyl)ester, CF3C(O)SCF3, was prepared by reacting CF3C(O)Cl and AgSCF3 at 50 degrees C. The compound was characterized by (13)C-, (19)F-NMR, UV, and vibrational spectroscopy as well as by gas electron diffraction (GED) and quantum chemical calculations (HF, MP2, and B3LYP methods 6-31G(d) and 6-311+G(2df) basis sets). GED and vibrational spectroscopy result in the presence of a single conformer with C1 symmetry and synperiplanar orientation of the S-CF3 bond relative to the CO bond. This result is in agreement with quantum chemical calculations which predict the anti conformer to be higher in energy by about 4 kcal/mol. An assignment of the IR (gas) and Raman (liquid) spectra is proposed, and the GED analysis results in the following skeletal geometric parameters (r(a) and angle(a) values with 3sigma uncertainties; these parameters are thermal averages and are not inconsistent with calculated equilibrium values): C=O = 1.202(6) A, C-C = 1.525(10) A, S-C(sp(2)) = 1.774(3) A, S-C(sp(3)) = 1.824 (3) A. O=C-C = 118.7(21) degrees, O=C-S = 127.1(15) degrees, C-S-C = 99.8 (13) degrees.     

Nanospheric [M20(OH)12(maleate)12(Me2NH)12]4+ clusters (M = Co, Ni) with O(h) symmetry

Nanospheric hydroxo-bridged clusters of [M(20)(OH)(12)(maleate)(12)(Me(2)NH)(12)](BF(4))(3)(OH)·nH(2)O (M = Co (1), Ni (2)) with O(h) symmetry were afforded under hydrothermal condition with Co(BF(4))(2)·6H(2)O/Ni(BF(4))(2)·6H(2)O and fumaric acid in a DMF/EtOH mixed solvent. They are characterized by elemental analysis, IR, and X-ray diffraction. X-ray single crystal diffraction analyses show that these two complexes are isostructural containing an ideally cubic M(8) core in that each two M atoms are doubly bridged at the edges by one OH(-) and one maleate, while these OH(-) and maleate groups are coordinated further by exterior identical 12 M atoms which construct a perfect M(12) icosahedron to encapsulate the cubic core. To our knowledge, such large clusters with O(h) symmetry are seldom. The variable-temperature magnetic susceptibility studies reveal that these two isostructures exhibit antiferromagnetic interactions.     

Tautomeric and conformational properties of dimethyl malonate, CH3OC(O)-CH2-C(O)OCH3: electron diffraction and quantum chemical study

The geometric structure of dimethyl malonate, CH₃OC(O)-CH₂-C(O)OCH₃, was studied by gas electron diffraction (GED) and quantum chemical methods. We conclude that only diketo conformers exist in the gas phase. According to the GED refinement, a mixture of two diketo conformers is present: 69(10)% (ac,ac) conformer with C₂ symmetry (both CO bonds anticlinal relative to the opposite C-C bond) and 31(10)% (sp,ac) conformer with C₁ symmetry (one CO bond with synperiplanar, the other CO bond with anticlinal orientation). Ab initio calculations, however, predict a preference of the (sp,ac) conformer rather than the (ac,ac) form.     

Fluorocarbonyl trifluoromethanesulfonate, FC(O)OSO2CF3: structure and conformational properties in the gaseous and condensed phases

Pure fluorocarbonyl trifluoromethanesulfonate, FC(O)OSO(2)CF(3), is prepared in about 70% yield by the ambient-temperature reaction between FC(O)SCl and AgCF(3)SO(3). The geometric structure and conformational properties of the gaseous molecule have been studied by gas electron diffraction (GED), vibrational spectroscopy [IR(gas), IR(matrix), and Raman(liquid)] and quantum chemical calculations (HF, MP2, and B3LYP with 6-311G basis sets); in addition, the solid-state structure has been determined by X-ray crystallography. FC(O)OSO(2)CF(3) exists in the gas phase as a mixture of trans [FC(O) group trans with respect to the CF(3) group] and gauche conformers with the trans form prevailing [67(8)% from GED and 59(5)% from IR(matrix) measurements]. In both conformers the C=O bond of the FC(O) group is oriented synperiplanar with respect to the S-O single bond. The experimental free energy difference between the two forms, DeltaG degrees = 0.49(13) kcal mol(-1) (GED) and 0.22(12) kcal mol(-1) (IR), is slightly smaller than the calculated value (0.74-0.94 kcal mol(-1)). The crystalline solid at 150 K [monoclinic, P2(1)/c, a = 10.983(1) A, b = 6.4613(6) A, c = 8.8508(8) A, beta = 104.786(2) degrees ] consists exclusively of the trans conformer.     

S-(fluoroformyl)O-(trifluoroacetyl) thioperoxide, FC(O)S-OC(O)CF3: gas-phase structure and conformational properties

The geometric structure and conformational properties of S-(fluoroformyl)O-(trifluoroacetyl) thioperoxide, FC(O)S-OC(O)CF3, were investigated by gas electron diffraction, matrix isolation infrared spectroscopy, and quantum chemical calculations (B3LYP with the 6-31G and aug-cc-pVTZ basis sets and MP2 with the 6-31G basis set). The experimental methods result in a mixture of two conformers with gauche conformation around the S-O bond. In the main conformer (82(7)% according to GED at 298 K), the C=O bond of the FC(O) group is oriented syn with respect to the S-O bond and phi(C-S-O-C) = 75(3) degrees . In the minor conformer (18(7)%), this C=O is oriented anti. Both conformers possess syn orientation of the C=O bond of the CF3C(O) group. The conformational properties and geometric parameters are reproduced reasonably well by the quantum chemical calculations, except for the S-O bond length, which is predicted too long by 0.04 A (B3LYP/aug-cc-pVTZ).     

Thorium(IV)-selenate clusters containing an octanuclear Th(IV) hydroxide/oxide core

Four Th(IV) hydroxide/oxide clusters have been synthesized from aqueous solution. The structures of [Th(8)(μ(3)-O)(4)(μ(2)-OH)(8)(H(2)O)(15)(SeO(4))(8)·7.5H(2)O] (1), [Th(8)(μ(3)-O)(4)(μ(2)-OH)(8)(H(2)O)(17)(SeO(4))(8)·nH(2)O] (2), [Th(9)(μ(3)-O)(4)(μ(2)-OH)(8)(H(2)O)(21)(SeO(4))(10)] (3), and Th(9)(μ(3)-O)(4)(μ(2)-OH)(8)(H(2)O)(21)(SeO(4))(10)·nH(2)O (4) were determined using single crystal X-ray diffraction. Each structure consists of an octanuclear core, [Th(8)O(4)(OH)(8)](16+), that is built from eight Th(IV) atoms (four Th in a plane and two up and two down) linked by four "inner" μ(3)-O and eight "outer" μ(2)-OH groups. Compounds 3 and 4 additionally contain mononuclear [Th(H(2)O)(5)(SeO(4))(4)](4-) units that link the octamers into an extended structure. The octanuclear units are invariably complexed by two selenate anions that sit in two cavities formed by four planar Th(IV) and four extra-planar Th(IV) atoms, thus making [Th(8)O(4)(OH)(8)(SeO(4))(2)](12+) a common building block in 1-4. However, changes in hydration as well selenate coordination give rise to structural differences that are observed in the extended structures of 1-4. The compounds were also characterized by Raman spectroscopy. Density functional theory calculations were performed to predict the geometries, vibrational frequencies, and relative energies of different structures. Details of the calculated structures are in good agreement with experimental results, and the calculated frequencies were used to assign the experimental Raman spectra. On the basis of an analysis of the DFT results, the compound Th(8)O(8)(OH)(4)(SeO(4))(6) was predicted to be a strong gas phase acid but is reduced to a weak acid in aqueous solution. Of the species studied computationally, the dication Th(8)O(6)(OH)(6)(SeO(6))(6)(2+) is predicted to be the most stable in aqueous solution at 298 K followed by the monocation Th(8)O(7)(OH)(5)(SeO(6))(6)(+).     

New hydrothermal synthesis and structure of Th2(PO4)2(HPO4).H2O: the first structurally characterized thorium Hydrogenphosphate

Th(2)(PO(4))(2)(HPO(4)).H(2)O was synthesized under wet hydrothermal conditions starting from a mixture of H(3)PO(3) and Th(NO(3))(4).5H(2)O. The crystal structure was solved by powder X-ray diffraction data. The unit cell parameters are a = 6.7023(8) Angstroms, b = 7.0150(8) Angstroms, c = 11.184(1) Angstroms, beta = 107.242(4) degrees, space group P2(1), and Z = 2. The structure consists of layers of both thorium atoms and PO(4) groups, alternating with a layer formed by HPO(4) entities and water molecules. By thermal treatment, this compound turns into Th(4)(PO(4))(4)P(2)O(7), a ceramic already described in the field of the immobilization of tetravalent actinides.     

((Fluoroformyl)imido)(trifluoromethyl)sulfur fluoride, FC(O)N = S(F)CF3: unexpected conformational properties

The geometric structure and conformational properties of ((fluoroformyl)imido)(trifluoromethyl)sulfur fluoride, FC(O)N = S(F)CF3, are investigated by gas electron diffraction (GED) experiments, IR (gas) spectroscopy, and quantum chemical calculations (HF, MP2, and B3LYP with 6-31G* basis sets). The GED intensities are reproduced best with a mixture of 79(12)% trans-syn and 21(12)% cis-syn conformers. "Trans/cis" describes the orientation around the S=N double bond (FC(O) group relative to sulfur substituents), and "syn" refers to the orientation of the C=O bond relative to the S=N bond. From the intensities of the C=O bands in the IR (gas) spectrum, a composition of 86(8)%:14(8)% is derived. These ratios correspond to delta G0(GED) = 0.79(36) and delta G0(IR) = 1.09(35) kcal mol-1. The preference of a trans structure, around the S=N double bond is unexpected, since all imidosulfur compounds studied thus far possess a cis configuration. The conformational properties are reproduced qualitatively correctly by all theoretical calculations. The predicted energy differences delta E(HF) = 2.41, delta E(MP2) = 0.64, and delta E(B3LYP) = 0.28 kcal mol-1 are larger or slightly smaller than the experimental values. Additional theoretical calculations (B3LYP) for several imidosulfur compounds reveal that only FC(O)N=S(F)CF3, with mixed substitution at sulfur and the FC(O) group bonded to nitrogen, prefers the trans structure.     

Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations

The molecular structures of Se(SCH(3))(2) and Te(SCH(3))(2) were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (r(h1)) are: rSe-S 219.1(1), rS-C 183.2(1), rC-H 109.6(4) pm; angleS-Se-S 102.9(3), angleSe-S-C 100.6(2), angleS-C-H (mean) 107.4(5), phiS-Se-S-C 87.9(20), phiSe-S-C-H 178.8(19) degrees for Se(SCH(3))(2), and rTe-S 238.1(2), rS-C 184.1(3), rC-H 110.0(6) pm; angleS-Te-S 98.9(6), angleTe-S-C 99.7(4), angleS-C-H (mean) 109.2(9), phiS-Te-S-C 73.0(48), phiTe-S-C-H 180.1(19) degrees for Te(SCH(3))(2). Ab initio and DFT calculations were performed at the HF, MP2 and B3LYP levels, employing either full-electron basis sets [3-21G(d) or 6-31G(d)] or an effective core potential with a valence basis set [LanL2DZ(d)]. The best fit to the GED structures was achieved at the MP2 level. Differences between GED and MP2 results for rS-C and angleS-Te-S were explained by the thermal population of excited vibrational states under the experimental conditions. All theoretical models agreed that each compound exists as two stable conformers, one in which the methyl groups are on the same side (g(+)g(-) conformer) and one in which they are on different sides (g(+)g(+) conformer) of the S-Y-S plane (Y = Se, Te). The conformational composition under the experimental conditions could not be resolved from the GED data. Despite GED R-factors and ab initio and DFT energies favouring the g(+)g(+) conformer, it is likely that both conformers are present, for Se(SCH(3))(2) as well as for Te(SCH(3))(2).     

Synthesis, magnetic properties, and magnetic structure of a natrochalcite structural variant, KM(II)2D3O2(MoO4)2 (M = Mn, Fe, or Co)

We report the syntheses, crystal structures, and magnetic properties of KMn(2)(H(3)O(2))(MoO(4))(2) (MnH), KMn(2)(D(3)O(2))(MoO(4))(2) (MnD), KFe(2)(H(3)O(2))(MoO(4))(2) (FeH), KFe(2)(D(3)O(2))(MoO(4))(2) (FeD), KCo(2)(H(3)O(2))(MoO(4))(2) (CoH), and KCo(2)(D(3)O(2))(MoO(4))(2) (CoD), and the magnetic structures of MnD and FeD. They belong to the structural variant (space group I2/m) of the mineral natrochalcite NaCu(2)(H(3)O(2))(SO(4))(2) (space group C2/m) where the diagonal within the ac-plane of the latter become one axis of the former. The structure of MnD, obtained from Rietveld refinement of a high-resolution neutron pattern taken at 300 K, consists of chains of edge-sharing octahedra bridged by MoO(4) and D(3)O(2) to form layers, which are connected to K through the oxygen atoms to form the three-dimensional (3D)-network. The X-ray powder diffraction patterns of the other two compounds were found to belong to the same space group with similar parameters. The magnetic susceptibilities of MnH and FeH exhibit long-range ordering of the moments at a Ne?el temperature of 8 and 11 K, respectively, which are accompanied by additional strong Bragg reflections in the neutron diffraction in the ordered state, consistent with antiferromagnetism. Analyses of the neutron data for MnD and FeD reveal the presence of both long- and short-range orderings and commensurate magnetic structures with a propagation vector of (?, 0, ?). The moments are antiferromagnetically ordered within the chains with alternation between chains to generate four nonequivalent nuclear unit cells. For MnD the moments are perpendicular to the chain axis (b-axis) while for FeD they are parallel to the b-axis. The overall total is a fully compensated magnetic structure with zero moment in each case. Surprisingly, for KCo(2)(D(3)O(2))(MoO(4))(2) neither additional peaks nor increase of the nuclear peaks' intensities were observed in the neutron diffraction patterns below the magnetic anomaly at 12 K which was identified to originate from a small quantity of a ferromagnetic compound, Co(2)(OH)(2)MoO(4).     

Chlorodifluoroacetyl cyanide, ClF2CC(O)CN: synthesis, structure, and spectroscopic characterization

The novel molecule difluorochloroacetyl cyanide, ClF(2)CC(O)CN, has been characterized by IR (gas phase, Ar matrix), Raman (liquid), (19)F and (13)C NMR, and photoelectron (PES) spectroscopies; photoionization mass spectrometry (PIMS); and gas electron diffraction (GED). The conformational properties of ClF(2)CC(O)CN have been studied by joint application of vibrational spectroscopy, GED, and quantum chemical calculations. The existence of two conformers is detected in the gas and liquid phases, in which the C-Cl bond adopts gauche and syn orientations with respect to the C═O group. The computed enthalpy difference is in harmony with the experimental results of the gauche being more stable than the syn conformer by ΔH° = 1.3 kcal mol(-1) (MP2/cc-pVTZ). The valence electronic properties and the possible ionization and dissociation processes of the title compound are studied using the PES and PIMS. The experimental first vertical ionization energy of 12.0 eV corresponds to the ejection of an electron of the oxygen lone pairs. Taking into account the properties and broad applications of acyl cyanides, ClF(2)CC(O)CN is a promising new precursor in preparative chemistry.