Atmospheric chemistry of n-C(x)F(2)(x)(+1)CHO (x = 1, 2, 3, 4): fate of n-C(x)F(2)(x)(+1)C(O) radicals

Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x)F(2)(x)(+1) radicals and CO. In 700 Torr O(2)/N(2) diluent at 298 +/- 3 K, the rate constant ratio, k(n-C(x)F(2)(x)(+1)C(O) + O(2) --> n-C(x)F(2)(x)(+1)C(O)O(2))/k(n-C(x)F(2)(x)(+1)C(O) --> n-C(x)F(2)(x)(+1) + CO) = (1.30 +/- 0.05) x 10(-17), (1.90 +/- 0.17) x 10(-19), (5.04 +/- 0.40) x 10(-20), and (2.67 +/- 0.42) x 10(-20) cm(3) molecule(-1) for x = 1, 2, 3, 4, respectively. In one atmosphere of air at 298 K, reaction with O(2) accounts for 99%, 50%, 21%, and 12% of the loss of n-C(x)F(2)(x)(+1)C(O) radicals for x = 1, 2, 3, 4, respectively. Results are discussed with respect to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment.     

Atmospheric chemistry of perfluoroaldehydes (CxF2x+1CHO) and fluorotelomer aldehydes (CxF2x+1CH2CHO): quantification of the important role of photolysis

The UV absorption spectra of CF(3)CHO, C(2)F(5)CHO, C(3)F(7)CHO, C(4)F(9)CHO, CF(3)CH(2)CHO, and C(6)F(13)CH(2)CHO were recorded over the range 225-400 nm at 249-297 K. C(x)F(2)(x)(+1)CHO and C(x)F(2)(x)(+1)CH(2)CHO have broad absorption features centered at 300-310 and 290-300 nm, respectively. The strength of the absorption increases with the size of the C(x)F(2)(x)(+1) group. There was no discernible (<5%) effect of temperature on the UV spectra. Quantum yields for photolysis at 254 and 308 nm were measured. Quantum yields at 254 nm were 0.79 +/- 0.09 (CF(3)CHO), 0.81 +/- 0.09 (C(2)F(5)CHO), 0.63 +/- 0.09 (C(3)F(7)CHO), 0.60 +/- 0.09 (C(4)F(9)CHO), 0.74 +/- 0.08 (CF(3)CH(2)CHO), and 0.55 +/- 0.09 (C(6)F(13)CH(2)CHO). Quantum yields at 308 nm were 0.17 +/- 0.03 (CF(3)CHO), 0.08 +/- 0.02 (C(4)F(9)CHO), and 0.04 +/- 0.01 (CF(3)CH(2)CHO). The quantum yields decrease with increasing size of the C(x)F(2)(x)(+1) group and with increasing wavelength of the photolysis light. The photolysis quantum yield at 308 nm for CF(3)CHO measured here is a factor of at least 8 greater than that reported previously. Photolysis is probably the dominant atmospheric fate of C(x)F(2)(x)(+1)CHO (x = 1-4) and is an important fate of C(x)F(2)(x)(+1)CH(2)CHO (x = 1 and 6). These results have important ramifications concerning the yield of perfluorocarboxylic acids in the atmospheric oxidation of fluorotelomer alcohols.     

Atmospheric chemistry of perfluorinated aldehyde hydrates (n-C(x)F(2x+1)CH(OH)2, x = 1, 3, 4): hydration, dehydration, and kinetics and mechanism of Cl atom and OH radical initiated oxidation

Smog chamber/Fourier transform infrared (FTIR) techniques were used to measure k(Cl+C(x)F(2x+1)CH(OH)(2)) (x = 1, 3, 4) = (5.84 +/- 0.92) x 10(-13) and k(OH+C(x)F(2x+1)CH(OH)(2)) = (1.22 +/- 0.26) x 10(-13) cm(3) molecule(-1) s(-1) in 700 Torr of N(2) or air at 296 +/- 2 K. The Cl initiated oxidation of CF(3)CH(OH)(2) in 700 Torr of air gave CF(3)COOH in a molar yield of 101 +/- 6%. IR spectra of C(x)F(2x+1)CH(OH)(2) (x = 1, 3, 4) were recorded and are presented. An upper limit of k(CF(3)CHO+H(2)O) < 2 x 10(-23) cm(3) molecule(-1) s(-1) was established for the gas-phase hydration of CF(3)CHO. Bubbling CF(3)CHO/air mixtures through liquid water led to >80% conversion of CF(3)CHO into the hydrate within the approximately 2 s taken for passage through the bubbler. These results suggest that OH radical initiated oxidation of C(x)F(2x+1)CH(OH)(2) hydrates could be a significant source of perfluorinated carboxylic acids in the environment.     

Composition Space of the (CuO, (1)/(2)Nb(2)O(5))/(HF)(x)().pyridine/H(2)O System. Structure and Synthesis of [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2-) and CuNb(py)(4)OF(5)

Single crystals of [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-) and CuNb(py)(4)OF(5) were synthesized in a (HF)(x)().pyridine/pyridine/water solution (150 degrees C, 24 h, autogeneous pressure) using CuO and Nb(2)O(5) as reagents. The compound [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-) contains clusters of [CuNb(2)(py)(4)O(2)F(10)](2)(-) anions linked through N-H(+).F hydrogen bonds to the [pyH(+)] cations. In contrast CuNb(py)(4)OF(5) is a unidimensional compound consisting only of chains, perpendicular to the c axis, of alternating [Cu(py)(4)(O/F)(2/2)](0.5+) and [NbF(4)(O/F)(2/)(2)](0.5)(-) octahedra. The chains change direction between the [110] and [1&onemacr;0] every c/2. Crystal data for [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-): tetragonal, space group I4(1)22 (No. 98),with a = 11.408(3) ?, c = 30.36(1) ?, and Z = 4. Crystal data for CuNb(py)(4)OF(5): monoclinic, space group C2/c (No. 15), with a = 10.561(3) ?, b = 13.546(6) ?, c = 16.103(4) ?, beta = 97.77(2) degrees, and Z = 4.     

Vanadium 7,7,8,8-tetracyano-p-quinodimethane (V[TCNQ]2)-based magnets

A new family of molecule-based magnets of general formula V[TCNQR(2)](2).zCH(2)Cl(2) has been synthesized and characterized (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane; R = H, Br, Me, Et, i-Pr, OMe, OEt, and OPh). In addition, solid solutions of V[TCNQ](x)()[TCNQ(OEt)(2)](2)(-)(x)().zCH(2)Cl(2) composition have been prepared. Except R = Br, magnetic ordering was observed for all materials, with T(c) values between 7.5 K (R = Me) and 106 K (R = OEt), with R = H at 52 K. The substitution of electron-donating OMe and OEt groups for H in TCNQ increased T(c), whereas the substitution of less electron-donating alkyl groups (with respect to alkoxy groups) decreased T(c). The results of MO calculations indicate that neither the spin nor charge densities of the disubstituted TCNQs are sufficiently different to explain the wide range of critical temperatures. Although the structures of the amorphous materials are not known, it is proposed that the oxygen atom of the [TCNQR(2)](*)(-) acceptor (R = OMe and OEt) and the V(II) interact to form a seven-membered ring. This interaction could stabilize the structure and enhance the magnetic coupling, leading to an increased T(c). The magnetic properties of V[TCNQ](x)()[TCNQ(OEt)(2)](2)(-)(x)().zCH(2)Cl(2) deviated from the expected linear relationship with respect to x, exhibiting magnetic behavior more characteristic of a step function in a plot of T(c) versus x.     

Synthesis and crystal chemistry of two new fluorite-related bismuth phosphates, Bi(4.25)(PO4)2O(3.375) and Bi5(PO4)2O4.5, in the Series Bi4+x(PO4)2O3+3x/2 (0.175 < or = x < or = 1)

Two new phosphates, Bi(4.25)(PO4)2O(3.375) and Bi(5)(PO(4))(2)O(4.5), have been analyzed by single-crystal X-ray diffraction in the series Bi(4+x)(PO4)2O(3+3x/2) (0.175 < or = x < or = 1). The syntheses of the compositions ranging from x = 0.175 to 0.475 were carried out by the ceramic route. The compositions from x = 0.175 to 0.475 form a solid solution with a structure similar to that of Bi(4.25)(PO4)2O(3.375), while Bi(5)(PO4)2O(4.5) was isolated from a mixture of two phases. Both of the phases form fluorite-related structures but, nevertheless, differ from each other with respect to the arrangement of the bismuth atoms. The uniqueness in the structures is the appearance of isolated PO(4) tetrahedra separated by interleaving [Bi2O2] units. ac impedance studies indicate conductivity on the order of 10(-5) S cm(-1) for Bi(4.25)(PO4)2O(3.375). Crystal data: Bi(4.25)(PO4)2O(3.375), triclinic, space group P (No. 1), with a = 7.047(1) A, b = 9.863(2) A, c = 15.365(4) A, alpha = 77.604(4) degrees, beta = 84.556(4) degrees, gamma = 70.152(4) degrees, V = 980.90(4) A3, and Z = 4; Bi(5)(PO4)2O(4.5), monoclinic, space group C2/c (No. 15), with a = 13.093(1) A, b = 5.707(1) A, c = 15.293(1) A, beta = 98.240(2) degrees, V = 1130.95(4) A(3), and Z = 8.     

New mercury vanadium phosphate hydrate Hg(4)(-)(x)()O(1-)(y)()((VO)(PO(4))(2).H(2)O with unprecedented tetrahedral oxo-cluster [Hg( approximately )(4)O( approximately )(5)

The new mercury vanadium phosphate hydrate Hg(4)(-)(x)()O(1)(-)(y)()(VO)(PO(4))(2).H(2)O has been synthesized under hydrothermal conditions. X-ray investigations led to orthorhombic symmetry, space group P2(1)2(1)2(1) (No. 19), a = 6.3632(2) A, b = 12.4155(5) A, c = 14.2292(6) A, Z = 4. The crystal structure was solved and refined from single-crystal diffractometer data to residuals R[F(2) > 2sigmaF(2)] = 0.039, R(w)(F(2)) = 0.055. The VPO framework consists of infinite one-dimensional [VO(PO(4))(2)]( infinity ) chains with corner-connected VO(6) octahedra and PO(4) tetrahedra. The chains run along the [100] direction and are held together by the unprecedented tetrahedral cationic units [Hg(4)(-)(x)()O(1)(-)(y)()](4+). Presence of Hg-Hg bonding contacts is proved from theoretical calculations.     

Structures and kinetic stabilities of the possible complexes of mononuclear Ni and (N2)x (x = 1-4)

Ab initio and density functional theory (DFT) methods have been applied to study the structures and kinetic stabilities of the possible products of the reactions of mononuclear nickel with (N(2))(x) (x = 1-4). Energy analyses show that end-on bound Ni(N(2))(x) (x = 1-4) complexes are preferred to side-on and N(4) bound ones. Several decomposition and isomerization pathways for Ni(N(2))(x) (x = 2-4) were investigated at the B3LYP/6-31G level of theory. The present study suggests that besides the four experimentally assigned complexes (NiN(2) (C(infinity)(v)), Ni(N(2))(2) (D(infinity)(h)), Ni(N(3))(2) (D(3)(h)), and Ni(N(2))(4) (T(d))), another two complexes (Ni(N(2))(4) (C(2)(v)) and Ni(N(2))(4) (D(4)(d))) are likely to be kinetically stable, while other complexes may be kinetically unstable with barrier heights of less than 30 kcal/mol. The present study also suggests that side-on bound N(2) ligand is ready to transform into the end-on bound one, while N(4) ligand is hard to transform into side-on or end-on bound N(2) ligand.     

Catalysis of the beta-elimination of HF from isomeric 2-fluoroethylpyridines and 1-methyl-2-fluoroethylpyridinium salts. Proton-activating factors and methyl-activating factors as a mechanistic test to distinguish between concerted E2 and E1cb irreversible mechanisms

Second-order rate constants, k(OH)(N), M(-)(1) s(-)(1), for the beta-elimination reactions of HF with 2-(2-fluoroethyl)pyridine (2), 3-(2-fluoroethyl)pyridine (3), and 4-(2-fluoroethyl)pyridine (4) in OH(-)/H(2)O, at 50 degrees C and mu = 1 M KCl, are = 0.646 x 10(-)(4) M(-)(1) s(-)(1), = 2.97 x 10(-)(6) M(-)(1) s(-)(1), and = 5.28 x 10(-)(4) M(-)(1) s(-)(1), respectively. When compared with the second-order rate constants for the same processes with the nitrogen-methylated substrates 1-methyl-2-(2-fluoroethyl)pyridinium iodide (5), 1-methyl-3-(2-fluoroethyl)pyridinium iodide (6), and 1-methyl-4-(2-fluoroethyl)pyridinium iodide (7), the methyl-activating factor (MethylAF) can be calculated from the ratio k(OH)(NCH)3/, and a value of 8.7 x 10(5) is obtained with substrates 5/2, a value of 1.6 x 10(3) with 6/3, and a value of 2.1 x 10(4) with 7/4. The high values of MethylAF are in agreement with an irreversible E1cb mechanism (A(N)D(E) + D(N)) for substrates 5 and 7 and with the high stability of the intermediate carbanion related to its enamine-type structure. In acetohydroxamate/acetohydroxamic acid buffers (pH 8.45-9.42) and acetate/acetic acid buffers (pH 4.13-5.13), the beta-elimination reactions of HF, with substrates 2 and 4, occur at NH(+), the substrates protonated at the nitrogen atom of the pyridine ring, even when the [NH(+)] is much lower than the [N], the unprotonated substrate, due to the high proton-activating factor (PAF) value observed: 3.6 x 10(5) for 2 and 6.5 x 10(4) for 4 with acetohydroxamate base. These high PAF values are indicative of an irreversible E1cb mechanism rather than a concerted E2 (A(N)D(E)D(N)) mechanism. Finally, the rate constant for carbanion formation from NH(+) with 2 is k(B)(NH)+ = 0.35 M(-)(1) s(-)(1), which is lower than when chlorine is the leaving group ( = 1.05 M(-)(1) s(-)(1); Alunni, S.; Busti, A. J. Chem. Soc., Perkin Trans. 2 2001, 778). This is direct experimental evidence that some lengthening of the carbon-leaving group bond can occur in the intermediate carbanion. This is a point of interest for interpreting a heavy-atom isotope effect.     

The gas phase tropospheric removal of fluoroaldehydes (CxF2x+1CHO, x = 3, 4, 6)

The rate coefficient of the OH reaction with the perfluoroaldehydes C(3)F(7)CHO and C(4)F(9)CHO have been determined in the temperature range 252-373 K using the pulsed laser photolysis-laser induced fluorescence (PLP-LIF) method: k(C(3)F(7)CHO+OH) = (2.0 +/- 0.6) x 10(-12) exp[-(369 +/- 90)/T] and k(C(4)F(9)CHO+OH) = (2.0 +/- 0.5) x 10(-12) exp[-(356 +/- 70)/T] cm(3) molecule(-1) s(-1), corresponding to (5.8 +/- 0.6) x 10(-13) and (6.1 +/- 0.5) x 10(-13) cm(3) molecule(-1) s(-1), respectively, at 298 K. The UV absorption cross sections of these two aldehydes and CF(3)(CF(2))(5)CH(2)CHO have been measured over the range 230-390 nm at 298 K and also at 328 K for CF(3)(CF(2))(5)CH(2)CHO. The obtained results for C(3)F(7)CHO and C(4)F(9)CHO are in good agreement with two recent determinations but the maximum value of the absorption cross section for CF(3)(CF(2))(5)CH(2)CHO is over a factor of two lower than the single one recently published. The photolysis rates of C(3)F(7)CHO, C(4)F(9)CHO and CF(3)(CF(2))(5)CHO have been measured under sunlight conditions in the EUPHORE simulation chamber in Valencia (Spain) at the beginning of June. The photolysis rates were, respectively, J(obs) = (1.3 +/- 0.6) x 10(-5), (1.9 +/- 0.8) x 10(-5) and (0.6 +/- 0.3) x 10(-5) s(-1). From the J(obs) measurements and calculated photolysis rate J(calc), assuming a quantum yield of unity across the atmospheric range of absorption of the aldehydes, quantum yields J(obs)/J(calc) = (0.023 +/- 0.012), (0.029 +/- 0.015) and (0.046 +/- 0.028) were derived for the photodissociation of C(3)F(7)CHO, C(4)F(9)CHO and CF(3)(CF(2))(5)CHO, respectively. The atmospheric implication of the data obtained in this work is discussed. The main conclusion is that the major atmospheric removal pathway for fluoroaldehydes will be photolysis, which under low NO(x) conditions, may be a source of fluorinated carboxylic acids in the troposphere.     

Bridging nitrate groups in [Mn(4)O(3)(NO(3))(O(2)CMe)(3)(R(2)dbm)(3)] (R = H, Et) and [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)): acidolysis routes to tetranuclear manganese carboxylate complexes

New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)(O(2)CEt)(6)(dbm)(2)] (8) with HX (X(-) = F(-), Cl(-), Br(-), NO(3)(-)); high-yield routes to 1 and 8 are also described. The X(-) = NO(3)(-) complexes [Mn(4)O(3)(NO(3))(O(2)CR)(3)(R'(2)dbm)(3)] (R = Me, R' = H (6); R = Me, R' = Et (7); R = Et, R' = H (12)) represent the first synthesis of the [Mn(4)O(3)(NO(3))](6+) core, which contains an unusual eta(1):mu(3)-NO(3)(-) group. Treatment of known [Mn(4)O(2)(O(2)CEt)(7)(bpy)(2)](ClO(4)) with HNO(3) gives [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)) (15) containing a eta(1):eta(1):mu-NO(3)(-) group bridging the two body Mn(III) ions of the [Mn(4)O(2)](8+) butterfly core. Complex 7 x 4CH(2)Cl(2) crystallizes in space group P2(1)2(1)2(1) with (at -168 degrees C) a = 21.110(3) A, b = 22.183(3) A, c = 15.958(2) A, Z = 4, and V = 7472.4(3) A(3). Complex 15 x (3)/(2)CH(2)Cl(2) crystallizes in space group P2(1)/c with (at -165 degrees C) a = 26.025(4) A, b = 13.488(2) A, c = 32.102(6) A, beta = 97.27(1) degrees, Z = 8, and V = 11178(5) A(3). Complex 7 contains a [Mn(4)(mu(3)-O)(3)(mu(3)-NO(3))](6+) core (3Mn(III), Mn(IV)) as seen for previous [Mn(4)O(3)X](6+) complexes. Complex 15 contains a butterfly [Mn(4)(mu(3)-O)(2)](8+) core. (1)H NMR spectra have been recorded for all complexes reported in this work and the various resonances assigned. All complexes retain their structural integrity on dissolution in chloroform and dichloromethane. Magnetic susceptibility (chi(M)) data were collected on 12 in the 5-300 K range in a 10.0 kG (1 T) field. Fitting of the data to the theoretical chi(M) vs T expression appropriate for a [Mn(4)O(3)X](6+) complex of C(3)(v)() symmetry gave J(34) = -23.9 cm(-)(1), J(33) = 4.9 cm(-)(1), and g = 1.98, where J(34) and J(33) refer to the Mn(III)Mn(IV) and Mn(III)Mn(III) pairwise exchange interactions, respectively. The ground state of the molecule is S = 9/2, as found previously for other [Mn(4)O(3)X](6+) complexes. This was confirmed by magnetization data collected at various fields and temperatures. Fitting of the data gave S = 9/2, D = -0.45 cm(-1), and g = 1.96, where D is the axial zero-field splitting parameter.     

The crystal chemistry of Ca(10-y)(SiO4)3(SO4)3Cl(2-x-2y)F(x) ellestadite

Fluor-chlorellestadite solid solutions Ca(10)(SiO(4))(3)(SO(4))(3)Cl(2-x)F(x), serving as prototype crystalline matrices for the fixation of hazardous fly ash, were synthesized and characterized by powder X-ray and neutron diffraction (PXRD and PND), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The lattice parameters of the ellestadites vary linearly with composition and show the expected shrinkage of unit cell volume as fluorine (IR = 1.33 ?) displaces chlorine (IR = 1.81 ?). FTIR spectra indicate little or no OH(-) in the solid solutions. All compositions conform to P6(3)/m symmetry where F(-) is located at the 2a (0, 0, (1)/(4)) position, while Cl(-) is displaced out of the 6h Ca(2) triangle plane and occupies 4e (0, 0, z) split positions with z ranging from 0.336(3) to 0.4315(3). Si/S randomly occupy the 6h tetrahedral site. Ellestadites rich in Cl (x ≤ 1.2) show an overall deficiency in halogens (<2 atom per formula unit), particularly Cl as a result of CaCl(2) volatilization, with charge balance achieved by the creation of Ca vacancies (Ca(2+) + 2Cl(-) →□(Ca) + 2□(Cl)) leading to the formula Ca(10-y)(SiO(4))(3)(SO(4))(3)Cl(2-x-2y)F(x). For F-rich compositions the vacancies are found at Ca(2), while for Cl-rich ellestadites, vacancies are at Ca(1). It is likely the loss of CaCl(2) which leads tunnel anion vacancies promotes intertunnel positional disorder, preventing the formation of a P2(1)/b monoclinic dimorph, analogous to that reported for Ca(10)(PO(4))(6)Cl(2). Trends in structure with composition were analyzed using crystal-chemical parameters, whose systematic variations served to validate the quality of the Rietveld refinements.     

Synthesis, crystal structure, and high-precision high-frequency and -field electron paramagnetic resonance investigation of a manganese(III) complex: [Mn(dbm)2(py)2](ClO4)

The complex [Mn(dbm)(2)(py)(2)](ClO(4)) (dbm = anion of 1,3-diphenyl-1,3-propanedione (dibenzoylmethane), py = pyridine) was synthesized and characterized by X-ray crystallography. It has tetragonally distorted geometry with the axial positions occupied by the py ligands and the equatorial positions by the dbm ligands. This mononuclear complex of high-spin Mn(III) (3d(4), S = 2) was studied by high-frequency and -field electron paramagnetic resonance (HFEPR) both as a solid powder and in frozen dichloromethane solution. Very high quality HFEPR spectra were recorded over a wide range of frequencies. The complete dataset of resonant magnetic fields versus transition energies was analyzed using automated fitting software. This analysis yielded the following spin Hamiltonian parameters (energies in cm(-1)): D = -4.504(2), E = -0.425(1), B(4)(0) = -1.8(4) x 10(-4), B(4)(2) = 7(3) x 10(-4), B(4)(4) = 48(4) x 10(-4), g(x) = 1.993(1), g(y) = 1.994(1), and g(z) = 1.983(1), where the B(4)(n) values represent fourth-order zero-field splitting terms that are generally very difficult to extract, even from single-crystal measurements. The results here demonstrate the applicability of HFEPR at high-precision measurements, even for powder samples. The zero-field splitting parameters determined here for [Mn(dbm)(2)(py)(2)](+) are placed into the context of those determined for other mononuclear complexes of Mn(III).     

Further evidence for the tetraoxoiodate(V) anion,IO(4)(3-): hydrothermal syntheses and structures of Ba[(MoO(2))(6)(IO(4))(2)O(4)] x H(2)O and Ba(3)[(MoO(2))(2)(IO(6))(2)] x 2H(2)O

The hydrothermal reaction of MoO(3) with BaH(3)IO(6) at 180 degrees C for 3 days results in the formation of Ba[(MoO(2))(6)(IO(4))(2)O(4)] x H(2)O (1). Under similar conditions, the reaction of Ba(OH)(2) x 8H(2)O with MoO(3) and Ba(IO(4))(2) x 6H(2)O yields Ba(3)[(MoO(2))(2)(IO(6))(2)] x 2H(2)O (2). The structure of 1, determined by single-crystal X-ray diffraction, consists of corner- and edge-sharing distorted MoO(6) octahedra that create two-dimensional slabs. Contained within this molybdenum oxide framework are approximately C(2v) tetraoxoiodate(V) anions, IO(4)(3-), that are involved in bonding with five Mo(VI) centers. The two equatorial oxygen atoms of the IO(4)(3-) anion chelate a single Mo(VI) center, whereas the axial atoms are mu(3)-oxo groups and complete the octahedra of four MoO(6) units. The coordination of the tetraoxoiodate(V) anion to these five highly electropositive centers is probably responsible for stabilizing the substantial anionic charge of this anion. The Ba(2+) cations separate the layers from one another and form long ionic contacts with neighboring oxygen atoms and a water molecule. Compound 2 also contains distorted MoO(6) octahedra. However, these solely edge-share with octahedral hexaoxoiodate(VII), IO(6)(5-), anions to form zigzagging one-dimensional, (1)(infinity)[(MoO(2))(IO(6))](3-), chains that are polar. These chains are separated from one another by Ba(2+) cations that are coordinated by additional water molecules. Bond valence sums for the iodine atoms in 1 and 2 are 5.01 and 7.03, respectively. Crystallographic data: 1, monoclinic, space group C2/c, a = 13.584(1) A, b = 7.3977(7) A, c = 20.736(2) A, beta = 108.244(2) degrees, Z = 4; 2, orthorhombic, space group Fdd2, a = 13.356(7) A, b = 45.54(2) A, c = 4.867(3) A, Z = 8.     

Tuning intermolecular magnetic exchange interactions in the solids C(x)F(2)(x)(CNSSS)(2)(AsF(6))(2): structural, EPR, and magnetic characterization of dimeric (x = 2, 4) diradicals

A series of diradical containing salts CxF2x(CNSSS)2(**2+0(AsF6-)2 {x = 2, 1[AsF6]2; x = 3, 3[AsF6]2; x = 4, 2[AsF6]2} have been prepared. 1[AsF6]2 and 2[AsF6]2 were fully characterized by X-ray, variable-temperature magnetic susceptibility, and solid-state EPR measurements, further allowing us to extend the number of examples of the family of rare 7pi RCNSSS(*+) radical cations. 1[AsF6]2: a = 6.5314(7) A, b = 7.5658(9) A, c = 9.6048(11) A, alpha = 100.962(2) degrees , beta = 96.885(2) degrees , gamma = 107.436(2) degrees , triclinic, space group P, Z = 1, T = 173 K. 2[AsF6]2: a = 10.6398(16) A, b = 7.9680(11) A, c = 12.7468(19) A, beta = 99.758(2) degrees , monoclinic, space group P21/c, Z = 2, T = 173 K. In the solid-state, CxF2x(CNSSS)2(**2+) (x = 2, 4) formed one-dimensional polymeric chains of dications containing discrete centrosymmetric radical pairs in which radicals were linked by four centered two-electron pi*-pi* bonds [12+, d(S...S) = 3.455(1) A; 22+, d(S...S) = 3.306(2) A]. The exchange interactions in these bonds were determined to be -500 +/- 30 and -900 +/- 90 cm-1, by variable temperature magnetic susceptibility measurements, respectively, providing rare experimental data on the singlet-triplet gaps in the field of thiazyl radicals. For 2[AsF6]2, the thermally excited triplet state was unambiguously characterized by EPR techniques [/D/ = 0.0254(8) cm(-1), /E/ = 0.0013(8) cm(-1)]. These experimental data implied a weakly associated nature of the radical moieties contained in the solids 1[AsF6]2 and 2[AsF6]2. Computational analysis of the dimerization process is presented, and we show that the 2c 4 electron pi*-pi* bonds in 1[AsF6]2 and 2[AsF6]2 have ca. 50% and 40% diradical character, respectively. In contrast, 3[AsF6]2.SO2, containing diradical C3F6(CNSSS)2(**2+) with an odd number of CF2 spacers, showed magnetic behavior that was consistent with the presence of monomeric radical centers in the solid state.     

Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7): a structure with tunable density of Na(+) vacancies

A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions.     

High-frequency EPR study of a new mononuclear manganese(III) complex:. [(terpy)Mn(N3)3] (terpy = 2,2':6',2'-terpyridine)

The isolation and structural characterization of [(terpy)Mn(III)(N3)3], complex 1, is reported (terpy = 2,2':6',2' '-terpyridine). Complex 1, a product of the reaction between the mixed-valence dimer [(terpy)(H2O)Mn(III)(O)2Mn(IV)(OH2)(terpy)](NO3)3 and NaN3, crystallizes in a triclinic system, space group P1, a = 8.480(1) A, b = 8.9007(2) A, c = 12.109(2) A, alpha = 93.79(1) degrees, beta = 103.17(1) degrees, gamma = 103.11(1) degrees, and Z = 2. Complex 1 exhibits a Jahn-Teller distortion of the octahedron characteristic of a six-coordinated high-spin Mn(III). A vibrational spectroscopic study was performed. The nu(asym)(N3) mode of complex 1 appears in the IR as a strong band at 2035 cm(-1) with a less intense feature at 2072 cm(-1), and in the FT-Raman as a strong band at 2071 cm(-1) with a weaker broad band at 2046 cm(-1). The electronic properties of complex 1 were investigated using a high-field and high-frequency EPR study (190-475 GHz). The different spin Hamiltonian parameters have been determined (D = -3.29 (+/-0.01) cm(-1), E = 0.48 (+/-0.01) cm(-1), E '= 0.53 (+/-0.01) cm(-1), g(x) = 2.00 (+/-0.005), g(y) = 1.98 (+/-0.005), g(z) = 2.01 (+/-0.005)). These parameters are in agreement with the geometry of complex 1 observed in the crystal structure, a D < 0 related to the elongated distortion, and a value of E/D close to 0.2 as expected from the highly distorted octahedron. The two values of the E-parameter are explained by the presence of two slightly different structural forms of complex 1 in the crystal lattice. A second hypothesis was explored to explain the experimental data. The calculation for the simulation was done taking into account that the g and D tensors are not collinear due to the low symmetry of complex 1. In that case, the spin Hamiltonian parameters found are D = -3.29 (+/-0.01) cm(-1), E = 0.51 (+/-0.01) cm(-1), g(x) = 2.00 (+/-0.005), g(y) = 1.98 (+/-0.005), and g(z) = 2.01 (+/-0.005).     

Syntheses and Vibrational and (13)C MAS-NMR Spectra of Bis(carbonyl)mercury(II) Undecafluorodiantimonate(V) ([Hg(CO)(2)][Sb(2)F(11)](2)) and of Bis(carbonyl)dimercury(I) Undecafluorodiantimonate ([Hg(2)(CO)(2)][Sb(2)F(11)](2)) and the Molecular Structure of [Hg(CO)(2)][Sb(2)F(11)](2)

The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)(2)][Sb(2)F(11)](2), and that of the corresponding mercury(I) salt [Hg(2)(CO)(2)][Sb(2)F(11)](2) are accomplished by the solvolyses of Hg(SO(3)F)(2) or of Hg(2)F(2), treated with fluorosulfuric acid, HSO(3)F, in liquid antimony(V) fluoride at 80 or 60 degrees C, respectively, in an atmosphere of CO (500-800 mbar). The resulting white solids are the first examples of metal carbonyl derivatives formed by a post-transition element. Both salts are characterized by FT-IR, FT-Raman, and (13)C-MAS-NMR spectroscopy. For [Hg(CO)(2)][Sb(2)F(11)], unprecedentedly high CO stretching frequencies (nu(av) = 2279.5 cm(-)(1)) and stretching force constant (f(r) = 21.0 +/- 0.1) x 10(2) Nm(-)(1)) are obtained. Equally unprecedented is the (1)J((13)C-(199)Hg) value of 5219 +/- 5 Hz observed in the (13)C MAS-NMR spectrum of the (13)C labeled isotopomers at delta = 168.8 +/- 0.1 ppm. The corresponding values (nu(av) = 2247 cm(-)(1), f(r) = (20.4 +/- 0.1) x 10(2) Nm(-)(1), (1)J((13)C-(199)Hg) = 3350 +/- 50 Hz and (2)J((13)C-(199)Hg) 850 +/- 50 Hz) are found for [Hg(2)(CO)(2)][Sb(2)F(11)](2), which has lower thermal stability (decomposition point in a sealed tube is 140 degrees C vs 160 degrees C for the Hg(II) compound) and a decomposition pressure of 8 Torr at 20 degrees C. The mercury(I) salt is sensitive toward oxidation to [Hg(CO)(2)][Sb(2)F(11)](2) during synthesis. Both linear cations (point group D(infinity)(h)()) are excellent examples of nonclassical (sigma-only) metal-CO bonding. Crystal data for [Hg(CO)(2)][Sb(2)F(11)](2): monoclinic, space group P2(1)/n; Z = 2; a = 7.607(2) ?; b = 14.001(3) ?; c = 9.730(2) ?; beta = 111.05(2) degrees; V = 967.1 ?(3); T = 195 K; R(F) = 0.035 for 1983 data (I(o) >/= 2.5sigma(I(o))) and 143 variables. The Hg atom lies on a crystallographic inversion center. The Hg-C-O angle is 177.7(7) degrees. The length of the mercury-carbon bond is 2.083(10) ? and of the C-O bond 1.104(12) ? respectively. The structure is stabilized in the solid state by a number of significant secondary interionic Hg- - -F and C- - -F contacts.     

A three-dimensional, noninterpenetrating metal--organic framework with the moganite topology: a simple (4(2)x6(2)x8(2))(4x6(4)x8)(2) net containing two kinds of topologically nonequivalent points

Self assembly of Cu(2+) with the multifunctional ligand 2-(4-pyridyl)thiazole-4-carboxylic acid (Pytac) affords the neutral 3D coordination polymer [Cu(3)(Pytac)(6)](H(2)O)(14) (hereafter, SZL-1), which has the rare moganite topology. The mineral moganite has a topology that is closely related to the well-known quartz topology, but the two topologies are differentiated by the number of topologically inequivalent nodes. Whereas only one kind of node is present in quartz, two types of topologically inequivalent nodes are present in moganite. The title compound, which has three vertices in its repeat unit, has two types of topologically inequivalent nodes with the overall vertex symbol (4(2)x6(2)x8(2))(4x6(4)x8)(2) corresponding to the moganite net. Prior to this report, few metal-organic framework materials (MOFs) have been found to contain more than one type of node, and SZL-1 is the first MOF with the moganite topology.     

Metamagnetism in cobalt phosphates with pillared layer structures: [Co3(pyz)(HPO4)2F2] and [Co3(4,4'-bpy)(HPO4)2F2].xH2O

Two new cobalt phosphates, [Co(3)(pyz)(HPO(4))(2)F(2)] (1) and [Co(3)(4,4'-bpy)(HPO(4))(2)F(2)].xH(2)O (x approximately 0.7) (2), have been synthesized by hydrothermal methods in the presence of aromatic amines, and characterized by single-crystal X-ray diffraction and magnetic susceptibility. Their structures consist of neutral sheets of fluorinated cobalt phosphate which are pillared through pyrazine and 4,4'-bipyridine molecules to form 3D frameworks. The structures are related to that of the mineral lazulite. Both compounds show long-range antiferromagnetic ordering below 15 K and metamagnetic behaviors. Compound 1 reveals a two-step magnetic phase transition. Crystal data for 1: monoclinic, space group C2/c (No. 15), a = 21.809(4) A, b = 7.370(1) A, c = 7.395(1) A, beta = 103.753(3) degrees, and Z = 4. Crystal data for 2 are the same as those for 1 except a = 29.940(2) A, b = 7.4421(5) A, c = 7.4170(5) A, and beta = 93.444(1) degrees.