Gaseous HgH2, CdH2, and ZnH2

Gaseous HgH2, CdH2, and ZnH2 molecules were synthesized by the direct gas-phase reaction of excited mercury, cadmium, and zinc atoms with molecular hydrogen. The molecules were identified by their high-resolution infrared emission spectra, and the metal-hydrogen bond lengths were determined from the rotational analysis of the antisymmetric stretching fundamental bands.     

Reactions of 1,3-dioxacycloalkanes and their 2-arsena, 2-bora, 2-germa, 2-sila,and 2-thia analogs with nitriles

New reactions of five-, six-, and seven-membered 1,3-dioxacycloalkanes and their 2-arsena, 2-bora, 2-germa, 2-sila, and 2-thia analogs with nitriles giving rise to 1,3-oxazacycloalkanes and then to amino alcohols are surveyed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1499–1507, July, 2005.     

Sulfur and chlorine K-shell x-ray absorption spectra of SCl2, S2Cl2, SOCl2, and SO2Cl2

The X-ray absorption spectra of dichlorosulfide (SCl₂), dichlorodisulfide (S₂Cl₂), thionyl chloride (SOCl₂) and sulfuryl chloride (SO₂Cl₂) have been recorded with synchrotron radiation in the regions of S 1s and Cl 1s excitation and ionization. Ionization current spectra of SOCl₂ and SO₂Cl₂ in the Cl 1s regions are also presented. The main spectral features are assigned to K-shell excitations to σ^* orbitals associated with the SCl, SS and SO bonds in these molecules.     

Structure and properties of single crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

Single crystals of CaMg(2)Bi(2), EuMg(2)Bi(2), and YbMg(2)Bi(2) were obtained from a Mg-Bi flux cooled to 650 °C. These materials crystallize in the CaAl(2)Si(2) structure-type (P ?3m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg(2)Bi(2) displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg(2)Bi(2) reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10(19) cm(-3) for CaMg(2)Bi(2), 1.7(1) × 10(19) cm(-3) for EuMg(2)Bi(2), and 4.6(7) × 10(19) cm(-3) for YbMg(2)Bi(2), which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ρ(300 K)/ρ(10 K) ≤ 1.6 in all cases, indicating significant defect scattering.     

Syntheses,Crystal Structure,and Properties of Hf2Ni2In,Hf2Ni2Sn,Hf2Cu2In,and Hf2Pd2In with Ordered Zr3Al2 Type Structure

Hf₂Ni₂In, Hf₂Ni₂Sn, Hf₂Cu₂In, and Hf₂Pd₂In were synthesized by reacting the elements in an arc-melting furnace under argon and subsequent annealing at 970 K. They crystallize with an ordered Zr₃Al₂ type structure, space group P4₂/mnm which was refined from single crystal X-ray data for Hf₂Ni₂In (a = 713.9(1) pm, c = 660.4(2) pm, wR2 = 0.0665, 513 F² values) and Hf₂Ni₂Sn (a = 703.1(1) pm, c = 676.1(2) pm, wR2 = 0.0423, 507 F² values) with 18 parameters for each refinement. The lattice constants for Hf₂Cu₂In and Hf₂Pd₂In are a = 715.5(1) pm, c = 677.0(1) pm and a = 742.6(1) pm, c = 679.4(2) pm, respectively. The structures may be considered as an intergrowth of distorted CsCl- and AlB₂-like slabs. Magnetic susceptibility measurements indicate Pauli paramagnetism for Hf₂Ni₂In and Hf₂Ni₂Sn, which is consistent with the metallic conductivity observed for Hf₂Ni₂In. ¹¹⁹Sn Mössbauer spectroscopy of Hf₂Ni₂Sn shows one signal with an isomer shift of δ = 1.59(1) mm/s subjected to quadrupole splitting of δE_q = 0.81(1) mm/s.     

Syntheses,Spectroscopic Studies,and Crystal Structures of Me2Sn(O2PPh2)2, Ph2Pb(O2PMe2)2, and Ph2Pb(O2PPh2)2

Me₂Sn(O₂PPh₂)₂ ( 1 ), Ph₂Pb(O₂PMe₂)₂ ( 2 ), and Ph₂Pb(O₂PPh₂)₂ ( 3 ) have been synthesized by the reactions of Me₂SnCl₂ or Ph₃PbCl with the corresponding diorganophosphinic acid in methanol. X‐ray diffraction studies show that the diorganophosphinate groups behave as double bridges between the metal atoms leading to polymeric ring‐chain structures with M₂O₄P₂ (M = Pb, Sn) eight‐membered rings. The organic groups bonded to the metal atoms are in trans‐position in the resulting octahedral arrangement around the metal atoms. The IR and the mass spectra were reported and discussed.     

Trace Element Analysis of USGS Standards AGV2, BCR2, BHVO2, DTS2 and GSP2 by INAA

Five second generation USGS standards AGV2, BCR2, BHVO2, DTS2 and GSP2 were analyzed for trace elements by instrumental neutron activation analysis. Abundances of the rare earth elements La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and eight other elements Co, Cr, Cs, Hf, Na, Sc, Ta and Th were determined in all samples, except for DTS2 which was analyzed only for Co, Cr, Na and Sc. Experimental precision and accuracy were evaluated. In general abundances of trace elements in this new generation of USGS standards are similar to the earlier standards. Abundances of Cr are, however, substantially higher in AGV2, BCR2, GSP2 and especially DTS2.     

CO2 laser-induced decomposition of propan-2-ol,butan-2-ol,pentan-2-ol,pentan-3-ol,and hexan-2-ol

The pulsed CO₂ laser-induced decompositions of propan-2-ol, butan-2-ol, pentan-2-ol, pentan-3-ol, and hexan-2-ol in the gas phase have been investigated. Like ethanol which we examined previously [1] the absorption cross section of propan-2-ol for pulsed 9R14 radiation increases with pressure at low pressures, an effect attributed to rotational hole-filling. In contrast the absorption cross section of butan-2-ol (10R24) has only a small pressure dependence and those of pentan-2-ol (9R26), pentan-3-ol (10R14), and hexan-2-ol (9P20) show little or no variation with pressure in the range 0.1–5.0 torr. Decomposition products have been investigated at low pressure where the excitation of the alkanols was essentially collision free. The observed products for all the alkanols can be rationalized on the basis of primary dehydration and C? C fission channels, with minor contributions from other molecular eliminations. © 1994 John Wiley & Sons, Inc.     

The confirmation of accurate combination of functional and basis set for transition‐metal dimers: Fe2, Co2, Ni2, Ru2, Rh2, Pd2, Os2, Ir2, and Pt2

Eight kinds of density functionals named B3LYP, PBE1PBE, B1B95, BLYP, BP86, G96PW91, mPWPW91, and SVWN along with two different valence basis sets (LANL2DZ and CEP‐121g) are employed to study the transition‐metal dimers for the elements of group VIII. By comparing the equilibrium bond distances, vibrational frequencies, and dissociation energies of the ground state of these dimers with the available experimental values and theoretical data, we show that the “pure” DFT methods (G96PW91, BLYP, and BP86) with great‐gradient approximation always give better results relative to the hybrid HF/DFT schemes (B3LYP, PBE1PBE, and B1B95). The striking case found by us is that the G96PW91 functional, which is not tested in previous systemic studies, always predicts the dissociation energy to be well. The Ru₂ and Os₂ dimers are sensitive to not only the functionals employed but also the valence basis sets adopted. The natural bond orbital population is analyzed, and the molecular orbitals of the unpaired electrons are determined. Furthermore, our results indicate that the s and d orbitals of these dimers always hybridize with each other except for Rh₂ and Pt₂ molecules. And by analyzing the electron configuration of the bonding atom, the dissociation limit of the ground state is obtained. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers

Very recently, two-dimensional nanosheets of MoSe(2), MoTe(2) and WS(2) were successfully synthesized experimentally [Science, 2011, 331, 568]. In the present work, the electronic and magnetic properties of perfect, vacancy-doped, and nonmetal element (H, B, C, N, O, and F) adsorbed MoSe(2), MoTe(2) and WS(2) monolayers are systematically investigated by means of first-principles calculations to give a detailed understanding of these materials. It is found that: (1) MoSe(2), MoTe(2) and WS(2) exhibit surprising confinement-induced indirect-direct-gap crossover; (2) among all the neutral native vacancies of MoSe(2), MoTe(2) and WS(2) monolayers, only the Mo vacancy in MoSe(2) can induce spin-polarization and long-range antiferromagnetic coupling; (3) adsorption of nonmetal elements on the surface of MoSe(2), MoTe(2) and WS(2) nanosheets can induce a local magnetic moment; H-absorbed WS(2), MoSe(2), and MoTe(2) monolayers and F-adsorbed WS(2) and MoSe(2) monolayers show long-range antiferromagnetic coupling between local moments even when their distance is as long as ～12 ?. These findings are a useful addition to the experimental studies of these new synthesized two-dimensional nanosheets, and suggest a new route to facilitate the design of spintronic devices for complementing graphene. Further experimental studies are expected to confirm the attractive predictions.     

Synthesis, structure, and properties of BaAl2Si2

Single crystals of BaAl2Si2 were grown from an Al molten flux and characterized using single-crystal X-ray diffraction at 10 and 90 K and neutron diffraction at room temperature. BaAl2Si2 crystallizes with the alpha-BaCu2S2 structure type (Pnma), is isostructural with alpha-BaAl2Ge2, and is an open 3D framework compound, where Al and Si form a covalent cagelike network with Ba2+ cations residing in the cages. BaAl2Si2 has a unit cell of a=10.070(3) A, b=4.234(1) A, and c=10.866(3) A, as determined by room-temperature single-crystal neutron diffraction (R1=0.0533, wR2=0.1034). The structure as determined by single-crystal neutron and X-ray diffraction (10 and 90 K) indicates that BaAl2Si2 (Pnma) is strictly isostructural to other (alpha)-BaCu2S2-type structures, requiring site specificity for Al and Si. Unlike BaAl2Ge2, no evidence for an alpha to beta (BaZn2P2-type, I4/mmm) phase transition was observed. This compound shows metallic electronic resistivity and Pauli paramagnetic behavior.     

Crystal structures and hydrogen bonding schemes in four benzamide derivatives (2-hydroxy-benzamide, 2-hydroxy-thiobenzamide, 2-hydroxy-N,N-dimethyl-benzamide,and 2-Hydroxy-N,N-dimethyl-thiobenzamide)

Summary 2-Hydroxy-benzamide, C₇H₇NO₂; monoclinic; I2/a-C _2h ⁶ ;a=12.901 (2),b=4.982 (1),c=20.987 (3) Å; =91.50 (2)°;Z=8. 2-Hydroxy-thiobenzamide, C₇H₇NOS; monoclinic; P2₁/n-C _2h ⁵ ;a=13.508 (5),b=6.780 (2),c=15.878 (6) Å; =93.74 (5)°;Z=8. 2-Hydroxy-N,N-dimethyl-benzamide, C₉H₁₁NO₂; orthorhombic; Pbca-D _2h ¹⁵ ;a=11.752 (2),b=16.680 (3),c=9.079 (2) Å;Z=8. 2-Hydroxy-N,N-dimethyl-thiobenzamide, C₉H₁₁NOS; monoclinic; P2₁/c-C _2h ⁵ ;a=6.983 (1),b=11.652 (3),c=11.704 (3) Å; =100.02 (2)°;Z=4. The crystal structures of these four compounds were determined (respectively refined: 2-hydroxy-benzamide) by single crystal X-ray data. The refinements of the structure parameters by least squares methods yielded in all casesR<0.056. The hydrogen atoms were located by means of difference Fourier summations. The O-H ... O distances are 2.513 (1) Å in 2-hydroxy-benzamide (intramolecular) and 2.625 (1) Å in 2-hydroxy-N,N-dimethyl-benzamide (intermolecular). The two O-H ... S distances in 2-hydroxy-thiobenzamide are 2.904 (2) Å and 2.918 (2) Å (intramolecular, two molecules in the asymmetric unit) and 3.228 (2) Å in 2-hydroxy-N,N-dimethyl-thiobenzamide (intermolecular). Clear N-H ... O hydrogen bonds with 2.926 (1) Å and 3.006 (1) Å occur only in the structure of 2-hydroxy-benzamide (intermolecular).

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Die Kristallstrukturen und Wasserstoffbrücken-Bindungsschemata in vier Benzamid-Derivaten

Zusammenfassung 2-Hydroxy-benzamid, C₇H₇NO₂; monoklin; I2/a-C _2h ⁶ ;a=12.901 (2),b=4.982 (1),c=20.987 (3) Å; =91.50 (2)°;Z=8. 2-Hydroxy-thiobenzamid, C₇H₇NOS; monoklin; P2₁/n-C _2h ⁵ ;a=13.508 (5),b=6.780 (2),c=15.878 (6) Å; =93.74 (5)°;Z=8. 2-Hydroxy-N,N-dimethyl-benzamid, C₉H₁₁NO₂; orthorhombisch; Pbca-D _2h ¹⁵ ;a=11.752 (2),b=16.680 (3),c=9.079 (2) Å;Z=8. 2-Hydroxy-N,N-dimethyl-thiobenzamid, C₉H₁₁NOS; monoklin; P2₁/c-C _2h ⁵ ;a=6.983 (1),b=11.652 (3),c=11.704 (3) Å; =100.02 (2)°;Z=4. Die Kristallstrukturen dieser vier Verbindungen wurden mittels Röntgen-Einkristalldaten bestimmt (bzw. verfeinert: 2-Hydroxy-benzamid). Die Verfeinerungen der Strukturparameter nach der Methode der kleinsten Quadrate ergab in allen FällenR<0.056. Die Wasserstoffatome konnten anhand von Differenz-Fourier-Summationen belegt werden. Die O-H ... O-Abstände haben folgende Werte: 2.513(1)Å in 2-Hydroxy-benzamid (intramolekular) und 2.625(1) Å in 2-Hydroxy-N,N-dimethyl-benzamid (intermolekular). Die zwei O-H ... S-Abstände sind in 2-Hydroxy-thiobenzamid 2.904(2)Å und 2.918(2)Å (intramolekular, zwei moleküle in der asymmetrischen Einheit) und 3.228(2)Å in 2-Hydroxy-N,N-dimethyl-thiobenzamid(intermollekular). Klar zuzuordnende N-H ... O-Wasserstoffbrücken mit 2.926(1)Å und 3.006(1)Å treten lediglich in der Struktur des 2-Hydroxy-benzamid auf (intermolekular).

     

Magnesium and cadmium containing Heusler phases REPd2Mg,REPd2Cd,REAg2Mg,REAu2Mg and REAu2Cd

Twenty-eight new Heusler phases REPd₂Mg, REPd₂Cd, REAg₂Mg, REAu₂Mg and REAu₂Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd₂Cd, GdPd₂Cd, GdAu₂Cd, Y_1.12Ag₂Mg_0.88 and GdAg₂Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu₂Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10⁻⁵ emu mol⁻¹ at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg₂Mg shows the highest ordering temperature of T_C = 98.3 K. ¹¹³Cd and ⁸⁹Y MAS NMR spectra of YAu₂Cd and YPd₂Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.     

Photoacoustic spectra of naphthalenes: 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes

The photoacoustic spectra of 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes have been recorded in the powder form. A method of analysing these spectra is suggested in the light of solution phase and vapour phase data on these molecules. It is observed that the non-radiative transitions in the region of 200 nm decrease in these molecules as the substituent in the 2-position is changed from F to Cl to Br to OH.     

TRIPLET STATE OF METALLOPORPHYCENES: ZnPCl, PdPC2, PtPC2, and NiPC2

We report on a study of the photoexcited triplet state, at low temperatures in ordered liquid crystals, and at room temperatures in the liquid phase, of some new metalloporphycenes: normal zincporphycene, ZnPCl; Pd(II), and Ni(II) complexes of 2,7,12,17-tetra- n -propylporphycene, PdPC2, PtPC2, and NiPC2, respectively. The triplet state at low temperature is obtained by selective laser excitation and its magnetization response is detected by EPR in the 250 ns time scale. From triplet EPR line shapes and triplet spin polarization directions it is concluded that the zinc cation lies above the molecular plane and the palladium cation fits into the porphycene's cavity. Such a proposed structure implies a strong spin-orbit interaction in PdPC2, thus resulting in an out-of-plane active spin state (z-axis), whereas that in ZnPCl, having a smaller spin-orbit interaction, in-plane ( x,y -axes) are the active spin states. Laser photolysis of the metalloporphycenes gives rise to detectable triplets of ZnPCl, PdPC2 and PtPC2 with triplet lifetimes of 26, 5 and 0.2 µs, respectively. The sensitization experiment, using β-acetonaphthone as a sensitizer to produce the triplet, results in detectable transients of only ZnPCl and PdPC2 with much longer triplet lifetimes of 85 and 20 µs, respectively. The short triplet lifetime of PtPC2 (and probably that of NiPC2) do not allow for triplet detection with the present sensitizer. However, the latter two metalloporphycenes quench the triplet lifetime of β-acetonaphthone from 29 to 10µs.     

M2(hpp)4Cl2 and M2(hpp)4, where M = Mo and W: preparations, structure and bonding, and comparisons with C2, C2H2, and C2Cl2 and the hypothetical molecules M2(hpp)4(H)2

The reaction between M(2)Cl(2)(NMe(2))(4), where M = Mo or W, and Hhpp (8 equiv) in a solid-state melt reaction at 150 degrees C yields the compounds M(2)(hpp)(4)Cl(2) 1a (M = Mo) and 1b (M = W), respectively, by the elimination of HNMe(2) [hpp is the anion derived from deprotonation of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp]. Purification of 1a and 1b is achieved by sublimation of the excess Hhpp and subsequent recrystallization from either CH(2)Cl(2) or CHCl(3) (or CDCl(3)). By single-crystal X-ray crystallography, the structures of 1a and 1b are shown to contain a central paddlewheel-like M(2)(hpp)(4) core with Mo-Mo = 2.1708(8) A (from CH(2)Cl(2)), 2.1574(5) A (from CDCl(3)), W-W = 2.2328(2) A (from CDCl(3)), and M-N = 2.09(1) (av) A. The Cl ligands are axially ligated (linear Cl-M-M-Cl) with abnormally long M-Cl bond distances that, in turn, depend on the presence or absence of hydrogen bonding to chloroform. The quadruply bonded compounds M(2)(hpp)(4), 2a (M = Mo), and 2b (M = W), can be prepared from the reactions between 1,2-M(2)R(2)(NMe(2))(4) compounds, where R = (i)()Bu or p-tolyl, and Hhpp (4 equiv) in benzene by ligand replacement and reductive elimination. The compounds 2a and 2b are readily oxidized, and in chloroform they react to form 1a and 1b, respectively. The electronic structure and bonding in the compounds 1a, 1b, 2a, and 2b have been investigated using gradient corrected density functional theory employing Gaussian 98. The bonding in the M-M quadruply bonded compounds, 2a and 2b, reveals M-M delta(2) HOMOs and extensive mixing of M-M pi and nitrogen ligand lone-pair orbitals in a manner qualitatively similar to that of the M(2)(formamidinates)(4). The calculations indicate that in the chloride compounds, 1a and 1b, the HOMO is strongly M-Cl sigma antibonding and weakly M-M sigma bonding in character. Formally there is a M-M triple bond of configuration pi(4)sigma(2), and the LUMO is the M-M delta orbital. An interesting mixing of M-M and M-Cl pi interactions occurs, and an enlightening analogy emerges between these d(4)-d(4) and d(3)-d(3) dinuclear compounds and the bonding in C(2), C(2)H(2), and C(2)Cl(2), which is interrogated herein by simple theoretical calculations together with the potential bonding in axially ligated compounds where strongly covalent M-X bonds are present. The latter were represented by the model compounds M(2)(hpp)(4)(H)(2). On the basis of calculations, we estimate the reactions M(2)(hpp)(4) + X(2) to give M(2)(hpp)(4)X(2) to be enthalpically favorable for X = Cl but not for X = H. These results are discussed in terms of the recent work of Cotton and Murillo and our attempts to prepare parallel-linked oligomers of the type [[bridge]-[M(2)]-](n)().     

Structural,electronic and elastic properties of the Laves phases WFe2, MoFe2, WCr2 and MoCr2 from first-principles

A theoretical analysis of the phase stability, electronic and mechanical properties, and Debye temperatures of the C14-type Laves phases (WFe₂, MoFe₂, WCr₂ and MoCr₂) has been presented from density functional theory. The phase stability follows the order: WFe₂>MoFe₂>WCr₂>MoCr₂. An exchange of electrons takes place between Fe and W/Mo atoms, and there is also electron transfer between Cr and W/Mo. The W–W and Mo–Mo bonds are of the valence character, while the Fe–W/Mo and Cr–W/Mo bonds are of ionic character. The bonding force of A–A is greater than that of A–B in C-14 AB₂ type Laves phases (WFe₂, MoFe₂, WCr₂ and MoCr₂). The ductility of MoCr₂ is higher than others. The hardness of WFe₂ (14.1 GPa) is the highest, and the hardness of MoCr₂ is the lowest. The incompressibility for these laves phases along c-axis is larger than that along a-axis. The Debye temperature (θ_D) of MoFe₂ is 619 K, which is the highest in those phases. These laves phases also have high melting points, which follows the order: WFe₂>MoFe₂>WCr₂>MoCr₂.     

Bis(2, 2, 2-trichloroethoxy)cobalt(II) and chloro(2, 2, 2-trichloroethoxy) cobalt(II): synthesis and coordination chemistry

Summary Bis(2, 2, 2-trichloroethoxy) cobalt(II) and chloro(2, 2, 2-trichloroethoxy)cobalt(II) [Co(OCH₂CCl₃)₂·L] and [CoCl(OCH₂CCl₃)·L], derivatives (L=tetrahydrofuran, dioxan, triphenylarsine oxide, or pyridine) have been synthesised and characterized. They have tetrahedral geometry both in solution and in the solid state.     

Syntheses,Structures, and Properties of New Quaternary Gold-Chalcogenides: K2Au2Ge2S6, K2Au2Sn2Se6, and Cs2Au2SnS4

The new compounds K₂Au₂Ge₂S₆ ( 1 ), K₂Au₂Sn₂Se₆ ( 2 ), and Cs₂Au₂SnS₄ ( 3 ) have been synthesized through direct reaction of the elements with a molten polyalkalithiogermanate(stannate) flux at 650, 550, and 400 °C, respectively. Their crystal structures have been determined by single crystal X-ray diffraction techniques. 1 crystallizes in the monoclinic space group P2₁/n with a = 10.633(2) Å, b = 11.127(2) Å, c = 11.303(2) Å, β = 115,37(3)°, V = 1208,2(3) ų and Z = 4, final R(Rw) = 0.045(0.106). 2 crystallizes in the tetragonal space group P4/mcc with a = 8.251(1) Å, c = 19.961(4) Å, V = 1358,9(4) ų and Z = 4, final R(Rw) = 0.040(0.076). 3 crystallizes in the orthorhombic space group Fddd with a = 6.143(1) Å, b = 14.296(3) Å, c = 24.578(5) Å, V = 2158.4(7) ų and Z = 4, final R(Rw) = 0.039(0.095). The structures of 1 , 2 , and 3 consist of infinite, one-dimensional anionic chains containing X₂Q₆^4– units linked by Au⁺ ions and charge balancing K⁺/Cs⁺ ions situated between the chains. All compounds were investigated with differential thermal analysis, FT-IR, and solid state UV/VIS diffuse reflectance spectroscopy.     

Bond dissociation energies and radical heats of formation in CH3Cl,CH2Cl2, CH3Br,CH2Br2, CH2FCl,and CHFCl2

An analysis of thermochemical and kinetic data on the bromination of the halomethanes CH_4–nX_n (X = F, Cl, Br; n = 1–3), the two chlorofluoromethanes, CH₂FCl and CHFCl₂, and CH₄, shows that the recently reported heats of formation of the radicals CH₂Cl, CHCl₂, CHBr₂, and CFCl₂, and the C? H bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH₄ and the other halomethanes, the following revised ΔH°_f,298 (R) values have been derived: ΔH°_f(CH₂Cl) = 29.1 ± 1.0, ΔH°_f(CHCl₂) = 23.5 ± 1.2, ΔH_f(CH₂Br) = 40.4 ± 1.0, ΔH°_f(CHBr₂) = 45.0 ± 2.2, and ΔH°_f(CFCl₂) = ?21.3 ± 2.4 kcal mol^?1. The previously unavailable radical heat of formation, ΔH°_f(CHFCl) = ?14.5 ± 2.4 kcal mol^?1 has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate C? H and C? X bond dissociation energies in CH₃Cl, CH₂Cl₂, CH₃Br, CH₂Br₂, CH₂FCl, and CHFCl₂.