Energetic salts of the binary 5-cyanotetrazolate anion ([C2N5]-) with nitrogen-rich cations.

The reaction of cyanogen (NC-CN) with MN(3) (M=Na, K) in liquid SO(2) leads to the formation of the 5-cyanotetrazolate anion as the monohemihydrate sodium (1·1.5 H(2)O) and potassium (2) salts, respectively. Both 1·1.5 H(2)O and 2 were used as starting materials for the synthesis of a new family of nitrogen-rich salts containing the 5-cyanotetrazolate anion and nitrogen-rich cations, namely ammonium (3), hydrazinium (4), semicarbazidium (5), guanidinium (6), aminoguanidinium (7), diaminoguanidinium (8), and triaminoguanidinium (9). Compounds 1-9 were synthesised in good yields and characterised by using analytical and spectroscopic methods. In addition, the crystal structures of 1·1.5 H(2)O, 2, 3, 5, 6, and 9·H(2)O were determined by using low-temperature single-crystal X-ray diffraction. An insight into the hydrogen bonding in the solid state is described in terms of graph-set analysis. Differential scanning calorimetry and sensitivity tests were used to assess the thermal stability and sensitivity against impact and friction of the materials, respectively. For the assessment of the energetic character of the nitrogen-rich salts 3-9, quantum chemical methods were used to determine the constant volume energies of combustion, and these values were used to calculate the detonation velocity and pressure of the salts using the EXPLO5 computer code. Additionally, the performances of formulations of the new compounds with ammonium nitrate and ammonium dinitramide were also predicted. Lastly, the ICT code was used to determine the gases and heats of explosion released upon decomposition of the 5-cyanotetrazolate salts.

First actinide complexes of the nitrogen-containing ligands dinitramide (N(NO2)2(-)), 4,5-Dicyano-1,2,3-triazolate (C4N5(-)), and dicyanamide (N(CN)2(-)).

The syntheses and characterization of uranyl complexes of nitrogen-containing ligands are reported. For the first time, an actinide complex containing dinitramide ligands coordinated to the actinide center in UO(2)(N(NO(2))(2))(2)(OP(NMe(2))(3))(2) (1) has been isolated and structurally characterized. Using an excess of OP(NMe(2))(3), the dinitramide ligands were replaced by OP(NMe(2))(3) ligands resulting in the formation of the salt [UO(2)(OP(NMe(2))(3))(4)][N(NO(2))(2)](2) (2). Both complexes 1 and 2 were characterized using IR, Raman, as well as (1)H, (13)C, (14)N and (31)P{(1)H} NMR spectroscopy, in addition to C/H/N analysis. The structures of 1 and 2 were determined by single crystal X-ray diffraction. 1: monoclinic, P2(1)/n, a = 12.5389(3), b = 7.9496(2), c = 15.8172(4) A, beta = 110.842(3) degrees , V = 1473.48(6) A(3), Z = 2. 2: orthorhombic, Pbca, a = 14.5640(6), b = 15.3697(6), c = 45.7789(18) A, V = 10247.3(7) A(3), Z = 8. The related complex [UO(2)(N(CN)(2))(2)(OP(NMe(2))(3))(2)] (3) containing the dicyanamide ligand (N(CN)(2)(-)) coordinated to the U(VI) center was synthesized and characterized using IR, Raman, (1)H, (13)C and (31)P{(1)H} NMR spectroscopy. The structure of 3 was determined using single crystal X-ray diffraction and revealed a dinuclear complex containing both terminal and bridging N(CN)(2)(-) ligands. 3: monoclinic, P2(1)/c, a = 15.5873(9), b = 14.2132(6), c = 13.2006(5) A, beta = 100.029(3) degrees, V = 2879.8(2) A(3), Z = 2. Finally, in this investigation of the coordination of relatively nitrogen-rich ligands to uranium centers, the synthesis, characterization, and isolation of the first U(VI) complex showing coordination of the triazolate ligand via a ring nitrogen atom is reported in UO(2)((NC)(2)C(2)N(3))(2)(OPPh(3))(3) (4). Complex 4 was characterized using IR, Raman, (1)H, (13)C and (31)P{(1)H} NMR spectroscopy. The solid state structure of 4 was determined using single crystal X-ray diffraction. 4: monoclinic, P2(1)/n, a = 18.9970(2), b = 31.9500(3), c = 20.1133(2) A, beta = 111.4449(4) degrees, V = 11362.69(19) A(3), Z = 8. To the best of our knowledge, compounds 1 and 2 are the first structurally characterized complexes where a dinitramide ligand is coordinated to an f-block center. Complex 3 is the first structurally characterized actinide dicyanamide complex and a rare example of a dinuclear uranyl complex showing a 12 membered U-N-C ring formed by bridging dicyanamide ligands between two uranyl centers. Finally, complex 4 is the first isolated and structurally characterized uranium complex containing a triazolate ligand coordinated to the U(VI) center. Complexes 3 and 4 are examples of uranyl complexes containing ligands coordinated via nitrogen atoms to the U(VI) center. Whereas the dinitramide ligand can coordinate via N or O atoms, in complex 1, the [N(NO(2))(2)](-) ligand acts as a bidentate chelate ligand, and only coordination via the oxygen atoms to the U(VI) center was observed in the crystalline state.

Does [I3]+ act as an "[I]+" donor to CH3CN and N2O? Structure of [H3CCN-I-NCCH3]+ [AsF6]-.

The solid state structure of the [(CH(3)CN)(2)I](+) cation in [(CH(3)CN)(2)I][AsF(6)] was determined using single crystal X-ray diffraction. The highly reactive cation was prepared by reaction of [I(3)][AsF(6)] with CH(3)CN in liquid SO(2). In the solid state, the CNI backbone consisting of seven atoms is linear and shows a dicoordinate iodine center. The ability of [I(3)][AsF(6)] to act as a source of "[I](+)" to CH(3)CN and N(2)O is compared, and the computed structures of the [CH(3)CNI](+), [(CH(3)CN)(2)I](+), [IN(2)O](+) and [ION(2)](+) cations are discussed.

Nitrate and perchlorate complexes of uranium(IV).

The solid-state structures of the [U(IV)(NO(3))(6)](2-) anions in the [n-Pr(4)N](2)[U(NO(3))(6)] (1), [n-Bu(4)N](2)[U(NO(3))(6)] (2), and [Ph(4)P](2)[U(NO(3))(6)] x 4 NCCH(3) (3) salts were determined using single-crystal X-ray diffraction. For the first time, a nondisordered structure of the hexanitratouranate(IV) dianion with a coordination number of 12 for the central U(IV) atom was determined. Salts 1-3 were prepared in simple metathesis reactions and characterized using IR spectroscopy, C/H/N analysis, and single-crystal X-ray diffraction. Attempts to prepare a salt containing the [U(IV)(ClO(4))(6)](2-) anion using the analogous route resulted in the isolation of U(ClO(4))(4)(NCCH(3))(5) (4), which was characterized using single-crystal X-ray diffraction. Compound 4 is the first structurally characterized uranium(IV) perchlorate to be reported in the literature.

Synthesis and characterization of 4,5-dicyano-2H-1,2,3-triazole and its sodium, ammonium, and guanidinium salts.

In this contribution, the synthesis and structural characterization of the 4,5-dicyano-1,2,3-triazolate anion in its sodium, ammonium, guanidinium, aminoguanidinium, diaminoguanidinium, and triaminoguanidinium salts is reported. The synthesis of 4,5-dicyano-2H-triazole (1) was repeated as described in the literature (Johansson, P. et al. Solid State Ionics 2003, 156, 129) and spectroscopically characterized using (1)H, (13)C, and (15)N NMR, IR, and Raman spectroscopy, as well as differential scanning calorimetry (DSC) and mass spectrometry (DEI+). The molecular structure was determined for the first time using X-ray diffraction (1: monoclinic, P2(1)/c, a = 6.0162(6) A, b = 11.2171(10) A, c = 7.5625(7) A, beta = 94.214(8) degrees, V = 508.97(8) A(3), Z = 4). Compound 1 was deprotonated using Na(2)CO(3) to form the corresponding sodium salt of the 4,5-dicyano-1,2,3-triazolate anion (2) as a monohydrate. This compound was also characterized using (13)C, (14)N, (15)N NMR, IR, and Raman spectroscopy, as well as single crystal X-ray diffraction (2: monoclinic, P2(1)/c, a = 3.6767(6) A, b = 20.469(4) A, c = 9.6223(13) A, beta = 97.355(13) degrees, V = 718.2(2) A(3), Z = 4). Reaction of 2 with AgNO(3) yielded silver 4,5-dicyano-1,2,3-triazolate (3) which was characterized using IR and Raman spectroscopy, as well as DSC, and was used to prepare the ammonium (4), guanidinium (5), aminoguanidinium (6), diaminoguanidinium (7), and triaminoguanidinium (8) salts of the 4,5-dicyano-1,2,3-triazolate anion in a metathetical reaction from the corresponding ammonium and guanidinium halides. All new compounds (4-8) were spectroscopically characterized ((1)H and (13)C NMR, IR, Raman), the stabilities investigated using DSC, the mass spectra obtained using the FAB+ and FAB- methods and the solid state structures determined using single crystal X-ray diffraction: (4): orthorhombic, Pnma, a = 6.5646(13) A, b = 7.5707(16) A, c = 13.303(3) A, V = 661.1(2) A(3), Z = 4; (5): monoclinic, Cc, a = 12.6000(11) A, b = 17.1138(15) A, c = 12.0952(9) A, beta = 106.098(7) degrees, V = 2505.9(4) A(3), Z = 12; (6): monoclinic, Pa, a = 7.0921(9) A, b = 7.2893(9) A, c = 8.8671(11) A, beta = 105.141(11) degrees, V = 442.48(10) A(3), Z = 2; (7): monoclinic, P2(1), a = 3.7727(4) A, b = 15.6832(17) A, c = 8.3416(10) A, beta = 101.797(10) degrees, V = 483.13(9) A(3), Z = 2; (8): monoclinic, C2/c, a = 14.0789(14) A, b = 11.5790(11) A, c = 13.5840(14) A, beta = 115.239(10) degrees, V = 2003.1(3) A(3), Z = 8. The impact and friction sensitivities of compounds 4-8 were investigated using drop hammer and friction apparatus methods, and all compounds were found to be neither impact (> 30 J) nor friction sensitive (> 360 N). The detonation parameters of compounds 5- 8 were computed using the EXPLO5 code.

Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.

The bonding in the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I42+ (three sigma + two pi bonds), the Se-I pi-bonded Se2I42+ (four sigma + one pi bonds), and their higher-energy isomers have been studied using modern DFT and ab initio calculations and theoretical analysis methods: atoms in molecules (AIM), molecular orbital (MO), natural bond orbital (NBO), and valence bond (VB) analyses, giving their relative energies, theoretical bond orders, and atomic charges. The aim of this work was to seek theory-based answers to four main questions: (1) Are the previously proposed simple pi*-pi* bonding models valid for S2I42+ and Se2I42+? (2) What accounts for the difference in the structures of S2I42+ and Se2I42+? (3) Why are the classically bonded isolobal P2I4 and As2I4 structures not adopted? (4) Is the high experimentally observed S-S bond order supported by theoretical bond orders, and how does it relate to high bond orders between other heavier main group elements? The AIM analysis confirmed the high bond orders and established that the weak bonds observed in S2I42+ and Se2I42+ are real and the bonding in these cations is covalent in nature. The full MO analysis confirmed that S2I42+ contains three sigma and two pi bonds, that the positive charge is essentially equally distributed over all atoms, that the bonding between S2 and two I2+ units in S2I42+ is best described by two mutually perpendicular 4c2e pi*-pi* bonds, and that in Se2I42+, two SeI2+ moieties are joined by a 6c2e pi*-pi* bond, both in agreement with previously suggested models. The VB treatment provided a complementary approach to MO analysis and provided insight how the formation of the weak bonds affects the other bonds. The NBO analysis and the calculated AIM charges showed that the minimization of the electrostatic repulsion between EI2+ units (E = S, Se) and the delocalization of the positive charge are the main factors that explain why the nonclassical structures are favored for S2I42+ and Se2I42+. The difference in the structures of S2I42+ and Se2I42+ is related to the high strength of the S-S pi bond compared to the weak S-I sigma bond and the additional stabilization from increased delocalization of positive charge in the structure of S2I42+ compared to the structure of Se2I42+. The investigation of the E2X42+ series (E = S, Se, Te; X = Cl, Br, I) revealed that only S2I42+ adopts the highly np pi-np pi (n > or = 3)-bonded structure, while all other dications favor the pi-bonded Se2I42+ structure. Theoretical bond order calculations for S2I42+ confirm the previously presented experimentally based bond orders for S-S (2.1-2.3) and I-I (1.3-1.5) bonds. The S-S bond is determined to have the highest reported S-S bond order in an isolated compound and has a bond order that is either similar to or slightly less than the Si-Si bond order in the proposed triply bonded [(Me3Si)2CH]2(iPr)SiSi triple bond SiSi(iPr)[CH(SiMe3)2]2 depending on the definition of bond orders used.

Structurally characterized ternary U-O-N compound, UN4O12: UO2(NO3)2.N2O4 or NO(+)UO2(NO3)3-?

The synthesis and characterization of the ternary U-O-N compound NO(+)UO2(NO3)3- (1) using IR and low-temperature and room-temperature Raman spectroscopy as well as 14N and 15N NMR spectroscopy are reported. In addition, solution Raman spectra of compound 1 recorded in various solvents are reported. The structure of compound 1 was determined using single-crystal X-ray diffraction techniques: monoclinic, C2/c, a = 13.3992(4) angstroms, b = 9.9781(4) angstroms, c = 7.6455(2) angstroms, beta = 115.452(2) degrees, V = 922.98(5) angstroms3, Z = 4. Compound 1 is highly moisture-sensitive and must be handled under an inert atmosphere. It reacts with water with the liberation of NO2. For the first time, this important precursor for the synthesis of anhydrous uranyl nitrate could be unambiguously identified and has been shown to be an ionic nitrosonium salt and not an adduct between uranyl nitrate and dinitrogen tetroxide, UO2(NO3)2.N2O4, as is incorrectly and predominantly cited in the literature.

Synthesis, structural and computational investigations of UO2I42-: a structurally characterized U(VI)-I anion.

The synthesis and characterization of (Ph(4)P)(2)UO(2)I(4).2NCCH(3) is reported. The UO(2)I(4)(2-) anion is not only the first unambiguously characterized anion containing a uranium(VI)-iodine bond, but is also the last member of the UO(2)X(4)(2-) (X = Cl, Br, I) series to be unambiguously identified and structurally characterized, in contrast to salts of the UO(2)Cl(4)(2-) and UO(2)Br(4)(2-) anions, which have all been thoroughly investigated and structurally characterized. (Ph(4)P)(2)UO(2)I(4).2NCCH(3) was characterized using IR, Raman, (1)H, (13)C, and (31)P NMR spectroscopy as well as X-ray diffraction. In addition, a computational investigation of the UO(2)I(4)(2-) anion was undertaken and compared with the experimentally observed structure.

First structurally characterized actinide isocyanates.

The synthesis and characterization of the neutral uranylisocyanate UO(2)(NCO)(2)(OP(NMe(2))(3))(2) [crystal data: monoclinic, P2(1)/c, a = 8.512(2) A, b = 10.931(2) A, c = 14.329(3) A, beta = 103.923(3) degrees , V = 1294.0(4) A(3), Z = 2] and isocyanato uranate (Et(4)N)(6)[(UO(2))(2)(NCO)(5)O](2) x 2CH(3)CN x H(2)O [crystal data: monoclinic, P2(1)/c, a = 17.2787(2) A, b = 15.560(1) A, c = 32.7619(4) A, beta = 94.0849(5) degrees , V = 8786.5(2) A(3), Z = 4] are reported. Not only are these compounds the first unambiguously characterized uranium isocyanates regardless of the oxidation state for uranium, but they are also the first structurally characterized actinide isocyanates. Both compounds show coordination of the OCN moiety through nitrogen to uranium and were characterized using IR and (1)H, (13)C, (14)N, and (31)P NMR spectroscopy and X-ray diffraction.

Synthesis and characterization of heavier dioxouranium(VI) dihalides.

The synthesis and characterization of the dioxouranium(VI) dibromide and iodide hydrates, UO(2)Br(2)x3H(2)O (1), [UO(2)Br(2)(OH(2))(2)](2) (2), and UO(2)I(2)x2H(2)Ox4Et(2)O (3), are reported. Moreover, adducts of UO(2)I(2) and UO(2)Br(2) with large, bulky OP(NMe(2))(3) and OPPh(3) ligands such as UO(2)I(2)(OP(NMe(2))(3))(2) (4), UO(2)Br(2)(OP(NMe(2))(3))(2) (5), and UO(2)I(2)(OPPh(3))(2)(6) are discussed. The structures of the following compounds were determined using single-crystal X-ray diffraction techniques: (1) monoclinic, P2(1)/c, a = 9.7376(8) A, b = 6.5471(5) A, c = 12.817(1) A, beta = 94.104(1) degrees , V = 815.0(1) A(3), Z = 4; (2) monoclinic, P2(1)/c, a = 6.0568(7) A, b = 10.5117(9) A, c = 10.362(1) A, beta = 99.62(1) degrees , V = 650.5(1) A(3), Z = 2; (4) tetragonal, P4(1)2(1)2, a = 10.6519(3) A, b = 10.6519(3) A, c = 24.0758(6) A, V = 2731.7(1) A(3), Z = 4; (5) tetragonal, P4(1)2(1)2, a = 10.4645(1) A, b = 10.4645(1) A, c = 23.7805(3) A, V = 2604.10(5) A(3), Z = 4, and (6) monoclinic, P2(1)/c, a = 9.6543(1) A, b = 18.8968(3) A, c = 10.9042(2) A, beta =115.2134(5) degrees , V = 1783.01(5) A(3), Z = 2. Whereas 1 and 2 are the first UO(2)Br(2) hydrates and the last missing members of the UO(2)X(2) hydrate (X = Cl --> I) series to be structurally characterized, 4 and 6 contain room-temperature stable U(VI)-I bonds with 4 being the first structurally characterized room temperature stable U(VI)-I compound which can be conveniently prepared on a gram scale in quantitative yield. The synthesis and characterization of 5 using an analogous halogen exchange reaction to that used for the preparation of 4 is also reported.

The ionic isomegethic rule and additivity relationships: estimation of ion volumes. A route to the energetics and entropics of new, traditional, hypothetical, and counterintuitive ionic materials.

By virtue of our recently established relationships, knowledge of the formula unit volume, V(m), of a solid ionic material permits estimation of thermodynamic properties such as standard entropy, lattice potential energy, and, hence, enthalpy and Gibbs energy changes for reactions. Accordingly, development of an approach to obtain currently unavailable ion volumes can expose compounds containing these ions to thermodynamic scrutiny, such as predictions regarding stability and synthesis. The isomegethic rule, introduced in this paper, states that the formula unit volumes, V(m), of isomeric ionic salts are approximately the same; this rule then forms the basis for a powerful and successful means of predicting unknown ion volumes (as well as providing a means of validating existing volume and density data) and, thereby, providing solid state thermodynamic data. The rule is exploited to generate unknown ion and (by additivity) corresponding formula unit volumes.

CS2N3(-)-containing pseudohalide species: an experimental and theoretical study.

The first structural reports of anhydrous salts containing the CS2N3 moiety are presented. The new M(+)CS2N3- species (M = NH4 (1), (CH3)4N (2), Cs (3), K (4)) were characterized by vibrational spectroscopy (IR, Raman), as well as multinuclear NMR spectroscopy (1H, 13C, 14N NMR). Moreover, the solid-state structures of NH4CS2N3 (1) [orthorhombic, Pbca, a = 10.6787(1) A, b = 6.8762(1) A, c = 15.2174(2) A, V = 1117.40(2) A3, Z = 8] and (H4C)4NCS2N3 (2) [monoclinic, P2(1)/m, a = 5.9011(1) A, b = 7.3565(2) A, c = 10.9474(3) A, beta = 91.428(1) degrees, V = 475.09(2) A3, Z = 2] were determined using X-ray diffraction techniques. The covalent compound CH3CS2N3 (5) was prepared by the reaction of methyl iodide with sodium azidodithiocarbonate and was characterized by vibrational spectroscopy (IR, Raman), multinuclear NMR spectroscopy (1H, 13C, 14N), and X-ray diffraction techniques [monoclinic, P2(1)/m, a = 5.544(1) A, b = 6.4792(7) A, c = 7.629(1) A, beta = 105.53(2) degrees, V = 264.06(7) A3, Z = 2]. Furthermore, the gas-phase structure of 5 was calculated (MPW1PW91/cc-pVTZ) and found to be in very good agreement with the experimentally determined structure. Improved synthetic routes for the recently reported dipseudohalogen (CS2N3)2 and interpseudohalogen CS2N3CN (6) are described, and the calculated gas-phase structure of 6 was compared with the experimentally determined structure (X-ray). The vibrational spectra of 6 and HCS2N3 (7) are also reported. Furthermore, several plausible isomers for 7 were calculated in an attempt to rationalize the experimentally observed structure which has N-H and not S-H connectivity. The lowest energy isomer for 7 is in agreement with the experimentally observed structure, and the Brønsted acidity was calculated at the MPW1PW91/cc-pVTZ level of theory. The unknown CSe2N3- anion (8) was also investigated both theoretically and experimentally, and the structure and vibrational data for the unknown CTe2N3- anion (9) were investigated by quantum-chemical calculations using a quasi-relativistic pseudopotential for Te (ECP46MWB) and a cc-pVTZ basis set for C and N. The gas-phase structure of 9 is predicted to be that of a five-membered ring in analogy to the sulfur and selenium analogues.

Synthesis and structure of UO2I2(OH2)2 x 4Et2O: first structurally characterized U(VI)-I bond and lightest missing member of the UO2X2 (X = halide) series.

UO2I2(OH2)2.4Et2O has been synthesized and structurally characterized using X-ray diffraction. This thermally unstable species is the lightest missing member of the dioxouranium dihalide (UO2X2, X = F, Cl, Br, I)-containing series to be structurally characterized and is, to our knowledge, the first structurally characterized compound containing a U(VI)-I bond.