Heterocyclic compounds M1M2E1E2H8 (M1, M2 = Al,Ga, In; E1, E2 = N,P, As): A quantum chemical study

Structural and thermodynamic characteristics of heteroelement inorganic heterocycles M¹M²E¹E²H₈ (M¹, M² = Al, Ga, In; E¹, E² = N, P, As) were calculated by the density functional theory B3LYP/LANL2DZ(d,p) method. It was shown that energetic characteristics of heterocycle dissociation processes can be calculated by simple a additive scheme with the use of the average M-E bond energy. Dissociation of heteroelement heterocycles into monomeric H₂MEH₂ molecules proceeds according to the hardsoft acid-base (HSAB) concept.     

An NHC-Stabilized H2GeBH2 Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains

The synthesis, characterization and reactivity studies of the NHC-stabilized complex IDipp ⋅ GeH₂BH₂OTf ( 1 ) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported. Nucleophilic substitution of the triflate (OTf) group in 1 by phosphine or arsine donors provides access to the cationic group 13/14/15 chains [IDipp ⋅ GeH₂BH₂ERR¹R²]⁺ ( 2 E=P; R, R¹=H; R²=^tBu; 3 E=P; R=H; R¹, R²=Ph; 4 a E=P; R, R¹, R²=Ph; 4 b E=As; R, R¹, R²=Ph). These novel cationic chains were characterized by X-ray crystallography, NMR spectroscopy and mass spectrometry. Moreover, the formation of the parent complexes [IDipp ⋅ GeH₂BH₂PH₃][OTf] ( 5 ) and [IDipp ⋅ GeH₃][OTf] ( 6 ) were achieved by reaction of 1 with PH₃. Accompanying DFT computations give insight into the stability of the formed chains with respect to their decomposition.     

Quantum-Chemical Study of Silicon Halide Adducts with Nitrogen-containing Donors: III. Energy Effects of Ammonolysis and Complex-Formation Reactions in Silicon Tetrahalide-Ammonia Systems

Thermodynamic characteristics of hydrogen halide elimination from SiX4-NH3 systems were calculated by the B3LYP density functional method. The role of adducts and oligomeric forms of compounds containing Si-N bonds, as intermediates in the chemical vapor deposition of silicon nitride, was considered. It was shown experimentally that the reaction between silicon tetrachloride and ammonia in nonaqueous solvents involves ammonolysis.     

THERMODYNAMIC STUDY OF GASEOUS MANGANESE PHOSPHATES MnPO3 and MnPO2

In the present work, the stability of gaseous manganese-containing salts was proved by the high-temperature mass spectrometric method. New previously unreported species were found, MnPO₃ and MnPO₂. On the basis of equilibrium constants measured for gas-phase reactions the standard formation enthalpies for MnPO₃ and MnPO₂ were determined as ?602.0 ± 10.0 kJ/mole and ?299.0 ± 11.5 kJ/mole, respectively, and the standard atomization enthalpies as 1950 ± 14 kJ/mole and 1397 ± 14 kJ/mole, respectively.     

Experimental and theoretical study on the reactivity of phosphorus-containing cubane type clusters [RMPR’]<Subscript>4</Subscript> (M = Ga,In) toward pyridine

Reactions of cubane type clusters [EtGaPSi(Me)₂Thex]₄ [Thex = CMe₂(Pr-i)] and {EtInP[Si(i-Bu)₃]}₄ with pyridine were studied. The temperature dependences of vapor pressure over individual solid compounds were measured using a membrane pressure gauge. At a temperature above 200°C the examined clusters undergo irreversible thermal decomposition due to instability of organic substituents. According to the experimental data, the cubane clusters do not react with gaseous pyridine below their decomposition temperature. Thermodynamic parameters for the isomerization of model clusters [HMPH]₄ (M = Ga, In) and their gas-phase reactions with pyridine were calculated by quantum-chemical methods. The addition of pyridine is thermodynamically allowed only at low temperatures.     

Structural and thermodynamic properties of group 13 imidometallanes and their heavier analogues

Systematic theoretical studies of the [XMYH](n) inorganic rings and clusters (M = Al, Ga, In; Y = N, P, As; X = H, F, Cl, Br, I; n = 1-6) have been carried out using hybrid Hartree-Fock density functional theory. A consistent set of the structural and thermodynamic properties has been obtained. The stability of the MY bond decreases in the order Al > Ga >or= In; N > P > As. Terminal groups X have a minor influence on the subsequent elimination enthalpies of the clusters. In the case of X = H, hydrogen elimination makes formation of the [HMYH](6) oligomers from MH(3) and YH(3) thermodynamically favorable; while in the case of halide substituents, formation of [XMYH](6) is thermodynamically unfavorable, except for the system with the strongest MY bond (AlN). Substitution of the acidic hydrogen by X is favorable energetically for all [HMYH](6) clusters, but is complicated by the processes of cluster destruction to form the [X(2)MYH(2)](2) dimers. The high stability of the [HMNH](6) clusters makes them attractive single-source precursors for the production of 13-15 composites.