Quantum chemical calculations at the DFT level have been carried out for the title compounds. The equilibrium geometries and bond dissociation energies are reported. The nature of the bonding between the metal and the π ligands ethylene and acetylene has been investigated by means of an energy partitioning analysis. The nature of the metal−ligand interactions is not very different from each other in the donor−acceptor complexes (CO)5TM−C2H x (TM = Cr, Mo, W), (CO)4TM−C2H x (TM = Fe, Ru, Os), and TM+−C2H x (TM = Cu, Ag, Au). The metal−C2H x bonds have a slightly more electrostatic than covalent character. The covalent bonding comes mainly from the metal ← ligand σ donation and the metal → ligand π∥ in-plane back-donation. The contributions from the out-of-plane π⊥ and δ orbitals are negligible. The main difference of the bonding interactions in the metallacyclic compounds Cl4TM−C2H x (TM = Cr, Mo, W) is that they are clearly more covalent than electrostatic. The covalent interactions come also mainly from a1(σ) and b2(π∥) interactions. The a2(δ) orbital interactions are negligible but the interactions of the out-of-plane π orbitals in the acetylene complexes Cl4TM−C2H2 contribute ∼11% to the total orbital term.

Electronic structure, thermodynamic stability and ligand properties in LRh(CO)2Cl complexes of a series of N-heterocyclic carbenes (NHCs) were studied at the DFT level. The systems under study are: imidazolin-2-ylidene (1), imidazolidin-2-ylidene (2), cyclic(alkyl)(amino)carbene (CAAC, 3), pyrazolin-3-ylidene (4), pyridin-2-ylidene (5), and pyridin-4-ylidene (6). The main structural feature influencing the properties of these species is the number of nitrogen atoms at the ylidene carbon. A decrease of the number of nitrogen atoms on the one hand leads to an increase in donor ability and ligand-to-metal bond strength, but lowers the stability of the NHC on the other hand. The number of nitrogen atoms can be taken as a key parameter for the classification of carbenes into 2N-NHC, 1N-NHC and r-NHC (r = remote).

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New stable monomeric germanium(II) and tin(II) compounds M(OCH 2 CH 2 NMe 2 ) 2 (M ) Ge (1); M ) Sn (2)), stabilized by two intramolecular coordination MrN bonds and containing no bulky groups on the metal atoms, were synthesized. The molecular and crystal structures of these compounds, and that of the previously synthesized compound (ArO) 2 Sn (3; Ar ) 2,4,6-(Me 2 NCH 2 ) 3 C 6 H 2 ), were determined by X-ray diffraction analysis. The electronic structures of 1 and 2 were studied by the DFT method.

Being not prone to aging and possessing high C4/C1 selectivity, new tricyclononene polymers bearing (AlkO)3Si side groups are prospective materials for hydrocarbon mixture separation.

Thermal decomposition of a novel promising high-performance explosive dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) was studied using a number of thermal analysis techniques (thermogravimetry, differential scanning calorimetry, and accelerating rate calorimetry, ARC). To obtain more comprehensive insight into the kinetics and mechanism of TKX-50 decomposition, a variety of complementary thermoanalytical experiments were performed under various conditions. Non-isothermal and isothermal kinetics were obtained at both atmospheric and low (up to 0.3 Torr) pressures. The gas products of thermolysis were detected in situ using IR spectroscopy, and the structure of solid-state decomposition products was determined by X-ray diffraction and scanning electron microscopy. Diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX) was directly identified to be the most important intermediate of the decomposition process. The important role of bistetrazole diol (BTO) in the mechanism of TKX-50 decomposition was also rationalized by thermolysis experiments with mixtures of TKX-50 and BTO. Several widely used thermoanalytical data processing techniques (Kissinger, isoconversional, formal kinetic approaches, etc.) were independently benchmarked against the ARC data, which are more germane to the real storage and application conditions of energetic materials. Our study revealed that none of the Arrhenius parameters reported before can properly describe the complex two-stage decomposition process of TKX-50. In contrast, we showed the superior performance of the isoconversional methods combined with isothermal measurements, which yielded the most reliable kinetic parameters of TKX-50 thermolysis. In contrast with the existing reports, the thermal stability of TKX-50 was determined in the ARC experiments to be lower than that of hexogen, but close to that of hexanitrohexaazaisowurtzitane (CL-20).

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New stable monomeric germanium(II) derivatives XGeOCH 2 CH 2 NMe 2 (1, X ) Cl; 2, X ) OCOMe) with ligands that are not sterically bulky at the Ge atom and only one intramolecular coordination GerN sp 3 bond have been synthesized. The molecular and crystal structures of these compounds were studied by X-ray diffraction analysis. The electronic structures of 1 and 2 were studied by DFT. Compound 2 is the first structurally characterized acyloxy derivative of germanium(II).