The syntheses and crystal structures of two new dimethyl diselenide-iodine adducts are described as well as the synthesis and crystal structure of the first diorgano disulfidenitrosonium adduct. The reaction of the NO + cation with R 2 S 2

Molecular dynamics simulations of the solid-state topochemical polymerization of four-membered S2N2 rings to (SN)x have been presented by involving DFT methods and periodic functions. Isotropic pressure compression and a slightly elevated temperature have been applied to lower the activation barriers and to increase the rate of the reaction to be within the framework of MD simulations. The polymer formation is initiated by the cleavage of one bond in one S2N2 ring with a virtually instantaneous attack of the fragment thus formed on the neighboring ring. The energetically most-favored reaction then quickly propagates along a axis throughout the lattice. The structures of the polymer chains are in good agreement with that observed experimentally in the crystal structure determination, but there is less long-range order between the neighboring chains. Upon polymerization the packing of the molecules changes from the herringbone structure of the S2N2 lattice to a layered structure in the (SN)x lattice. While not the same, the simulated and experimental packing changes bear a qualitative similarity. The simulated polymerization was also observed to propagate along c axis in addition to a axis, but these side effects generally disappear toward the end of the simulations. In some cases, the polymers propagating simultaneously in both a and c axis directions persist at the end of the simulation resulting in a complicated network of sulfur-nitrogen chains. This finds experimental support in the observation of several polymorphs (SN)x with severe disorder in the lattice.

The complexes [M(2){mu-N,N'-Se(NR)(2)}(2)](CF(3)SO(3))(2) (1, M = Ag, R = (t)Bu; 2, M = Ag, R = Ad; 3, M = Cu, R = (t)Bu; 4, M = Cu, R = Ad; Ad = 1-adamantyl) were prepared in good yields from the reaction of the corresponding selenium diimide with silver or copper triflate in toluene and were characterized in solution using multinuclear NMR spectroscopy. Recrystallization of 1-4 from a variety of solvents produced 1.2CH(2)Cl(2), 2(AdNH(3))(CF(3)SO(3)) (a few crystals), 3.2thf, and 4.1/2C(7)H(8), which were characterized by X-ray crystallography. All of these salts contain a metallacyclic [M(2){mu-N,N'-Se(NR)(2)}(2)](2+) [M = Ag, Cu; R = (t)Bu, Ad] cation, the frameworks of which exhibit M...M close contacts of 2.7384(9), 2.751(2), 2.556(2)-2.569(2), and 2.531(1) A, respectively. The M...M interaction was further explored by PBE/def-TZVP calculations of the dications [M(2){mu-N,N'-Se(NR)(2)}(2)](2+) (M = Ag, Cu; R = H, Me, (t)Bu, Ad). The geometry optimizations yielded metric parameters that were in good agreement with experimental values, where available. For both metals, it was observed that the M...M distance became shorter, as the organic substituent on nitrogen became bulkier. At the same time, the metallacyclic framework deviated more significantly from planarity. A survey of related dinuclear silver(I) and copper(I) complexes showed that, while there is some correlation between the bite size and the M...M distance, the latter is more dependent on the deviation from planarity of the D(2)M...MD(2) fragment. Atoms in molecules calculations clearly showed the presence of a bond critical point between the two silver or copper centers, as well as two ring critical points. Our computational results are consistent with other recent molecular orbital studies at different levels of theory and indicate the existence of d(10)-d(10) closed-shell metallophilic interactions in 1-4.

While hydrogen bridging is very common in boron chemistry, halogen bridging is rather rare. The simplest halogen-bridged boron compounds are the [B2X7](-) anions (X = F, Cl, Br, I), of which only [B2F7](-) has been reported to exist experimentally. In this paper a detailed theoretical and synthetic study on the [B2X7](-) anions is presented. The structures of [B2X7](-) anions have been calculated at the MP2/def2-TZVPP level of theory, and their local minima have been shown to be of C2 symmetry in all cases. The bonding situation varies significantly between the different anions. While in [B2F7](-) the bonding is mainly governed by electrostatics, the charge is almost equally distributed over all atoms in [B2I7](-) and additional weak iodine···iodine interactions are observed. This was shown by an atoms in molecules (AIM) analysis. The thermodynamic stability of the [B2X7](-) anions was estimated in all phases (gas, solution, and solid state) based on quantum-chemical calculations and estimations of the lattice enthalpies using a volume-based approach. In the gas phase the formation of [B2X7](-) anions from [BX4](-) and BX3 is favored in accord with the high Lewis acidity of the BX3 molecules. In solution and in the solid state only [B2F7](-) is stable against dissociation. The other three anions are borderline cases, which might be detectable under favorable conditions. However, experimental attempts to identify [B2X7](-) (X = Cl, Br, I) anions in solution by (11)B NMR spectroscopy and to prepare stable [PNP][B2X7] salts failed.