Crystal structure of 2-azido-1H-imidazole-4,5-di-carbonitrile.

In the title compound, C5HN7, the nitrile and azido substituents are close to being coplanar with the central ring. Mol-ecules in the crystal are linked via an N-H⋯N hydrogen bond to a nitrile acceptor, forming a chain extending along the c-axis direction.

Crystal structure of 4,5-di-nitro-1H-imidazole.

The title compound, C3H2N4O4, forms crystals with two mol-ecules in the asymmetric unit which are conformationally similar. With the exception of the O atoms of the nitro groups, the mol-ecules are essentially planar. In the crystal, adjacent mol-ecules are associated by N-H⋯N hydrogen bonds involving the imidazole N-H donors and N-atom acceptors of the unsaturated nitro-gen of neighboring rings, forming layers parallel to (010).

Crystal structure of 2-diazo-imidazole-4,5-dicarbo-nitrile.

In the title compound, C5N6, all the atoms are approximately coplanar. In the crystal, mol-ecules are packed with short contact distances of 2.885 (2) (between the diazo N atom connected to the ring and a cyano N atom on a neighboring mol-ecule) and 3.012 (2) Š(between the terminal diazo N atom and an N atom of a neighboring imidazole ring).

En route to dinitroacetylene: nitro(trimethylsilyl)acetylene and nitroacetylene harnessed by dicobalt hexacarbonyl.

Dinitroacetylene and other nitroacetylenes are attractive stoichiometric precursors to high energy-density materials, but suffer from high reactivity and thermal instability. Herein, we report that nitroacetylenes can be dramatically stabilized in the form of their dicobalt hexacarbonyl complexes. In particular, we describe the syntheses and characterization of the first two transition-metal complexes of nitroalkynes, [µ-1-nitro-2-(trimethylsilyl)ethyne-1,2-diyl]bis(tricarbonylcobalt)(Co-Co) and [µ-1-nitroethyne-1,2-diyl]bis(tricarbonylcobalt)(Co-Co). The chemistry of these compounds reveals their potential as reaction partners in [2+2+2] cyclotrimerizations, furnishing nitroindane, nitrotetralin, and trinitrobenzene products. The X-ray crystal structure of 1,3,5-trinitro-2,4,6-tris(trimethylsilyl)benzene presents a distorted, yet planar, aromatic ring.

Synthesis and characterization of the homoleptic octahydrotriborate complex Cr(B3H8)2 and its Lewis base adducts.

Solvate-free sodium octahydrotriborate, NaB3H8, is prepared on a 20 gram scale from sodium amalgam and diborane in diethyl ether. This substance, which is chemically related to borohydride-based compounds being investigated as hydrogen storage materials, is also useful for the preparation of transition-metal complexes bearing B3H8 ligands. Treatment of CrCl3 with NaB3H8 affords a thermally unstable purple liquid thought to be a chromium(III) hydride of stoichiometry CrH(B3H8)2. This hydride converts rapidly at room temperature to the chromium(II) complex Cr(B3H8)2, which adopts a square-planar structure in which four hydrogen atoms form the coordination sphere of the chromium atom. This chromium(II) species forms six-coordinate Lewis base adducts Cr(B3H8)2L2, where L is Et2O, THF, or PMe3; the first two of these adopt trans geometries, whereas the latter is cis. Volatile Cr(B3H8)2 is the first homoleptic transition-metal complex of the octahydrotriborate anion, and it is an excellent single-source precursor for the chemical vapor deposition of thin films of CrB2 at temperatures as low as 200 degrees C. Crystal structures of the new complexes are reported.