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(Figure Presented) Elastic bonds: The structure of [OsHCl(η 2-H2)(PPh3)3] has been determined by neutron diffraction (see figure). The complex presents an unusual H⋯H contact of 1.48(2) Å and can be regarded either as a highly stretched dihydrogen complex or as a compressed dihydride complex. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

Whereas numerous binary transition-metal azido complexes have been reported,1 no binary Group 6 azides are known. Only a limited number of partially azide-substituted molybdenum and tungsten compounds have been reported. Furthermore, no heptaazido compounds have been described. Herein, we report the synthesis and characterization of the first binary Group 6 azides, Mo(N3)6, W(N3)6, Mo(N3)7-, and W(N3)7-. The last two ions represent the first examples of heptaazides. We also report the crystal structure of W(N3)6 and the controlled nitrogen loss from the heptaazido anions to give nitrido-teraazido anions. The NMo(N3)4- ion is already known but had been obtained by a different method., Prepared in collaboration with Laker Research Institute, University of Southern California, Los Angeles, CA. Sponsored in part by National Science Foundation, Washington, DC.

The crystal structure of the 1:1 adduct ClF5-SbF5 was determined and contains discrete ClF4(+) and SbF6(-) ions. The ClF4(+) cation has a pseudo-trigonal bipyramidal structure with two longer and more ionic axial bonds and two shorter and more covalent equatorial bonds. The third equatorial position is occupied by a sterically active free valence electron pair of chlorine. The coordination about the chlorine atom is completed by two longer fluorine contacts in the equatorial plane, resulting in the formation of infinite zigzag chains of alternating ClF4(+) and cis fluorine bridged SbF6(-) ions. Electronic structure calculations were carried out for the isoelectronic series ClF4(+), BrF4(+), IF4(+) and SF4, SeF4, TeF4 at the B3LYP, MP2 and CCSD(T) levels of theory and used to revise the previous vibrational assignments and force fields. The discrepancies between the vibrational spectra observed for ClF4(+) in ClF4(+)SbF6(-) and those calculated for free ClF4(+) are largely due to the fluorine bridging that compresses the equatorial F-Cl-F bond angle and increases the barrier towards equatorial-axial fluorine exchange by the Berry mechanism. A computationally simple model, involving ClF4(+) and two fluorine bridged HF molecules at a fixed distance as additional equatorial ligands, was used to simulate the bridging in the infinite chain structure and greatly improved the fit between observed and calculated spectra. bridging in the infinite chain structure and greatly improved the fit between observed and calculated spectra., Prepared in collaboration with Loker Hydrocarbon Res. Inst. and Dept. of Chemistry, Univ. of Southern California, Los Angeles, CA.

The crystal structure of the 1:1 adduct, ClF5SbF5, was determined and shown to contain discrete ClF4+ and SbF6- ions., Prepared in collaboration with Dept. of Chemistry, Univ. of Southern California, Los Angeles, CA. Pres. at meeting of American Chemical Society. Held in San Francisco, CA, 26-30 Mar 2000.

Single crystals of the hexamethylguanidinium hexafluorosilicate hexahydrate salt, C(NMe2)32(+)SiF6(2-)(dot) 6H2O, were isolated when a product, obtained by water removal from aqueous C(NMe2)3F in a glass vessel, was recrystallized from CH3OH. The crystal structure of this salt was determined, and the structure of the free hexamethylguanidinium cation was calculated, showing that the propeller-shaped structure of the hexamethylguanidinium cation is not caused by solid state effects but is the true minimum energy structure., Prepared in cooperation with Loker Hydrocarbon Research Institute, University of Southern California, Los Angeles, CA.

The first crystal structures of fluoro-substituted carbocations without heteroatom stabilization and of the As2F11(-) anion are reported. The experimental geometries of the carbenium ions in (CH3)2CF(+)asF6(-), (M-CF3C6H4)(C6H5)CF(+)asF6(-) and (M-CF3C6H4)(C6H5)CF(+)as2F11(-) and their comparison with that of the (0-ClC6H4)(C6H5)CCl(+) cation show that, in accord with previous theoretical calculations, chlorine stabilizes carbenium ions more efficiently than fluorine. The apparent discrepancy between these findings and a previously reached conclusion, based on an analysis of sup 13 C NMR chemical shift difference data, are reconciled by using the direct sup 13 C chemical shifts for judging the donor strength of a ligand. The sup 13 C and sup 19 F NMR spectra of the (M-CF3C6H4)(C6H5)CF(+) cation were recorded and analyzed with the help of RHF/6-31G(d,p) calculations using the GIAO method. In each of the three fluoro-substituted carbocation crystal structures studied, the carbenium centers are further stabilized by forming two fluorine bridges with the anions, resulting in pseudo-trigonal bipyramidal environments around the carbenium centers. The F5As-F-AsF5(-) anion in (M-CF3C6H4)(C6H5)CF(+)as2F11(-) possesses a symmetric fluorine bridge with an As-F-As angle of 156.5(13) deg and staggered AsF4 groups., Prep. in collaboration with Loker Hydrocarbon Res. Inst. and Dept. of Chemistry, Univ. of Southern California, Los Angeles, CA.

Single crystals of the hexamethylguanidinium hexafluorosilicate hexahydrate salt, C(NMe2)32(+)SiF6(2-)(dot) 6H2O, were isolated when a product, obtained by water removal from aqueous C(NMe2)3F in a glass vessel, was recrystallized from CH3OH. The crystal structure of this salt was determined, and the structure of the free hexamethylguanidinium cation was calculated, showing that the propeller-shaped structure of the hexamethylguanidinium cation is not caused by solid state effects but is the true minimum energy structure.

Unsymmetrical 2,3-dimethyl-5-silaspiro(4,4)nona-2,7-diene (I) has been prepared by a dissolving metal reaction between 1,1-dichloro-1- silacyclopent-3-ene (III) and 2,3-dimethyl-1,3-butadiene. Ring opening reactions of I catalyzed by alkyllithium reagents and hexamethylphosphoramide (HMPA) have been explored. High yields of the dimer 2,3,12,13-tetramethyl-5,10- disiladispiro(4,4,4,4)octadeca-2,7,12,16-tetraene (II) are formed in these reactions. Dimerization of 2,3-Dimethyl-5-silaspiro(4,4)nona-2,7-diene, 5,10- disiladispiro(4,4,4,4)octadeca-2,7,12,16-tetraene, Structure by X-ray crystallography, Polymers, Composite materials, Organic chemistry, Oligomers, Appendix VII, Organometallic compounds.

Unsymmetrical 2,3-dimethyl-5-silaspiro)4,4)nona-2,7-diene (I) has been prepared by a dissolving metal reaction between 1,1-dichloro-1- silacyclopent-3-ene (III) and 2,3-dimethyl-1,3-butadiene. Ring opening reactions of I catalyzed by alkyllithium reagents and hexamethylphosphoramide (HMPA) have been explored. Keywords: Dimerization of 2,3-dimethyl-5-silaspiro(4.4)nona-2,7- diene, 5,10-Disiladispiro)4,4,4,4)octadeca-2,7,12,16-tetraene, Structure by x-ray crystallography, Organometallic compounds, Composite materials.

Reaction of photogenerated (ETA5-C5H5)2W2(CO)4 with acetylene at 25 yields a complex of the formula (ETA5-C5H5)2W2(CO)4(C2H2). The crystal structure of the complex shows it to have a tetrahedrane-like W2C2 core. The C-C bond distance of the C2H2 unit is 1.35 Angstrom which is close to that of ethylene, considerably longer than the 1.20 Angstrom for acetylenes. The W-W distance is 2.973 Angstrom which is approx. 0.25 Angstrom shorter than the W-W distance in (ETA5-C5H5)2W2(CO)6 but longer than that expected for (ETA5-C5H5)2W2(CO)4. (Author), Prepared in cooperation with University of Southern California, Los Angeles. Dept. of Chemistry.