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The remarkable change in the BN bond lengths of CH3CN · BF3 and HCN · BF3 between the gas phase and the condensed phase has been attributed to effects of the surrounding medium. Results herein suggest that in BF3‐rich argon matrices, CH3CN · BF3 and HCN · BF3 are present in the form with a short BN bond, as is CH3CN · BF3 in solution in benzene. The two structural alternatives for HCN · BF3 are shown schematically above.

The Raman and infrared spectra of gas phase Re(2)O(7) are reported. The experimental vibrational spectra of molecular Tc(2)O(7) and Re(2)O(7) are compared with calculated spectra. The results of these studies agree with a nonlinear M-O-M bridge for Tc(2)O(7) and Re(2)O(7). For infrared intensity calculations, the point charge approximation is used, while for the Raman calculations a combination of bond and atom polarizabilities is adopted. Pure Re(2)O(7) was prepared from rhenium wire, but attempts to prepare it from rhenium powder and oxygen always led to infrared spectra showing serious contamination from a species containing an -OH linkage. Detailed experiments identified this molecule as HReO(4), a unique transition metal analogue of the perhalic acids, and a partial infrared spectrum of this molecule is reported.

This paper reports fundamental vibration frequencies for molecular OS03Fz and o s o 4 isolated in argon matrices at low temperatures. Os03Fz is shown to have D3h symmetry on the basis of Raman and IR selection rules, and this conclusion is confirmed by the results of ' 8 0 enrichment studies which demonstrate the presence of an oso3 unit containing three equivalent oxygens. The argon matrix frequencies are 946.5 ( A ; ) , 928.5 (E'), 646 (A;), 619 ( A ; ) 348 (E"), 316.5 (E') 258 ( A ; ) and 206 (E') cm-l. High resolution spectra are also reported for matrix isolated oS1604 (~1963, vz 332, v3 956, and v4 327 cm-I) and for ' 8 0 enriched oso4 species.

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Polypropylene is formed using a catalyst typically consisting of TiCI, supported on a MgCI, substrate. A Combination of molecular-modelling methods has been used to investigate the catalyst at the atomic level. Molecular graphics and static lattice calculations show that MgCI, exhibits stable surfaces in which surface Mg ions are four, five and six coordinated. Density functional theory calculations show that TiCl, binds to MgCI2 via a 'triply bound' model. This results in one of the CI-Ti-CI bond angles opening up to 1 3 F , an event that clearly facilitates cis insertion of the monomer unit at this position. These calculations also demonstrate the stability of this TiCI,/MgCI2 cluster with a propene monomer unit.

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