The first definitive experimental characterization of the unusual HBBH molecule is reported. It has been generated by several different methods and trapped in neon and argon matrices for a detailed electron spin resonance (ESR) investigation. A complete resolution of the IlB and 'H nuclear hyperfine structure into isotropic and dipolar components was possible. Ab initio CI calculations, conducted as part of this experimental study, yielded Aiso and Adip parameters in good agreement with the observed values. These ESR results offer the first confirmation that HBBH has a 3Xgelectronic ground state as predicted by earlier theoretical calculations. The HBBH molecule resembles acetylene with one electron removed from each of the x-type molecular orbitals. Molecules that contain boron-boron double bonds are extremely rare.

leads to more rapid metalation reactions with porphyrins having negatively charged substituent groups, with the largest rate enhancements found for the most highly charged substrate. Thus, Uro-I has kZn = 75 M"1 s"1 at / = 1.

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The BH2 and CH−2 radicals have been generated and trapped in rare gas matrices for ESR (electron spin resonance) investigation. Theoretical calculations were conducted on these radicals and the CH+2 cation for detailed comparison with the experimental results. The observed magnetic parameters (MHz) for 13 CH−2 in neon matrices at 4 K were: giso =2.0027(3); 13 C; ‖Aiso‖=59(1) and H; ‖Aiso‖=45(1). For 11 BH2 in argon at 4 K the results were: giso =2.0016(3); 11 B; Aiso=358(2) and H; ‖Aiso‖=38(1). The electronic structure information obtained for these small radicals from theoretical and experimental results is discussed and compared with other related molecules.