REACTIONS OF LASER-ABLATED BORON ATOMS WITH ETHYLENE AND ETHANE - INFRARED-SPECTRA AND DFT CALCULATIONS FOR SEVERAL NOVEL BC2HX (X = 1, 2, 3, 4, 5) MOLECULES

Laser-ablated boron atoms have been reacted with ethylene during conde nsation in excess argon. The BC2H3 closed-shell isomers borirene (CH)( 2)BH, ethynylborane H2BCCH, and borallene HBCCH2 have been identified from infrared spectra by using B-10, C-13, and D substitution and BP86 /6-311G isotopic frequency calculations. The observation of both cycl ic aromatic and aliphatic products suggests that the reaction proceeds through both exothermic C=C addition and C-H insertion reaction mecha nisms. Evidence is presented for the most stable BC2H4 radicals, namel y, cyclic BHCHCH2 and aliphatic H2BCCH2, which require H-atom migratio n within the intermediates first formed. Ethane gave a smaller yield o f the same products, including linear HBCC and BCCH, vinylborane H2BC2 H3, and an enhanced yield of the C-C insertion product CH3B=CH2.