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 condensation in excess argon. The BC 2 H 3 closed-shell isomers borirene (CH) 2 BH, ethynylborane H 2 BCCH, and borallene HBCCH 2 have been identified from infrared spectra by using 10 B, 13 C, and D substitution and BP86/6-311G* isotopic frequency calculations. The observation of both cyclic aromatic and aliphatic products suggests that the reaction proceeds through both exothermic C C addition and C−H insertion reaction mechanisms. Evidence is presented for the most stable BC 2 H 4 radicals, namely, and aliphatic H 2 BCCH 2, which require H-atom migration within the intermediates first formed. Ethane gave a smaller yield of the same products, including linear HBCC and BCCH, vinylborane H 2 BC 2 H 3, and an enhanced yield of the C−C insertion product CH 3 B CH 2 .