PULSED-LASER EVAPORATED BORON ATOM REACTIONS WITH METHANE .2. INFRARED-SPECTRA OF H2CBH2, H2CBH, HCBH, AND HBCBH IN SOLID ARGON

Codeposition of pulsed laser evaporated boron atoms with a mixture of methane/argon onto a 12 K cold window produced several new organoborane species. Substitution of the isotopic reagents B-11, B-10, CH4, (CH4)-C-13, CD4, and CH2D2 has characterized H2CBH2, H2CBH, HCBH, and HBCBH as the major reaction products. These identifications are supported by ab initio quantum chemical frequency calculations. The anticipated primary insertion product CH3BH radical was tentatively identified by its strongest calculated infrared band, a B-H stretching mode at 2561 cm-1. The rearrangement product H2CBH2 was characterized by four infrared bands. The H elimination product H2CBH was identified from a B-H stretching mode at 2724.6 cm-1, a C=B stretching mode at 1469.7 cm-1, and BH and CH2 deformation modes at 902.6, 705.7, and 61 1.8 cm-1, and the H-2 elimination product HCBH radical exhibited diagnostic fundamentals at 3248.8, 2743.4, and 1475.3 cm-1. The secondary reaction product HB=C=BH, with two equivalent boron atoms and carbon-boron double bonds, was identified from a natural boron isotopic triplet at 1895.2, 1883.9, and 1872.0 cm-1. Atomic boron ig extremely reactive with hydrocarbons.