Boron-Mediated C–C and CN Bond Cleavage of Acetonitrile: Matrix Infrared Spectra and Theoretical Calculations

The reactions of laser-ablated B atoms with acetonitrile
in 4 K
solid neon have been investigated by matrix-isolation infrared spectra,
and new products have been identified by 10B, D, and 13C isotopic substitutions and quantum chemical calculations.
The side-on complex B-η2-(NC)-CH3 was
observed during deposition and isomerized to NCBCH3, CNBCH3, and CNB(H)CH2, respectively, through
C–C bond breakage and hydrogen transfer. For diboron reaction
with acetonitrile, the N-end-on complex BBNCCH3 was formed
on deposition, which rearranged to HBNC(B)CH2 and
HBNBCCH2 by λ > 220 nm irradiation. In
this
reaction pathway, the CN triple bond was completely cleaved.
The final diboron product HBNBCCH2 was much more
stable than the precursors by 152.0 kcal mol–1 at
the CCSD(T)-Full/cc-pVTZ//B3LYP/aug-cc-pVTZ level of theory.