He I photoelectron spectra of unstable boron isocyanates; electronic and geometric structures in the BClx(NCO)3 –x series

Abstract

He I photoelectron spectra have been recorded for the series of unstable boron isocyanate molecules BCl₂(NCO), BCl(NCO)₂, and B(NCO)₃, obtained in a low-pressure flow system from the reaction of gaseous BCl₃ with solid AgNCO at moderate temperatures. Trends in orbital energies can be tracked through the series BCl₃ to B(NCO)₃, thereby providing information on the relative π-bonding capability of the NCO and Cl moieties. These trends can also be followed by semiempirical modified neglect of diatomic overlap calculations. The optimised structures and photoelectron spectra of these molecules support the tendency toward non-linear BNCO chains with increasing NCO substitution, such that B(NCO)₃ has a C_3h structure.