Bonding studies of compounds of boron and the group 4 elements. Part 9.—Photoelectron spectra and bonding studies of halogeno-, dimethylamino-, and methyl-boranes, BX3and BX2Y

Abstract

The photoelectron (PE) spectra, excited by helium 21.22 eV radiation, of the compounds BX3 and BX2Y (X and Y chosen from F, Cl, Br, I, NMe2, or Me) have been measured. From these and published data, the spectra of the boron trihalides have been fully assigned; earlier proposals have been re-assessed on the basis of (i) line shapes, (ii) calculations of spin-orbit coupling and of orbital energies as a function of distortion, and (iii) comparisons with other BX′3(e.g., X′= NMe2, NHMe) spectra. Assignments for the other BX3 and BX2Y molecules are based on (i) line shapes, and (ii) a comprehensive analysis of trends within series, e.g., for Me2NBCl2, (Me2N)nBCl3–n as well as Me2NBX2(X = F, Cl, Br, I); calculations for these more complex molecules did not prove especially helpful, except for those relating to orbital energies as a function of twist angle (for X = NMe2).