He(I) resonance photoelectron spectra are presented for the borane complexes of ammonia, mono-, di- and tri-methylamine, carbon monoxide and phosphorus trifluoride. The spectra are assigned by correlation with each other, with the spectra of the free bases, and with calculations. Agreement with calculations is good, and evidence is presented in favour of a simple Lewis donor-acceptor bond in the compounds, with some additional “back donation” in the carbon monoxide and phosphorus trifluoride complexes.