However, this explanation is inconsistent with the observation that the single transition found in the spectrum of trans-l, 2-vinylenebis (di-n-butylphosphine) monoxide (2), in which one of the lone pairs of electrons has now been coordinated, is at an even lower energy than the transition observed for 1. On the other hand (assuming the same transition mechanism obtains for both 1 and its monoxide) the electron-transfer mechanism would account for ...
