The electronic effects of bulky aryl substituents on low coordinated phosphorus atoms in diphosphenes and phosphaalkenes by functionalization at the para position

The electronic effects of bulky aryl substituents on low coordinated phosphorus atom(s) in diphosphenes and phosphaalkenes have been examined by means of functionalization at the para position of the substituents. Bulky bromobenzenes bearing an electron-donating or electron-withdrawing group at the para position were prepared as precursors of the substituents and some of them were applied to preparations of the corresponding diphosphenes and fluorenylidene-(phenyl)phosphines bearing low-coordinated phosphorus atom(s). Electronic perturbation by the para-substituent in the system was indicated by UV-vis spectra and ³¹PNMR chemical shifts. These observations can be attributed to effects induced by electronic properties of the bulky aryl substituent(s) on the lone pair of the low-coordinated phosphorus atom.