Experimental Evidence of Phosphine Oxide Generation in Solution and Trapping by Ruthenium Complexes

The elusive and poorly investigated phosphine oxide H3PO was generated by simple electrochem. methods based on two-​step process involving first the electroredn. of white P to PH3 in acidic water​/ethanol mixt. at a Pb electrode, followed by PH3 oxidn. at the Zn anode producing H3PO in about 70​% max. yield. Spontaneous disproportionation of H3PO to PH3 and H3PO2 takes place even at low temp. and hampers the isolation of H3PO as a pure product. The phosphine oxide H3PO was characterized in soln. by NMR and trapped in the coordination sphere of Ru(II) ion by tautomerization to phosphinous acid, H2P(OH)​, to afford stable organometallic cationic complexes.