Dihydrogen Phosphide

The compound LiaP7 was first prepared by the action of butyllithium on diphosphane. The route given below, however, is a much better approach it is based on a nucleophilic cleavage of white phosphorus with lithium dihydrogen phosphide. The latter is readily available by the reaction of butyllithium and phosphine.  

A high yield of Li2P 6 is obtained in the reaction of P4 and LiPHj if the stoichiometric ratio of reactants and the reaction time are significantly modified. The formation of the P ion has also been observed in the reaction of Na3P7 with (Ph4P)Cl (ref. 8) and in the decomposition of U2HP7 and LiH2P7.  

The compound Na3P2i is formed when sodium sand is allowed to react with white phosphorus at a Na P ratio of 1 2 (not 1 7 ).  

The three polyphosphides precipitate in the form of definite solvent adducts. This is also observed for the starting compound LiPH2. On drying, the adducts lose a part of the solvent with concomitant decomposition of the salts. 

Through one of the side arms of a clean, dry, 1-L three-necked round-bottomed flask (FI, Fig. 1) a gas inlet device (D) is inserted consisting of an inlet tube, which is fitted with a three-way stopcock (T-bore) and a septum. 

---

Sodium diformylnitromethanide hydrate, 1073a Sodium dihydrobis(2-methoxyethoxy)aluminate, 2570 Sodium dihydrogen phosphide, 4468... 

H2FeOgP2CjjH3o, Iron(ll), dicarbonyl-cts-dihydrido-rrani-bis(triphenyl phosphite)-, 29 159 H2FejO,SC, Iron, nonacarbonyldi-hydrido-pj-thiotri-, 26 244 H2LiP, Lithium dihydrogen phosphide, (LiH2P), 27 228... 

Alkali Metals. The well-known reaction of PH3 with solutions of alkali metals in liquid NH3 leads to the formation of pure, crystalline dihydrogen phosphides, MPH2, where M = Li, Na [70 to 72], K [70], Rb [70, 73], and Cs [70]. An excess of PH3 is recommended to obtain phosphides which are free of alkali amides [70]. Sodium in diethyl ether/anthracene mixtures or potassium in THF/naphthalene mixtures also give high yields of the corresponding dihydrogen phosphides [74]. Additional details concerning the syntheses of solutions of PHg and the isolation of solid phosphides under various experimental conditions are described in Section 1.2.4.1, p. 102. Earlier reactions of PH3 with Na are described in Natrium Erg.-Bd. 4, 1967, pp. 1541/2. 

---