A new route for the metallation of trihydroheptaphosphine P7H3 with butyllithium

Abstract

A new route for the metallation of heptaphosphine P 7 H 3 with BuLi, namely, decomposi tion of the nortricyclane P 7 unit to form dilithium hexadecaphosphide Li 2 P 16 , was found.Homopolyphosphorus clusters 1 play an important role for understanding of the mechanism of elemen tal phosphorus transformations into various organo phosphorus derivatives 2 and for solving the problem of diagonal relationship between carbon and phosphorus. 3 In spite of the fact that many alkaline metal poly phosphides have been described, 4 the main method for their synthesis is the reaction of the corresponding metal with elemental phosphorus at high temperature 5,6 or in liquid ammonia. 7,8 To date processes of modifica tion of known polyphosphorus compounds remain virtu ally unstudied, although they provide a possibility of se lective synthesis of homopolyatomic clusters of alkaline metals.Therefore, we paid attention to one of simplest polyphosphines: trihydroheptaphosphine P 7 Н 3 (1), 9 which is a potentially convenient reagent for preparing various alkaline metal polyphosphides. At the same time, chemi cal properties of this compound remain virtually unstud ied so far. It is only known that its metallation with LiPH 2 occurs to form Li 3 P 7 in ~100% yield. 10 We found that the use of butyllithium as the metal lating agent in this reaction makes it possible to accom plish a new route, namely, opening of the nortricyclane structure of the P 7 fragment resulting in the formation of several polyphosphorus products. From this mixture we have isolated dilithium hexadecaphosphide Li 2 P 16 (2)