Beiträge zur Chemie des Phosphors. 140. Dilithium-hydrogenheptaphosphid,Li2HP7 – ein teilmetalliertes Derivat von P7H3: Darstellung und strukturelle Charakterisierung

Contributions to the Chemistry of Phosphorus. 140. Dilithium Hydrogen Heptaphosphide, Li₂HP₇ — a Partially Metallated Derivative of P₇H₃: Preparation and Structural. Characterization Dilithium hydrogen heptaphosphide, Li₂HP₇ ( 2 ), is purely obtained as an orange-red solvent adduct by reacting P₂H₄ with n-BuLi or Li₃P₇ ( 1 ) under suitable conditions. 2 is also formed in the metalation of LiH₂P₇ ( 3 ) or P₇H₃, in the disproportionation of LiH₄P₅, in thepartial protolysis of 1 , and in the nucleophilic cleavage of P₄. The composition and the structure of 2 could be elucidated by a complete analysis of its low-temperature ³¹P{¹H}-NMR spectrum. As shown by the δ(³¹P) values, the P₇ cage in 2 is clearly distorted compared with 1 . The P₇H^2? ion has fluctuating bonds in analogy to dihydrobullvalene and can be described by two valence-tautomeric forms with identical structures. At room temperature 2 disproportionates yielding lithium polyphosphides with a greater number of phosphorus atoms.