Beiträge zur Chemie des Phosphors. 236. Über einige physikalische und chemische Eigenschaften von Diphosphan(4)

Contributions to the Chemistry of Phosphorus. 236. On Several Physical and Chemical Properties of Diphosphane(4) The density of diphosphane(4) has been measured between ?78°C and +18°C and the value d₄²⁰ = 1.014 · 0.002 extrapolated. The refractive index of P₂H₄ was determined to be n²⁰ = 1.66 ± 0.01. The surface tension at 0°C and ?50°C was measured to be σ = 34 and 42 dyn · cm^?1, respectively. In the UV absorption spectrum, gaseous P₂H₄ exhibits a broad absorption band at λ_max = 2 220 Å, in n-hexane solution, this band is shifted somewhat to shorter wave-lengths. The molar extinction coefficient was determined to be ? ≈? 900 1 · mol^?1 · cm^?1. As a result of photolytic decomposition, absorptions for PH₃ and more phosphorus-rich hydrides also occur. The solubility behavior of P₂H₄ in various organic solvents and the stabilities of the resultant solutions have been investigated. At 0°C, the solubility of diphosphane(4) in water was found to be ± 035 ± 0.003 g P₂H₄/100 g solution and that of water in diphosphane(4) to be 43.2 ± 1.6 g H₂O/100 g solution. The system diphosphane(4)/methanol also exhibits a miscibility anomaly. The IR spectra of liquid P₂H₄ and of its solutions in various solvents revealed, in accord with the results of nuclear magnetic resonance spectroscopy 7], that diphosphane(4) is practically not associated. Weak interactions through hydrogen bridging bonds occur with pyridine and methanol in which P₂H₄ serves as the proton donor and, in the latter case, also as proton acceptor. For the thermolysis of diphosphane(4), it has been found that the primary step comprises a disproportionation with inter-molecular elimination of PH₃ and formation of triphosphane(5). With further progress of the thermolysis, in dependence on the reaction conditions, mixtures of various phosphanes of differing composition are formed. Photolysis gives rise to phosphane mixtures having similar compositions. With aqueous silver salt and iodine solutions, diphosphane(4) reacts as a reducing agent; with sodium hydroxide solution, it reacts by a slow disproportionation as well as by formation and degradation of the subsequently formed polyphosphides. On reaction with triphenylmethyl, triphenylmethane and a yellow solid of varying composition are formed. The reaction of diazomethane with diphosphane(4) leads to the preferential insertion of the carbene in the P? P bond and formation of methylenebis(phosphane).