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 degrees C and +18 degrees C and the value d(4)(20) = 1.014 +/- 0.002 extrapolated. The refractive index of P2H4 was determined to be n(20) = 1.66 +/- 0.01. The surface tension at O degrees C and -50 degrees C was measured to be sigma = 34 and 42 dyn . cm(-1), respectively. In the UV absorption spectrum, gaseous P2H4 exhibits a broad absorption band at lambda(max) = 2220 Angstrom, in n-hexane solution, this band is shifted somewhat to shorter wave-lengths. The molar extinction coefficient was determined to be epsilon approximate to 9001 . 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 degrees C, the solubility of diphosphane(d) in water was found to be 0.035 +/- 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 intermolecular 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 methylene-bis(phosphane).