Reactions with Diborane and Monobromodiborane

Ammonia reacts with boron hydride to form a product with the empirical composition B2H6 2NH3 s2-is4) similarly, phosphine combines with diborane, in the gas phase above -30 °C and in the liquid phase in a sealed tube above -130 C, to give a white instable solid of constitution BH3PH3 (m.p. 32-35 °C) is ). The dissociation pressure of BH3 PH3 is so large that the compound is already separated into its components at room temperature 

Nuclear magnetic resonance spectra show that the compound exists as a monomer in the molten state IR and Raman data show that the same molecular structure exists for the solid state Sawodny and Goubeau calculated the force constants from the normal vibrations of the molecule, after they had corrected the original assignments of the bands A bond number of 0.78 was found for the P—B bond. The chemical shifts and coupling constants from the H and B n.m.r. spectra for molten BH3PH3 are given in Table 9 

Trimethylamine replaces PH3 quantitatively in BH3 PH3 to give BH3 N(CH3)3. Liquid or gaseous ammonia also replaces phosphine in the compound BH3 PH3 to the extent of 52-58% or up to 75%, respectively. The hydrogen atoms bonded to boron are partially, or completely, replaced by chlorine on treatment with hydrogen chloride, depending on the reaction conditions. The first stage of the reaction with hydrogen chloride is the formation of the colourless, viscous liquid BHjCl PH3 (see below). 

By means of a kinetic investigation of the reaction between diborane and phosphine at 0 °C in the gas phase, Brumberger and Marcus were able to describe the probable course of the reaction using the following equations  

This adduct begins to decompose to diborane and H3PBH2Br at -45 °C The latter compound is stable up to 0 °C. At this temperature it polymerises slowly by splitting off hydrogen  

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