Reactive intermediates and molecular beam mass spectra of the boranes [1]

Abstract

Molecular beam mass spectrometric work on the lower boron hydrides is reported. Borane, BH3, and tetraborane (8), B4H8, were formed by reactions involving loss of BH3, CO, and, in the latter case, H2 from the appropriate molecules. This ensemble of reactions permitted unambiguous identification of each species. A route to B3H7 from B3H7PX3 is proposed. Investigation of the “stable” and “unstable” boranes and isotopically labelled molecules permits correlations of the mass spectra, determination of a structure ((B4H9)2), and identification of fragmentation pathways. Steady state pyrolysis in the ion source is particularly insidious. Because of it, previous appearance potential and theoretical fragmentation studies of e. g., B4H10 are virtually meaningless.

Evaluating the Role of Triborane(7) As Catalyst in the Pyrolysis of Tetraborane(10)

“…Two reactions and , both first order in B 4 H 10 , have been claimed to be the rate-limiting step in the initial stages of pyrolysis. − normalB 4 normalH 10 → normalB 4 normalH 8 + normalH 2 normalB 4 normalH 10 → normalB 3 normalH 7 + BH 3 Reaction was proposed as the rate-determining step from several experimental observations. First, the reaction between B 4 H 10 and ethylene yielded B 4 H 8 (C 2 H 4 ), while the reaction between deuterated ethylene and B 4 H 10 yielded B 4 H 8 (C 2 D 4 ). , Next, B 4 H 8 D 2 was captured as the product of the reaction between B 4 H 8 CO and D 2 .…”