Kinetic studies of reactions of hexaborane(10) with other binary boranes in the gas phase

• Published in: Journal of organometallic chemistry 2000-12, Vol.614, p.144-152
• Main Authors: Attwood, Martin D, Greatrex, Robert, Greenwood, Norman N, Potter, Christopher D
• Format: Article
• Language: English
• Subjects: Binary boranes; Hexaborane; Kinetic studies; Mechanism; Thermolysis
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(00)00627-6

Cothermolysis reactions of B 6H 10 with the binary boranes B 2H 6, B 4H 10, B 5H 9, and B 5H 11 have been studied by a quantitative mass-spectrometric technique to gain insight into the role of B 6H 10 in borane interconversion reactions. Except in the B 6H 10–B 5H 9 system the initial rate of consumption of B 6H 10 was found to be considerably more rapid than in the thermolysis of B 6H 10 alone, indicating that interactions were occurring. Detailed kinetic studies of the B 6H 10–B 2H 6 and B 6H 10–B 4H 10 reactions showed that the rate of consumption of B 6H 10 was governed in each case by the rate-determining step in the decomposition of the co-reactant, the orders being 3/2 with respect to B 2H 6 and 1 with respect to B 4H 10; a considerable increase in the conversion of B 6H 10 to B 10H 14 at the expense of polymeric solids was also observed. Added hydrogen was found to have very little effect on the reaction rates and product distributions in the cothermolysis reactions, in marked contrast to its effect on the reactions of B 2H 6 and B 4H 10 alone. The kinetic results are entirely consistent with earlier suggestions, based on qualitative observations, that the reactive intermediates {B 3H 7} and {B 4H 8} are scavenged by reaction with B 6H 10, and suggest strongly that this borane, unlike B 6H 12, plays a pivotal role in the build-up to B 10H 14 and other higher boranes.