Room-Temperature Structure of Ammonia Borane

Mark E. Bowden; Graeme J. Gainsford; Ward T. Robinson

doi:10.1071/CH06442

RESEARCH ARTICLE

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Room-Temperature Structure of Ammonia Borane

Mark E. Bowden ^A , Graeme J. Gainsford ^A and Ward T. Robinson ^B

+ Author Affiliations

- Author Affiliations

^A Industrial Research Ltd, PO Box 30-310, Lower Hutt, New Zealand.

^B Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.

^C Corresponding author. Email.m.bowden@irl.cri.nz

Australian Journal of Chemistry 60(3) 149-153 https://doi.org/10.1071/CH06442
Submitted: 22 November 2006 Accepted: 23 January 2007 Published: 2 April 2007

Abstract

Structural determinations of ammonia borane (BH₃NH₃) have been carried out for the orthorhombic (at 90 K) and tetragonal (at 298 K) modifications using single-crystal X-ray data. The orthorhombic structure (space group Pmn2₁) agreed with a previously published neutron determination, while the tetragonal structure (I4mm) exhibited halos of hydrogen atom occupancy around both the nitrogen and boron atoms. The bond angles to the regions of hydrogen occupancy are consistent with the expected tetrahedral geometry for –BH₃ and –NH₃ groups. A new model for tetragonal BH₃NH₃ was constructed which accounts for the hydrogen disorder in the I4mm structure while introducing only weak new diffraction peaks. These peaks could not be found, however, and it is likely that the hydrogen disorder in tetragonal BH₃NH₃ arises from either rotations of higher than 3-fold order, or from random orientations of hydrogen-containing groups.

Acknowledgments

The authors thank Martin Ryan of Industrial Research Ltd for his assistance with some of the diffraction measurements. Funding from the New Zealand Foundation for Research, Science and Technology under contract C08X0416 is gratefully acknowledged.

References

Room-Temperature Structure of Ammonia Borane

Abstract

Acknowledgments

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