1. New Directions for Higher Boranes
Bjarne R. S. Hansen

2. Introduction Molecular boranes have been known for 100 years!
-First borane correctly identified (B4H10) in 1912 by A. Stock
Molecular boranes have a rich history in rocket fuel applications
-Boranes (B-H) 70,000 kJ/kg
-Alkanes (C-H) 42,000 kJ/kg
Metal borohydrides first reported in 1940 by
Schlesinger, Brown & Burg: Al(BH4)3, Be(BH4)2, LiBH4
F. M. Hawthorne synthesized the B12H122- anion in 1960
Nobel Prize in Chemistry 1976: W. N. Lipscomb for his studies on the structure of boranes illuminating problems of chemical bonding
Nobel Prize in Chemistry 1979: H. C. Brown
for boron compounds as reducing agents in organic chemistry

3. Borane Anions Closo BnHn Nido BnHn+4 Arachno BnHn+6 5 6 7 8 9 10 11 12
/j.ccr

4. Metal Borane Synthesis
Hansen et al. Coord Chem Rev, 2016, /j.ccr

5. B10H102- and B12H122- compounds and derivatives
NH4+
Table available here:
Hansen et al. Coord Chem Rev, /j.ccr
Often hydrates or solvates!

6. Closo-borane applications
Ion conductors
PCCP, 2013,15,
Carborane-containing amino acids
Medicine (BNCT) – Cancer Therapy
NH3/H2 storage
J. Mater. Chem., 2010, 20,
Li2B12H12∙7NH3
Org. Lett., 2006, 8 (8), 1713–1716
Light
Nano-Car
Texas, USA
Polym. Chem., 2011, 2, 2122
Polymers/Ceramics
Luminescence
J. Mater. Chem. A, 2015, 3, 22853

7. Solid-State Ion Conductivity
Hansen et al. Coord Chem Rev, 2016, /j.ccr

8. Silver Boranes: Synthesis
λ = Å
Hydroxides, metals, nitrates or oxides can also be used instead of carbonates
Muetterties, Chemistry of Boranes VIII, salts and acids of B10H102- and B12H122-,1964
Paskevicius et al. Nature Energy, 2016, submitted

9. Silver Boranes: Structures
β-Ag2B12H12
α-Ag2B12H12
Fm-3m
Pa-3
50%
12.5%
Paddlewheel mechanism
B12H122- anion highly dynamic
Ag+ in partially occupied sites with much closer jumps
Only certain Ag-sites are permitted for particular B12H122- orientations (Ag-H distance)
Boron, Silver
Paskevicius et al. Nature Energy, 2016, submitted

10. Silver Boranes: Ion ConductivityAu
Sample
Electrochemical Impedance Spectroscopy
Mark Paskevicius Silver boranes, worth their weight in gold?
Tuesday, Room 3
Paskevicius et al. Nature Energy, 2016, submitted

11. Aim is to study structures and decomposition mechanism
NH3 storage in closo-boranes
Or indirect H storage
MB12H12
M = Li2, Na2, Ca
Flask placed in cooling bath
λ = Å
Aim is to study structures and decomposition mechanism
Hansen et al. J. Phys. Chem. C, 2016, to be submitted

12. NH3 storage in closo-boranes
Na2B12H12∙2NH3
Trigonal, P-3m1 (no. 164)
a = (1) Å ,
c = (2) Å,
In situ SR-PXD of ammoniated Na2B12H12
HT-Na2B12H12
LT-Na2B12H12
Na2B12H12∙4NH3
Monoclinic, P21/n (no. 14)
a = (2)Å ,
b = (3) Å,
c = (3) Å,
β = (18)°
Boron, Sodium, Nitrogen, Hydrogen
Na2B12H12∙xNH3
λ = Å
Hansen et al. J. Phys. Chem. C, 2016, to be submitted

13. NH3 storage in closo-boranes
λ = Å
Na2B12H12
CaB12H12
Compound
NH3 content (wt%)
H content from NH3 (wt%)
Total H content (wt%)
Li2B12H12∙7NH3
43.36
7.70
12.10
Na2B12H12∙4NH3
26.62
4.73
9.45
CaB12H12∙6NH3
35.97
6.39
10.64
Thermal and chemical stability advantageous
No formation of BN
Reversible
Hansen et al. J. Phys. Chem. C, 2016, to be submitted

14. NH3 storage in closo-boranes
Reversible NH3 storage
Thermal and chemical stability advantageous
No formation of BN
Reversible
Hansen et al. J. Phys. Chem. C, 2016, to be submitted

15. Conclusions Revisit old methods to make new materials
Extensive research foundation in the literature on metal boranes
New materials lead to ‘new’ and exciting properties
Ag2B10H10 and Ag2B12H12 are excellent ion conductors and have interesting structures
Ammine metal closo-boranes can be useful for reversible NH3/H2 storage or as DeNOX catalysts
There are large number of metal boranes to be explored for a broad number of applications
GO AND EXPLORE NOW!

16. Thank you for your attention!
Acknowledgements
Funding:
HAPPY BIRTHDAY
(…Yesterday)
Mark Paskevicius
Torben R. Jensen
Mark Paskevicius
Bo Richter
Mathias Jørgensen
Anders S. Jacobsen
Hai-wen Li
Etsuo Akiba
Nikolay Tumanov
Yaroslav Filinchuk
Antonio Santoru
Claudio Pistidda
Martin Dornheim
Thank you for your attention!