Transcript Slide 1

A Very Brief Introduction to
Boron Chemistry
Kristina Orosz
Nov. 5, 2004
Uses of Boron
• Borosilicate glasspyrex
• Detergents
• Flame retardants
• Ceramics
• Pyrotechnics
• Used in production of
impact resistant
steels
• Control rods in
nuclear reactors
Common Bonds in Boranes
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2c-2e3c-2e2c-2e3c-2e-
B-H
B-H-B
B-B
B-B-B
Diborane B2H6
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry: principles of structure and reactivity, 4th
ed. New York: HarperCollins College Publisher, 1993. 790.
B2H6 MO Diagram
Wade, K. Electron Deficient Compounds. London:
Nelson, 1971. 30.
Tetraborane B4H10
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry: principles of structure and reactivity, 4th
ed. New York: HarperCollins College Publisher, 1993. 794.
Dodecaborane
[B12H12]2-
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry:
principles of structure and reactivity, 4th ed. New York:
HarperCollins College Publisher, 1993. 795.
Elemental Forms of Boron
a- rhombohdral
b-rhombohedral,
B12(B12)12, (B12)(B12)(B60)
Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001.
251-2.
Boron Deltahedra – Parent
Clusters
Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001.
275.
Boron Hydrides
Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001.
272.
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry:
principles of structure and reactivity, 4th ed. New York:
HarperCollins College Publishing, 1993. 799.
Wade’s Rules
• n = number of B atoms in parent closodeltahedron
• Always n+1 bonding e- pairs and n+1
bonding MOs
– nido has n-1 vertices
– arachno has n-2 vertices
– hypho has n-3 vertices
Using Wade’s Rules
• Find total available bonding e-s:
– Each B-H unit gives 2 e-s
– Each additional H gives 1 e– Overall charge
• Find parent closo-deltahedron
– n+1 bonding e- pairs
– Is it closo, nido, arachno, hypho?
– Lose highest connectivity B first then
lose adjacent sites
• Determine number of remaining
hydrogen atoms
– Each vertex has a H
– “sew up” hole with H atoms
• Bridging H atoms
• Low connectivity B atoms can get another
2c-2e- B-H bond
• Try to keep it as symmetrical as possible
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry: principles of structure and reactivity, 4th
ed. New York: HarperCollins College Publisher, 1993. 798.
Carboranes
C2B10H12
ortho
meta or neo
para
Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry: principles of structure and reactivity, 4th
ed. New York: HarperCollins College Publisher, 1993. 801.
Boron Neutron Capture Therapy
(BNCT)
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10B
has large cross-section for neutron
capture
10B +  a + 7Li
Products can kill cells
Cancer treatment
Cages - need high [10B] in cell
References
Dreiss, Matthias, ed., and Heinrich Nöth, ed. Molecular Clusters of the Main
Group Elements. Weinheim: Wiley-VCH, 2004. 95-125.
Housecroft, Catherine E. Boranes and Metallaboranes: structure, bonding, and
reactivity. 2nd ed. New York: Ellis Horwood, 1994. 1-20, 93-116.
Housecroft, Catherine E., and Alan G. Sharpe. Inorganic Chemistry. New York:
Pearson Education Limited, 2001. 245-279.
Huheey, James E., Ellen A. Keiter, and Richard L. Keiter. Inorganic Chemistry:
principles of structure and reactivity. New York: HarperCollins College
Publishers, 1993. 789-801.
Wade, Kenneth. Electron Deficient Compounds. London: Nelson, 1971. 1-61.