A Very Brief Introduction to Boron Chemistry

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A Very Brief Introduction to Boron Chemistry

• Kristina Orosz
• Nov. 5, 2004

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Uses of Boron

• Borosilicate glass-pyrex
• Detergents
• Flame retardants
• Ceramics

• Pyrotechnics
• Used in production of impact resistant steels
• Control rods in nuclear reactors

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Common Bonds in Boranes

• 2c-2e- B-H
• 3c-2e- B-H-B
• 2c-2e- B-B
• 3c-2e- B-B-B

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Diborane B2H6
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• B2H6 MO Diagram

Wade, K. Electron Deficient Compounds. London
Nelson, 1971. 30.
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Tetraborane B4H10
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• Dodecaborane B12H122-

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.
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Elemental Forms of Boron
b-rhombohedral, B12(B12)12, (B12)(B12)(B60)
a- rhombohdral
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Boron Deltahedra Parent Clusters
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Boron Hydrides
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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.
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Wades Rules

• n number of B atoms in parent closo-deltahedron
• Always n1 bonding e- pairs and n1 bonding MOs
• nido has n-1 vertices
• arachno has n-2 vertices
• hypho has n-3 vertices

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• 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
• n1 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

• Using Wades Rules

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CarboranesC2B10H12
ortho
meta or neo
para
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Boron Neutron Capture Therapy (BNCT)

• 10B has large cross-section for neutron capture
• 10B ? a 7Li
• Products can kill cells
• Cancer treatment
• Cages - need high 10B in cell

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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.