A Very Brief Introduction to Boron Chemistry

1. A Very Brief Introduction to Boron Chemistry Kristina Orosz Nov. 5, 2004

2. Borosilicate glass-pyrex Detergents Flame retardants Ceramics Pyrotechnics Used in production of impact resistant steels Control rods in nuclear reactors Uses of Boron

3. Common Bonds in Boranes • 2c-2e- B-H • 3c-2e- B-H-B • 2c-2e- B-B • 3c-2e- B-B-B

4. 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.

5. B2H6 MO Diagram Wade, K. Electron Deficient Compounds. London: Nelson, 1971. 30.

6. 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.

7. 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.

8. Elemental Forms of Boron b-rhombohedral, B12(B12)12, (B12)(B12)(B60) a- rhombohdral Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001. 251-2.

9. Boron Deltahedra – Parent Clusters Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001. 275.

10. Boron Hydrides Housecroft, C. E.; Sharpe, A. G. inorganic Chemistry. New York: Pearson Education Limited, 2001. 272.

11. 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.

12. Wade’s Rules • n = number of B atoms in parent closo-deltahedron • 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

13. 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 Using Wade’s Rules

14. 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.

15. CarboranesC2B10H12 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.

16. 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

17. 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.