carboranes and it's types - closo,nido,archano.pptx

Carboranes and it's types

1. CARBORANES Saravanakumar.M Msc.chemistry

2. CARBORANES Carboranes are mixed hydrides of boron and carbon in which carbon and boron atoms occupy the vertices of triangulated polyhedron. Carboranes are most important heteroboranes. Carboranes are member of a class of organometallic compounds containing carbon (C), boron (B), and hydrogen (H). General formula of carboranes is C 2 B n H n+m , where n is an integer carboranes with n ranging from 3 to 10 have been characterized. Boranes and carboranes have same number of electrons in their bonding framework , will have similar structure.

3. TYPES OF CARBORANES CLOSO CARBORANES Closed, triangulated polyhedra structure. General formula: C 2 B n H n+2, Total number of electron in bonding framework is (2n+2)e - . i.e. (n+1) e pairs. Example-1,6-C 2 B 8 H 10

4. One corner of triangulated polyhedra is removed General formula: C 2 B n H n+4, Total number of electron in bonding framework is (2n+4)e - . i.e. (n+2) e - pairs. Example- C 2 B 4 H 8 , [1,7-C 2 B 9 H 12 ] - NIDO CARBORANES

5. ARACHNO CARBORANES Two corners of triangulated polyhedra is removed. General formula: C 2 B n H n+6, Total number of electron in bonding framework is (2n+6)e - . i.e. (n+4) e - pairs. Example- 1,3-C 2 B 7 H 13

6. WADE’S RULE In chemistry polyhedral skeletal electron pair theory provides electron containing rules useful for predicting structures of boranes and carboranes. It is formulated by Wade and hence it is called as Wade’s rule. In Wade’s rule Each BH unit donates 2e - to skeletal structures. Each CH unit donates 3e - . -ve charge on borane gives an electron. Additional hydrogen atom gives one electrons each. Types Formula Skeletal Electron Pairs Example Closo B n H n n + 1 [B 5 H 5 ] 2- Nido B n H n+4 n + 2 B 2 H 6 Arachno B n H n+6 n + 3 B 4 H 10 Hypho B n H n+8 n + 4 None

7. APPLICATIONS OF BORANES AND CARBORANES Boranes are used as rocket fuels in supersonic aeroplanes. Used as catalyst in polymerisation reaction Used as reducing agent in organic reactions Boranes can be used as vulcanising agent for natural and synthetic rubber. Used in borane coating

8. CONCLUSION Boranes are colourless and gaseous at room temperatures. Boranes are highly reactive and reacts violently with water. In boranes 3c-2e bonds are present; It is unique type of bond present in boranes only. Carboranes are mixed hydrides of boron and carbon. And have same structure like boranes. Carboranes derived from pyrolysis of boranes