1. The dodecaborate anion has the structure of a regular icosahedron of boron atoms, each bonded to a hydrogen atom, forming B12H12. 2. It can be synthesized through several methods, including the pyrolysis of B3H8 or the reaction of diborane with borohydrides. 3. Derivatives of dodecaborate anion have been made through substitution reactions replacing hydrogen with groups like carbonyl, amino, phosphonium, and others.

1. P R E S E N T E D B Y
K . M U T H U K A N N A N

2. DODECABORANE:
Introduction:
The dodecaborate anion(12), [B12H12]2-, has the structure
of a regular icosahedron of boron atoms, with each boron atom being
attached to a hydrogen atom .The existence of
the dodecaborate anion, [B12H12]2-,was predicted
by H. C. Longuet-Higgins and M.de V. Roberts
in 1955 on the basis of MO and LCAO
calculations. This prediction was verified
experimentally by Hawthorne and Pitochelli
in 1960. It is also known as dodecahydro-closo-
dodecaborate anion.

4. Preparations:
It may be synthesised by the pyrolysis of the [B3H8]- ion .
Diborane and borohydride reacts to give dodecaborane
anion.
One of the most convenient methods of synthesis of the
closo-dodecaborate anion is pyrolysis of triethylamine-borane with
decaborane(14) at 190 °C giving the desired product in 92% yield.
B10H14 + 2 Et3N·BH3 → (Et3NH)2[B12H12] + 3 H2
5[B3H8]-
[B12H12]-2
+ 3[BH4]-
+ 8H2
2[BH4]-
+ 5B2H6
[B12H12]-2
+ 13H2

5. Another convenient and widely used in laboratory practice
method of synthesis the [B12H12]2-anion is the reaction of sodium
tetrahydroborate with decaborane at 160 °C giving the product in 91%
yield.
B10H14 + 2 NaBH4 → Na2[B12H12] + 5 H2
Metallo derivatives:
The reactions of the closo-dodecaborate anion with mercury
acetate and trifluoroacetate gave metallated derivatives
[B12H12–n(HgOC(O)CX3)n]2– (X = H, F; n = 1–12). However, in
contrast to the mercurated carborane derivatives, the metallated
dodecaborate derivatives are unstable and easily decompose in
solution and in the solid state.

6. Derivative with boron-carbon bond:
The reaction of the [B12H12]2– with carbon monoxide at 1000
atm and 130 °C in the presence of [Co2(CO)8] as a catalyst gives almost a
quantitative conversion to a mixture of mono- and disubstituted carbonyl
derivatives, [B12H11CO], [1,12B12H10(CO)2], and [1,7-B12H10(CO)2].
[B12H12]2– + CO → [B12H11CO]+ [1,7-B12H10(CO)2]+[1,12B12H10(CO)2].
Derivative with boron-nitrogen bond:
The reaction of the closo-dodecaborate anion with
hydroxylamine-O-sulfonic acid in aqueous solution giving mono- and
disubstituted amino derivatives which, because of their high basicity, are
readily isolated in the N-protonated forms.

7. The diamino derivative was obtained as a mixture of the 1,7-, 1,12-,
and a small amount of 1,2-isomers.
[B12H12]2– → [B12H11NH3]- → [1,2-, 1,7- and 1,12-B12H10(NH3)2]
Derivative with boron-phosphate and boron-arsenic bond:
The trimethylphosphonium derivatives of the dodecaborate
anion were obtained by pyrolysis of the trimethylphosphine–borane
complex, where the [B12H11PMe3]– yield reaches 60%.
Me3P·BH3 → [B12H11PMe3]– + [B12H10(PMe3)2]
The [1,7-B12H10(PMe2Ph)2] complex was obtained by
the reaction of the closo-dodecaborate anion with [PdCl2(Me2PhP)2] in
tetrahydrofuran.

8. [B12H12]2– + [PdCl2(Me2PhP)2] → [1,7-B12H10(PMe2Ph)2]
The trimethylarsonium derivatives [B12H11AsMe3]– and
[B12H10(AsMe3)2] were obtained by pyrolysis of the trimethylarsine–
borane complex.
Derivative with boron-oxygen bond:
Alkylation of [B12H11OH]2– with alkyl halides in dimethyl
sulfoxide in the presence of potassium hydroxide or in acetone in the
presence of potassium carbonate gives the alkoxy derivatives
[B12H11OR]2–.
[B12H12OH]2- + RX → [B12H12OR]2-
R = C2H5, (CH3)2CH, C6H5CH2

9. Derivative with boron-Sulphur bond:
[B12H12]2– anion with thiourea under conditions of chemical
oxidation.
[B12H12] 2– + SC(NH2)2 → [B12H11SC(NH2)2]– + OH– → [B12H11SH]2–
Derivative with boron-selenium bond:
The selenocyanato derivative [B12H11SeCN]2– was prepared by
the reaction of the closo-dodecaborate anion with (SeCN)2 in
dichloromethane at –100°C.
[B12H12]2– → [B12H11SeCN]2–

10. Applications:
⸙ Closo-dodecaborate anion takes advantage of high stability under
usual conditions that allows to use its salts as components of high
burning composite propellants.
⸙ An important field is using lithium closo-dodecaborates Li2[B12H12]
and Li2[B12Cl12] as used for advanced rechargable lithium batteries.
⸙ The main direction of application of the closododecaborate
derivatives nowadays is medicine.
⸙ [B12H12]2-, [B12(OH)12]2- and [B12(OMe)12]2- show promise for use in
drug delivery.
⸙ Salts of dodecaborane is therapeutic agent in cancer treatment.