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In organometallic chemistry, a dicarbollide is an anion of the formula 2B9H11sup>2-. Various isomers exist, but most common is 1,2-dicarbollide derived from
:C2B10H12 + NaOEt + 2 EtOH → Na+C2B9H12− + H2 + B(OEt)3
:Na+C2B9H12− + NaH → Na2C2B9H11 + H2
The dianion derived from ortho-carborane, 2B9H11sup>2- is a nido cluster. The nomenclature rules call the high coordination number vertex as 1. Thus the nido cluster with two adjacent carbon centers on the rim is the 7,8-isomer.
A variety of complexes are known with one or two dicarbollide ligands. An example of a 1:1 complex is n(CO)3(η5-7,8-C2B9H11)sup>−.
Most heavily studied are complexes with two dicarbollide ligands, especially sandwich complexes. Thus, these are prepared by
In organometallic chemistry, a dicarbollide is an anion of the formula 2B9H11sup>2-. Various isomers exist, but most common is 1,2-dicarbollide derived from ortho-carborane
Ortho-carborane is the organoboron compound with the formula C2B10H12. The prefix ''ortho'' is derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant poly ...
. These dianions function as ligands, related to the cyclopentadienyl anion
In chemistry, the cyclopentadienyl anion or cyclopentadienide is an aromatic species with a formula of and abbreviated as Cp−. It is formed from the deprotonation of the molecule cyclopentadiene.
Properties
The cyclopentadienyl anion ...
. Substituted dicarbollides are also known such as 2B9H10(pyridine)sup>− (pyridine bonded to B) and 2R2B9H9sup>2- (R groups bonded to carbon).
Synthesis of dicarbollides
Dicarbollides are obtained by base-degradation of 12-vertex dicarborane
Carboranes are electron-delocalized (non-classically bonded) clusters composed of boron, carbon and hydrogen atoms.Grimes, R. N., ''Carboranes 3rd Ed.'', Elsevier, Amsterdam and New York (2016), . Like many of the related boron hydrides, these ...
s. This degradation of the ortho derivative has been most heavily studied. The conversion is conducted in two-steps, first "deboronation" and second deprotonation:
:C2B10H12 + NaOEt + 2 EtOH → Na+C2B9H12− + H2 + B(OEt)3
:Na+C2B9H12− + NaH → Na2C2B9H11 + H2
The dianion derived from ortho-carborane, 2B9H11sup>2- is a nido cluster. The nomenclature rules call the high coordination number vertex as 1. Thus the nido cluster with two adjacent carbon centers on the rim is the 7,8-isomer.
Coordination compounds
A variety of complexes are known with one or two dicarbollide ligands. An example of a 1:1 complex is n(CO)3(η5-7,8-C2B9H11)sup>−.
Most heavily studied are complexes with two dicarbollide ligands, especially sandwich complexes. Thus, these are prepared by salt metathesis reaction
A salt metathesis reaction, sometimes called a double displacement reaction, is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding a ...
s, as illustrated by the synthesis of the ferrocene
Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, ...
analogue:
:2 Na2C2B8H11 + FeCl2 → Na2 e(C2B8H11)2 + 2 NaCl
These bisdicarbollide dianions are often readily oxidized. Fe(III), Co(III), Ni(III), and Ni(IV) derivatives are known. In some cases, the oxidation induces rearrangement of the C2B9 cage to give complexes where the carbon centers are nonadjacent.
Precursor to other carboranes
Diprotonation of 2B9H11sup>2− gives the neutralcarborane
Carboranes are electron-delocalized (non-classically bonded) clusters composed of boron, carbon and hydrogen atoms.Grimes, R. N., ''Carboranes 3rd Ed.'', Elsevier, Amsterdam and New York (2016), . Like many of the related boron hydrides, these ...
C2B9H13. Pyrolysis of this nido cluster gives closo-C2B9H11. Chromate-oxidation of 2B9H12sup>− results in deboronation, giving the C2B7H13. This carborane features two CH2 vertices.Grimes, R. N., ''Carboranes 3rd Ed.'', Elsevier, Amsterdam and New York (2016), .
Homogeneous catalysis
The clam-shell dicarbollide complex (Cp*)(C2B9H11)ZrCH3 catalyzes alkene polymerization.{{cite journal , author1=Crowther, D. J. , author2=Baenziger, N. C. , author3=Jordan, R. F. , title = Group 4 metal dicarbollide chemistry. Synthesis, structures and reactivity of electrophilic alkyl complexes (Cp*)(C2B9H11)M(R), M = Hf, Zr , journal = Journal of the American Chemical Society , year = 1991 , volume = 113 , issue = 4 , pages = 1455–1457 , doi = 10.1021/ja00004a080References