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Crystal structures of the carborane dianions [1,4-(PhCB₁₀H₁₀C)₂C₆H₄]²⁻ and [1,4-(PhCB₁₀H₁₀C)₂C₆F₄]²⁻ and the stabilizing role of the para-phenylene unit on 2n+3 skeletal electron clusters.

Kahlert J, Stammler HG, Neumann B, Harder RA, Weber L, Fox MA - Angew. Chem. Int. Ed. Engl. (2014)

Bottom Line: While carboranes with 2 n+2 and 2 n+4 (n=number of skeletal atoms) skeletal electrons (SE) are widely known, little has been reported on carboranes with odd SE numbers.The salts of the dianions were isolated by reduction with sodium metal and their unusual structures were determined by X-ray crystallography.The diamagnetic dianions contain two 2 n+3 SE clusters where each cluster has a notably long carborane C-carborane C distance of ca 2.4 Å.

View Article: PubMed Central - PubMed

Affiliation: Fakultät für Chemie der Universität Bielefeld, 33615 Bielefeld (Germany).

No MeSH data available.


Generic structures for [3]2− and [4]2− (left) and 5 (right) with atom numbering. The Me3Si groups attached to the carbon atoms in 5 are omitted for clarity.
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sch02: Generic structures for [3]2− and [4]2− (left) and 5 (right) with atom numbering. The Me3Si groups attached to the carbon atoms in 5 are omitted for clarity.

Mentions: While both clusters in these systems 3 and 4 are significantly distorted on reduction, the phenyl groups remain largely unchanged whereas the ═C6H4═ and ═C6F4═ bridges are distorted as well. The bridges become more quinoid-like with the bond between the aryl ring and the cluster shortened by 0.08–0.09 Å. While this bond shortening agrees with an increased bond order, it is quite small when compared to carborane anions with substantial exo-multiple bond character.6, 12 The geometrical parameters of the ═C6H4═ ring in [3]2− resemble the phenylene units in the experimentally determined geometries of para-quinodimethane analogues, disilaquinodimethane 6 and diboraquinodimethane 7 (Scheme 3).22, 23 The transitions responsible for the colors in [3]2− (686 nm), 6 (555 nm) and 7 (630 nm) presumably arise from the ═C6H4═ ring in all cases.


Crystal structures of the carborane dianions [1,4-(PhCB₁₀H₁₀C)₂C₆H₄]²⁻ and [1,4-(PhCB₁₀H₁₀C)₂C₆F₄]²⁻ and the stabilizing role of the para-phenylene unit on 2n+3 skeletal electron clusters.

Kahlert J, Stammler HG, Neumann B, Harder RA, Weber L, Fox MA - Angew. Chem. Int. Ed. Engl. (2014)

Generic structures for [3]2− and [4]2− (left) and 5 (right) with atom numbering. The Me3Si groups attached to the carbon atoms in 5 are omitted for clarity.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4257503&req=5

sch02: Generic structures for [3]2− and [4]2− (left) and 5 (right) with atom numbering. The Me3Si groups attached to the carbon atoms in 5 are omitted for clarity.
Mentions: While both clusters in these systems 3 and 4 are significantly distorted on reduction, the phenyl groups remain largely unchanged whereas the ═C6H4═ and ═C6F4═ bridges are distorted as well. The bridges become more quinoid-like with the bond between the aryl ring and the cluster shortened by 0.08–0.09 Å. While this bond shortening agrees with an increased bond order, it is quite small when compared to carborane anions with substantial exo-multiple bond character.6, 12 The geometrical parameters of the ═C6H4═ ring in [3]2− resemble the phenylene units in the experimentally determined geometries of para-quinodimethane analogues, disilaquinodimethane 6 and diboraquinodimethane 7 (Scheme 3).22, 23 The transitions responsible for the colors in [3]2− (686 nm), 6 (555 nm) and 7 (630 nm) presumably arise from the ═C6H4═ ring in all cases.

Bottom Line: While carboranes with 2 n+2 and 2 n+4 (n=number of skeletal atoms) skeletal electrons (SE) are widely known, little has been reported on carboranes with odd SE numbers.The salts of the dianions were isolated by reduction with sodium metal and their unusual structures were determined by X-ray crystallography.The diamagnetic dianions contain two 2 n+3 SE clusters where each cluster has a notably long carborane C-carborane C distance of ca 2.4 Å.

View Article: PubMed Central - PubMed

Affiliation: Fakultät für Chemie der Universität Bielefeld, 33615 Bielefeld (Germany).

No MeSH data available.