Diastereoselective Assembly of Helicates Incorporating a Hexadentate Chiral Scaffold

Constable, Edwin C. and Zhang, Guoqi and Housecroft, Catherine E. and Neuburger, Markus and Zampese, Jennifer A.. (2010) Diastereoselective Assembly of Helicates Incorporating a Hexadentate Chiral Scaffold. European Journal of Inorganic Chemistry, 2010 (13). pp. 2000-2011.

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Official URL: http://edoc.unibas.ch/dok/A5841489

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The condensation of enantiopure (1R,2R)-(–)-1,2-diaminocyclohexane with two equivalents of 2,2′-bipyridine-6-carbaldehyde followed by reduction with NaBH4 allows the facile synthesis of the enantiopure hexadentate ligand (R,R)-3. Each tridentate metal-binding domain in (R,R)-3 exhibits a degree of flexibility arising from inversion at the amine nitrogen centre and rotation about N–C and C–C single bonds. This leads to the formation of either M-[M{(R,R)-3}]2+ or P-[M{(R,R)-3}]2+. The solid-state structures of the copper(II), iron(II) and zinc(II) complexes of (R,R)-3 all show a preference for M-[M{(R,R)-3}]2+. In solution, [Fe{(R,R)-3}]2+ exists predominantly as one diastereoisomer (assumed to be the M-form). The preference for the M- over P-form is rationalized in terms of a favourable anti configuration of the NH and cyclohexane-1,2-diyl CH hydrogen atoms in the M-form, and an unfavourable syn-configuration in the P-form. When (R,R)-4, the Schiff base analogue of (R,R)-3, combines with zinc(II) or silver(I), [2+2] double helicates with M-chirality assemble in the solid state. With (S,S)-4, iron(II) also assembles into a dinuclear, double helicate with M-handedness. Complete stereoselectivity is observed in solution with NMR spectroscopic data indicating the presence of one diastereoisomer. The preference for a dinuclear over mononuclear helicate can be traced to a decrease in ligand flexibility on going from 3 (saturated backbone) to 4 (unsaturated imine backbone).
Faculties and Departments:05 Faculty of Science > Departement Chemie > Former Organization Units Chemistry > Anorganische Chemie (Housecroft)
UniBasel Contributors:Housecroft, Catherine Elizabeth and Constable, Edwin Charles and Zhang, Guoqi and Zampese, Jennifer Ann and Neuburger, Markus
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:08 May 2017 08:09
Deposited On:14 Sep 2012 06:59

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