Helical dinuclear 3d metal complexes with bis(bidentate) [S,N] ligands: synthesis, structural and computational studies

A diprotic bis(β-thioketoimine) ligand precursor featuring a flexible 4,4′-methylbis(aniline) linker, H 2 2 , was synthesised via treatment of the corresponding bis(β-ketoimine) with Lawesson's reagent. Lithiation of H 2 2 and coordination with one equivalent of d-block metal( ii ) chlorides MC...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2024-11, Vol.53 (43), p.1768-17619
Main Authors: Allen, Jamie, Saßmannshausen, Jörg, Singh, Kuldip, Kilpatrick, Alexander F. R
Format: Article
Language:English
Subjects:
Aniline
Bonding strength
Cobalt compounds
Coordination compounds
Iron
Ligands
Oxidation
Reagents
Zinc
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Summary:A diprotic bis(β-thioketoimine) ligand precursor featuring a flexible 4,4′-methylbis(aniline) linker, H 2 2 , was synthesised via treatment of the corresponding bis(β-ketoimine) with Lawesson's reagent. Lithiation of H 2 2 and coordination with one equivalent of d-block metal( ii ) chlorides MCl 2 (THF) x (M = Fe, Co and Zn) yielded a corresponding series of homoleptic dinuclear complexes, [M 2 (μ- 2 ) 2 ]. X-ray diffraction analysis reveals a tetrahedral geometry for the two metals and a double-stranded helicate structure arising from inter-strand face-face π-stacking. These interactions create a helical 'twist' of ca. 70°. Utilising a bulky mononucleating β-thioketoiminate ligand, [ 3 ] − , the analogous series of homoleptic monometallic complexes, [M( 3 ) 2 ] (M = Fe, Co and Zn), were prepared and characterised by spectroscopic and analytical techniques. A comprehensive DFT study of all complexes reveals a stronger M-S bonding compared to M-N due to a higher degree of covalency. Solution magnetic studies and natural bonding orbital calculations on the mono- and dinuclear iron and cobalt complexes are consistent with high-spin tetrahedral Fe( ii ) and Co( ii ) centres, and cyclic voltammetry reveals both oxidation and reduction processes are accessible. A dinucleating [S,N] ligand with a flexible linker forms homobimetallic complexes with Fe, Co and Zn. These show a double-stranded helicate structure, stabilised by intramolecular π-π interactions, with homochirality at the two tetrahedral centres.
ISSN:1477-9226
1477-9234
DOI:10.1039/d4dt02395a