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Issue 11, 2016
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Structural insights into the coordination chemistry and reactivity of a 3,3′-bis-imine-2,2′-bipyridine ligand

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Abstract

The coordination chemistry of the bis-salicyl-appended Schiff-base ligand L8 with Lewis acidic metal ions affords the mononuclear complex [Sn(L9)Cl4] (1) and two paramagnetic dimers [Cu(L9)(sal)]2(ClO4)2, (2) and [Mn(L9)Cl2(EtOH)]2] (3). The X-ray crystal structures of 1–3 reveal a propensity for L8 to undergo metal catalyzed hydrolysis and cyclization to the diazepine ligand L9. Theoretical calculations on L8 and a model Sn(IV) complex reveal that coordination to a metal ion weakens the imine bonds, rendering them more susceptible to hydrolysis reactions and/or attack by nucleophiles. In contrast, reaction of L8 with FeCl3 in the presence of base affords the partial hydrolysis product [Fe(L10)2]Cl·CH3CN (4). Tuning the reaction conditions via the addition of a second base slows down the hydrolysis of the ligand sufficiently to afford a few crystals of the μ2-oxo diferric complex (μ-O)[Fe(L8)]2·2CH3CN (5) in which intact L8 coordinates to the Fe(III) in a bis-bidentate manner through a deprotonated salicyl oxygen and a bis-imine nitrogen lone pair, with the nitrogen atoms of its 2,2′-bipyridine remaining uncoordinated.

Graphical abstract: Structural insights into the coordination chemistry and reactivity of a 3,3′-bis-imine-2,2′-bipyridine ligand

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Publication details

The article was received on 01 Dec 2015, accepted on 25 Jan 2016 and first published on 26 Jan 2016


Article type: Paper
DOI: 10.1039/C5CE02349A
CrystEngComm, 2016,18, 1892-1903

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    Structural insights into the coordination chemistry and reactivity of a 3,3′-bis-imine-2,2′-bipyridine ligand

    R. Gumbau-Brisa, J. J. Hayward, J. D. Wallis, J. M. Rawson and M. Pilkington, CrystEngComm, 2016, 18, 1892
    DOI: 10.1039/C5CE02349A

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