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Published in

International Union of Crystallography, IUCrJ, 1(5), p. 45-53, 2018

DOI: 10.1107/s2052252517015081

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Snapshot and crystallographic observations of kinetic and thermodynamic products for NO2S2 macrocyclic complexes

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Direct observation and structural characterization of a kinetic product and a thermodynamic product for complexes with an NO2S2 macrocycle (L) are reported. L reacts with copper(I) iodide to give a mononuclear complex [Cu(L)]2(Cu2I4)·2CH2Cl2 (1), featuring three separate units. When cadmium(II) iodide was reacted with L, an anion-coordinated complex [Cd(L)I]2(Cd2I6)·4CH3CN (2) with a needle-type crystal shape was formed as the kinetic product. Interestingly, when the needle-type kinetic product was left undisturbed in the mother solution it gradually transformed to the pseudo-dimer complex [Cd2(L)2I2](Cd2I6) (3) with a brick-type crystal shape as the thermodynamic product. The dissolution–recrystallization process resulted in the elimination of the lattice solvent molecules (acetonitrile) in 2 and the contraction of two neighboring macrocyclic complex units [Cd(L)I]+, forming the pseudo-dimer 3 via an intermolecular Cd...I interaction between two monomers. For the entire process from kinetic to thermodynamic products, it was possible to obtain sequential photographic snapshots, single-crystal X-ray structures and powder X-ray diffraction patterns. For the copper(I) and cadmium(II) complexes, competitive NMR results agree with the solid-state data that show copper(I) has a higher affinity for L than does cadmium(II).