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Frontiers of Chemical Science and Engineering >> 2018, Volume 12, Issue 3 doi: 10.1007/s11705-018-1743-6

Crystal-to-crystal transformation from the triclinic to the cubic crystal system by partial desolvation

Institute of Inorganic Chemistry, RWTH Aachen University, Aachen, Germany

Accepted: 2018-08-23 Available online: 2018-09-18

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Abstract

Diffusion reaction of the labile building block Mg(acacCN)2 (acacCN= 3-cyanoacetylacetonate) with silver salts leads to a series of solvated Mg/Ag bimetallic coordination polymers with composition [Mg(acacCN)3Ag]·solvent. Despite their common stoichiometry, the topology of these polymers depends on the solvent of crystallization. The two-dimensional coordination compound [Mg(acacCN)3Ag]·4CHCl3 in space group P1‾ is obtained as platelet-shaped crystals from a mixture of methanol and chloroform. When kept in the reaction mixture, these thin plates within one week convert to isometric tetrahedral crystals of the 3D network [Mg(acacCN)3Ag]·2CHCl3 in the cubic space group P213. The transformation reaction proceeds via dissolution and recrystallization. The co-crystallized solvent molecules play an important role for stabilizing the target structure: They subtend Cl···Cl contacts and interact via non-classical C–H···O hydrogen bonds with the coordination framework. In the new cubic coordination network, both Mg(II) and Ag(I) adopt octahedral coordination, with unprecedented face-sharing by bridging O atoms of three acetylacetonato moieties. Prolonged standing of [Mg(acacCN)3Ag]·2CHCl3 in the reaction medium leads to further degradation, under formation of [Ag(acacCN)].

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