Thuéry P, Harrowfield J. Cavity Formation in Uranyl Ion Complexes with Kemp's Tricarboxylate: Grooved Diperiodic Nets and Polynuclear Cages.
Inorg Chem 2021;
60:1683-1697. [PMID:
33435670 DOI:
10.1021/acs.inorgchem.0c03205]
[Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Kemp's triacid (cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid, H3kta) was reacted with uranyl nitrate under solvo-hydrothermal conditions in the presence of diverse counterions or additional metal cations to give eight zero- or diperiodic complexes. All the coordination polymers in the series, [PPh3Me][UO2(kta)]·0.5H2O (1), [PPh4][UO2(kta)] (2), [C(NH2)3][UO2(kta)] (3), [Cd(bipy)3][UO2(kta)]2 (4), and [Zn(phen)3][UO2(kta)]2·2H2O (5) (bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline) crystallize as networks with the hcb topology, the ligand being in the chair conformation with the three carboxylate groups equatorial, except in 3, in which the axial/diequatorial boat conformation is present. Various degrees of corrugation and different arrangements of neighboring layers are observed depending on the counterion, with complexes 4 and 5, in particular, displaying cavities containing the bulky cations. [Co(en)3]2[(UO2)2(kta)(Hkta)2]2·2NMP·10H2O (6) (en = 1,2-ethanediamine; NMP = N-methyl-2-pyrrolidone) contains a metallatricyclic, tetranuclear anionic species, displaying two clefts in which the cations are held by extensive hydrogen bonding, and with the ligands in both triaxial chair and axial/diequatorial boat conformations. [(UO2)3Pb(kta)2(Hkta)(H2O)]2·1.5THF (7) (THF = tetrahydrofuran) and [(UO2)2Pb2(kta)2(Hkta)(NMP)]2 (8) are two heterometallic cage compounds containing only the convergent, triaxial chair form of the ligand, which have the same topology in spite of the different U/Pb ratio. These complexes are compared to previous ones also involving Kemp's triacid anions, and the roles of ligand conformation and of counterions in the formation of cavities, either in cage-like species or as grooves in diperiodic networks, is discussed.
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