Cavity Formation in Uranyl Ion Complexes with Kemp’s Tricarboxylate: Grooved Diperiodic Nets and Polynuclear Cages

Abstract

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 = 2,2ʹ-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 neighbouring 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) 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) 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. We report here the synthesis and crystal structure of eight uranyl ion complexes with Kemp's triacid anions, five of which involve anionic, diperiodic coordination polymers and three polynuclear, closed species, both groups providing an example of where the ligand adopts a non-chair conformation. The anionic coordination oligomers or polymers of uranyl ion and Kemp's triacid anions are associated with cations of rather varied characteristics. Three of these counterions are organic (PPh3Me + , PPh4 + , C(NH2)3 +) and the others are either an additional metal ion (Pb 2+) or metal ion complexes ([Cd(bipy)3] 2+ , [Zn(phen)3] 2+ or [Co(en)3] 3+ , with bipy = 2,2ʹ-bipyridine, phen = 1,10-phenanthroline, and en = 1,2-ethanediamine). EXPERIMENTAL SECTION Syntheses. Caution! Uranium is a radioactive and chemically toxic element, and uranium-containing samples must be handled with suitable care and protection. [UO2(NO3)2(H2O)2]•4H2O (RP Normapur, 99%) was purchased from Prolabo. Kemp's triacid was from Aldrich and [Co(en)3]Cl33H2O was from Alfa-Aesar. Elemental analyses were ASSOCIATED CONTENT Accession Codes CCDC 2037808-2037815 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing

Plumbing the uncertainties of solvothermal synthesis involving uranyl ion carboxylate complexes

“…Even where the polyamine complex has no sites available for further coordination interactions, it can be of some utility for the isolation of crystalline products. In the case of [Co(en) 3 ] 3+ , for example, [36][37][38][39] this is due to the presence in this cation of up to 12 NH-donor sites known to engage in hydrogen bonding interactions, as found in the structures of a wide variety of simple salts of this cation. 40 The present report is intended to illustrate some of the uncertainties associated with the solvothermal method of synthesis by using the structures of four uranyl ion coordination polymers involving dicarboxylate ligands derived from acids containing long aliphatic chains, a large family of ligands which has been extensively investigated (e.g.…”

Ni(2,2′:6′,2″-Terpyridine-4′-carboxylate)2 Zwitterions and Carboxylate Polyanions in Mixed-Ligand Uranyl Ion Complexes with a Wide Range of Topologies

“…rings pertaining to adjacent ring columns, [centroidcentroid distance, 3.9175(17) Å; dihedral angle, 18.95(14)°] and a clear CH(terpy)O(nitrate) interaction extending the association of the metallacycles. Here also, the KPI of 0.60 indicates the presence of voids occupied by disordered solvent molecules.Complexes 1 and 2 belong to the rather restricted family of uranyl-based metallacycles, with known examples involving (2R,3R,4S,5S)-tetrahydrofurantetracarboxylate,51 Kemp's tricarboxylate,52,53 1,3-adamantanediacetate,…”

Chain, Network and Framework Formation in Uranyl Ion Complexes with 1,1′‐Biphenyl‐3,3′,4,4′‐Tetracarboxylate

“…The complex [Co(en) 3 ][UO 2 (bptc)(HCOO)] • 2.5H 2 O (1) involves a counterion known to be an efficient hydrogen bond donor [21] and which has proven to be an efficient structure-directing species in uranyl complexes. [22][23][24][25] As noted above, the bptc 4À ligand is effectively a bis(phthalate) species and thus would be expected to form a 7-membered chelate ring at each phthalatelike site. This, in fact, is what is observed but, unlike most other known phthalate complexes, there are no other interactions of the oxygen donors with the metal cation.…”

“…The non-involvement of four oxygen atoms in bptc 4À and one in formate in coordination severely limits the periodicity of the coordination polymer, which is a zigzag chain parallel to [010] having a marked S-shape when viewed end-on. This undulating form defines gaps which, somewhat like the cavities found in a Kemp's tricarboxylate complex where the same countercation is present, [25] are approached from both sides by cations forming NH•••O bonds. The cation is present in its lel 2 ob conformation, [26] again as found in the Kemp's tricarboxylate complex, and all 12 amino group protons are involved in 15 NH•••O bonding interactions, some of them bifurcated, with two pairs of protons being bridged by water molecules and the others interacting with both bptc 4À In particular, two protons of type C 3 (i. e. such that the CÀ H bond is nearly parallel to the pseudo-C 3 axis of the anion) form three hydrogen bonds with the formate ligand, possibly explaining the rather unusual monodentate nature of the latter (less than one third of all uranyl formate species reported in the Cambridge Structural Database (CSD, version 5.42 [27] ) are neither chelating, nor bridging).…”

“…[38] There are 90 cases of 7-membered rings reported in the CSD, which involve, for example, citrate, [37] phthalate, [39] 4,4'-(1,1,1,3,3,3-hexafluoroisopropylidene)diphthalate [40] and 1,2cyclohexanedicarboxylates. [41] Larger, 8-membered rings are known with citrate [42] and Kemp's tricarboxylate, [25,43] and 9membered rings are found with 2,2'-bipyridine-3,3'dicarboxylate, [44] 1,1'-biphenyl-2,2'-dicarboxylate, [14] and 1,1'-biphenyl-2,2',6,6'-tetracarboxylate. [18] 7-Membered ring formation is present in all complexes 1-3, and it is the only coordination mode found in 1, in which two such rings are found in the equatorial plane of the uranyl ion, but this is at variance with previously reported uranyl ion complexes with this ligand, in which the only 7-membered ring involves Ag I and not U VI .…”