Georg Seeber

The Missing Link in Low Nuclearity Pure Polyoxovanadate Clusters: Preliminary Synthesis and Structural Analysis of a New {V16} Cluster and Related Products

Two new metastable polyoxovanadate-based cluster compounds have been isolated and crystallographically characterized with nuclearities of {V16} (1) and {V18} (2). The {V16} cluster represents a new framework type and incorporates two protons into the cluster framework whereas the {V18} framework has been previously characterised, and the oxidation states of the {V18} cluster can be assigned as {VIV15VV3}. Compound K10[H2V16O38]⋅13H2O (1) crystallizes in the monoclinic space group P21/c, a=12.12820(10), b=38.2302(3), c=12.35400(10) Å, β=115.0470(10)°, V=5189.43(7) Å3, Dc=2.624 g⋅cm−3. 10086 unique reflection and 702 refined parameters were used in structure refinement. R1=0.039, R2=0.109 (all data). From the same preparation the new compound K11[V18O42(SO4)]⋅20H2O (2) was also isolated and crystallographically characterized. Compound 2 crystallizes in the monoclinic space group P21/n, a=12.7854(3), b=20.2812(5), c=13.2386(4) Å, β=115.3400(10)°, V=3102.53(14) Å3, Dc=2.650 g⋅cm−3. 7115 unique reflections and 462 refined parameters were used in structure refinement. R1=0.046, R2=0.121 (all data).

Supramolecular assembly of ligand-directed triangular {CuII3Cl} clusters with spin frustration and spin-chain behaviour

Triangular [Cu(II)3Cl] clusters, containing a chloro ligand in an unprecedented trigonal planar coordination mode, are assembled in a 3-D array by the combination of coordinative and hydrogen-bonded interactions, which result in magnetically isolated 1-D chains exhibiting a combination of spin frustration and spin-chain behaviour.

The importance of π–π, π–CH and N–CH interactions in the crystal packing of Schiff-base derivatives of cis,cis- and cis,trans-1,3,5-triaminocyclohexane

The crystal structures of cis,trans-1,3,5-tris-benzaldimino-cyclohexane (trans-tbc, 1), cis,trans-1,3,5-tris-(pyridine-2-carboxaldimino)-cyclohexane (trans-ttop, 2), cis,cis-1,3,5-tris-(pyridine-3-carboxaldimino)-cyclohexane (cis-mttop, 3) and cis,trans-1,3,5-tris-(pyridine-4-carboxaldimino)-cyclohexane (trans-pttop, 4) are reported. The arrangements of the molecules forming the packed arrays are controlled by the interplay of several different weak intermolecular interactions: π–π stacking, C–H⋯π and C–H⋯N interactions, and these are in turn related to differences in the stereochemistry around the cyclohexane backbone, as well as the positioning of the pyridyl–nitrogen to determine the overall supramolecular arrangement of these molecules in the solid state.

Palladium(II)-based cis,trans-1,3,5-triaminocyclohexane complexes demonstrating a variety of coordination modes and architectures

The reaction of cis,trans-1,3,5-triaminocyclohexane·3HX (L·3HX) with PdX2 (X = Br, Cl) affords a wide range of coordination complexes that represent the different coordination modes available to L. Monoligand complexes [Pd(LH)Cl2]Cl (1) and [Pd(LH)Br2]2[PdBr4] (2) demonstrate the bidentate coordination of L with the two cis amino ‘head’ groups chelating the palladium(II) ion and the third trans amino ‘tail’ group being protonated. Diligand complexes [Pd(LH)2]X (X = (NO3)43, (SO4)24) show a ‘head-to-head’ coordination mode with the protonated trans amino groups adopting a conformation that positions them opposite to each other. Both sets of amino groups are engaged in coordination in a cyclic ‘head-to-tail’ fashion found in the hexanuclear ring clusters [{Pd(L)X}6]X6 (X = Cl 5, Br 6). 5 and 6 are isostructural, both in the solid state and in solution, despite accommodating six chloro or bromo ligands into the cluster framework. A trinuclear complex [Pd{Pd(L)Cl2}2Cl2] (7) reveals ‘tail-to-tail’ coordination of two ligands for the centre palladium(II) ion in addition to their ‘head’ amino groups individually chelating other palladium(II) ions. Complexes 1–7 were characterised by single-crystal X-ray diffraction, elemental analysis, IR and by NMR spectroscopy (1–6).

Supramolecular Architectures of Copper(II) Perchlorate Complexes of cis,trans-1,3,5-Triaminocyclohexane Assembled Exploiting the Delicate Balance Between Weak and Strong Interactions

The complexation of copper(II) perchlorate with cis,trans-1,3,5-triamino-cyclohexane (transtachH) yields four related mononuclear complexes, [Cu(trans-tachH)2](ClO4)4・(H2O) (1), [Cu(transtachH) 2](ClO4)4・2MeOH (2), [Cu(trans-tachH)2(ClO4)](ClO4)3 (3) and [Cu(trans-tach)(transtachH)( ClO4)2](ClO4)・H2O (4). These complexes only differ with respect to ligand protonation, solvent coordination / content, and counterion binding, yet these small differences manifest as vast differences in the supramolecular structures, and we also show that certain crystalline phases of these four compounds persist for different lengths of time in the mother liquor. Graphical Abstract Supramolecular Architectures of Copper(II) Perchlorate Complexes of cis,trans-1,3,5-Triaminocyclohexane Assembled Exploiting the Delicate Balance Between Weak and Strong Interactions

Polymeric silver(I) coordination tubes

Isolated polymeric Ag(I) coordination tubes are self-assembled from the rigid triamino ligands cis,cis-1,3,5-triaminocyclohexane (cis-tach) and cis,trans-1,3,5-triaminocyclohexane (trans-tach), forming two topologically equivalent framework motifs.

Self-assembly of a twelve-component hexanuclear metallomacrocycle constructed with a novel tri-amino ligand

Reaction of the novel ligand cis,trans-1,3,5-triaminocyclohexane, which contains two types of metal binding sites trans to each other, with palladium(II) chloride results in the self assembly of a hexanuclear ring cluster that has been characterised both in the solid state and in solution.