Tris-(2-hydroxybenzylidene)triaminoguanidinium salts having six alkyl chains with proper spacing served as new molecular building blocks for the formation of porous honeycomb networks by van der Waals interaction between interdigitated alkyl chains at the liquid/graphite interfaces.

The crystal structures of 5,10,15,20-tetra(4-hydroxyphenyl)-21,23H-porphyrin nitrobenzene hexasolvate (1), 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatonickel(II) nitrobenzene hexasolvate (2) and 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatocopper(II) nitrobenzene hexasolvate (3) are described. Compounds 1–3 crystallise isomorphously in the non-centrosymmetric tetragonal space group P4cc with Z = 8. There are three crystallographically distinct porphyrin molecules, two of which contain fourfold axes perpendicular to the porphyrin plane. The remaining one contains a twofold axis perpendicular to the porphyrin ring system. The porphyrin building blocks are joined into a three-dimensional network through self-complementary O–H⋯O hydrogen bonding interactions between 4-hydroxyphenyl groups of adjacent molecules. The space occupied by the nitrobenzene solvent molecules is remarkably large at ca. 61.5% of the unit cell volume in 1–3.

A three-part experiment that leads to the synthesis of palladium(II) complex starting from a C3-symmetric triaminoguanidinium-based ligand is presented. In the first part, the preparation of tris-benzylidenetriaminoguanidinium chloride ([H6Br3L]Cl) by an acidic catalyzed 3-fold imine formation reaction of 5-bromo-2-hydroxybenzaldehyde and triaminoguanidinium chloride is described. Starting from the second part, the reaction procedures are performed under inert gas atmosphere. The conversion of PdCl2 with acetonitrile to give [Pd(MeCN)4]Cl2 as a precursor is performed at 80 °C. The third part of the experiment is a three-step procedure that begins with deprotonation of [H6Br3L]Cl, followed by transfer of [Pd(MeCN)4]Cl2 to the reaction flask, where the chelation of Pd(II)-precursor leads to the in situ species [Pd(MeCN)H3Br3L]. Addition of PPh3 as the final reaction step yields [Pd(PPh3)H3Br3L]. This sequence of experiments provides an excellent example of ligand and transition metal preparation and its subsequent complexation to form an oxidant-sensitive organometallic species. Undergraduate students get the opportunity to learn Schlenk techniques and to investigate 1H NMR spectra of organic and organometallic compounds starting from relatively simple to more advanced spectra. The distinct result of the chemical shift of the 4JP–H-affected doublet mirrors the preparative success of the student and demonstrates the utility of 1H NMR experiments.Keywords: Analytical Chemistry; Inorganic Chemistry; Inquiry-Based/Discovery Learning; Interdisciplinary/Multidisciplinary; NMR Spectroscopy; Organometallics; Oxidation/Reduction; Second-Year Undergraduate;

C 3 -symmetric ligands carrying a rigid triaminoguanidinium backbone are important building blocks for the preparation of supramolecular coordination cages as tetrahedra or trigonal bipyramides. Coordination of Eu(III)- or Gd(III)-ions leads to 1,2,4-triazole formation, which has been reported only rarely. Using Pd(II)-complexes as a model system, this triazole formation could be analyzed in more detail. The preparation of Pd(II)-coordination compounds can be easily done under stoichiometric control. These complexes could be transformed into 1,2,4-triazoles using O2 or H2O2 as an oxidation reagent. The steric demand of the PR3-coligand seems to play a key role in the cyclisation reaction.

The crystal structure of [ZnBr2(μ-dtdp)]n (1) (dtdp = 4,4’-dithiodipyridine) is described. Compound 1 is a one-dimensional coordination polymer of the arched chain type, composed of ZnBr2 units as tetrahedral metal nodes joined by the bent bridging ligand dtdp. 1 was found to crystallise in the monoclinic space group C2/c with the lattice parameters a = 12.713(4) Å, b = 10.108(4) Å, c = 10.835(5) Å, β = 91.21(3)°, V = 1392.0(9) Å3. In the crystal, the coordination polymer strands run parallel to the c axis direction with the ZnBr2 units and disulfide bridges containing crystallographic twofold rotation axes. The structure of 1 belongs to an isomorphous series of [ZnX2(μ-dtdp)]n (X = Cl−, SCN−, CH3COO−) coordination polymers, which can be found in the literature. The crystal of 1 studied was found to be a two component non-merohedral twin with the twin operation representing a twofold rotation about the c axis, as for the isostructural chlorido derivative [Seidel RW, Dietz C, Oppel IM (2012) Z Kristallogr NCS 227:305].

Reaction of Zn(NO3)2·6H2O with the bent bridging ligand 4,4′-dithiodipyridine (dtdp), showing axial chirality, in the presence of the chelating 1,10-phenanthroline (phen) ligand in ethanol yielded [{Zn(μ-dtdp)2(H2O)2}(NO3)2·2C2H5OH·2H2O]n (1). In 1, Zn2+ ions are linked by two dtdp ligands of opposite chirality into a one-dimensional coordination polymer of the repeated-rhomboid type; the phen co-ligand was not encountered in the crystal. Pseudo-symmetry of the lattice is discussed for 1. Reaction of Zn(NO3)2·6H2O and dtdp in an ethanol/water mixture in absence of phen led to the known repeated-rhomboid coordination polymer [{Zn(NO3)(μ-dtdp)2(H2O)}NO3·4H2O]n (2), the crystal structure of which was redetermined at 110 K. At low temperature, the nitrato-κO ligand in one axial position of Zn2+ was found to be non-disordered as distinct from the room temperature structure (Horikoshi and Mikuriya, Cryst Growth Des 5:223–230, 2005). The Zn2+ ions in 2 are joined by two dtdp ligands of the same chirality.

Tris-(2-hydroxybenzylidene)triaminoguanidinium salts having six alkyl chains with proper spacing served as new molecular building blocks for the formation of porous honeycomb networks by van der Waals interaction between interdigitated alkyl chains at the liquid/graphite interfaces.

C 3 -symmetric ligands carrying a rigid triaminoguanidinium backbone are important building blocks for the preparation of supramolecular coordination cages as tetrahedra or trigonal bipyramides. Coordination of Eu(III)- or Gd(III)-ions leads to 1,2,4-triazole formation, which has been reported only rarely. Using Pd(II)-complexes as a model system, this triazole formation could be analyzed in more detail. The preparation of Pd(II)-coordination compounds can be easily done under stoichiometric control. These complexes could be transformed into 1,2,4-triazoles using O2 or H2O2 as an oxidation reagent. The steric demand of the PR3-coligand seems to play a key role in the cyclisation reaction.