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The synthesis and spectroscopic characterisation of a series of homoleptic complexes of the tridentate pyridine‐2,6‐di(5‐tetrazolate) ligand (pydtz2–) with CoII, NiII, CuII and ZnII are reported. Single‐crystal XRD data reveals the formation of octahedrally configured complexes [M(pydtz)2]2– for M = Zn or [M(Hpydtz)(pydtz)]– for M = Co or Ni, whereas for M = Cu a polymeric structure [Cu(pydtz)(EtOH)]n crystallised. In the latter, alternate short and long Cu···Cu distances were found. Magnetic measurements and electron paramagnetic resonance (EPR) spectroscopy reveal noncoupled S = 1/2 CuII ions for [Cu(pydtz)(EtOH)]n, S = 1/2 low‐spin configuration for the CoII complex and an S = 1 ground state for the NiII derivative. At T < 16 K the latter shows anomalies that resemble those of single‐ion molecular magnets. The ligand strength of pydtz2– is markedly higher than that of the bioisosteric pyridine‐2,6‐dicarboxylate (pydic2–) ligand and is very similar to that of the well‐established 2,2′:6′,2″‐terpyridine (terpy) ligand as revealed by the ligand field bands of the Co, Ni and Cu complexes and the magnetism of the Co and Ni derivatives. Solution electrochemical investigations suggest that essentially ligand‐centred reduction at rather negative potentials and metal‐centred oxidation processes occur.

The synthesis, spectroscopy, structures and chemical reactivity of platinum(II) diolefin complexes cis‐[(∥∧∥)PtCl2], cis‐[(∥∧∥)PtCl(R)] and cis‐[(∥∧∥)Pt(R)2] [∥∧∥ = chelate diolefin ligand: 1,5‐cyclooctadiene (COD), 1,5‐dimethylocta‐1,5‐diene (Me2COD), norbornadiene (NBD), 1,5‐hexadiene (HEX), 3‐allyloxypropene (All2O, diallyl ether), diallylamine (All2NH); R = Me, Bn, C6F5, C6F4H‐4 (or ‐5), or C≡C(4‐Me)Ph] have been explored. The relative exchange rates of the cis‐[(∥∧∥)PtCl2] complexes towards the diimine ligand diisopropyl‐1,4‐diazabutadiene (iPr‐DAB) increased along the series COD < Me2COD < NBD < HEX < All2O by a factor of 4. The presumably dimeric complex [(All2NH)PtCl2]2 undergoes a unique rearrangement process in dimethyl sulfoxide (DMSO) solution to yield the dimeric piperazine complex [PtCl(dmso)(C6H10N)]2, which has been characterised by single‐crystal XRD. For selected platinum complexes, cytotoxic effects in HT‐29 colon carcinoma and MCF‐7 breast cancer cell lines were evaluated. For comparison, the dicationic complexes [(COD)Pt(Bn)(L)][PF6]2 with the very labile coligands N‐methyl‐4,4′‐bipyridinium (MQ+) and N‐methyl‐1,4‐pyrazinium (Mpz+) were added to the study. Although the hexadiene complexes [(HEX)Pt(C6F4H‐4)2] and [(HEX)Pt(C6F4H‐5)2] show strong cytotoxicity, the introduction of labile diolefin ligands or the labile cationic MQ+ or Mpz+ coligands does not generally lead to markedly increased cytotoxicity.

The chemical composition of a black powder confiscated by German customs was elucidated. Black powders are occasionally used as a 'transporter' for cocaine and are obviously especially designed to cloak the presence of the drug. The material consisting of cocaine, copper, iron, thiocyanate, and graphite was approached by analytical tools and chemical modelling. Graphite is added to the material probably with the intention of masking the typical infrared (IR) fingerprints of cocaine and can be clearly detected by powder X-ray diffraction (XRD) and Raman spectroscopy. Cu(2+) and NCS(-) ions, when carefully reacted with cocaine hydrochloride, form the novel compound (CocH)2 [Cu(NCS)4 ] (CocH(+)  = protonated cocaine), which has been characterised by single crystal XRD, IR, NMR, UV/Vis absorption and EPR spectroscopy. Based on some further experiments the assumed composition of the original black powder is discussed.

The five coordinate organoplatinum complex [Pt(bpy)(cod)(Me)][SbF6] (cod = 1,5-cyclooctadiene, bpy = 2,2'-bipyridine) was obtained reacting [Pt(cod)(Me)Cl] with Ag[SbF6] and bpy and characterized by multiple spectroscopy (IR and NMR) and single crystal XRD. Although the application of the τ values for the discrimination between trigonal bipyramidal vs. square pyramidal coordination fails, the molecular structure can be unequivocally described as basally-distorted trigonal bipyramidal. Detailed multinuclear NMR spectroscopy in solution at ambient temperature gives strong evidence for the same structure; corresponding low-temperature measurements down to −70 °C revealed no marked dynamic processes.

The synthesis and spectroscopic characterisation of a series of heteroleptic complexes of the tridentate pyridine-2,6-di-(5-tetrazolate) (pydtz(2-)) with Co(II), Ni(II), Cu(II) and Zn(II) and pyridine (Py) and H2O as coligands is reported. Single crystal XRD data reveals the formation of octahedrally configured complexes [Co(pydtz)(H2O)(Py)(2)], [Co(pydtz)(H2O)(2)(Py)]2H(2)O, [Ni(pydtz)(Py)(3)]2Py, and [Zn(pydtz)(H2O)(Py)(2)]Py, and a markedly Jahn-Teller distorted octahedral structure for [Cu(pydtz)(H2O)(2)(Py)]. Magnetic measurements reveal a S = 3/2 high-spin configuration for the Co(II) complex [Co(pydtz)(H2O)(Py)(2)], an S = 1 ground state for the Ni(II) derivative and S = 1/2 Cu(II) ions for [Cu(pydtz)(H2O)(2)(Py)], the latter is supported by electron-paramagnetic-resonance spectroscopy. The crystalline materials are subject to severe corrosion as revealed by powder XRD and DSC-TG experiments. H2O and pyridine co-crystallisates and coligands are easily cleaved. At the same time DSC-TG reveal very high stability of the [M(pydtz)] fragments with exothermic decomposition at T > 300 degrees C. As a consequence, in pyridine solution in all cases the species [M(pydtz)(Py)(3)] are observed. Ultraviolet-visible light absorption spectroscopy reveals a strong ligand field procured by the pydtz(2-) ligand and electrochemical measurements suggest very strong sigma-donation but only weak -accepting abilities of pydtz(2-) compared to the isostructural terpy (2,2';6',2''-terpyridine) ligand

Tetranuclear complexes [M 4 (L R) 4 ] with M = Ni(II) or Zn(II), with a [2 × 2] grid-type structure, were assembled in good yields and purity from the easily accessible but unprecedented pyrazine-bridged bis(thiosemicarbazone) protoligands (ligand precursors) H 2 L R (1,4-pyrazine-2,5bis(R-carbaldehyde-thiosemicarbazone); R = Me, Et, i Pr, or Ph). The complexes were characterised in solution by NMR, MS, IR, and UV-Vis absorption spectroscopy and (spectro)electrochemical methods. HR-MS spectra unequivocally reveal that the tetranuclear species are very stable in solution and any measurements represent these species. Only at higher temperatures (fragmentation in solution: MS and in the solid: TG-DTA) or upon the addition of protons (acidic UV-Vis titrations) can the tetrameric entities be decomposed. Single crystal XRD measurement remained preliminary. Rapid loss of co-crystallised solvent molecules within the [2 × 2] grid-type structures resulted in crystals of very poor quality, but the results were qualitatively in line with spectroscopy, electrochemistry, and quantum chemical (DFT) calculations. IR and NMR spectroscopy point clearly to a thiolate coordination of dianionic (deprotonated) ligands. The electrochemistry reveals four electronically coupled and reversible one-electron reductions centred largely at the pyrazine bridges. EPR and UV-Vis spectroelectrochemical measurements in combination with DFT calculation support the assignment.

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