Synthesis of an Iron(IV) Aqua-Oxido Complex Using Ozone as an Oxidant.

The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclo-tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2 O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of FeIV oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of δ=0.19 mm s-1 and a quadrupole splitting ΔEQ =1.38 mm s-1 , confirming the high-valent FeIV state. DFT calculations were performed and led to an assignment of triplet spin multiplicity. Crystallographic characterization of [(H2 O)(tmc)Fe=O)](OTf)2 as well as of starting materials [(tmc)Fe(CH3 CN)](OTf)2 and [(tmc)Fe(OTf)]OTf together with previous results strongly suggest that [(H2 O)(tmc)Fe=O)](OTf)2 was formed similar to the oxido-hydroxido tautomerism analogous to heme systems.

Anticancer activity of a series of copper(II) complexes with tripodal ligands.

A series of copper(II) complexes with tripodal polypyridylamine ligands (derived from the parent ligand tris(2-pyridylmethyl)amine, tmpa) has been synthesized. Crystallographic characterization was possible for all complexes obtained. The copper(II) chloride complexes were investigated for their in vitro anticancer potential using human tumor cell lines containing examples of cervical, colon, ovarian cancers and melanoma. Some compounds showed a similar activity compared to that of cisplatin, however no systematic behavior could be observed.

Copper Chloride Catalysis: Do µ4-Oxido Copper Clusters Play a Significant Role?

Copper chloride catalysis is a well-established field in organic and inorganic chemistry. However, in most cases a detailed mechanistic understanding of the individual reaction steps and identification of reactive intermediates are still missing. The present study reports the results of spectroscopic and spectrometric measurements that support formation of copper agglomerates during catalytic processes. The composition of CuCl2·2H2O in several coordinating solvents and the influence of basic coreagents such as NaO(t)Bu and K2CO3 on the structure in the solid state as well as in solution were investigated. Several experiments involving crystal structure determination, IR spectroscopy, and ultra-high-resolution cryospray-ionization mass spectrometry were performed. The crystal structures of [CuCl2(H2O)]·0.5(CH3)2CO (1), [Cu2(CH3CN)2Cl4] (2), [Cu3(CH3CN)3Cl6] (3), [Cu3Cl6(THF)4] (4), [Cu(DMSO)2Cl2] (5), (H2N(CH3)2)2[CuCl3] (6), and [Cu4OCl6(THF)(urea)3]·3THF·urea (8) are reported herein. It can be clearly demonstrated that µ4-oxido copper clusters of the formula [Cu4OCl6(solvent)4] are the main product from the reactions of CuCl2·2H2O and basic coreagents. As a final result of these experiments, it can be stated that µ4-oxido copper clusters most likely play an important role in the mechanism of copper chloride-catalyzed reactions.

Fluoride-assisted activation of calcium carbide: a simple method for the ethynylation of aldehydes and ketones.

The fluoride-assisted ethynylation of ketones and aldehydes is described using commercially available calcium carbide with typically 5 mol % of TBAF·3H2O as the catalyst in DMSO. Activation of calcium carbide by fluoride is thought to generate an acetylide "ate"-complex that readily adds to carbonyl groups. Aliphatic aldehydes and ketones generally provide high yields, whereas aromatic carbonyls afford propargylic alcohols with moderate to good yields. The use of calcium carbide as a safe acetylide ion source along with economic amounts of TBAF·3H2O make this procedure a cheap and operationally simple method for the preparation of propargylic alcohols.

Reactions of copper(II) chloride in solution: facile formation of tetranuclear copper clusters and other complexes that are relevant in catalytic redox processes.

Mixing CuCl2⋅2 H2O with benzylamine in alcoholic solutions led to an extremely colorful chemistry caused by the formation of a large number of different complexes. Many of these different species could be structurally characterized. These include relatively simple compounds such as [Cu(L(1))4Cl2] (L(1) = benzylamine) and (HL(1))2[CuCl4]. Most interestingly is the easy formation of two cluster complexes, one based on two cluster units Cu4OCl6(L(1))4 connected through one [Cu(L(1))2Cl2] complex and one based on a cubane-type cluster ([Cu4O4](C11H14)4Cl4). Both clusters proved to be highly reactive in a series of oxidation reactions of organic substrates by using air or peroxides as oxidants. Furthermore, it was possible to isolate and structurally characterize ([Cu(L(1))Cl]3 and [Cu(benz2mpa)2]CuCl2 (benz2mpa = benzyl-(2-benzylimino-1-methyl-propylidene)-amine), two copper(I) complexes that formed in solution, demonstrating the high redox activity of the cluster systems. In addition, it was possible to solve the molecular structures of the compounds Cu4OCl6(MeOH)4, [Cu(MeOH)2Cl2], [Cu(aniline)2Cl2], and an organic side product (HC13 H19 NOCl). In fact all determined structures are of a known type but the chemical relation between these compounds could be explained for the first time. The paper describes these different compounds and their chemical equilibria. Some of these complexes seem to be relevant in catalytic oxidation reactions and their reactivity is discussed in more detail.