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The ligand class of tridentate bis(pyrazolyl)methanes was extended via the syntheses of HC(3,5-EtPz)(2)Py. This ligand is the first of its kind with a homogeneous 3,5-functionalization with large substituents. On the basis of 3,5-functionalized ligands we were able to synthesize 15 novel complexes with Fe-II, Zn-II, and Cu-II salts. Herein we present an extensive coordination chemistry study, that focuses on the influences of different metals, ligands, and counterions on the coordination mode and on the spin state in case of Fe-II complexes.

Heteroscorpionate ligands of the bis(pyrazolyl)methane family have been applied in the stabilisation of terminal copper tosyl nitrenes. These species are highly active intermediates in the copper-catalysed direct C-H amination and nitrene transfer. Novel perfluoroalkyl-pyrazolyl- and pyridinyl-containing ligands were synthesized to coordinate to a reactive copper nitrene centre. Four distinct copper tosyl nitrenes were prepared at low temperatures by the reaction with SO(2)tBuPhINTs and copper(I) acetonitrile complexes. Their stoichiometric reactivity has been elucidated regarding the imination of phosphines and the aziridination of styrenes. The formation and thermal decay of the copper nitrenes were investigated by UV/Vis spectroscopy of the highly coloured species. Additionally, the compounds were studied by cryo-UHR-ESI mass spectrometry and DFT calculations. In addition, a mild catalytic procedure has been developed where the copper nitrene precursors enable the C-H amination of cyclohexane and toluene and the aziridination of styrenes.

European journal of organic chemistry 2019(37), 6341-6346 (2019). doi:10.1002/ejoc.201900904, Published by Wiley-VCH Verl., Weinheim

Copper-poly(pyrazolyl)methane complexes have been proven to be highly useful in a variety of catalytic organic transformations. A multitude of poly(pyrazolyl)methane ligands have been developed for this effort and are summarized in this work. Their tailored electronic properties and steric hindrance are easily modified, demonstrating their diversity and high potential as spectator ligands for copper catalysis. The listed examples of organic reactions range from cycloadditions to nitrene transfer and bioinorganic monooxygenase chemistry. 1 Introduction 2 Cycloadditions of Azides and Alkynes 3 Copper-Mediated Nitrene and Carbene Transfer 4 Csp–Csp2, C–N and C–S Cross-Coupling Reactions 5 Copper–Tpm-Catalyzed Aldol Reactions 6 A Bpm Ligand for the Polymerization of Methyl Methacrylate 7 Copper-Catalyzed Oxidations 8 Concluding Remarks

A series of bis(pyrazolyl)methane copper complexes were found to catalyze a fast palladium-free Sonogashira coupling reaction of several iodoarenes with terminal alkynes such as phenylacetylene, propargyl benzyl ether, and (tert-butyl-dimethyl)silylacetylene. These reactions proceed with CuCl2·2H2O (10 mol-%) under aerobic conditions and the corresponding chelate ligand (10 mol-%), with its tailored facial coordination mode, is crucial for the success of the reaction. The coupling can also be carried out in water with liquid aryl halides and a phase-transfer catalyst.