The occurrence of crystalline intermediates in mechanochemical reactions may be more widespread than previously assumed. For example, a recent study involving the acetate‐assisted C–H activation of N‐heterocycles with [Cp*RhCl2]2 by ball milling revealed the formation of transient cocrystals between the reagents prior to the C–H activation step. However, such crystalline intermediates were only observed through stepwise intervallic ex situ analysis and their exact role in the C–H activation process remained unclear. In the present study, we monitored the formation of discrete, stoichiometric cocrystals between benzo[h]quinoline and [Cp*RhCl2]2 by ball milling using in situ synchrotron X‐ray powder diffraction. This continuous analysis revealed an initial cocrystal that transformed into a second crystalline form. Computational studies showed that differences in non‐covalent interactions made the [Cp*RhCl2]2 unit in the later‐appearing cocrystal more reactive towards reaction with NaOAc. This demonstrated the advantage of cocrystal formation before the acetate‐assisted metalation‐deprotonation step and evidence how the net cooperative action of weak interactions between the reagents in mechanochemical experiments can lead to stable supramolecular assemblies, which can enhance substrate activation under ball milling conditions. This could explain the superiority of some mechanochemical reactions, such as acetate‐assisted C–H activation, compared to their solution‐based counterparts.

Hybrid metal-organic compounds as relatively new and prosperous magnetoelectric multiferroics provide opportunities to improve the polarization, magnetization and magneto-electric coupling at the same time, which usually have some limitations in the common type-I and type-II multiferroics. In this work we investigate the crystal of guanidinium copper (II) formate [C(NH2)3]Cu(HCOO)3 and give novel insights concerning the structure, magnetic, electric and magneto-electric behaviour of this interesting material. Detailed analysis of crystal structure at 100 K is given. Magnetization points to the copper (II) formate spin-chain phase that becomes ordered below 4.6 K into the canted antiferromagnetic (AFM) state, as a result of super-exchange interaction over different formate bridges. The performed ab-initio colinear density functional theory (DFT) calculation confirm the AFM-like ground state as a first approximation and explain the coupling of spin-chains into the AFM ordered lattice. In versatile measurements of magnetization of a crystal, including transverse component besides the longitudinal one, very large anisotropy is found that might originate from canting of the coordination octahedra around copper (II) in cooperation with the canted AFM order. With cooling down in zero fields the generation of spontaneous polarization is observed step-wise below 270 K and 210 K and the effect of magnetic field on its value is observed also in the paramagnetic phase. Measured polarization is somewhat smaller than the DFT value in the c-direction, possibly due to twin domains present in the crystal. The considerable magneto-electric coupling below the magnetic transition temperature is measured with different orientations of the crystal in magnetic field, giving altogether the new light onto the magneto-electric effect in this material.

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In this work, we explore the halogen-bonded cocrystallization potential of cobaloxime complexes in the synthesis of cocrystals with perhalogenated benzenes. We demonstrate a strategy for synthesizing halogen-bonded metal–organic cocrystals by utilizing cobaloximes whose pendant bromide group and oxime oxygen enable halogen bonding. By combining three well-known halogen bond donor molecules differing in binding geometry and composition with three cobaloxime units, we obtained a total of four previously unreported cocrystals. Single crystal X-ray diffraction experiments showed that the majority of obtained cocrystals exhibited the formation of the targeted I···O and I···Br motives. These results illustrate the potential of cobaloximes as halogen bond acceptors and indicate that this type of halogen bond acceptors may offer a novel route to metal–organic halogen-bonded cocrystals.

Discrete and polymeric ensembles based on dimolybdenum(vi) units with adaptive carbohydrazide ligands are described. The polymeric complexes are efficient catalysts for cyclooctene epoxidation under eco-friendly conditions.