The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N-N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo-N -Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N-N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation.

Low-valent osmium nitrides are discussed as intermediates in nitrogen fixation schemes. However, rational synthetic routes that lead to isolable examples are currently unknown. Here, the synthesis of the square-planar osmium(IV) nitride [OsN(PNP)] (PNP=N(CH2 CH2 P(tBu)2 )2 ) is reported upon reversible deprotonation of osmium(VI) hydride [Os(N)H(PNP)](+) . The Os(IV) complex shows ambiphilic nitride reactivity with SiMe3 Br and PMe3 , respectively. Importantly, the hydrogenolysis with H2 gives ammonia and the polyhydride complex [OsH4 (HPNP)] in 80 % yield. Hence, our results directly demonstrate the role of low-valent osmium nitrides and of heterolytic H2 activation for ammonia synthesis with H2 under basic conditions.

An iridium(iii–v) imido series has been isolated that features an iridium complex with an unprecedented triplet ground state.

A new series of [Pd2(L)4] cages based on photochromic dithienylethene (DTE) ligands allowed us to gain insight into the successive photoswitching of multiple DTE moieties in a confined metallo‐supramolecular assembly. Three new X‐ray structures of [Pd2(o‐L4)4], [Pd2(o‐L1)2(c‐L1)2] and [Pd2(c‐L1)4] (o‐L and c‐L = open and closed forms of DTE ligands, respectively) were obtained. The structures deliver snapshots of three different combinations of DTE photoisomeric states within the cage, facilitating a comparison of the all‐open with the all‐closed, and most notably, an intermediate form where open and closed switches co‐exist in the same cage. Moreover, a series of spherical anionic borate clusters was introduced in order to study their roles in the light‐controllable host–guest chemistry. The binding guests show higher affinities with the flexible open cage [Pd2(o‐L1)4] than with the rigid closed cage [Pd2(c‐L1)4]. For the [B12F12]2− guest, thermodynamic data obtained from NMR experiments was compared to results from isothermal titration calorimetry (ITC).