The reaction of 1,1,3,3-tetraphenyl-1,3-disiloxandiol (LH2) with n-butyllithium and CrCl2 results in a mononuclear chromium(II) complex (1) that further reacts with O2 at low temperatures to yield a mononuclear chromium(III) superoxide complex [L2CrO2(THF)][Li2(THF)3] (2). The crystal structure revealed that the chromium superoxido entity is stabilized by the coordination to an adjacent lithium cation. Complex 2 thus contains an unprecedented heterobimetallic [Cr(III)(μ-O2)Li(+)] core; beyond this it is the first chromium superoxide for which a temperature-dependent magnetic characterization could be achieved, and the first structurally characterized representative with chromium in an exclusive O-donor environment.

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CAAC–CAAC dimers with alkylene spacers are presented. These compounds are electron-rich and undergo one- and two-electron oxidation.

Syntheses of very electron‐rich dialkylamino‐substituted 2,2':6',2''‐terpyridines (TPYs) were adapted to moderate scale preparation without tedious purification of intermediates. The key 4'‐bromo‐6,6''‐dimethyl‐2,2':6',2''‐terpyridine‐4,4''‐diyl bisnonaflate is now available in gram quantities. Its nucleophilic aromatic substitution with dimethylamine provided mixtures of 4'‐bromo‐substituted 4,4''‐bis(dimethylamino)‐TPY and the tris(dimethylamino)‐TPY. The bromo compound was used in a Buchwald–Hartwig amination to provide the tris(dimethylamino)‐TPY in excellent yield. The 4'‐bromo substituent was reductively removed to furnish the bis(dimethylamino)‐TPY. The same sequence of reactions with pyrrolidine as nucleophile leads to the hitherto unknown pyrrolidino‐TPYs. Calculations at the MP2(FC)/6–31+G(2d,p)//B98/6‐31G(d) level predict very high methyl cation affinities for compounds of this type, with the 4,4',4''‐tri(pyrrolidin‐1‐yl)‐TPY being the most Lewis basic TPY synthesized to date. The efficiently prepared electron‐rich TPYs should be excellent ligands for many applications.

Metal–ligand cooperativity can be used in iridium complexes with an unsymmetrically substituted redox-active diamidobenzene ligand for bond activation reactions.

We have studied the effect of N-substitution on the course of the reaction of imidazolium triflate. The reaction of N-heterocyclic carbene with N-tBu-substituted pyrrolinium triflate afforded 2-(pyrrolidin-2-yl)-imidazolium triflate, 3 R . Treatment of 3 R with potassium bis(trimethylsilyl)amide (KHMDS) leads to either the dealkylation product 4 or the deprotonation product, triazaalkene 5, depending on the N-substitution at the imidazolium moiety. Density functional studies using the B3LYP/TZVP setup have been employed to explore various pathways for the dealkylation reaction and the calculated energies support the dealkylation by a large energy margin compared to the deprotonatation process. Theoretical calculations revealed that dealkylation reaction is thermodynamically more favorable than deprotonation. The triazaalkene 5 could be oxidized by AgOTf to the corresponding radical cation 6 and dication 7 in-situ. While 6 and 7 could not be isolated, the formation of the former is inferred by electron paramagnetic resonance spectroscopy and its abstraction of a H-atom to afford 3 Me . Similarly, the formation of the dication 7 is inferred by its ready elimination of isobutylene affording 8.

A series of dumbbell-shaped sec-ammonium salts with bulky (pseudo)stoppers (‘speed bumps’) were tested for their ability to form pseudorotaxanes with a redox-switchable, tetrathiafulvalene (TTF)-decorated [24]crown-8 ether. Depending on the size...

Diamidobenzene ligands are a prominent class of redox-active ligands owing to their electron reservoir behaviour, as well as the possibility of tuning the steric and the electronic properties of such...