Hydrogen–deuterium exchange (H/D exchange) is a method commonly used for studying catalytic activation of C–H(D) bonds by transition metal complexes. In this study, a series of additives were studied for H/D exchange of toluene-d₈ with acetic acid (HOAc) using (^RPNP)Rh(X) complexes (R = phosphine substituents including cyclohexyl, isopropyl, and tert-butyl; X = trifluoroacetate or acetate) as the precatalysts. Cu(OAc)₂ and AgOAc additives were found to benefit Rh-mediated C–H(D) activation of toluene with meta–para selectivity by facilitating the conversion to active (^RPNP)Rh species and stabilizing the Rh catalysts from decomposition to inactive Rh(s). In contrast, nonoxidizing Lewis acid additives, such as B(OMe)₃ or NaOAc, were not effective at facilitating Rh-catalyzed toluene C–H activation. The complexes (^RPNP)Rh^III(H)(X)₂ and [(^RPNP)Rh^I(CO)][X] (X = TFA or OAc) were found to be intermediates of the catalytic the H/D exchange.

Herein, we describe the syntheses and structural characterization of bis(carbene)- and tris(carbene)-stabilized organomagnesium cations. The reaction of the N-heterocyclic carbene (NHC) stabilized Grignard reagent (^iPrNHC)₂Mg(Me)(Br) (1) and Na[BAr^F₄] (^iPrNHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, Ar^F = 3,5-bis(trifluoromethyl)phenyl) in chlorobenzene yields exclusively the bis(NHC)-stabilized dication [{(^iPrNHC)₂Mg}₂(μ-Me)₂][(BAr^F₄)₂] (2). If the reaction is performed in ethereal or nonpolar arene solvents, 2 undergoes Schlenk-type rearrangements to tris(NHC)-stabilized cations [(^iPrNHC)₃Mg(Me)][BAr^F₄] (3[BAr^F₄]) and [(^iPrNHC)₃Mg(Br)][BAr^F₄] (4[BAr^F₄]). These monomeric cations 3[A] and 4[A] (A = BAr^F₄, BPh₄) can be independently prepared as single pure products in high yields using common hydrocarbon solvents. The electronic influence of tris(carbene) stabilization is further evidenced by an NHC-mediated ionization of magnesium bromide in the absence of abstraction reagents. The reaction between the sterically unencumbered 1,3,4,5-tetramethylimidazol-2-ylidene (^MeNHC) ligand and (^MeNHC)₂MgBr₂ (7) resulted in two geometrically unique cations of the type [(^MeNHC)₃MgBr][Br]: complex 8a bearing a weakly coordinating bromide anion resulting in a trigonal bipyramidal magnesium center, and complex 8b bearing a noncoordinating bromide anion where the magnesium atom resides in a tetrahedral coordination environment. All isolated complexes were characterized by NMR spectroscopy and single-crystal X-ray diffraction, and their bonding was investigated by density functional theory (DFT).

Charge‐separated metal–organic frameworks (MOFs) are a unique class of MOFs that can possess added properties originating from the exposed ionic species. A new charge‐separated MOF, namely, UNM‐6 synthesized from a tetrahedral borate ligand and Co²⁺ cation is reported herein. UNM‐6 crystalizes into the highly symmetric P43n space group with fourfold interpenetration, despite the stoichiometric imbalance between the B and Co atoms, which also leads to loosely bound NO₃⁻ anions within the crystal structure. These NO₃⁻ ions can be quantitatively exchanged with various other anions, leading to Lewis acid (Co²⁺) and Lewis base (anions) pairs within the pores and potentially cooperative catalytic activities. For example, UNM‐6‐Br, the MOF after anion exchange with Br⁻ anions, displays high catalytic activity and stability in reactions of CO₂ chemical fixation into cyclic carbonates.