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This report describes an isostructural series of dinuclear iron, cobalt, and nickel complexes bound by a redox-active macrocyclic ligand. The series spans five redox levels (34–38 e–/cluster core), allowing for a detailed investigation into both the degree of metal–metal interaction and the extent of ligand-based redox-activity. Magnetometry, electrochemistry, UV–vis–NIR absorption spectroscopy, and crystallography were used in conjunction with DFT computational analyses to extract the electronic structures of the six homodinuclear complexes. The isoelectronic, 34 e–species [(3PDI2)Fe2(PMe3)2(μ-Cl)](OTf) and [(3PDI2)Co2(PMe3)2(μ-Cl)](OTf)3exhibit metal–metal single bonds, with varying amounts of electron density delocalization into the ligand as a function of the effective nuclear charge of the metal ions. One- and two-electron reductions of [(3PDI2)Co2(PMe3)2(μ-Cl)](OTf)3lead to isolable products, which show successive increases in both the Co–Co distances and the extent of reduction of the ligand manifold. This trend results from reduction of a Co–Co σ* orbital, which was found to be heavily mixed with the redox-active manifold of the 3PDI2ligand. A similar trend was observed in the 37 and 38 e–dinickel complexes [(3PDI2)Ni2(PMe3)2(μ-Cl)](OTf)2and [(3PDI2)Ni2(PMe3)2(μ-Cl)](OTf); however, their higher electron counts lead to high-spin ground states that result from occupation of a high-lying δ/δ* manifold with significant Ni–NPDIσ* character. This change in ground state configuration reforms a M–M bonding interaction in the 37 e–complex, but formation of the 38 e–species again disrupts the M–M bond alongside the transfer of electron density to the ligand.

Separation of the rare-earth (RE) elements (Sc, Y, La–Lu) is challenging because of their similar chemical properties, but is necessary for their applications in renewable energy and electronic device technologies. The development of separation processes driven by kinetic factors represents a new area for this field. Herein, we disclose a novel method of separating select rare earths by reacting RE cyclopentadienides with the triradical species tris(2-tert-butylnitroxyl)benzylamine (1). The key proligand 1was characterized using a variety of techniques including X-ray crystallography, magnetometry, and EPR spectroscopy. When applied to an equimolar mixture of La:Y cyclopentadienide complexes, different rates of chelation of these organometallic precursors by 1were observed, affording a separation factor of 26 under the reported conditions.

A series of uranium(VI)–acetylide complexes of the general formula UVI(O)(C≡C–C6H4–R)[N(SiMe3)2]3, with variation of the parasubstituent (R = NMe2, OMe, Me, Ph, H, Cl) on the aryl(acetylide) ring, was prepared. These compounds were analyzed by 13C NMR spectroscopy, which showed that the acetylide carbon bound to the uranium(VI) center, U–C≡C–Ar, was shifted strongly downfield, with δ(13C) values ranging from 392.1 to 409.7 ppm for Cl and NMe2substituted complexes, respectively. These extreme high-frequency 13C resonances are attributed to large negative paramagnetic (σpara) and relativistic spin–orbit (σSO) shielding contributions, associated with extensive U(5f) and C(2s) orbital contributions to the U–C bonding in title complexes. The trend in the 13C chemical shift of the terminal acetylide carbon is opposite that observed in the series of parent (aryl)acetylenes, due to shielding effects of the parasubstituent. The 13C chemical shifts of the acetylide carbon instead correlate with DFT computed U–C bond lengths and corresponding QTAIM delocalization indices or Wiberg bond orders. SQUID magnetic susceptibility measurements were indicative of the Van Vleck temperature independent paramagnetism (TIP) of the uranium(VI) complexes, suggesting a magnetic field-induced mixing of the singlet ground-state (f0) of the U(VI) ion with low-lying (thermally inaccessible) paramagnetic excited states (involved also in the perturbation-theoretical treatment of the unusually large paramagnetic and SO contributions to the 13C shifts). Thus, together with reported data, we demonstrate that the sensitive 13C NMR shifts serve as a direct, simple, and accessible measure of uranium(VI)–carbon bond covalency.

A nickel-catalyzed cross-coupling of toluene derivatives with both aryl bromides and chlorides using a NIXANTPHOS-ligated nickel(II) complex has been developed. The key factor to success is proposed to be the catalyst activation of toluene by a cation−π complex, enabling methyl arenes (pKa≈ 43) to be deprotonated with the relatively mild base NaN(SiMe3)2. This method facilitates access to a variety of sterically and electronically diverse hetero- and nonheteroaryl-containing diarylmethanes.

An aluminum complex of a tripodal tris(nitroxide)-based ligand has been prepared and characterized. The complex has the ability to participate in metal–ligand cooperative catalysis, which has been exploited for the hydroboration of both aldehydes and ketones. This represents new, transition-metal-like reactivity for an earth-abundant metal.

Uranium complexes in the +3 and +4 oxidation states were prepared using the anionic PN–(PN–= (N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) ligand framework. New complexes include the halide starting materials, (PN)2UIIII (1) and (PN)2UIVCl2(2), which both yield (PN)2UIV(N3)2(3) by reaction with NaN3. Compound 3was reduced with potassium graphite to produce a putative, transient uranium–nitrido moiety that underwent an intramolecular C–H activation to form a rare example of a parent imido complex, [K(THF)3][(PN)UIV(═NH)[iPr2P(C6H3Me)N(C6H2Me2CH2)]] (4). Calculated reaction energy profiles strongly suggest that a C–H insertion becomes unfavorable when a reductant is present, offering a distinctively different reaction pathway than previously observed for other uranium nitride complexes.

Selectively converting linear alkanes to α-olefins under mild conditions is a highly desirable transformation given the abundance of alkanes as well as the use of olefins as building blocks in the chemical community. Until now, this reaction has been primarily the remit of noble-metal catalysts, despite extensive work showing that base-metal alkylidenes can mediate the reaction in a stoichiometric fashion. Here, we show how the presence of a hydrogen acceptor, such as the phosphorus ylide, when combined with the alkylidene complex (PNP)Ti=CHtBu(CH3) (PNP=N[2-P(CHMe2)2-4-methylphenyl]2−), catalyses the dehydrogenation of cycloalkanes to cyclic alkenes, and linear alkanes with chain lengths of C4to C8to terminal olefins under mild conditions. This Article represents the first example of a homogeneous and selective alkane dehydrogenation reaction using a base-metal titanium catalyst. We also propose a unique mechanism for the transfer dehydrogenation of hydrocarbons to olefins and discuss a complete cycle based on a combined experimental and computational study.

A synthetic route has been developed for a series of 3d homobimetallic complexes of Mn, Fe, Co, Ni, and Cu using three different pyridyldiimine and pyridyldialdimine macrocyclic ligands with ring sizes of 18, 20, and 22 atoms. Crystallographic analyses indicate that while the distances between the metals can be modulated by the size of the macrocycle pocket, the flexibility in the alkyl linkers used to construct the macrocycles enables the ligand to adjust the orientation of the PD(A)I fragments in response to the geometry of the [M2(μ-Cl)2]2+core, particularly with respect to Jahn–Teller distortions. Analyses by UV–vis spectroscopy and SQUID magnetometry revealed deviations in the properties [M2(μ-Cl)2]2+-containing complexes bound by standard mononucleating ligands, highlighting the ability of macrocycles to use ring size to control the magnetic interactions of pseudo-octahedral, high-spin metal centers.