Synergistic effects in ambiphilic phosphino-borane catalysts for the hydroboration of CO2

The benefit of combining both a Lewis acid and a Lewis base in a catalytic system has been established for the hydroboration of CO₂, using ferrocene-based phosphine, borane and phosphino-borane derivatives.

Charge Localisation in Heavy Alkali Metal Ion Complexes of 4,4'-Biphenyldicarboxylate

Crystal structure determinations on the isomorphous RbI and CsI complexes of 4,4′-biphenyldicarboxylate have shown the carboxylate entities to be coordinated in an unusual fashion where both oxygen atoms are in a tetrahedral environment indicative of negative charge localisation on each. The metal ions also show a highly irregular form of six-coordination, while the biphenyl units are planar, seemingly as a result of attractive interactions between the ortho hydrogen atoms.

Counter-ion control of structure in uranyl ion complexes with 2,5-thiophenedicarboxylate

Various counterions containing d-block metal ions and N-donating chelators were used to generate one- and two-dimensional uranyl-2,5-thiophenedicarboxylate species, one of them displaying inclined polycatenation.

Complexes of the tripodal phosphine ligands PhSi(XPPh2)3(X = CH2, O): synthesis, structure and catalytic activity in the hydroboration of CO2

The coordination chemistry of Fe²⁺, Co²⁺and Cu⁺ions was explored with the ligands PhSi{CH₂PPh₂}₃(1) and PhSi{OPPh₂}₃(2), so as to evaluate the impact of the electronic properties of the tripodal phosphorus ligands on the structure and reactivity of the corresponding complexes.

Metal-free dehydrogenation of formic acid to H2 and CO2 using boron-based catalysts

The decomposition of formic acid to H₂ and CO₂ under metal-free conditions has been unveiled using dialkylborane derivatives as catalysts.

Formic acid is at the crossroads of novel sustainable energy strategies because it is an efficient H₂ carrier. Yet, to date, its decomposition to H₂ relies on metal-based catalysts. Herein, we describe the first metal-free catalysts able to promote the dehydrogenation of formic acid. Using dialkylborane derivatives, HCOOH is decomposed to H₂ and CO₂ in the presence of a base with high selectivity. Experimental and computational results point to the involvement of bis(formyloxy)borates as key intermediates in the C–H bond activation of a formate ligand.

U(III)-CN versus U(IV)-NC coordination in tris(silylamide) complexes

Treatment of the metallacycle [UN*2(N,C)] [N* = N(SiMe3)2; N,C = CH2SiMe2N(SiMe3)] with [HNEt3][BPh4], [HNEt3]Cl, and [pyH][OTf] (OTf = OSO2CF3) gave the cationic compound [UN*3][BPh4] (1) and the neutral complexes [UN*3X] [X = Cl (3), OTf (4)], respectively. The dinuclear complex [{UN*(μ-N,C)(μ-OTf)}2] (5) and its tetrahydrofuran (THF) adduct [{UN*(N,C)(THF)(μ-OTf)}2] (6) were obtained by thermal decomposition of 4. The successive addition of NEt4CN or KCN to 1 led to the formation of the cyanido-bridged dinuclear compound [(UN*3)2(μ-CN)][BPh4] (7) and the mononuclear mono- and bis(cyanide) complexes [UN*3(CN)] (2) and [M][UN*3(CN)2] [M = NEt4 (8), K(THF)4 (9)], while crystals of [K(18-crown-6)][UN*3(CN)2] (10) were obtained by the oxidation of [K(18-crown-6)][UN*3(CN)] with pyridine N-oxide. The THF adduct of 1, [UN*3(THF)][BPh4], and complexes 2-7, 9 and 10 were characterized by their X-ray crystal structure. In contrast to their U(III) analogues [NMe4][UN*3(CN)] and [K(18-crown-6)]2[UN*3(CN)2] in which the CN anions are coordinated to the metal center via the C atom, complexes 2 and 9 exhibit the isocyanide U-NC coordination mode of the cyanide ligand. This U(III)/U(IV) differentiation has been analyzed using density functional theory calculations. The observed preferential coordinations are well explained considering the electronic structures of the different species and metal-ligand bonding energies. A comparison of the different quantum descriptors, i.e., bond orders, NPA/QTAIM data, and energy decomposition analysis, has allowed highlighting of the subtle balance between covalent, ionic, and steric factors that govern the U-CN/NC bonding.

Advances in f-element cyanide chemistry

By using the cyanide ligand, actinide compounds with unprecedented structures, U^III–CN vs. Ce^III–NC and U^III–CN vs. U^IV–NC coordination modes, and novel high-valent uranium complexes were revealed.

Solvent effects in solvo-hydrothermal synthesis of uranyl ion complexes with 1,3-adamantanediacetate

Uranyl ion complexes with 1,3-adamantanediacetate display different topologies arising from variations in coordination mode and the presence of additional ligands.