Themed collection Small Molecule Activation

Welcome to this themed issue of Dalton Transactions entitled “Small molecule activation”.

The rational design of trimetallic transition metal clusters supported by a trinucleating cyclophane ligand, L³⁻, and the reactivities of these complexes with dinitrogen and carbon dioxide are discussed.

While β-diketiminate (BDI or ‘nacnac’) ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity.

Catalysts for the oxidation of water are a vital component of solar energy to fuel conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu.

A new cobalt(II) complex reacts with N₂O under mild conditions and it catalytically performs the oxidation of aldehydes.

Polyoxometalate (POM)-based polyanionic fluorosurfactants self-assemble in hexafluoroisopropanol (HFIP) and activate hydrogen peroxide (H₂O₂), yielding efficient epoxidation of terminal alkenes.

Polyfluorooxometalates with a nitro ligands, Q₉[NaH₂Cu^II(NO₂)W₁₇F₆O₅₅], are oxygen donors for epoxidation of alkenes and catalytic with O₂ as terminal oxidant.

In addition to imidometal [Mⁿ⁺NR] units, transient metal–iminoiodane [M⁽ⁿ⁻²⁾⁺−N(R)IPh] adducts have been demonstrated as a possible “second oxidant” responsible for the imido group transfer reactivity.

Efficient photochemical and electrochemical CO₂-to-CO conversion using the N,O and N,S-NHC-containing dicarbonyl rhenium(I) bipyridine complexes is described.

The 6,6′′-diaminoterpyridine palladium(II) methylperoxo complex eliminates methyl hydroperoxide and reacts with acetone to form a novel hemi-aminal palladium complex, whereas the analogous platinum(II) complex generates formaldehyde and a platinum(II) hydroxo complex.

Water-soluble cis-mer-[IrH₂Cl(mtppms)₃] selectively dehydrogenated formic acid with a TOF of 298 000 h⁻¹, a final pressure of 140 bar, and a TON_max of 674 000.

A mononuclear nonheme cobalt(III)–hydroperoxide complex bearing a tetramethylated cyclam ligand, which is synthesized by the protonation of its corresponding cobalt(III)–peroxide complex, exhibits an amphoteric reactivity in electrophilic and nucleophilic oxidative reactions.

Activation of carbon disulfide (CS₂) by “masked” terminal nickel sulfide, [K(18-crown-6)][(L^tBu)Ni(S)], gives a trithiocarbonate complex. This result confirms the nucleophilicity of the sulfide ligand and expands the scope of reactivity for late metal sulfides.

A systematic study on iminopyridine palladium complexes demonstrates the relationship among NMR chemical shifts, ligand donor capability and catalytic performances.

Two types of zinc flavonolato complexes exhibit similar visible light-induced CO release reactivity in the solution and solid state.

The syntheses of new molybdenum dinitrogen complexes supported by the tridentate PEP ligands (E = N, P) prPP(Ph)P (2), prPPHP (3), PN(Ph)P (4) and prPN(Ph)P (5) are reported.

The mechanistic investigation of the reductive coupling vs. reductive disproportionation of CO₂ using magnesium(I) dimers bearing tripodal ligands has been carried out using DFT computational methods.

Synthetic studies targeting an m-terphenyl isocyanide analogue of the unstable 16e⁻, S = 1 complex CpCo(CO) are reported (Cp = η⁵-C₅H₅).

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.

New cobalt(II) complexes based on the TPMA ligand have been synthesized and characterized as molecular catalysts for photoinduced hydrogen evolution.

A cobalt complex using a bioinspired ligand, that mimics the molybdopterin cofactor, displays very good activity for electrochemical proton reduction in terms of turnover frequency, faradic yields and stability.

Dioxidomolybdenum(VI) complexes coordinated by functionalized bidentate iminophenolate ligands undergo oxygen atom transfer to PMe₃ to yield molybdenum(IV) oxido phosphino species that readily react with molecular O₂ to form molybdenum(VI) oxido peroxido complexes.

Novel triazolylidene gold(I) complexes were synthesized and activated by silver-free methodologies to generate catalysts for oxazoline synthesis and the C–H activation of arenes.

Activation of sulfur containing heteroallenes by nickel(II) alkyl complexes supported by the bulky hydrotris(3-phenyl-5-methylpyrazolyl)borate (Tp^Ph,Me) ligand is described.

We report the first example of a wholly inorganic mimic of a part of the FeMoco active centre of nitrogenases.

Titanium(IV) complexes bearing an unsubstituted tridentate bis(phenolate) N-heterocyclic carbene (NHC) were synthesized and structurally identified.

Tetraferrocenylporphyrins have been successfully deposited on ITO electrodes for O₂ photo-catalytic activation.

Amino triphenolate tungsten(VI) complexes have been prepared and they proved to be efficient catalysts in haloperoxidation reactions using hydrogen peroxide as a terminal oxidant and inorganic sources of halides.

Incorporation of the simple, readily available, building blocks ethylene, water and acetonitrile into Au(tpy)(OCOCF₃)₂ (tpy = 2-(p-tolyl)pyridine) in a one-step reaction leads to high yields of a new 6-membered ring gold(III) metallacycle complex.

New hetero- and homo-dinuclear Cu/Ni complexes electropolymerise potentiodynamically on glassy carbon electrodes and the polymers reduce dioxygen in water.

The reactivity of peroxo adducts towards H₂O₂ and phenols as functional catalase and RNR-R2 mimics is described.

The reduction of the iron enamido-phosphinimine complex under N₂ leads to dinitrogen activation and cleavage of the phosphinimine linkage to generate a di-iron complex with a bridging imido moiety.

Ni(PMe₃)₄, which can be obtained by reaction of either Ni(py)₄(O₂CH)₂ or Ni(O₂CH)₂·2H₂O with PMe₃, serves as a catalyst for the release of H₂ from formic acid.

A series of tailor-designed Ruthenium based water oxidation catalysts have been synthesized. By fine tuning of the catalyst structure, the turnover frequency was increased up to 500 s⁻¹ and the stability over 6000 turnovers.

Photocatalytic systems for CO₂ reduction using a Ru(II) photosensitiser and dinuclear Re(I) diimine tricarbonyl complexes (Re(n)Re), in which diimine ligands are connected by alkyl chains of various lengths (–C_nH_2n–: n = 2, 3, 4, 6, 14), as catalysts were investigated.

A highly stable and easy to synthesize aluminium complex bearing a flexible N₂O₂-donor salabza ligand (N,N′-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO₂ to epoxides (TOFs 120–3434 h⁻¹) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05–0.2 mol%).

A series of fluorophosphonium cations incorporating (C₆Cl₅) substituents, [Ph₂PF(C₆Cl₅)][B(C₆F₅)₄] 8, [PhPF(C₆Cl₅)₂][B(C₆F₅)₄] 9, and [(C₆F₅)PF(C₆Cl₅)₂][B(C₆F₅)₄] 10, were prepared and tested for air stability and catalytic activity.

Raman spectra have been collected on single crystals of over 20 different rare earth complexes containing reduced dinitrogen ligands to determine if these data will correlate with periodic properties or relative stability.

The Tp^MsCu core has been found to bind ammonia as well as to promote stoichiometric or catalytic modification of the ammonia N–H bond.

Three novel Re complexes with thiophene substituted bipyridine ligands were electropolymerized on GCE surface by oxidation. The surface-modified electrodes were tested for electrocatalytic CO₂ reduction.