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The POM capsule functions as a redox-active inorganic crown ether. Specifically, Cs+ ions are captured in the crown-ether-like pores {Mo3Fe3O6}, which exist on the surface of the capsule, and electrons are stored in the Mo atoms of the capsule.

Molecular metal chalcogenides have attracted great attention as electrocatalysts for the hydrogen evolution reaction (HER). However, efficient utilisation of the active sites and catalytic performance modulation has been challenging. Here we explore the design of immobilized molecular molybdenum polyselenides [Mo2O2S2(Se2)(Sex)]2– that exhibit efficient hydrogen evolution at low overpotential and stability over 1000 cycles. Density functional calculations provide evidence of a unimolecular mechanism in the HER process via the exploration of viable reaction pathways. The discussed findings are of a broad interest in the development of efficient molecular electrocatalytic materials.

The reaction mechanism for formation of cyclic carbonates from CO2 and 1,2-epoxyhexane catalyzed by an [Al(amino-triphenolate)]/NBu4I binary system has been investigated by using density functional theory (DFT) based methods. A monometallic mechanism is proposed and the main steps of the reaction are described in detail. The energetic span model (δE) was used to theoretically determine the turnover frequencies (TOFs) of the catalytic cycle and to evaluate the efficiency of the aluminum complex in mediating the CO2 addition reaction. Our findings indicate that entropy changes in solution must be included in order to compute the TOF values in line with the experimental results.

In rhodium catalysed borylation of cyclic olefins, the synergy between bidentate NHC ligands, that modify cationic Rh(I) species, and the use of non-polar solvents, such as cyclohexane, is the key factor to favour a less energetically demanding route towards the formation of diborated products versus allyl boronate esters.

Several SPANphos ligands based on a spirobichroman backbone, introduced as a putative trans ligand, form compounds of the type [Rh(nbd)(SPANphos)]BF4 (1–6) in which both norbornadiene and SPANphos act as cis chelating ligands. The cyclooctadiene rhodium chloride derivatives form bimetallic complexes. Crystal structures for several of these compounds and free ligands are reported. Semiemperical AM1 and DFT calculations show that spirobichroman can assume several conformations, some of which are suitable for the formation of cis chelating SPANphos. All calculations on SPANphos complexes of PdCl2, PtCl2 and Rh(CO)Cl show that the trans complex is more stable by 4–10 kcal mol−1. The cis conformation in 1–6 is enforced by the cis chelating norbornadiene ligand.

To provide further insight into electronic and steric factors and to quantify their relative importance, we studied in detail the migratory CO insertion step for RhMe(CO)I2(L–L) systems (L–L = dppms (PPh2CH2P(S)Ph2) or dppe (PPh2CH2CH2PPh2)), Monsanto catalysts and some electronically unsymmetrical diphosphine model systems. The difference in the reaction rates of dppms and dppe has a clear electronic origin that reflects the different properties of sulfide phosphine (π-donor) and phosphine (π-acid) ligands. Molecular orbital calculations clearly show that dppms strongly increases back-bonding to CO and favors the overlap between CO and methyl. Steric effects modulate the barrier, which decreases more for dppe than it does for dppms. For dppms, the electronic contribution that phenyl phosphine substituents make to lower the barrier is greater than that made by purely steric effects. The sulfide phosphine ligand dppms accelerates the carbonyl insertion because of its π-donor capability. For the diphosphine ligands we studied, the energy barrier varied gradually as basicity varied, and the slowest kinetics is shown by the most electron-donating ligand. The basicity dependence is stronger when the phosphine ligand occupies a trans position to CO. On the other hand and in unsymmetrical diphosphine complexes, phosphine basicity affects stability and reactivity in opposite ways.

Addition of a dithiol ligand HS(CH2)nSH (n= 2–4) to [{Rh(µ-OMe)(cod)}2](cod = cycloocta-1,5-diene) afforded dithiolate-bridged complexes [{Rh2[µ-S(CH2)nS](cod)2}x](x= 1 or 2). These diene complexes react with carbon monoxide to give the binuclear tetracarbonyl complexes [Rh2{µ-S(CH2)nS}(CO)4]. The crystal structures of [Rh2{µ-S(CH2)nS}(cod)2](n= 2 or 3) have been determined by X-ray diffraction methods. A study of the electronic structure of the complexes by analysis of the topology of the charge density shows that in spite of a zero formal bond order between the rhodium atoms a direct metal–metal interaction may be characterized.

The Ti8C12 molecule, recently observed as a positive ion by Castleman et al., is presented as a cluster with seven possible conformations which have been characterized as local minima by means of ab initio Hartree–Fock calculations.

This paper describes the development of quantitative structure–enantioselectivity and–activity relationships for the asymmetric hydroformylation of styrene by Rh–diphosphane. We used 3D steric- and electrostatic-type interaction fields derived from DFT calculations, and generated alignment-independent descriptors using GRid INdependent Descriptor (GRIND) methodology. The obtained QSPR models showed statistical significance and predictive ability. The most predictive model for enantioselectivity was obtained using steric-type 3D fields (MSF) based on the local curvature electron density isosurface that accounts for catalyst shape (r2 = 0.92, q2 = 0.68). We obtained the most predictive model for activity using a combination of shape- and electrostatic-based 3D fields (r2 = 0.99, q2 = 0.74). The use of chemically meaningful descriptors provides insight into the factors governing catalytic activity and selectivity. The worst predicted ligand, kelliphite, showed the lowest preference for equatorial–apical coordination and low selectivity, which suggests that its intrinsic enantiotopic differentiation capacity can be lost through the occurrence of bis-equatorial paths. The selective catalysts Rh–chiraphite, –binapine, –diazaphospholane, and –yanphos showed the same pattern as Rh–binaphos, for which the origin of stereoinduction is known: the chirality at the apical site discriminates one alkene coordination path and one enantiomer. Ligands with electron withdrawing groups at phosphorus atoms such as chiraphite, kelliphite, binaphos, and diazaphospholane reduce ligand basicity and promote catalytic activity effectively. However, more complex relationships underlie the origin of activity, and the shape of the catalyst also needs to be considered such as for the Ph-BPE ligand. Comparison with previous studies suggests that reduction of the steric hindrance at the reaction centre which favors alkene coordination and insertion would also promote catalytic activity.

The adsorption of a polyoxometalate (POM) on a metal surface has been studied by means of a periodic plane wave DFT based method for the first time. In particular, we have analysed the most favourable adsorption sites of anion [SiW(12)O(40)](4-) on the Ag(111) surface and computed the infrared spectrum. Despite the intrinsic complexity of the system we have been able to fairly reproduce the observed IR spectrum and unambiguously discern the signal corresponding to W-O-Ag symmetric stretching, which appears at around 800 cm(-1).

The self-assembly of Secondary Phosphine Oxides (SPOs) into anionic bidentate chelates was used to construct unique systems for metal catalyzed transfer hydrogenation of ketones in isopropanol. Chelating bidentate or tridentate ligands were formed by assembly of secondary phosphine oxides through hydrogen bonding in the presence of rhodium trichloride as demonstrated by means of NMR spectroscopy and X-ray diffraction. When a chiral version of an SPO was used in asymmetric transfer hydrogenation of isopropanol and acetophenone, an enantiomeric excess of 89% was achieved. The presence of at least two ligands in the catalytically active species was confirmed by a positive non-linear effect. DFT calculations were applied to characterize several intermediates for the isopropanol dehydrogenation to produce a rhodium hydride complex and acetone. A transition state for the hydrogen-transfer was fully characterized, which revealed that the process occurs via a concerted outer-sphere mechanism.

The reactions of phosphido complexes [Nb(eta(5)-C(5)H(4)SiMe(3))(2)(L)(PPh(2))] [L = CO (1), CNxylyl (2), CNCy (3)] with alkynes have been carried out. The new diphenylphosphinoalkenyl niobocene complexes [Nb(eta(5)-C(5)H(4)SiMe(3))(2)(eta(1)-C-C(CO(2)CH(3))=C(R)PPh(2))(CO)] [R = H (4), CH(3) (5)] and [Nb(eta(5)-C(5)H(4)SiMe(3))(2)(eta(1)-C-C(CO(2)R)=C(CO(2)R)PPh(2))(CO)] [R = CH(3), (6), R = (t)Bu, (7)] were successfully synthesized by the reaction of with methyl propiolate (HC[triple bond]CCO(2)CH(3)) or methyl 2-butynoate (CH(3)C[triple bond]CCO(2)CH(3)) and dimethyl 2-butynedioate [(CH(3) O(2)C)C[triple bond]C(CO(2)CH(3))] or di(tert-butyl) 2-butynedioate [((t)BuO(2)C)C[triple bond]C(CO(2)(t)Bu)], respectively. However, reaction was not observed with more electron-rich alkynes. Complex reacted with methyl propiolate, methyl 2-butynoate (MeC[triple bond]CCO(2)Me) or di(tert-butyl) 2-butynedioate to give surprising new heteroniobacycle complexes [Nb(eta(5)-C(5)H(4)SiMe(3))(2)(eta(1)-C-C(=NXylyl)C(R(1))=C(R(2))PPh(2)-kappa(1)-P)] [R(1) = H, R(2) = CO(2)Me (8); R(1) = Me, R(2) = CO(2)Me (9); R(1) = CO(2)(t)Bu, R(2) = CO(2)(t)Bu (10)]. Finally, the phosphido complexes and reacted with phenylacetylene (PhC[triple bond]CH) to give new diphenylphosphinoalkenyl niobocene derivatives [Nb(eta(5)-C(5)H(4)SiMe(3))(2)(eta(1)-C-C(C(6)H(5))=C(H)PPh(2))(CNR)] [R = xylyl (11), Cy (12)]. All of these compounds were characterized by NMR spectroscopy and the molecular structure of was determined by single-crystal X-ray diffraction studies. Theoretical studies were also carried out by means of density functional theory (DFT) calculations on the insertions of alkynes into the Nb-P bond in the phosphido niobocenes.