Paper on fullerene anion chemistry accepted by Chemical Science

Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium
Chem. Sci., Accepted.
Samuel R. Lawrence,  C. André Ohlin, David B. Cordes,  Alexandra M. Z. Slawin, Andreas Stasch

Abstract: The reaction of the magnesium(I) complexes [{( Arnacnac)Mg}2], ( Arnacnac = HC(MeCNAr)2 , Ar =Dip (2,6-iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3 )) with fullerene C60 afforded a series of hydrocarbon-soluble fulleride complexes [{(Arnacnac)Mg}nC60], predominantly with n = 6, 4 and 2. 13C{1H} NMR spectroscopic studies show both similarities (n = 6) and differences (n = 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. The molecular structures of[{(Arnacnac)Mg}nC60] with n = 6, 4 and 2 can be described as inverse  coordination complexes of n [(Arnacnac)Mg]+ ions with C60n- anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C606- ion. Experimental studies show the flexible ionic nature of the {(Arnacnac)Mg}+····C606-  coordination bonds. DFT calculations on the model complex [{(Menacnac)Mg}6C60] (Menacnac = HC(MeCNMe)2) support the formulation as an ionic complex with a centralC606- anion and comparable frontier orbitals toC606- with a small HOMO-LUMO gap. The reduction of C60 to its hexaanion gives an indication about the reducing strength of dimagnesium(I) complexes.

Paper on microwave synthesis accepted by European Journal of Inorganic Chemistry

Microwave Synthesis of Alkali-Free Hexaniobate, Decaniobate, and Hexatantalate Polyoxometalate Ions
in Eur. J. Inorg. Chem.201935, 3913-3918.   Link
M. A. Rambaran, M. Pascual-Borràs and C. A. Ohlin

Abstract:
 Microwave synthesis of polyoxoniobates and -tantalates circumvents the prolonged heating required by conventional hydrothermal methods, while providing comparable or greater yields. Microwave irradiation allows synthesis of polyoxoniobates from anhydrous niobium pentoxide, in lieu of niobic acid and sets the precedent for the discovery of new polyoxoniobates and -tantalates.

Paper on protonation in Anderson-type POMs published in Inorganic Chemistry

Direct Single- and Double-Side Triol-Functionalization of the Mixed Type Anderson Polyoxotungstate [Cr(OH)3W6O21]6–”

in Inorganic Chemistry, 2019, 58(1), 106-113. Link

Nadiia I. Gumerova, Tania Caldera Fraile, Alexander Roller, Gerald Giester, Magda Pascual-Borràs, C. André Ohlin, and Annette Rompel

Abstract: Since the first successful triol-functionalization of the Anderson polyoxometalates, the protons of the central octahedron X(OH)6 (X—heteroatom) have been considered as a prerequisite for their functionalization and therefore the functionalization of Anderson structures from the unprotonated sides have never been reported. Herein, for the first time, we organically functionalized the mixed-type Anderson polyoxometalate with real-time observation of hybrid anion formation.

Paper on protonation in polyoxomelates accepted by Dalton Transactions

“Protonation and water exchange kinetics in sandwich polyoxometalates”

in Dalton Transactions, 2018, 47, 13602-13607. Link.

C. André OhlinMagda Pascual-Borràs

Abstract: Density functional theory is used to explore the locus and consequences of protonation in [Zn4(H2O)2(PW9O34)2]10− . The results are used to explain recent observations regarding the contrasting pH effects on the water-ligand exchange in [Mn4(H2O)2(P2W15O56)2]16− and [Co4(H2O)2(P2W15O56)2]16− , and the general effect of protonation on solvent exchange in metal oxides is discussed.

Chapter published in Annual Reports on NMR Spectroscopy

17O NMR as a Tool in Discrete Metal Oxide Cluster Chemistry

in Annual Reports on NMR Spectroscopy. Link.

C. André Ohlin, William H. Casey

Abstract: This chapter covers recent developments in 17O NMR spectroscopy as applied to discrete metal oxide clusters, particularly in the context of their use as models in geochemistry and catalysis. Dynamic 17O NMR methods based on the McConnell–Bloch equations are explored in depth, and recent advances are reviewed. High-pressure NMR methods are also discussed and reviewed, as are recent developments in the use of density functional theory in the computation of 17O NMR shifts in polyoxometalates. The emphasis of the chapter is on the new developments that promise to reinvigorate 17O NMR as a central tool in the study of aqueous chemical kinetics, with the most urgent challenges being understanding the rates of isotopic substitution into bridging oxygens in clusters.

Paper on fractionation accepted by Geochimica et Cosmochimica Acta

Computational Prediction of Mg-Isotope Fractionation Between Aqueous [Mg(OH2)6]2+ and Brucite

Geochim. Cosmochim. Acta., Accepted. Link.

Christopher A. Colla, W. H. Casey, C. André Ohlin

Abstract: The fractionation factor in the magnesium-isotope fractionation between aqueous solutions of magnesium and brucite remarkably changes sign with increasing temperature, as uncovered by recent experiments.  To understand this behavior, the Reduced Partition Function Ratios and isotopic fractionation factors (Δ26/24Mgbrucite-Mg(aq)) are calculated using molecular models of aqueous [Mg(OH2)6]2+ and the mineral brucite at increasing levels of density functional theory.  The calculations were carried out on the [Mg(OH2)6]2+·12H2O cluster, along with different Pauling-bond-strength-conserving models of the mineral lattice of brucite. Three conclusions were reached: i) all of the calculations overestimate <Mg-O> bond distances in the aqua ion complex relative to Tutton’s salts; ii) the calculations predict that brucite at 298.15 K is always enriched in the heavy isotope, in contrast with experimental observations; iii) the temperature dependencies of Wimpenny et al. (2014) and Li et al. (2014) could only be achieved by fixing the <Mg-O> bond distances in the [Mg(OH2)6]2+·12H2O cluster to values close to those observed in crystals that trap the hydrated ion. Read more.

 

Paper accepted by Dalton Trans.

PNacPNacE: (E = Ga, In, Tl) – monomeric group 13 metal(I) heterocycles stabilized by a sterically demanding bis(iminophosphoranyl)methanide

Dalton Trans., 2017, 46, 16872-16877.

Christian P. Sindlinger, Samuel R. Lawrence, Shravan Acharya, C. André Ohlin, Andreas Stasch

Abstract: The salt metathesis reaction of the sterically demanding bis(iminophosphoranyl)methanide alkali metal complexes LM (L – = HC(Ph 2 P=NDip) 2- , Dip = 2,6- i Pr 2 C 6 H 3 ; M = Li, Na, K) with “GaI”, InBr or TlBr afforded the monomeric group 13 metal(I) complexes LE:, E = Ga (1), In (2) and Tl (3), and small quantities of LGaI 2 4 in case of Ga, respectively. The molecular structures of LE: 1-3 from X-ray single crystal diffraction show them to contain puckered six-membered rings with N,N’-chelating methanide ligands and two-coordinated metal(I) centres. Reduction reactions of LAlI 2 5, prepared by iodination of LAlMe 2 , were not successful and no aluminium(I) congener could be prepared so far. DFT studies on LE:, E = Al–Tl, were carried out and support the formulation as an anionic, N,N’-chelating methanide ligand coordinating to group 13 metal(I) cations. The HOMOs of the molecules for E = Al-In show a dominant contribution from a metal-based lone pair that is high in s-character. See http://pubs.rsc.org/en/content/articlelanding/2017/dt/c7dt04048b#!divAbstract