Gerken, Michael

Permanent URI for this collection


Recent Submissions

Now showing 1 - 5 of 21
  • Item
    Lewis acid behavior of MoF5 and MoOF4: syntheses and characterization of MoF5(NCCH3), MoF5(NC5H5)n, and MoOF4(NC5H5)n (n- 1, 2)
    (ACS Publications, 2021) Bykowski, Janelle; Turnbull, Douglas; Hahn, Nolan R. J.; Boeré, René T.; Wetmore, Stacey D.; Gerken, Michael
    The Lewis acid–base adducts MoF5(NC5H5)n and MoOF4(NC5H5)n (n = 1, 2) were synthesized from the reactions of MoF5 and MoOF4 with C5H5N and structurally characterized by X-ray crystallography. Whereas the crystal structures of MoF5(NC5H5)2 and MoOF4(NC5H5)2 are isomorphous containing pentagonal-bipyramidal molecules, the fluorido-bridged, heptacoordinate [MoF5(NC5H5)]2 dimer differs starkly from monomeric, hexacoordinate MoOF4(NC5H5). For the weaker Lewis base CH3CN, only the 1:1 adduct, MoF5(NCCH3), could be isolated. All adducts were characterized by Raman spectroscopy in conjunction with vibrational frequency calculations. Multinuclear NMR spectroscopy revealed an unprecedented isomerism of MoOF4(NC5H5)2 in solution, with the pyridyl ligands occupying adjacent or nonadjacent positions in the equatorial plane of the pentagonal bipyramid. Paramagnetic MoF5(NC5H5)2 was characterized by electron paramagnetic resonance (EPR) spectroscopy as a dispersion in solid adamantane as well as in a diamagnetic host lattice of MoOF4(NC5H5)2; EPR parameters were computed using ZORA with the BPW91 functional using relativistic all-electron wave functions for Mo and simulated using EasySpin. Density functional theory calculations (B3LYP) and natural bond orbital analyses were conducted to elucidate the distinctive bonding and structural properties of all adducts reported herein and explore fundamental differences observed in the Lewis acid behavior of MoF5 and MoOF4.
  • Item
    Fluoride-ion acceptor properties of WSF4: synthesis, characterization, and computational study of the WSF5¯ and W2S2F9¯ anions and 19F NMR spectroscopic characterization of the W2OSF9¯ anion
    (American Chemical Society, 2012) Nieboer, Jared; Haiges, Ralf; Hillary, William; Yu, Xin; Richardet, Tyler; Mercier, Hélène P. A.; Gerken, Michael
    The new [N(CH3)4][WSF5] salt was synthesized by two preparative methods: (a) by reaction of WSF4 with [N(CH3)4][F] in CH3CN and (b) directly from WF6 using the new sulfide-transfer reagent [N(CH3)4][SSi(CH3)3]. The [N(CH3)4][WSF5] salt was characterized by Raman, IR, and 19F NMR spectroscopy and [N(CH3)4][WSF5]·CH3CN by X-ray crystallography. The reaction of WSF4 with half an aliquot of [N(CH3)4][F] yielded [N(CH3)4][W2S2F9], which was characterized by Raman and 19F NMR spectroscopy and by X-ray crystallography. The WSF5– and W2S2F9– anions were studied by density functional theory calculations. The novel [W2OSF9]− anion was observed by 19F NMR spectroscopy in a CH3CN solution of WOF4 and WSF5–, as well as CH3CN solutions of WSF4 and WOF5–.
  • Item
    A new synthetic route to rhenium and iodine oxide fluoride anions: The reaction between oxoanions and sulfur tetrafluoride
    (Elsevier, 2015) Goettel, James T.; Turnbull, Douglas; Gerken, Michael
    Sulfur tetrafluoride is a reagent for the one-step syntheses of [ReVIIO2F4]−, [IVOF4]−, and [IVIIO2F4]− salts. Pure Ag[ReO2F4] as well as its CH3CN coordination compounds were obtained from CH3CN solvent. The Ag[ReO2F4], [Ag(CH3CN)2][ReO2F4], and [Ag(CH3CN)4][ReO2F4] salts were characterized by Raman spectroscopy. The [Ag(CH3CN)4][ReO2F4]·2CH3CN coordination compound was characterized by single-crystal X-ray diffraction. The reaction of SF4 with KIO4 in anhydrous HF gave the known K[IO2F4] salt. The reaction of [N(CH3)4]IO3 with SF4 in CH3CN yielded the new [N(CH3)4][IOF4] salt, which was characterized by Raman spectroscopy.
  • Item
    The structure of trimethyltin fluoride
    (Royal Society of Chemistry, 2015) Chaudhary, Praveen; Bieringer, Mario; Hazendonk, Paul; Gerken, Michael
    The solid-state structure of (CH3)3SnF was reinvestigated by X-ray diffraction techniques as well as by multi-nuclear solid-state NMR spectroscopy. Trimethyltin fluoride crystallizes from hot ethanol in the orthorhombic space group Pnma at room temperature and changes to a low-temperature orthorhombic phase (space group: Cmcm) below −70 °C. In both modifications, trimethyltin fluoride adopts a linear chain structure with symmetric fluorine bridges, in contrast to previous reports. During its synthesis, (CH3)3SnF precipitates in another, poorly crystalline modification, as shown by powder X-ray diffraction. Solid-state MAS NMR experiments of both room-temperature phases of (CH3)3SnF (non-recrystallized and recrystallized) were carried out for the 1H, 13C, 19F, and 119Sn nuclei. The 119Sn{19F, 1H} and 19F{1H} NMR spectra offer unambiguous determination for the 19F and 119Sn shielding tensors. The 119Sn{1H} solid-state NMR spectra are in agreement with pentacoordination of Sn in this compound for the non-recrystallized and the recrystallized modifications. Based on the solid-state NMR results, the non-recrystallized modification of (CH3)3SnF also consists of linear, symmetrically fluorine-bridged chains, and differs from the recrystallized orthorhombic phase only in packing of the chains.
  • Item
    Interactions between SF4 and fluoride: a crystallographic study of solvolysis products of SF4·nitrogen-base adducts by HF
    (American Chemical Society, 2016) Goettel, James T.; Kostiuk, Nathan; Gerken, MIchael
    Adducts between SF4 and a nitrogen base are easily solvolyzed by HF, yielding the protonated nitrogen base and fluoride. Salts resulting from the solvolysis of SF4·NC5H5, SF4·NC5H4(CH3), SF4·NC5H3(CH3)2, and SF4·NC5H4N(CH3)2 have been studied by Raman spectroscopy and X-ray crystallography. Crystal structures were obtained for pyridinium salts [HNC5H5+]F–·SF4 and [HNC5H5+]F–[HF]·2SF4, the 4-methylpyridinium salt [HNC5H4(CH3)+]F–·SF4, the 2,6-methylpyridinium salt [HNC5H3(CH3)2+]2[SF5–]F–·SF4, and 4-(dimethylamino)pyridinium salts [HNC5H4N(CH3)2+]2[SF5–]F–·CH2Cl2 and [NC5H4N(CH3)2+][HF2–]·2SF4. In addition, the structure of [HNC5H4(CH3)+][HF2–] was obtained. 4,4′-Bipyridyl reacts with SF4 and 1 and 2 equiv of HF to give the 4,4′-bipyridinium salts [NH4C5–C5H4NH+]F–·2SF4 and [HNH4C5–C5H4NH2+]2F–·4SF4, respectively. These structures exhibit a surprising range of bonding modalities and provide an extensive view of SF4 and its contacts with Lewis basic groups in the solid state. The interactions range from the strong F4S–F– bond in the previously observed SF5– anion to weak F4S---F–, F4S(---F–)2, and F4S(---FHF–)2 dative bonds.