Boere, Rene

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    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.
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    Synthesis, characterization and anticancer activities of cationic η6-p-cymene ruthenium(II) complexes containing phosphine and nitrogenous ligands
    (Elsevier, 2022) Guimaraes, Ivelise D. L.; Marszaukowski, Flávia; Rutka, Priscila B.; Borge, Luis F.; Ribeiro, Renan A. P.; Ricardo de Lazaro, Sergio; Castellen, Patrícia; Sagoe-Wagner, Araba; Golsteyn, Roy M.; Boeré, René T.; Wohnrath, Karen
    Ruthenium-based anticancer agents have created a center of attention in the field of inorganic medicinal chemistry. The first fully characterized cationic ruthenium(II)-arene complexes [Ru(η6-p-cymene) (PAr3)LNCl]+ with highly lipophilic PAr3 ligands where Ar = 3,5-((CH3)3C)2C6H3– (L1), 3,5-(CH3)2C6H3– (L2), 4-CH3O-3,5-(CH3)2C6H2– (L3) and 4-CH3O-C6H4– (L4) with N = 3-methylpyridine (1–4, respectively), or L4 and 4-methylpyridine (5), or L4 and CH3CN (6) were obtained (yields 67–91%) as solids stable to light and air. Electrical conductance indicates that all the complexes are 1:1 electrolytes in solution. Their composition and purity have been unambiguously established by single-crystal X-ray diffraction, NMR spectroscopy and elemental analysis. The coordination geometries are uniform for all six complexes and each structure consist of a unipositive complex cation bearing the phosphine ligands L1-L4 and LN = 3-methylpyridine, 4-methylpyridine or CH3CN attached to the organometallic fragment. The equivalent unit cell volumes per formula unit decrease with 1 > 3 > 2 > 4 > 5 > 6, accurately reflecting the decreasing sizes of the phosphines L1-L4, and a greater occupied volume for 3-methyl- vs. 4-methylpyridine, and the smallest volume contribution from CH3CN. Electrochemical studies showed mixed electrochemical mechanisms (EC/ECE) from partial substitution of p-cymene by CH3CN ligands from the solvent. A large electrochemical stability window (>2.2 V) for Ru(II) was observed extending beyond the physiological E° range. The complexes were cytotoxic against human cancer cell lines in vitro, and some complexes altered cell morphology.
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    Frustrated and realized hydrogen bonding in 4-hydroxy-3,5- ditertbutylphenylphosphine derivatives
    (ACS Publications, 2022) Marszaukowski, Flávia; Boeré, René T.; Wohnrath, Karen
    Synthesis and molecular and supramolecular structures of a series of triarylphosphines P(Ph)3–n{4-RO-3,5-(tBu)2-C6H2}n (n = 1, 3; R = SiMe3, H) are reported. Chemical oxidation products E=P(Ph)3–n{4-RO-3,5-(tBu)2-C6H2}n (E = O, S, and Se; n = 1, 3; R = SiMe3, H) are also reported. Crystal structures of the reported compounds were determined by single-crystal X-ray diffraction, using a Hirshfeld atom refinement with NoSpherA2 through OLEX2, which provides an average improvement in C–C bond distance precision of 35%. Phosphine basicity for the phosphines with n = 1, R = H and n = 3, R = SiMe3, H was determined using the 1JP,Se values of the respective selenides; 1JP,Se = 699 Hz for E = Se, n = 3, and X = H identifies the most basic triarylphosphine ever reported. Intermolecular interactions allow classification of the 17 structures into 4 categories: those with only dispersion-induced short contacts, those with frustration of H-bonding, those with only classic H-bonding, and those with combinations of classic and frustration of H-bonding. A “double phenol embrace” classified by an R22(4) graph set is a weak intermolecular synthon organizing lattices with 2,6-ditertbutylphenol functional groups. Classic H-bonding occurs only when E = O.
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    The copper sulfate hydration cycle. Crystal structures of CuSO4 (Chalcocyanite), CuSO4·H2O (Poitevinite), CuSO4·3H2O (Bonattite) and CuSO4·5H2O (Chalcanthite) at low temperature using non-spherical atomic scattering factors
    (Royal Society of Chemistry, 2022) Ibrahim, Mukaila A.; Boeré, René T.
    New structure determinations of CuSO4, CuSO4 H2O, CuSO4 3H2O and CuSO4 5H2O are reported from X-ray diffraction experiments at 100 (1) K. Combined density functional theory (ORCA) and non-spherical atomic scattering factor (NoSpherA2) computations enabled a Hirshfeld Atom Refinement (HAR) using custom atom scattering factors, accurately polarized and charge-compensated atom electron densities and accurate placement and shapes of the water hydrogen atoms. The results clearly demonstrate that all H atoms are involved in conventional H-bonding in the structures of the hydrates, contrary to an early X-ray diffraction determination on CuSO4 3H2O. Comparison to neutron diffraction results demonstrates the efficacy of this new HAR method. Colour variation in copper sulfates is interpretable by considering the relative number of sulfato and aqua ligands, given the lower crystal field splitting of the former relative to the latter.
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    Reversible redox chemistry of anionic imidazole-2-thione-fused 1,4-dihydro-1,4-diphosphinines
    (ACS Publications, 2022) Ramachandran, Mridhul R. K.; Schnakenburg, Gregor; Majumdar, Moumita; Kelemen, Zsolt; Gal, Dalma; Nyulaszi, Laszlo; Boeré, René T.; Streubel, Rainer K.
    Anionic 1,4-dihydro-1,4-diphosphinines were synthesized from tricyclic 1,4-diphosphinines and isolated as blue powdery salts M[2a–2c]. Reaction of solutions of these monoanions with iodomethane led to P-methylated compounds 3a–3c. An oxidation/reduction cycle was examined, starting from solutions of K[2a] via P–P coupled product 4a and back to K[2a], and the recyclability and redox chemistry of this cycle were confirmed by experimental and simulated cyclic voltammetry analysis, which is proposed as a potential 2-electron cathode for rechargeable cells. TD-DFT studies were used to examine species that might be involved in the process.