Tatiana R. Amarante

Synthesis, structural elucidation, and catalytic properties in olefin epoxidation of the polymeric hybrid material [Mo3O9(2-[3(5)-pyrazolyl]pyridine)]n.

The reaction of [MoO2Cl2(pzpy)] (1) (pzpy = 2-[3(5)-pyrazolyl]pyridine) with water in an open reflux system (16 h), in a microwave synthesis system (120 °C, 2 h), or in a Teflon-lined stainless steel digestion bomb (100 °C, 19 h) gave the molybdenum oxide/pyrazolylpyridine polymeric hybrid material [Mo3O9(pzpy)]n (2) as a microcrystalline powder in yields of 72–79%. Compound 2 can also be obtained by the hydrothermal reaction of MoO3, pzpy, and H2O at 160 °C for 3 d. Secondary products isolated from the reaction solutions included the salt (pzpyH)2(MoCl4) (3) (pzpyH = 2-[3(5)-pyrazolyl]pyridinium), containing a very rare example of the tetrahedral MoCl4(2–) anion, and the tetranuclear compound [Mo4O12(pzpy)4] (4). Reaction of 2 with excess tert-butylhydroperoxide (TBHP) led to the isolation of the oxodiperoxo complex [MoO(O2)2(pzpy)] (5). Single-crystal X-ray structures of 3 and 5 are described. Fourier transform (FT)-IR and FT Raman spectra for 1, 4, and 5 were assigned based on density functional theory calculations. The structure of 2 was determined from synchrotron powder X-ray diffraction data in combination with other physicochemical information. In 2, a hybrid organic–inorganic one-dimensional (1D) polymer, ∞(1)[Mo3O9(pzpy)], is formed by the connection of two very distinct components: a double ladder-type inorganic core reminiscent of the crystal structure of MoO3 and 1D chains of corner-sharing distorted {MoO4N2} octahedra. Compound 2 exhibits moderate activity and high selectivity when used as a (pre)catalyst for the epoxidation of cis-cyclooctene with TBHP. Under the reaction conditions used, 2 is poorly soluble and is gradually converted into 5, which is at least partly responsible for the catalytic reaction.

Synthesis, structural elucidation, and application of a pyrazolylpyridine-molybdenum oxide composite as a heterogeneous catalyst for olefin epoxidation.

The reaction of [MoO(2)Cl(2)(pypzEA)] (1) (pypzEA = ethyl[3-(pyridin-2-yl)-1H-pyrazol-1-yl]acetate) with water in a Teflon-lined stainless steel autoclave (100 °C) or in an open reflux system leads to the isolation of the molybdenum oxide/pyrazolylpyridine composite material [Mo(2)O(6)(HpypzA)] (2; HpypzA = [3-(pyridinium-2-yl)-1H-pyrazol-1-yl]acetate). The solid state structure of 2 was solved through single crystal and powder X-ray diffraction analyses in conjunction with information derived from FT-IR and (13)C CP MAS NMR spectroscopies and elemental analyses. In the asymmetric unit of 2, two crystallographically distinct Mo(6+) centers are bridged by a syn,syn-carboxylate group of HpypzA. The periodic repetition of these units along the a axis of the unit cell leads to the formation of a one-dimensional composite polymer, (∞)(1)[Mo(2)O(6)(HpypzA)]. The outstretched pyrazolylpyridine groups of adjacent polymers interdigitate to form a zipper-like motif, generating strong onset π-π contacts between adjacent rings of coordinated HpypzA molecules. The composite oxide 2 is a stable heterogeneous catalyst for liquid-phase olefin epoxidation.

Heterometallic complexes involving iron(II) and rhenium(VII) centers connected by μ-oxido bridges

The reaction of FeI(2) with two equivalents of AgReO(4) in acetonitrile leads to yellow, crystalline Fe(ReO(4))(2)(CH(3)CN)(3) (1), and the treatment of 1 with four equivalents of CpFe(CO)(2)CN gives orange, crystalline Fe(ReO(4))(2)[CpFe(CO)(2)(CN)](4) (2). Compound 2 can also be prepared in one step by the reaction of FeI(2), AgReO(4) and CpFe(CO)(2)CN in dichloromethane. The structure of 1 consists of infinite chains in which alternating {Fe(CH(3)CN)(4)} and {Fe(ReO(4))(2)(CH(3)CN)(2)} units are linked by perrhenate anions to form a (-ReO(2)-O-Fe(ReO(4))(2)(CH(3)CN)(2)-O-ReO(2)-O-Fe(CH(3)CN)(4)-O-)(n) molecular wire. The structure of 2 shows a monomeric iron complex with a slightly distorted octahedral coordination environment consisting of four organometallic complexes coordinated in the equatorial plane via the cyanide groups and two monodentate perrhenates in the corresponding apical positions. Both compounds were further characterised in the solid state by IR spectroscopy, thermogravimetric analysis and magnetic susceptibility measurements. The magnetic data indicate that 1 behaves as a ferrimagnetic chain with 3D ordering below 8 K due to inter-chain interactions. Compound 2 has antiferromagnetic interactions within the Fe(ReO(4))(2)[CpFe(CO)(2)(CN)](4) clusters.

4,4′-Di-tert-butyl-2,2′-bipyridine

In the title compound, C18H24N2, the molecular unit adopts a trans conformation around the central C—C bond [N—C—C—N torsion angle of 179.2 (3)°], with the two aromatic rings almost coplanar [dihedral angle of only 0.70 (4)°]. The crystal packing is driven by co-operative contacts involving weak C—H⋯N and C—H⋯π interactions, and also the need to fill effectively the available space.

Tris(4,4'-di-tert-butyl-2,2'-bipyridine-κN,N')molybdenum(II) μ(6)-oxido-dodeca-μ(2)-oxido-hexa-oxidohexa-molybdate(VI) acetonitrile tetra-solvate.

The asymmetric unit of the title compound, [Mo(C18H24N2)3][Mo6O19]·4CH3CN, comprises an [Mo(di-t-Bu-bipy)3]2+ cation (di-t-Bu-bipy is 4,4′-di-tert-butyl-2,2′-bipyridine), two halves of Lindqvist-type [Mo6O19]2− anions (with each anion completed by the application of a center of inversion) and four acetonitrile solvent molecules. The geometry around the metal atom of the cation resembles a distorted octahedron, with each of the three di-t-Bu-bipy ligands being almost planar [deviation from planarity < 6.3 (2)°]. Supramolecular interactions, namely Mo=O⋯π, C N⋯π, C—H⋯O and C—H⋯N, along with electrostatic forces, mediate the crystal packing. Two of the tert-butyl groups are affected by rotational disorder which was modeled over two distinct positions with major site occupancies of 0.707 (9) and 0.769 (8).

4,4′-Di-tert-butyl-2,2′-dipyridinium dichloride

In the title compound, C18H26N2 2+·2Cl−, the complete dication is generated by crystallographic inversion symmetry; both N atoms are protonated and engaged in strong and highly directional N—H⋯Cl hydrogen bonds. Additional weak C—H⋯Cl contacts promote the formation of a tape along ca. [110]. The crystal structure can be described by the parallel packing of these tapes. The crystal studied was a non-merohedral twin with twin law [−1 0 0, 0 −1 0, −0.887 0.179 1] and the final BASF parameter refining to 0.026 (2) .

2-(1H-Pyrazol-3-yl)pyridinium chloride monohydrate

The title organic salt, C8H8N3 +·Cl−·H2O, exhibits a rich hydrogen-bonding network involving all constituent species. The water molecules are engaged in strong O—H⋯Cl interactions with the chloride anions, two neighboring protonated 2-(1H-pyrazol-3-yl)pyridinium species interact via N—H⋯N bonds with two pyrazole rings. Further, a short and highly directional C—H⋯O interaction is observed connecting the pyridinium ring to the water molecule of crystallization. Weak C—H⋯Cl and N—H⋯Cl interactions contribute to the stabilization of the crystal structure.

Mo4(η3-allyl)4Cl2(OH)2(CO)8: the first cubane-type Mo2+ organometallic complex with μ3-OH and μ3-Cl bridges

The reaction between fluorenyllithium and Mo(eta(3)-C(3)H(5))Cl(NCMe)(2)(CO)(2) led to the isolation of di-mu(3)-chlorido-di-mu(3)-hydroxido-tetrakis[(eta(3)-allyl)dicarbonylmolybdenum(II)]-9-fluorenone-tetrahydrofuran (1/1/1), [Mo(4)(C(3)H(5))(4)Cl(2)(OH)(2)(CO)(8)].C(4)H(8)O.C(13)H(8)O. The tetrametallic Mo(4) unit constitutes the first example of a complex containing simultaneously two mu(3)-OH groups and two mu(3)-Cl anions capping the metallic trigonal prism. The four crystallographically independent Mo(2+) centres exhibit distorted octahedral geometry with the eta(3)-allyl groups being trans-coordinated to a mu(3)-OH group and the carbonyl groups occupying the equatorial plane. Space-filling tetrahydrofuran and 9-fluorenone molecules are engaged in strong O-H...O hydrogen-bonding interactions with Mo(4)(eta(3)-allyl)(4)Cl(2)(OH)(2)(CO)(8) complexes.

1-Hydroxy-1,1,3,3,3-pentaphenyldisiloxane, [Si2O(OH)(Ph)5], at 100 K

In the crystal structure of the title compound, C30H26O2Si2, one Si(Ph)3 residue is bound to another Si(OH)(Ph)2 residue via a non-linear Si—O—Si bridge. The asymmetric unit is composed of two such molecules which interact, on the one hand, via a strong and highly directional O—H⋯O hydrogen bond involving the two neighbouring Si—OH units and, on the other, via an O—H⋯π contact connecting the second hydroxyl group with an adjacent phenyl group.

Crystal structure of an organic-inorganic supra-molecular salt based on a 4,4'-methyl-enebis(3,5-dimethyl-1H-pyrazol-2-ium) cation and a β-octa-molybdate anion.

The crystal structure of the title novel organic–inorganic supramolecular salt is based in the in situ formation of 4,4′-methylenebis(3,5-dimethyl-1H-pyrazol-2-ium) cations, which are engaged in N—H⋯O hydrogen bonds with β-octamolybdate anions.