In Situ Flow MAS NMR Spectroscopy and Synchrotron PDF Analyses of the Local Response of the Brønsted Acidic Site in SAPO-34 during Hydration at Elevated Temperatures.

In situ flow magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and synchrotron-based pair distribution function (PDF) analyses were applied to study water's interactions with the Brønsted acidic site and the surrounding framework in the SAPO-34 catalyst at temperatures up to 300 °C for NMR spectroscopy and 700 °C for PDF. 29 Si enrichment of the sample enabled detailed NMR spectroscopy investigations of the T-atom generating the Brønsted site. By NMR spectroscopy, we observed dehydration above 100 °C and a coalescence of Si peaks due to local framework adjustments. Towards 300 °C, the NMR spectroscopy data indicated highly mobile acidic protons. In situ total X-ray scattering measurements analyzed by PDF showed clear changes in the Al local environment in the 250-300 °C region, as the Al-O bond lengths showed a sudden change. This fell within the same temperature range as the increased Brønsted proton mobility. We suggest that the active site in this catalyst under industrial conditions comprises not only the Brønsted proton but also SiO4 . To the best of our knowledge, this is the first work proposing a structural model of a SAPO catalyst by atomic PDF analysis. The combination of synchrotron PDF analysis with in situ NMR spectroscopy is promising in revealing the dynamic features of a working catalyst.

Crystal structure of catena-poly[[[aqua-bis-(di-methyl-formamide-κO)magnesium(II)]-µ3-(2,2'-bi-pyridine-5,5'-di-carboxyl-ato-κ5O2:O2':N,N':O5)-[di-chlorido-platinum(II)]] di-methyl-formamide monosolvate].

The title compound, {[MgPtCl2(C12H6N2O4)(C3H7NO)2(H2O)]·C3H7NO} n , is a one-dimensional coordination polymer. The structure consists of Pt-functionalized bi-pyridine ligands connected by MgII cations, as well as coordinating and non-coordinating solvent mol-ecules. The PtII cation is coordinated by the two N atoms of the bi-pyridine moiety and two Cl atoms in a square-planar fashion. This coordination induces an in-plane bend along the bi-pyridine backbone of approximately 10° from the linear ideal of a conjugated π-system. Likewise, the coordination to the MgII cation induces a significant bowing of the plane of the bi-pyridine of about 12°, giving it a distinct curved appearance. The carboxyl-ate groups of the bi-pyridine ligand exhibit moderate rotations relative to their parent pyridine rings. The MgII cation has a fairly regular octa-hedral coordination polyhedron, in which three vertices are occupied by O atoms from the carboxyl-ate groups of three different bi-pyridine ligands. The remaining three vertices are occupied by the O atoms of two di-methyl-formamide (DMF) mol-ecules and one water mol-ecule. The one-dimensional chains are oriented in the [01-1] direction, and non-coordinating DMF mol-ecules can be found in the space between the chains. The shortest inter-molecular O⋯H contacts are 2.844 (4) and 2.659 (4) Å, suggesting moderate hydrogen-bonding inter-actions. In addition, there is a short inter-molecular Pt⋯Pt contact of 3.491 (1) Å, indicating a Pt stacking inter-action. Some structure-directing contribution from the hydrogen bonding and Pt⋯Pt inter-action is probable. However, the crystal packing seems to be directed primarily by van der Waals inter-actions.

Crystal structure of dimethyl 4,4'-di-meth-oxy-biphenyl-3,3'-di-carboxyl-ate.

In the title compound, C18H18O6, the benzene rings are coplanar due to the centrosymmetric nature of the mol-ecule, with an inversion centre located at the midpoint of the C-C bond between the two rings. Consequently, the methyl carboxyl-ate substituents are oriented in a trans fashion with regards to the bond between the benzene rings. The methyl carboxyl-ate and meth-oxy substituents are rotated slightly out of plane relative to their parent benzene rings, with dihedral and torsion angles of 18.52 (8) and -5.22 (15)°, respectively. The shortest O⋯H contact between neighbouring mol-ecules is about 2.5 Å. Although some structure-directing contributions from C-H⋯O hydrogen-bonding inter-actions are possible, the crystal packing seems primarily directed by weak van der Waals forces.

4,4'-Dimeth-oxybi-phenyl-3,3'-di-car-box-ylic acid.

The title compound, C16H14O6, was recrystallized under solvothermal conditions. The mol-ecules are located on inversion centres, with one complete mol-ecule generated from the asymmetric unit by inversion. There are intra-molecular O-H⋯O hydrogen bonds involving the carb-oxy-lic acid group and the O atom of the adjacent meth-oxy group. In the crystal, mol-ecules are linked via O-H⋯O hydrogen bonds, forming chains propagating along [100]. The chains are linked via C-H⋯O hydrogen bonds, forming sheets parallel to (001).

Dimethyl 3,3'-di-meth-oxy-biphenyl-4,4'-di-carboxyl-ate.

In the title compound, C18H18O6, the biphenyl moiety is twisted with a dihedral angle of 29.11 (10)°. The carbometh-oxy groups form C-C-C-O torsion angles of -18.3 (3) and -27.7 (3)° with the attached rings, as a result of steric hindrances from the nearby meth-oxy groups. In the absence of stacking inter-actions and with no H⋯O contacts shorter than 2.7 Å, the packing is dominated by weaker van der Waals inter-actions.

Methyl 5-iodo-2-meth-oxy-benzoate.

In the title compound, C9H9IO3, the mol-ecules are close to planar [maximum deviation from benzene ring plane = 0.229 (5) Šfor the methyl carboxylate C atom] with the methyl groups oriented away from each other. In the crystal, mol-ecules form stacked layers parallel to the ab plane, where every layer has either the iodine or meth-oxy/methyl carboxyl-ate substituents pointing towards each other in an alternating fashion.

(E)-9-(But-2-en-1-yl)-6-chloro-9H-purine.

The asymmetric unit of the title compound, C9H9ClN4, contains two mol-ecules. In the crystal, the mol-ecules are ordered in a chain-like fashion along the a axis, and form layers offset relative to the C plane by approximately 30°. This ordering does not, however, appear to be directed by classical hydrogen bonding.The allylic side chains of both independent mol-ecules are disordered, with occupancies of 0.870 (4) and 0.934 (3) for the major components. The disorder components represent two possible spatial orientations of the atoms around the C=C double bond.

(5,5'-Dimethyl-2,2'-bipyridine)-iodido-trimethyl-platinum(IV).

In the title compound, [Pt(CH(3))(3)I(C(12)H(12)N(2))], the Pt(IV) atom is six-coordinated in a slightly distorted octa-hedral configuration with one CH(3) group and the I atom forming a near perpendicular axis relative to the square plane formed by the bipyridine ligand and the two remaining CH(3) groups. The CH(3) group trans to the I atom has a slightly elongated bond to Pt compared to the other CH(3) groups, indicating a difference in trans influence between iodine and the bipyridine ligand.