An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The title compound, 4C9H6O6·C6H8N6·2H2O, crystallizes in a layer structure where each sheet is composed of anellated hydrogen-bonded rings of six distinct sizes: R22(16), R33(18), R44(12), R44(18), R44(22) and R44(25). The two largest rings, viz. R44(22) and R44(25), are associated with O—H⋯N bonds from the carboxyl groups to the triazole rings. The typical head-to-tail carboxyl–carboxyl R22(8) motif is not observed.
The palladium(II) complex [Pd(C6F5)Cl(bpzm*)] (5) [bpzm* = bis(3,5-dimethylpyrazol-1-yl)methane] was characterized by 1H,1H-TOCSY, 1H-NOE difference spectra, 1H,19F-HOESY and 13C,1H-HMBC 2D-NMR techniques. Chemical exchange of the methylene protons from 1H,1H-NOESY cross peaks and exchange of the ortho- and meta-fluorine atoms, respectively, from 19F,19F-EXSY cross peaks indicates that the Pd-bpzm* chelate ring boat-to-boat inversion occurs at a rate slower than the NMR time scale together with a concomitant change of the C6F5 atom positions. The presence of three 19F-NMR signals for 2Fo : 1Fp : 2Fm of the C6F5 ligand for complexes [Pd(C6F5)Cl(tmeda)] (1) and [Pd(C6F5)Cl(bipy)] (3) (tmeda = N,N,N′,N′-tetramethylethylenediamine; bipy = 2,2′-bipyridine) is interpreted as being due to identical hemi-spaces above and below an apparent symmetry plane coinciding with the Pd-coordination plane instead of free ring rotation. The molecular structures of 1, 3 and 5 from single-crystal studies suggest that the hindered C6F5 rotation is not limited to 5 but is also present in 1 and 3 due to ligand repulsion. Complexes [Pd(C6F5)Cl(tmeda)] (1), [Pd(C6F5)OH(tmeda)] (2), [Pd(C6F5)Cl(bipy)] (3), [Pd(C6F5)OH(bipy)] (4) and [Pd(C6F5)Cl(bpzm*)] (5) have been applied as pre-catalysts for the vinyl homopolymerization of norbornene in combination with the cocatalyst methylaluminoxane (MAO). Activities of more than 106 gpolymer/(molPd h) could be reached with these catalytic systems. Based on the spectrochemical series, pre-catalysts 1 and 2 with the pure σ-donor and more weakly bound aliphatic amine ligands showed higher polymerization activities than compounds 3–5 with modest π-accepting and stronger bound aromatic substituents. This is reasoned with a kinetic activation effect through a faster removal of the more weakly bound ligands upon reaction with MAO together with the chloro or hydroxo ligands to give the active, almost "naked" Pd2+ cations. For the activation mechanism, 1H-, 13C- and 19F-NMR studies of the MAO activated complex 5 showed about 13% chlorine-to-methyl exchange for a molar Pd : Al ratio of 1 : 10. For 5 : MAO at a Pd : Al ratio of 1 : 100 abstraction of C6F5 takes place with a redox reaction giving Pd metal and C6F5-CH3 in the absence of norbornene monomer.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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