The stabilized phosphorus ylides, Ph3P=C(CO.R′)CO.OR; 1, R=Et, R′=CH2P+Ph3; 2, R=R′=Me; 3, R=Et, R′=Me; 4, R=Pri; R′=Me; 5, R=But; R′=Me, adopt a near planar conformation in the crystal which allows extensive electronic delocalization. The keto and alkoxylic oxygens are oriented and align favorably with the cationoid phosphorus. These conformations bring methyl hydrogens in the ester residue into proximity with the face of a phenyl group and lead to π-shielding and upfield shifts of the 1HNMR signals of 3 over a wide temperature range (-50–95°C) in (CD3)2CO, CDCl3 and DMSOd-6. Geometries of 2 and 3, optimized by using the HF 3-21 (G*) or 6-31 (G*) basis sets, are very similar to those in the crystal, but semiempirical treatments generate structures in which either the ester or keto moiety is twisted out of plane. 相似文献
The two isomorphous title structures, formulated as {[Co(C10H4O8)(C12H10N2)(H2O)2]·C12H10N2}n, (I), and {[Co(C10H4O8)(C12H12N2)(H2O)2]·C12H12N2}n, (II), respectively, are reported. They crystallize in the space group P with only one formula unit in the asymmetric unit, so that the organic ligands lie about inversion centres and the Co atom lies on an inversion centre. The Co atoms are octahedrally coordinated by a carboxylate O atom from 2,5‐dicarboxybenzene‐1,4‐dicarboxylate (H2btc), one N atom from 1,2‐di‐4‐pyridylethene (L) in (I) or from 1,2‐di‐4‐pyridylethane (L) in (II), and one coordinated water molecule, plus their inversion‐related species. This particular coordination results in a two‐dimensional array, with an elemental unit in the shape of a parallelogram having the CoII cations at the corners, linked in one direction by L bridges and in the opposite direction by H2btc groups. The L solvent molecules act as pillars between parallel planes, linking them by strong hydrogen bonds where the H atoms lie midway between the formal donor/acceptor atoms in a `shared' mode. Comparison is made with structures presenting the same structural motif, strongly suggesting that the two‐dimensional arrangement reported here might be a very stable robust building block for molecular engineering purposes. 相似文献
[Cp*Fe-dicyclopenta(a,f)naphthalene-FeCp*]n+ (Cp*=pentamethylciclopentadiene, n=0, 1), respectively named complexes V and VI, were synthesized and characterized. The X-ray structure has been solved and 1H-, 13C-NMR and elemental analysis were performed for the n=0 complex. Cyclic voltammetry showed a potential difference of 360 mV within the two redox peaks. An absorption band at 850 nm was assigned to an intervalence band. The Mössbauer investigations show a uniform Fe2+ environment for the neutral compound and two sites, assigned to Fe2+ and Fe3+ for the monoxidized compound. The information gathered by all the previously mentioned techniques indicates that the studied binuclear compound belongs to the mixed valence class II using Robin and Day classification. 相似文献
The title compound, [Cu(O2CCH=CHCH3)2(C5H5N)2(H2O)], crystallizes as a monomer, with the copper ion in a pentacoordinated square‐pyramidal environment, bisected by a twofold axis passing through the metal atom and the apex. The molecules organise in chains connected by hydrogen bonds running along the unique b axis. 相似文献
This paper reports on the electrodeposition of aluminium on several substrates from the air‐ and water‐stable ionic liquids 1‐propyl‐1‐methylpiperidinium bis(trifluoromethylsulfonyl)amide ([C3mpip][NTf2]) and 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][NTf2]), which contain anhydrous AlCl3. At an AlCl3 concentration of 0.75 molal, no evidence for aluminium electrodeposition was observed in either system at room temperature. However, aluminium electrodeposition becomes feasible upon heating the samples to 80 °C. Aluminium electrodeposition from bis(trifluoromethylsulfonyl)amide‐based ionic liquids that contain AlCl3 has previously been shown to be very dependent upon the AlCl3 concentration and has not been demonstrated at AlCl3 concentrations below 1.13 molal. The dissolution of AlCl3 in [C3mpip][NTf2] and [C4mpyr][NTf2] was studied by variable‐temperature 27Al NMR spectroscopy to gain insights on the electroactive species responsible for aluminium electrodeposition. A similar change in the aluminium speciation with temperature was observed in both ionic liquids, thereby indicating that the chemistry was similar in both. The electrodeposition of aluminium was shown to coincide with the formation of an asymmetric four‐coordinate aluminium‐containing species with an 27Al chemical shift of δ=94 and 92 ppm in the [C3mpip][NTf2]–AlCl3 and [C4mpyr][NTf2]–AlCl3 systems, respectively. It was concluded that the aluminium‐containing species that give rise to these resonances corresponds to the electroactive species and was assigned to [AlCl3(NTf2)]?. 相似文献
Calorimetry and signal processing : Vibrational spectroscopies, heat‐flow microcalorimetry, and multivariate analysis are combined to decouple the reaction enthalpies of parallel reactions (see picture). This methodology allows the evaluation of reaction enthalpy from complex systems without recourse to conventional kinetic modeling.