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31.
Carlo Mealli Stefano Midollini Simonetta Moneti Thomas A. Albright 《Helvetica chimica acta》1983,66(2):557-569
The reaction of [(C3Ph3)Ni(PPh3)2]ClO4 with P(CH2CH2PPh2)3(pp3) and NaBPh4 yields the [(C3Ph3)Ni(pp3)]BPh4-complex. After long exposure of the solution of this compound in acetone/butanol to the air a new derivative [(C3Ph3)-Ni(pp2po)]BPh4· 0.5 C4H9OH, where pp2po is (Ph2PCH2CH2)2P(CH2 CH2POPh2), is obtained. Complete X-ray analysis has been carried out for the latter complex: a=18.303 (5); b=29.445 (6), c=13.305 (5) Å, β=112.70 (9)°; space group monoclinic, P21/a, Z=4. Disorder problems were encountered in the refinement of the structure. The best R is 0.093. One of the arms of the parent pp3-molecule, not coordinated to the metal, undergoes oxidation. The Ni-atom, coordinated by the three remaining P-atoms of the ligand, is also linked in a roughly η3-mode to the cyclopropenium ligand. The geometry of the molecule is examined in detail. Extended HMO-calculations were performed to interpret how the variation of P? Ni? P angles affects the bonding between the NiP3- and C3H3-fragments. The conclusion is that the overall energy of the complex may be lowered in spite of a weakening of the Ni-cyclopropenium linkage. Extensions are made to other systems containing a linkage between a metal and a X3-ring (X=P,As). 相似文献
32.
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34.
Riccò M Shiroka T Carretta S Bolzoni F Femoni C Iapalucci MC Longoni G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(9):2856-2861
The magnetic behaviour of the even-electron [Ni16Pd16(CO)40]4- cluster, in its [NnBu4]+ salt, has been investigated by magnetometry and muon spin rotation/relaxation (muSR) spectroscopy. The susceptibility measurements show an exceptionally high magnetic moment corresponding to a total spin value J=2. This suggests a Hund filling of a quadruplet ground state, quite unique in carbonyl-metal clusters. SQUID magnetometry shows a departure from the Curie-Weiss law, for T>150 K, and strong deviation from a Brillouin behaviour of the magnetisation curves. muSR spectroscopy in zero applied field shows a temperature independent decay of the muon spin polarisation, similar to that of a purely paramagnetic system. The observed muon spin repolarisation in a moderate external longitudinal field, however, invalidates this simple picture and suggests the presence of a local anisotropy field acting on the cluster's magnetic moment. A consistent interpretation of magnetometry and muSR results implies the occurrence of an additional interaction of the cluster spin with an effective crystalline field. The inclusion of this interaction in a model Hamiltonian allows us to successfully reproduce both the susceptibility and magnetisation data. 相似文献
35.
The low-temperature NMR spectra of 1,4-bis(mesitoyl)durene, 1, and of 1,4-bis(mesitylethenyl)durene, 2, reveal the presence of syn and anti rotamers at the equilibrium, their relative proportions depending on the dielectric constant of the solvent. In solution the more stable rotamer of 1 is the anti whereas, in the case of 2, the more stable is the syn. Depending on the crystallization solvent employed the more (anti) and the less stable (syn) rotamers were both observed (X-ray diffraction) in the solid state of 1. On the other hand, only the less stable rotamer (anti) was found to be present in the solid state of 2. As shown by MM calculations, the syn-to-anti interconversion occurs via a correlated process (cogwheel pathway) involving the mesityl-C and durene-C bond rotations: the dynamic NMR technique yields an experimental barrier of 8.2 kcal mol(-)(1) for 1 and 13.1 kcal mol(-)(1) for 2. In the case of derivative 2 a second barrier, due to a second type of correlated rotation process (torsion), was also determined (8.6 kcal mol(-)(1)). As a consequence of the restriction of this second torsional motion the anti rotamer of 2 displays two distinguishable NMR spectra at -133 degrees C, corresponding to a pair of conformers with different symmetry (anti C(i)() and anti C(2)). 相似文献
36.
Alessandro?De?Robertis Concetta?De?Stefano Demetrio?Milea Silvio?SammartanoEmail author 《Journal of solution chemistry》2005,34(10):1211-1226
Complex formation constants were determined potentiometrically (by a ISE-H+, glass electrode) in the systems, M2+ – Lz – H+ [M2+ = (C2H5)2Sn2+, Lz = malonate, glycinate and ethylenediamine] at t = 25 ∘C and 0.1 mol-L−1≤ I/ ≤ 1 mol-L−1 in NaClaq (0.1 mol-L−1 ≤ I ≤ 0.75 mol-L−1 for the ethylenediamine system). Thermodynamic values of formation constants, at infinite dilution, are [± 95% confidence
interval, Tβpqr refer to the equilibrium, pM2+ + qLz + rH+ = MpLqHr(2+z+r)]: for malonate, log10 Tβ110 = (5.47 ± 0.10); for glycinate, log10 Tβ110 = (9.54 ± 0.08), log10 Tβ111 = (12.97 ± 0.10); and for ethylenediamine, log10 Tβ110 = (10.47 ± 0.10), log10 Tβ120 = (16.17 ± 0.12) and log10 Tβ111 = (15.46 ± 0.10). The dependence on ionic strength of the formation constants was modeled by a simple Debye–Hückel type equation
and by the SIT approach. By analyzing the stability of the species in the three different systems we found a simple additivity
rule that can be expressed by the relationship: log10 K = 6.46 nN + 3.96 nO − 0.60 (nN2+ nO2), with a mean deviation, ε(log10 K) = 0.15 (K = equilibrium constant for the interaction of the organometal cation with the unprotonated or protonated ligand, nN = number of amino groups and nO = number of carboxylic groups of the ligand(s) involved in the formation reaction of complex species). 相似文献
37.
38.
Jos L. Del Valle Cecilia Polo TomS Torroba Stefano Marcaccini 《Journal of heterocyclic chemistry》1995,32(3):899-901
The sodium salt of TOSMIC reacted with (E)-3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-C-nitro-D-galacto- (1) and -D-manno-hept-1-enitol (2) to give 3-(D-galacto- (3) and 3-(D-manno-penta-O-acetylpentitol-1-yl)-4-nitropyrrole (4) , respectively. Compound 1 reacted with diaryl nitrile imines, affording 1,3-diaryl-4-(1,2,3,4,5-penta-O-acetyl-D-galacto-pentitol-1-yl)pyrazoles 5 and 6 . 相似文献
39.
The carotenoid triplet populations associated with the long-wavelength-emitting chlorophyll forms of photosystem I (PS I)(dagger) have been investigated in isolated spinach thylakoids by means of fluorescence-detected magnetic resonance in zero field. The spectra collected in the 730-800 nm emission range can be globally fitted assuming the presence of four different carotenoid triplet states coupled to long-wavelength-emitting forms of PS I, having zero-field-splitting parameters /D/ = 0.0359 cm(-1) and /E/ = 0.00371 cm(-1), /D/ = 0.0382 cm(-1) and /E/ = 0.00388 cm(-1), /D/ = 0.0395 cm(-1) and /E/ = 0.00397 cm(-1), and /D/ = 0.0405 cm(-1) and /E/ = 0.00411 cm(-1). On the basis of the triplet-associated fluorescence emission profile, it is suggested that those triplets are associated with light-harvesting complex I, the peripheral antenna complex of PS I. 相似文献
40.
Mandrioli R Musenga A Ferranti A Lasaponara SS Fanali S Raggi MA 《Journal of separation science》2005,28(9-10):966-972
A micellar electrokinetic chromatographic method was developed and applied for the first time to the separation and quantification of the main components of cloves, namely eugenol and beta-caryophyllene. The analytes were separated in less than ten minutes in an unmodified fused silica capillary (effective length: 40.0 cm) using a background electrolyte composed of 25 mM carbonate buffer (pH 10.0) and 60 mM sodium dodecylsulfate. Analyte concentrations were determined in clove oil and in methanolic clove extracts after simple sequential dilution with methanol and background electrolyte, and the resulting electropherograms showed no interference due to other components. Precision assays gave satisfactory results, with mean standard deviation of peak areas lower than 4.7% (lower than 1.5% for migration times). The eugenol content of a commercial clove oil was about 70% (RSD% = 3.2), while that of beta-caryophyllene was about 15% (RSD% = 4.2); in clove extracts, on the other hand, eugenol was approximately 15% (RSD% = 4.7) and beta-caryophyllene 4% (RSD% = 5.1). Accuracy was also good (mean recovery >98%). 相似文献