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1.
The preparation and structural characterization of {Ru 3(CO) 11} 2(1,4-bis(diphenylphosphino)benzene), a modified synthesis of 1,4-bis(diphenylphosphino)benzene, and the structural characterization of {Ru 3(CO) 11} 2(bis(diphenylphosphino)ethane) are reported. In both compounds two metal cluster units are connected through ditertiary-phosphine ligands. Both molecules consist of centrosymmetric units in which the diphosphine ligands are largely covered by the triangular ruthenium clusters. No direct interaction between the two cluster units occurs within individual molecules. Molecular packing in the solid state is dominated by interactions between sets of carbon monoxide ligands in motifs that were previously identified in the solid state structure of the parent cluster, Ru 3(CO) 12. 相似文献
2.
A new compound containing a cubane tungsten chalcogenide cluster [W 4(μ 3-Te) 4(CN) 12] 6− and Ca 2+ complex units has been prepared by the reaction of aqueous solution of K 6[W 4(μ 3-Te) 4(CN) 12] · 5H 2O with the solution of a Ca(NO 3) 2 and phen(1,10-phenanthroline) (1:2 molar ratio) in a solvent mixture of H 2O/EtOH. The structure of [{Ca(phen) 2(H 2O)}{Ca(phen)(H 2O) 4}{Ca(phen) 2(H 2O) 3}][W 4Te 4(CN) 12] · 5H 2O 1 has been determined by X-ray crystallography. Compound 1 contains [{Ca(phen)(H 2O) 4}{Ca(phen) 2(H 2O) 3}][W 4(μ 3- Te) 4(CN) 12] units bridged by {Ca(phen) 2(H 2O)} 2+ units to form an one-dimensional zigzag chain structure. Interestingly, compound 1 showed a heterogeneous catalytic activity in the transesterification of a range of esters with methanol under the mild conditions. Moreover, it can be reused without any loss of activity through 10 runs with ester. 相似文献
3.
The new organometallic cluster (η 2-μ 4-CO) 2(CO) 13(η 6-C 6Me 6) has been prepared by the thermolysis of Ru 3(CO) 12 with hexamethylbenzene in octane and characterised by a single crystal X-ray diffraction study. It is isostructural with the known cluster Ru 6(η 2-μ 4-CO) 2(CO) 13(η 6-C 6H 3Me 3) and the metal core constitutnts the same tetrahedral Ru 4 unit with two edge-bridging Ru atoms. The mesitylene derivative has been shown to undergo rearrangement to afford the octahedral carbido cluster Ru 6C(CO) 14(η 6-C 6H 3Me 3), but this conversion is not observed for the new hexamethylbenzene derivative. 相似文献
4.
The phosphinoalkenes Ph 2P(CH 2) nCH=CH 2 ( n= 1, 2, 3) and phosphinoalkynes Ph 2P(CH 2) n C≡CR (R = H, N = 2, 3; R = CH 3, N = 1) have been prepared and reacted with the dirhodium complex (η−C 5H 5) 2Rh 2(μ−CO) (μ−η 2−CF 3C 2CF 3). Six new complexes of the type (ν−C 5H 5) 2(Rh 2(CO) (μ−η 1:η 1−CF 3C 2CF 3)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH 3C 5H 4)Mn(CO) 2thf resulted in coordination of the manganese to the alkene function. The Rh 2---Mn complex [(η−C 5H 5) 2Rh 2(CO) (μ−η 1:η 1−CF 3C 2CF 3) {Ph 2P(CH 2) 3CH=CH 2} (η−CH 3C 5H 4)Mn(CO) 2] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co 2(CO) 8 resulted in the coordination of Co 2(CO) 6 to the alkyne function. The Rh 2---Co 2 complex [(η−C 5H 5) 2Rh 2(CO) (μ−η 1:η 1−CF 3C 2CF 3) {Ph 2PCH 2C≡CCH 3}Co 2(CO) 2], C 37H 25Co 2F 6O 7PRh 2, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group
( Ci1, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on | F| was 0.052 fo observed ( I > 3σ( I)) reflections. The Rh 2 and Co 2 parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh 2 and perpendicular for Co 2. Attempts to induce Rh 2Co 2 cluster formation were unsuccessful. 相似文献
5.
Trekking and military missions generally consist of carrying heavy loads for extreme durations. These factors have been separately shown to be sources of neuromuscular (NM) fatigue and locomotor alterations. However, the question of their combined effects remains unresolved, and addressing this issue required a representative context. PurposeThe aim was to investigate the effects of extreme-duration heavy load carriage on NM function and walking characteristics. MethodsTen experienced infantrymen performed a 21-h simulated military mission (SMM) in a middle-mountain environment with equipment weighing ∼27 kg during battles and ∼43 kg during marches. NM function was evaluated for knee extensors (KE) and plantar flexors (PF) pre- and immediately post-SMM using isometric maximal voluntary contraction (MVC) measurement, neural electrical stimulation and surface EMG. The twitch-interpolation method was used to assess central fatigue. Peripheral changes were examined by stimulating the muscle in the relaxed state. The energy cost, mechanical work and spatio-temporal pattern of walking were also evaluated pre−/post-SMM on an instrumented treadmill in three equipment conditions: Sportswear, Battle and March. ResultsAfter the SMM, MVC declined by −10.2±3.6% for KE ( P<0.01) and −10.7±16.1% for PF ( P = 0.06). The origin of fatigue was essentially peripheral for both muscle groups. A trend toward low-frequency fatigue was detected for KE (5.5%, P = 0.08). These moderate NM alterations were concomitant with a large increase in perceived fatigue from pre- (rating of 8.3±2.2) to post-SMM (15.9±2.1, P<0.01). The SMM-related fatigue did not alter walking energetics or mechanics, and the different equipment carried on the treadmill did not interact with this fatigue either. Conclusionthis study reports the first data on physiological and biomechanical consequences of extreme-duration heavy load carriage. Unexpectedly, NM function alterations due to the 21-h SMM were moderate and did not alter walking characteristics. Clinical Trial Registration
Name: Effect of prolonged military exercises with high load carriage on neuromuscular fatigue and physiological/biomechanical responses. Number: {"type":"clinical-trial","attrs":{"text":"NCT01127191","term_id":"NCT01127191"}}NCT01127191. 相似文献
6.
BackgroundTo investigate the cause/s of muscle fatigue experienced during a half-iron distance triathlon. Methodology/Principal FindingsWe recruited 25 trained triathletes (36±7 yr; 75.1±9.8 kg) for the study. Before and just after the race, jump height and leg muscle power output were measured during a countermovement jump on a force platform to determine leg muscle fatigue. Body weight, handgrip maximal force and blood and urine samples were also obtained before and after the race. Blood myoglobin and creatine kinase concentrations were determined as markers of muscle damage. ResultsJump height (from 30.3±5.0 to 23.4±6.4 cm; P<0.05) and leg power output (from 25.6±2.9 to 20.7±4.6 W · kg −1; P<0.05) were significantly reduced after the race. However, handgrip maximal force was unaffected by the race (430±59 to 430±62 N). Mean dehydration after the race was 2.3±1.2% with high inter-individual variability in the responses. Blood myoglobin and creatine kinase concentration increased to 516±248 µg · L −1 and 442±204 U · L −1, respectively ( P<0.05) after the race. Pre- to post-race jump change did not correlate with dehydration (r = 0.16; P>0.05) but significantly correlated with myoglobin concentration (r = 0.65; P<0.001) and creatine kinase concentration (r = 0.54; P<0.001). Conclusions/significanceDuring a half-iron distance triathlon, the capacity of leg muscles to produce force was notably diminished while arm muscle force output remained unaffected. Leg muscle fatigue was correlated with blood markers of muscle damage suggesting that muscle breakdown is one of the most relevant sources of muscle fatigue during a triathlon. 相似文献
7.
Two new copper(II) complexes, Cu(L1)(ClO 4) 2 (1), {[(μ-oxalate)Cu(L1)] · 5H 2O} n (2), and a zinc(II) complex, {[(μ-oxalate)Zn(L2)] · 3H 2O · 0.5DMF} n (3) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0 1.18,0 7.12]docosane), have been synthesized and characterized by X-ray crystallography. In 1, the ligand conformation is planar, and the octahedral coordination about the copper(II) ion is completed by weakly interacting ions. In 2 and 3, bridging oxalate ligands coordinate to copper(II) or zinc(II) ions in an unusually twisted bis-monodentate ( trans-1,1′-bicoordination) mode. The rigidity and steric hindrance of macrocycles L1 and L2 by the introduction of two cyclohexane rings and methyl groups on a cyclam (1,4,8,11-tetraazacyclotetradecane) skeleton cause the bridging oxalate ligands to adopt such unusual geometries in 2 and 3. 相似文献
8.
The dialkyl-μ-ethylidene-μ-methylene-bis (pentamethylcyclopentadienyl)-dirhodium complexes [{(C 5Me 5)Rh} 2(μ-CH 2)(μ-CHMe) (R) 2] (4, P=Me; 5, Et; 6, n-Bu; 7, CH=CH 2; and 8, Z-CH=CHMe) have been prepared from RMgBr and [{(C 5Me 5)Rh} 2(μ-CH 2)(μ-CHMe)(X) 2] (2, X=Cl; 3, X=Br). Structures deduced from the NMR spectra show that the dialkyl complexes can exist in one trans and two cis forms. The decomposition of the dimethyl complex 4 is compared with that of the related di-μ-methylene complex; it reacts readily (30°C, MeCN solution) in the presence of one-electron oxidisers to give propene and methane and a little ethene and some butenes. Mass-spectrometric analysis of the 13C labelling in the organics originating from [{(C 5Me 5)Rh} 2(μ-CH 2)(μ-CHMe) ( 13CH 3) 2] shows that methane derives from the Rh---Me, ethene half from the ethylidene and half from coupling of Rh-methyl and a bridging methylene, while the propene arises almost entirely from the ethylidene and a rhodium methyl. The butenes come from coupling of ethylidene, methylene and a Rh-methyl, but only quite small amounts are formed; thus C+C coupling is the major decomposition path for the μ-ethylidenes, in contrast to the di-μ-methylene complexes where C+C+C coupling predominates. The divinyl complex [{(C 5Me 5)Rh} 2(μ-CH 2)(μ-CHMe) (CH=CH 2) 2] also underwent internal C+C coupling on reaction with AgBF 4 in MeCN to give a mixture of the allyl and methylallyl cations [(C 5Me 5)Rh(η 3-CH 2CHCHR)(MeCN)] +(10, R=H; 11, R=Me). 相似文献
9.
The lithiation of indole, using a slight excess of n-butyl lithium in THF, followed by methylation and reaction with [Cr(CO) 6] in refluxing dibutyl ether, resulted in the formation of [Cr(η 6- N-methylindole)(CO) 3] (1a) and [Cr(η 6- N-methyl-2-methylindole)(CO) 3] (1b). In contrast, lithiation of quinoline in THF, silylation and the subsequent reaction with [Cr(CO) 6] under similar reaction conditions, afforded [Cr(η 6- N-trimethylsilyl-2-butyl-1,2-dihydroquinoline)(CO) 3] (2) and [Cr(η 6-{2-butyl-1,2,3,4-tetrahydroquinoline})(CO) 3] (3). The formation of [Cr(η 6-2,2′-bis{ N-methylindolyl})(CO) 3] (4) implied lithiation at the 2-position of 1a. However, metallation at the 7-position was also indicated during the same reaction. In the presence of [Mn(CO) 5Br], product 4 and the transmetallation product [Cr(η 6-{7-( N-methylindolyl)Mn(CO) 5})(CO) 3] (5) were isolated. Reaction with titanocene dichloride gave [Cr(η 6-{2-( N-methylindolyl)TiCp 2Cl})(CO) 3] (6), which slowly converted into [TiCp 2{Cr(η 6-2-( N-methylindolyl)(CO) 3} 2] (7). 相似文献
10.
Ketenylidenetriphenylphosphorane, Ph 3PC=C=O, 1, has been used to synthesize platinum-substituted ketenes [PtMe{η 1-C(PPh 3)CO}L 2]BF 4, 2a, b (L 2=1,5-cyclooctadiene, cod (a), 1,2-bis(diphenylphosphino)ethane, diphos (b)). Parent compound [PtCl{η 1-C(PPh 3)CO}L 2]BF 4, 3, with L 2= cis-1,2-bis(diphenylphosphino)ethene, diphoe, was also synthesized, which is stable only at low temperature. The stability of 2 and 3 and the reactivity of the C=C=O moiety have been examined and discussed in terms of the electronic and steric characteristics of the ancillary ligands, also taking into account the reactivity of the ‘PtXL 2’ fragment with other carbonyl stabilized phosphorus ylides, Ph 3PCHCOR (R=Me, Ph, OMe, OEt). 相似文献
11.
BackgroundReduced CD4 T lymphocytes counts can be observed in HIV infection and in patients undergoing autologous haematopoietic stem cell transplantation (ASCT). Nevertheless, whereas opportunistic infections (OI) are frequent in HIV-infected individuals with low cell counts, OI are uncommon in ASCT patients. Methodology/Principal FindingsTo verify whether this observation could be secondary to intrinsic HIV-correlated T cell defects, we performed in-depth immunologic analyses in 10 patients with comparable CD4 counts in whom lymphopenia was secondary either to HIV-infection or ASCT-associated immunosuppressive therapy and compared them to age-matched healthy subjects. Results showed the presence of profound alterations in CD4+ T lymphocytes in both groups of patients with respect to healthy controls. Thus, a low percentage of CCR7+ CD4+ T cells and a compensative expansion of CD45RA−CCR7− CD4+ T cells, a reduced IL-2/IFN-γ cytokine production and impaired recall antigens-specific proliferative responses were detected both in ASCT and HIV patients. In stark contrast, profound differences were detected in CD8+ T-cells between the two groups of patients. Thus, mature CD8+ T cell prevailed in ASCT patients in whom significantly lower CD45RA−CCR7− cells, higher CD45RA+CCR7− CD8+ cells, and an expansion of CCR7+CD8+ cells was detected; this resulted in higher IFN-γ +/TNFα production and granzyme CD8+ expression. The presence of strong CD8 T cells mediated immune responses justifies the more favorable clinical outcome of ASCT compared to HIV patients. Conclusion/SignificanceThese results indicate that CD8 T cells maturation and functions can be observed even in the face of a profound impairment of CD4+ T lymphocytes in ASCT but not in HIV patients. Primary HIV-associated CD8 defects or an imprinting by an intact CD4 T cell system in ASCT could justify these results. 相似文献
12.
Myasthenia gravis has variable effects on the respiratory system, ranging from no abnormalities to life-threatening respiratory failure. Studies characterized diaphragm muscle contractile performance in rat autoimmune myasthenia gravis. Rats received monoclonal antibody that recognizes acetylcholine receptor determinants (or inactive antibody); 3 days later, phrenic nerve and diaphragm were studied in vitro. Myasthenic rats segregated into two groups, those with normal vs. impaired limb muscle function when tested in intact animals ("mild" and "severe" myasthenic). Baseline diaphragm twitch force was reduced for both severe (P < 0.01) and mild (P < 0.05) myasthenic compared with control animals (twitch force: normal 1,352 +/- 140, mild myasthenic 672 +/- 99, severe myasthenic 687 +/- 74 g/cm2). However, only severe myasthenic diaphragm had impaired diaphragm endurance, based on significantly (P < 0.05) accelerated rate of peak force decline during the initial period of stimulation (0.02 + 0.02, 0.03 +/- 0.01, and 0.09 +/- 0.01%/pulse for normal, mild myasthenic, and severe myasthenic, respectively, during continuous stimulation) and intratrain fatigue (up to 30.5 +/- 7.4% intratrain force drop in severe myasthenic vs. none in normal and mild myasthenic, P < 0.01). Furthermore, compared with continuous stimulation, intermittent stimulation had a protective effect on force of severe myasthenic diaphragm (force after 2,000 pulses was 31.4 +/- 2.0% of initial during intermittent stimulation vs. 13.0 +/- 2.1% of initial during continuous stimulation, P < 0.01) but not on normal diaphragm. These data indicate that baseline force and fatigue may be affected to different extents by varying severity of myasthenia gravis and furthermore provide a mechanism by which alterations in breathing pattern may worsen respiratory muscle function in neuromuscular diseases. 相似文献
13.
A new steroidal glycoside, agaveside D, isolated from the fruits of Agave cantata was characterized as 3β-{-
-rhamnopyranosyl-(1→2), β-
-glycopyranosyl-(1→3)-β-
-glucopyranosyl[β-
-xylopyransoyl-(1→4)--
-rhamnopyranosyl-(1→2)]-β-
-glucopyranosyl}-25 R-5- spirostane on the basis of chemical degradation and spectrometry. 相似文献
14.
HRu 2Fe 2PdC(CO) 12 (η 3-ß-C 10H 15) cluster was prepared in the reaction of (Et 4N) [HFe 2Ru 2C(CO) 12] with [Pd(η 3-ß-C 10H 15)Cl] 2. X-ray structural study of HRu 2Fe 2PdC(CO) 12 (η 3-ß-C 10H 15) (where ß-C 10H 15 is ß-pinenyl) revealed a wing-tip butterfly geometry of the metal core and (1R, 2S, 3S, 5R) absolute configuration for both crystallography independent molecules in the crystal. Chiroptical properties of this cluster are compared with other clusters containing a Pd(η 3-ß-C 10H 15) fragment and discussed. 相似文献
15.
BackgroundPerceptual illusions play an important role in untangling neural mechanisms underlying conscious phenomena. The thermal grill illusion (TGI) has been suggested as a promising model for exploring percepts involved in neuropathic pain, such as cold-allodynia (pain arising from contact with innocuous cold). The TGI is an unpleasant/painful sensation from touching juxtapositioned bars of cold and warm innocuous temperatures. AimTo develop an MRI-compatible TGI-unit and explore the supraspinal correlates of the illusion, using fMRI, in a group of healthy volunteers. MethodsWe constructed a TGI-thermode allowing the rapid presentation of warm(41°C), cold(18°C) and interleaved(41°C+18°C = TGI) temperatures in an fMRI-environment. Twenty volunteers were tested. The affective-motivational (“unpleasantness”) and sensory-disciminatory (“pain-intensity”) dimensions of each respective stimulus were rated. Functional images were analyzed at a corrected α-level <0.05. ResultsThe TGI was rated as significantly more unpleasant and painful than stimulation with each of its constituent temperatures. Also, the TGI was rated as significantly more unpleasant than painful. Thermal stimulation versus neutral baseline revealed bilateral activations of the anterior insulae and fronto-parietal regions. Unlike its constituent temperatures the TGI displayed a strong activation of the right (contralateral) thalamus. Exploratory contrasts at a slightly more liberal threshold-level also revealed a TGI-activation of the right mid/anterior insula, correlating with ratings of unpleasantness(rho = 0.31). Conclusion/SignificanceTo the best of our knowledge, this is the first fMRI-study of the TGI. The activation of the anterior insula is consistent with this region''s putative role in processing of homeostatically relevant feeling-states. Our results constitute the first neurophysiologic evidence of thalamic involvement in the TGI. Similar thalamic activity has previously been observed during evoked cold-allodynia in patients with central neuropathic pain. Our results further the understanding of the supraspinal correlates of the TGI-phenomenon and pave the way for future inquiries into if and how it may relate to neuropathic pain. 相似文献
16.
The reaction of thiamine with K 2Pt IICl 4 and with Pt IVCl 4 in the presence of excess NaSCN in aqueous solution gave thiamine salts, (H-thiamine)[Pt(SCN) 4] · 3H 2O (1) and (H-thiamine)[Pt(SCN) 6] · H 2O (2), respectively, structures of which have been determined by X-ray diffraction. The thiamine molecule adopts the usual F conformation in each salt. In 1, [Pt(SCN) 4] 2− ions act as large planar spacers in the crystal lattice and interact scarcely with thiamine, except for a hydrogen bonding with the terminal hydroxy O(5 γ). Instead, water molecules form two types of host–guest-like interactions with the pyrimidine and the thiazolium moieties of a thiamine molecule, one being a C(2)–Hwaterpyrimidine bridge and the other being an N(4′)–Hwaterthiazolium bridge. In 2, despite the much larger ion size, octahedral [Pt(SCN) 6] 2− ions form a C(2)–Hanionpyrimidine bridge and an N(4′)–Hanionthiazolium bridge. An additional hydrogen bonding between the anion and the terminal O(5γ) of thiamine creates a hydrogen-bonded macrocyclic ring {thiaminium–[Pt(SCN) 6] 2−} 2, a supramolecule. 相似文献
17.
The aim of this work is to examine the possible interaction and extent thereof of the polysaccharide galactomannan (GAL) with the cereal protein gliadin (GLI) and a peptic-tryptic degraded gliadin (PT-GLI) by analytical ultracentrifugation. The work is part of a series of investigations into the field of coeliac disease (gluten-induced enteropathy) as gliadins are known to be toxic for patients with this disease. The molecular integrity of the GAL and GLI preparations was first checked by sedimentation velocity and sedimentation equilibrium. Sedimentation velocity showed single boundaries indicating homogeneity and low-speed sedimentation equilibrium gave plausible apparent weight average molar masses of 180,000 g/ mol for GAL and 20,000 g/mol for GLI. PT-GLI, GLI and GAL in phosphate buffer (pH 6.5) and the incubated mixtures (stirred for 3 h at 37 °C; PT-GLI: GAL = 3.53:1, wt.wt.; GLI:GAL = 0.23 and 0.55:1, wt.wt.) were then investigated by sedimentation velocity at a temperature of 20 °C. The plots of 1/s20 vs. c of GAL, PT-GLI-GAL and GLI-GAL mixtures after incubation show a significantly different shape suggesting the presence of interactions. According to the equation 1/s20 = 1/so20(1 + ksc), values for {so20, ks} of {(4.02 ± (490.9 ± 28.9) ml/g, {(5.92 ± 0.24) S, (1152 ± 44) ml/g} and {(5.38 ± 0.19) S, (1141 ± 38) ml/g} for GAL and PT-GLI-GAL and GLI-GAL mixtures, respectively, were obtained. The concentration of GAL ranged from 0.75–3.0 mg/ml for GAL alone and from 0.34–1.50 mg/ml in the incubated mixtures. This apparent indication for a weak non-covalent protein-polysaccharide interaction was further supported by UV absorption spectrometry and gel filtration. 相似文献
18.
Layer-by-layer assembly of glucose oxidase (GOx) with single-wall carbon nanotubes (SWCNTs) is achieved on the electrode surface based on the electrostatic attraction between positively charged GOx in pH 3.8 buffer and negatively charged carboxylic groups of CNTs. The cyclic voltammetry and electrochemical impedance spectroscopy are used to characterize the formation of multilayer films. In deaerated buffer solutions, the cyclic voltammetry of the multilayer films of {GOx/CNT} n shows two pairs of well-behaved redox peaks that are assigned to the redox reactions of CNTs and GOx, respectively, confirming the effective immobilization of GOx on CNTs using the layer-by-layer technique. The redox peak currents of GOx increase linearly with the increased number of layers indicating the uniform growth of GOx in multilayer films. The dependence of the cyclic voltammetric response of GOx in multilayer films on the scan rate and pH is also studied. A linear decrease of the reduction current of oxygen at the {GOx/CNT}-modified electrodes with the addition of glucose suggests that such multilayer films of GOx retain the bioactivity and can be used as reagentless glucose biosensors. 相似文献
19.
The reaction between the linear trinuclear complex [Pt{Fe(CO) 3(NO)} 2(PhCN) 2] and Ph 2(2-C 5H 4N)PSe led to the isolation and characterization of the 46-electron cluster [(CO) 3Fe(μ 3-Se){Pt(CO)P(2-C 5H 4N)Ph 2} 2] (1), whose structure has been determined by X-ray diffraction methods. The cluster typology, which consists of an open triangle Pt---Fe---Pt capped by a μ 3-Se atom, is rather rare. The chemical bonding in 1 and in similar systems has been analyzed through density functional theory (DFT) and qualitative MO approaches. A strict analogy with the well understood L 2M(μ-acetylene)ML 2 systems is invoked by considering 1 as formed by the (CO) 3FeSe tetrahedral unit stabilized by sidewise interactions of the triple bond with two d 10-L 2M fragments. Otherwise, the 18-electron (CO) 3FeSe monomer is unstable as an isolate molecule. This is confirmed by our DFT calculations that indicate how the well characterized dimer (CO) 3Fe(μ-Se 2)Fe(CO) 3 lies as much as, approximately, 58 kcal mol −1 deeper in energy. Finally, by considering an analogy with [L 2M(μ-dichalcogen)ML 2] 0, +2 redox systems (M=Pd, Pt), reduction of 1 to a dianion has been hypothesized and the structure of the latter has been tentatively explored by DFT calculations. 相似文献
20.
Reaction of [Au(η 2-Ar){CH 2C(O)R}Cl] (Ar=C 6H 4N=N- Ph- 2, R=Me, C 6H 2(OMe) 3-3′,4′,5′; Ar=C 6H 3(N=NC 6H 4Me- 4′)-2, Me-5, R=Me) with PPh 3 and NaClO 4·H 2O (1:2:1) at room temperature, leads to reductive elimination giving [Au(PPh 3) 2]ClO 4 and the corresponding carbon-carbon coupling product ArCH 2C(O)R. A similar process takes place when complexes [Au(η 2-Ar){CH 2C(O)R}(PPh 3)Cl] are refluxed in tetrahydrofuran, through elimination of [Au(PPh 3)Cl]. 相似文献
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