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31.
Let be the -valued process with independent Bessel components and with indices p and q strictly positive. In this paper we compute explicitly the law of the hitting time and place of a circle, centered at the origin, when starts from the center and deduce a Reuter-type independence result. We use mainly analytical tools from PDE theory. To cite this article: A. Ziadi, A. Bencherif-Madani, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
32.
Michael Knorr Pierre Braunstein Abdelatif Messaoudi Antonio Tiripicchio Franco Ugozzoli 《Journal of Cluster Science》2007,18(1):289-301
The reaction of the iron metalate [Fe{Si(OMe)3}(CO)3(dppm-P)]− (1b) with [Ru(CO)3Cl(μ-Cl)]2 afforded the heterodinuclear complex [(OC)3{(MeO)3Si}Fe(μ-dppm)Ru(CO)3Cl)] (Fe–Ru) (3) in which a long Fe–Ru separation of 2.956(1) ? has been crystallographically evidenced. It was shown by density functional
theory (DFT) calculations to correspond to the minimum-energy structure. Upon treatment of the corresponding hydrido complex
[HFe{Si(OMe)3}(CO)3(dppm-P)] (1a) with [Ru(CO)3Cl(μ-Cl)]2, the chloride-bridged tetranuclear hydrido complex [(OC)3{(MeO)3Si}Fe(H)(μ-dppm)Ru(CO)2Cl(μ-Cl)]2 (4) was formed in which the Fe and Ru centers are only linked via bridging dppm ligands.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Pierre Braunstein (Corresponding author)Email: |
33.
Heterodinuclear silyl complexes of the type [(OC)3(R3Si)[Fe(mu-PPh2)Pt](CO)(PPh3)], which contain a [Fe(mu-P)Pt] triangular core, were previously reported to undergo an unprecedented dyotropic-type rearrangement involving migration of the silyl group from iron to platinum with concomitant 1,2 migration of CO from Pt to Fe. In the resulting complexes of formula [(OC)4[Fe(mu-PPh2)Pt](SiR3)(PPh3)], the Si atom occupies a cis position at the planar Pt center with respect to the phosphido bridge. DFT calculations were employed to elucidate the mechanism of this intramolecular silyl migration reaction. When the Fe-Pt precursor complex is [(OC)3(R3Si)[Fe(mu-PPh2)Pt](PPh3)2], the reaction sequence involves (i) the substitution of PPh3 by CO at Pt, (ii) the concerted migration of CO and SiR3, and (iii) the cis-trans isomerization at Pt. The calculations support the exergonic character of the overall process. An explanation for the experimental observation of only one product isomer being formed is possible via frontier molecular orbital analysis. Consistent with the experimental findings, the transition states of the migration (a species with a triply bridged intermetallic bond) and isomerization steps were found to be energetically within reach at room temperature. Additional support for the suggested mechanism also comes from the fact that relative silyl migration activities could be rationalized by the means of quantum chemistry. 相似文献
34.
CNN Pincer Ruthenium Catalysts for Hydrogenation and Transfer Hydrogenation of Ketones: Experimental and Computational Studies 下载免费PDF全文
Prof. Walter Baratta Dr. Salvatore Baldino Prof. Maria José Calhorda Dr. Paulo J. Costa Prof. Gennaro Esposito Dr. Eberhardt Herdtweck Dr. Santo Magnolia Dr. Carlo Mealli Dr. Abdelatif Messaoudi Dr. Sax A. Mason Prof. Luis F. Veiros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13603-13617
Reaction of [RuCl(CNN)(dppb)] ( 1‐Cl ) (HCNN=2‐aminomethyl‐6‐(4‐methylphenyl)pyridine; dppb=Ph2P(CH2)4PPh2) with NaOCH2CF3 leads to the amine‐alkoxide [Ru(CNN)(OCH2CF3)(dppb)] ( 1‐OCH2CF3 ), whose neutron diffraction study reveals a short RuO ??? HN bond length. Treatment of 1‐Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)] ? (EtOH)n ( 1‐OEt?n EtOH ), which equilibrates with the hydride [RuH(CNN)(dppb)] ( 1‐H ) and acetaldehyde. Compound 1‐OEt?n EtOH reacts reversibly with H2 leading to 1‐H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1‐OEt?n EtOH and 1‐H reveal hydrogen bond interactions and exchange processes. The chloride 1‐Cl catalyzes the hydrogenation (5 atm of H2) of ketones to alcohols (turnover frequency (TOF) up to 6.5×104 h?1, 40 °C). DFT calculations were performed on the reaction of [RuH(CNN′)(dmpb)] ( 2‐H ) (HCNN′=2‐aminomethyl‐6‐(phenyl)pyridine; dmpb=Me2P(CH2)4PMe2) with acetone and with one molecule of 2‐propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru‐hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH2 is mediated by the alcohol and leads to the key “amide” intermediate. Regeneration of the hydride complex may occur by reaction with 2‐propanol or with H2; both pathways have low barriers and are alcohol assisted. 相似文献
35.
Prof. Dr. K. C. Nicolaou Dr. Philipp Heretsch Dr. Abdelatif ElMarrouni Christopher R. H. Hale Dr. Kiran K. Pulukuri Dr. Avinash K. Kudva Dr. Vivek Narayan Prof. Dr. K. Sandeep Prabhu 《Angewandte Chemie (International ed. in English)》2014,53(39):10443-10447
A catalytic asymmetric total synthesis of the potent and selective antileukemic Δ12‐prostaglandin J3 (Δ12‐PGJ3) is described. The convergent synthesis proceeded through intermediates 2 and 3 , formed enantioselectively from readily available starting materials and coupled through an aldol reaction followed by dehydration to afford stereoselectively the cyclopentenone alkylidene structural motif of the molecule. 相似文献
36.
The reaction of 4-morpholinopyridine with TMSCH2Li induced an unprecedented anionic ring contraction of the morpholine ring in an exo-trig mode while lithiating the pyridine ring regioselectively at C-3. The one-pot process offers a straightforward route to functional oxazolidinyl pyridines. 相似文献
37.
Margraf G Pattacini R Messaoudi A Braunstein P 《Chemical communications (Cambridge, England)》2006,(29):3098-3100
Two tautomers of the new phosphinoaminothiazoline Ph2PNHC=NCH2CH2S, obtained from the reaction of 2-amino-2-thiazoline (ATHZ) with Ph(2)PCl, have been structurally characterized and the intermediate formation of the diphosphine Ph2PN=CN(PPh2)CH2CH2S has been demonstrated experimentally and by DFT calculations; reacts with [AuCl(THT)] to give [(AuCl)2] whereas the bidentate metalloligand cis-[Pt(1(-H))2] reacts with AgOTf to form the Ag-Pt coordination polymer [Ag(infinity)[Pt(1(-H))2](infinity)](OTf)(infinity). 相似文献
38.
A TMSCH2Li-based reagent promoted the first C-3 lithiation of DMAP opening a direct access to functional diversity in acylation catalysts. 相似文献
39.
The first regioselective C-4 lithiation of (S)-nicotine has been realized using TMSCH2Li as basic reagent in toluene. The reaction proceeded under mild conditions with a small excess of electrophile. The 4-chloro derivative was subsequently metallated at C-5 with the same basic reagent in THF at -78 degrees C. This methodology opens a straightforward access to functional diversity in (S)-nicotine chemistry. 相似文献