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241.
Constantin Mamat 《Journal of organometallic chemistry》2004,689(10):1739-1745
1-(8-Methoxy-1-naphthyl)-1,2,2-tris(trimethylsilyl)silene (10) and the 1-[2,6-bis(alkoxymethyl)phenyl]-1,2,2-tris(trimethylsilyl)silenes (12a-d) were generated by the reaction of (dichloromethyl)tris(trimethylsilyl)silane (1) with two molar equivalents of 8-methoxy-1-naphthyllithium or 2,6-bis(alkoxymethyl)phenyllithium (8a-d), respectively, but proved to be unstable. 10 was trapped with excess of the applied naphthyllithium reagent to give 1,1-bis(8-methoxy-1-naphthyl)-1-[bis(trimethylsilyl)methyl]-2,2,2-trimethyldisilane (11); and 12a-d underwent spontaneous conversions and formed two types of substituted 2-oxa-1-silaindane derivatives (13a,b and 14b-d). Whereas silenes with an intramolecular amine coordination are thermally stable compounds which can be isolated, the intramolecular coordination of an ether group to the electrophilic silene silicon atom does not provide a comparable stabilization to the SiC system and the respective derivatives generated were converted into resultant products. 相似文献
242.
Tetramethyl Ammonium Amalgam, [N(CH3)4]Hg8 Crystals of tetramethyl ammonium amalgam with the composition [N(CH3)4]Hg8 were prepared by electrolysis. According to temperature‐dependent X‐ray diffraction experiments the compound transforms into an amorphous product above 6 °C; the decomposition is a multi‐stage process as shown by DTA experiments. X‐ray examinations of crystalline aggregates indicate a structure of low symmetry with remarkable similarities to that of α‐Hg. 相似文献
243.
R. Bugoi V. Cojocaru B. Constantinescu F. Constantin D. Grambole F. Herrmann 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(2):375-383
Several fragments of ancient gold objects coming from an Eneolithic hoard and from Pietroasa Cloca cu Puii de Aur (The Golden Brood Hen with Its Chickens) hoard, unearthed on Romanian territory, and two Romanian native gold nuggets samples were analyzed using micro-PIXE technique. The purpose of the study was to clarify the metal provenance. Trace and minor elements (Cu, Te, Sn, Pb, Ti, Cr, V, Mn, Ta) and platinum group elements (PGE) concentrations were estimated. The presence of inclusions (micrometer size areas of composition different from the surroundings) was investigated. We found Si and Ca inclusions on two Eneolithic samples, and Ta inclusions on two samples from Pietroasa hoard. The measurements suggested an alluvial origin of gold for the Eneolithic samples and give indications for the possible gold ore sources of Pietroasa hoard. 相似文献
244.
Jonathan M. Curtis Peter J. Derrick Andr Schnell Emilie Constantin Richard T. Gallagher John R. Chapman 《Journal of mass spectrometry : JMS》1992,27(11):1176-1180
Electrospray ionization on Ln(tfc)3 complexes (Ln = Eu, Yb; tfc = D -3-trifluoroacetylcamphorate) was performed with samples dissolved in methanol–water containing acetic acid. The spectra were obtained with a four-sector mass spectrometer. The mass spectra exhibit ions containing tfc ligand in addition to ions with acetato ligand. Electro-spray and tandem mass spectra are presented. 相似文献
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247.
Constantin Nacaronstacaronsescu 《代数通讯》2013,41(19):2441-2453
248.
249.
Stereochemical Behavior of Pairs of P-stereogenic Phosphanyl Groups at the Dimethylxanthene Backbone
Dr. Karel Škoch Dr. Constantin G. Daniliuc Marcel Müller Prof. Dr. Stefan Grimme Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202200248
The P-stereogenic bis(phosphanes) 7 and 9 , featuring pairs of P(Mes)-ethynyl or vinyl substituents at the dimethyl xanthene backbone show rather low barriers of stereochemical inversion at phosphorus. π-Conjugative effects are probably causing these low inversion barriers. Compound 7 reacted with B(C6F5)3 to form the nine-membered heterocyclic product 10 , featuring a [P]−C≡C−B(C6F5)3 substituent. Compound 7 was converted to the bis[P(Mes)vinyl] xanthene derivative 9 , which gave the zwitterionic P(H)(Mes)−CH=CH−B(C6F5)3 containing product 16 upon treatment with B(C6F5)3. Thermally induced epimerization barriers at phosphorus of ca. 20 to 27 kcal mol−1 were calculated by DFT for the alkenyl- and alkynyl-P derived systems 6 to 9 , 15 and 16 and experimentally determined for the examples 7 and 16 . 相似文献