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61.
The [Et4N][M(CO)5SCOPh] complexes (1a, M = Mo; 2a, M = W) have been prepared at ambient temperatures by reacting the photogenerated M(CO)5 THF intermediate with [Et4N][SCOPh] in THF. Kinetic studies of the reactions of the anions [M(CO)5SCOPh]– with the tri(iso-propyl)phosphite (L) ligand under pseudo-first-order conditions indicate that these reactions are first-order in substrate and are independent of the P(OPr-i)3 concentration. It is thus envisaged that these CO substitutions proceed via a mechanism which involves initial cis-M—CO bond-breaking, followed by fast attack of the incoming nucleophile on the resulting intermediate to give [cis-M(CO)4{P(O-Pri)3}SCOPh]–. This facile displacement of cis-CO indicates the labilizing nature of the thiobenzoate ligand, most probably by virtue of distal oxygen atom participation. Activation parameters for the reactions are: [M(CO)5SCOPh]– + L cis-[M(CO)4(L)SCOPh]– + CO M = Mo, H
= 24.6(2) kcal mol–1, S
= 8.2(6) eu; M = W, H
= 28.4(2) kcal mol–1, S
= 11.3(5) eu. Kinetic data and the mechanism of these ligand-substitutions are discussed. 相似文献
62.
Summary
We give an intrinsic (set theoretical) method to obtain all realcompletions of a Tychonoff space X. It is based on the concept of a spectral structure. Every realcompletion of the space can be obtained as a space of terminal clusters relative to an appropriate spectral structure on X. Various applications of this concept are then given. For example we may characterize those spectral structures which yield the realcompletions between X and X, or which yield spaces that are realcomplete (that is, realcompact), or compact or pseudocompact or Lindelöf. We also determine the class K of compactifications K of X for which X will be real closed in K for every K K.Here we continue the use of the word realcompletion (see [2]) in place of real-compactification. As many investigations have shown and as the present article reinforces, the former is more appropriate than the latter. 相似文献
63.
Munir M. Ahmad Martin R. Bryce Joan Halfpenny Larry Weiler 《Tetrahedron letters》1984,25(38):4275-4278
Bis(triphenylphosphoranylidene)ammonium iodide (PPN+I?) forms a 2:3 complex with TCNQ [(PPN)2(TCNQ)3(CH3CN)2] that provides an example of a TCNQ complex containing acetonitrile in the crystal lattice; the material is a semi-conductor with trimerised TCNQ stacks. 相似文献
64.
Diastereoisomers (1S,2R,3S)-, (1R,2R,3S)-, (1R,2S,3S)- and (1S,2S,3S)-2-methyl-1-phenyl-1,3-butanediols were prepared by simple and convenient strategies using two different chemo-enzymatic approaches for the reduction of racemic 2-methyl-1-phenyl-1,3-butanedione, both involving in situ racemization. The first method comprised a one-pot microbial reduction coupled with a chemical reduction, while in the second method, stepwise chemo-enzymatic reductions were performed. 相似文献
65.
M.?Prasad S.?P.?MoulikEmail author A. Al.?Wardian S.?Moore A.?van?Bommel R.?PalepuEmail author 《Colloid and polymer science》2005,283(8):887-897
The clouding points (CP) of the nonionic surfactants p-tert-octyl phenyl polyoxyethylene ether (Triton X 100), Brij-56 and Brij-97, and the water soluble polymer polyvinylmethylether (PVME) have been measured in the presence of the ionic surfactants alkyl (C10, C12, C14 and C16) triphenyl phosphonium bromides (ATPBs). The threshold additive concentrations required for efficient CP enhancement of the systems that were studied have been determined. Considering CP as the threshold state of phase separation, the energetics of the process at different additive concentrations has been evaluated. The spontaneity of free energy of the clouding process (G
c
0
) at the transition concentrations followed the order PVME > TX 100 Bj 56 > Bj 97. The clouding process has been found to be energetically endothermic with fairly large enthalpy and entropy changes that nicely compensate each other. The compensation temperature has been evaluated and compared with different types of the clouding agents.This revised version was published online in January 2005 with corrections to the names of the authors. 相似文献
66.
Summary Potassium dihydro-bis-(1-indazolyl)borate, synthesized from potassium borohydride and indazole, has been used as a reagent to yield complexes with copper(II), nickel(II), cobalt(II), manganese(II) and iron(III) ions. From i.r. spectral studies the ligand is uninegative and bidentate and coordination occurs through the nitrogen atom at position 2 of the indazole ring system in all cases. With the sole exception of the copper(II) complex, the nitrogen atom at position 1 is also involved in forming a bridge with an adjacent metal ion. On the basis of electronic spectral studies and magnetic susceptibility measurements a distorted square planar structure involving chlorine bridges has been proposed for the copper complex. An octahedral geometry with ligand bridges for all complexes is tentatively proposed and it appears that all are polymers. 相似文献
67.
Two series of 2-(N-aryl-2-oxo-2-arylethanehydrazonoyl)-6-methyl-4(3H)-pyrimidinones 11 (12) were prepared by coupling of diazotized anilines with 2-(aroylmethylene)-1,2-dihydro-6-methyl-4(3H)-pyrimidinones 2 (3). The spectral data of such compounds together with their 3-methyl analogs 13 (14) indicated that they exist predominantly in the hydrazone tautomeric form. 相似文献
68.
Abdullah A. Al‐Karim Al‐Shara'ey 《中国化学会会志》2004,51(3):547-552
6‐Aryl‐5‐cyano‐4‐pyrimidinone‐2‐thion derivatives 1a‐c reacted with methyl iodide (1:2) to give the corresponding 2‐S,N‐dimethyl pyrimidine‐4‐one derivatives 2a‐c . Compounds 2a‐c were in turn, reacted with hydrazine hydrate to give the sulfur free reaction products 3a‐c . These reaction products were taken as the starting materials for the synthesis of several new heterocyclic derivatives. Reaction of 3a‐c with acetic anhydride and formic acid gave pyrimido triazines 4a‐c and 7a‐c , respectively. Their reactions with active methylene containing reagents gave the corresponding 2‐(1‐pyrazonyl)‐N‐methyl pyrimidine derivatives 9a‐c and 10a‐c , respectively. Their reactions with aromatic aldehydes afforded the corresponding 2‐hydrazono pyrimidine derivatives 11a‐c . The structure of these reactions products were established based on both elemental analysis and spectral data studies. 相似文献
69.
70.
A series of chelating reagents, 1-phenyl-3-methyl-4-(2-fluorobenzoyl)-5-pyrazolone, 1-phenyl-3-methyl-4-(3-fluorobenzoyl)-5-pyrazolone and 1-phenyl-3-methyl-4-(4-fluorobenzoyl)-5-pyrazolone, has been synthesized. The extraction of Ln(III), (Ln = La, Eu and Lu) into chloroform with these reagents at 30 +/- 1 degrees has been studied. The composition of the complexes extracted has been determined by the slope method, and the extraction constants K(ex), were measured. The presence of the fluorine atom in the reagents does not make the K(ex), values much different from those obtained with the parent pyrazolone. 相似文献