Substituent effects on the 31P NMR chemical shifts of arylphosphorothionates
摘要:
Six tris(aryloxy)phosphorothionates substituted in the para position of the aromatic rings were synthesized and studied by P-31 NMR, X-ray diffraction techniques and ab initio calculations at a RHF/6-31G** level of theory, in order to find the main structural factors associated with the delta P-31 in these compounds. As the electron-withdrawing (EW) ability of the substituents was increased, an 'abnormal' shielding effect on delta P-31 of the arylphosphorothionates was observed. The analyses of the geometrical properties obtained through both experimental and theoretical methods showed that a propeller-type conformation is preferred for the arylphosphorothionates, except in the case of the tris(O-4-methylphenyl)phosphorothionate, since one of the aromatic rings is not rotated in the same direction as the other two in the solid state. The main features associated with the delta P-31 NMR of compounds 1-6 were a decrease of the averaged O-P-O angle and mainly the shortening of the P=S bond length, which is consistent with an increase of the thiophosphoryl bond order as delta P-31 values go upfield. On the other hand, comparison of the experimental and calculated bond lengths and bond angles involving a bonded atoms to phosphorus of the six compounds suggested that stereoelectronic interactions of the type n(pi)O-sigma*(P=S), n(pi)O-sigma*(P-OAr) and n(pi)S-sigma*(P-OAr) could be present in the arylphosphorothionates 1-6. (c) 2005 Elsevier Ltd. All rights reserved.
作者:Makeba B. Murphy-Jolly、Lesley C. Lewis、Andrew J. M. Caffyn
DOI:10.1039/b507752d
日期:——
Tris(perfluoroalkyl)phosphines, of interest as tunable alternatives to the carbon monoxide ligand, can be synthesised by the nucleophile mediated reaction of perfluoroalkyltrimethylsilanes with triphenylphosphite; the method can be extended to diphosphines.
Neue Methoden zur Herstellung von Carbonsäure-arylestern. Über aktivierte Ester VIII
作者:B. Iselin、W. Rittel、P. Sieber、R. Schwyzer
DOI:10.1002/hlca.19570400216
日期:——
Two new methods for preparing carboxylic acid aryl esters are presented. They consist in reacting the carboxylic acid with (a) aryl sulfites or (b) aryl phosphites in the presence of pyridine. A possible mechanism of the sulfite method is discussed.
On the mechanism of the nickel-catalysed regioselective cyclodimerization of isoprene
作者:P.W.N.M. van Leeuwen、C.F. Roobeek
DOI:10.1016/s0040-4020(01)97949-9
日期:——
similar steric properties the changes in product distribution as a function of the electronic ligand parameter are explained in terms of a gradual change in HOMO-LUMO interactions between Ni and the olefins, with strong π-acidic ligands promoting the head-to-headcoupling of the isoprene molecules. The second step, involving reductive elimination of a cyclodimer from the metal, shows an increasing selectivity
The effect of electron-withdrawing (EW) and electron-releasing (ER) substituents on the 31P NMR chemicalshifts and the structural parameters of a series of tris-(p-X-aryl)selenophosphates is reported in this article. Similarly to O-aryl phosphates and O-aryl thiophosphates, EW groups attached to aromatic rings induce a shielding effect on the 31P NMR signal. After a detailed experimental and theoretical
本文报道了吸电子 (EW) 和放电子 (ER) 取代基对 31 P NMR 化学位移和一系列三-(pX-芳基)硒代磷酸酯结构参数的影响。与 O-芳基磷酸酯和 O-芳基硫代磷酸酯类似,连接到芳环上的 EW 基团对 31P NMR 信号产生屏蔽效应。经过详细的实验和理论分析,我们证实硒原子是负责通过反向键合效应向磷转移电荷密度的主要部分。获得的完整系列的 1JP-Se 值与这一观察结果一致。补充材料可用于本文。转至出版商在线版的磷、硫和硅及相关元素,查看免费的补充文件。
Rhodium recovery from hydroformylation still heel with triaryl phosphate ligand
申请人:E.I. DU PONT DE NEMOURS AND COMPANY
公开号:EP0000665A1
公开(公告)日:1979-02-07
A process for recovering rhodium present in a still heel from the hydroformylation of an unsaturated hydrocarbon wherein rhodium and a triaryl phosphite ligand were used by a process comprising
a) pretreating the still heel with a compatible organic solvent, at least 5 ml of water per 100 g of still heel, oxygen gas or a precursor thereof and sufficient base to produce a pH of 2 to 7 in the reaction mixture after rhodium precipitation;
b) heating to a temperature of from 0° to 80°C to oxidize the triaryl phosphite ligand to the corresponding phosphate compound;
c) heating the mixture from b) for from about 15 minutes to about 120 minutes at about 115°C to about 175°C to precipitate the rhodium and optionally purifying the rhodium from c) by
d) separating the rhodium precipitate;
e) washing the rhodium precipitate with a solvent-acid solution at a pH of to4;
f) treating the rhodium precipitate with an alkaline reducing solution to reduce the trivaient rhodium impurity to zero valent rhodium;
g) quenching the rhodium with glacial acetic acid;
h) separating the rhodium;
i) washing the rhodium with an acid solution at a pH of 3 to 4;
j) drying the rhodium in an inert atmosphere at from 250° to 400°C; and
k) oxidizing the rhodium at a temperature of from 300° to 900°C to convert the rhodium to Rh2O3.