Germatranes and their quasi and hypo analogs with highly electronegative substituent at the Ge atom

2012 ◽  
Vol 61 (5) ◽  
pp. 992-998 ◽  
Author(s):  
M. G. Voronkov ◽  
A. A. Korlyukov ◽  
G. S. Samokhin ◽  
D. V. Vrazhnov ◽  
T. A. Kochina
1981 ◽  
Vol 48 ◽  
pp. 41-44 ◽  
Author(s):  
P.M Treichel ◽  
G.P Essenmacher ◽  
H.F Efner ◽  
K.J Klabunde

1995 ◽  
Vol 50 (11) ◽  
pp. 1739-1747 ◽  
Author(s):  
Brigitte Bräunlein ◽  
Frank H. Köhler ◽  
Werner Strauß ◽  
Harald Zeh

A series of paramagnetic (S = 3/2) chromium half-sandwiches of the type CpCrX2D (D = donor) were synthesized by starting from [CpCrX2]2, Cp2Cr, CpCrCl2(THF), and Cp*Cr(CH3)2[P(CH3)3]. Besides the parent cyclopentadienyl (Cp) the alkylated derivatives CH3C5H4, (CH3)5C5 (Cp*), and C2H5(CH3)4C5 were bound to chromium. The electronegative substituent was X = F, Cl, Br, I, and triflate, while the donors were three ethers, four ketones, dimethylsulfoxide, acetonitrile, methylisocyanide, pyridine, and seven molecules ER3 where E = N, P, As, Sb. The half-sandwiches were partly isolated and partly established in solution. The 13C and 1H NMR spectra showed strongly shifted signals which allowed to quantitatively investigate the equilibrium between CpCrX2D and the anti ferromagnetic species [CpCrX2]2. The NMR signals of CpCrX2D and its substituted derivatives appeared in characteristic ranges thus providing a means of rapid identification. Considerable spin density was found to be induced on the ligands; it is negative in the Cp π system. As for the donors, inter- and intramolecular dynamic behavior as well as selective spin transfer to the γ protons of acetonitrile, methylisocyanide, and ketones was detected.


1970 ◽  
Vol 25 (7) ◽  
pp. 665-674 ◽  
Author(s):  
Basanta G. Chatterjee ◽  
Noel L. Nyss

The activating influence of a nitrophenyl substituent in the intramolecular alkylation of compounds of the type 3 and 5 has been studied. The investigation establishes that the activation afforded by a 4-nitrophenyl substituent is intermediate between that of a carbonyl and ester functions. The role of the N-aryl substituent in the alkylation of N-aryl, N-α haloacetamino esters and ketones has also been studied. A number of hitherto unreported lactams have been synthesized and characterized. Synthesis of the compound 4 c using a weak base is of special interest, since this lactam possesses only a single electronegative substituent at the 4-position.


1977 ◽  
Vol 55 (6) ◽  
pp. 1015-1023 ◽  
Author(s):  
Jean Lessard ◽  
Phan Viet Minh Tan ◽  
Robert Martino ◽  
John K. Saunders

The analysis of the 13C and 1H nuclear magnetic resonance data of 2-substituted methylenecyclohexanes and 3-substituted cyclohexenes demonstrates that a double bond stabilizes the axial conformer for an electronegative substituent. Introduction of a methoxy group on the double bond further increases the relative stability of the axial conformer. These results are interpreted in terms of the 'double bond – no bond' resonance.


1955 ◽  
Vol 33 (8) ◽  
pp. 1337-1351 ◽  
Author(s):  
C. Sandorfy

The simple semiempirical molecular orbital method was applied to saturated hydrocarbons in three different approximations. Electronic charge distribution diagrams were obtained. Characteristic differences between saturated and conjugated compounds concerning bond localization and the effect of an electronegative substituent can be interpreted on the basis of these diagrams. The 1s electrons of the hydrogens are introduced for the first time in semiempirical molecular orbital calculations.


1982 ◽  
Vol 47 (2) ◽  
pp. 603-612 ◽  
Author(s):  
Antonín Lyčka ◽  
Dobroslav Šnobl ◽  
Karel Handlíř ◽  
Jaroslav Holeček ◽  
Milan Nádvorník

29Si and 13C NMR spectra of alkyldiphenylchlorosilanes, alkyldiphenylsilanoles, and bis(alkyldiphenylsilyl)chromates (C6H5)2Si(R)X have been studied. The chemical shifts δ(29Si) are most affected by nature of the electronegative substituent X, i.e. Cl, OH or CrO3OSi(R). (C6H5)2. The δ(29Si) shifts due to effects of the substituents R can be correlated successfully with values of the Taft constants σ. Slopes of the correlation dependences have negative signs for all the groups of the studied compounds (increasing electron-acceptor ability of substituent R causes upfield shifts of δ(29Si), and their values decrease with increasing electronegativity of the substituent X (sensitivity of the δ(29Si) shifts due to sustituent R increases with increasing electronegativity of the substituent X). Methyl groups at γ-position of the chain of substituent R cause a diamagnetic shift of δ(29Si) by 0.6 to 3.3 ppm. The δ(13C) shifts depend little on nature of the substituent X. Chemical shifts δ(13C) of carbon atoms at α-, β-, and γ-positions of the substituent R with respect to silicon show a good linear correlation with the δ(13C) shifts of the corresponding carbon atoms in aliphatic hydrocarbons CH3R. Slopes of the correlation dependences of all the groups of studied compounds are close to 1, the intercepts for α- and β-positions are negative because of induction effect. Positive value of the intercepts for γ-positions reflects the influence of sterical γ-effect.


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