6166-12-7Relevant academic research and scientific papers
The allyl leaving group approach to tricoordinate silyl, germyl, and stannyl cations
Lambert, Joseph B.,Zhao, Yan,Wu, Hongwei,Tse, Winston C.,Kuhlmann, Barbara
, p. 5001 - 5008 (2007/10/03)
A group 14 atom bonded to three mesityl groups (2,4,6-trimethylphenyl) and to one allyl group serves as a novel precursor to tricoordinate group 14 cations, the analogues of the carbocation. The double bond of the allyl group provides an accessible reaction site that is located beyond the ortho methyl groups. Reaction of various electrophiles with the double bond releases the allyl group and leads to formation of the group 14 cations. The mesityl groups then are of sufficient steric bulk to protect the tricoordinate metal center from attack by nucleophiles. This approach is used herein with silicon, germanium, and tin as the central atom. The 29Si chemical shift (δ 225) indicates full cationic character for the silicon system. The 119Sn chemical shift (δ 806) indicates less than full cationic character for the tin system. The positive charge for the germanium system has been assessed by examination of the aromatic 13C chemical shifts. These results provide the highest current cationic character for silylium and stannylium ions.
Trimesitylzinn-hydroxid und -fluorid als Modellsubstanzen zur Bestimmung der "Normal"-Kovalenzabstaende Zinn-Sauerstoff und Zinn-Fluor
Reuter, Hans,Puff, Heinrich
, p. 223 - 234 (2007/10/02)
Trimesityltin hydroxide and fluoride have been prepared and have been studied by single crystal X-ray diffraction and IR spectroscopy.In both compounds the tin atoms are tetrahedrally coordinated, and the oxygen and fluorine atoms twofold and singly coordinated, respectively.The observed bond lengths are 199.9 pm for Sn-O and 195.7/196.5 pm (av. 196.1 pm) for Sn-F.
Substituent effects upon the kinetics of hydrogen transfer from triorganotin hydrides to the 5-hexen-1-yl radical
Pike, Philip W.,Gilliatt, Vernon,Ridenour, Michael,Hershberger, James W.
, p. 2220 - 2223 (2008/10/08)
Steric and electronic substituent effects were probed for the hydrogen atom transfer reaction of a series of triorganotin hydrides with the 5-hexen-1-yl radical. Rate data were obtained for tributyltin hydride (1), triisopropyltin hydride (2), tri-tert-butyltin hydride (3), trineopentyltin hydride (4), trimesityltin hydride (5), and dibutylethoxytin hydride (6). Arrhenius parameters are reported for the reactions of 1-4 and 6; the reaction of 5 was studied only at 50°C. For compounds 1-4, the activation energy, Ea, decreased monotonically with increasing alkyl size from 3.9 ± 0.1 to 3.1 ± 0.1 kcal mol-1. The preexponential factor, expressed as log A, decreased monotonically from 9.4 ± 0.1 to 8.8 ± 0.1. The effect of the ethoxy substituent, 6, relative to an n-butyl substituent, 1, upon the activation energy was negligible (4.2 ± 0.2 versus 3.9 ± 0.1 kcal mol-1, respectively), but the preexponential factor, log A, increased from 9.4 ± 0.1 to 10.0 ± 0.1. The activation data for 1-4 are interpreted in terms of the steric requirements of the alkyl groups appended to tin. The lack of a significant substituent effect upon Ea by the ethoxy group is reflective of a nonpolarized transition state for the hydrogen atom transfer reaction.
