Investigation of the gas-phase structure and rotational barrier of trimethylsilyl

MARÍA E. DEFONSI LESTARD ; MARÍA E. TUTTOLOMONDO ; EDUARDO L. VARETTI ; DEREK A. WANN; H. E. ROBERTSON; DAVID W. H. RANKIN; A. BEN ALTABEF

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Año: 2010 vol. 984 p. 376 - 382

0022-2860

The molecular structure of trimethylsilyl trifluoromethanesulfonate, CF3SO2OSi(CH3)3, has been determinedin the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculationsusing 6-31G(d), 6-311++G(d,p) and 6-311G++(3df,3pd) basis sets. Both experimental andtheoretical data indicate that only one gauche conformer is possible by rotating about the O?S bond.The anomeric effect is a fundamental stereoelectronic interaction and presents a profound influence onthe electronic geometry. We have investigated the origin of the anomeric effect by means of NBO andAIM analysis. A natural bond orbital analysis showed that the lpp[O bonded to Si)]?r[C?S] hyperconjugativeinteraction favors the gauche conformation. In addition, comparison of the structural and stereoelectronicproperties of the title molecule with those of silyl trifluoromethanesulfonate and methyltrifluoromethanesulfonate has been carried out.