Vibrational spectra and rotational isomerism of t-butyl formate

Polysulfide anions II: structure and vibrational spectra of the S4(2-) and S5(2-) anions. Influence of the cations on bond length, valence, and torsion angle

The influence of the cations on bond length, valence, and torsion angle of S4(2-) and S5(2-) anions was examined in a series of solid alkali tetra- and pentasulfides by relating their Raman spectra to their known X-ray structures through a force-field analysis. The IR and Raman spectra of BaS4.H2O and the Raman spectra of (NH4)2S4.nNH3, gamma-Na2S4, and delta-Na2S5 are presented. The similarity of spectra of gamma-Na2S4 with those of BaS4.H2O suggests similar structures of the S4(2-) anions in these two compounds with a torsion angle smaller than 90 degrees. The variations of SS bond length, SSS valence angle, and dihedral angle of Sn2- anions are related to the polarization of the lone pair and electronic charge of the anion by the electric field of the cations. A correlation between the torsion angle and the SSS valence angle is shown as that previously reported between the length of the bond around which the torsion takes place and the dihedral angle value. These geometry changes are explained by the hyperconjugation concept and the electron long-pair repulsion.

Nuclear magnetic resonance and infrared study of lithium coordination by phosphonates and phosphine oxides R2P(O)CH2COY and their carbanions. Comparison between ketone, ester, and amide COY groups

Lithiated carbanionic chelates α to P(O) groups are formed from four title compounds. Their infrared and 13C and 31P nuclear magnetic resonance spectra show that chelation induces peculiar structural perturbations that depend upon the nature of Y. The corresponding neutral precursors 1–4 are able to form bidentate coordinates with the Li cation, which can be observed in THF when Y = OMe or NMe2 but in benzene only when Y = Me. They are probably intermediates in the lithiated base deprotonation of neutral compounds 1–4.