Joseph D. Cargioli

29Si NMR of five- and six-coordinate organosilicon complexes

Abstract Silicon-29 NMR is shown to be powerful tool for characterizing five- and six-coordinate organosilicon complexes. Chemical shifts for twenty seven compounds are given, and the general trends with structural changes are discussed.

Silicon-29 NMR. Solvent effects on chemical shifts of silanols and silylamines☆

The 29Si NMR spectra of six silanols and four silylamines were examined in several solvents of varying electron pair donor ability. A linear correlation was found between the silanol silicon-29 chemical shift and solvent donor ability. The silylamines were considerably less sensitive to solvent. The effect is attributed to hydrogen bonding between the hydroxyl proton of the silanol and an electron pair of the solvent.

13C fourier-transform NMR study of trimethyl(phenylethynyl)silane: Silicon-carbon bonding

Abstract A 13 C Fourier transform (FT) NMR study of trimethyl(phenylethynyl)silane gives new evidence for ( p → d ) π bonding or equivalent interaction between bonded carbon and silicon atoms. Pulsed FT operation allows detection of 29 Si 13 C spinspin coupling observed as 2.3 % 29 Si satellites in 13 C spectra. The one-bond 13 C 29 Si coupling constants for seven compounds were found to be roughly proportional to “ s ” character on carbon, ranging from 50.2 ( sp 3 ) to 83.6 Hz ( sp ).

Silicon-29 chemical shifts for organosilicon reference compounds

Abstract Silicon-29 chemical shifts are reported for several organosilicons used as reference compounds in 29 Si NMR studies. Solvent-induced shifts were small but significant for two of these compounds measured in six solvents (0.7 ppm for tetramethylsilane and 0.3 ppm for hexamethyldisiloxane). Requirements for a good 29 Si reference compound are discussed.

29Si and 13C NMR Studies of organofunctional di- and trisilanes

Abstract A series of di- and trisilanes of general structure Ph3SiSiMe2R and (Ph3Si)2SiR′R″ were synthesized, and the 29Si and 13C chemical shifts and one-bond siliconsilicon coupling constants (1JSiSi) were measured. The coupling constants of the disilanes were found to be primarily dependent upon the inductive effect of the alkyl group, R, as measured by the Taft o★ constant. In both series of compounds, increasing alkyl substitution at silicon led to a decrease in 1JSiSi.

Carbon-13 nuclear magnetic resonance study of carbon suboxide

The carbon-13 n.m.r. spectrum of carbon suboxide has been recorded and a remarkably high field resonance observed for the central carbon atom.

Effect of solvent media on the electronic character of substituted aromatic systems

Correlation of phenyl ring 13C n.m.r. chemical shifts with SCF–MO charge densities and Hammett type σ-parameters can be used to determine interaction between ring substituents and solvent.

13 C nuclear magnetic resonance of organophosphorus compounds: triphenyl phosphite and triphenyl phosphate

The 13C n.m.r. spectra of triphenyl phosphite and triphenyl phosphate show significant differences in chemical shifts and C–P coupling constants.