Cyclic Imides. Preparation of Silylphthalimides and Characterization by Infrared and Mass Spectrometry

A series of silylphthalimides containing silicon substituents —H, —CH3, —C2H5, —CH2CH=CH2, and —C6H5 have been prepared and characterized. The compounds are N-silylated and found to be monomeric in the liquid and gas phase. The i.r. spectroscopic studies in dilute (10−1 M) chloroform solution showed a decrease (approximately 40 cm−1) in the carbonyl stretching frequency on silylation, but relatively small changes (± 7 cm−1) on changing silicon substituents. The major effect appears to be electron donation by silyl groups. The N15 isotopomers were prepared and C—N and Si—N vibrations identified.Mass spectrometric studies of methyl- and phenylsilylphthalimides, including N15 substitution, are reported. A possible mechanism of formation of methyl- and phenylbiphenylene silicon ions, involving loss of methyl or phenyl, carbon dioxide, and hydrogen cyanide, is suggested.