Intramolecular interactions in compounds bearing SiOCCN or COCCN fragments

Abstract

Two main types of intramolecualr interaction are possible in molecules of 2,2,6-trimethyl-1,3-dioxa-6-aza-2-silacyclooctane (VII), (2-trimethylsiloxyalkyl)ami- nes (III-VI) and tris(2-R-ethyl)amines I-II, each of which bears a OCCN fragment. These are: (i) through-bond coupling of nitrogen and oxygen lone pairs and (ii) interaction of the nitrogen or oxygen lone pair with σ★ MOs of the OCCN skeleton arranged in the same plane (anomeric effect). A CNDO/S calculation of the photoelectron spectrum of dimethyl(2- methoxyethyl)amine, MeOCH 2CH 2NMe 2 with differing spatial orientations of methoxy and dimethylamine moieties has shown that depending on the orientation of nitrogen or oxygen lone pairs these two types of interaction narrow the gap between nitrogen and oxygen orbitals (ca. 0.5–0.6 eV) or drive them apart ca. 1.8 eV. The former is indicative of the presence of only one intense band in the photoelectron spectra of I-II and two bands (ca. 10 and 11 eV) in the spectra of methylsilatranes (VIII, IX) and higher equilibrium constants in the hydrogen bonding of phenol with the above compounds.