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Tricyclic neutral pentacoordinate silicon complexes are formed by a novel intramolecular rearrangement of pentacoordinate bis(imino nitrogen)-chelated siliconium halide salts. The rearrangement consists of an interchelate aldol-type condensation of imine moieties, forming a new carbon-carbon bond and a third chelate ring.

Ab initio calculations with full geometry optimization have been used to investigate the O and N atom proton affinities and the molecular structures of silatranes (RSi(OCH2CH2)3N), as well as the related compounds RSi(OCH3)3, RSi(OCH2)3CH, and RSi(OCH2CH2)3CH, where R = F, Cl, CH3, SiH3, utilizing the 6-31G(d) basis set. It is found that larger electron donor substituents R induce large proton affinities. The silatranes have stronger proton affinities than the other compounds because of the transannular Si−N interaction. For silatranes, only a small difference between the O and N atom proton affinities is found. The silatrane Si−R bond distances are apparently determined by the degree of the anomeric effect in the R−Si−O fragment and transannular Si−N interactions. Disciplines Chemistry CommentsReprinted (adapted) with permission from Organometallics 20 (2001) Ab initio calculations with full geometry optimization have been used to investigate the O and N atom proton affinities and the molecular structures of silatranes (RSi(OCH 2 CH 2 ) 3 N), as well as the related compounds RSi(OCH 3 ) 3 , RSi(OCH 2 ) 3 CH, and RSi(OCH 2 CH 2 ) 3 CH, where R ) F, Cl, CH 3 , SiH 3 , utilizing the 6-31G(d) basis set. It is found that larger electron donor substituents R induce large proton affinities. The silatranes have stronger proton affinities than the other compounds because of the transannular Si-N interaction. For silatranes, only a small difference between the O and N atom proton affinities is found. The silatrane Si-R bond distances are apparently determined by the degree of the anomeric effect in the R-Si-O fragment and transannular Si-N interactions.