| Abstract
| - RHF/6-31G* and B3LYP/6-31G* computations were performed on the silene [Me2NNC(Me)O]2SiCH2 (6) and analyzed through the use of properties of atoms in molecules. Threestationary states of 6 belong to its non-chelate (6a) and two intramolecularly N-donor-stabilized forms, five-membered mono-chelate (6b) and previously unknown (for the silenes)bis-chelate (6c), with three-, four-, and five-coordinate doubly bonded silicon, respectively.On going from 6a to 6b and 6c, initially planar silicon attains distorted tetrahedral andsquare pyramidal structures, whereas the SiC double bond becomes more polar and changesits distance from 1.674 Å to 1.693 and 1.704 Å and from 1.691 Å to 1.701 and 1.713 Å at theRHF and B3LYP levels, respectively. The RHF and B3LYP N−Si distances in 6b (1.988and 2.031 Å) are shorter than in 6c (2.187 and 2.140 Å). The N→Si bond in chelates 6b,c isdescribed as highly polar, but of sufficiently covalent character. The four-center six-electron(4c-6e) model is proposed for the silicon bonding in the N2SiC moiety of 6c. High energeticadvantages of the chelate 6b and 6c forms over 6a (26.8 and 31.4 kcal/mol at the B3LYP/6-31G* level including the ZPE correction and 32.4 and 36.3 kcal/mol at the RHF/6-31G*level, respectively) suggest that intramolecular N-donor stabilization may be sufficient toobserve silene 6 under relatively mild conditions.
- The RHF/6-31G* and B3LYP/6-31G* computations on 1,1-bis[N-(dimethylamino)acetimidato]silene demonstrate energetic advantages of its bis-chelate form, having SP geometry about doubly bonded silicon, over related mono-chelate and non-chelate forms.
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