The Role of Conformational Flexibility in the Hyperyalency of Organosilanes

Abstract

Organosilanes with the potentially coordinating group -N^CI-y^NlV^]") or -N(CH-,CH ? OMe) 2 have been prepared and characterized by proton, carbon, and silicon NMR"spectroscopy. None of the compounds showed evidence of hypervalency, suggesting that the conformationally-flexible bridging framework produces an unfavorable entropy of coordination. Abstracth3C η η N R CHa 409 Brought to you by | provisional account Unauthenticated Download Date | 6/3/15 5:50 PM

Stereochemical Flexibility of Bis(amidomethyl)dichlorogermanes. A Novel Dissociative Mechanism of Ligand Exchange in Neutral Hexacoordinated Bischelate Complexes

“…Probably for these reasons, for example, in crystals of N -(trifluorosilylmethyl)phthalimide the Si←O bond distance of 2.654 Å is longest in comparison with those for other pentacoordinate (C,O)-chelate trifluorosilanes . Dynamic coordination−decoordination processes for such “flip-flop” type complexes reported for silicon and tin 23d, derivatives are usually too fast to be observed by NMR, suggesting that the conformationally flexible bridging framework produces an unfavorable entropy of coordination.…”