Hypercoordinated Oligosilanes Based on Aminotrisphenols

Abstract

The hypercoordinated silicon chlorides ClSi[(o-OC6H4)3N] (3) and ClSi[(OC6H2Me2CH2)3N] (5) were used for the synthesis of catenated derivatives (Me3Si)3SiSi[(o-OC6H4)3N] (9), (Me3Si)3SiSiMe2SiMe2Si(SiMe3)2Si[(o-OC6H4)3N] (11), and (Me3Si)3SiSi[(OC6H2Me2CH2)3N] (13) in reactions with (Me3Si)3SiK·THF (7) or (Me3Si)3SiK·[18-crown-6] (8). It was found that the nature of the (Me3Si)3SiK solvate determines the product of interaction, resulting in the formation of (Me3Si)3Si(CH2)4OSi[(OC6H2Me2CH2)3N] (12) or 13. Compounds obtained were characterized using multinuclear NMR and UV–vis spectroscopy and mass spectrometry. The molecular structures of 3, 9, and 11–13 were investigated by single-crystal X-ray analysis, featuring hypercoordinated Si atoms in a trigonal-bipyramidal coordination environment with O atoms in the equatorial plane. The structure of the side product [N(CH2C6H2Me2O)3Si]2O (6) was also studied, indicating highly tetrahedrally distorted trigonal-bipyramidal environment at the Si atoms, which was confirmed by crystal density functional theory calculations indicating the very weak Si ← N interaction. The Si···N interatomic distances span a broad range (2.23–2.78 Å). The dependence of structural and NMR parameters for hypercoordinated catenated compounds from the type of the ligand was established.

Electrooxidation of Hypercoordinated Derivatives of Silicon and Reactivity of Their Electrogenerated Cation Radicals: 1-Substituted Silatranes

“…From the experimental and theoretical findings of this work, the stability of the CRs of silatranes against deprotonation can be expected to be enhanced upon: Weakening of the N→Si interaction in the starting silatranes (i.e., reducing the electronegativity of the substituent R and the solvent polarity); and Replacing the protons at C α and C β atoms with alkyl groups or with F atoms, or else merging the C α –C β bond into side cyclic structures, primarily aromatic (phenylene substitution). The latter means passing to tribenzsilatranes (see [ 43 , 73 , 74 ]), in which the deprotonation is expected to be less important due to the unfavorable orbital orientation of the p z (N) and π systems of the side aromatic rings, reducing positive charge delocalization in the latter in the CRs. Further study in these directions is underway and will be published elsewhere.…”

Oligosilanylated Silocanes

“…Extending our previous work on oligosilanylated silatranes [ 3 , 4 , 5 , 6 , 7 ], we have chosen to study the chemistry of a related system with a less constrained geometry. For this reason we decided to turn to the family of silocanes, which can be regarded as silatranes with one of the bridging arms between nitrogen and silicon missing.…”

“…Nowadays, a number of compound classes featuring hypercoordination are well-investigated. Especially, the cage-type atrane molecules of heavier group 14 elements have received much attention [ 1 , 2 ] and recently we have contributed to these investigations by some studies of oligosilanyl-substituted silatranes [ 3 , 4 , 5 , 6 , 7 ].…”

Crystal Structure of New 1-Phenyl-Substituted Tribenzsilatranes

“…Upon substitution of lateral ethylene chains in 1 for phenylene fragments (i.e., going to tribenzsilatranes X-Si(OC 6 H 4 ) 3 N (2)), a noticeable elongation of the Si• • • N contact is observed (according to XRD data [2,[15][16][17]). This elongation can be related to the increased rigidity of the atrane cage (in other words, to the profile of the potential function of deformation of the N→Si bond).…”

“…As an alternative explanation, the redistribution of electronic effects in the side chains (substitution of alkane carbon atoms for more electronegative aromatic ones) can also be advanced [17]. However, neither of these explanations have yet received convincing support.…”