Silicon Hybridization Energy Probed by Changes in Ligand Donor Strength and Molecular Rearrangements in Hexacoordinate Silicon Dichelates

Daniel Kost 1Boris Gostevskii 1Inna Kalikhman 1Mark Botoshansky 2Menahem Kaftory 2

1. Ben-Gurion University, Department of Chemistry, Beer-Sheva 84105, Israel
2. Technion, Department of Chemistry, Haifa 32000, Israel

Abstract

Neutral hydrazide-based hexacoordinate silicon bis-chelates with no halogen ligands, but with two monodentate alkyl (aryl) or hydrido ligands, are described.

formulaSmall.gif

Dimethylamino complexes (1) form weakly coordinated "bicapped tetrahedral" geometries in the solid state (Figure 1), while imino-coordinated complexes (2) are more strongly bound and form distorted octahedral structures (Figure 2). The difference in donor strengths of these two nitrogen-donor types determines whether the dative bonds (in 2 and 1, respectively) provide sufficient energy to promote silicon from tetrahedral to octahedral configuration.

Hexacoordinate silacyclobutane complexes (3) have been prepared. Upon mild heating or photolyzing they undergo a skeletal rearrangement involving cleavage of the four-membered heterocycle (4). In the absence of imino α-protons (3, R1 = Ph, R2 = H) addition of the four-membered ring residue to the imino double bond takes place, forming a new chelate ring (5).

bg559colorSmall_1_1_1.jpg bg553colorSmallest_1_1.jpg
Figure 1: Crystal structure of 1 Figure 2: Crystal structure of 2

Legal notice
  • Legal notice:

    Copyright (c) Pielaszek Research, all rights reserved.
    The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
    In every case, proper references including Author(s) name(s) and URL of this webpage: http://science24.com/paper/8245 must be provided.

 

Presentation: invited lecture at 18th Conference on Physical Organic Chemistry, Plenary session, by Daniel Kost
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-28 06:56
Revised:   2009-06-07 00:44
Google
 
Web science24.com
© 1998-2021 pielaszek research, all rights reserved Powered by the Conference Engine