Si, Ge and Sn compounds with geminal donor functions
 

Silicon compounds with donor atoms in geminal position have a lot of unusual properties as compared to those of the carbon analogues. The deviating properties include magnetic susceptibility, dipole moments, basicity, various spectroscopic parameters, reactivity and molecular structure. Such effects have often been described as the α-effect in silicon chemistry, but also germanium and tin chemistry.
These investigations are relevant for a fundamental understanding of the chemistry of geminal systems and heteroatom effects in silicon chemistry. Compounds with SiON units (silylhydroxylamines) are also important as silicone rubber cold curing catalysts and discussed as intermediates in catalytic reactions of SiH functions.
Our research in this field is the synthesis of simple model compounds containing an acceptor atom (Si, Ge, Sn) and a donor atom (N, O, P, S) linked by a spacer group.

Acceptor
Spacer
Donor
Al, Ga, In
Si, Ge, Sn
C, N, O ...
O, S ...
N, P ...

Both types of aggregation (monomers and dimers) are found as illustrated by the following examples.

Crystal structure of F3SiONMe2

Crystal structure of F3SiCH2NMe2

We investigate systematically the factors determining the aggregation type and interaction strength such as substituent effects at donor, acceptor and spacer atom and the conformation of the molecules.

Crystal structure of (F3C)F2SiONMe2

Crystal structure of (F3Si)(Me3Si)NNMe2

Further extension of this research aims at the investigation of a broader range of acceptor A, spacer S and donor groups D. The following table shows some immediately obvious possibilities for combinations.

A
Z
D
F3Si-, FH2Si-, F3CF2Si-, R3Si-
F3Ge-, (F3C)3Ge-, R3Ge-
F2P-, (F3C)2P-, R2P-
F2As-, (F3C)2As-, R2As-
F4P-, R4P-
F4As -, R4As-
F4Sb-, R4Sb-
-CH2-,
-CR2-
-NR-
-PR-
-O-
-S-
-Se-
-NR2
-PR2
-AsR2
-OR
-SR
please choose...
 
Si, Ge and Sn Compounds
with Geminal Donor Functions

 
Michael Hagemann
Organometallic Compounds
with M-C-X Units (X = Donor)

 
Angelika Gabor
 
Daniel Bojer
Stabilization of Lewis-Acidic Main Group and Transition Metal Fragments Utilizing N-O-Ligand Systems
 
Patrick Bösing
 
Matthias Ullrich
Molecular Precursors for Materials
 
Ingo Gronde
 
Surajit Jana
Maingroup-donor-acceptor molecules and OHCD-Crystallization of liquids
 
 
Constantin Sicking
Theory and Gasphase Electron Diffraction
 
Dr. Raphael J. F. Berger
Calixarenes
 
Ulf Strasser
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