Betty Günther's research while affiliated with Technische Universität Bergakademie Freiberg and other places

The reaction of dichlorodimethylsilane with a polydentate Schiff base ligand derived from pyridoxal and 2-ethanolamine yielded the macrocyclic silicon compound (8 E ,22 E )-4,4,12,18,18,26-hexamethyl-3,5,17,19-tetraoxa-8,13,22,27-tetraaza-4,18-disilatricyclo[22.4.0.0 10,15 ]octacosa-1(24),8,10,12,14,22,25,27-octaene-11,25-diol, C 24 H 36 N 4 O 6 Si 2 . The asymmetric unit contains the half macrocycle with an intramolecular O—H...N hydrogen bond between the imine nitrogen atom and a neighbouring oxygen atom. The crystal structure is dominated by C—H...O and C—H...π interactions, which form a high ordered molecular network.

Disproportionation reactions of chlorosilane compounds in the presence of boron trichloride yield the compound H[B(SiCl3)4]. Spectroscopic analyses of the yellow‐whitish solid with IR‐, Raman‐, and NMR‐spectroscopy (²⁹Si, ¹¹B) show the presence of a highly symmetric anion containing boron, which is fourfold coordinated with silicon. Due to the high symmetry ¹J(¹¹B,²⁹Si) and even ¹J (¹⁰B, ²⁹Si) couplings can be observed in the NMR spectra of the dissolved compound. The crystal structure analysis with a crystal obtained from toluene solution proves the existence of a highly symmetric borate anion, which is stabilized by four trichlorosilyl groups. The molecular structure consists of a para‐protonated toluene cation and the weakly coordinating borate anion [B(SiCl3)4]⁻. Quantum chemical analysis of the tetrakis(trichlorosilyl)borate ion shows a negatively charged boron atom and the presence of polar Si−Cl and Si−B bonds. Highly reactive compounds [E(SiCl3)n]⁻ which are stabilized solely by trichlorosilyl groups have been prepared with E=C, Si, Ge, P, S in recent years. The superacid H[B(SiCl3)4] represents a new member in this elusive compound family.

New cyclic and spirocyclic aminosilanes were synthesised using ethylenediamine, 2-aminobenzylamine, 1,8-diaminonaphthalene, o-phenylenediamine, and trans -cyclohexane-1,2-diamine as starting material. These diamines were converted into aminosilanes using silicon tetrachloride and dimethyldichlorosilane directly and via the N,N’ -bis(trimethylsilylated) amino derivatives. 15 new compounds of the type (diamino)(SiMe 3 ) 2 , (diamino) 2 Si, (diamino)SiMe 2 , and (diamino)SiCl 2 have been prepared. The formation of two cyclotrisilazane derivatives was observed starting from ( N,N’ -2-aminobenzylamino)dichlorosilane by trimerisation. All synthesised compounds have been characterised with NMR-, Raman-, or IR-spectroscopy, mass-spectrometry, and boiling or melting point. Single-crystal X-ray structure analyses of several derivatives have been performed. The degree of substitution with trimethylsilyl groups in the final compounds depends on the ring size of the spirocycles. It was shown with quantum chemical calculations on the M062X/6-31G(d) level that trimethylsilyl groups have a stabilising effect on 5-membered ring systems and a destabilising effect on 6-membered rings in these compounds.

The heteroscorpionate ligand 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethanol, C 24 H 26 N 4 O, features in the solid state an intramolecular O—H...N hydrogen bond. A heteroscorpionate tungsten complex, cis -[2,2-bis(3,5-dimethylpyrazolyl)-1,1-diphenylethanolato]chloridodioxidotungsten(VI) tetrahydrofuran monosolvate, [W(C 24 H 25 N 4 O)ClO 2 ]·C 4 H 8 O, was prepared by the simple mixing of solutions of the ligand and WOCl 4 in tetrahydrofuran. The tungsten complex was isolated after standing for several weeks. The complex exhibits a κ ³N , N ′, O -coordination of the ligand. This simple synthetic procedure allows access to the cis isomer in high yield without additional purification steps. The Hirshfeld surface analysis shows a change of the intermolecular contacts due to the coordination of the WO 2 Cl unit with the ligand molecule.

The reaction of (S)-N-[(2-hydroxynaphthalen-1-yl)methylidene]valine (H2L), 1, with organoelement halides from group 4 and 14 leads to different hypercoordinated complexes depending on the substitution of the starting material. The dianion of 1 therein acts as tridentate ligand in κ³O,N,O’ coordination mode. Complexes with silicon, germanium, tin, and titanium have been prepared in that way and are presented here as proof of concept. With one exception diorganoelement chlorides R2ECl2 yield pentacoordinate complexes LER2. Element tetrachlorides yield hexacoordinate complexes L2E. The prepared compounds were characterized via NMR, IR and UV/Vis spectroscopy, elemental and X-ray structure analysis. Furthermore solid state NMR measurements and chemical shift tensor analysis with the help of quantum chemical methods were used to investigate the electron density distribution around the central atoms of several products. This study demonstrates the ability of 1 to form chiral hypercoordinate complexes with different elements.

Force field parameters for new compound classes are an important prerequisite for the fast and reliable modeling of these compounds with commercial available modeling software. The development of MMX force field parameters for aminoorganosilanes is described in this work. Combined efforts have been undertaken including synthesis, structural characterization of suitable compounds, and quantum chemical calculation with a systematic set of model compounds. 1,2-Dibenzylamino-1,2-dichloro-dimethyldisilane has been synthesized and characterized by X-ray structure analysis. It is possible to calculate bond lengths and angles of this and other aminosilanes with the new force field parameters.

A number of aminosilanes derived from N-methylaniline and chloroorganylsilanes were prepared and characterized. X-ray structure analysis was performed on the crystalline derivatives Ph(Cl)Si(NMePh)2 (4a), HSi(NMePh)3 (2b), MeSi(NMePh)3 (3b), and Ph2Si(NMePh)2 (6b). The compounds were comprehensively characterized by 1H, 13C, 29Si NMR, and IR spectroscopy. Volatile derivatives were further characterized by GC/MS. It was shown using quantum chemical methods that the planarization of the nitrogen atoms in the amino derivatives is caused by phenyl groups and silyl substituents.

Chiral Schiff base ligands with O,N,O0-coordination ability have been prepared with amino acid esters from the chiral pool. Unfortunately the chiral information is lost during the formation of complexes with these chiral ligands with silicon tetrachloride. This was demonstrated with the help of two X-ray structures which show different reaction products depending on chosen reaction conditions. The reaction of N-(salicylidene)-D-phenylglycine methylester (1a) with SiCl4 in presence of triethylamine leads to planarization of the amino acid ester and formation of a ketene acetal 2a. The reaction of N-(salicylidene)- L-valinmethylester (1b) with SiCl4 without triethylamine leads to racemization of the amino acid ester and formation of the complex 2b. A mechanism for the formation of both products has been proposed. It is possible to transfer the chiral information present in the ligand system into the complex by using dichlorodimethylstannane for the complex formation. Dimethyltin[N-(salicylidene)-D-phenylglycine methylester] (3a) crystallizes in the chiral space group P212121 with one diasteromer in the asymmetric unit. 1H NMR analysis of 3a with the help of a lanthanide shift reagent proves the presence of only one diasteromer in the bulk material.

The reaction of dichlorodiphenylsilane with a polydentate Schiff base ligand derived from pyridoxal and 2-hydroxyaniline yields the macrocyclic centrosymmetric silicon compound 9,27-dimethyl-3,3,21,21-tetraphenyl-2,4,20,22-tetraoxa-8,13,26,31-tetraaza-3,21-disilapentacyclo[30.4.0.0(6,11).0(14,19).0(24,29)]hexatrideca-1(32),6,8,10,12,14,16,18,24,26,28,30,33,35-tetradecaene-10,28-diol chloroform tetrasolvate, C(52)H(44)N(4)O(6)Si(2) x 4CHCl(3). The asymmetric unit contains half of the macrocycle and two molecules of chloroform, with C-H...O and C-H...N contacts binding the two guests to the host in the crystal structure. This macrocyclic silicon compound represents a promising host for molecular-recognition processes and for the construction of nanostructures.

Defined crystalline amino-substituted organosilanes were prepared by reaction of N-methylaniline with 1,1,2,2-tetrachlorodimethyldisilane and other chloroorganosilanes. The X-ray structure analyses of 1,2-dichloro-1,2-bis(N-methyl-anilino)dimethyldisilane (1), 1-chloro-1,2,2-tris(N-methylanilino)dimethyldisilane (2) and tetrakis(N-methylanilino)-1,2-dimethyldisilane (3) were performed. The absolute structure of 1 was determined by crystallographic methods. 1,2-Dichloro -1,2-bis(N-methylanilino)dimethyldisilane (1) is a useful reagent for the preparation of a variety of other aminoorganodisilanes.