A study of chirality in bis(1,2-dimethoxyethane-κ²O,O′)sodium bis(tri-tert-butoxysilanethiolato-κ²O,S)sodate

Abstract

This work presents an analysis of self-assembly of a complex molecule from simpler ions, some of which are asymmetric, and is an example of a sodium silanethiolate. The tri-tert-butoxysilanethiolate anion has two helical conformers (P and M), so aggregation of silanethiolates can proceed with recognition of chirality. Alkali metal silanethiolates can form cyclic solvated oligomers (e.g. dimers) or complexes such as sodates with anions of general formula R2Na(-). We note that all known sodates (and lithiates) contain both ligands of the same helicity in the anion, whereas in the dimers the metal atoms are coordinated by silanethiolate ligands of different helicity. The title compound, a new example of a sodate, [Na(C4H10O2)2][Na(C12H27O3SSi)2] or [Na{((t)BuO)3SiS}2][Na(DME)2] (DME is 1,2-dimethoxyethane), is built up of separate ion pairs with no significant interactions. The anion is formed from an Na atom O,S-chelated by two silanethiolate ligands of the same helicity (both P or both M), while the cation contains an Na atom solvated by two DME molecules. Because the structure is centrosymmetric, equal numbers of both conformational enantiomers are present in the crystal lattice.

Intramolecular Interactions in Crystals of Tris(2,6-diisopropylphenoxy)silanethiol and Its Sodium Salts

“…Sodium silanethiolates 2 , 3 , and 4 were obtained in the reaction of sodium metal with TDST in n -hexane solution similar to the sodium thiolates and silanethiolates , described previously. The reaction in n -hexane was rather slow, requiring continuous stirring and heating.…”

“…Systematic studies undertaken to analyze the influence of metal, ligand, and solvent on the structure of thiolates of group 1 elements were reviewed . Because of the well recognized ability of thiolato ligands to form bridges between metal ions, alkali metal thiolates exhibit the varying extent of aggregation; they crystallize as rare, mononuclear species, common, four-membered M 2 S 2 rings, ,, ladders, ,, cubanes, ,, or other coordination oligomers and polymers. ,,,, The aggregation can be prevented by the increase of the steric hindrance of thiolato ligand ,,, and/or addition of coligands such as tetrahydrofuran ,,, or N , N , N ′, N ′-tetramethylethylenediamine. ,,,, It is possible to obtain crystalline compounds with separate or contact thiolato anions and alkali metal cations surrounded either by water or crown ethers. ,,, Quite unusual ion pairs of different character, 2Li­(TBST) 2 – Li 2 (D 2 O) 6 2+ and Na­(TBST) 2 – Na­(DME) 2 + , were structurally characterized by the researchers from our department. Introduction of other functional groups into the molecule of thiol greatly influences the structure of the resulting alkali metal thiolate (e.g., ref ), but this research is not reviewed in detail here.…”

Propeller-Like Chirality of Methyl-Tris (2,6-diisopropylphenoxy)Silylsulfide

“…After Chojnacki [2] the enantiomers will be called P (all torsion angles S-Si-O-C positive) and M (the same torsion angles negative). Apart from the sign of the appropriate torsion angle, these aromatic derivatives possess an additional element of helicity introduced by the twist of the aromatic rings with regard to the reference plane (compare [13, (15) 14]).…”

“…observed and described by Chojnacki for solid tri-tertbutoxysilanethiolato complexes [2,3]. In this contribution we describe a similar type of propeller chirality in aromatic analogue of tri-tert-butoxysilanethiol obtained more recently, tris(2,6-diisopropylphenoxy)silanethiol TDST [4] and its methyl derivative.…”

“…Sodium silanethiolates were obtained as described before [2,4]. Methyl iodide (Sigma-Aldrich) was used as purchased.…”