Synthesis, molecular and crystal structure, and stereochemical non-rigidity of (O→Ge)-Bischelate bis[1-(2-oxoperhydroazepinyl)methyl]bromogermanium iodide and triflate

Negrebetsky, Vad.V; Korlyukov, A.A; Bylikin, Sergey; Kramarova, E.P and Baukov, Yul (2020). Synthesis, molecular and crystal structure, and stereochemical non-rigidity of (O→Ge)-Bischelate bis[1-(2-oxoperhydroazepinyl)methyl]bromogermanium iodide and triflate. Journal of Organometallic Chemistry, 916, article no. 121244.

DOI: https://doi.org/10.1016/j.jorganchem.2020.121244

Abstract

Reactions of (O→Ge)-bischelate dibromogermane (L7CH2)2GeBr2 (4c) with trimethyliodosilane and trimethylsilyl triflate proceed with the substitution of only one bromine atom and yield (O→Ge)-bischelate monobromogermanes (L7CH2)2Ge(Br)X (8c, X = I; 9c, X = OTf; LnCH2 = lactamomethyl C,O-chelate ligand; n = lactam ring size). According to X-ray crystal analysis data, triflate 9c is characterized by nearly ionic structure with the monodentate ligand and anion in trans-positions. The configuration of the germanium atom in the complex is intermediate between trigonal bipyramidal and square pyramidal. Quantum chemical calculations show the absence of additional coordinate bonding between the germanium atom and anion.

Dynamic 1H NMR spectroscopy (1H DNMR) was used to study the stereochemical non-rigidity of monobromides 8c and 9c. Activation parameters for the inversion of the germanium atom configuration were calculated in various solvents. Based on the 1H DNMR data and quantum chemistry calculations, possible mechanisms of permutational isomerization are discussed.

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