C,N-Chelated Organogermanium(II) Hydride as Catalyst for Esterification of Aldehydes.

The reactions of the monomeric C,N-chelated organogermanium(II) hydride L(H)Ge·BH (1) with potassium alkoxides KOR provided potassium hydrido-alkoxo-germanato-borates {K(THF)[BH·Ge(L)(H)(OR)]} (R = tBu (2), C(CH)CHCH (3)) as products of KOR addition. Compounds 2 and 3 react with benzaldehyde under formation of alkyl esters of benzoic acid along with elimination of a neutral complex L(H)Ge·BH (1). Thus complex 1 was tested as a useful catalyst for esterification of aldehydes by KOBu. The GC-MS analysis revealed formation of t-butyl esters of appropriated carboxylic acids. The mechanistic studies for the esterification of benzaldehyde with KOBu catalyzed by 1 were also performed either theoretically (DFT calculations), or experimentally (NMR and IR spectroscopy).