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·BH₃ (1) with potassium alkoxides KOR provided potassium hydrido-alkoxo-germanato-borates {K(THF)₂[BH₃·Ge(L)(H)(OR)]}₂ (R = tBu (2), C(CH₃)₂CH₂CH₃ (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·BH₃ (1). Thus complex 1 was tested as a useful catalyst for esterification of aldehydes by KO^tBu. The GC-MS analysis revealed formation of t-butyl esters of appropriated carboxylic acids. The mechanistic studies for the esterification of benzaldehyde with KO^tBu catalyzed by 1 were also performed either theoretically (DFT calculations), or experimentally (NMR and IR spectroscopy).