Bis(o-Aminophenolato)germanium(II) and Tin(II) Complexes in Hydroboration Reactions of Aromatic Aldehydes

Stable tin(II) (^dippAmP)₂Sn (I) and germanium(II) (^dippAmP)₂Ge (II) complexes based on 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-aminophenol were synthesized and characterized. The compounds are monomeric and contain, in addition to covalent element(II)–oxygen bonds, additional coordination bonds involving the secondary amino groups of the chelating ligand. The synthesized compounds were tested as homogeneous catalysts for the hydroboration of various substituted aldehydes to the corresponding boronate esters. Optimization of the catalytic reaction conditions made it possible to reduce the catalyst loading to 0.02 mol % while maintaining quantitative conversion under mild conditions. The molecular structure of complex II was established by X-ray diffraction analysis (CCDC no. 2423247, II).