Bis(catecholato)germane: an effective catalyst for Friedel-Crafts alkylation reaction.

Bis(catecholato)germane, [Ge(C 6 H 4 O 2 ) 2 (H 2 O) 2 ] (1), was synthesized by the reaction of catechol and germanium oxide in water according to a reported method. Complex 1 was characterized by FT-IR spectroscopy, NMR spectroscopy and elemental analysis. Complex 1 was employed as a Lewis acid catalyst in the Friedel-Crafts alkylation reaction of indole with various aldehydes and β-nitrostyrene derivatives separately. The yield of the product for the formation of bis(indolyl)alkanes and nitroalkylated indoles was up to 95% and 96%, respectively. These observations confirmed the catalytic efficacy of complex 1 as a Lewis acid in both reactions. Based on the experimental findings, a plausible mechanism is proposed for both reactions.