Formation of different ruthenium(ll)-indole zwitterion complexes via metal-induced cycloisomerization of aniline-tethered alkynes

Abstract

Isolation of C-2 metalated ruthenium–indole zwitterion complex (1a) and C-3 metalated ruthenium-indole zwitterion complex (1b), derived from the reaction between [Ru([9]aneS3)(bpy)(OH2)](ClO4)2 and aniline tethered alkyne derivatives has been achieved. Spectroscopic studies on complex 1a and 1b were carried out and their molecular structure were determined by the X-ray crystallography. Mechanistic studies based on the reaction temperature and modification of ligand was conducted experimentally. The selectivity between a "vinylidene-involving pathway" and the "direct 5-endo-dig cyclization pathway" for the formation of 1a and 1b has been achieved by lowering down the activation barrier of the formation of Ru–vinylidene intermediate.