Iridium(I) complex of chelating pyridine-2-thiolate ligand: Synthesis, reactivity, and application to the catalytic E-selective terminal alkyne dimerization via C–H activation

Abstract

A novel iridium(I) complex bearing a chelate-coordinated pyridine-2-thiolate ligand [Ir(η 2-SNC 5H 4)(PPh 3) 2] ( 2) was prepared by the reaction of iridium ethylene complex [IrCl(C 2H 4)(PPh 3) 2] ( 1) with lithium salt of pyridine-2-thiol (Li[SNC 5H 4]). On the treatment of iridium(I) complex 2 with chloroform, iridium(III) dichloro-complex [IrCl 2(η 2-SNC 5H 4)(PPh 3) 2] ( 3) was formed. Reactions of complex 2 with methyldiphenylsilane, acetic acid, and p-tolylacetylene afforded iridium(III) hydride complexes [IrH(SiMePh 2)(η 2-SNC 5H 4)(PPh 3) 2] ( 4), [IrH(O 2CCH 3)(η 2-SNC 5H 4)(PPh 3) 2] ( 5), and [IrH(C C( p-tolyl))(η 2-SNC 5H 4)(PPh 3) 2] ( 6), respectively. Complex 2 catalyzed dimerization of terminal alkynes leading to enynes ( 7) with high E-selectivity via C–H bond activation.