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

A novel iridium(I) complex bearing a chelate-coordinated pyridine-2-thiolate ligand [Ir(eta(2)-SNC5H4)(PPh3)(2)](2) was prepared by the reaction of iridium ethylene complex [IrCl(C2H4)(PPh3)(2)] (1) with lithium salt of pyridine-2-thiol (Li[SNC5H4]). On the treatment of iridium(I) complex 2 with chloroform, iridium(III) dichloro-complex [IrCl2(eta(2)-SNC5H4)(PPh3)(2)] (3) was formed. Reactions of complex 2 with methyldiphenylsilane, acetic acid, and p-tolylacetylene afforded iridium(III) hydride complexes [IrH(SiMePh2)(eta(2)-SNC5H4)(PPh3)(2)] (4), [IrH(O2CCH3)(eta(2)-SNC5H4)(PPh3)(2)](5), and [IrH(C C(p-tolyl))(eta(2)-SNC5H4)(PPh3)(2)] (6), respectively. Complex 2 catalyzed dimerization of terminal alkynes leading to enynes (7) with high E-selectivity via C-H bond activation. (c) 2007 Elsevier B.V. All rights reserved.