Rhodium(i) and iridium(i) complexes with bidentate N,N and P,N ligands as catalysts for the hydrothiolation of alkynes

Abstract

Cationic iridium(I), rhodium(I) complexes containing bis(1-methylimidazol-2-yl)methane, bim, [M(bim)(CO)₂]BPh₄ (M = Ir (1), Rh (2)); bis(pyrazol-1-yl)methane, bpm, [M(bpm)(CO)₂]BPh₄ (M = Ir (3), Rh (4)) have been shown to be effective in catalysing the regioselective addition of thiophenol to a series of alkynes. Analogous cationic and neutral Ir(I), Rh(I) complexes with the novel mixed P,N-donor bidentate ligand 1-(2-diphenylphosphino)ethylpyrazole, PyP (5), [M(PyP)(COD)]BPh₄ (M = Ir (6), Rh (7), COD = 1,5-cyclooctadiene); [Rh(PyP)(COD)]BF₄ (8); [Ir(PyP)(CO)₂]BPh₄ (9); [Rh(PyP)(CO)₂]BF₄ (10); [M(PyP)(CO)Cl] (M = Ir (11), Rh (12)) have also been synthesised, and characterised by NMR. The solid-state structures of (6), (7), (11) and (12) have been determined by single-crystal X-ray diffraction analysis. The metal complexes (9)–(12) with the mixed P,N-donor ligand, PyP are in most cases more effective in promoting the hydrothiolation of alkynes in comparison with the analogous complexes (1)–(4) with N,N-donor ligands. The iridium complexes were significantly more effective than their rhodium analogues in promoting the hydrothioloation of alkynes. The cationic complexes (9) and (10) are more effective as catalysts for the hydrothiolation of alkynes than their neutral analogues (11) and (12).