Rhodium(I) and iridium(I) complexes containing bidentate phosphine-imidazolyl donor ligands as catalysts for the hydroamination and hydrothiolation of alkynes

摘要

A series of novel cationic and neutral rhodium and iridium complexes containing bidentate phosphine-imidazolyl donor ligands of the general formulae [M(ImP)(COD)]BPh4 (M = Rh, ImP ImP2,3; ImP1a, 4a; ImP1b, 4b and M = Ir, ImP = ImP2,5; ImP1a, 6a and ImP1b, 6b), [Ir(Imp)(CO)(2)]BPh4 (ImP = ImP2,7; ImP1a, 8a and ImP1b, 8b), [Rh(ImP1b)(CO)(2)]BPh4 (10b) and [M(ImP)(CO)Cl] (M = Rh, Imp = ImP2, 11; ImP1b, 12 and M = Ir, ImP = ImP2, 13; ImP1b, 14) where COD = 1,5-cyclooctadiene, ImP2 = 1-methyl-2-[(2-(diphenylphosphino)ethyl]imidazole, 1; ImP1a = 1-methyl-2-[(diphenylphosphino)methyl]imidazole, 2a and ImP1b = 2-[(diisopropylphosphino)methyl]I -methylimidazole, 2b were successfully synthesised. The solid state structures of 3, 6a, I I and 12 were determined by single crystal X-ray diffraction analysis. A number of these complexes are effective as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine to 2-methyl-1-pyrroline. The cationic complexes are significantly more effective than analogous neutral complexes. The cationic iridium complex 8b, containing the phosphine-imidazolyl ligand with the bulky isopropyl groups on the phosphorus donor, is more efficient than analogous complexes with the phenyl substituents oil the phosphorus donor atom, 7 and 8a. The complexes 7-8b are also moderately effective in catalysing the addition of thiophenol to a range of terminal alkynes. In contrast to the hydroamination reaction, placement of the isopropyl group Oil the phosphorus donor leads to a decrease in the reactivity of the resulting Metal complexes as catalysts for the hydrothiolation reaction.