International audienceTwo series of ruthenium carbonyl complexes bearing either one secondary phosphine oxide ligand or two phosphinous acids have been synthesized and characterized. The catalytic behavior of these complexes has been then investigated for the cycloisomerization of arenynes. This study highlighted a strong relationship between ligands’ and substrates’ substructures

A series of [RuCl2(η(6)-p-cymene)] complexes bearing phosphinous acid (PA) ligands have been straightforwardly prepared from the dimer [RuCl2(p-cymene)]2 and secondary phosphine oxides (SPOs) and fully characterized. The steric parameter quantification of PAs, other L ligands and η(6)-p-cymene allowed a better comprehension of the coordination chemistry of these types of complexes and explained the absence of coordination in the case of bulky SPOs such as Ad2P(O)H. These complexes were tested in the C-H activation/functionalization of 2-phenylpyridine and a good activity was obtained at 80 °C for the complex exhibiting the highest steric bulk. A study on halide effects, either on the ruthenium complex or for the aryl halide partner, has also been carried out showing drastic differences. Further investigations on halide effects were performed notably by using a cationic ruthenacycle which was found to be an intermediate for the reaction. In order to rationalize the role played by the phosphinous acid, a mechanism involving a concerted metallation deprotonation favored by a phosphinito species has been proposed.