Synthesis, coordination chemistry, and cooperative activation of H ₂ with ruthenium complexes of proton-responsive METAMORPhos ligands

The synthetic scope of proton-responsive sulfonamidophosphorus (METAMORPhos) ligands is expanded and design principles for the selective formation of particular tautomers, ion pairs, or double condensation products are elucidated. These systems have been introduced in the coordination sphere of Ru for the first time, thereby enabling the exclusive coordination as a monoanionic P,O chelate. Depending on the Ru precursor, halide-bridged dinuclear species 3-5 or cymene-derived piano-stool complexes 6-9 are isolated. The METAMORPhos framework is shown to play a role in the heterolytic cleavage of H₂, with species 7 converted into neutral monohydride 10. Substitution chemistry with cymene complex 7 has also been examined, thereby giving rise to tetrakis(acetonitrile) adduct 11. Introduction of a second equivalent of METAMORPhos ligand to this species yielded the bis(ligated) derivative 13, for which variable-temperature (VT) NMR spectroscopy indicates coalescence of the phosphine donors at high temperature. Solid-state structures of 3, 6, 11, and 13 are presented to establish the precise bonding situation of the inorganic PNSO framework within METAMORPhos upon coordination as a proton-responsive monoanionic P,O chelate.