Insights into metal-ligand hydrogen transfer: a square-planar ruthenate complex supported by a tetradentate amino-amido-diolefin ligand.

A four-coordinate, sixteen-electron Ru(0) complex containing the tetradentate diamino-diolefin ligand (±)-trans-N,N-bis(5H-dibenzo[a,d]cyclohepten-5-yl)-1,2-diaminocyclohexane (trop2dach) has been synthesised. Deprotonation of one amino N-H functional group generates an unprecedented four-coordinate ruthenate species which has been characterised in solution and in the solid state. The newly formed ruthenate complex undergoes intramolecular metal-ligand N-H addition/elimination in solution to generate a transient diamido ruthenium hydride species, as supported by NMR spectroscopy and density functional theory.