C-P bond forming reactivity of N-heteropentacene: isolation and characterization of a phospho-ylide complex of ruthenium(II)

Abstract

In an unusual reaction of H₂L² (H₂L²=N-heteropentacene) with Ru(PPh₃)₃Cl₂ a phospho-ylide ruthenium(II) complex (1) was obtained via unprecedented chemical transformations of the conjugate base [L²]^2-. A bidentated phospho-ylide ligand is formed with concomitant aromatic ring hydroxylation and new C-P bond formation reactions. The new ligand, binds to Ru^II as a neutral N, O-donor. Crystal structure determination by single crystal X-ray diffraction has been used to characterize the compound. The phospho-ylide Ru(II) description of the complex was established based on ¹³C as well as ³¹P NMR studies. The complex shows rich spectral and redox properties. UV-Vis-NIR spectrum consisted of multiple low-energy transitions in the visible and near IR regions. Preliminary density functional theory calculations were employed to understand the electronic structure and to assign the spectral transitions. Cyclic voltammogram and EPR-spectrum of the electrogenerated oxidized compound are reported and used to characterize the redox properties.