In 1984, Kubas and co-workers determined the molecular structure of W(PiPr3)2(CO)3(eta2-H2) by a single crystal neutron diffraction study. This seminal study established that molecular hydrogen could bind to a metal center in a “side-on” fashion without cleavage of the H-H bond forming the corresponding dihydride, (H)2. The terms Kubas-compound and Kubas-interaction are now familiar to all scientists working in the areas of metal hydrides and physi-sorbed hydrogen. The bonding in a Kubas complex is described as involving a donation of electrons from the H2 σ orbital to a linear empty metal valence orbital and a back-bonding interaction from a filled metal dπ orbital to the empty σ* orbital of the H2. In the Kubas interaction, the H2 ligand acting as σ base is emphasized. The bonding of an H2 ligand to a metal center that does not involve a non-classical Kubas interaction, but rather an unusual “end-on” interaction, involves a 3-center 4-electron bond. In the end-on bonding model, the H2 ligand acting as a σ* acid is emphasized. We recently determined the molecular structure of Ir(η1-H2){C6H3(OAsBut2)2-2,6} through a single crystal X-ray diffraction study. Surprisingly, upon refinement, the H2 ligand was found to be situated in an “end-on” rather than “side-on” coordination motif. This talk will discuss the details of the (η1-H2) bonding mode and characterization methods. Also, through the studies of Ir(η1-H2){C6H3(OAsBut2)2-2,6}, and the possible discrete (η1-H2) coordination, we have revisited an earlier project from the Jensen lab. In order to gain insight into the mechanism for facile interconversion of (H)2 and (η2-H2) in an alternate iridium system, an (η1-H2) intermediate has been explored and will be discussed as well.

New perspective into the mechanism for the highly facile interconversion of (H)2 and (η2-H2) in an iridium system: through an (η1-H2) interaction?

255th National Meeting (2018)

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