Syntheses and structural characterization of mononuclear Rh–Cp* and Ir–Cp* complexes with η6-phenanthrene, η6-pyrene and η6-triphenylene

Four novel mononuclear Rh–Cp* and Ir–Cp* complexes with polycyclic aromatic hydrocarbons (PAHs), [M(Cp*)(η6-PAHs)](BF4)2 (M = Rh and Ir; Cp* = η5-C5Me5; PAHs = phenanthrene (phn), pyrene (pyr) and triphenylene (triph)), were prepared by the reactions of the intermediate [M(Cp*)(Me2CO)3]2+ with appreciable PAHs. Their structures were characterized by a single crystal X-ray analysis, 1H, 13C {1H} NMR and 2D NMR techniques. The X-ray crystallographic studies showed that the [M(Cp*)]2+ fragment is η6-coordinated to one terminal benzene ring in each PAH. In particular, it is interesting to note that the partial π/π/π/π interaction was formed in the Ir–pyr complex [Ir(Cp*)(η6-pyr)](BF4)2. The 1D and 2D NMR studies described that the Rh–Cp* and Ir–Cp* complexes with PAHs gave unique 1H and 13C {1H} NMR spectra with positive coordination shifts (Δδ(1H, 13C)) in (CD3)2CO at 23 °C, which are likely induced by the local effect and the non-local effect on the coordination of the [M(Cp*)]2+ fragment to PAHs. The decreasing of the coupling constants (3JH–H) in the η6-coordinated benzene ring is also induced, with no changes in the uncoordinated benzene rings. The time-course of 1H NMR spectra showed that Rh–Cp* and Ir–Cp* complexes with PAHs are partially dissociated to [M(Cp*)(Me2CO)3]2+ and metal-free PAHs in (CD3)2CO at 23 °C. It was demonstrated that their stabilities are in the order of Ir–triph, Ir–phn, Ir–pyr and Rh–triph complexes in (CD3)2CO.

Four novel mononuclear Rh–Cp* and Ir–Cp* complexes with polycyclic aromatic hydrocarbons (PAHs), [M(Cp*)(η6-PAHs)](BF4)2 (M = Rh and Ir; Cp* = η5-C5Me5; PAHs = phenanthrene (phn), pyrene (pyr) and triphenylene (triph)) were prepared by the reactions of the intermediate [M(Cp*)(Me2CO)3]2+ with appreciable PAHs. Their structures were characterized by a single crystal X-ray analysis, 1H, 13C {1H} NMR and 2D NMR techniques.Figure optionsDownload as PowerPoint slide