Redox-Transmetalation Reactions: Easy Access to Homo- and Heterodimetallic d,d Complexes.

The ability of the imine PyCH═N-CHPy (Py = 2-pyridyl, bpi) to behave as a heteroditopic ligand, which is suitable for creating two separate compartments to host metals in different oxidation states, has been developed by studying the reactions of the mixed-valence complexes [(cod)M(μ-bpi)M(cod)] (M = Rh, Ir) with [M'(Cl)(PPh)] (M' = Pd, Ni). The results depend on the molar ratio of the reagents used (1:1 or 1:2) to give the heterometallic complexes {d-M',d-M}-[(PPh)(Cl)M'(μ-bpi)M(cod)] (Pd,Rh, ; Pd,Ir, ; Ni,Rh, ; Ni,Ir, ) and the two-electron mixed-valent compounds [(PPh)(Cl)M'(μ-bpi)M'(Cl)] (M' = Ni, ; Pd, ), respectively. A redox process occurs in the replacement of the low-valent [(cod)M] fragment, whereas the exchange of the [(cod)M] fragment is redox-neutral. The metal with a d configuration in the products exhibits a square-planar geometry coordinated to two (Rh/Ir) or three (Ni/Pd) nitrogen atoms of the bridging bpi ligand. Conversely, the metal with a d configuration adopts trigonal-planar geometries, π-bonded to the imine C═N bond. The isolated complexes / and , along with the hypothetical heterometallic Pd,Ni compound (), were studied by DFT methods. Additionally, the T-shaped moiety 'M'(PPh)(Cl)(η-CH-N(bpi))', stabilized by a secondary γ-agostic interaction, and the 'M'(Cl)(κ-bpi)' fragment was found to be accessible redoxomers of complexes and by DFT calculations.