Electrochemistry and spectroelectrochemistry (EPR, UV-visible-near-IR) of platinum(II) 2,2'-bipyridine and ring-metalated bipyridine complexes: PtII(L-) and PtI(L-) but not PtI(L)

, , , , , , und . Inorganic Chemistry 31 (24): 5084--5088 (1992)


The Pt(II) complexes Pt(bpy)(py)22+, Pt(bpy)(Me2N-py)22+, Pt(Me2-bpy)(py)22+, Pt(bpy)(en)2+, Pt(Mebpy - H)(py)22+, Pt(Mebpy - H)(bpy)2+ (VI), Pt(phen)(py)22+, and Pt(py)42+ (VIII) (bpy, 2,2'-bipyridine; py, pyridine; Mebpy - H, N-methyl-2,2'-bipyridinium-3-yl-C,N'; Me2-bpy, 4,4'-dimethyl-2,2'-bipyridine; Me2N-py, 4-(dimethylamino)pyridine; en, 1,2-diaminoethane; phen, 1,10-phenanthroline) have been investigated by cyclic voltammetry and where possible by EPR spectroelectrochem. and by UV-vis-near-IR spectroelectrochem. All complexes except VIII show at least two reversible reductive one-electron processes; VI shows three, and VIII shows one chem. irreversible process. In all cases, the doubly reduced species showed the characteristic p* $\rightarrow$ p* UV-visible-near-IR absorptions of the ligand anion radicals. For the singly reduced species, EPR spectra show the added electron to be localized on the bipyridine-type ligand. However, the UV-visible-near-IR spectra of these species are not typical of ligand-based redn. products, and the potentials are less neg. than expected for such a process. It is concluded that the singly reduced species are best formulated as contg. Pt(II), with the semioccupied and/or th lowest unoccupied ligand orbitals (corresponding to the LUMO and SLUMO of the unreduced parent species) being perturbed by the presence of metal orbitals. The doubly reduced species, however, are straightforward anion radical complexes of Pt(I). on SciFinder(R)

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