Structural And Oxidation State Alternatives In Platinum And Palladium Complexes Of A Redox-Active Amidinato Ligand

Reaction of [Pt(DMSO)(2)Cl-2] or [Pd(MeCN)(2)Cl-2] with the electron-rich LH = N,N'-bis(4-dimethylaminophenyl)ethanimidamide yielded mononuclear [PtL2] (1) but dinuclear [Pd2L4] (2), a paddle-wheel complex. The neutral compounds were characterized through experiments (crystal structures, electrochemistry, UV-vis-NIR spectroscopy, magnetic resonance) and TD-DFT calculations as metal(II) species with non-innocent ligands L-. The reversibly accessible cations [PtL2](+) and [Pd2L4](+) were also studied, the latter as [Pd2L4][B{3,5-(CF3)(2)C6H3}(4)] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [Pt-II(L-)(2)] or [Pt-center dot(L)(2)], [Pt-II(L0.5-)(2)](+) or [Pt-III(L-)(2)](+), [(Pd-II)(2)(mu-L-)(4)] or [(Pd-1.5)(2)(m-L0.75-)(4)], and [(Pd-2.5)(2)(mu-L-)(4)](+) or [(Pd-II)(2)(mu-L0.75-)(4)](+). In each case, the first alternative was shown to be most appropriate. Remarkable results include the preference of platinum for mononuclear planar [PtL2] with an N-Pt-N bite angle of 62.8(2)degrees in contrast to [Pd2L4], and the dimetal (Pd-2(4+) -> Pd-2(5+)) instead of ligand (L- -> L) oxidation of the dinuclear palladium compound.