Structural and oxidation state alternatives in platinum and palladium complexes of a redox‐active amidinato ligand

Abstract

Reaction of [Pt(DMSO)2Cl2] or [Pd(MeCN)2Cl2] 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 noninnocent ligands L-. The reversibly accessible cations [PtL2]+ and [Pd2L4]+ were also studied, the latter as [Pd2L4][B{3,5‐(CF3)2C6H3}4] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [PtII(L-)2] or [Pt.(L )2], [PtII(L0.5-)2]+ or [PtIII(L-)2]+, [(PdII)2(μ‐L−)4] or [(Pd1.5)2(μ‐L0.75-)4], and [(Pd2.5)2(μ‐L-)4]+ or [(PdII)2(μ‐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)° in contrast to [Pd2L4], and the dimetal (Pd24+→Pd25+) instead of ligand (L-→L ) oxidation of the dinuclear palladium compound.