Mixed-valent linear chain Pt₂PdPt₂ complexes

Pentanuclear linear-chain PtPd complexes {[Pt₂(NH ₃)₂X₂(μ-pivalamidato)₂(CH ₂COCH₃)]₂[PdX′₄]} ·2CH₃COCH₃ (X = X′ = Cl (1a), X = Cl, X′ = Br (1b), X = Br, X′ = Cl (1c), X = X′ = Br (1d)) composed of a monomeric Pd^II complex sandwiched by two amidato-bridged dimeric Pt^III units were synthesized from the reaction between the acetonyl dinuclear Pt^III complexes having equatorial halide ligands [Pt₂(NH₃)₂-X₂(μ-pivalamidato) ₂(CH₂COCH₃)]X″ (X = Cl (2a), Br (2b), X″ = NO₃^-, CH₃C₆H ₄SO₃^-) and K₂[PdX′ ₄] (X′ = Cl, Br). The X-ray crystallographic analysis of 1a-1d shows that the complexes have metal-metal bonded linear Pt₂PdPt ₂ structures. The pentanuclear PtPd complexes have either an arch backbone structure or a sigmoid backbone structure, depending on the solvent of crystallization. The UV/Vis/NIR spectra clearly show the existence of a rare charge-transfer band from Pd to Pt in the pentanuclear PtPd complexes.