MULTIELECTRON TRANSFER AND SINGLE-CRYSTAL X-RAY STRUCTURE OF A TRINUCLEAR CYANIDE-BRIDGED PLATINUM IRON SPECIES

[Pt(NH3)4]2[(NC)5FeII–CN–PtIv(NH3)4–NC–FeII(CN)5]•9H2O was synthesized by the redox reaction of Pt(NH3)4(NO3)2 and K3Fe(CN)6 in aqueous solution. The red complex crystallized in space group P21/c (No. 14) and was analyzed by X-ray diffractometry. The monoclinic crystal consists of a trinuclear, cyanide-bridged Fe–Pt–Fe anion hydrogen-bonded via a terminal cyanide group on each iron atom to two separate tetraammineplatinum(II) counterions. Unit cell dimensions are a = 15.313 (2) Å, b = 8.5353 (14) Å, c = 16.206 (5) Å, β = 100.52 (2)°, and Z = 2; a center of inversion exists at the central Pt atom of the trinuclear anion. The R factors for this structure are R = 5.0% and Rw = 5.3%. On the basis of infrared spectroscopy, magnetic measurements, ESR spectroscopy, and the electrochemistry of the compound, localized oxidation states of FeII–PtIV–FeII are assigned to the complex. The electronic spectrum reveals an intervalent (IT) charge-transfer absorption at approximately 470 nm. Excitation into this band effects an electron transfer between the Fe11 and PtIv atoms and results in the formation of Pt(NH3)42+ and ferricyanide in a 1 to 2 ratio. The initial quantum yield for the formation of ferricyanide at 488-nm irradiation is 0.02. © 1990, American Chemical Society. All rights reserved.