M(μ-CN)Fe(μ-CN)M‘ Chains with Phthalocyanine Iron Centers: Preparation, Structures, and Isomerization

The molecular building blocks Fe(II)Pc (Pc = phthalocyaninato2-), Fe(III)Pc, ZnPc, Cp(dppe)Fe, and Cp(PPh3)2Ru were combined in the cyanide-bridged dinuclear reference compounds with M−CN−ZnPc and M−CN−FePc−CN arrays containing Fe(II)Pc and Fe(III)Pc. The linear trinuclear species with the M(μ-CN)Fe(μ-CN)M‘
backbone were prepared for both Fe(II)Pc and Fe(III)Pc centers, for terminal Fe/Fe, Fe/Ru, and Ru/Ru combinations
and for all three possible cyanide orientations (M−CN−Fe−NC−M‘, M−CN−Fe−CN−M‘, and M−NC−Fe−CN−M‘). The 15 complexes obtained were identified from their IR spectra and six structure determinations. The
preferred orientation of the cyanide bridges could be established starting from the [Fe−NC−Fe(III)Pc−CN−Fe]+ complex, which is labile in solution and isomerizes to the corresponding [Fe−CN−Fe(III)Pc−NC−Fe]+
complex. A kinetic analysis of this isomerization has yielded an activation barrier of roughly 110 kJ/mol.