Abstract
The tetra(pyridyl)cyclobutadiene complexes [K([18{crown-6){Cp*FeC4(3-py)(4)}] (2) (3-py = 3-pyridyl) and [K([18{crown-6){Cp*FeC4(4-py)(4)}] (3) (4-py = 4-pyridyl) were synthesized by reacting two equivalents of bis(3-pyridyl)acetylene and bis(4-pyridyl)acetylene with the naphthalene complex [K([18{crown-6){Cp*Fe((4)-C10H8)}]. Compounds 2 and 3 were fully characterized by X-ray crystallography, ...
Abstract
The tetra(pyridyl)cyclobutadiene complexes [K([18{crown-6){Cp*FeC4(3-py)(4)}] (2) (3-py = 3-pyridyl) and [K([18{crown-6){Cp*FeC4(4-py)(4)}] (3) (4-py = 4-pyridyl) were synthesized by reacting two equivalents of bis(3-pyridyl)acetylene and bis(4-pyridyl)acetylene with the naphthalene complex [K([18{crown-6){Cp*Fe((4)-C10H8)}]. Compounds 2 and 3 were fully characterized by X-ray crystallography, H-1 and C-13{H-1} NMR spectroscopy, UV/Vis spectroscopy, and elemental analysis. They display similar sandwich structures with an (5)-coordinated Cp* unit and an (4)-coordinated cyclobutadiene moiety. In the solid state, compounds 2 and 3 form distinct polymeric chain structures due to the interaction of the pyridyl nitrogen atoms with the potassium cations. Cyclic voltammetry measurements indicate that the [Cp*FeC(4)py(4)](-) anions (py = 3-py or 4-py) undergo a reversible one electron oxidation to neutral [Cp*FeC(4)py(4)] complexes. A second quasi-reversible redox event is attributed to the oxidation these products to unstable [Cp*FeC(4)py(4)](+) cations. The properties of 2 and 3 are compared with those of the previously reported 2-pyridyl complex [K([18{crown-6){Cp*FeC4(2-py)(4)}] (1) [Dalton Trans. 2014, 43, 4247-4250].
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