X-ray crystal and molecular structure of an organometallic hydrazone containing a zigzag π-conjugated spacer: [CpFe(η⁶-C ₆H₅)-N(Me)N=CH-C₆H₄-4-NMe ₂]⁺PF₆^-

The crystal and molecular structure of the complex [CpFe(η⁶- C₆H₅)-N(Me)N=CH-C₆H₄-4-NMe ₂]⁺PF₆^-, [1]⁺PF ₆^-, was solved by single crystal X-ray diffraction analysis. One of the most salient features observed in this structure is the depyramidalization of both the benzylic nitrogen and the dimethylamino nitrogen atoms which reveals the delocalization of the π-electron system along the entire hydrazone skeleton from the donor to the acceptor termini, through a quinonoidal deformation and a pseudo-cyclohexadienyl conformation (folding dihedral angle of ca. 7.4°) of the free and coordinated phenyl rings, respectively. Both C_ipso-N bond lengths are virtually identical (1. 37 Å), lying between pure single and double bonds. These and other peculiarities are described and compared with the structures of other organometallic hydrazones.