Organometallic–inorganic charge transfer salts containing a cationic iron mixed sandwich and polyoxomolybdate anions: Syntheses, X-ray molecular structures and spectroscopic properties

Abstract

Two new organometallic–inorganic charge transfer salts formulated as [(η 5-Cp)Fe(η 6-MeO-p-C 6H 4–NHNH 2)] 2[Mo 6O 19], 1, and [(η 5-Cp)Fe(η 6-MeO-p-C 6H 4–NHNH 2)] 4[β-Mo 8O 26], 2, were prepared through a metathesis reaction between the organometallic hydrazine precursor [(η 5-Cp)Fe(η 6-MeO-p-C 6H 4–NHNH 2)] +PF 6 − and either [ n-Bu 4N] 2[Mo 6O 19] or [ n-Bu 4N] 4[α-Mo 8O 26] in acetonitrile. In the second case, the [α-Mo 8O 26] 4− anion transforms into the [β-Mo 8O 26] 4− isomer. These organometallic–inorganic hybrids were characterized by spectroscopic techniques (IR, 1H NMR and UV–vis). In addition, the UV–vis diffuse reflectance spectra of 1 and 2 in solid state exhibit a band at λ max = 475 and 470 nm, respectively, not observed in DMSO solution, which have been attributed to a charge transfer transition. On the other hand, the solid state structure of 2, solved by X-ray diffraction analysis shows the formation of hydrogen bonds between the protons of the –NHNH 2 and C–H groups with the terminal oxo groups of the β-octamolybdate anions [β-Mo 8O 26] 4−. Finally, hybrid 3, formulated as [(η 5-Cp)Fe(η 6-C 6H 5OMe)] 4[β-Mo 8O 26] was prepared in EtOH under solvothermal conditions. The single crystal X-ray structure shows the elimination of the –NHNH 2 group from the organometallic mixed sandwich reducing its associative ability toward the oxo groups of the counterion only to the electrostatic interactions and to the very weak CH⋯O hydrogen bonds.