Iron−Molybdenum Charge-Transfer Hybrids Containing Organometallic and Inorganic Fragments Bridged by Aryldiazenido Ligands in a μ-η6:η1 Coordination Mode: Syntheses, Characterization, X-ray Structures, Electrochemistry, and Theoretical Investigation
Résumé
Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula [(η5-C5H5)Fe(μ,η6:η1-p-RC6H4NN)Mo(η2-S2CNEt2)3] +PF6- (R: H, 5+PF6-; Me, 6+PF6-; MeO, 7+PF6-) and [(η5-C5Me5)Fe(μ,η6:η1-C6H5NN)Mo(η2-S2CNEt2)3]+PF6-, 8+PF6-, have been synthesized by reaction of the corresponding mixed-sandwich organometallic hydrazines [(η5-C5H5)Fe(η6-p-RC6H4NHNH2)]+PF6- (R: H, 1+PF6-; Me, 2+PF6-; MeO, 3+PF6-) and [(η5-C5Me5)Fe(η6-C6H5NHNH2)]+PF6-, 4+PF6-, with cis-dioxomolybdenum(VI) bis(diethyldithiocarbamato) complex, [MoO2(S2CNEt2)2], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC(S)NEt2*3H2O, in refluxing methanol. These iron−molybdenum complexes consist of organometallic and inorganic fragments linked each other through a π-conjugated aryldiazenido bridge coordinated in η6 and η1 modes, respectively. These complexes were fully characterized by FT-IR, UV−visible, and 1H NMR spectroscopies and, in the case of complex 7+PF6-, by single-crystal X-ray diffraction analysis. Likewise, the electrochemical and solvatochromic properties were studied by cyclic voltammetry and UV−visible spectroscopy, respectively. The electronic spectra of these hybrids show an absorption band in the 462−489 and 447−470 nm regions in CH2Cl2 and DMSO, respectively, indicating the existence of a charge-transfer transition from the inorganic donor to the organometallic acceptor fragments through the aryldiazenido spacer. A rationalization of the properties of 5+PF6-−8+PF6- is provided through DFT calculations on a simplified model of 7+PF6-. Besides the heterodinuclear complexes 5+PF6-−8+PF6-, the mononuclear molybdenum diazenido derivatives, [(η1-p-RC6H4NN)Mo(η2-S2CNEt2)3] (R: H, 9; Me, 10; MeO, 11), resulting from the decoordination of the [(η5-C5H5)Fe]+ moiety of complexes 5+PF6-−7+PF6-, were also isolated. For comparative studies, the crystalline and molecular structure of complex 10*Et2O was also determined by X-ray diffraction analysis and its electronic structure computed.