Inorganic Chemistry, Vol.46, No.4, 1123-1134, 2007
Iron-molybdenum charge-transfer hybrids containing organometallic and inorganic fragments bridged by aryldiazenido ligands in a mu-eta(6):eta(1) coordination mode: Syntheses, characterization, X-ray structures, electrochemistry, and theoretical investigation
Representative members of a new family of covalently bonded charge-transfer molecular hybrids, of general formula [(eta(5)-C5H5)Fe(mu,eta(6):eta(1)-p-RC6H4NN)Mo(eta(2)-S2CNEt2)(3)] +PF6- (R: H, 5(+)PF(6)(-); Me, 6(+)PF(6)(-); MeO, 7(+)PF(6)(-)) and [(eta(5)-C5Me5)Fe(mu,eta(6):eta(1)-C6H5NN)Mo(eta(2)-S2CNEt2)(3)]+PF6-, 8(+)PF(6)(-), have been synthesized by reaction of the corresponding mixed-sandwich organometallic hydrazines [(eta(5)-C5H5)Fe(eta(6)-p-RC6H4NHNH2)]+PF6- (R: H, 1(+)PF(6)(-); Me, 2(+)PF(6)(-); MeO, 3(+)PF(6)(-)) and [(eta(5)-C5Me5)Fe(eta(6)-C6H5NHNH2)]+PF6-, 4(+)PF(6)(-), with cis-dioxomolybdenum(VI) bis(diethyldithiocarbamato) complex, [MoO2(S2CNEt2)(2)], in the presence of sodium diethyldithiocarbamato trihydrate, NaSC(S)NEt2 center dot 3H(2)O, in refluxing methanol. These iron-molybdenum complexes consist of organometallic and inorganic fragments linked each other through a pi-conjugated aryldiazenido bridge coordinated in eta(6) and eta(1) modes, respectively. These complexes were fully characterized by FT-IR, UV-visible, and H-1 NMR spectroscopies and, in the case of complex 7(+)PF(6)(-), 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(+)PF(6)(-)-8(+)PF(6)(-) is provided through DFT calculations on a simplified model of 7(+)PF(6)(-). Besides the heterodinuclear complexes 5(+)PF(6)(-)-8(+)PF(6)(-), the mononuclear molybdenum diazenido derivatives, [(eta(1)-p-RC6H4NN)Mo(eta(2)-S2CNEt2)(3)] (R: H, 9; Me, 10; MeO, 11), resulting from the decoordination of the [(eta(5)-C5H5)Fe](+) moiety of complexes 5(+)PF(6)(-)-7(+)PF(6)(-), were also isolated. For comparative studies, the crystalline and molecular structure of complex 10 center dot Et2O was also determined by X-ray diffraction analysis and its electronic structure computed.