Structure–molecular orbital energy correlations in Me3Si-substituted bis(indenyl)iron complexes evidenced with UV–vis spectroscopy and cyclic voltammetry

Synthesis, structures and spectroelectrochemistry of methyl-substituted bis(η5-indenyl)iron(II) complexes

“…These bands are likely to be d-d transitions since the HOMO is largely metal-based [5,17] and the extinction coefficients are all less than 1000 L mol À1 cm À1 . For mono-trimethylsilyl-substitution on the C 5 ring, we found that the UV/visible absorption peaks change by 10-22 nm while for disubstitution, all of the UV/visible absorption peaks shift to longer wavelength by 40-62 nm [10]. Apparently, the r * orbitals of the TMS groups have a significant influence on the indenide ring MOs, thus affecting the bands in the UV/visible spectra.…”

“…We recently reported [10] the spectroelectrochemistry of a variety of trimethylsilyl-substituted derivatives of bis(indenyl)iron(II) in which significant effects on the UV/visible spectra were observed but only minor, nonadditive effects were found in the cyclic voltammetry. Quite different effects were observed for the methyl derivatives reported here.…”

“…Related systems of particular relevance are the group 4 metallocenes, for which the cyclic voltammetry and UV/visible spectra of many cyclopentadienyl (but not indenyl) derivatives have been reported [7], and the half-sandwich indenyl group 4 complexes which have had some systematic studies carried out [8,9]. We recently reported the spectroelectrochemical properties of trimethylsilyl derivatives of indenyl ferrocenes, but were unable to find consistent trends or rationalize the observations of either the electrochemistry or the UV/visible spectroscopy [10]. We therefore sought to simplify the system by using methyl groups, thus eliminating the complication of p-donor/acceptor effects.…”

From ferrocene to 1,2,3,4,5-pentafluoroferrocene: halogen effect on the properties of metallocene

“…A similar, although smaller trend was noticed upon the introduction of methyl substituents 56 while other functional groups usually led to a bathochromic shift. [61][62][63] To further investigate the electronic structure of polyfluoroferrocenes, the energies of the HOMO and LUMO were calculated. As reported by Long, 43 fluorination mainly stabilizes the HOMO while a weak destabilization of the LUMO was noticed from 1,2,3trifluoferrocene (Table 2).…”

Complexes of manganese, iron and cobalt with sterically demanding indenyl ligands

“…Reaction of two equivalents of NaInd tBu (1-Na) and NaInd cHexyl (2-Na) with one equivalent of MI 2 (thf ) n (M = Mn (n = 3), Fe (n = 2)) and Co(acac) 2 in tetrahydrofuran yielded the corresponding manganocenes, ferrocenes and cobaltocenes as crystalline compounds in moderate yields. ‡ Whereas several substituted bis(indenyl)iron and -cobalt complexes have been synthesized previously, 28,[60][61][62][63][64][65][66][67][68][69][70] very little is known about the corresponding manganocenes with the exception of a recent report by Hanusa and co-workers. 18 It was pointed out that bis(indenyl)manganese complexes suffer from a substantial air-and moisture-sensitivity and that their syntheses require manganese starting materials of high purity otherwise intractable oils are obtained.…”