Synthesis and electronic structure of permethylindenyl complexes of iron and cobalt

Electrochemistry and UV/visible spectroscopy of phosphino-substituted bis(η5-indenyl)iron(II) complexes

“…Only one redox process was observed in each of the rac/meso mixtures. Like the other diindenyl ferrocenes that have been reported [17][18][19][20][21], the redox process is reversible. This is in stark contrast to that of dppf in CH 2 Cl 2 , however, for which irreversible processes are observed [8].…”

“…However, solvent effects and transitions involving the SHOMO and SLUMO (and potentially other MOs), as well as changes in relative orbital energies and electron configurations, can significantly complicate the situation to the extent that one can generally only get meaningful information by comparing closely related compounds [25,26]. Although group 4 half-sandwich complexes have been investigated by cyclic voltammetry and UV/visible spectroscopy [26][27][28][29], the processes and orbitals involved are quite different from those observed in diindenyl ferrocene systems: Firstly, oxidation of the group 4 complexes occurs from ligand-based orbitals rather than metal-based d orbitals [26,29,30], and, secondly, although the UV/visible spectroscopy provides information on the HOMO-LUMO gap in both systems, it is an LMCT process from the indenyl to a d 0 metal centre in the group 4 complexes [26,27,29] rather than a d-d transition of the d 6 Fe atom [19,31]. One must be careful, therefore, when making comparisons between these systems.…”

“…Diindenyl ferrocenes typically exhibit two UV/visible absorption bands (with extinction coefficients of between 300 and 900 L.mol -1 .cm -1 ), one near 420 nm and the other near 555 nm [17,18,20]. These bands are likely to be d-d transitions since the HOMO is largely metal-based [19,31] and the extinction coefficients are less than 1,000 L.mol -1 .cm -1 . It has been observed that for methyl substitution the UV/visible spectra vary by only 12 nm (416-426 nm and 548-560 nm) [17,20].…”

“…This paper reports on those studies. Additionally, in comparison to the analogous dicyclopentadienyliron(II) complexes, diindenyliron(II) complexes have barely been investigated [17][18][19][20][21]. We have recently reported systematic studies of the electrochemistry and UV/visible spectroscopy of a variety of methyl-and TMS-substituted diindenyl ferrocenes: the methyl-substituted complexes were found to be well behaved with (i) an additive relationship between the number of methyl groups and their ring position on the oxidation potential of the ferrocene and (ii) only minor effects on the UV/visible spectra [17].…”

Synthesis of heptamethylindenyl rhodium(III) complexes: molecular structures of [(η5-C9Me7)RhCl(µ-Cl)]2 and [(η5-C9Me7)Rh(PMe2Ph)Cl2]

“…We recently reported detailed preparative procedures for the synthesis of heptamethylindene, Ind*H, on both the 10 g (9) and 90 g (8) scales. Ind*H is reported to have a pK, of 27.4 in DMSO compared with values of 20.1 for indene, 26.1 for Cp*H, and 18.0 for cyclopentadiene (1 1).…”