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

Abstract

Six phosphino-functionalized diindenyl ferrocenes have been characterized by UV/visible spectroscopy and cyclic voltammetry in dichloromethane. The complexes contain the following ligands: 1-diphenylphosphino-(1), 1-diphenylphosphino-2-methyl-(2), 1-diphenylphosphino-3-methyl-(3), 1-diphenylphosphino-3-trimethylsilyl-(4), 1-diphenylphosphino-2,3-dimethyl-(5), and 1-diphenylphosphino-4,7-dimethyl-indenide (6). The cyclic voltammetry shows an approximately additive relationship between oxidation potential and the type of substituent and its ring position, but with increasing substitution leading to lower than otherwise expected oxidation potentials. The UV/visible spectra show two absorptions with the low energy band moving to lower energy with increasing substitution on the C 5 ring.

Synthesis, X-ray structure and electrochemical oxidation of palladium(ii) complexes of ferrocenyldiphenylphosphine

“…15 The reversible potentials and the level of chemical reversibility of the oxidation of 1,1¢bis(diphenylphosphino)octamethylferrocene (dppomf) and 1,1¢bis(diphenylphosphinoindenyl)iron, Fe(dppind) 2 , are significantly different from those of dppf. 16,17 Dppf complexes of palladium have found application in organometallic chemistry and the homogeneous catalysis of, for example, C-C coupling and CO insertion reactions. [18][19][20] While working with palladacyclic complexes containing ferrocenyldiphenylphosphine (PPh 2 Fc), we realised that, although the chemical behaviour of this ligand has been reported to be less complex than that of dppf, 6,21, 22 it has not been studied as thoroughly, nor has the influence of P-coordination on its electrochemical behaviour been established.…”

Derivatives of 1,1′-bis(diphenylphosphino)ferrocene (dppf): Electrochemistry, complexation and the X-ray structures of 1,1′-bis(diphenylphosphino)osmocene (dppo) and [PdCl2(dppo)]

“…Oxidation of [PdCl 2 ((dppind) 2 Fe)] occurs at 0.25 V vs. FcH 0/+ while oxidation of the platinum analogue occurs at 0.24 V vs. FcH 0/+ . The difference between the potential at which oxidation of the free (dppind) 2 Fe occurs (À0.14 V) [14] and that of these complexes is approximately 0.35 V, which is identical to the difference between dppf and [MCl 2 (dppf)] (M = Pd or Pt) [6]. This similarity suggests that an equation similar to Eq.…”

“…While it is unclear why such a reaction does not seem to occur, it is possible that the lone pair on arsenic is tied up in p-bonding to the C 5 ring to a greater extent than the lone pair on phosphorus, and therefore, formation of an arsenic radical cation is less likely. The oxidative electrochemistry of (dppind) 2 Fe was recently reported and, unlike dppf, the oxidation of (dppind) 2 Fe is reversible [14]. The compounds, [MCl 2 ((dppind) 2 Fe)] (M = Pd or Pt), were prepared by methods similar to the dppf analogues [7].…”

“…A final sequence of alternatives results from changing the groups on the C 5 rings. For example, the oxidative electrochemistries of 1,1 0 -bis(diphenylphosphino)octamethylferrocene (dppomf) [13] and 1,1 0 -bis(diphenylphosphinoindenyl)iron (dppind) 2 Fe [14] have been examined, and the potentials at which oxidation of these compounds occur as well as the reversibility of the oxidation are significantly different from dppf.…”

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.…”