Ferrocene‐Fused Acenequinones: Synthesis, Structure and Reaction Chemistry

Abstract

The synthesis of anti‐[1.1](2,17)(6,13)ferrocenophane‐1,12‐dione (2) is discussed. By addition of LiAlH4, NaBH4 or Wittig's reagent only one keto group reacted to give HO‐ or cC3H4‐functionalized [1.1](2,17)(6,13)ferrocenophan‐12‐hydroxy‐1‐one (3) and [1.1](2,17)(6,13)ferrocenophan‐12‐cyclopropane‐1‐one (4). Exchange of CO by CS groups is possible upon addition of Lawesson's reagent to 2 forming [1.1](2,17)(6,13)ferrocenophan‐1,12‐dithioketone (5). Theoretical studies confirm the different reactivities of the CO groups. Electrochemical studies on 2–5 showed separated reversible one‐electron events for 2–4 (125–925 mV) and an irreversible one for 5. The ferrocenyls in 4 are easier to oxidize, due to their higher electron‐richness. In 2 a larger redox separation comes about suggesting a stronger intermetallic interaction between FeII/FeIII in the mixed‐valent species. In situ UV‐vis/NIR studies confirm that 2 is a weak coupled class II system according to the classification of Robin and Day. Compounds 3 and 4 display electrostatic interactions among the ferrocenyls as oxidation progresses.

Experimental and Theoretical Evaluation of Four NLO‐Active Divalent Transition‐Metal Complexes Supported by an Enantiomerically Pure Tetradentate Schiff Base Ligand

“…In 2 , the nitro group is twisted by 15.8(6)° with the salicylidene ring plane. All those metrical parameters are in accordance with previously reported structural data for related tetradentate ferrocenoyl enaminone ligands and their unsymmetrical Schiff base derivatives [19,35a,41,42,47] …”

“…The protonated Schiff base proligand 2 exists as its enaminone tautomeric form in solution (Figure 1). The 1 H NMR spectrum displays a deshielded amino proton doublet at δ =10.86 ppm, this deshielding is due to intramolecular hydrogen bonding between the N−H group and the carbonyl oxygen atom [25a,35a,41] . Note also that the most downfield shifted broad singlet appearing at δ =14.40 ppm is due to the hydroxyl proton engaged in a second intramolecular hydrogen bond with the imine nitrogen atom (Scheme 1).…”

Spectroscopy, molecular structure, and electropolymerization of Ni(ii) and Cu(ii) complexes containing a thiophene-appending fluorinated Schiff base ligand

“…The molecular structure of 2 shows that it adopts a characteristic double Z – s – Z conformational form, 45,54–56 confirming the NMR findings (see above) and consistent with two keto-enamine tautomers with two intramolecular N–H⋯O hydrogen bonds formed between the amino hydrogen atoms and the carbonyl oxygen atoms with N⋯O bond separations of 2.734(3) and 2.712(3) Å (Table S3, ESI‡). Such hydrogen bonding interactions close two pseudo-six membered rings through the resonant [OC–CC–NH⋯] fragment, 57 with alternating double-, single-, double- and single bonds between the vicinal sp 2 -hybridized atoms (Table S1, ESI‡).…”

“…All the metrical parameters are in accordance with literature structural data reported for enaminone derivatives by ourselves, 45,59,60 and others. 55,56,61,62…”

“…All the metrical parameters are in accordance with literature structural data reported for enaminone derivatives by ourselves, 45,59,60 and others. 55,56,61,62 Complexes 3, 4, and 5•CH 2 Cl 2 . The X-ray crystal structures of the three complexes 3-5•CH 2 Cl 2 show that the metal(II) ion is tetracoordinated, bonded to the four N 2 O 2 donor atoms set of the tetradentate dianionic Schiff base ligand (Fig.…”