[1.1]Ferrocenophanes and Bis(ferrocenyl) Species with Aluminum and Gallium as Bridging Elements: Synthesis, Characterization, and Electrochemical Studies

Abstract

Salt-metathesis reactions between dilithioferrocene (Li(2)fc·2/3tmeda) and intramolecularly coordinated aluminum and gallium species RECl(2) [R = 5-Me(3)Si-2-(Me(2)NCH(2))C(6)H(3); E = Al (2a), Ga (2b); and R = (2-C(5)H(4)N)Me(2)SiCH(2); E = Al (3a), Ga (3b)] gave respective [1.1]ferrocenophanes ([1.1]FCPs). Those obtained from 2a and 2b, respectively, were isolated as analytically pure compounds and fully characterized including single-crystal X-ray structure determinations [4a (Al): 43%; 4b (Ga): 47%]. Bis(ferrocenyl) compounds of the type REFc(2) [R = 5-Me(3)Si-2-(Me(2)NCH(2))C(6)H(3); E = Al (5a), Ga (5b); and R = (2-C(5)H(4)N)Me(2)SiCH(2); E = Al (6a), Ga (6b)] and R(2)SiFc(2) [R = Me (7(Me)); Et (7(Et))] were prepared, starting from respective element dichlorides and lithioferrocene (LiFc). Molecular structures of 6a, 7(Me), and 7(Et) were solved by single-crystal X-ray analyses. One of the two Fc moieties of 6a was bent toward the open coordination site of the aluminum atom. The measured dip angles α* of the two independent molecules in the asymmetric unit were 11.9(5) and 13.3(5)°, respectively. The redox behavior of [1.1]FCPs 4 and bis(ferrocenyl) species 5, 6, 7, and (Mamx)EFc(2) [Mamx = 2,4-tBu(2)-6-(Me(2)NCH(2))C(6)H(2); E = Al (8a), Ga (8b)] were investigated with cyclic voltammetry. While all gallium and silicon compounds gave meaningful and interpretable data, all aluminum compounds were problematic with the exception of 8a. Aluminum species, compared to respective gallium species, are more sensitive and, presumably, fluoride ions or residual water from the electrolyte and solvent are causing degradation. The splitting between the formal potentials for bis(ferrocenyl) species was significantly smaller (5b, 6b, and 8b: ΔE°' = 0.138-0.159 V) than that of the [1.1]FCP 4b (ΔE°' = 0.309 V). These results were explained by assuming an electrostatic interaction between the two iron centers; differences between bis(ferrocenyl) species and [1.1]FCPs are likely due to a more effective solvation of Fe-containing moieties in the more flexible bis(ferrocenyl) species.

Indium‐Bridged [1]Ferrocenophanes

“…For example, the 1 H NMR spectrum of 4 2 displays three signals in the characteristic range of Cp protons, with one signal being twice as intense as the other two ( δ =3.91 (4 α‐H), 4.26 (8 β‐H), and 4.40 ppm (4 α‐H)). This pattern is a distinctive signature of heavier Group 13 element bridged [1.1]FCPs stabilized by “one‐armed” phenyl ligands 18a,b,d. 22 The two signals of the β protons, either with a small splitting or overlapping, appear approximately in the middle of the two signals of the α protons, which, in turn, show a large splitting (In(Me 2 Ntsi): δ =4.36 (2 α‐H), 4.43 (2 β‐H), 4.45 (2 β‐H), and 4.57 ppm (2 α‐H);22 InAr′: δ =4.04 (4 α‐H), 4.45 (4 β‐H), 4.53 (4 β‐H), and 4.97 ppm (4 α‐H);18b GaAr′: δ =3.99 (4 α‐H), 4.37 (4 β‐H), 4.48 (4 β‐H), and 5.07 ppm (4 α‐H);18b AlAr′: δ =3.97 (4 α‐H), 4.42 (4 β‐H), 4.52 (4 β‐H), and 5.17 ppm (4 α‐H)) 18a.…”

“…The chemical behaviour of the indium species 5 1 is reminiscent of the strained sandwich compounds (Mamx)Gafc and (Mamx)Alfc 13c. 18d Both [1]FCPs as well as their ruthenium analogues spontaneously polymerize in solution 13c. 18d However, to perform controlled polymerizations, monomers must be isolated and purified.…”

“…18d Both [1]FCPs as well as their ruthenium analogues spontaneously polymerize in solution 13c. 18d However, to perform controlled polymerizations, monomers must be isolated and purified. Against the background that the use of two i Pr groups on the ferrocenediyl moiety resulted in the isolation of the gallane 2 (ER x =GaAr′; Scheme ),11 the salt metathesis of the dilithio derivative of 1 and Ar′InCl 2 was performed with the hope that predominantly the targeted inda[1]ferrocenophane 6 1 forms (Scheme ).…”

Boron, aluminium, gallium, indium and thallium

“…309 3 Gallium Gallium (and aluminium) bridged [1]-ferrocenophanes, [1]-ruthenocenophanes and mixed gallium-silicon and all gallium (or aluminium) bridged [1.1] ferrocenophanes were reported. [310][311][312] When gallium was ligated by the bulky ligand 2,4-ditert-butyl-6-[(dimethylamino)methyl]phenyl formation of the [1]-metallacyclophanes was strongly favoured over the [1.1] derivatives. These [1]-metallacyclophanes underwent facile ring opening polymerisation, with the high reactivity attributed to the ortho-tBu steric bulk increasing the strain in the [1]-metallocenophanes.…”

Synthesis and characterization of ferrocenyl stannanes and polyferrocenyl stannanes

“…Sn) 47-50 or 15 (P, As) 51,52 linking moieties have been described since the late 1960s. Very recently, several new[1.1]ferrocenophanes containing Al, Ga, or Si bridging elements containing intramolecularly coordinating ligands have been synthesised by the Müller group 129. Larger symmetrical macrocyclic[1.1]ferrocenophanes were also reported by Manners et al for species with either five or six alternating linked ferrocenes and dimethylsilyl groups.…”