Synthesis, Characterization, and Electrochemical Studies on [1.1]Ferrocenophanes Containing Aluminum, Gallium, and Indium

Abstract

The synthesis, characterization, structure, and electrochemistry of [1.1]ferrocenophanes, bridged by the heavier group 13 elements aluminum (1a), gallium (1b), and indium (1c), are described and discussed. Compounds 1a-c have been synthesized from dilithioferrocene and intramolecularly coordinated group 13 element dihalides Ar'EX(2) (Ar' = 2-(Me(2)NCH(2))C(6)H(4); EX(2) = AlCl(2), GaCl(2), InI(2)). Although the synthesis and characterization of 1a by single-crystal X-ray analysis has been described recently (Braunschweig, H.; Burschka, C.; Clentsmith, G. K. B.; Kupfer, T.; Radacki, K. Inorg. Chem. 2005, 44, 4906), compounds 1b and 1c are described for the first time. The galla (1b) and the inda (1c) [1.1]ferrocenophane have been characterized by single-crystal X-ray determination [1b: C(38)H(40)Fe(2)Ga(2)N(2), monoclinic, P2(1)/c, a = 10.3467(5) Angstroms, b = 11.6311(4) Angstroms, c = 14.0747(7) Angstroms, beta = 105.931(2) degrees, Z = 2; 1c: C(38)H(40)Fe(2)In(2)N(2), monoclinic, P2(1)/c, a = 10.5522(7) Angstroms, b = 11.8476(8) Angstroms, c = 13.9855(9) Angstroms, beta = 104.990(3) degrees, Z = 2]. All three compounds 1a-c are anti conformers with trans orientations of the two donating NMe(2) groups. For the [1.1]ferrocenophane 1a, an unprecedented fully reversible two-electron redox process was observed by cyclic voltammetry, whereas the corresponding Ga and In species exhibit a more conventional stepwise redox chemistry. According to the Robin-Day classification, 1a is a class I and 1b and 1c are class II species. In addition to the reversible processes, compound 1a shows an irreversible oxidation at higher voltages accompanied by adsorption processes. The irreversible adsorption process was investigated with an electrochemical quartz crystal microbalance (EQCM).

Examination of the Mixed‐Valence State of the Doubly Boron‐Bridged Diferrocene Cation [(FeCp)2{μ‐C10H6(BPh)2}]+

“…[26][27][28] Boron-bridged oligo-and polyferrocenes are particularly intriguing owing to the opportunity to switch between tri-and tetracoordinate boron through the binding of nucleophiles, which in turn influences the degree of electronic communication between the ferrocene moieties. [28][29][30] An early example of a MV boron-bridged oligoferrocene is the zwitterionic borate Fc II 3 Fc III B (Fc= ferrocenyl), which features a tetra-coordinate boron bridge. Although an intervalence charge-transfer (IVCT) band was detected in the NIR region, a localized structure was identified in the solid state by X-ray diffraction.…”

Ferrocenyl(dimethyl)aluminum dimer [(η5-C5H5)Fe(η5-C5H4)AlMe2]2

“…Surprisingly little information is available on ferrocenylaluminum compounds. Recently, it has been shown that the reactions of 1,1 0 -dilithiated ferrocene fcLi 2 with organoaluminum dihalides afford ferrocenophanes with aluminum in the bridge, stabilised by intramolecular coordination [5,6], 1,1 0 -disubstituted ferrocene [7] or rather novel types of ferrocenylaluminum compounds [6b,8]. Ferrocenylmercury chloride reacts with trialkylalanes to give mixed dimers 2 [9].…”

Photoinduced FeCp Bond Cleavage and Insertion Reactions of Strained Silicon‐ and Sulphur‐Bridged [1]Ferrocenophanes in the Presence of Transition‐Metal Carbonyls

“…[20] Since the X-ray crystal structure of the first [1.1]ferrocenophane was reported by Watts et al in 1967, [52] such species have attracted significant attention, owing to their unusual structural and redox properties. [53] Analogous [1.1]ferrocenophanes bearing ER x bridging groups, in which E ranges from Group 13 (B, [54] Al, Ga, In [55] ), Group 14 (C [56] Si, [53,57] Sn [19] ) to Group 15 (P [58,59] ), have also been published and their properties extensively studied. Nonetheless, to the best of our knowledge, compound 10 is the first example of a Group- 16- [54,59] It has been previously noted that, in general, the greater the ring-strain in [1]ferrocenophanes, the more upfield shifted the ipso-Cp-C 13 C resonance.…”