2,5-Diferrocenyl-1-phenyl-1H-phosphole (3) has successfully been prepared by a cyclization reaction of phenylphosphine with 1,4-diferrocenylbutadiyne. Subsequent reaction with elemental sulfur and selenium, respectively, leads to the formation of the appropriate phosphole sulfide (4) or selenide (5). Molecules 4 and 5 have structurally been characterized by single crystal X-ray diffraction. Despite the tetrahedral environment at the phosphorus atom, the c C 4 P ring itself is planar and coplanar to the cyclopentadienyl rings of the ferrocenyl termini. Electrochemical measurements revealed that the two ferrocenyl groups could be oxidized at discrete potentials, with separation of the individual redox waves of 280 mV (3), 240 mV (4) and 235 mV (5), respectively. These values agree with other examples of heterocyclic-bridged diferrocenyl compounds such as diferrocenyl thiophene (260 mV) and diferrocenyl furan (290 mV). Compounds [3] + , [4] + and [5] + exhibit IVCT absorptions of weak to moderate strength which conforms well to the predictions of the Hush two-state model for weakly coupled mixedvalence systems. These conclusions are supported by DFT and TD-DFT results, which satisfactorily model the observed structural and spectroscopic parameters. The computational work assists in assigning the various low energy (LF, IVCT) electronic transitions and also highlights the key role of the unsaturated cis-diene-like C 4 H 2 building block of the heterocycle in promoting the Fc à Fc + electron-transfer transition.

Reactions of various substituted bis(imino)acenaphthenes (R‐BIANs) with FeCl2(thf)1.5 afforded the tetrahedral complexes (R‐BIAN)FeCl2 (2) from bulky α‐diimines and the octahedral complexes [Fe(R‐BIAN)3][FeCl4]2 (3) from less bulky ligands. The driving force for the formation of complexes 3 is the high ligand‐field stabilization of the low‐spin FeII center. The two sets of complexes exhibit distinct charge‐transfer band intensities and redox activities. (R‐BIAN)FeCl2 complexes showed reversible ligand‐centered reductions at −0.9 V (vs. FcH/FcH+; FcH: ferrocene); further reduction led to decomposition. Irreversible oxidations were observed at 0.2 and 0.4 V, associated with a reduction at −0.4 V, as well as a ligand‐centered redox event at 1.0 V. First applications of the Fe(BIAN) complexes to hydrogenations of alkenes indicated good catalytic activity under mild conditions.

A range of ferrocenyl aryl ethers of type Fc−O−Ar (Fc = Fe(η 5 -C 5 H 5 )(η 5 -C 5 H n X 4−n ); n = 2−4; X = H, P(O)(OEt) 2 , SO 2 CF 3 ; Ar = 2,4-(NO 2 ) 2 -C 6 H 3 , 4-NO 2 -C 6 H 4 ) have been successfully prepared by using the nucleophilic aromatic substitution reaction (S N Ar) of Fc−OLi (1a−Li) and electron-deficient aryl fluorides, enabling a new pathway to this rarely described family of organometallic compounds. Initial studies of 1a−Li and ophosphonato-substituted hydroxyferrocenes (1b−Li) have also been performed, indicating a low nucleophilicity of the oxygen atom. The S N Ar reaction protocol tolerates ortho substituents, e.g. phosphonato and sulfonyl groups, resulting in 1,2-X,O (X = S, P) ferrocenyl ethers that can be obtained in a onepot synthesis procedure including 1,3-O → C anionic phospho-and thia-Fries rearrangements. Within these studies, the first 1,3-diortho-functionalized ferrocenyl aryl ether could be synthesized. An electrochemical study of the redox potentials of the obtained compounds allows conclusions on the reactivity of the varying electronic properties and the electrophilicity of different aryl fluorides and the nucleophilicity of the functionalized hydroxyl ferrocenes, which is directly reflected by the potential of the first ferrocene related redox processes. Chiral-pool-based phosphonates rearrange to the aryl ethers with diastereomeric excesses of 74 and 81% after the anionic Fries rearrangement. The usage of aryl 1,2-/1,3-difluorides resulted in the synthesis of the first examples of bis(FcO)-substituted benzenes. Their electrochemical investigations reveal a splitting of the two redox processes of the ferrocenyls that decreases from 155 mV (1,2-substitution) to 130 mV (1,3-substitution) on the basis of electrostatic interactions.

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The influence of the coordination and ion pairing properties of electrolyte anions and used solvents on the electrochemical and spectroscopic properties of cationic class II mixed valent species is discussed.