Crystal structure at −35°C of carboxycobaltocenium hexafluorophosphate

Metastable Charged Dimers in Organometallic Species: A Look into Hydrogen Bonding between Metallocene Derivatives

Multiply charged complexes bound by noncovalent interactions have been previously described in the literature, although they were mostly focused on organic and main group inorganic systems. In this work, we show that similar complexes can also be found for organometallic systems containing transition metals and deepen in the reasons behind the existence of these species. We have studied the structures, binding energies, and dissociation profiles in the gas phase of a series of charged hydrogen-bonded dimers of metallocene (Ru, Co, Rh, and Mn) derivatives isoelectronic with the ferrocene dimer. Our results indicate that the carboxylic acid-containing dimers are more strongly bonded and present larger barriers to dissociation than the amide ones and that the cationic complexes tend to be more stable than the anionic ones. Additionally, we describe for the first time the symmetric proton transfer that can occur while in the metastable phase. Finally, we use a density-based energy decomposition analysis to shine light on the nature of the interaction between the dimers.

Organometallic electrodes: modification of electrode surfaces through cathodic reduction of cyclopentadienyldiazonium complexes of cobalt and manganese

Two organometallic complexes having cyclopentadienyldiazonium ligands have been isolated and characterized by spectroscopy, X-ray crystallography, and electrochemistry. Both CoCp(η(5)-C(5)H(4)N(2))(2+) (2(2+)) and Mn(CO)(3)(η(5)-C(5)H(4)N(2))(+) (3(+)) undergo facile cyclopentadienyldiazonium ligand-based one-electron reductions which liberate dinitrogen and result in strong binding of the cyclopentadienyl ligand to a glassy carbon surface, similar to the processes well established for organic aryldiazonium salts. The organometallic-modified electrodes are robust and have a thickness of approximately one monolayer (Γ = (2-4) × 10(-10) mol cm(-2)). Their voltammetric responses are as expected for a cobaltocenium-modified electrode, [CoCp(η(5)-C(5)H(4)-E)](+), where Cp = cyclopentadienyl and E = electrode, and a "cymantrene"-modified electrode Mn(CO)(3)(η(5)-C(5)H(4)-E). The cobaltocenium electrode has two cathodic surface waves. The first (E(1/2) = -1.34 V vs ferrocene) is highly reversible, whereas the second (E(pc) = -2.4 V) is not, consistent with the known behavior of cobaltocenium. The cymantrene-substituted electrode has a partially chemically reversible anodic wave at E(1/2) = 0.96 V, also consistent with the behavior of its Mn(CO)(3)Cp parent. Many of the properties of aryl-modified electrodes, such as "blockage" of the voltammetric responses of test analytes, are also seen for the organometallic-modified electrodes. Surface-based substitution of a carbonyl group by a phosphite ligand, P(OR)(3), R = Ph or Me, was observed when the cymantrene-modified electrode was anodically oxidized in the presence of a phosphite ligand. The successful grafting of organometallic moieties by direct bonding of a cyclopentadienyl ligand to electrode surfaces expands the chemical and electrochemical dimensions of diazonium-based modified electrodes.