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1-(Bromomercurio)ferrocene
(2013)
The asymmetric unit of the title compound, [Fe(C5H5)(C5H4BrHg)], contains two independent molecules, A and B, in which the Hg-C bond lengths are 2.045 (6) and 2.046 (6) Å, the Hg-Br bond lengths are 2.4511 (9) and 2.4562 (7) Å, and the C-Hg-Br angles are 176.42 (17) and 177.32 (17)°. The two cyclopentadienyl rings of mol-ecule A are eclipsed, while those of mol-ecule B are almost staggered. The HgBr groups are connected by intermolecular Hg⋯Br contacts of 3.3142 (9)-3.4895 (11) Å, forming layers parallel to (001). These layers contain both four-membered (HgBr)2 and eight-membered (HgBr)4 rings. Ferrocene-ferrocene C-H⋯π contacts connect the molecular layers along the c-axis direction.
The IrIII atom of the title compound, [Ir(C11H8N)2Cl(CH3CN)], displays a distorted octahedral coordination. The pyridyl groups are in trans positions [N—Ir—N = 173.07 (10)°], while the phenyl groups are trans with respect to the acetonitrile and chloride groups [C—Ir—N = 178.13 (11) and C—Ir—Cl = 176.22 (9)°]. The pyridylphenyl groups only show a small deviation from planarity, with the dihedral angle between the planes of the two six-membered rings in each pyridylphenyl group being 5.6 (2) and 5.8 (1)°. The crystal packing shows intermolecular C—H[cdots, three dots, centered]Cl, C—H[cdots, three dots, centered]π(acetonitrile) and C—H[cdots, three dots, centered]π(pyridylphenyl) contacts.
Pyrazolyl-substituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives have been synthesized by reaction of 1,4-benzoquinone and 1,4-naphthoquinone, respectively, with pyrazole. Cyclovoltammetric measurements have shown that 1,4-benzoquinone possesses the potential to oxidize 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene. The 2,5-bis(pyrazol-1-yl)- 1,4-dihydroxybenzene reacts with air to give quantitatively black insoluble 2,5-bis(pyrazol-1-yl)-1,4- quinhydrone. Black crystals of 2,5-bis(pyrazol-1-yl)-1,4-quinhydrone suitable for X-ray diffraction were grown from methanol at ambient temperature (monoclinic C2/c). The poor yields of pyrazolylsubstituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives can be explained by the formation of insoluble black quinhydrons in the reaction of benzoquinone and naphthoquinone with pyrazole. The dianions of 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene react with oxygen to give the corresponding semiquinone anions. 2,5-Bis(pyrazol-1-yl)-1,4-benzoquinone shows two reversible one-electron reduction processes in cyclovoltammetric measurements, whereas pyrazolyl-substituted 1,4-dihdroxybenzene and -naphthene derivatives undergo irreversibile electrontransfer processes.