T. V. Potapova

Apically linked iron(II) α-dioximate and α-oximehydrazonate bis-clathrochelates: synthesis, structure and electrocatalytic properties.

Iron(II) α-oximehydrazonate and α-dioximate bis-clathrochelates with apical hydrocarbon linkers were obtained by template condensation on an iron(II) ion followed by H(+)-catalyzed macrobicyclization of the bis-semiclathrochelate precursor with formaldehyde and triethyl orthoformate, and by transmetallation of the triethylantimony-containing clathrochelate precursor with diboron-containing bifunctional Lewis acids, respectively. The geometry of the para-phenylenediboron-capped iron(II) bis-clathrochelate studied by single-crystal X-ray diffraction is intermediate between a trigonal prism and a trigonal antiprism with a distortion angle of 20.4°; the rigidity of its C6H4 linker results in the presence of the expected three-fold pseudo-rotational B···Fe···B···B···Fe···B axis and a staggered conformation of the cyclohexane-containing chelate moieties. The cyclic voltammograms (CVs) for the oximehydrazonate bis-clathrochelates contain single one-electron (for each metallocentre, and therefore, two electrons per molecule) quasi-reversible reduction waves assigned to the redox-processes of Fe(2+/+), and no interaction is observed between the two encapsulated iron(I)-containing metallocenters; six strong electron-withdrawing ethoxy substituents in the 1,3,5-triazacyclohexane capping fragments substantially affect the potential of this reduction. The corresponding waves for the dioximate complexes are irreversible: due to the structural rigidity of the caging tris-dioximate ligands, their reduced dianionic forms are unstable on the CV time scale. The CV for the hexaethoxy bis-clathrochelate complex contains one two-electron reversible oxidation wave assigned to the metal-centered oxidation of Fe(2+/3+), whereas those for its dioximate analogs are quasi-reversible. The relative lability of the ligand cavity in binuclear oximehydrazonates causes a stabilization of both the oxidized and the reduced forms; the reduced iron(I)-containing species are highly electrocatalytically active in the hydrogen-producing 2H(+)/H2 reaction. Their higher activity as compared with that for dioximate bis-clathrochelates was explained by the higher availability of the catalytically active metallocentres for H(+) ions.

Design of bicyclic and cage boron compounds based on allylboration of acetylenes with allyldichloroboranes.

Allylboration of acetylenes with allyldichloroboranes has been proposed as a first step of allylboron-acetylene condensation and a way to design condensation products from stage to stage. The chemistry has been applied to the synthesis of isomeric 3-borabicyclo[3.3.1]non-6-enes transformed into 3-methyl-1-boraadamantane and [5-D]-3-methyl-1-boraadamantane derivatives.

1-Boraadamantane derivatives with functional groups in the side chain

Abstract 1-Boraadamantane derivatives containing ω-functionalized substituents in the position 2 have been synthesized by hydroboration-isomerization of 7-(ω-X-alkyl)-3-borabicyclo[3.3.1]non-6-enes. The application of the method permitted the previously unreported preparation of intra-complexes of the 1-boraadamantane series (X, XI, XIII).

Chelate-assisted synthesis of pyrazolylidene derivatives from cyanoacetic acid hydrazide and O-methyl lactims

Diphenylboron chelate of cyanoacetic acid hydrazide and O-methyl lactims were used to synthesize pyrrolidin-, piperidin-, and azepan-2-ylidene derivatives of 3-aminopyrazol-5-one.

Low-temperature phase transition in plastic solid 1-boraadamantane

ConclusionsRaman spectroscopy showed that solid 1-boraadamantane at room temperature is a plastic meso phase with isotropic molecular reorientation, which converts at 183 K to an ordered crystalline state. This effect indicates the possibility of determining the molecular structure of 1-boraadamantane by x-ray diffraction analysis below 183 K.

Behavior of 1-boraadamantane complexes during chemical ionization

ConclusionsIntra- and intermolecular complexes of 1-boraadamantane during mild protolysis eliminate a hydride ion to form [M - H]+ ions. During severe protolysis (methane reactant gas) protonation of the 1-boraadamantane structure occurs with cleavage of a B-C bond.

1,3-Elimination in γ-halogen- and γ-ammonium-1-boraadamantane ate-complexes

Conclusions1.Complexes of 2-(2-halogenoidethyl)-1-boraadamantanes with tetrahydrofuran and pyridine have been synthesized by the hydroboration-isomerization of 3-methoxy-7-(3-halogenoidpropyl)-3-borabicyclo[3.3.1]non-6-enes.2.4-Chloro-, and 2-(2-halogenoidethyl)-, and 2-(2-trimethylammoniumethyl)-1-boraadamantane ate-complexes undergo self-induced 1,3-elimination, resulting in the formation of substituted 3-borabicyclo[3.3.1]nonanes containing a cyclopropane fragment.