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The main advances in the synthesis and studies of the properties of new stable heterocyclic verdazyl radicals and verdazyl radical coordination chemistry are reviewed. The promising applications of these radicals are also discussed. [ABSTRACT FROM AUTHOR]

The problem of stabilization of polyhedral carbon clusters, which do not obey the isolated pentagon rule, is discussed taking a dodecahedral fullerene C20 as an example. Ab initio MO LCAO calculations in the HF/3-21G approximation showed that fullerene C20 as well as its C20H5 hydrides with C5v symmetry can form stable 2η5-π-complexes of the CpFeC20FeCp and H5C20FeC20H5 types. The energies of the η5-Fe--C20 π-bonds in these complexes were compared with those of the Fe--Cp bond in ferrocene and the Fe--C60 bond in the η5-π-C60H5FeCp complex. [ABSTRACT FROM AUTHOR]

Reactions of the binuclear complexes MLCl [M = Pt or Pd, L = bis(diphenylphosphino)methane (dppm) or 2-(diphenylphosphino)pyridine (dppy)] with thallium 3,6-di tert-butyl- o-benzosemiquinone (3,6-SQ) in solutions have been studied. The formation of the corresponding bis(semiquinone) binuclear derivatives ML(SQ) with retention of the metal-metal bond has been established by the ESR method. The average distances between the centers of localization of unpaired electrons, which were determined from the ESR spectral data for the complexes studied, allow conclusions about the parallel arrangement of the semiquinone ligands in skewed conformations in a square-pyramidal coordination sphere of both metal atoms. At room temperature, the biradical complexes are slowly converted to diamagnetic catecholate compounds with cleavage of the M-M bond and with retention of the bridging structure of the dppm and dppy ligands. The structures of catecholate complexes of palladium have been established by X-ray structural analysis. [ABSTRACT FROM AUTHOR]