ianion, the structure of which contains two four-coordinated boron atoms, to very weak M . . . H interactions with the hydride atoms in the case of bulky [3,3 1 -Co(1,2-C 2 B 9 H 11 ) 2 ]´monoanion.
We report a new family of photoactive molecular compounds for which reversible solid state transformations and linkage isomerism have been observed using in situ X-ray diffraction. The interaction of trisIJtriphenylphosphine)silverIJI) with eicosaborate ijB 20 H 18 ] 2− afforded a binuclear complex with a bridging boron cluster that underwent a series of isomerization transformations occurring in a single-crystal-to-single-crystal manner without crystal degradation and obeying the criteria for an effective molecular switch.
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Interaction of [Cu2B10H10] with 2,2'-bipyridine (bipy) afforded a novel binuclear discrete complex of the [Cu2(bipy)2B10H10] composition. Two copper(I) atoms coordinate a bridge boron cage through an apical edge and a triangular BBB face situated at its opposite apical vertices to form four 3c2e (CuHB) and one 2c2e Cu-B bonds. The charge density model was obtained by density functional theory calculations of isolated molecule and crystal. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM) and electron localizability indicator (ELI-D). The geometry and the topological parameters of copper(I) coordination environment were found to be sensitive to crystal-field effect. An annulus of flat electron density ρ(r) and small ∇(2)ρ(r) is formed at dianion faces. As a result, some of the expected B-B, Cu-B, or Cu-H bond critical points are absent. The topological instability in the region of multicentered bonds is observed. The Cu-B bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism for copper(I) decaborates. The results show that an unambiguous real-space criterion for multicentered bonding between transition metals and polyhedral boron anions is not yet given. The molecular graph for this class of compounds does not provide a definitive picture of the chemical boding and can be complemented with other descriptors, such as virial graphs and the ELI-D distribution.
Boron-cross-linked cobalt(II) pseudoclathrochelate was obtained by the template reaction of 2-acetylpyrazoloxime, phenylboronic acid, and a new DMF cobalt(II) solvato complex with a decachloro-closo-decaborate dianion. As confirmed by singlecrystal X-ray diffraction, this complex crystallizes with two symmetry-independent cobalt(II) pseudoclathrochelate cations, one decachloro-closo-decaborate dianion, one benzene, one dichloromethane solvent molecule, and two molecules of DMF. The latter act as pseudocapping fragments to the monocapped trispyrazoloximate ligands by forming N−H•••O hydrogen bonds with their pyrazole groups. The Co II N 6 -coordination polyhedra adopt a nearly ideal TP geometry with distortion angles φ equal to 1.22(16) and 2.58(17)°for two symmetry-independent pseudoclathrochelate cations, both containing the encapsulated cobalt(II) ion in its high-spin state (Co−N 2.115(4)−2.198(3) Å). Magnetic properties of this complex were studied both by dc-magnetometry and by solution-state NMR spectroscopy to reveal a high magnetic anisotropy, thus suggesting a large magnetic susceptibility tensor anisotropy (25.8 × 10 −32 m 3 at 298 K) and a large negative zero-field splitting energy (−85 cm −1 ). The results of magnetometry studies in the ac magnetic field suggest a single molecule magnet behavior of this TP complex with an effective magnetization reversal barrier of approximately 130 cm −1 . Its pseudocapping DMF molecules that form H-bonds with tris-pyrazoloximate fragments are easy to substitute by strong H-bond acceptors, such as chloride ions and di-and tetramethylureas, thus affecting the magnetic properties of a whole pseudomacrobicyclic paramagnetic system.
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