John S. Maass

Expanding molecular transition metal cubane clusters of the form [M4(μ3-O)4]12+: syntheses, spectroscopic and structural characterizations of molecules M4(μ3-O)4(O2P(Bn)2)4(O4), M = VV and WV

Oxidizing the trimer V(3)(μ(3)-O)(O(2))(μ(2)-O(2)P(Bn)(2))(6)(H(2)O) in the presence of excess (t)BuOOH results in V(4)(μ(3)-O)(4)(μ(2)-O(2)P(Bn)(2))(4)(O(4)) and heating W(CO)(6) and bis(benzyl)phosphinic acid in 1:1 EtOH/THF at 120 °C produces W(4)(μ(3)-O)(4)(μ(2)-O(2)P(Bn)(2))(4)(O(4)).

Syntheses, X-ray structural characterizations, and thermal stabilities of two nonclassical trinuclear vanadium(IV) complexes, (V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6(H2O) and (V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6(py), and polymeric complexes of stoichiometry (VO(O2PR2)2)∞, R2 = Ph2 and o-(CH2)2(C6H4).

The preparation and structural characterization of two trinuclear vanadium complexes, (V(3)(μ(3)-O)O(2))(μ(2)-O(2)P(CH(2)C(6)H(5))(2))(6)(H(2)O), 1, and (V(3)(μ(3)-O)O(2))(μ(2)-O(2)P(CH(2)C(6)H(5))(2))(6)(py), 2, are reported. In these nonclassical structures, the planar central core consists of the three vanadium atoms arranged in the form of an acute quasi-isosceles triangle with the central oxygen atom multiply bonded to the vanadium atom at the center of the vertex angle and weakly interacting with the two other vanadium atoms on the base sites, each of which contain one external multiply bonded oxygen atom. Reacting VO(acac)(2)in the presence of diphenylphosphinic acid affords (VO(O(2)PPh(2))(2))(∞), 3, while 2-hydroxyisophosphindoline-2-oxide at room temperature in CH(2)Cl(2) affords ((H(2)O)VO(O(2)Po-(CH(2))(2)C(6)H(4))(2))(∞), 4, and at 120 °C in EtOH yields (VO(O(2)P(o-(CH(2))(2)(C(6)H(4)))(∞), 5 on the basis of elemental analyses. The thermal and chemical stability of the complexes were assessed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The bond strengths of the vanadium atoms to the OH(2) ligand in 1 and to the NC(5)H(5) ligand in 2 were assessed at 10.7 and 42.0 kJ/mol respectively. Room temperature magnetic susceptibility measurements reveal magnetic moments for trinuclear 1 and 2 at 3.02(1) and 3.05(1) μ(B/mol), and also close to spin only values (1.73 μ(B)) values for 3, 4, and 5 at 1.77(2), 1.758(7), and 1.77(3) μ(B), respectively. Variable-temperature, solid-state magnetic susceptibility measurements were conducted on complex 2 in the temperature range of 2.0-298 K and at an applied field of 0.5 T. Magnetization measurements at 2 and 4 K confirmed a very weak magnetic interaction between the vanadyl centers.

tert-Butyl 2-(4-chloro-benzo-yl)-2-methyl-propanoate.

The title compound, C15H19ClO3, is bent with a dihedral angle of 72.02 (9)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C—O—C). In the crystal, molecules related by inversion symmetry are connected by weak C—H⋯O interactions into infinite chains. These interactions involve H atoms from a methyl group of the dimethyl residue and the O atoms of the ketone on one side of a molecule; on the other side there are interactions between H atoms of the benzene ring and the carbonyl O atoms of the ester functionality. There are no directional interactions between the chains.

Syntheses and characterization of the vanadium trimer (V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6(4,4′-bipyridine) and the vanadium hexamer [(V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6]2(μ2-N1,N2-di(pyridin-4-yl)oxalamide)

Abstract Reacting VO(acac)2 with six equivalents of dibenzylphosphinic acid in the presence of 4,4′-bipyridine or μ2-N1,N2-di(pyridin-4-yl)oxalamide leads to trimeric (V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6(4,4′-bipyridine) or the hexamer [(V3(μ3-O)O2)(μ2-O2P(CH2C6H5)2)6]2(μ2-N1,N2-di(pyridin-4-yl)oxalamide). The complexes were characterized by spectroscopic (FTIR and 1H NMR spectroscopies), TGA, and by single crystal X-ray diffraction measurements. The structures consist of a planar central core where three vanadium ions are arranged in the form of a quasi-isosceles triangle and contain an interstitial O which is multiply bonded to one V and weakly interacting at different bond distances to the remaining two V ions.

The first dinuclear cobalt complex bridged by acetylamidate ligands: di-μ-acetylamido-κ2O:N;κ2N:O-di-μ-hydroxido-κ4O:O-bis[bis(pyridine-κN)cobalt(III)] bis(perchlorate) acetonitrile disolvate.

The title compound, [Co(2)(C(2)H(4)NO)(2)(OH)(2)(C(5)H(5)N)(4)](ClO(4))(2)·2C(2)H(3)N, consists of two octahedral Co(III) centers arranged around an inversion point in which two cis hydroxide and two trans acetylamidate ligands link the two centers together, forming a dimeric cationic complex. Each Co(III) center has two cis pyridine ligands which coordinate in the same plane as the cis hydroxide ligands. Two acetonitrile solvent molecules and two perchlorate anions are hydrogen bonded to the H atoms on the bridging hydroxide and acetylamidate (N atom) ligands, respectively.