Complexation and metallation of Ph2PCC(CH2)5CCPh2 in triosmium carbonyl clusters

Reaction of Ph₂PCC(CH₂)₅CCPh₂ with Os₃(CO)₁₀(NCMe)₂ affords Os₃(CO)₁₀(μ,η²-(Ph₂P)₂C₉H₁₀) (1) and the double cluster [Os₃(CO)₁₀]₂(μ,η²- (Ph₂P)₂C₉H₁₀)₂ (2), through coordination of the phosphine groups. Thermolysis of 1 in toluene generates Os₃(CO)₇(μ-PPh₂)(μ₃,η⁵-Ph₂PC₉H₁₀) (3) and Os₃(CO)₈(μ-PPh₂)(μ₃,η⁶-Ph₂P(C₉H₁₀)CO) (4). The molecular structures of 1, 3, and 4 have been determined by an X-ray diffraction study. Both 3 and 4 contain a bridging phosphido group and a carbocycle connected to an osmacyclopentadienyl ring, which are apparently derived from C-P bond activation and C-C bond rearrangement of the dpndy ligand governed by the triosmium clusters.     

Polarization effects in mesogenic isoxazoles and 1,3,4-oxadiazoles

Four new series of unsymmetric isoxazoles and 1,3,4-oxadiazoles were prepared, characterized and their mesomorphic properties investigated. Isoxazoles were obtained by condensation–cyclization of β-diketones with hydroxylamine hydrochloride in refluxing THF, while 1,3,4-oxadiazoles were obtained from hydrazine-carboxylate in refluxing POCl₃. Two single crystallographic structures were determined by X-ray crystallographic analysis. A correlated dimeric structure was formed by H-bonds in isoxazoles 1a (n=6), leading to a more elongated structure required for the formation of mesophases. All compounds 1a–c formed N, SmA or/and SmC phases. In contrast, compounds 1d exhibited columnar phases, and an N_cell=14.6 obtained from powder XRD data indicated that a correlated structure formed by four molecules was probably induced in Col_h phases. The better mesomorphic behavior formed in 1a than 1b might be attributed to stronger intermolecular interactions and higher polarization induced in isoxazoles 1a.     

Synthesis,structures and magnetic properties of two hexanuclear complexes

The reaction of salicylaldoxime (H₂salox) with Mn(ClO₄)₂ · 6H₂O, NaN(CN)₂ and NEt₃ in MeOH affords a Mn^III₆ hexanuclear complex of [Mn₆O₂(salox)₆(MeOH)₆(NCNCONH₂)₂] (1), while reaction of H₂salox with MnCl₂ · 4H₂O and NEt₄OH in EtOH affords a Mn^III₆ hexanuclear complex of [Mn₆O₂(salox)₆(EtOH)₄(H₂O)₂Cl₂] (2). Both complexes 1 and 2 contain a [Mn^III₆(μ₃-O)₂]¹⁴⁺ core, which is a known structural type in the family of Mn₆ complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S = 4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0 K and 10–70 kG confirm that the ground state is S = 4, with significant magnetoanisotropy as gauged by the D value of ?0.82 cm^?1 and ?1.18 cm^?1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a U_eff of 27.0(1) K and τ₀ = 3.8(2) × 10^?9 s for complex 1, and U_eff of 25.1(6) K and τ₀ = 4.6(1) × 10^?8 s for complex 2.     

Hydrogen-bond-assisted supramolecular 1-D tape-like structures of mesogenic bis-pyrazoles

Two new series of isomeric bis-pyrazoles 1a–b are prepared, characterized, and their mesomorphic properties investigated. These pyrazoyl derivatives were obtained from the condensation of α,β-diketones 2a–b with hydrazine monohydrate in refluxing THF. Two single crystallographic structures of compounds mesogenic 1a (n=14) and nonmesogenic 1b (n=8) were determined by X-ray analysis. Both 1a–14 and 1b–8 crystallize in a triclinic space group P?1 and monoclinic C2/c group, respectively. An extended H-bonded structure was formed in both crystal lattices, giving a pseudo 1D-polymeric tape-like structure. Derivatives 1a exhibited smectic A/C mesophases, in contrast, derivatives 1b were all nonmesogenic. The difference in mesomorphic behavior was attributed to the between linear conformation and the coplanarity of the five rings over than in 1a. The correlation between the molecular structures and the mesomorphic properties is discussed.     

Further studies of [Ni4(DAniDANy)4] (DAniDANy2− = N,N’-bis-p-anisyl-2,7-diamido-1,8-naphthyridine) and its one-electron oxidation product: Metal-metal sigma bonding in Ni49+ complex

The linear tetranickel strings, [Ni₄(DAniDANy)₄] (1), and its one-electron oxidation product, [Ni₄(DAniDANy)₄](PF₆) (2), have been synthesized and studied extensively (DAniDANy^2? = N,N’-bis-p-anisyl-2,7-diamido-1,8-naphthyridine). Crystal structural analyses and DFT calculations suggest that the chemical oxidation of 1 involves removal of an electron from the σ* antibonding orbital, which results in the formation of Ni-Ni bonds in 2.     

An unprecedented oxidative migration of a methyl group from 2-(2',6'-dimethylphenylazo)-4-methylphenol mediated by ruthenium and osmium

An unprecedented chemical transformation of 2-(2',6'-dimethylphenylazo)-4-methylphenol has been observed upon its reaction with [M(PPh(3))(3)X(2)] (M = Ru, Os; X = Cl, Br) whereby one methyl group from the phenyl ring of the arylazo fragment migrates to the metal center via oxidation to CO.     

Ferromagnetic exchange in two dicopper(II) complexes using a mu-alkoxo-mu-7-azaindolate bridge

Syntheses, structures, and magnetic properties of two heterobridged mu-alkoxo-mu-7-azaindolate dicopper(II) complexes, [Cu(II)2(L-F)(mu-C7H5N2)] (1) and [Cu(II)2(L-H)(mu-C7H5N2)].CH3OH (2) (H3L-F = 1,3-bis(3-fluorosalicylideneamino)-2-propanol; H3L-H = 1,3-bis(salicylideneamino)-2-propanol) have been reported. Aside from being a new type of heterobridged complex, 1 and 2 exhibit ferromagnetic interaction (2J = 52 cm(-1) for 1 and 33.4 cm(-1) for 2) despite orbital complementarity (7-azaindolate HOMO is antisymmetric).