Supramolecular assemblies of trinuclear triangular copper(II) secondary building units through hydrogen bonds. Generation of different metal-organic frameworks, valuable catalysts for peroxidative oxidation of alkanes

Formation of the trinuclear triangular copper derivative [Cu3(μ3-OH)(μ-pz)3(EtCOO)2(H2O)]·H2O, 1b (Hpz = pyrazole), has been simply achieved by addition of Hpz to a water solution of Cu(EtCOO)2·H2O and leaving the resulting solution to crystallize at ca. 12 °C. When the reaction and crystallization were carried out at a slightly higher temperature (18−22 °C), the compound [Cu3(μ3-OH)(μ-pz)3(EtCOO)2(H2O)], 1c, formed. Single-crystal X-ray molecular structure determinations show that both compounds have analogous trinuclear triangular structures, but very different supramolecular assemblies, due mainly, but not only, to the crystallization molecule of H2O in 1b. In particular, contrarily to the previously reported, strictly related, [Cu3(μ3-OH)(μ-pz)3(EtCOO)2(EtOH)], 1a, the propionate ions in 1b and 1c do not bridge different triangular units, whereas they are involved in intra- and intermolecular H-bonds, generating complex supramolecular 2-D MOFs. Compounds 1a and 1c act as remarkably active and selective catalysts or catalyst precursors for liquid biphasic (MeCN/H2O) peroxidative oxidation of cyclohexane and cyclopentane to the corresponding alcohols and ketones

Trinuclear Triangular Copper(II) Clusters – Synthesis, Electrochemical Studies and Catalytic Peroxidative Oxidation of Cycloalkanes

The reactions of CuII carboxylates (valerate, 2-methylbutyrate, hexanoate, heptanoate) with pyrazole (Hpz) in EtOH or EtOH/water solutions easily afford the triangular trinuclear copper derivatives [Cu 3(μ3-OH)(μ-pz)3(RCOO)2(L) x] [R = CH3(CH2)3, L = H 2O, x = 1 for 5; R = CH3CH2CH(CH3), L = EtOH, x = 2 for 6; R = CH3(CH2)4, L = EtOH, x = 1 for 7; R = CH3(CH2)5, L = EtOH, x = 1 for 8] as it has been previously found for R = H, L = Hpz, x = 2, (1); R = CH3, L = Hpz, x = 1, (2); R = CH3CH2, L = EtOH, x = 1, (3) and [Cu3(μ3-OH)(μ-pz) 3-(CH3(CH2)2COO)2(MeOH) (H2O)], (4). The trinuclear structure common to 5-8 has been assigned on the basis of magnetic susceptibility studies, ESI MS, IR and UV/Vis spectroscopy as well as 1H NMR measurements. The room temp. magnetic susceptibilities of 5-8 almost correspond to the presence of a single unpaired electron for each trinuclear unit. The IR spectra exhibit signals due to the bridging μ3-OH in accordance with what was observed in the spectra of 1-4. Solid-state and MeOH solution UV/Vis spectra show the same features previously reported for 1-4 and 1H NMR spectra of 1-8 show almost identical low field signals that can be assigned to pz- hydrogens. A detailed investigation of the supramolecular structures of 1 and 4 and the single-crystal X-ray study of the polymeric paddlewheel Cu(2-methylbutyrate) 2, A, are also reported. Electrochemical experiments show that in 1-8 the CuII ions can be reduced, in distinct steps, to CuI and Cu0. All the complexes act as catalysts or catalyst precursors for the efficient peroxidative oxidation, by aqueous hydrogen peroxide in acetonitrile and at room temp., of cycloalkanes RH (cyclohexane and cyclopentane) to the corresponding cyclic alcohols and ketones, with overall yields of up to 34% and TONs up to 42. Radical pathways involving the formation of alkyl hydroperoxides (ROOH) are involved

Topologically Unique 2D Heterometallic Cu^II/Mg Coordination Polymer: Synthesis, Structural Features, and Catalytic Use in Alkane Hydrocarboxylation

The new two-dimensional (2D) heterometallic Cu^II/Mg coordination polymer [Cu₂Mg₂(μ-Htea)₂(μ₆-pma)­(H₂O)₆]_<i>n</i>·6<i>n</i>H₂O (<b>1</b>) with an unprecedented [Cu₂Mg­(μ-O)₂(μ-COO)₂]⁻ core has been easily generated by aqueous medium self-assembly from copper­(II) nitrate, triethanolamine (H₃tea), magnesium hydroxide, and pyromellitic acid (H₄pma). The crystal structure of <b>1</b> is composed of infinite interdigitated 2D metal–organic layers that extend via H-bonds into an intricate 3D supramolecular framework. The topological analysis of <b>1</b> discloses a binodal 2,4-connected underlying 2D net with the unique topology described by the point symbol of (6⁴·8·10)­(6), further simplification of which leads to an uninodal 4-connected net with the <b>sql</b> topology. Apart from representing a very rare example of the heterometallic Cu/Mg coordination network, compound <b>1</b> also acts as an efficient catalyst precursor for the mild single-pot hydrocarboxylation of linear and cyclic C_<i>n</i> (<i>n</i> = 5–9) alkanes into the corresponding C_<i>n</i>+1 carboxylic acids

Structural transformations of Pb(II)- trans -1,2-bis(4′-pyridyl) ethene coordination polymers in solution

10.1021/cg201071yCrystal Growth and Design11104697-470