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 [Cu3(μ3-OH)(μ-pz)3(RCOO)2(L)x] [R = CH3(CH2)3, L = H2O, 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

By reacting copper(II) acrylate with pyrazole (Hpz), two trinuclear copper derivatives [Cu3(mu3-OH)(mu-pz)3(CH2CHCOO)2(H2O)2(Hpz)], 1, and [Cu3(mu3-OH)(mu-pz)3(CH2CHCOO)2(CH3OH)], 2, are obtained, in water and methanol respectively, while copper(II) methacrylate affords [Cu3(mu3-OH)(mu-pz)3(CH2C(CH3)COO)2], 3, independently from the solvent used. In 1 and 2 two triangular trinuclear units are connected through acrylate bridges forming hexanuclear clusters that, in the case of 2 are further connected through double syn-syn carboxylate bridges, generating a 1-D coordination polymer. In the case of 3 a different 1-D coordination polymer is obtained by alternating syn-syn and syn-anti double carboxylate bridges connecting the trinuclear clusters. In all cases H-bonds contribute both to the stabilization of these arrangements and to the formation of more extended supramolecular networks. Compounds 1-3 are valuable catalysts in the peroxidative oxidation with aqueous H2O2, in MeCN at 25 degrees C, of cycloalkanes (i.e. cyclohexane and cyclopentane) to the corresponding ketones and alcohols (overall yield up to 36%, TON = 36), following a radical mechanism as shown by radical trap experiments, and the effects of various factors are studied. Electrochemical experiments show that the copper(II) centres are reduced to copper(I) and copper(0).

A series of mono-, tri-, hexanuclear compounds, and coordination polymers were obtained from the reaction of [Cu 3 (μ 3 -OH)(μ-pz) 3 (MeCOO) 2 (Hpz)], 1, (Hpz = pyrazole) with H 2 SO 4 , H 3 PO 4 , HClO 4 , HNO 3 , CF 3 COOH, and CF 3 SO 3 H. The trinuclear [Cu 3 (μ 3 -OH)(μ-pz) 3 (SO 4 )(Hpz) 3 ] 3 H 2 O, 2 t , forms a one-dimensional coordination polymer through bridging SO 4 2-. The mononuclear [Cu(H 2 PO 4 ) 2 (Hpz) 4 ], 3 m , is instead the unique (pure) compound isolated in our conditions from the reaction of 1 with H 3 PO 4 , whereas both [Cu(ClO 4 ) 2 (Hpz) 4 ], 4 m , and [{Cu 3 (μ 3 -OH)(μ-pz) 3 (ClO 4 )(Hpz) 3 } 2 (μ 2 -ClO 4 ) 2 ], 4 h , have been isolated from the reaction with aqueous HClO 4 , the latter being a hexanuclear species formed by two trinuclear triangular units connected through two bridging perchlorates. Moreover, the three already reported species [Cu 3 (μ 3 -OH)(μ-pz) 3 (NO 3 )(μ 3 -NO 3 )(Hpz) 2 ], 5 t , [{Cu 3 (μ 3 -OH)-(μ-pz) 3 (NO 3 )(Hpz) 3 } 2 (μ 2 -NO 3 ) 2 ], 5 h , and [Cu(NO 3 ) 2 (Hpz) 4 ], 5 m , are formed in the reaction of 1 with HNO 3 . Three pure fractions, containing crystals of the trinuclear [Cu 3 (μ 3 -OH)(μ-pz) 3 (CF 3 COO) 2 (Hpz) 2 ], 6 t , and two mononuclear adducts, [Cu(CF 3 COO) 2 -(HPz) 4 ], 6 m(a) , and [Cu(CF 3 COO) 2 (Hpz) 2 ], 6 m(b) , have been isolated when 1 was reacted with aqueous CF 3 COOH. Analogously, in the reaction of 1 with CF 3 SO 3 H, three different species were obtained, the mononuclear [Cu(CF 3 SO 3 H) 2 (Hpz) 4 ], 7 m , the trinuclear [Cu 3 (μ 3 -OH)(μ-pz) 3 (CF 3 SO 3 ) 2 (Hpz) 3 ] 3 H 2 O, 7 t , and the hexanuclear [{Cu 3 (μ 3 -OH)(μ-pz) 3 (Hpz) 3 }{Cu 3 (μ 3 -O)(μ-pz) 3 (Hpz) 3 }]-(CF 3 SO 3 ) 3 , 7 h , where the two trinuclear units are strongly bonded through an unequally shared H-bond involving (μ 3 -OH) andAll compounds were fully characterized by single-crystal X-ray diffraction determinations, UV-vis and IR spectra, electrospray ionization mass spectrometry, and magnetic susceptibility measurements.

The trinuclear triangular CuII complex [Cu3(μ3-OH)(μ-pz)3(HCOO)2(Hpz)2] (Hpz = pyrazole) reacts with 4,4′-bipyridine (bpy) yielding a two-dimensional (2D) waved sheets, two three-dimensional (3D) coordination polymers (CPs), as well as a hexanuclear CuII cluster, depending on the reagent ratios and reaction conditions. Single crystal X-ray diffraction (XRD) determinations point out that, while CPs crystal structures are not porous, the hexanuclear CuII clusters are packed in the solid state generating a stable porous 3D supramolecular network, where two kinds of perpendicular, hydrophobic channels (ca. 4.83 × 5.86 Å2 and 4.99 × 4.79 Å2, corresponding to the 24.7% of the total crystal volume) are present. In the “as-synthesized” compound, channels of one kind are empty, while the other ones are occupied by guest bpy molecules which can be removed by soaking the crystals in suitable solvents (benzene, toluene, c-hexane) maintaining intact the crystal skeleton. Moreover, two of the above complexes act as catalysts (or catalyst precursors) in the peroxidative oxidation of cyclohexane.

By reacting 4,4′-bipyridine (bpy) with selected trinuclear triangular Cu II complexes, [Cu 3 MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One-and two-dimensional coordination polymers (CPs), as well as two hexanuclear Cu II clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-singlecrystal transition.