Di-2-pyridyl ketone oxime [(py)(2)CNOH] in manganese carboxylate chemistry: mononuclear, dinuclear and tetranuclear complexes, and partial transformation of (py)(2)CNOH to the gem-diolate(2-) derivative of di-2-pyridyl ketone leading to the formation of NO3-

The use of di-2-pyridyl ketone oxime, (py)(2)CNOH, in manganese carboxylate chemistry has been investigated. Using a variety of synthetic routes complexes [Mn(O2CPh)(2) (py)(2)CNOH(2)] . 0.25H(2)O(1.0.25H(2)O), Mn-4(O2CPh)(2) (py)(2)CO2(2) (py)(2)CNO(2)Br-2] . MeCN (2 . MeCN), [Mn-4(O2CPh)(2) ( py)(2)CO2(2) ( py)(2)CNO(2)Cl-2] . 2MeCN ( 3 . 2MeCN), [Mn-4(O2CMe)(2) (py)(2)CO2(2) (py)(2)CNO(2)Br-2] . 2MeCN ( 4 . 2MeCN), [Mn-4(O2CMe)(2) ( py)(2)CO2(2) (py)(2)CNO(2)(NO3)(2)] . MeCN . H2O( 5 . MeCN . H2O) and [Mn-2(O2CCF3)(2)( hfac)(2) ( py)(2)CNOH(2)] (6) have been isolated in good yields. Remarkable features of the reactions are the in situ transformation of an amount of ( py) 2CNOH to yield the coordination dianion, (py)(2)CO22- of the gem-diol derivative of di-2-pyridyl ketone in 2-5, the coordination of nitrate ligands in 5 although the starting materials are nitrate-free and the incorporation of CF3CO2- ligands in 6 which was prepared from Mn(hfac)(2) . 3H(2)O( hfac(-) = hexa uoroacetylacetonate). Complexes 2 4 have completely analogous molecular structures. The centrosymmetric tetranuclear molecule contains two Mn-II and two Mn-III six-coordinate ions held together by four mu-oxygen atoms from the two 3.2211 (py)(2)CO22- ligands to give the unprecedented [Mn-II ( mu-OR) Mn-III (mu-OR)(2)Mn-III ( mu-OR) Mn-II](6+) core consisting of a planar zig-zag array of the four metal ions. Peripheral ligation is provided by two 2.111 (py)(2)CNO-, two 2.11 PhCO2- and two terminal Br- ligands. The overall molecular structure of 5 is very similar to that of 2-4 except for the X- being chelating NO3-. A tentative reaction scheme was proposed that explains the observed oxime transformation and nitrate generation. The CF3CO2- ligand is one of the decomposition products of the hfac ligand. The two Mn-II ions are bridged by two neutral ( py) 2CNOH ligands which adopt the 2.0111 coordination mode. A chelating hfac(-) ligand and a terminal CF3CO2- ion complete a distorted octahedral geometry at each metal ion. The CV of complex 3 reveals irreversible reduction and oxidation processes. Variable-temperature magnetic susceptibility studies in the 2 300 K range for the representative tetranuclear clusters 2 and 4 reveal weak antiferromagnetic exchange interactions, leading to non-magnetic S-T = 0 ground states. Best-fit parameters obtained by means of the program CLUMAG and applying the appropriate Hamiltonian are J(Mn(II) ... Mn(III)) = 1.7 (2), 1.5 (4) cm(-1) and J(Mn(III) ... Mn(III)) = 3.0 (2, 4) cm(-1)

A cube in a tetrahedron: Microwave-assisted synthesis of an octametallic Fe-III cluster

The microwave-assisted reaction of Fe(O 2CMe)2 with salicylaldoxime (saoH2) in pyridine produces an octametallic cluster in crystalline form in 2 min. The core describes a cube encapsulated in a tetrahedron, while sao2- exhibits a novel coordination mode

Uranium and manganese assembled in a wheel-shaped nanoscale single-molecule magnet with high spin-reversal barrier

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