673457-04-0Relevant articles and documents
2-Pyridinealdoxime [(py)CHNOH] in manganese(II) carboxylate chemistry: Mononuclear, dinuclear, tetranuclear and polymeric complexes, and partial transformation of (py)CHNOH to picolinate(-1)
Milios, Constantinos J.,Kefalloniti, Elena,Raptopoulou, Catherine P.,Terzis, Aris,Escuer, Albert,Vicente, Ramon,Perlepes, Spyros P.
, p. 83 - 95 (2004)
The preparation and crystal structures of four MnII carboxylate complexes containing 2-pyridinealdoxime, (py)CHNOH, are reported. The 1:1 reaction between Mn(O2CPh)2·2H2O and (py)CHNOH in MeCN, followed by evaporation of the resulting solution, redissolution of the residue in CHCl3 and precipitation with Et 2O leads to isolation of [Mn4(O2CPh) 6{(py)CO2}2{(py)CHNOH}2]·0. 6CHCl3 (1·0.6CHCl3). The most interesting synthetic feature is the in situ formation of the picolinate(-1) ligand, (py)CO2-. The centrosymmetric tetranuclear cluster consists of an exactly planar zig-zag array of MnII ions and is held together by four syn,syn η1:η2:μ2 and two η1:η2:μ3 PhCO 2- groups, two η1:η2: μ2 (py)CO2- ligands and two N,N′-bidentate chelating (py)CHNOH molecules. The 1:4:7 [Mn 3II,III, IIIO(O2CPh)6(pyr) 2(H2O)]/Me3SiCl/(py)CHNOH reaction mixture in MeCN (pyr=pyridine) yields the 1D coordination polymer [Mn(O2CPh) {(py)CO2}{(py)CHNOH}]n (2), in which the partial (py)CHNOH→(py)CO2- transformation has again occurred. In each chain the MnII ions are bridged by syn,anti carboxylate groups of the η1:η1:η1:μ 2 (py)CO2- ligands, while the monodentate PhCO2- group and the N,N′-bidentate chelating (py)CHNOH molecule complete the octahedral coordination at each metal ion. The 1:3 reaction between Mn(O2CMe)2·4H2O and (py)CHNOH in EtOH leads to the isolation of the dinuclear complex [Mn 2(O2CMe)2{(py)CO2} 2{(py)CHNOH}2] (3); crystallography reveals again the partial (py)CHNOH→(py)CO2- transformation. The dinuclear molecule is located at a centre of symmetry; the MnII ions are bridged by two oxygen atoms from the two symmetry-related η 1:η1:μ2 (py)CO2- ligands, whose nitrogen atoms are ligated to different metal ions. Each Mn II ion is further coordinated by a monodentate MeCO2 - group and a N,N′-bidentate chelating (py)CHNOH molecule. Reaction of Mn(hfac)2·3H2O (hfacH= hexafluoroacetylacetone) with 1 equivalent of (py)CHNOH in CH2Cl 2 yields complex [Mn(O2CCF3) 2{(py)CHNOH}2] (4); the CF3CO2 - ligand is one of the decomposition products of the hfac - ligand. The MnII ion in 4 is coordinated by two monodentate CF3CO2- groups and two N,N′-bidentate chelating (py)CHNOH ligands in a cis-cis-trans fashion. The four complexes have been characterised by IR spectroscopy; characteristic bands are discussed in terms of the known structures and the coordination modes of the ligands. Variable-temperature magnetic susceptibility and EPR studies indicate weak antiferromagnetic exchange interactions in 1.
