Defective double-cubane, tetranuclear manganese(II) and cobalt(II) complexes with simultaneous mu(1,1)-Azido and mu-O bridges

The reactions of M(O2CCH(3))(2). 4H(2)O (M= Mn, Co) with di-2-pyridyl ketone, (py)(2)CO, and NaN3 in CH3OH or CH3OH/ H2O allow isolation of the tetranuclear compounds [Mn-4(mu (1.1)-N-3)(2)(N-3)(2)(py)(2)C(OH)O(2)(py)(2)C(OCH3)O(2)] (1) and [Co-4(mu (1.1)-N-3)(2)(N-3)(2)(py)(2)C(OH)O(2)(py)(2)C(OCH3)O(2)]. 2H(2)O (2). X-ray diffraction analysis reveals defective double-cubane tetrameric entities in which the Mn-II or Co-II atoms are linked by mu (1.1)-N-3 bridges and two kinds of O-bridges. The molar magnetic susceptibility measurements of 1 and 2 in the 2-300 K range indicate weak antiferromagnetic coupling for 1 and clear bulk ferromagnetic coupling for 2

A one-dimensional Manganese(II) coordination polymer derived from zerovalent manganese and 1-hydroxybenzotriazole - Synthesis, characterization, crystal structure and magnetic properties

The reaction of zerovalent manganese with 1-hydroxybenzotriazole, btaOH, and NH4SCN in DMF in the presence of dioxygen allows isolation of the one-dimensional coordination polymer [Mn-3(btaO)(2)(NCS)(4)(DMF)(8)], (3). X-ray diffraction analysis reveals that the chain is best described as [Mn-2(btaO)(2)(NCS)(2)(DMF)(6)] dimers linked by Mn(NCS)(2)- (DMF)2 bridges. Molar magnetic susceptibility measurements of 3 in the 5-300 K range indicate weak antiferromagnetic coupling between the Mn-II atoms within the dinuclear subunits of the chain

Cu-II-herbicide complexes: structure and bioactivity

Copper complexes with the commercial auxin herbicides 2,4-dichlorophenoxy-acetic acid (2,4-D), 3,4-dichlorophenoxy-acetic acid (3,4-D), 2,4,5-trichlorophenoxy-acetic acid (2,4,5-T), 2-methyl-4-chloro-phenoxy-acetic acid (MCPA), 2,3-dichlorophenoxy-acetic acid (2,3-D) and 2-(2,4-dichlorophenoxy)-propanoic acid (2,4-DP) in the presence or not of 2,2′-bipyridine (bipy), an antimicrobial agent, were prepared and characterized. The available evidence supports a dimeric structure for the 2,3-D complex, while the presence of bipy leads to monomeric forms. The solution behaviour of dinuclear complexes in dimethylformamide (DMF) has shown that the complexes are converted to monomeric compounds by the addition of more than 1:2 of bipy. The cyclic voltammograms of dimers in DMF suggest that the complexes retain the dimeric structure in solution. The electron spin resonance spectra of the compound (aqua) (2.2′-bipyridine)bis(2-methyl-4-chloro-phenoxyacetato) copper(II) (1) show features characteristic of the presence of an S = 1 triplet state. The crystal structure of 1 was determined and refined by least-squares methods using three-dimensional Mo Kα data. 1 crystallizes in the space group C2/c, in a cell of dimensions a = 40.49(1), b = 7.286(3). c = 19.617(6) Å, β = 103.23(1)°, V = 5634(3) Å3, Z = 8. Study of the antimicrobial activity showed that the presence of bipy increases the efficiency 4-8 times. © 1998 Elsevier Science S.A. All rights reserved

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)

Studies of monothiomalonamide and its palladium(II) and platinum(II) complexes

A project related to the crystal engineering of hydrogen bonded coordination complexes has been initiated and our first results are presented here. The cis and trans forms of monothiomalonamide (LH2) have been fully characterized by vibrational spectroscopy, thermal techniques and single-crystal X-ray diffraction. The cis form crystallizes in the monoclinic space group P2(1)/c and the trans form in the monoclinic space group C2/c. The respective lattice constants are a = 5.602(3), b = 9.055(2), c = 10.945(5) Angstrom, beta = 101.29(2)degrees (cis-LH2) and a = 20.336(7), b = 4.317(1), c = 12.432(5) Angstrom, beta = 92.16(1)degrees (trans-LH2). The new complexes [Pd(LH2)(4)]X-2 (X = Cl, Br), [Pt(LH2)(4)]X-2 (X = Br, 1), [PdX2(LH2)(2)] (X = Cl, Br, 1) and [PtX2(LH2)(2)] (X = Cl, I) were prepared and characterized by elemental analyses and spectroscopic (IR, far-IR, Raman) studies. All data are discussed in terms of the nature of bonding in conjunction with assigned structures. The LH2 molecule behaves as a monodentate ligand binding through the sulfur atom. Monomeric square planar structures are assigned for the metal complexes in the solid state; the 1:2 complexes have the trans geometry. A detailed comparison of the new complexes with the corresponding monothiooxamide complexes is also presented

Site preferences in hetero-metallic [Fe9−xNix] clusters: a combined crystallographic, spectroscopic and theoretical analysis

The reaction of mixtures of Fe(O2CMe)2·2H2O and Ni(O2CMe)2·4H2O of various compositions with di-2-pyridyl ketone (py2CO, dpk) in MeCN under an inert atmosphere afforded a family of hetero-metallic enneanuclear clusters with general formula [Fe9−xNix(μ4-OH)2(O2CMe)8(py2CO2)4] (2, x = 1.00; 3: x = 6.02; 4, x = 7.46; 5, x = 7.81). Clusters 2–5 are isomorphous to the homo-metallic [Fe9] cluster (1) previously reported by some of us, and also isostructural to the known homo-metallic [Ni9] cluster. All four clusters contain a central MII ion in an unusual 8-coordinate site and eight peripheral MII ions in distorted octahedral environments. The distribution of FeII and NiII ions over these two distinct coordination sites in 2–5 can be established through a combination of X-ray fluorescence and Mössbauer spectroscopies, which show that FeII preferentially occupies the unique 8-coordinate metal site while NiII accumulates in the octahedral holes. Density functional theory indicates that the distribution of ions across the two sites arises not from any intrinsic preference of the FeII ions for the 8-coordinate sites, but rather because of the large ligand field stabilization energy available to NiII in octahedral coordination.</p