Synthesis of bis(diethyldithiocarbamato)manganese(II) and tris(diethyldithiocarbamato)manganese(III)

An ideal undergraduate introduction to the challenges of synthesis and characterization of air-sensitive compounds is accomplished in the preparation of bis(diethyldithiocarbamato)manganese(II). This economical experiment employs a glovebag, low-cost and low-toxicity chemicals, and is completed in one undergraduate laboratory period. For comparison purposes, the synthesis and characterization of air-stable tris(diethyldithiocarbamato)manganese(III) is also described.     

Nitrates and bis(dithiooxalato)nickelates(II) of biacetyldihydrazone complexes

Summary Biacetyldihydrazone (BdH) complexes [M(BdH)₃](NO₃)₂ (M=Co^II, Ni^II, Cu^II or Zn^II); [Fe(BdH)₃](NO₃)₃; [M(BdH)₃][Ni(dto)₂] (M=Co^II, Ni^II or Zn^II; dto=dithiooxalate); [Cu(BdH)₂][Ni(dto)₂] and [Fe(BdH)₃]₂[Ni(dto)₂]₃ have been prepared and characterized by chemical analysis, conductance measurements, electronic and i.r. spectral studies and cyclic voltammetry.A mononuclear octahedral configuration is proposed for all cationic complexes, excepting [Cu(BdH)₂][Ni(dto)₂, which is probably a dithiooxalate bridged dimer.     

Structural, magnetic and catalytic properties of a self-recognized mu-oxo-bridged diiron(III) bis(benzimidazole) complex

The inherent nonplanarity and C(2) symmetry of the dimethyl-substituted bis(benzimidazole) ligand (Me(2)BBZ) results in two distinct atropisomers that, when separated, have been suggested to have potential for chiral recognition and catalysis. Here is reported the synthesis and characterization of a diiron mu-oxo-bridged bis(benzimidazole) complex, 1, that provides indirect support for this hypothesis. Dimerization of a racemic solution of iron-Me(2)BBZ monomers via the mu-oxo bridge yields (+,+) and (-,-) diastereomers whose complementary association can be attributed to the inherent sidedness of the metal-Me(2)BBZ interaction surface, and to the differences in the torsional angles of the phenyl(benzimidazole) units (34 degrees) and the Schiff base linkages (54 degrees). These results highlight the steric differences between the phenyl(benzimidazole) and Schiff-base portions of the ligand, features that could be important in the chiral recognition of ligands and in differentiating substrate trajectories as required for asymmetric catalysis. For completeness, studies of 1 in the catalytic epoxidation of styrene are also reported.     

Oxovanadium(IV), manganese(II) and manganese(III) carbodithioates exhibiting abnormal magnetic behaviour

Summary New carbodithioate complexes of the oxovanadium(IV), manganese(II) and manganese(III) ions have been prepared and studied by i.r. and electronic spectral and variable temperature magnetic susceptibility (77K to room temperature) measurements. The carbodithioate ligands, 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) and 4-phenylpiperazine-1-carbodithioate (4-PPipzcdt), were derived from heterocyclic secondary amines. The VO(4-MPipzcdt)₂ and VO(4-PPipzcdt)₂ complexes possess C _4v symmetry; Mn(4-PPipzcdt)₂ is tetrahedral and Mn(4-PPipzcdt)₃ is octahedral. All exhibit abnormal room temperature magnetic moments and the variable temperature magnetic moments suggest antiferromagnetism for the oxovanadium(IV) and the manganese(II) complexes and the occurrence of low spin (³ T _1g ) high spin (⁵ E _g ) equilibrium in addition to antiferromagnetic interactions in the manganese(III) complex. The spin-spin exchange parameter (-2J) value for the VO(4-MPipzcdt)₂ complex has been calculated using variable temperature magnetic susceptibility data.     

Investigation of the crystal structures and magnetic features of two bis(dithiolato)nickelate salts with flexible organic cations

Transition Metal Chemistry - Two bis(dithiolato)nickel salts with different flexible ammonium counterions, [Et3MeN][Ni(dmit)2] (1) and [(i-Bu)Et3N][Ni(dmit)2] (2)...     

Efficient macrocyclization using methylene-tethered terminal dienes and bis(manganese(III)-enolate)s

Macrocyclic compounds, which have two fused dihydrofuran rings, were synthesized with complete control by the oxidation of α,α,ω,ω-tetraaryl-α,(ω-1)-alkadienes 1_x with manganese(III)-oligomethylenebis(enolate) complexes directly formed by the reaction of the oligomethylene bis(3-oxobutanoate)s 2_y with manganese(III) acetate in situ. The oxamethylene-tethered macrodiolides 5 and 7 were also produced in good to moderate yields by a similar oxidation. The key intermediate, an electron donor-acceptor-like complex, was proposed for the efficient macrocyclization reaction.     

Structure and catalytic activity of a manganese(III) tetraphenylporpholactone

A manganese(III) complex of tetraphenylporpholactone, Mn(TPPL)Cl, was synthesized and characterized, including by single-crystal X-ray diffraction; the catalytic activity of this complex for olefin epoxidation reactions is compared with that of manganese(III) tetraphenylporphyrin chloride, Mn(TPP)Cl.     

Structure and magnetic properties of homobinuclear gadolinium (III) complex of isonicotinoyl hydrazone

The crystal structure of [Gd₂(μ-L)₃(H₂O)₂]1.5(NO₃)1.5 (OH)5H₂O (where L is union of N, N-Diisonicotinoyl-2-hydroxy-5-methyl-isophthalaldehyde dihydrazone) has been determined by X-ray diffraction method. The complex crystallizes in the monoclinic system, space group P2₁/c with a=1.6654(3), b=1.6904(3), c=2.8039(6) nm, β=91.30(3), final R factor is 6.3%. The structure consists of [Gd₂(μ-L)₃(H₂O)₂]³⁺ cation, one and a half nitrate and 1.5 hydroxyl anions and five water molecules. Within dinuclear cation, Gd(III)—Gd(III) is bridged by oxygen and nitrogen atoms of the three ligands, resulting in Gd? Gd distance of 0.36353(2) nm. Gd(III) exhibits a distorted 1333 stack coordination environment. Magnetic susceptibility measurements in the temperature range 300–4 K revealed the occurrence of weak antiferromagnetic exchange interaction between two Gd(III) ions with a J value of—0.22, and g of 1.93.     

Synthesis,crystal structure and magnetic properties of a dinuclear manganese(III) tetradentate Schiff-base complex

A dinuclear manganese(III) tetradentate Schiff-base complex, [Mn₂(salophen)₂(4,4′-bipy)₃](BPh₄)₂ (1) (salophen = N,N′-o-phenylene-bis(salicylideneaminato)), has been synthesized and structurally characterized. Compound 1 crystallized in the triclinic, P 1 space group, a = 13.431(4), b = 13.791(4), c = 13.886(4) Å, α = 73.599(5)°, β = 80.410(6)°, γ = 71.241(5)°, V = 2328.3(12) ų. Complex 1 contains two Mn(salophen) moieties bridged by 4,4′-bipy to form a dinuclear unit, with two terminal 4,4′-bipy ligands. Variable temperature magnetic susceptibility (2–300 K) shows very weak ferromagnetic interactions between the Mn(III) ions.     

Comparative spectroscopic and electrochemical properties of bis(octakis(dodecylthio)naphthalocyaninato)europium(III) and bis(tetra-tert-butylnaphthalocyaninato)europium(III) complexes

Bis(substituted-2,3-naphthalocyaninato)europium(III) complexes: bis(octakis(dodecylthio)-2,3-naphthalocyaninato)europium(III) (Eu[2,3-Nc(SC12H25)8]2, 1) and bis(tetra-tert-butyl-2,3- naphthalocyaninato)europium(III) (Eu[2,3-Nc(t-Bu)4]2, 2) have been synthesized by cyclic tetramerization of naphthalonitriles with Eu(acac)3.H2O in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These compounds were characterized by UV-visible, magnetic circular dichroism (MCD), near-IR, IR, EPR, and mass spectroscopies. The absorption and MCD spectra of 1 showed splitting of the Q band, with peaks at 700 and 784 nm, red shifted from the Q band of 2 at 763 nm. The absorption and MCD spectral band deconvolution calculations of complex 1 gave two A terms in the Q-band region. The A terms are assigned to 2A2-->2E1 transitions. Cyclic voltammograms of 1 and 2 showed reversible oxidation couples at E1/2 = -0.28 V (for 2) and -0.25 V (for 1) vs ferrocenium/ferrocene (Fc+/Fc). The second oxidation exhibited a complicated behavior for both complexes. The reduction couples for 2 were observed at E1/2 = -0.61, -1.64, -1.97, and -2.42 V, and for 1 they were observed at E1/2 = -0.62, -1.60, -1.86, and -2.27 V vs Fc+/Fc. Spectral changes observed on chemical oxidation and reduction of the complexes are presented, and the behaviors of 1 and 2 are compared.     

Structure and DNA-binding properties of bis(quinolonato)bis(pyridine)zinc(II) complexes

The novel neutral mononuclear zinc complexes with the quinolone antibacterial drugs enrofloxacin and oxolinic acid in the presence of the nitrogen donor heterocyclic ligand pyridine have been synthesized and characterized. The experimental data suggest that the quinolone ligands are on the deprotonated mode acting as bidentate ligands coordinated to the zinc(II) ion through the ketone oxygen and a carboxylato oxygen. The crystal structure of the complex bis(enrofloxacinato)bis(pyridine)zinc(II), 1, has been determined with X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT-DNA) with UV and fluorescence spectroscopies. UV spectroscopic titration studies of the interaction of the complexes with DNA have shown that they can bind to CT-DNA and the DNA binding constants have been calculated. Competitive studies with ethidium bromide (EB) have shown that the complexes exhibit the ability to displace the DNA-bound EB indicating that they can bind to DNA in strong competition with EB for the intercalative binding site.