Uranium(VI) bis(imido) disulfonamide and dihalide complexes: Synthesis density functional theory analysis

Novel cis- and trans-bis(imido) uranium disulfonamide derivatives have been prepared from iodide metathesis reactions between two equivalents of K[N(Me)(SO₂Ar’)] (Ar’ = 4-Me-C₆H₄) and U(N^tBu)₂(I)₂(L)_x (L = OPPh₃, x = 2; Me₂bpy, x = 1; Me₂bpy = 4,4’-dimethyl-2,2’-bipyridyl). These bis(amide) derivatives serve as useful precursors for the synthesis of the trans-diphenolate complex U(N^tBu)₂(O-2-^tBuC₆H₄)₂(OPPh₃)₂ (5), cis- and trans-dithiolate complexes U(N^tBu)₂(SPh)₂(L)_x (L = OPPh₃ (6); Me₂bpy (7)), and cis- and trans-dihalide complexes with the general formulas U(N^tBu)₂(X)₂(L)_x (X = Cl, L = OPPh₃ (8), L = Me₂bpy (10); X = Br, L = OPPh₃ (9), L = Me₂bpy (11)). DFT calculations performed on the trans-dihalide series U(N^tBu)₂(X)₂(L)₂ and the UO₂²⁺ analogues UO₂X₂(OPPh₃)₂ suggest that the uranium centers in the [U(N^tBu)₂]²⁺ ions possess more covalent character than analogous UO₂²⁺ derivatives but that the U-X bonds in the U(N^tBu)₂X₂L₂ complexes possess a more ionic nature.     

Reactions of a hydrido(hydrosilylene)tungsten complex with oxiranes

Reactivity of a hydrido(hydrosilylene)tungsten complex, Cp¹(CO)₂(H)WSi(H)[C(SiMe₃)₃] (1), toward oxiranes was investigated. Treatment of 1 with racemic mono-substituted oxiranes with a substituent R (R = Ph, vinyl, ^tBu, or ⁿBu) at room temperature produced dihydrido(vinyloxysilyl)tungsten complexes, (E)- and/or (Z)-Cp¹(CO)₂(H)₂W{Si(H)(OCHCHR)[C(SiMe₃)₃]} [(E/Z)-2: R = Ph, (E)-3: R = vinyl, (E)-4: R = ^tBu, (E/Z)-5: R = ⁿBu] in high yields via regioselective ring-opening of oxiranes. When the substituent R on oxirane was relatively large, (E)-isomers (2, 3, and 4) were obtained predominantly (87–97%), while the substituent was a relatively small ⁿBu group, an approximately 1:1 mixture of (E)- and (Z)-isomers [(E/Z)-5] was obtained. Reaction of 1 with 2,2-dimethyloxirane afforded the corresponding complex, Cp¹(CO)₂(H)₂W{Si(H)(OCHCMe₂)[C(SiMe₃)₃]} (6), quantitatively. A reaction mechanism is also discussed.     

[MoFe3S4]3+ and [MoFe3S4]2+ cubane clusters containing a pentamethylcyclopentadienyl molybdenum moiety

A series of organometallic molybdenum/iron/sulfur clusters of the general formula [Cp¹MoFe₃S₄L_n]^m (Cp¹ = η⁵-C₅Me₅; L = S^tBu, SPh, Cl, I, n = 3, m = 1−; L_n = I₂(P^tBu₃), m = 0; L = 2,6-diisopropylphenylisocyanide (ArNC), n = 7, m = 1+) have been synthesized. A cubane cluster (PPh₄)[Cp¹MoFe₃S₄(S^tBu)₃] (2) was isolated from a self-assembly reaction of Cp¹Mo(S^tBu)₃ (1), FeCl₃, LiS^tBu, and S₈ followed by cation exchange with PPh₄Br in CH₃CN, while an analogous cluster (PPh₄)[Cp¹MoFe₃S₄(SPh)₃] (3) was obtained from the Cp¹MoCl₄/FeCl₃/LiSPh/PPh₄Br reaction system or from a ligand substitution reaction of 2 with PhSH. Treatment of 2 with benzoyl chloride gave rise to (PPh₄)[Cp¹MoFe₃S₄Cl₃] (4), which was in turn converted to (PPh₄)[Cp¹MoFe₃S₄I₃] (5) by the reaction with NaI. A neutral cubane cluster Cp¹MoFe₃S₄I₂(P^tBu₃) (6) was generated upon treating 5 with P^tBu₃. Although reduction of 4 by cobaltocene under the presence of ArNC resulted in a disproportionation of the cubane core to give Fe₄S₄(ArNC)₉Cl (7), a similar reduction reaction of 5 produced [Cp¹MoFe₃S₄(ArNC)₇]I (8), where the MoFe₃S₄ core was retained. The crystal structures of 4–6, and 8 were determined by the X-ray analysis.     

Synthesis and characterization of organophosphine/phosphite stabilized N-silver(I) succinimide: crystal structure of [(Ph3P)3 · AgNC4H4O2]

Six organophosphine/phosphite stabilized N-silver(I) succinimide complexes of the type L_n · AgNC₄H₄O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) have been prepared by reacting [AgNC₄H₄O₂], which can be synthesized from succinimide and excessive Ag₂O in boiling water, with triphenylphosphine or triethylphosphite in dichloromethane under a nitrogen atmosphere. These complexes were obtained in high yields and characterized by elemental analysis, ¹H, ¹³C{H} NMR, IR spectroscopy and thermal analysis (TG and DSC). The molecular structure of 2c has been determined by X-ray single crystal analysis, in which the silver atom is in a distorted tetrahedral geometry.     

Complexes derived from the copper(II) perchlorate/maleamic acid/2,2′-bipyridine and copper(II) perchlorate/maleic acid/2,2′-bipyridine reaction systems: Synthetic,reactivity, structural and spectroscopic studies

A systematic investigation of the reactions of Cu(ClO₄)₂ · 6H₂O with maleamic acid (H₂L) in the presence of 2,2′-bipyridine (bpy) has been carried out. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixture and the molar ratio of the reactants. Various reaction schemes have led to the isolation of the complexes [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ (1), [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ · 2H₂O (1 · 2H₂O), [Cu(L′′)(bpy)]_n · 2nH₂O (2 · 2nH₂O), [Cu₂(L′′)(bpy)₂(H₂O)₂]_n(ClO₄)_2n · 0.5nH₂O (3 · 0.5nH₂O), [Cu₂(L′′)₂(bpy)₂] · 2MeOH (5 · 2MeOH), [Cu₂(L′)₂(bpy)₂(ClO₄)₂] (6) and [Cu(ClO₄)₂(bpy)(MeCN)₂] (7b), where L′′^2? and L′^? are the maleate(?2) and monomethyl maleate(?1) ligands, respectively. The HL^? ion has been transformed to L′′^2? and L′^? in the known compounds 2 · 2nH₂O and 6, respectively, via metal ion-assisted processes involving hydrolysis (2 · 2nH₂O) and methanolysis (6) of the primary amide group. The reaction that leads to 6 takes place through the formation of the mononuclear complex [Cu(ClO₄)₂(bpy)(MeOH)₂] (7a), whose structure was assigned on the basis of its spectral similarity with the structurally characterized complex 7b. The structures of the cations in 1 and 1 · 2H₂O consists of two Cu^II atoms bridged by the carboxylate groups of the two HL^? ligands, each exhibiting the less common η² coordination mode; a chelating bpy molecule and a H₂O ligand complete square pyramidal coordination at each metal centre. The structure of the dinuclear repeating unit in the 1D coordination polymer 3 · 0.5nH₂O consists of two Cu^II atoms bridged by two syn,syn η¹:η¹:μ₂ carboxylate groups belonging to two L′′^2? ions; each ligand bridged two neighboring [Cu^II,II₂] units thus promoting the formation of a helical chain. The structure of the dinuclear molecule of complex 5 · 2MeOH consists of two Cu^II atoms bridged by two η² carboxylate groups from two L′′^2? ligands; the second carboxylate group of each maleate(?2) ligand is monodentately coordinated to Cu^II, creating a remarkable seven-membered chelating ring. The L′^? ion behaves as a carboxylate-type ligand in 6, with the carboxylate group being in the familiar syn,syn η¹:η¹:μ₂ coordination mode; a chelating bpy molecule and a coordinated ClO₄^? complete five-coordination at each Cu^II centre. The crystal structures of the complexes are stabilized by various H-bonding patterns. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Activation process of 3-alkyl-substituted ansa-bis(indenyl) zirconocenes by MAO

The ansa-indene compound {1-Me₂Si(3-C₉H₆Et)₂} (1) was prepared by alkylation of the unsubstituted ansa-indene. This compound was converted, by reaction with nBuLi, to the dilithium compound [Li₂{1-Me₂Si(3-C₉H₅Et)₂}] (2). ansa-Zirconocene [Zr{1-Me₂Si(3-η⁵-C₉H₅Et)₂}Cl₂] (3) was prepared by the reaction of ZrCl₄ with 2 in ether/toluene at −78 °C. The molecular structure of meso-3 was determined by single crystal X-ray diffraction studies. The ansa-zirconocene 3 exhibits a greater activity in ethylene polymerization than reference complexes such as [Zr{1-Me₂Si(η⁵-C₉H₆)₂}Cl₂] and [Zr{1-C₂H₄(η⁵-C₉H₅)₂}Cl₂] and, in addition, it maintained a reasonable level of activity after 12 h of contact with MAO solution. Furthermore, the different elementary steps in the activation process of ethylene polymerization for substituted complexes [Zr{1-Me₂Si(3-η⁵-C₉H₅R)₂}Cl₂] (R = Et 3, Me 4, nPr 5 and nBu 6) by commercial methylaluminoxane (MAO) have been studied by UV–vis spectroscopy. Addition of MAO in large excess ([Al]/[Zr] = 2000) at −78 °C yields a previously unreported intermediate in the activation process of metallocenes; this intermediate has an absorption band centered at λ = 639 nm. We report here the influence of the type of catalyst, ring substitution, type of cocatalyst and addition of THF on the activation process of these metallocenes.     

A new molecular building blocks: Synthesis,crystal structure,magnetic and spectroscopic properties of Cu(II) and Ni(II) macrocyclic complexes

New higly unsaturated macrocyclic building blocks [CuLSCN]·ClO₄ (1) (L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and [NiL(SCN)₂] (2) (L = N-dl-5,12-dimethyl-7,14-diisopropyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) were synthesized and the crystal structures of both compounds were determined. Both complexes crystallizes in monoclinic, space group P2₁/n (1) and P2₁/c (2). Their magnetic properties were studied over the temperature range 1.8–300 K using a Quantum Design SQUID magnetometer (MPMSXL-5-type). The results indicate that both compounds behave as weakly interacting paramagnetic centers in the crystal lattice. The effects of hydrogen bond mediating the magnetic exchange interactions on the spin density have been evidenced by DFT calculations. The NIR–Vis–UV diffuse-reflectance electronic spectra confirm the square pyramidal and octahedral geometry around Cu²⁺ and Ni²⁺ metal ions.     

Reactivity of intramolecularly coordinated aluminum compounds to R3EOH (E = Sn,Si). Remarkable migration of N,C,N and O,C,O pincer ligands

The reaction of organoaluminum compounds containing O,C,O or N,C,N chelating (so called pincer) ligands [2,6-(YCH₂)₂C₆H₃]AlⁱBu₂ (Y = MeO 1, ^tBuO 2, Me₂N 3) with R₃SnOH (R = Ph or Me) gives tetraorganotin complexes [2,6-(YCH₂)₂C₆H₃]SnR₃ (Y = MeO, R = Ph 4, Y = MeO, R = Me 5; Y = ^tBuO, R = Ph 6, Y = ^tBuO, R = Me 7; Y = Me₂N, R = Ph 8, Y = Me₂N, R = Me 9) as the result of migration of O,C,O or N,C,N pincer ligands from aluminum to tin atom. Reaction of 1 and 2 with (ⁿBu₃Sn)₂O proceeded in similar fashion resulting in 10 and 11 ([2,6-(YCH₂)₂C₆H₃]SnⁿBu₃, Y = MeO 10; Y = ^tBuO 11) in mixture with ⁿBu₃SnⁱBu. The reaction 1 and 3 with 2 equiv. of Ph₃SiOH followed another reaction path and ([2,6-(YCH₂)₂C₆H₃]Al(OSiPh₃)₂, Y = MeO 12, Me₂N 13) were observed as the products of alkane elimination. The organotin derivatives 4–11 were characterized by the help of elemental analysis, ESI-MS technique, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopy and in the case 6 and 8 by single crystal X-ray diffraction (XRD). Compounds 12 and 13 were identified using elemental analysis,¹H, ¹³C, ²⁹Si NMR and IR spectroscopy.     

Insertion of ketenes into lanthanocene n-butylamide and imidazolate complexes

Reaction of Cp₂LnNHⁿBu with 1 equiv. of Ph₂CCO in toluene affords dimeric complexes [Cp₂Ln(OC(CHPh₂)NⁿBu)]₂ [Ln = Yb (1), Dy (2)], derived from a formal insertion of the CC bond of the ketene into the N–H bond. Treatment of CpErCl₂ with 2 equiv. of LiNHⁿBu followed by reacting with Ph₂CCO affords a rearrangement product [Cp₂Er(OC(CHPh₂)NⁿBu)]₂ (3). Treatment of [Cp₂Ln(μ-Im)]₃ (Im = imidazolate) with PhRCCO gives [Cp₂Ln(μ-OC(Im)CPhR)]₂ [R = Et, Ln = Yb (4); R = Ph, Ln = Yb (5), Er (6)]. In contrast to the previous observations that [Cp₂ErNⁱPr₂]₂ and [Cp₂ErNHEt]₂ react with ketenes to give di-insertion products, in the present cases the presence of excess of ketenes has no influence on the final product even with prolonged heating and only monoinsertion products are isolated. All these complexes were characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1 and 3–6 were also determined through X-ray single crystal diffraction analysis.     

New three-dimensional (3,4)-net zincophosphites templated by linear diammonium cations: H3N(CH2)5NH3·Zn3(HPO3)4 and β-H3N(CH2)6NH3·Zn3(HPO3)4

The mild-condition syntheses, single-crystal structures and properties of H₃N(CH₂)₅NH₃·Zn₃(HPO₃)₄ and β-H₃N(CH₂)₆NH₃·Zn₃(HPO₃)₄ are reported. Both are constructed from (3,4)-nets of ZnO₄ tetrahedra and HPO₃ pyramids, sharing vertices to result in three-dimensional anionic open-frameworks. In both materials, the organic species interacts with the framework by way of N–H⋯O bonds. Crystal data: H₃N(CH₂)₅NH₃·Zn₃(HPO₃)₄, M_r = 620.22, orthorhombic, Pccn (No. 56), a = 9.5364 (9) Å, b = 21.8015 (19) Å, c = 9.1118 (7) Å, V = 1894.4 (3) Å³, Z = 4, R(F) = 0.044, wR(F²) = 0.111. β-H₃N(CH₂)₆NH₃·Zn₃(HPO₃)₄, M_r = 634.25, monoclinic, P2₁/n (No. 14), a = 8.7627 (1) Å, b = 13.8117 (2) Å, c = 16.6187 (3) Å, β = 92.680 (1)°, V = 2009.12 (5) Å³, Z = 4, R(F) = 0.072, wR(F²) = 0.187.     

Ruthenium(II) and iron(II) complexes of N-pyridyl substituted imidazolin-2-ylidenes

N-mesityl-N′-pyridyl-imidazolium chloride 1a and the corresponding bromide salt 1b have been deprotonated with NaH in THF giving the free N-heterocyclic carbene N-mesityl-N′-pyridyl-imidazolin-2-ylidene 2 in 80% yield (starting from 1a). Imidazolium salt 1a reacts with RuCl₃ · xH₂O to give a racemic mixture of dinuclear di-μ-chloro bridged ruthenium complexes [(κ²-2)₂Ru(μ-Cl)₂Ru(κ²-2)₂]²⁺ [3a]²⁺. The carbene carbon atoms as well as the halides are arranged in cis-positions to each other whereas the nitrogen atoms adopt a trans-configuration. The di-μ-bromo bridged derivative [(κ²-2)₂Ru(μ-Br)₂Ru(κ²-2)₂]²⁺ [3b]²⁺ was obtained from RuCl₃ · xH₂O and 1b. The bridging halide ligands can be removed by the reaction with silver or sodium salts of bidentate Lewis acids. Complex [3a]²⁺ reacts with silver pyridylcarboxylate to give a racemic mixture of the mononuclear complex [4]⁺. Reaction of [3a]²⁺ with the sodium salt of l-proline resulted in a diastereomeric mixture of complexes [5]⁺. The free N-heterocyclic carbene 2 reacts with [FeCl₂(PPh₃)₂] to give after anion exchange with NaBPh₄ cis/cis/trans coordinated [Fe(κ²-2)₂(MeCN)₂](BPh₄)₂ [6](BPh₄)₂. The molecular structures of [3b](PF₆)₂, [4]PF₆ and [6](BPh₄)₂ · H₂O are reported.     

Synthesis,structures and full characterization of p-tert-butylcalix[5]arene mono-, di-, tri- and pentaanionic ligand precursors

The synthesis, complete characterization, and solid state conformation of a new series of p-tert-butylcalix[5]arene (Bu^tC5) mono-, di-, tri- and pentaanions are reported. X-ray structures of the alkali metal salts illustrate the strong influence of the alkali metal ion on the structure of the calixanion. The strength of the alkali metal base and its reaction stoichiometry play an important role in the conformation and level of deprotonation of the resulting anion. Reaction of Bu^tC5 in a 2:1 molar ratio with alkali metal bases M₂CO₃ (M = Rb, Cs), or in a 1:1 ratio with M₂CO₃ (M = Na, K), MOH (M = Na, K, Rb, Cs) or MH (M = Li, Na) produces Bu^tC5 monoanions, but Bu^tC5 reacts in a 1:1 molar ratio with M₂CO₃ (M = Rb, Cs) or a 1:2 molar ratio with MOC(CH₃)₃ (M = Na, K) to afford Bu^tC5 dianions. Due to the steric bulkiness of the Bu^t group no polymeric structures are observed. Alkali metal salts of trianionic Bu^tC5 were obtained in high yields from reactions of Bu^tC5 with MOC(CH₃)₃ (M = Li, Na, K), BuⁿLi, LiH and LiOH in a 1:3 molar ratio. Pentaanionic Bu^tC5 salts were obtained by the reaction with MOC(CH₃)₃ (M = Li, Na, K) or BuⁿLi in a 5:1 ratio. X-ray crystal structures of Bu^tC5 · Na and Bu^tC5 · Cs indicate that the size of the alkali metal influences the level of cation-π arene interactions and therefore the conformation of the Bu^tC5 unit; for example, Bu^tC5 · Na has a cone conformation while Bu^tC5 · Cs shows a flattened cone conformation. Cation-π arene interactions are observed in most of the calixarene salts.     

Supramolecular aspects of iron(II) crown-dipyridyl spin-crossover compounds

The synthesis, structures and magnetism of the complexes [Fe^II(3-bpp)₂][bpmdcK](SeCN)_1.7(ClO₄)_1.3·MeOH·H₂O (1), [Fe^II(3-bpp)₂]₄[bpmdcH₂(H₂O)₂](ClO₄)₁₀·7H₂O·3MeOH (2) and cis-[Fe^II₂(NCSe)₂((3,5-Me₂pz)₃CH)₂(μ-bpmdc)]·2MeCN (3) (where 3-bpp = 2,6-di(pyrazole-3yl)pyridine, bpmdc = N,N′-bis(4-pyridyl-methyl)diaza-18-crown-6) and (3,5-Me₂pz)₃CH = tris(3,5-dimethylpyrazole)methane, are presented. These compounds form a study of the supramolecular influence of host–guest/crown-ether interactions and cation-to-crown hydrogen-bonding effects upon d⁶ spin transitions, the latter occurring above, or near to, room temperature in 1 and 2. Desolvation effects also influence the T_1/2 values. The dinuclear compound 3 contains covalent pyridyl (crown) N to Fe bridge bonding and remains high spin.     

Stereospecific ligands and their complexes. IV: Synthesis,characterization and cytotoxicity of novel platinum(IV) complexes with ethylenediamine-N,N′-di-S,S-2-propanoate and halogenido ligands: Crystal structure of s-cis-[Pt(S,S-eddp)Cl2]·4H2O and uns-cis-[Pt(S,S-eddp)Br2]

The syntheses of two novel platinum(IV) complexes of formula [PtX₂(S,S-eddp)]·nH₂O (S,S-eddp = ethylenediamine-N,N′-di-S,S-2-propanoate ion, X = chlorido (1) or bromido (2), n = 4, 0) are reported. The complexes have been obtained by direct reaction of corresponding potassium hexahalogenidoplatinate(IV) with neutralized ethylenediamine-N,N′-di-S,S-2-propanoic acid (H₂-S,S-eddp). The complexes were characterized by elemental analysis, infrared, ¹H and ¹³C NMR spectroscopy. The spectroscopically predicted geometrical configurations of the obtained complexes were confirmed by X-ray analyses of the crystal structures of the s-cis-[Pt(S,S-eddp)Cl₂]·4H₂O and uns-cis-[Pt(S,S-eddp)Br₂]. These complexes displayed significantly lower in vitro cytotoxicity in comparison to cisplatin.     

Metal complexes of tetradentate and pentadentate N-o-hydroxybenzamido-meso-tetraphenylporphyrin ligand: M(N-NCO(o-OH)C6H4-tpp) (M = Zn2+, Ni2+, Cu2+) and M′(N-NCO(o-O) C6H4-tpp) (M′ = Mn3+) (tpp = 5, 10, 15, 20-tetraphenylporphyrinate)

The crystal structures of N-o-hydroxybenzimido-meso-tetraphenylporphyrinatozinc(II) toluene solvate [Zn(N-NCO(o-OH)C₆H₄-tpp)·C₆H₅CH₃; 4·C₆H₅CH₃], N-o-hydroxybenzimido-meso-tetraphenylporphyrinatonickel(II) chloroform solvate [Ni(N-NCO(o-OH)C₆H₄-tpp)·0.6CHCl₃; 5·0.6 CHCl₃], N-o-hydroxybenzimido-meso-tetraphenylporphyrinatocopper(II) toluene solvate [Cu(N-NCO(o-OH)C₆H₄-tpp)·C₆H₅CH₃; 6·C₆H₅CH₃] and N-o-oxido-benzimido-meso-tetraphenylporphyrinato(-κ⁴,N¹,N²,N³,N⁵,κO²) manganese (III) methylene chloride·methanol solvate [Mn(N-NCO(o-O)C₆H₄-tpp)·CH₂Cl₂·MeOH; 8·CH₂Cl₂·MeOH] were established. The coordination sphere around Zn²⁺ ion in 4·C₆H₅CH₃, (or Ni²⁺ ion in 5·0.6 CHCl₃ or Cu²⁺ ion in 6·C₆H₅CH₃) is a distorted square planar (DSP) whereas for Mn³⁺ in 8·CH₂Cl₂·MeOH, it is a distorted trigonal bipyramid (DTBP) with O(1), N(1) and N(3) lying in the equatorial plane for 8·CH₂Cl₂·MeOH. The g value of 8.27 measured from the parallel polarization of X-band EPR spectra at 293 K is consistent with the high-spin mononuclear manganese(III) (S = 2) in 8. The magnitude of axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) in 8 was determined approximately as 3.0 cm^?1 by the paramagnetic susceptibility measurements and conventional EPR spectroscopy.     

Biological study and electrochemical characterization of Cu(II) and 1,8-bis-(2-pyridyl)-3,6-dithiaoctane (pdto) complex

Preliminary proliferation assays in human tumor cervix line HeLa, using the coordination compound [Cu(pdto)H₂O]²⁺ (pdto = 1,8-bis-(2-pyridyl)-3,6-dithiaoctane) and its precursors Cu(NO₃)₂ · 2.5H₂O and pdto, were carried out. The results showed that the copper complex has a behavior similar to that of the reference drug cis-platin. No biological activity for the non-coordinated ligand and the copper salt was found. It was established by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, that the complex [Cu(pdto)H₂O]²⁺ presents an electrochemical reversible Cu(II)/Cu(I) reduction, in acetonitrile solution, meanwhile, the copper salt Cu(NO₃)₂ · 2.5H₂O exhibited an electrochemical irreversible behavior. A comparison between biological and electrochemical results corresponding to [Cu(pdto)H₂O]²⁺ and Cu(NO₃)₂ · 2.5H₂O let us to proposed, the electrochemical reversibility, as one important factor in the antitumoral activity of the copper complex. Due to the nature of the studies presented in this work, other factors like intercalation properties with DNA cannot be neglected in the antitumoral activity of the complex.     

Synthesis,molecular and supramolecular structures,electrochemistry and magnetic properties of two macrocyclic dicopper(II) complexes: Microporous supramolecular assembly

Synthesis, molecular and supramolecular structures, electrochemistry and magnetic properties of two diphenoxo-bridged dicopper(II) compounds [Cu^II₂L(H₂O)(ClO₄)]·ClO₄·2H₂O (1) and [Cu^II₂L(N₃)₂]·2H₂O (2) derived from a tetraimino diphenolate macrocyclic ligand H₂L, obtained on [2+2] condensation of 4-methyl-2,6-diformylphenol and 2,2′-dimethyl-1,3-diaminopropane, are presented. Supramolecular structure of both 1 and 2 are three-dimensional resulting from hydrogen bonding interactions. Interestingly, the 3-D self-assembly of 2 contains micropores having the dimension of 0.35 nm. Electrochemical analyses reveal that both of these compounds exhibit two-step couples in the reduction window. Variable-temperature (2–300 K) magnetic susceptibilities measurements of the two compounds reveal that the metal centers in both of the complexes are coupled by strong antiferromagnetic interactions with J values (H = ?JS₁·S₂) ?776 and ?836 cm^?1 for 1 and 2, respectively.     

Versatile binding properties of di-pyridyl ligands with Cu(II) complexes: The syntheses,structural characterization and thermal analysis of six new species

A novel series of 4,4′-bipyridine- and 1,2-bis(4-pyridyl)ethane-Cu(II) complexes were synthesized using a variety of amine ligands (DPA = di(2-pyridylmethyl)amine, Medpt = 3,3′-diamino-N-methyldipropylamine, Hbpca = bis(2-pyridylcarbonyl)amine, TPA = tris(2-pyridylmethyl)amine) and cyclen = 1,4,7,10-tetraazacyclododecane). Different complexes were obtained including mononuclear [Cu(cyclen)(4,4′-bipy)](ClO₄)₂ (1), dinuclear {[Cu(μ₂-bpca)(4,4′-bipy)(H₂O)]ClO₄}₂ (2), [Cu₂(DPA)₂(μ₂-4,4′-bipy)(ClO₄)₄)]·H₂O (3), [Cu₂(cyclen)₂(μ₂-bpe)](ClO₄)₄ (4) and [Cu₂(TPA)₂(μ₂-bpe)](ClO₄)₄ (5) and the 1-D polymer, {[Cu(Medpt)(μ₂-4,4′-bipy)](ClO₄)₂}_n (6). In the 1–6 samples, cooling up to 100 K produces only the expected, minor, changes in cell constants given no space group changes. Therefore, data for the 100 K structures are reported only. Single-crystal X-ray crystallography reveals the monodentate coordination of the 4,4′-bipy in 1 and 2, and the bridged nature of the di-pyridyl ligands in the dinuclear complexes 2–5 and in the polymeric complex 6. In this series, structures 3–6 consist of the 4,4′-bipy or bpe bridging the two Cu(II) centers, the coordination by the tri- or the tetra-N donors of the amine, and the ClO₄^? groups as counter ions in 4–6 complexes. In the complexes 3–6, the Cu···Cu distances across the bridged di-pyridyl ligands were found to be greater than 11 Å. The magnetic properties of complex 3 reveal no evidence for magnetic coupling between the two Cu(II) centers (J = ?0.58 cm^?1).     

The reaction of amidinato(pyridine) complexes of molybdenum and tungsten with triethylborane adduct of N-heterocyclic carbene (NHC · BEt3): Investigation on the reactivity of NHC · BEt3 as carbene precursor toward transition metal complexes

The reaction of triethylborane adduct of N-heterocyclic carbene, NHC · BEt₃, (NHC = IⁱPr = 1,3-diisopropylimidazol-2-ylidene (IⁱPr · BEt₃; 1a), NHC = IMes = 1,3-dimesitylimidazol-2-ylidene (IMes · BEt₃; 1b)), which was prepared by the reaction of the corresponding imidazolium salt with one equivalent of LiBEt₃H, with amidinato(pyridine) complex, [M(η³-allyl){η²-(NPh)₂CH}(CO)₂(NC₅H₅)] (M = Mo; 2-Mo M = W; 2-W), was investigated. The reaction of compound 1 with complex 2 under toluene-reflux conditions resulted in the formation of carbene complex [M(η³-allyl){η²-(NPh)₂CH}(CO)₂(NHC)] (M = Mo, NHC = IⁱPr; 3a-Mo, M = Mo, NHC = IMes; 3b-Mo, M = W, NHC = IⁱPr; 3a-W, M = W, NHC = IMes; 3b-W). These complexes were characterized spectroscopically as well as by X-ray analyses. Complex 3a-Mo was formed in various solvents such as 1,2-dimethoxyethane (DME), 1,2-dichloroethane, and acetonitrile under refluxing conditions for 3 h. In toluene, 3a-Mo was obtained in a good yield by heating at 70 °C for only 20 min. Employment of NHC · BEt₃ (1) was found to afford convenient route for the introduction of the carbene ligand to the transition metal complexes.