Pentacyanido(L)ferrate(III) complexes: Crystal structures, electrochemical and DFT studies (L = pyrazine, 4,4′-bipyridine, azide)

The crystal structures of two pentacyanido(L) ferrate(III) complexes, [P(C₆H₅)₄]₂[Fe(CN)₅(prz)]·4H₂O 1, [P(C₆H₅)₄]₂[Fe(CN)₅(4,4′-bipy)]·3H₂O 2, have been solved. Within the two complex anions the iron atoms are hexacoordinated by five cyanido ligands, the sixth position being occupied by the nitrogen atom arising from pyrazine and, respectively, 4,4′-bipyridine. The electrochemical properties of compounds 1, 2 and of the azido derivative, (Ph₄As)₂[Na(H₂O)₄][Fe(CN)₅(N₃)] 3, have been investigated by cyclic voltammetry. A relatively complicated redox behavior of these complexes was found, due especially to the electron transfer involving the central metallic ion that changes reversibly its oxidation state (Fe^III/Fe^II redox site) and also to the coligand (4,4′-bipyridine, pyrazine or azide) which intervenes in a distinct electron transfer. The experimental data have been rationalized through DFT calculations.     

Reactivities governed by a single metal atom M in mixed-metal highnuclearity clusters having [Ru5M(C)] core (M = Co, Rh, Pd): Site-nonselective, site-selective, and chemo-selective variations in the SO2-trapping reactions

The SO₂ substitution for a CO ligand of the hexa-nuclear carbonyl complexes having Ru₅M(C) type carbido-metal core, [PPN][Ru₅Co(C)(CO)₁₆] (2), [PPN][Ru₅Rh(C)(CO)₁₆] (3), and Ru₅Pd(C)(CO)₁₆ (4), is dramatically affected by the kind of metal atom M: 2 (M = Co) is reactive but not site-selective, 3 (M = Rh) is reactive and site-selective, whereas 4 (M = Pd) is not reactive at all even though 4 can easily react with PPh₃ to give the substitution products.     

Rhodium(III) and iridium(III) complexes of thioarylazoimidazoles: Synthesis,structure, spectral characterization,electrochemistry and DFT calculation

[M(SRaaiNR′)Cl₃] (M = Rh(III), Ir(III) and SRaaiNR′ = 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole) complexes are described in this article. The single crystal X-ray structure of one of the complexes, [Rh(SMeaaiNEt)Cl₃] (3b), shows a tridentate chelation of SMeaaiNEt via N(imidazole), N(azo) and S(thioether) donor centres. Spectral characterization has been done by IR, UV–Vis and ¹H NMR data. The electronic structure, redox properties and spectra are well supported by DFT and TDDFT computation on the complexes.     

Cyclometalated iridium(III) complexes containing 2-phenyl-2H-indazole ligand: Synthesis,photophysical studies,and DFT calculations

Heteroleptic cyclometalated iridium(III) complexes ( Ir1 – Ir5 ) featuring piz-based ligands and acetylacetone ancillary ligand are synthesized and characterized. Their photophysical and electrochemical properties were studied, and DFT calculations were used to further support the experiment results. All the complexes emit yellow color with quantum yields of 12.2–56.5% in dichloromethane solution at room temperature, and the emission originates from a hybrid ³MLCT/³ILCT/³LLCT excited state.     

Rhenium(I), (III) and (V) complexes of tridentate ONX (X = O,N, S)-donor Schiff bases

The reactions of the potentially tridentate Schiff bases 2-[(2-hydroxyphenyl)iminomethyl]phenol (H₂ono) and 2-(2-aminobenzylideneimino)phenol (H₃onn) with trans-[ReOBr₃(PPh₃)₂] were studied, and the complexes [Re^IIIBr(PPh₃)₂(ono)] (1) and [Re^VBr(PPh₃)₂(onn)]Br (2) were isolated. In 1ono acts as a dianionic tridentate ligand, and in 2onn is coordinated as a tridentate trianionic imido-imino-phenolate. The complex [Re^I(CO)₃(ons)(Hno)] was isolated from the reaction of [Re(CO)₅Br] with 2-[(2-methylthio)benzylideneimino]phenol (Hons; Hno = 2-aminophenol), with ons coordinated as a bidentate chelate with a free SCH₃ group. These complexes were characterized by X-ray crystallography, NMR and IR spectroscopy.     

Synthesis, spectroscopic characterization, X-ray structure and DFT calculations of rhenium(III) complex with bis(3,5-dimethylpyrazol-1-yl)methane

[ReCl₃(MeCN)(PPh₃)₂] reacts with bis(3,5-dimethypyrazol-1-yl)methane (bdmpzm) in acetone to give [ReCl₃(bdmpzm)(PPh₃)]. The compound has been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The molecular orbital diagram of [ReCl₃(bdmpzm)(PPh₃)] has been calculated with the density functional theory (DFT) method.     

Synthesis,crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

A new copper(II) complex of an unsymmetrical tripodal ligand (NN₂O222) derived from tris(2-aminoethylamine)amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN₂O222)Cu(ImH)](ClO₄)₂·0.5H₂O (NN₂O222?=?2-[bis(2-aminoethyl)amino]ethanol; ImH?=?imidazole). Crystals of the complex are orthorhombic, space group Pna2₁, with a?=?29.983(10), b?=?15.568(5), c?=?8.127(3)?Å. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu^II/Cu^I redox behavior at +44?mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO₄)₂·6H₂O.     

Synthesis and structural aspects of M-allyl (M = Ir, Rh) complexes

The synthesis, characterization and chemistry of novel η³-allyl metal complexes (M = Ir, Rh) are described. The structures of compounds (C₅Me₄H)Ir(PPh₃)Cl₂ (1), (C₅Me₄H)Ir(PPh₃)(η³-1-methylallyl)Br (3a), (C₅Me₄H)Ir(η⁴-1,3,5-hexatriene) (8), and (C₅Me₅)Rh(η³-1-ethylallyl)Br (5d) have been determined by X-ray crystallography. Structural comparisons among these complexes are discussed. It is found that the neutral metal allylic complex [Cp^∗IrCl(η³-methylallyl)] (5) ionizes in polar solvents to give [Cp^∗Ir(η³-methylallyl)]⁺Cl⁻ (6) and reaches equilibrium (5 ? 6) at room temperature. Addition of tertiary phosphine ligands to neutral complexes such as [Cp^∗Ir(η³-methylallyl)Cl], results in the formation of stable ionic phosphine adducts. Factors such as solvent, length of carbon chain, temperature and light are discussed with respect to the formation, stability and structure of the allyl complexes.     

Synthesis,spectroscopic characterization,X-ray structure and DFT calculations of rhenium(III) complex with 1-isoquinolinyl phenyl ketone

The [ReCl₃(MeCN)(PPh₃)] complex reacts with 1-isoquinolinyl phenyl ketone (N–O) to give [ReCl₃(N–O)(PPh₃)]. The compound has been studied by IR, UV–Vis spectroscopy, magnetic measurements and X-ray crystallography. The magnetic behavior is characteristic of mononuclear octahedral Re(III) complex with d⁴ low-spin (³T_1g ground state) and arises because of the large spin–orbit coupling, which gives diamagnetic ground state. The molecular orbital diagram of [ReCl₃(N–O)(PPh₃)] has been calculated with the density functional theory (DFT) method, and time-dependent DFT (TD-DFT) calculations have been employed in order to discussion of its spectroscopic properties in more detail.     

New complexes of lanthanide Ln(III), (Ln = La, Sm, Gd, Er) with Schiff bases derived from 2-furaldehyde and phenylenediamines

Some new Schiff bases derivates from 2-furaldehyde and phenylenediamines (L^1-3) and their complexes with lanthanum (La), samarium (Sm), gadolinium (Gd) and erbium (Er) have been synthesized. These complexes with general formula [Ln(L^1-3)₂(NO₃)₂]NO₃·nH₂O (Ln = La, Sm, Gd, Er) were characterized by elemental analysis, UV-Vis, FT-IR and fluorescence spectroscopy, molar conductivity and thermal analysis. The metallic ions were found to be eight coordinated. The emission spectra of these complexes indicate the typical luminescence characteristics of the Sm(III), La(III), Er(III) and Gd(III) ions.     

Syntheses, structures and DFT study of [W(CO)5(Ph2SbX)] X = Cl, Br, I

The complexes [W(CO)₅(Ph₂SbX)], X = Cl (1), Br (2) and I (3) were prepared by reaction of [W(CO)₅(tetrahydrofuran)] with Ph₂SbX. The structures of 1-3 were studied by X-ray diffraction. In the crystals there are weak contacts between the oxygen atoms of the CO ligands and antimony atoms of neighbouring molecules. DFT calculations were carried out for 1 using gradient corrected functional B3LYP. The bonding between Ph₂SbCl and the W(CO)₅ fragment in 1 was analysed using charge decomposition analysis.     

F NMR spectroscopy as useful tool for determining the structure in solution of coordination compounds of MF5 (M = Nb, Ta)

The salts [S(NMe₂)₃][MF₆] (M = Nb, 2a; M = Ta, 2b) and [S(NMe₂)₃][M₂F₁₁] (M = Nb, 2c; M = Ta, 2d) have been prepared by reacting MF₅ (M = Nb, 1a; M = Ta, 1b) with [S(NMe₂)₃][SiMe₃F₂] (TASF reagent) in the appropriate molar ratio. The solid state structure of 2b has been ascertained by X-ray diffraction. The 1:1 molar ratio reactions of 1a with a variety of organic compounds (L) give the neutral adducts NbF₅L [L = Me₂CO, 3a; L = MeCHO, 3b; L = Ph₂CO, 3c; L = tetrahydrofuran (thf), 3d; L = MeOH, 3e; L = EtOH, 3f; L = HOCH₂CH₂OMe, 3g; L = Ph₃PO, 3h; L = NCMe, 3i] in good yields. The complexes MF₅L [M = Nb, L = HCONMe₂, 3j; M = Nb, L = (NMe₂)₂CO, 3k; M = Ta, L = (NMe₂)₂CO, 3l; M = Nb, L = OC(Me)CHCMe₂, 3m] have been detected in solution in admixture with other unidentified products, upon 2:1 molar reaction of 1 with the appropriate reagent L. The ionic complexes [NbF₄(tht)₂][NbF₆], 4a, and [NbF₄(tht)₂][Nb₂F₁₁], 4b, have been obtained by combination of tetrahydrothiophene (tht) and 1a, in 1:1 and 2:3 molar ratios, respectively. The treatment of 1 with a two-fold excess of L leads to the species [MF₄L₄][MF₆] [M = Nb, L = HCONMe₂, 5a; M = Ta, L = HCONMe₂, 5b; M = Nb, L = thf, 5c; M = Ta, L = thf, 5d; M = Nb, L = OEt₂, 5e]. The new complexes have been fully characterised by NMR spectroscopy. Moreover, the revised ¹⁹F NMR features of the known compounds MF₅L [M = Ta, L = Me₂CO, 3n; M = Ta, L = Ph₂CO, 3o; M = Ta, L = MePhCO, 3p; M = Ta, L = thf, 3q; M = Nb, L = CH₃CO₂H, 3r; M = Nb, L = CH₂ClCO₂H, 3s; M = Ta, L = CH₂ClCO₂H, 3t], TaF₄(acac), TaF₄(Me-acac) and [TaF(Me-acac)₃][TaF₆] (Me-acac = methylacetylacetonato anion) are reported.     

The structure of 1-formyl-3-phenyl-Δ-pyrazoline in the gas phase (DFT calculations), in solution (NMR) and in the solid state (X-ray crystallography)

The molecular structure of 1-formyl-3-phenyl-Δ²-pyrazoline was determined by X-ray crystallography (triclinic, P-1). The geometry thus obtained was compared with that obtained by DFT calculations. The GIAO method was used to calculate absolute shieldings, which agree conveniently with those measured by ¹³C and ¹⁵N NMR. The title compound appears to be an essentially planar molecule.     

Trifluoroacetylacetonate rhodium(III) methyl complexes, cis-[Rh(TFA)(PPh3)2(CH3)(L)][BPh4] and cis-[Rh(TFA)(PPh3)2(CH3)(I)] (L = CH3CN, NH3, pyridine), in comparison with their acetylacetonate analogs

The oxidative addition of CH₃I to planar rhodium(I) complex [Rh(TFA)(PPh₃)₂] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1), or neutral, cis-[Rh(TFA)(PPh₃)₂(CH₃)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH₃ and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (2) and cis-[Rh(TFA)(PPh₃)₂(CH₃)(Py)][BPh₄] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] in acetone at −15 °C. Complexes 1-5 were characterized by elemental analysis, ³¹P{¹H}, ¹H and ¹⁹F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1-5 and related complexes are discussed from the viewpoint of their isomerism.     

Synthesis, structure, photochromism and DFT calculations of copper(I)-triphenylphosphine halide complexes of thioalkylazoimidazoles

[Cu(SRaaiNR′)(PPh₃)X] complexes are synthesized by the reaction of CuX (X = Cl, Br, I), triphenylphosphine and 1-alkyl-2-[(o-thioalkyl)phenylazo]imidazole (SRaaiNR′). The single crystal X-ray structure of [Cu(SEtaaiNH)(PPh₃)I] (SEtaaiNH = 2-[(o-thioethyl)phenylazo]imidazole) shows a distorted tetrahedral geometry of the copper center with bidentate, N(azo), N(imidazole) chelation of SEtaaiNH and coordination from PPh₃ and iodine. These complexes show a trans-to-cis isomerization upon irradiation with UV light. The reverse transformation, cis-to-trans isomerization, is very slow with visible light irradiation and is thermally accessible. The quantum yields (?_t→c) of the trans-to-cis isomerization of [Cu(SRaaiNR′)(PPh₃)X] are lower than the free ligand values. This is due to the increased mass and rotor volume of the complexes compared to the free ligand data. The rate of isomerization follows the order: [Cu(SRaaiNR′)(PPh₃)Cl] < [Cu(SRaaiNR′)(PPh₃)Br] < [Cu(SRaaiNR′)(PPh₃)I]. The activation energy (E_a) of the cis-to-trans isomerization is calculated by a controlled temperature reaction. DFT computation of representative complexes has been used to determine the composition and energy of the molecular levels.     

Quantum chemistry studies on the Ru-M interactions and the P NMR in [Ru(CO)3(Ph2Ppy)2(MCl2)] (M = Zn, Cd, Hg)

To study the Ru-M interactions and their effects on ³¹P NMR, complexes [Ru(CO)₃(Ph₂Ppy)₂] (py = pyridine) (1) and [Ru(CO)₃(Ph₂Ppy)₂MCl₂] (M = Zn, 2; Cd, 3; Hg, 4) were calculated by density functional theory (DFT) PBE0 method. Moreover, the PBE0-GIAO method was employed to calculate the ³¹P chemical shifts in complexes. The calculated ³¹P chemical shifts in 1-3 follow 2 > 3 > 1 which are consistent to experimental results, proving that PBE0-GIAO method adopted in this study is reasonable. This method is employed to predict the ³¹P chemical shift in designed complex 4. Compared with 1, the ³¹P chemical shifts in 2-4 vary resulting from adjacent Ru-M interactions. The Ru → M or Ru ← M charge-transfer interactions in 2-4 are revealed by second-order perturbation theory. The strength order of Ru → M interactions is the same as that of the P-Ru → M delocalization with Zn > Cd > Hg, which coincides with the order of ³¹P NMR chemical shifts. The interaction of Ru → M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M²⁺, results in the delocalization of P-Ru → M, which decreases the electron density of P nucleus and causes the downfield ³¹P chemical shifts. Except 2, the back-donation effect of Ru ← M, arising from the delocalization from s valence orbital of M²⁺ to the valence orbital of Ru, is against the P-Ru → M delocalization and results in the upfield ³¹P chemical shifts in 4. Meanwhile, the binding energies indicate that complex 4 is stable and can be synthesized experimentally. However, as complex [Ru(CO)₃(Ph₂Ppy)₂HgCl]⁺5 is more stable than 4, the reaction of 1 with HgCl₂ only gave 5 experimentally.     

Copper(II) complexes of bis(pyrazol-1-yl)methane - Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

Two novel copper(II) complexes incorporating bis(pyrazol-1-yl)methane ligand (bpzm) have been synthesized. The compounds [CuCl(bpzm)₂(H₂O)]Cl·H₂O (1) and [Cu(N₃)₂(bpzm)]_n (2) have been studied by IR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies on the compounds 1 and 2 have been accompanied computationally by the density functional theory (DFT) calculations.     

Synthesis, reaction and structure of a series of chromium(III) complexes containing oxalate ligand

A series of chromium(III) complexes [Cr(bipy)(HC₂O₄)₂]Cl·3H₂O (1), [Cr(phen)(HC₂O₄)₂]Cl·3H₂O (2), [Cr(phen)₂(C₂O₄)]ClO₄ (3), [Cr₂(bipy)₄(C₂O₄)](SO₄)·(bipy)_0.5·H₂O (4) and [Mn(phen)₂(H₂O)₂]₂[Cr(phen)(C₂O₄)₂]₃ClO₄·14H₂O (5) were synthesized (bipy=4,4′-bipyridine, phen=1,10-phenanthroline), while the crystal structures of 1 and 3–5 have been determined by X-ray analysis. 1 and 3 are mononuclear complexes, 4 contains binuclear chromium(III) ions and 5 is a 3D supromolecule formed by complicated hydrogen bonding. 1–3 are potential molecular bricks of chromium(III) building blocks for synthesis heterometallic complexes. When we use these molecular bricks as ligands to react with other metal salts, unexpected complexes 4 and 5 are isolated in water solution. The synthesis conditions and reaction results are also discussed.