Thio-azo proligands based on 5,6-derivatives-1,10-phenanthroline and their use for iron(II) complexes: Synthesis,characterization and crystal structures

The preparation and characterization of 5,6-substituted-1,10-phenanthrolines, phdtos = 5,6-bistosyl-1,10-phenanthroline (1) and phdbt = 5,6-dibenzyltiol-1,10-phenanthroline (2) are described. The synthesis of (1) was achieved in good yield via the corresponding dihydroxide and 2 was obtained by cross-coupling reaction of 5,6-dibromo-1,10-phenanthroline and benzylthiol mediated by a palladium catalytic system in refluxing toluene (120 °C). These phenanthroline derivatives were used as ligands to afford [Fe^II(phdtos)₃](PF₆)₂ (5) and [Fe^II(phdbt)₃](PF₆)₂ (6) complexes.     

Pd(II) complexes of novel phosphine ligands: Synthesis,characterization, and catalytic activities on Heck reaction

Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH₃, monitored by ³¹P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.     

Decanuclear Ln10 Wheels and Vertex‐Shared Spirocyclic Ln5 Cores: Synthesis,Structure, SMM Behavior,and MCE Properties

The reaction of a Schiff base ligand (LH₃) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln₁₀ (Ln=Dy( 1 ), Tb( 2 ), and Gd ( 3 )) and pentanuclear Ln₅ complexes (Ln=Gd ( 4 ), Tb ( 5 ), and Dy ( 6 )), respectively. The formation of Ln₁₀ and Ln₅ complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes ( 1 – 6 ) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (U_eff)=16.12(8) K and relaxation time (τ_o)=3.3×10^?5 s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out‐of‐phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: ?ΔS_m=26.6 J kg^?1 K^?1 at T=2.2 K for 3 and ?ΔS_m=27.1 J kg^?1 K^?1 at T=2.4 K for 4 , both for an applied field change of 7 T.     

Structure and conformational processes of bis(o-cumyl)sulfide, sulfoxide and sulfone

The NMR solution spectra of the title sulfide and sulfone show decoalescence of the geminal methyl signals of the isopropyl groups at low temperature (−178 °C for the ¹³C signal of sulfide at 150.8 MHz and −147 °C for the ¹H signal of sulfone at 600 MHz). The barriers for the related dynamic processes were measured (4.3 and 7.0 kcal mol⁻¹ for the sulfide and sulfone, respectively). The preferred conformer of sulfide has a propeller shape with a C₁ symmetry, as suggested by Molecular Mechanics (MM) calculations. In the case of sulfone the preferred conformer has a propeller shape with a C₂-anti symmetry, as indicated by calculations and supported by X-ray crystallographic determination. The computed contour map of the potential energy shows that in both cases the dynamic processes take place via correlated rotations (cogwheel mechanism) of the two aromatic substituents about the Ar-S bonds. Dynamic processes could not be observed by NMR in the title sulfoxide, which was also found to adopt a propeller shaped conformation, as indicated by MM calculations and X-ray diffraction.     

Binuclear and polynuclear transition metal complexes with macrocyclic ligands 1. Synthesis and the structure of an antiferromagnetic binuclear nickel complex prepared by the reaction of o-phenylenediamine with pyrrole-2,5-dicarbaldehyde and nickel pivalate

The reaction of pyrrole-2,5-dicarbaldehyde (1) with o-phenylenediamine (2) in anhydrous EtOH afforded a [1+1]-condensation product, viz., Schiff"s base. The structure of the latter was established by NMR spectroscopy and X-ray diffraction analysis. The reaction of this product or a mixture of 1 and 2 with Ni₉(_n-OOCBu^t)₁₂(HOOCBu^t)₄(₄-OH)₃(₃-OH)₃ in MeCN in the presence of AcOH gave rise to an antiferromagnetic binuclear complex. According to the X-ray diffraction data, the macrocycle in the latter complex is a [2+2]-condensation product of compounds 1 and 2, _eff ranging from 0.569 to 2.614 B (2—301 K), –2J = 360 cm^–1. The Ni₂(OAc)₂ fragment is located in the central cavity of the macrocycle. The structures of the condensation products are discussed based on the results of DFT quantum-chemical calculations.     

Synthesis and properties of new Mo(II) complexes with N-heterocyclic and ferrocenyl ligands

New Mo(II) complexes with 2,2′-dipyridylamine (L1), [Mo(CH₃CN)(η³-C₃H₅)(CO)₂(L1)]OTf (C1a) and [{MoBr(η³-C₃H₅)(CO)₂(L1)}₂(4,4′-bipy)](PF₆)₂ (C1b), with {[bis(2-pyridyl)amino]carbonyl}ferrocene (L2), [MoBr(η³-C₃H₅)(CO)₂(L2)] (C2), and with the new ligand N,N-bis(ferrocenecarbonyl)-2-aminopyridine (L3), [MoBr(η³-C₃H₅)(CO)₂(L3)] (C3), were prepared and characterized by FTIR and ¹H and ¹³C NMR spectroscopy. C1a, C1b, L3, and C2 were also structurally characterized by single crystal X-ray diffraction. The Mo(II) coordination sphere in all complexes features the facial arrangement of allyl and carbonyl ligands, with the axial isomer present in C1a and C2, and the equatorial in the binuclear C1b. In both C1a and C1b complexes, the L1 ligand is bonded to Mo(II) through the nitrogen atoms and the NH group is involved in hydrogen bonds. The X-ray single crystal structure of C2 shows that L2 is coordinated in a κ²-N,N-bidentate chelating fashion. Complex C3 was characterized as [MoBr(η³-C₃H₅)(CO)₂(L3)] with L3 acting as a κ²-N,O-bidentate ligand, based on the spectroscopic data, complemented by DFT calculations.The electrochemical behavior of the monoferrocenyl and diferrocenyl ligands L2 and L3 has been studied together with that of their Mo(II) complexes C2 and C3. As much as possible, the nature of the different redox changes has been confirmed by spectrophotometric measurements. The nature of the frontier orbitals, namely the localization of the HOMO in Mo for both in C2 and C3, was determined by DFT studies.     

1H, 13C and 15N NMR coordination shifts in gold(III), cobalt(III), rhodium(III) chloride complexes with pyridine, 2,2'-bipyridine and 1,10-phenanthroline

Au(III), Co(III) and Rh(III) chloride complexes with pyridine (py), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) of the general formulae [M1LCl3], trans-[M2L4Cl2]+, mer-[M2L3Cl3], [M1(LL)Cl2]+, cis-[M2(LL)2Cl2]+, where M1=Au; M2=Co, Rh; L=py; LL=bpy, phen, were studied by 1H--13C HMBC and 1H--15N HMQC/HSQC. The 1H, 13C and 15N coordination shifts (the latter from ca-78 to ca-107 ppm) are discussed in relation to the type of metal, electron configuration, coordination sphere geometry and the type of ligand. The 13C and 15N chemical shifts were also calculated by quantum-chemical NMR methods, which reproduced well the experimental tendencies concerning the coordination sphere geometry and the ligand type.     

A Diazabutadiene stabilized Nickel(0) Cyclooctadiene Complex: Synthesis,Characterization and the Reaction with Diphenylacetylene

The reaction of [Ni(COD)₂] with one equivalent of DAB^Mes (DAB^Mes = (2,4,6‐Me₃C₆H₂)N=C(Me)‐C(Me)=N(2,4,6‐Me₃C₆H₂)) affords a mixture of the compound [Ni(DAB^Mes)₂] ( 2 ) and starting material [Ni(COD)₂]. The crystallographically characterized, diamagnetic complex 2 can be obtained in a stoichiometric reaction of [Ni(COD)₂] and two equivalents of DAB^Mes. This reaction can be accelerated by addition of 1‐chloro‐fluorobenzene or methyl iodide. In the presence of 1‐chloro‐fluorobenzene, [Ni(DAB^Mes)(COD)] ( 3 ) is available via reaction of [Ni(COD)₂] and one equivalent of DAB^Mes. The crystallographically characterized complex 3 reacts with diphenylacetylene to afford [Ni(DAB^Mes)(Ph‐C≡C‐Ph)] ( 4 ). A long‐wavelength absorption band in the UV‐Vis spectrum of this compound has to be assigned to a mixed MLCT/LL′CT transition, as quantum chemical calculations reveal.     

Electronic Structure and Hydrogen Bonding in a Dicobalt(III) Werner Complex

The bonding of the O-O group in the dicobalt cation 1a [(NH₃)₆Co₂(μ-O₂)(μ-OH)(μ-NH₂)]³⁺ was studied by DFT methods (ADF program) and the bridging O₂ ligand was characterized as superoxide(O₂⁻). In this complex, three bridging ligands connect the two cobalt atoms, forcing a cis conformation of the Co-O-O-Co atoms. A comparison was made with [(NH₃)₁₀Co₂(μ-O₂)]⁵⁺, 2a, where a trans arrangement is observed. Superoxide binds more strongly to the dicobalt(III) fragment in 2a than in 1a, both as a result of weaker Pauli repulsion and stronger covalent interaction. It was found that in 1a the electronic structure with one unpaired electron, where cobalt is formally Co(III), d⁶, and O₂ carries one negative charge gives rise to the most stable structure, compared to possibilities with three and five unpaired electrons. The hydrogen bonds in the crystal were analyzed and the interactions between one water molecule or one nitrate ion studied in more detail.     

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.     

Synthesis, spectral studies, crystal structures and TDDFT studies of the rhenium(I) complexes of 2,4-dihydroxy-N′-(4-hydroxybenzilidene) benzohydrazide

The rhenium(I) carbonyl bromide complex, [ReBr(CO)₃(HL)], of the ligand derived from 2,4-dihydroxybenzaldehyde and 4-hydroxybenzoic acid hydrazide (HL), has been prepared. HL and its complex have been characterized by elemental analysis, MS, IR, UV-Vis and ¹H NMR spectroscopic methods. The structure of HL and the aqua-complex [Re(OH₂)(CO)₃(L)] where the ligands are monodeprotonated have been elucidated by X-ray diffraction. The structure of [ReBr(CO)₃(HL)] has been calculated from conformational parameters found in the aqua-complex. DFT and TDDFT calculations have been performed to obtain the IR spectra and UV-Vis absorption and emission spectra. The calculated spectra agree with the experimental results.     

Synthesis and characterization of dinuclear pyrazolato bridged platinum(IV) complexes

Reactions of [PtMe₃(OCMe₂)₃](BF₄) and [(PtMe₃I)₄] with pyrazole (pzH) afforded mononuclear pyrazole platinum(IV) complexes [PtMe₃(pzH)₃](BF₄) (1) and [PtMe₃I(pzH)₂] (2), respectively. The formation of dinuclear pyrazolato bridged platinum(IV) complexes (PPN)[(PtMe₃)₂(μ-pz)₃] (3), (PPN)[(PtMe₃)₂(μ-I)(μ-pz)₂] · 1/2Et₂O (4) and [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (5) was achieved by the reaction of each 1 and 2 with [PtMe₃(OCMe₂)₃](BF₄) in the presence of KOAc followed by reaction with (PPN)Cl (PPN⁺ = bis(triphenylphosphine)iminium cation) and 18C6, respectively. The reaction of complex 4 with AgO₂CCF₃ followed by addition of RSR′ (R/R′ = Me/Me, Me/Ph) resulted in the formation of complexes [(PtMe₃)₂(μ-pz)₂(μ-RSR′)] (R/R′ = Me/Me, 6; Me/Ph, 7). All complexes were characterized unambiguously by microanalysis and NMR (¹H, ¹³C) spectroscopic investigations. Additionally, crystal structures of complexes 3 and 4 as well as DFT calculation are presented. Furthermore, in vitro studies on the anti-proliferative activity of complexes 2 and 5 were carried out.     

Synthesis and crystal structure of nickel(II) complexes with bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine

A series of nickel(II) complexes having the (Me-Tp)₂PMA ligand ((Me-Tp)₂PMA = bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine) with nitrates (1), chlorides (2), and perchlorates (3) as anions were synthesized and isolated. All these complexes were successfully characterized by physicochemical methods including X-ray crystallographic analysis. In complex 1, the ligand binds in a bidentate N₂ fashion, whereas in the cases of 2 and 3 the ligand binds in the tridentate N₂S form. The coordination geometry around the nickel(II) atoms in these complexes is distorted octahedral.     

Polynuclear iron(III) pivalates

The formation of magnetically active polynuclear Fe^III pivalates in the FeSO₄·7H₂O-KOOCCMe₃ system was studied. The reaction of FeSO₄·7H₂O (1) with KOOCCMe₃ in EtOH in air afforded the antiferromagnetic trinuclear complex [Fe₃O(OOCCMe₃)₆(H₂O)₃]⁺[OOCCMe₃]^–·3EtOH. A change of the solvent (EtOH) in this system to a 40:1 benzene—THF mixture resulted in the formation of the antiferromagnetic hexanuclear cluster [Fe₆(O)₂(OH)₂(OOCCMe₃)₁₂(HOOCCMe₃)(THF)]·1.5C₆H₆. The addition of trimethylacetic acid to EtOH and recrystallization from hexane gave rise to the antiferromagnetic coordination polymer [K₂Fe₄(O)₂(OOCCMe₃)₁₀(HOOCCMe₃)₂(H₂O)₂]_n (7). Recrystallization of the latter from acetonitrile afforded the antiferromagnetic tetranuclear complex K₂Fe₄(O)₂(OOCCMe₃)₁₀(HOOCCMe₃)₂(MeCN)₂. The structures of these compounds were established by X-ray diffraction analysis, and their magnetic susceptibilities and thermal decomposition were investigated.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2403–2413, November, 2004.     

Synthesis and characterization of new platinum(II) phosphinate complexes

The syntheses of platinum(II) complexes of bis(dimethylphosphinylmethylene)amine and bis(aminomethyl)phosphinic acid were investigated. In the case of bis(dimethyl-phosphinylmethylene)amine the reaction with K₂[PtCl₄] yields the potassium amino-trichloroplatinate K[PtCl₃L] (L?=?bis(dimethylphosphinylmethylene)amine), which was characterized by multinuclear (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) NMR spectroscopy in solution. Bis(aminomethyl)phosphinic acid reacts with K₂[PtCl₄] under strictly controlled pH conditions to give colorless crystals of the cisplatin analog K[PtCl₂L′] (L′?=?bis(aminomethyl)phosphinate). This complex was characterized by multinuclear NMR spectroscopy in solution as well as by single-crystal X-ray diffraction in the solid state. The bis(aminomethyl)phosphinate coordinates to platinum via both amino functions, thus acting as a chelating ligand.     

Synthesis, crystal structures, and properties of oxovanadium(IV)-lanthanide(III) heteronuclear complexes

A new series of oxovanadium(IV)-lanthanide(III) heteronuclear complexes [Yb(H2O)8]2[(VO)2(TTHA)](3)21 H2O (1), {[Ho(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)} 8.5 H2O (2), {[Gd(H2O)7(VO)2(TTHA)][(VO)2(TTHA)](0.5)}8.5 H2O (3), {[Eu(H2O)7][(VO)2(TTHA)](1.5)} 10.5 H2O (4), and [Pr2(H2O)6(SO4)2][(VO)2(TTHA)] (5) (H6TTHA=triethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H(6)TTHA as structure-directing agent. X-ray crystallographic studies reveal that they contain the same [(VO)2(TTHA)]2- unit as building block, but the Ln3+ ion lies in different coordination environments. Although the lanthanide ions always exhibit similar chemical behavior, the structures of the complexes are not homologous. Compound 1 is composed of a [Yb(H2O)8]3+ ion and a [(VO)2(TTHA)]2- ion. Compounds 2 and 3 are isomorphous; both contain a trinuclear [Ln(H2O)7(VO)2(TTHA)]+ (Ln=Ho for 2 and Gd for 3) ion and a [(VO)2(TTHA)]2- ion. Compound 4 is an extended one-dimensional chain, in which each Eu3+ ion links two [(VO)2(TTHA)]2- ions. For 5, the structure is further assembled into a three-dimensional network with an interesting framework topology comprising V2Pr2 and V4Pr2 heterometallic lattices. Moreover, 4 and 5 are the first oxovanadium(IV)-lanthanide(III) coordination polymers and thus enlarge the realm of 3d-4f complexes. The IR, UV/Vis, and EPR spectra and the magnetic properties of the heterometallic complexes were studied. Notably, 2 shows unusual ferromagnetic interactions between the VO2+ and Ho3+ ions.     

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C5HF6O2)4] (Ln=La,Gd, Lu)

The molecular structures of potassium tetrakis(hexafluoroacetylacetonato)lanthanide(III) complexes [KLn(hfa)₄] (Ln=La, Gd, Lu; hfa=C₅HF₆O₂,) were studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublime congruently and the vapors contain a single molecular species: the heterobinuclear complex [KLn(hfa)₄]. All molecules are of C₁ symmetry with the lanthanide atom in the center of an LnO₈ coordination polyhedron, while the potassium atom is coordinated by three ligands with formation of three K−O and three K−F bonds. One hfa ligand is not bonded to the potassium atom. Topological analysis of the electron-density distributions confirmed the existence of ionic-type K−O and K−F bonding. The structures of the free [KLn(hfa)₄] molecules are compared with those of the related compounds [KDy(hfa)₄] and [KEr(hfa)₄] in their crystalline state. The complex nature of the chemical bonding is discussed on the basis of electron-density topology analyses.     

Synthesis,spectroscopic characterization,crystal and molecular structure of [ReOBr(hmquin-7-COOH)2] and [ReOCl(hmquin-7-COOH)2] · MeCN complexes. DFT and TD-DFT calculations for [ReOBr(hmquin-7-COOH)2]

Novel [ReOBr(hmquin-7-COOH)₂] (1) and [ReOCl(hmquin-7-COOH)₂] · MeCN (2 · MeCN) complexes have been prepared by treatment of [ReOX₃(AsPh₃)₂] with an excess of 8-hydroxy-2-methylquinoline-7-carboxylic acid in acetonitrile. The compounds were characterized structurally and spectroscopically. The electronic structure of 1 has been calculated with the density functional theory (DFT) method, and additional information about binding has been obtained by NBO analysis. The UV–Vis spectrum of 1 has been discussed on the basis of TDDFT calculations.