Dinuclear and polynuclear Cu(II) azido-bridged compounds with 7-azaindole as a ligand. Synthesis, characterization and 3D structures

In this study three new dinuclear Cu(II) compounds with the ligand 7-azaindole (abbreviated as Haza) and bridging end-on azide anions with the general formula [Cu₂(Haza)₄(N₃)₂(A)₂] (in which A =  (1), (2) and (3)) are reported, as well as a dinuclear-based polymeric compound with the overall formula [Cu₄(L)₆(N₃)₆(ClO₄)₂]_n·(CH₃OH)_2n (4). The latter compound contains both end-on and end-to-end azide anions. Full characterization of all four compounds has been performed by spectroscopic methods and by using 3D X-ray structure analysis.     

Dinuclear gold(III) pyrazolato complexes - Synthesis, structural characterization and transformation to their trinuclear gold(I) and gold(I/III) analogues

The reaction of AuCl₃py with Na(pz∗) (pz∗ = pyrazolato, or substituted pyrazolato anion) yields stable dinuclear [cis-Au^IIICl₂(μ-pz∗)]₂ complexes. In the presence of a base, the latter undergo reduction with concomitant transformation of the dinuclear -structure to trinuclear Au^I, Au^III (containing trans Au^IIICl₂-centres) and species.     

Square-planar and trigonal prismatic silver(I) in bipyrimidine and oxalate bridged tetranuclear complexes and one-dimensional compounds: Synthesis and crystal structures

The reaction of [Ag₄(hfac)₄(THF)₂] (hfac⁻ = 1,1,1,5,5,5-hexafluoroacetylacetonate, THF = tetrahydrofurrane) with 2,2′-bipyrimidine (bpm) leads to single crystals. They crystallise in the triclinic system, space group . Their structure consists of [Ag₄(hfac)₄(μ₂-bpm)₃] tetranuclear complexes. In this complex, Ag(I) ions adopt distorted square planar and trigonal prismatic geometries. When [Ag₄(hfac)₄(THF)₂] is replaced by monohydrated silver(I) perchlorate, a one-dimensional (1D) compound with a formula of [[Ag(μ₂-bpm)]⁺]_n, is obtained as single crystals. They crystallise in the monoclinic system, space group P2₁/c. Their structure consists of [[Ag(μ₂-bpm)]⁺]_n chains separated by non-coordinated perchlorate ions. In the chains, the Ag(I) centres adopt a square planar geometry. Finally, starting from [[Ag(μ₂-bpm)]⁺]_n, and sodium oxalate , another 1D compound with a formula of [Ag(μ₂-bpm)(μ₂-ox)]_n, 4nH₂O is obtained as single crystals. They crystallise in the triclinic system, space group . In these chains, bipyrimidine and oxalate are alternate. They generate a square planar geometry around the Ag(I) cations.     

Polynuclear complex formation of trivalent lanthanides by 5-sulfosalicylate in an aqueous system—potentiometric, H NMR, and TRLIFS studies

The complex formation between several trivalent lanthanides (Ln) and 5-sulfosalicylate, (SSA)³⁻, was investigated by potentiometry, ¹H NMR, and time resolved laser-induced fluorescence spectroscopy (TRLIFS). The potentiometric data were used to deduce the stoichiometry and equilibrium constants for the reactions pLn³⁺ + rL ? Ln_pH_−qL_r + qH⁺ at 298 K in an ionic medium with a constant concentration of Na⁺ equal to 1.00 M. Note that “L” denotes the SSA ligand where all protons are dissociated. Two mononuclear chelating complexes, LnL(aq) and , were identified. Their stability constants obtained by least-squares refinement of the potentiometric data agree well with previously published information. In addition, two additional dinuclear complexes, and , which have very different ¹H NMR and fluorescence characteristics, were identified by least-squares refinement in the −log[H⁺] range of 6.0-10.0. ¹H NMR spectra from the ligand in the complex showed separate peaks having two different rates of exchange with free ligand in the bulk solution besides a signal from the free and carboxylate-coordinated ligands. This indicates that the dinuclear complex, , consists of two different types of chelating ligands: μ-{OR}-type chelating ligands between metals to form the {Ln₂L₂}-type core structure and the bidentate ligands outside the {Ln₂L₂}-type core. This core structure is different from the An(IV)-SSA case (An(IV): tetravalent actinide), in which hydroxides play the role of forming the {An₂(OH)₂}-type core structure. TRLIFS measurement gave further information about the dynamics and molecular structures of the complexes.     

Re(I)(tricarbonyl) complexes with the 2-(2-pyridyl)-N-methyl-benzimidazole, 2-(2-pyridyl)benzoxazole and 2-(2-pyridyl)benzothiazole ligands - syntheses, structures, electrochemical and spectroscopic studies

The reactions of Re(CO)₅Cl with the chelating ligands 2-(2-pyridyl)-N-methylbenzimidazole, 2-(2-pyridyl)benzoxazole and 2-(2-pyridyl)benzothiazole afforded neutral fac-Re(CO)₃(L)Cl and ionic complexes with structures confirmed by means of X-ray measurements. UV-vis absorption and emission properties have been studied at room and 77 K temperatures in order to determine the nature of the lowest electronically excited states. Electrochemical behaviour of the investigated fac-Re(CO)₃(L)Cl and complexes has been studied using cyclic and square-wave voltammetry. Preliminary results from the electrogenerated chemiluminescence studies of the ionic and the neutral fac-Re(CO)₃(MPBI)Cl complexes are briefly presented.     

Ruthenium(II) complexes possessing the η-p-cymene ligand

Complexes possessing a soft donor η⁶-arene and hard donor acetylacetonate ligand, [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1) (OTf = trifluoromethanesulfonate; acac = acetylacetonate) and {Ar′ = 3,5-(CF₃)-C₆H₃}, were prepared and fully characterized. The lability of the μ-CH linkage for complex 1 and the THF ligand of 2 allow access to the unsaturated cation [(η⁶-p-cymene)Ru(κ²-O,O-acac)]⁺. The reaction of with KTp {Tp = hydridotris(pyrazolyl)borate} produces . The azide complex forms upon reaction of with N₃Ar (Ar = p-tolyl), and reaction of with CHCl₃ at 100 °C yields the chloride-bridged binuclear complex . The details of solid-state structures of [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1), and are disclosed.     

Half-sandwich Mo(III) complexes with asymmetric diazadiene ligands

The asymmetric 1,4-diazadiene ligands R^∗NCHCHNR^∗ [R^∗ = (S)-CH(CH₃)Ph], , and 2,2′-bis(4-ethyloxazoline), as-ox, have been used to generate half-sandwich Mo^III derivatives by addition to Cp₂Mo₂Cl₄. Ligand affords a mononuclear, paramagnetic 17-electron product, , whereas as-ox leads to the isolation of a dinuclear compound where only one molecule of ligand has been added per two Mo atoms, Cp₂Mo₂Cl₄(as-ox). In the presence of free as-ox, this compound coexists with the paramagnetic mononuclear complex in solution. Both products are capable of controlling the radical polymerization of styrene under typical atom transfer radical polymerization (ATRP) conditions. However, the tacticity of the resulting polystyrene does not differ from that given by conventional free radical polymerization.     

Synthesis and characterization of four novel mixed (porphyrinato)(phthalocyaninato) sandwich-type europium(III) complexes with [tetrakis(4-chlorophenyl)porphyrinato] and diversely substituted phthalocyaninato ligands

Four novel mixed (porphyrinato)(phthalocyaninato) rare earth double-deckers Eu^III(TClPP)[Pc(t-BuPhO₂)₄] {H₂TClPP = tetrakis(4-chlorophenyl)porphyrin, H₂[Pc(t-BuPhO₂)₄] = 1,3,10,12(11,13),19,21(20,22),28,30(29,31)-octa-tert-butyl-tetrakis[1,4]benzodioxino[2,3-b:2′,3′-k:2″,3″-t:2?,3?-e₁]phthalocyanine}, HEu^III(TClPP)[Pc(α-OC₄H₉)₈] {H₂[Pc(α-OC₄H₉)₈] = 1,4,8,11,15,18,22,25-octa-butoxy-phthalocyanine}, Eu^III(TClPP)[Pc(MeOPhO)₈]{H₂[Pc(MeOPhO)₈] = 2,3,9,10,16,17,23,24-octakis(4-methoxyphenoxy)phthalocyanine} and Eu^III(TClPP)[Pc(PhS)₈] {H₂[Pc(PhS)₈] = 2,3,9,10,16,17,23,24-octakis(benzenesulfenyl)phthalocyanine} have been prepared for the first time by treating Eu(acac)(TClPP) with corresponding metal-free phthalocyanine in refluxing 1,2,4-trichlorobenzene (TCB). Typical IR marker bands of the monoanion radical , and show strong bands at 1310, 1319, and 1318 cm⁻¹, and are attributed to pyrrole CC stretchings. The TClPP⁻ IR marker band at ca. 1270-1300 cm⁻¹ was not observed for these compounds. These facts indicate that the hole in these double-deckers is mainly localized at the phthalocyanine ring. The marker IR band for phthalocyanine monoanionradical, , appearing at ca. 1312 cm⁻¹ as a medium absorption band was not observed for HEu^III(TClPP)[Pc(α-C₄H₉)₈]. Instead, a significant peak appearing at ca. 1321 cm⁻¹ with weak intensity is assigned to the pyrrole stretching of the phthalocyanine dianion, . This suggests that both the phthalocyanine and porphyrin rings exist as dianions in mixed (porphyrinato)(phthalocyaninato) complex, . The four complexes were characterized by MS, EA, UV-Vis and IR spectra.     

Oxalate, squarate and croconate complexes with bis(2-pyrimidylcarbonyl)amidatecopper(II): synthesis, crystal structures and magnetic properties

The preparation and magnetic properties of three copper(II) compounds of formulae [Cu₂(bpcam)₂(H₂O)₂(C₂O₄)] (1), [Cu₂(bpcam)₂(H₂O)₄(C₄O₄)] · 10 H₂O (2) and Cu₂(bpcam)₂(C₅O₅)(H₂O)₃ (3) [bpcam = bis(2-pyrimidyl)amidate, and are reported. The structures of two of them (1 and 2) have been solved by single crystal X-ray diffraction and consists of centrosymmetric discrete copper(II) dinuclear units bridged by bis-bidentate oxalate (1) and bis-monodentate squarate (2), with the bpcam group acting as a terminal tridentate ligand. Each copper atom in 1 exhibits a distorted elongated octahedral coordination geometry. Three bpcam nitrogen atoms and one oxalate oxygen define the basal plane while the other oxalate oxygen and a water molecule take up the axial positions. Each copper atom in 2 is in an elongated octahedral surrounding with three bpcam nitrogen atoms and one squarate oxygen in the equatorial plane and two water molecules in the axial positions. The intramolecular copper-copper separations are 5.677(1) (1) and 7.819(53) Å (2). Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K show the occurrence of weak ferromagnetic interactions through oxalato (J = +0.75 cm⁻¹) and squarato (J = +1.26 cm⁻¹), the Hamiltonian being defined by . These values are analyzed and discussed in the light of the available magneto-structural data for analogous systems. The quasi-Curie law observed in 3 (θ = −1.15 K) contrasts with the significant antiferromagnetic interaction through bis-chelating croconate in other structurally characterized croconate-bridged copper(II) complexes and rules out the presence of bridging croconate in this compound.     

Crystal structures of [M(NTf2)3(H2O)n] (M = Eu and Yb) and a template effect of linear molecules on the 3D hydrogen bonding network structure of [Eu(NTf2)3(H2O)3]

Lewis acid catalysts [Eu(NTf₂)₃] and [Yb(NTf₂)₃] can be easily crystallized from a p-xylene solution in the presence of carboxylic acids and a small amount of water to give a trihydrate and a pentahydrate, respectively. In the crystallization of [Eu(NTf₂)₃(H₂O)₃], linear molecules such as n-alkanes and n-alkanoic acids act as templates to form crystals belonging to the trigonal space group with a hexagonal cylindrical structure, which is constructed by 3D hydrogen bonding network. On the other hand, [Eu(NTf₂)₃(H₂O)₃] crystallized in the cubic space group P2₁3 in the presence of a bulkier carboxylic acid, cyclohexanecarboxylic acid. In both [Eu(NTf₂)₃(H₂O)₃] crystals, ligands act as bidentate ligands coordinating to the Eu atom through two oxygen atoms. [Yb(NTf₂)₃] crystallized as a pentahydrate in the monoclinic space group P2₁/n, in which ligands coordinated to the Yb atom with only one oxygen atom.     

Structural studies on novel Ru(II)-Binap complexes

The solid-state structures for two complexes, 7 and 8, are reported. Complex 7 was prepared by treating Ru(OAc)₂(Binap) with two equivalents of HBArF in toluene solution, and represents only the second solid-state structure of a Binap complex, in which the Binap is a 6e donor to the Ru(II). The bonding is maintained in solution as shown via ¹³C NMR studies. The unusual cation 8, as an salt, arises from prolonged reaction of Ru(OAc)₂(Binap) with wet HBF₄ (and, subsequently, added HSbF₆) in 1,2-dichloroethane.     

Metallocycle and ring-opening polymerization of silver(I) complexes with 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene ligand

The reaction of 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag₂(bib)₂](NO₃)₂ · 2H₂O, in which bib ligand displayed in cis configuration. When the additional competing ligands/counterions, such as oxlate salt, 1,2-diaminoethene (en), 1,3-diaminopropane (pn), and were introduced, respectively, to the above-mentioned reaction solution, ring-open polymerization of sliver(I) complexes {[Ag(bib)]NO₃ · H₂O}_n (1), {[Ag(bib)₂]X}_n ( (2), (3)), {[Ag₂(bib)₂(NO₂)](NO₂) · 19/8H₂O}_n (4) and {[Ag₂(bib)₂](V₄O₁₂)_0.5 · 3H₂O · 2MeCN}_n (5) were generated. In compounds 1, 4 and 5, bib ligand adopts trans configuration and twists around the Ag-Ag axis, giving rise to single-stranded helical structure with short adjacent Ag?Ag distances of 3.56, 3.56, 3.50 and 3.63 Å, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag₂(bib)₂]²⁺, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag?Ag distances of 8.52 Å in 2 and 8.61 Å in 3 along with the strong intracyclicπ-π interactions between phenyl groups. Cis and trans configurations of bib coexist in solution and crystallize in complexes 1 and 2 in the solid state in the presence of en or pn. The solution of 1 and 2 can be converted into 3 via the addition of the bulky counter anion or into 4 through introduction of the competing ligand/conuterion .     

Conformational isomerism and hydrogen-bonded motifs of anion assisted supramolecular self-assemblies using Cu/Co salts and pyridine-4-acetamide

Six novel metal-organic complex assemblies constructed from a conformation-flexible ligand - pyridine-4-acetamide (PAT) and inorganic Cu^II and Co^II salts have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Crystal structure analysis reveals five types of architectures by variation of metal salts. In {[Cu(PAT)₂Cl₂]}_n (1) and {[Co(PAT)₂Cl₂]}_n (3), PAT ligands bridge metal centers to form one-dimensional chains. The chains are extended to three dimensions with the aid of two types of hydrogen bonded motifs () and (12)). {[Cu(PAT)₂(NO₃)](NO₃)(THF)}_n (5) which exhibits two-dimensional coordinating layers forms open channels filled with solvent molecules. In [Cu(PAT)₂Cl₂] (2), [Co(PAT)₂Cl₂] (4) and [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6), PAT is observed as a monofunctional ligand. Complex 2 forms one-dimensional hydrogen bonded chains. Crystal structure of complex 4 has a two-dimensional infinite hydrogen-bonded network with and motifs formed by complementary amide-amide hydrogen bonds. [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6) crystallizes in centrosymmetric I4₁/a space group. Complex 6 forms chiral channels which are filled with twisted solvent helices and anion helices. Within each channel the solvent helix and the anion helix have the same handedness; and adjacent channels have opposite handedness. Complexes 1, 2 and complexes 3, 4 illustrate examples of conformational supramolecular isomerism in {[Cu(PAT)₂Cl₂]}_∞ and {[Co(PAT)₂Cl₂]}_∞, respectively. In these complexes, changes of PAT conformations and coordination geometry of metal center induced the structural versatility.     

Kinetics and mechanism of the oxidation of oxalic acid by tetrachloroaurate(III) ion

The oxidation of oxalic acid by tetrachloroaurate(III) ion in 0.005 ? [HClO₄] ? 0.5 mol dm⁻³ is first order in and a fractional order in [oxalic acid], the reactive entities being AuCl₃(OH)⁻ and ions. The pseudo first-order rate, k_obs, with respect to [Au(III)], is retarded by increasing [H⁺] and [Cl⁻]. The retardation by H⁺ ion is caused by the dissociation equilibrium . A mechanism in which a substitution complex, is formed from AuCl₃(OH)⁻ and ions prior to its rate limiting disproportionation into products is suggested. The rate limiting constant, k, has been evaluated and its activation parameters are reported. The equilibrium constant K₁ for the formation of the substitution complex and its thermodynamic parameters are also reported.     

On the mechanism of formation and spectral properties of radical anions generated by the reduction of -[Re(CO)3(5-nitro-1,10-phenanthroline)] and -[Re(CO)3(3,4,7,8-tetramethyl-1,10-phenanthroline)] pendants in poly-4-vinylpyridine polymers

The electrochemical reduction in aprotic media of -[Re^I(CO)₃L]⁺ pendants in poly-4-vinylpyridine polymers is compared to that of [Re^I(CO)₃L]⁺ complexes (L = 5-nitro-1,10-phenanthroline and 3,4,7,8-tetramethyl-1,10-phenanthroline). The UV-Vis absorption spectra of the reduced radical anions of 5-nitro-1,10-phenanthroline (NO₂-phen) and 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) were obtained by spectro-electrochemistry of [Re^I(CO)₃(NO₂-phen)(CH₃CN)]⁺ and [Re^I(CO)₃(tmphen)(CH₃CN)]⁺, respectively. Similar spectra were obtained for the radical anions -phen and tmphen⁻ after pulse radiolysis experiments with -[Re^I(CO)₃L]⁺-containing polymers. The analysis of the time-resolved difference spectra was performed using “multivariate curve resolution” (MCR) techniques. Unlike , CH₂OH radicals were unable to reduce tmphen ligands. The reaction of and/or CH₂OH with -[Re^I(CO)₃(NO₂-phen)]⁺-containing polymers generates -[Re^I(CO)₃(-phen)] pendants which after disproportionation give rise to products with λ_max = 380 nm. The kinetic behavior of -[Re^I(CO)₃(-phen)] pendants under different experimental conditions is discussed.     

Syntheses, structures and magnetic properties of zig-zag chains of transition metals with O-P-O bridges

A novel series of linear chain coordination polymers, [NH₄][M^II(H₂PO₂)₃(H₂O)] where M = Mn, Co, Ni, has been obtained by the reaction of divalent metals salts with ammonium pyrophosphite, [NH₄][H₂PO₂], in a methanol-water mixture. They crystallise in the monoclinic P2₁/n cell and contain polar chains aligned with opposing polarity. Both bridging and terminal monodentate coordination modes are exhibited by the . Two types of hydrogen-bond between a coordinated water and a monodentate connect the chains into a 3D-network. The compounds have been further characterised by IR and UV-Vis spectroscopies, TGA, and their magnetic properties measured. All three compounds exhibit weak antiferromagnetic nearest neighbour interaction. A similar study on the known [Fe^III(H₂PO₂)₃] is also reported. Its magnetic susceptibility fits a model for a 1D-antiferromagnet with 2 J/k of 1.20(1) K and g of 2.019(2).     

Syntheses, characterization and luminescence of Pt-M (M = Re, Ru, Gd) heteronuclear complexes with 5-ethynyl-2,2′-bipyridine

Incorporation of diplatinum component [Pt₂(μ-dppm)₂(CCbpy)₄] (1, dppm = Ph₂PCH₂PPh₂, CCbpy = 2,2′-dipyridyl-5-acetylide) with Re(CO)₅Cl, Ru(bpy)₂Cl₂ (bpy = 2,2′-bipyridine) and Gd(hfac)₃(H₂O)₂ (Hhfac = hexafluoroacetylacetone) via 2,2′-dipyridyl chelating induced isolation of (2), (3), and (4) complexes, respectively. The structures of 2 and 4 were determined by X-ray single crystal diffraction. Intense low-energy absorptions occur in the range 360-510 nm originating from metal-to-ligand charge transfer (MLCT) transitions. These compounds display photoluminescence in both solid states and dichloromethane at room temperature with emissive lifetimes in the range of microseconds.     

3D coordination polymer of copper (II)-potassium (I): Crystal structure and thermal decomposition kinetics

A new heterometallacrown coordination polymer [K₂Cu(NPA)₂(H₂O)₄]_n (where H₂NPA = 3-nitro-phthalic acid) has been synthesized and it’s crystal structure has been elucidated. In the complex, the o-phthalate group coordinates to metal atoms behaving as both tetradentate and heptadentate coordination, the modes of which have been found for the first time. The thermal behaviors of this complex and the thermal decomposition kinetics have been studied. Kinetic analysis shows that the decomposition of title complex in the main range acts as two separate transitions with the first one being a double-step following reaction, , and the second being a three-step following reaction of t:f,f, . The kinetic parameters of these processes were also obtained.     

Investigation into the reaction of (t-BuC5H4)2Nb(η-Te2)H with CH3Li: Hydride abstraction versus telluride methylation

The reaction of (Cp′ = t-BuC₅H₄) with CH₃Li in THF was examined by variable temperature ¹H NMR, ESR and mass spectroscopic means. From these methods it is evident that the diamagnetic compounds and as well as the paramagnetic compound form simultaneously. In the subsequent reaction of the intermediate solution with [Co₂(CO)₈] compound 4 was consumed and the compound (5) formed in good yield. Complex 5 was characterized by IR and variable temperature ¹H NMR spectroscopies. Electrochemical two-electron reduction of 1 leads, in a quasi-reversible process, to products that are not stable in solution.     

Magnetic properties and circular dichroism of 1D chains built from chiral mononuclear and non-chiral trinuclear Cu(II) complexes with α-aminocarboxylates

Coordination polymers Cu(l-Pro)(ClO₄)(H₂O)₂ (1) and Cu₃(Gly)₄(H₂O)₂(NO₃)₂ (2) were synthesized and characterized structurally. Compound 1 possesses the structure of 1D chain, where Cu(II) ions are linked by carboxyl-group in syn-anti conformation in equatorial-equatorial mode. Compound 2 is polymeric chain, consisting from trinuclear blocks Cu₃(Gly)₄(H₂O)₂²⁺. In each of these units Cu(II) ions are linked by carboxyl-group in the same way as in 1, while trinuclear units Cu₃(Gly)₄(H₂O)₂²⁺ are linked by NO₃⁻ ions, acting as the bridges between Cu(II) ions of neighboring trinuclear units. Circular dichroism properties of 1 were studied in solid state and solution. Magnetic measurements revealed that there were ferromagnetic exchange interactions between Cu(II) ions in 1 (J = +1.22(1) cm^-1 for Hamiltonian ) and 2 (J = +1.17(2) cm^-1 for Hamiltonian ).