Synthesis and properties of potassium oxotriperoxovanadate(V) K3[VO(O-O)3]

The conditions of synthesis of potassium oxotriperoxovanadate(V) K₃[VO(O-O)₃] were developed, and the compound was isolated pure. Its physicochemical characteristics, including X-ray diffraction pattern, thermogravimetric data, and IR spectrum, are presented.     

Lithium dioxobis[trioxoiodato(V)]vanadate,Li[VO2(IO3)2]

The title compound represents a new structure type, in which distorted VO₆ octa­hedra are bridged by iodate groups to form infinite two‐dimensional [VO₂(IO₃)₂]⁻ layers that are separated by octa­hedrally coordinated Li⁺ cations.     

Coordination behavior of chromone Schiff bases towards the [ReVO]3+ and [ReI(CO)3]+ cores

Herein, we describe the coordination behavior of chromone Schiff bases towards [Re^VO]³⁺ and [Re^I(CO)₃]⁺. The reaction between 2-(2-thiolphenyliminomethyl)-4H-chromen-4-one (Htch) and [Re(CO)₅Cl] led to fac-[Re(CO)₃(bsch)Cl] (1) (bsch = 2-benzothiazole-4H-chromen-4-one). The square pyramidal [ReO(Hns)] (2) {H₂ns=bis-[(2-phenylthiolate)iminomethyl]-methyl-1-(2-hydroxyphenyl)prop-2-en-1-one} and octahedral [ReO(OCH₃)(PPh₃)(Huch)] (3) complexes were isolated from reactions of trans-[Re^VOBr₃(PPh₃)₂] with Htch and H₃uch [(5Z)-5-((4-hydroxy-2-methoxy-2H-chromen-3-yl)methyleneamino)-6-amino-1,3-dimethylpyrimidine-2,4(1H, 3H)-dione], respectively. The chromone Schiff bases and their metal complexes were fully characterized via NMR-, IR- and UV–Vis spectroscopy, single crystal XRD analysis and conductivity measurements. In addition, DFT studies were conducted to compare selected optimized and experimental parameters of the complexes.     

Synthesis and characterisation of triselenocarbonate [CSe3]2- complexes

[Pt(CSe3)(PR3)2] (PR3= PMe3, PMe2Ph, PPh3, P(p-tol)3, 1/2 dppp, 1/2 dppf) were all obtained by the reaction of the appropriate metal halide containing complex with carbon diselenide in liquid ammonia. Similar reaction with [Pt(Cl)2(dppe)] gave a mixture of triselenocarbonate and perselenocarbonate complexes. [{Pt(mu-CSe3)(PEt3)}4] was formed when the analogous procedure was carried out using [Pt(Cl)2(PEt3)2]. Further reaction of [Pt(CSe3)(PMe2Ph)2] with [M(CO)6] (M = Cr, W, Mo) yielded bimetallic species of the type [Pt(PMe2Ph)2(CSe3)M(CO)5] (M = Cr, W, Mo). The dimeric triselenocarbonate complexes [M{(CSe3)(eta5-C5Me5)}2] (M = Rh, Ir) and [{M(CSe3)(eta6-p-MeC6H4(i)Pr)}2] (M = Ru, Os) have been synthesised from the appropriate transition metal dimer starting material. The triselenocarbonate ligand is Se,Se' bidentate in the monomeric complexes. In the tetrameric structure the exocyclic selenium atoms link the four platinum centres together.     

Synthesis and crystal structures of the dioxovanadium complexes [VO2L1] and [VO2L2]2

Two new oxovanadium complexes, [VO₂L¹] (I) and [VO₂L²]₂ (II), where L¹ and L² are the deprotonated forms of 4-bromo-2-[(2-diethylaminoethylimino)methyl]phenol (HL¹) and 4-bromo-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL²), respectively, have been synthesized and characterized by IR spectra and single crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/n, a = 14.300(3), b = 7.010(2), c = 15.460(2) ?, ?? = 107.401(2)°, V = 1478.7(5) ?³, Z = 4. The crystal of II is monoclinic: space group P2₁/c, a = 7.270(2), b = 15.373(3), c = 11.893(3) ?, ?? = 99.302(2)°, V = 1311.8(5) ?³, Z = 2. Complex I is a mononuclear dioxovanadium(IV) complex. Complex II is a centrosymmetric dinuclear dioxovanadium(V) complex with a V...V distance of 3.117(2) ?. The Vatom in I is in a distorted square-pyramidal coordination, and that in II is in an octahedral coordination. The difference in the structures of the complexes is largely induced by the hydrogen bonds during the self-assembly process.     

The Vanadium(V) Oxoazides [VO(N3)3], [(bipy)VO(N3)3], and [VO(N3)5]2−

Vanadium(V) oxoazide [VO(N₃)₃] was prepared through a fluoride–azide exchange reaction between [VOF₃] and Me₃SiN₃ in acetonitrile solution. When the highly impact‐ and friction‐sensitive compound [VO(N₃)₃] was reacted with 2,2′‐bipyridine, the adduct [(bipy)VO(N₃)₃] was isolated. The reaction of [VO(N₃)₃] with [PPh₄]N₃ resulted in the formation and isolation of the salt [PPh₄]₂[VO(N₃)₅]. The adduct [(bipy)VO(N₃)₃] and the salt [PPh₄]₂₃[VO(N₃)₅] were characterized by vibrational spectroscopy and single‐crystal X‐ray structure determination, making these compounds the first structurally characterized vanadium(V) azides.     

Darstellung,Ramanspektren und Kristallstrukturen von V2O3(SO4)2, K[VO(SO4)2] und NH4[VO(SO4)2]

Preparation, Raman Spectra, and Crystal Structures of V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] The oxo-sulfato-vanadates(V) V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] have been prepared as crystals suitable for X-ray structure determination. In all structures sulfate acts as an unidentate ligand only toward a single vanadium atom. The structure of V₂O₃(SO₄)₂ consists of a threedimensional network of pairs of cornershared VO₆ octahedra with one terminal oxygen atom each, and SO₄ tetrahedra. All oxygen atoms of the sulfate ions are coordinated. NH₄[VO(SO₄)₂] and K[VO(SO₄)₂] are isostructural. VO₆ octahedra with one terminal oxygen atom and pairs of sulfate tetrahedra form infinite chains by corner sharing. The chains are weakly interlinked to layers. The sulfate ions are distorted towards planar SO₃ molecules and single oxygen atoms attached to vanadium. This structural detail gives an explanation for the mechanism of the reversible reaction K[VO(SO₄)₂] ? K[VO₂(SO₄)] + SO₃ at 400°C. Raman spectra of the compounds have been recorded and interpreted with respect to their structures. Crystal data: V₂O₃(SO₄)₂, monoclinic, space group P2₁/a, a = 947.2(4), b = 891.3(3), c? 989.1(4) pm, β = 104.56(3)°, Z = 4, 878 unique data, R(R_w) = 0.039(0,033); K[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(2), b = 869.6(9), c = 1 627(1)pm, Z = 4, 642 unique data, R(R_w) = 0,11(0,10); NH₄[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(1), b = 870.0(2), c = 1 676.7(4)pm, Z = 4, 768 unique data, R(R_w) = 0.088(0.083).     

Synthesis, chemistry and structures of complexes of the dioxovanadium(V) halides VO2F and VO2Cl

[VO2F(L-L)] (L-L = 2,2'-bipyridyl, 1,10-phenanthroline, Me2N(CH2)2NMe2) and [VO2F(py)2] (py = pyridine) have been prepared from the corresponding [VOF3(L-L)] or [VOF3(py)2] and O(SiMe3)2 in MeCN solution. VO2F (itself made from VOF3 and O(SiMe3)2 in MeCN) forms [Me4N][VO2F2] with [Me4N]F, but does not react with neutral N- or O-donor ligands. VO2Cl, prepared from VOCl3 and ozone, reacts with 2,2'-bipyridyl or 1,10-phenanthroline to form [VO2Cl(L-L)], with pyridine or pyridine-N-oxide (L) to produce [VO2Cl(L)2], and with OPPh3 or OAsPh3 (L') gives [VO2Cl(L')]. A second product from the OPPh3 system is the ionic [VO2(OPPh3)3][VO2Cl2] containing a trigonal bipyramidal cation. Neither VO2F nor VO2Cl form isolable complexes with MeCN, thf or MeO(CH2)2OMe, and both are reduced by P-, As-, S- or Se-donor ligands. [Ph4As][VO2X2] (X = F or Cl) react with 2,2'-bipyridyl to form [VO2X(2,2'-bipyridyl)], but similar reactions with weaker O-donor ligands fail. The complexes have been characterised by IR, multinuclear NMR (1H, 19F, 51V or 31P) and UV-visible spectroscopy. X-ray crystal structures are reported for [VO2F(py)2], [VO2Cl(L)2] (L = py or pyNO) and [VO2(OPPh3)3][VO2Cl2].     

Synthesis, characterization, reactivity, and catalytic potential of model vanadium(IV, V) complexes with benzimidazole-derived ONN donor ligands

Reaction between [VO(acac)(2)] and the ONN donor Schiff base Hsal-ambmz (I) (Hsal-ambmz = Schiff base obtained by the condensation of salicylaldehyde and 2-aminomethylbenzimidazole) resulted in the formation of the complexes [V(IV)O(acac)(sal-ambmz)] (1), [V(V)O(2)(acac-ambmz)] (2) (Hacac-ambmz = Schiff base derived from acetylacetone and 2-aminomethylbenzimidazole), and the known complex [V(IV)O(sal-phen)] (3) (H(2)sal-phen = Schiff base derived from salicylaldehyde and o-phenylenediamine). Similarly, [V(IV)O(acac)(sal-aebmz)] (7) has been isolated from the reaction with Hsal-aebmz (II) (Hsal-aebmz derived from salicylaldehyde and 2-aminoethylbenzimidazole). Aerial oxidation of the methanolic solutions/suspensions of 1 and 7 yielded the dioxovanadium(V) complexes [V(V)O(2)(sal-ambmz)] (4) and [V(V)O(2)(sal-aebmz)] (8), respectively. Reaction of VOSO(4) with II gave [{V(IV)O(sal-aebmz)}(2)SO(4)] (9) and [V(IV)O(sal-aebmz)(2)] (10), along with 3 and 8. Under similar reaction conditions, I gave only [{V(IV)O(sal-ambmz)}(2)SO(4)] (5) and 3 as major products. Treatment of 1 and 7 with benzohydroxamic acid (Hbha) yielded the mixed-chelate complexes [V(V)O(bha)(sal-ambmz)] (6) and [V(V)O(bha)(sal-aebmz)] (11). The crystal and molecular structures of 2, 3.1/2DMF, 7.1/4H(2)O, 8, 9.2H(2)O, 10, and 11 have been determined, confirming the ONN binding mode of the ligands. In complex 10, one of the ligands is coordinated through the azomethine nitrogen and phenolate oxygen only, leaving the benzimidazole group free. In the dinuclear complex 9, bridging functions are the phenolate oxygens from both of the ligands and two oxygens of the sulfato group. The unstable oxoperoxovanadium(V) complex [V(V)O(O(2))(sal-aebmz)] (12) has been prepared by treatment of 7 with aqueous H(2)O(2). Acidification of methanolic solutions of 7 and 10 lead to (reversible) protonation of the bemzimidazole, while 8 was converted to an oxo-hydroxo species. Complexes 2, 4, and 8 catalyze the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide and methyl phenyl sulfone, a reaction mimicking the sulfideperoxidase activity of vanadate-dependent haloperoxidases. These complexes are also catalytically active in the oxidation of styrene to styrene oxide, benzaldehyde, benzoic acid, and 1-phenylethane-1,2-diol.     

Synthesis of mixed-ligand complexes of VO2+ and VO3+ incorporating hydrazone, 1,10-phenanthroline and 8-hydroxyquinoline

2-Aminobenzoylhydrazide (abh) reacts with equimolar amounts of either [V^IVO(acac)₂] or [V^IVO(bzac)₂] (where acac^? and bzac^? are the monoanionic forms of acetylacetone (Hacac) and benzoylacetone (Hbzac), respectively) in the presence of equimolar amounts of 1,10-phenanthroline (phen) to form the octahedral mixed-ligand complexes [V^IVO(L¹)(phen)] (1) and [V^IVO(L²)(phen)] (2), where (L¹)^2? and (L²)^2? are the dianionic forms of the 2-aminobenzoylhydrazone of acetylacetone (H₂L¹) and benzoylacetone (H₂L²). Upon substituting phen by 8-hydroxyquinoline (Hhq), pentavalent [V^VO(L¹)(hq)] (3) and [V^VO(L²)(hq)] (4) complexes were instead obtained. In the crystal structures of 3 and 4, the hydrazone ligands coordinate to the vanadium center through the enolic-O, one imine-N and amide-O in a mer geometry. The amine and the second imine nitrogen form intramolecular hydrogen bonds. Complexes 1 and 2 display quasi-reversible one-electron oxidation peaks near +0.60 V, while the pentavalent 3 and 4 exhibit quasi-reversible one-electron reduction peaks near ?0.18 V versus Ag/AgCl in CH₂Cl₂ solution. EPR spectroscopic studies on 1 and 2 suggest that the unpaired electron is present in the d_xy orbital. DFT studies for 3 indicate that the d_xy orbital of vanadium is the main contributor to the LUMO.     

Synthesis,structures and magnetic properties of nickel bis (dithiolene) complexes with [Fe(qsal)2]+

Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)₂][Ni(dddt)₂] · CH₃CN · CH₃OH (1) and [Fe(qsal)₂][Ni(pddt)₂] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis spectra are dominated by [Ni(L)₂]^? (1, L = dddt; 2, L = pddt). Magnetic studies show antiferromagnetic interaction in 1 from intermolecular S···S contacts and π–π stacking interactions, while the antiferromagnetic interaction in 2 is very weak.     

Synthesis,characterization, photocleavage,antimicrobial activity and DNA binding of [Co(bpy)2MHPIP]3+, [Co(dmb)2MHPIP]3+, and [Co(phen)2MHPIP]3+ complexes

4-Methyl-2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline) (MHPIP) and its complexes [Co(bpy)₂MHPIP]³⁺ (1) (bpy = 2,2′-bipyridine), [Co(dmb)₂MHPIP]³⁺ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine), and [Co(phen)₂MHPIP]³⁺ (3) (phen = 1,10-phenanthroline) have been synthesized and characterized by UV/VIS, IR, EA, ¹H, ¹³C-NMR, and mass spectra. The binding of the three complexes with calf-thymus-DNA (CT-DNA) has been investigated by absorption and emission spectroscopy, DNA-melting techniques, viscosity measurements, and DNA cleavage assay. The spectroscopic data and viscosity results indicate that these complexes bind to CT-DNA via an intercalative mode. The complexes also promote photocleavage of plasmid pBR322 DNA and were screened for antimicrobial activity.     

Synthesis,structural characterization and catalytic potential of oxidovanadium(IV) and dioxidovanadium(V) complexes with thiazole-derived NNN-donor ligand

Reaction between the tridentate NNN donor ligand, (E)-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)benzo[d]thiazole (HL), and V₂O₅ in ethanol gave a new vanadium(V) complex, [VO₂L] (1), while the similar reaction by using [V^IVO(acac)₂] as the metal source gave two different types of crystals related to compounds [VO₂L] (1) and [V^IVO(acac)L] (2). The molecular structures of the complexes were determined by single-crystal X-ray diffraction and spectroscopic characterization was carried out by means of FT-IR, UV–vis and NMR experiments as well as elemental analysis. The oxidovanadium(IV) and dioxidovanadium(V) species were used as catalyst precursors for olefin oxidation in the presence of hydrogen peroxide (H₂O₂) as an oxidant. Under similar experimental conditions, the presence of 1 resulted in higher oxidation conversion than 2.     

Oxorhenium(V) and oxotechnetium(V) [NN][S]3 complexes of 2-phenylbenzothiazole derivatives

The reaction of 2-(2'-pyridyl)benzothiazole, [NN], with the ReO(V)(3+) and TcO(V)(3+) cores in the presence of thiophenols, [S] (RC(6)H(4)SH, R = H, 4-CH(3), 4-OCH(3)), as coligands led to the isolation of hexacoordinated complexes of the MO[NN][S](3) type (M = Re, Tc). In all cases, two geometric mer isomers were formed, as evidenced by NMR spectroscopy and confirmed by X-ray crystallography. In both isomers, the coordination geometry about the metal ion is a distorted octahedral defined by the two nitrogen atoms of the bidentate ligand, the three sulfur atoms of the monodentate thiols, and the oxygen atom of the oxo group. The apical positions of the octahedron are occupied by the oxygen of the oxo group and, in one of the isomers, the nitrogen of the pyridyl moiety of 2-(2'-pyridyl)benzothiazole, while, in the second isomer, the imine nitrogen of 2-(2'-pyridyl)benzothiazole. The complexes are stable, neutral, and lipophilic. Complete (1)H and (13)C NMR assignments are reported for all complexes. The synthetic reaction was also successfully transferred at the technetium-99m tracer level by ligand exchange reaction using (99m)Tc-glucoheptonate as precursor in the presence of 2-(2'-pyridyl)benzothiazole and 4-CH(3)C(6)H(4)SH. The structure of the technetium-99m complex was established by high-performance liquid chromatographic comparison with the analogous oxotechnetium and oxorhenium complexes. The 2-(2'-pyridyl)benzothiazole ligand serves as a preliminary model for 2-(4-aminophenyl)benzothiazole, which possesses interesting properties for the development of technetium and rhenium radiopharmaceuticals for tumor imaging and/or radiotherapy as well as in vivo diagnosis of Alzheimer's disease.     

Ein neues Orthovanadat(V): Cs2Na[VO4]

A New Orthovanadate (V): Cs₂Na[VO₄] Colourless single-crystals of Cs₂Na[VO₄] resulted by heating intimate mixtures of CsO_0.52, NaO_0.52 and V₂O₅ (Cs: Na: V = 2.2:1.1:1.0) in tightly closed Ni-tubes. The crystal structure was determined (four-circle diffractometer data), 1341 I_o(hkl), R = 6.23%, R_w = 4.23%, parameters see text. The new orthovanadate(V) crystallizes monoclinic (space group P2₁/m) with a = 839.9(1), b = 624.7(1), c = 614.8(1) pm, β = 92.66(1)° (Guinier-Simon powder data), Z = 2. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, are discussed.     

Calix[4]arene rhenium(V) complexes as potential radiopharmaceuticals

The calix[4]arene platform was used for the syntheses of novel rhenium(V) complexes, that may have potential applications as radiopharmaceuticals. The reaction of ReO(PPh3)2Cl3 with tetradentate N2O2-calix[4]arene ligand 8 in ethanol gave the novel mixed-ligand rhenium complex 9 with the structure ReO(N2O2-calix)OEt. The configuration was elucidated by using a number of 1H NMR techniques. In 9, the ethoxy ligand could be easily and quantitatively exchanged for another monodentate ligand to give complex 12. Tetradentate N2S2-calix[4]arene ligand 15 formed the rhenium complex 16 either via reaction with ReO(PPh3)2Cl3 in an organic solvent or by reaction with rhenium gluconate in an aqueous solution. Complex 16 showed good stability in phosphate-buffered saline solution (37 degrees C, 5 d). The crystal structures of a mono- and a bimetallic complex were determined. The bimetallic N2O2-calixarene complex dimer 11 crystallized in the monoclinic space group C2/c, with a = 38.963(5) A, b = 23.140(6) A, c = 27.382(6) A, beta = 128.456(10) degrees, V = 19,333(7) A3, Z = 8, and final R = 0.0519. The monometallic N2S2 model complex 17 crystallized in the monoclinic space group Cc, with a = 15.715(2) A, b = 12.045(2) A, c = 20.022(3) A, beta = 94.863(12) degrees, V = 3776.3(10) A3, Z = 4, and final R = 0.0342.     

Synthesis, characterization, and glutathionylation of cobalamin model complexes [Co(N4PyCO2Me)Cl]Cl2 and [Co(Bn-CDPy3)Cl]Cl2

Synthetic Co(III) complexes containing N5 donor sets undergo glutathionylation to generate biomimetic species of glutathionylcobalamin (GSCbl), an important form of cobalamin (Cbl) found in nature. For this study, a new Co(III) complex was synthesized derived from the polypyridyl pentadentate N5 ligand N4PyCO(2)Me (1). The compound [Co(N4PyCO(2)Me)Cl]Cl(2) (3) was characterized by X-ray crystallography, UV-vis, IR, (1)H NMR, and (13)C NMR spectroscopies and mass spectrometry (HRMS). Reaction of 3 with glutathione (GSH) in H(2)O generates the biomimetic species [Co(N4PyCO(2)Me)(SG)](2+) (5), which was generated in situ and characterized by UV-vis and (1)H NMR spectroscopies and HRMS. (1)H NMR and UV-vis spectroscopic data are consistent with ligation of the cysteine thiolate of GSH to the Co(III) center of 5, as occurs in GSCbl. Kinetic analysis indicated that the substitution of chloride by GS(-) occurs by a second-order process [k(1) = (10.1 ± 0.7) × 10(-2) M(-1) s(-1)]. The observed equilibrium constant for formation of 5 (K(obs) = 870 ± 50 M(-1)) is about 3 orders of magnitude smaller than for GSCbl. Reaction of the Co(III) complex [Co(Bn-CDPy3)Cl]Cl(2) (4) with GSH generates glutathionylated species [Co(Bn-CDPy3)(GS)](2+) (6), analogous to 5. Glutathionylation of 4 occurs at a similar rate [k(2) = (8.4 ± 0.5) × 10(-2) M(-1) s(-1)], and the observed equilibrium constant (K(obs) = 740 ± 47 M(-1)) is slightly smaller than for 5. Glutathionylation showed a significant pH dependence, where rates increased with pH. Taken together, these results suggest that glutathionylation is a general reaction for Co(III) complexes related to Cbl.