Hydrothermal synthesis of a mixed-valence hexamolybdate cluster: crystal structure of [HN(CH2CH2)3N]2[HMoVMoVI5O19]·[N(CH2CH2)3N]

The hydrothermal reaction of MoO₃, V, Na₂WO₄· 2H₂O, [N(CH₂CH₂)₃N](1,4-diazabicyclo[2.2.2] octane), and H₂O at 160°C for 90h gave dark-brown crystals of [HN(CH₂CH₂)₃N]₂[HMo^VMo^VI ₅O¹⁹]·[N(CH₂CH₂)₃N], (1), in 40% yield. Complex (1) is the first one-electron reduced mixed-valence hexamolybdate to be crystallized and structurally characterized. The crystal structure of (1) consists of discrete [HMo^VMo^VI ₅O₁₉]^2– anions, [HN-(CH₂CH₂)₃N]⁺ cations, and neutral [N(CH₂CH₂)₃N] molecules of crystallization.     

Synthesis and Structural Features of Copper(I) Chloride and Bromide Complexes with the N,N,N′,N′-Tetraallylpiperasinium Cation (L2+) of Compositions L2+[CuCl2]– 2 and L2+[CuBr3]2–

Crystals of the -complex [C₄H₈N₂(C₃H₅)₄]²⁺[CuCl₂]^– ₂ (I) were prepared by ac electrochemical synthesis from copper and N,N,N,N-tetraallylpiperasinium chlorides in alcohol solution. Similar synthesis with the use of the metal and N,N,N,N-tetraallylpiperasinium bromides yielded the complex [C₄H₈N₂(C₃H₅)₄]²⁺[CuBr₃]^2– (II). Structures I and II were studied by X-ray diffraction (DARCh automated single-crystal diffractometer, MoK radiation). Crystals of I are triclinic, space group P1¯, a = 8.650(3) Å, b = 7.572(2) Å, c = 8.095(3) Å, = 100.45(2)°, = 83.91(2)°, = 99.89(2)°, V = 512.1(6) ų, Z = 1. Crystals of II are orthorhombic, space group Pn2₁ a, a = 17.673(3) Å, b = 14.369(6) Å, c = 8.244(2) Å, V = 2093(2) ų, Z = 4. In structure I, the potentially tetradentate N,N,N,N-tetraallylpiperasinium cation uses two centrosymmetric allyl groups for bonding with copper atoms, whose environment is completed to the trigonal-planar coordination with the chlorine atoms. The [C₄H₈N₂(C₃H₅)₄]²⁺[CuCl₂]^– ₂ groups are joined into a three-dimensional framework by weak hydrogen bonds. The inorganic fragment CuCl^– ₂ is partially disordered, which appears as splitting of the positions of the copper atom and one of the chlorine atom. In compound II, the inorganic fragment occurs as an unusual trigonal-planar CuBr^2– ₃ anion; the N,N,N,N-tetraallylpiperasinium cation is not involved in metal coordination.     

Preparation and electrocatalytic performance of Fe–N–C for electroreduction of H2O2

Fe–N–C catalysts were prepared through metal-assisted polymerization method. Effects of carbon treatment, Fe loading, nitrogen source, and calcination temperature on the catalytic performance of the Fe–N–C for H₂O₂ electroreduction were measured by voltammetry and chronoamperometry. The Fe–N–C catalyst shows optimal performance when prepared with pretreated active carbon, 0.2 wt.% Fe, paranitroaniline (4-NA) and one-time calcination. The Fe–N–C catalyst displayed good performance and stability for electroreduction of H₂O₂ in alkaline solution. An Al–H₂O₂ semi-fuel cell was set up with Fe–N–C catalyst as cathode and Al as anode. The cell exhibits an open-circuit voltage of 1.3 V and its power density reached 51.4 mW cm⁻² at 65 mA cm⁻².     

Crystal,molecular and electronic structure of [ReCl2(η2-N2COPh–N′,O)(PPh3)2]

[ReO(OEt)Cl₂(PPh₃)₂] reacts with benzoylhydrazine in the presence of PPh₃ and hydrochloric acid to give [N-benzoylhydrazido(3-)-O,N′]dichlorobis(triphenylphosphine) rhenium(V). The complex has been studied by IR, UV-Vis spectroscopy and X-ray crystallography. The molecular orbital diagram has been calculated with density functional theory (DFT). The spin-allowed singlet-singlet electronic transitions of [ReCl₂(η²–N₂COPh–N′,O)(PPh₃)₂] have been calculated with the time-dependent DFT method, and the UV-Vis spectrum of the title compound has been discussed on this basis.     

N,N′-methylenedipyridinium Pt(II) and Pt(IV) hybrid salts: synthesis, crystal and molecular structures of [(C5H5N)2CH2] · [PtCl4] and [(C5H5N)2CH2] · [PtCl6]

The highly insoluble organic-inorganic hybrid ionic compounds N,N??-methylenedipyridinium tetrachloroplatinate(II) [(C₅H₅N)₂CH₂] · [PtCl₄] and N,N??-methylenedipyridinium hexachloroplatinate(IV) [(C₅H₅N)₂CH₂] · [PtCl₆] were obtained by the treatment of N,N??-methylenedipyridinium dichloride monohydrate [(C₅H₅N)₂CH₂]Cl₂ · H₂O with K₂[PtCl₄] or (NH₄)₂[PtCl₆], respectively, in an aqueous solution. Both complexes were isolated, purified, characterised by elemental analysis, and their molecular structures were confirmed by powder X-ray diffraction. The crystal structure of both compounds consists of separated discrete dications [(C₅H₅N)₂CH₂]²⁺ and anions [PtCl _n ]^2? (n = 4 or 6). As anticipated, the dications formed a butterfly shape consisting of two pyridine rings bound to the methylene group via their N atoms, while the Pt centre had a square planar geometry in [(C₅H₅N)₂CH₂] · [PtCl₄] and an octahedral coordination in [(C₅H₅N)₂CH₂] · [PtCl₆]. Interestingly, both crystal structures are stabilised by intermolecular C-H??Cl non-standard hydrogen bonds, ??-?? ring interactions between two pyridine rings of adjacent dications, and also by Cl-?? interactions.     

The reactivity of cis-platin. Spectroscopic properties of products isolated from the [cis-Pt(NH3)2Cl2–quercetin] and [cis-Pt(NH3)2Cl2–CrVI–quercetin] systems

New coordination compounds: [Pt^IIQ] and [Pt^IV–Cr^IIIQ₂], where Q = quercetin, were isolated from the [Pt(NH₃)₂Cl₂–quercetin] and [Pt(NH₃)₂Cl₂–Cr^VI–quercetin] systems, respectively. Structures are proposed on the basis of i.r., n.m.r. and deconvoluted electronic spectra.     

Kinetics of aquation of trans-dichlorobis(N,N′-dimethylethylenediamine)cobalt(III) ion in water–methanol in water–propan-2-ol media

The complex trans-[Co(dmen)2Cl2]Cl (dmen=N,N-dimethylethylenediamine) has been prepared and characterized by elemental analysis, u.v.-vis. and i.r. spectra. The kinetics of the primary aquation of trans-[Co(dmen)2Cl2] in H2O, H2O–MeOH and H2O–i-PrOH have been examined over a wide range of solvent compositions and temperatures (40–55°C). Plots of rate constants (log k) versus the reciprocal of the dielectric constant of the medium (Ds–1) and Grunwald–Winstein values of the solvent (Y) were found to be non-linear. The variation of enthalpies (H) and entropies (S) of activation with solvent composition has been determined. Plots of H or S versus the mole fraction of each solvent exhibit extrema at x2=ca. 0.16 and 0.27 for MeOH and at x2=ca. 0.03 and 0.14 for i-PrOH. Furthermore, the cycle relating the free energy of activation in H2O to that in H2O–co-solvent shows that the stabilizing influence of the changes in the solvent structure is greater on the emergent five-coordinate cation in the transition state than that on the complex ion in the initial state, with the difference becoming greater as the mole fraction of the co-solvent increases.     

New nickel dithiolene–diselenolene complexes obtained from 3,4-dichloro-1,2,5-thiadiazole: X-ray structure of (Bu4N)2[Ni(C2N2S2.2Se0.8)2]

The new (Bu₄N)₂[Ni(C₂N₂S_2.2Se_0.8)₂] (1) redox active nickel complex with a mixed S_0.6/Se_0.4 occupancy of thiolic sulfurs in the 1,2,5-thiadiazole-3,4-dithiolate (tdas) ligand has been prepared by reacting in situ NiCl₂·6H₂O with the products of the selenation reaction (grey selenium with NaBH₄ in EtOH) of 3,4-dichloro-1,2,5-thiadiazole (TDACl₂). Single crystal X-ray analysis of 1 shows that in the dianion, the central Ni-atom exhibits a square-planar geometry and that bond distances and angles are in agreement with those usually found in this class of complexes, except for the CC distance [1.428(5) Å] which is longer than those generally found in dianionic metal dithiolene or diselenolene complexes. The position at unusually low frequency (1311 cm⁻¹) of the CC stretching vibration in the Raman spectra agrees with structural results. A cyclic voltammetric study on 1 shows that the introduction of the selenium atom in the dithiolene core has the effect to make the dianion more easily to be oxidised than the corresponding tdas derivative. By chemical oxidation with I₂, Bu₄N[Ni(C₂N₂S_2.2Se_0.8)₂] (2) has been obtained. The existence of a monoanion as isolated species in solution and as dimers strongly antiferromagnetically coupled in the solid state is inferred from spectroscopic and EPR results.     

ESR Investigation of Single Crystal of (Bu_4N)_2[Cu/Pd(dmit)_2]

By incorporating (Bu4N)2[Cu(dmit)2] with the diamagnetic host complex (Bu4N)2[Pd (dmit)2], single crystal of (Bu4N)2[Cu/Pd(dmit)2] is obtained. Its ESR spectra of various orientations are recorded. The principal values of g and A tensors and their direction cosines are computed using a least-squares fitting procedure, and based on which the molecular orbital of unpaired electron in [Cu(dmit)2]2- is described. The essence of the two magnetically non-equivalent sites is also revealed.     

Binary group 15 polyazides. structural characterization of [Bi(N3)4]-, [Bi(N3)5]2-, [bipy·Bi(N3)5]2-, [Bi(N3)6]3-, bipy·As(N3)3, bipy·Sb(N3)3, and [(bipy)2·Bi(N3)3]2 and on the lone pair activation of valence electrons

The binary group 15 polyazides As(N(3))(3), Sb(N(3))(3), and Bi(N(3))(3) were stabilized by either anion or donor-acceptor adduct formation. Crystal structures are reported for [Bi(N(3))(4)](-), [Bi(N(3))(5)](2-), [bipy·Bi(N(3))(5)](2-), [Bi(N(3))(6)](3-), bipy·As(N(3))(3), bipy·Sb(N(3))(3), and [(bipy)(2)·Bi(N(3))(3)](2). The lone valence electron pair on the central atom of these pnictogen(+III) compounds can be either sterically active or inactive. The [Bi(N(3))(5)](2-) anion possesses a sterically active lone pair and a monomeric pseudo-octahedral structure with a coordination number of 6, whereas its 2,2'-bipyridine adduct exhibits a pseudo-monocapped trigonal prismatic structure with CN 7 and a sterically inactive lone pair. Because of the high oxidizing power of Bi(+V), reactions aimed at Bi(N(3))(5) and [Bi(N(3))(6)](-) resulted in the reduction to bismuth(+III) compounds by [N(3)](-). The powder X-ray diffraction pattern of Bi(N(3))(3) was recorded at 298 K and is distinct from that calculated for Sb(N(3))(3) from its single-crystal data at 223 K. The [(bipy)(2)·Bi(N(3))(3)](2) adduct is dimeric and derived from two BiN(8) square antiprisms sharing an edge consisting of two μ(1,1)-bridging N(3) ligands and with bismuth having CN 8 and a sterically inactive lone pair. The novel bipy·As(N(3))(3) and bipy·Sb(N(3))(3) adducts are monomeric and isostructural and contain a sterically active lone pair on their central atom and a CN of 6. A systematic quantum chemical analysis of the structures of these polyazides suggests that the M06-2X density functional is well suited for the prediction of the steric activity of lone pairs in main-group chemistry. Furthermore, it was found that the solid-state structures can strongly differ from those of the free gas-phase species or those in solutions and that lone pairs that are sterically inactive in a chemical surrounding can become activated in the free isolated species.     

Kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N′,N′-triacetato]cobalt(II) by N-bromosuccinimide

The kinetics of the oxidation of [N-(2-hydroxyethyl)-ethylene-diamine-N,N,N-triacetato] cobalt(II), [Co^II-(HEDTA)]^–, by N-bromosuccinimide, NBS, have been studied in aqueous solutions and water-methanol solvent mixtures under various conditions. The reaction stoichiometry indicates that one mole of NBS reacts with one mole of [Co^II(HEDTA)]^–. In aqueous solutions the reaction obeys the following rate law:

Structural and spectroscopic characterization of a cationic aquanitrato copper(II) complex with the tetradentate Schiff-base ligand N,N′-bis[1–(2–pyridyl)ethylidene]ethane-1,2–diamine

Cu(NO3)2·3H2O reacts with 1 equiv. of the tetradentate Schiff base N,N-bis[1–(2–pyridyl)ethylidene]ethane-1,2–diamine (LA) in refluxing acetone to yield the [CuLA(ONO2)(H2O)](NO3) complex in ca. 80% yield. The structure of this salt has been determined by single-crystal X-ray crystallography. The copper is six-coordinated with the LA ligand in the equatorial plane and weakly bonded aqua and nitrato ligands above and below this plane. The complex cation is hydrogen-bonded to the nitrate counter-ion. The complex was also characterized by elemental analyses, molar conductivity, room-temperature magnetic susceptibility and spectroscopic (i.r., far-i.r., u.v.–vis, e.s.r.) studies. The data are discussed in terms of the nature of bonding and the known structure.     

Crystal Structure of [Et_4N][Sm(S_2CNEt_2)_4]

The crystal structure of .[Et4N][Sm(S2CNEt2)4] was determined by X-ray diffraction technique. The crystal crystallizes in monoclinic system, space group P21/n with a= 1. 1695(3), b=2.0821(6), c=1.7420(7) nm, β=99. 79(3)°? Z=4, Dc= 1. 39 g/ cm3, μ(Mo/KTσ) = 18. 4 cm-1, F(000) = 1812. The structure was solved by Patterson and Fourier techniques and refined by least-squares method to a final conventional R of 0. 053 for 3116 (Ⅰ> 3σ- (Ⅰ)) reflections. Each asymmetric unit contains two ions [Sm (S2CNEt2)4]-1 and [Et4N] +1, having distance between central atoms N5 and Sm3+ to be 0. 6522 nm. The atom Sm is coordinated by eight sulphur atoms. The Sm-S distance lies in the range of 0. 285-0. 290 nm with an average of 0. 288 nm.     

Redox properties of N2S2-type nickel complexes with aromatic ligands. Crystal structure of [1,2-C6H4(SMe)NH2]2Ni2+(MeCN)2·2ClO4–

The redox properties of six chelate N₂S₂-type Ni(ii) complexes containing two aromatic NS or one N₂S₂ ligands, such as 2-aminothiophenol, 2-aminothiophenolate anion, 2-amidothiophenolate dianion, 2-amidothioanisole, 2,2"-diaminodiphenyl disulfide dianion, and 8-quinolinethiolate anion, were studied by cyclic voltammetry at a glassy-carbon electrode in DMF. Some free ligands were also studied for comparison. A new Ni^II complex with the 2,2"-diamidodiphenyl disulfide dianion was synthesized. The crystal and molecular structures including the square planar Ni(N₂S₂) center with two MeCN molecules as additional axial ligands were established for the Ni^II complex with 2-aminothioanisole [1,2-C₆H₄(SMe)NH₂]₂Ni²⁺(MeCN)₂·2ClO₄ ^– using X-ray diffraction. The most part of the studied compounds are irreversibly oxidized and reduced; however, bis(2-amidothiophenolato)nickel(iv) and bis(8-quinolinethiolato)nickel(ii) show a quasi-reversible behavior in the reduction region. The electrochemically generated anionic form of the 8-thioquinoline complex is rapidly alkylated in the presence of BuⁿBr or BuⁿI to form, probably, the corresponding butylnickel(iii) complex.     

Photoredox-catalyzed C(sp2)–N coupling reactions

Photoredox-catalyzed radical reactions have attracted intense interest from synthetic chemists over the past several years. The photoredox-catalyzed C(sp²)–N coupling reactions, including Ullmann type C–N coupling (C–X/N–H type coupling), redox neutral C–N coupling (C–H/N–X type coupling) and oxidative C–N coupling (C–H/N–H type coupling), have been summarized in this digest.     

Copper-catalyzed intramolecular C–N bond formation reaction of 3-amino-2-(2-bromophenyl)dihydroquinazolinones: synthesis of indazolo[3,2-b]quinazolinones

A copper-catalyzed intramolecular C–N bond formation reaction of 3-amino-2-(2-bromophenyl)dihydroquinazolinones has been developed for the synthesis of indazolo[3,2-b]quinazolinones in moderate to good yields. The structure of the newly synthesized indazolo[3,2-b]quinazolinones was unambiguously confirmed by X-ray single-crystal diffraction analysis. Moreover, a possible mechanism for the formation of indazolo[3,2-b]quinazolinones is discussed.     

Interaction of Phosphorus Iminoilides with Metal Acetates. Crystal and Molecular Structure of Cu[(2-O–)(5-NO2)C6H3N–CH=CH–+PPh3]2 · 2CHCl3

The structure of the Cu[(2-O^–)(5-NO₂)C₆H₃N–CH=CH–⁺PPh₃]₂ complex with the CuN₂O₂ coordination core of distorted square-planar geometry was established by X-ray diffraction analysis. The molecules in the crystal structure of the Cu[(2-O^–)(5-NO₂)C₆H₃N–CH=CH–⁺PPh₃]₂ · 2CHCl₃ solvate are bound via hydrogen bonds of two types, namely, C(sp ²)–H···O and C(sp ³)–H···O.     

Electron paramagnetic resonance of γ-irradiated [(CH3)4N]2ZnF4 and [(CH3)4N]2CdF4 single crystals and vibrational spectra of their unirradiated forms

γ-Irradiated [(CH₃)₄N]₂ZnF₄ and [(CH₃)₄N]₂CdF₄ single crystals were investigated by electron paramagnetic resonance (EPR) and vibrational spectroscopy of their unirradiated forms at ambient temperature. It has been found that both compounds indicate the existence of (CH₃)₃ N˙⁺ radicals. The g factors were found to be isotropic and the hyperfine constant for protons of the methyl groups was measured as 28.9 G for this radical in these substances. Each methyl group rotates around its C_3ν-axis and also rotates around the C_3ν-axis of the (CH₃)₃ N˙⁺ radical. In addition to these motions, the C_3ν-axis of the (CH₃)₃ N˙⁺ radical seems to rotate around the z-axis. These results were compared with the earlier studies in (CH₃)₃ N˙⁺ radical and discussed. The vibrational spectra of these two compounds were discussed in relation to other compounds containing tetramethylammonium salts. The assignments of the observed bands were discussed.