Terminal Coordination Mode Research Articles

Chemistry of a Nitrosyl Ligand κ:η-Bridging a Ditungsten Center: Rearrangement and N-O Bond Cleavage Reactions.

The novel nitrosyl-bridged complex [W2Cp2(μ-PtBu2)(μ-κ:η-NO)(CO)(NO)](BAr4) [Ar = 3,5-C6H3(CF3)2] was prepared in a multistep procedure starting from the hydride [W2Cp2(μ-H)(μ-PtBu2)(CO)4] and involving the new complexes [W2Cp2(μ-PtBu2)(CO)4](BF4), [W2Cp2(μ-PtBu2)(CO)2(NO)2](BAr4), and [W2(μ-κ:η5-C5H4)Cp(μ-PtBu2)(CO)(NO)2] as intermediates, which follow from reactions with HBF4·OEt2, NO, and Me3NO·2H2O, respectively. The nitrosyl-bridged cation easily added chloride upon reaction with [N(PPh3)2]Cl, with concomitant NO rearrangement into the terminal coordination mode, to give [W2ClCp2(μ-PtBu2)(CO)(NO)2], and underwent N–O and W–W bond cleavages upon the addition of CNtBu to give the mononuclear phosphinoimido complex [WCp(NPtBu2)(CNtBu)2](BAr4). Another N–O bond cleavage was induced upon photochemical decarbonylation at 243 K, which gave the oxo- and phosphinito-bridged nitrido complex [W2Cp2(N)(μ-O)(μ-OPtBu2)(NO)](BAr4), likely resulting from a N–O bond cleavage step following decarbonylation.

Copper(I) azide and copper(I) cyanate π-complexes

Electrochemical alternating current synthesis starting from an ethanol solution of CuSO4 · 5H2O and allylamine in the presence of solid sodium azide results in formation of Cu[C3H5NH2]N3. The trigonal-pyramidal coordination environment of both crystallographically independent copper ions consists of the C = C-bond of one allylamine molecule, the NH2-group of another ligand moiety and two N-atoms of the two azide-anions. One N3 − exhibits a terminal coordination mode and the other is a μ3-1,1,3-bridge. The bridging function of both allylamine and azide leads to formation of a complicated 3-D network. An elongation of coordinated C = C-bond and a strong shift of the ν s mode in the Raman spectrum confirm effective Cu–(C = C) bonding. A similar synthetic route starting from a methanol solution of Cu(BF4)2 · 6H2O in the presence of solid potassium cyanate results in formation of Cu[C3H5NH2]NCO. The cyanate-anion is bound to copper through nitrogen. The nitrogen from the allylamine molecule and the C = C-bond from another ligand complete the trigonal-planar environment of copper. The elongation of the coordinated C = C-bond and the shift of ν s (C = C) mode in the Raman spectrum are similar to those in the azide derivative.

Synthesis, X-ray structure, Hirshfeld analysis and DFT studies of Ni(II) complexes with pyridine-type ligands and monoanionic (SCN¯, N3¯ and NO3¯) ligands

The molecular and supramolecular structures of two self-assembled Ni(II) complexes with pyridine-type ligands (34Lut: 3,4-lutidine and 4Pic: 4-picoline) comprising different anions (SCN¯, N3¯and NO3¯) were presented. The dinuclear [Ni(34Lut)3(SCN)2]2(1) complexcomprises a hexa-coordinated Ni(II) with NiN5S coordination environment from three 34Lut, one isothiocyanate, in addition to two SCN¯ connecting the two Ni(II) centres via µ(1,3) coordination mode. Structure of complex 2 has the two complex units [Ni(4Pic)4(N3)2][Ni(4Pic)4(NO3)2], in which the two Ni(II) centers have also hexa-coordinated environments with NiN6 and NiN4O2 coordination spheres. In both units, there are four 4Pic ligand units coordinating the Ni(II) via the pyridine nitrogen atom and two anions in anti-positions to one another. In the first unit, the two azides have terminal coordination mode. In the second unit, there are two monodentate nitrate ions coordinating the Ni(II) ion via one oxygen atom. Molecular packing analysis using Hirshfeld calculations revealed the importance of the S…H (20.4%) and CH…π (25.2%) interactions in 1. For complex 2, the N…H (16.2%) and O…H (20.7%) contacts are the most important in [Ni(4Pic)4(N3)2] and [Ni(4Pic)4(NO3)2] complex units, respectively. The H…H contact percentages are 50.5, 54.6 and 51.3%, respectively which are the most common in all complex units. Using DFT calculations, the charge of the Ni(II) ion decreased to 0.7792, 0.8136 and 0.9377 e in the thiocyanato, azido and nitrato complexes, respectively. Using AIM calculations, the Ni-N, Ni-S and Ni-O bonds showed the characteristics of mainly closed shell interactions.

Synthesis, crystal structures and catalytic activity of oxidovanadium(V) complexes with tridentate ONO aroylhydrazone ligands

Two oxidovanadium(V) complexes, [VOL1(OEt)] (1) and [V2O2(L2)2(OEt)2] (2), where L1 and L2 are the anions of 2-amino-N′-(2-hydroxybenzylidene)benzohydrazide (H2L1) and N′-(2-hydroxybenzylidene)-4-hydroxybenzohydrazide (H2L2), respectively, have been synthesized and characterized by elemental analysis, infrared and electronic spectra, and 1H NMR spectra. Structures of the complexes were further confirmed by single-crystal X-ray determination. The V atom in the mononuclear complex 1 is in square pyramidal coordination, and those in the dinuclear complex 2 are in octahedral coordination. Both aroylhydrazone ligands coordinate to the V atoms through the phenolate O, imino N, and enolate O atoms. The ethanol ligand in complex 1 is in terminal coordination mode, while that in complex 2 is in bridging coordination mode. The complexes function as effective olefin epoxidation catalysts with hydrogen peroxide as terminal oxidant and sodium hydrogen carbonate as a co-catalyst.

A Series of Manganese(III) Salen Complexes as a Result of Team-Based Inquiry in a Transnational Education Programme.

The development of a team-based approach to research-led transnational practical chemistry teaching is described in which a team of five Chinese students on an articulated transnational degree programme, supported by a team of academic and technical staff, carried out a study examining the structural chemistry of a series of manganese(III) salen complexes. A series of four crystallographically characterized manganese(III) salen complexes with ancillary carboxylate ligands are reported here. The carboxylate coordination modes range from the bridging syn-anti μ2 -κO : κO' mode observed in the predominant cyclohexanoate and isobutyrate species, to a capping terminal monodentate mode for the adamantanoate species, and an unusual mixture of bridging and terminal coordination modes observed in a second minor phase of the cyclohexanoate species. The variation on extended structures based on the weakly interacting aliphatic backbones may provide a useful basis for further structural studies.

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization.

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ-butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO:κO')di-μ-hydroxido-bis[(butyl 2,6-di-tert-butyl-4-methylphenyl hydrogen phosphato-κO)(butyl 2,6-di-tert-butyl-4-methylphenyl phosphato-κO)chromium](Cr-Cr) heptane disolvate or {Cr2(μ2-OH)2[μ2-PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO:κO']2[PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2[HOPO(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2}·2C7H16, [Cr2(C19H32O4P)4(C19H33O4P)2(OH)2]·2C7H16, denoted (1)·2(heptane), [μ-bis(2,6-diisopropylphenyl) phosphato-1κO:2κO']bis[bis(2,6-diisopropylphenyl) phosphato]-1κO,2κO-chlorido-2κCl-triethanol-1κ2O,2κO-di-μ-ethanolato-1κ2O:2κ2O-dichromium(Cr-Cr) ethanol monosolvate or {Cr2(μ2-OEt)2[μ2-PO2(O-2,6-iPr2-C6H3)2-κO:κO'][PO2(O-2,6-iPr2-C6H3)2-κO]2Cl(EtOH)3}·EtOH, [Cr2(C2H5O)2(C24H34O4P)3Cl(C2H6O)3]·C2H6O, denoted (2)·EtOH, and di-μ-ethanolato-1κ2O:2κ2O-bis{[bis(2,6-diisopropylphenyl) hydrogen phosphato-κO][bis(2,6-diisopropylphenyl) phosphato-κO]chlorido(ethanol-κO)chromium}(Cr-Cr) benzene disolvate or {Cr2(μ2-OEt)2[PO2(O-2,6-iPr2-C6H3)2-κO]2[HOPO(O-2,6-iPr2-C6H3)2-κO]2Cl2(EtOH)2}·2C6H6, [Cr2(C2H5O)2(C24H34O4P)2(C24H35O4P)2Cl2(C2H6O)2]·2C6H6, denoted (3)·2C6H6. Complexes (1)-(3) have been synthesized by an exchange reaction between the in-situ-generated corresponding lithium or potassium disubstituted phosphates with CrCl3(H2O)6 in ethanol. The subsequent crystallization of (1) from heptane, (2) from ethanol and (3) from an ethanol/benzene mixture allowed us to obtain crystals of (1)·2(heptane), (2)·EtOH and (3)·2C6H6, whose structures have the monoclinic P21, orthorhombic P212121 and triclinic P-1 space groups, respectively. All three complexes have binuclear cores with a single Cr-Cr bond, i.e. Cr2O6P2 in (1), Cr2PO4 in (2) and Cr2O2 in (3), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ2-OH in (1) or μ2-OEt in (2) and (3). The organophosphate ligands demonstrate terminal κO coordination modes in (1)-(3) and bridging μ2-κO:κO' coordination modes in (1) and (2). All the complexes exhibit hydrogen bonding: two intramolecular Ophos...H-Ophos interactions in (1) and (3) form two {H[PO2(OR)2]2} associates; two intramolecular Cl...H-OEt hydrogen bonds additionally stabilize the Cr2O2 core in (3); two intramolecular Ophos...H-OEt interactions and two O...H-O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in (2)·EtOH. The presence of both basic ligands (OH- or OEt-) and acidic [H(phosphate)2]- associates at the same metal centres in (1) and (3) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short-chain branching. The formation of a small amount of α-olefins has been detected in this reaction.

Hydrogen Bonding Influenced Coordination Mode of Azide Ligand in Schiff base Copper(II) Complexes: Synthesis, Crystal Structures, and Antibacterial Activity

Two copper(II) complexes, [CuL1N3] (I) and [CuL2(μ1, 1-N3)] (II), where L1 = 2-[(2-diethylaminoethylimino)methyl]-4,6-difluorophenolate, L2 = 2,4-difluoro-6-[(2-isopropylaminoethylimino)-methyl]phenolate, have been prepared and structurally characterized by elemental analyses, IR and UV-Vis spectra, as well as single crystal X-ray determination (CIF files CCDC nos. 1848289 (I) and 1848290 (II)). In complex I, the Cu atom is in square planar coordination, with the azide ligand in terminal coordination mode. In complex II, the Cu atom is in square pyramidal coordination, with the azide ligand in end-on bridging mode. The crystals are stabilized by hydrogen bonds, which influence the coordination mode of the azide ligand. The complexes have strong antibacterial activity against B. subtilis and S. aureus.

Bis(2,6-diiso-propyl-phen-yl) phosphato-κO]pentakis-(methanol-κO)manganese bis-(2,6-diiso-propyl-phen-yl) phosphate methanol tris-olvate.

The title compound, [Mn(C24H34O4P)(CH3OH)5](C24H34O4P)·3CH3OH, was formed in the reaction between a hydrate of a manganese(II) salt [either Mn(NO3)2(H2O)6 or MnCl2(H2O)4] with a methanol solvate of lithium bis-(2,6-diiso-propyl-phen-yl) phosphate, {Li[OOP(O-2,6- i Pr2C6H3)2]·(CH4O)3}·CH4O, in methanol. The structure has monoclinic (Cc) symmetry at 150 K. The complex consists of an [Mn{OOP(O-2,6- i Pr2C6H3)2}(CH3OH)5]+ cation, an [OOP(O-2,6- i Pr2C6H3)2]- anion and three non-coordinating methanol mol-ecules. The anion demonstrates disorder of an isopropyl group [occupancy ratio is 0.57 (4):0.43 (4)]. The di-aryl-phosphate ligand in the cation exhibits a κ1 O terminal coordination mode. The Mn atom is in a nearly unperturbed octa-hedral environment. The [Mn{OOP(O-2,6- i Pr2C6H3)2}(CH3OH)5]+ cation exhibits one intra-molecular O-H⋯O bond, and is coordinated via two inter-molecular O-H⋯O hydrogen bonds to the [OOP(O-2,6- i Pr2C6H3)2]- anion. The cations, anions and non-coordinating methanol mol-ecules are linked into infinite chains along the c-axis direction via 0-H⋯O hydrogen bonding. The complex is of inter-est as a possible inhibitor for the thermal decomposition of polydi-methyl-siloxane. The crystal studied was refined as an inversion twin with a domain ratio of 0.47 (3):0.53 (3).

Different coordination modes of trans-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in rare-earth complexes: influence of the metal cation radius and the number of ligands on steric congestion and ligand coordination modes.

A simple and effective synthetic route to homo- and heteroleptic rare-earth (Ln= Y, La and Nd) complexes with a tridentate Schiff base anion has been demonstrated using exchange reactions of rare-earth chlorides with in-situ-generated sodium (E)-2-{[(2-methoxyphenyl)imino]methyl}phenoxide in different molar ratios in absolute methanol. Five crystal structures have been determined and studied, namely tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ3O1,N,O2)lanthanum, [La(C14H12NO2)3], (1), tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato-κ3O1,N,O2)neodymium tetrahydrofuran disolvate, [La(C14H12NO2)3]·2C4H8O, (2)·2THF, tris(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-κ3O1,N,O2;κ3O1,N,O2;κ2N,O1-yttrium, [Y(C14H12NO2)3], (3), dichlorido-1κCl,2κCl-μ-methanolato-1:2κ2O:O-methanol-2κO-(μ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ3O1,N,O2:2κO1)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato)-1κ3O1,N,O2;2κ3O1,N,O2-diyttrium-tetrahydrofuran-methanol (1/1/1), [Y2(C14H12NO2)3(CH3O)Cl2(CH4O)]·CH4O·C4H8O, (4)·MeOH·THF, and bis(μ-2-{[(2-methoxyphenyl)imino]methyl}phenolato-1κ3O1,N,O2:2κO1)bis(2-{[(2-methoxyphenyl)imino]methyl}phenolato-2κ3O1,N,O2)sodiumyttrium chloroform disolvate, [NaY(C14H12NO2)4]·2CHCl3, (5)·2CHCl3. Structural peculiarities of homoleptic tris(iminophenoxide)s (1)-(3), binuclear tris(iminophenoxide) (4) and homoleptic ate tetrakis(iminophenoxide) (5) are discussed. The nonflat Schiff base ligand displays μ2-κ3O1,N,O2:κO1 bridging, and κ3O1,N,O2 and κ2N,O1 terminal coordination modes, depending on steric congestion, which in turn depends on the ionic radii of the rare-earth metals and the number of coordinated ligands. It has been demonstrated that interligand dihedral angles of the phenoxide ligand are convenient for comparing steric hindrance in complexes. (4)·MeOH has a flat Y2O2 rhomboid core and exhibits both inter- and intramolecular MeO-H...Cl hydrogen bonding. Catalytic systems based on complexes (1)-(3) and (5) have demonstrated medium catalytic performance in acrylonitrile polymerization, providing polyacrylonitrile samples with narrow polydispersity.

Thorium aspartate tetrahydrate precursor to ThO2: Comparison of hydrothermal and thermal conversions

The synthesis of original crystalline thorium aspartate tetrahydrate, Th(C4NO4H6)4.4H2O, was performed using two different wet-chemistry routes, involving either L-asparagine or L-aspartic acid as complexing agent. Characterization of this compound through 13C NMR and PXRD led to confirm the terminal coordination mode of the aspartate group and to suggest a potential cubic lattice (Pn-3 space group). Vibrational spectroscopy data were also collected. The conversion of thorium aspartate tetrahydrate into thorium dioxide was further performed through classical high temperature heat treatment or under hydrothermal conditions. On the one hand, thermal treatment provided a pseudomorphic conversion which retained the starting morphology, and favored the increase of the average crystallite size, as well as the complete elimination of the residual carbon content. On the other, hydrothermal conversion could be used to tune the morphology of the final oxide, ThO2.nH2O microspheres being prepared when starting from L-asparagine.

Cadmium(II) thiosaccharinate (tsac) complexes: Crystal structures of [Cd(tsac)2(abtH)2] (abtH = 2-aminobenzothiazole), [Cd(tsac)2(bimsH)2] (bimsH = 2-mercaptobenzimidazole) and [Cd(μ-tsac)(tsac)(κ2-aapH)]2 (aapH = 2-acetylaminopyridine)

A range of new cadmium(II) thiosaccharinate (tsac) complexes have been prepared from reactions of the synthon [Cd(tsac)2·H2O] with a variety of two-electron donor ligands including amino- and acetyl-amino heterocycles, 2-mercaptobenzoimidazole, 2-mercaptobenzothiozole and 2-phenylpyridine, as well as the bidentate small bite-angle diphosphane, bis(diphenylphosphino)methane (dppm), and the tridentate ligand 2,6-diacetylamidopyridine (daapH2). Four types of complex have been isolated, namely [Cd(tsac)2L2], [Cd(tsac)2L], [Cd(tsac)2(μ-dppm)]2 and [Cd(tsac)2(κ3-daapH2)(H2O)]. Crystal structures of three, namely [Cd(tsac)(μ-tsac)(κ2-aapH)]2 (aapH=2-acetylaminopyridine), [Cd(tsac)2(abtH)2] (abtH=2-aminobenzothiazole) and [Cd(tsac)2(bimsH)2] (bimsH=2-mercaptobenzimidazole) have been carried out. In all the tsac ligand(s) bind exclusively through coordination of the thiocarbonyl sulfur atom highlighting the chalcogenophilic nature of cadmium. In [Cd(tsac)(μ-tsac)(κ2-aapH)]2 the tsac ligands adopt both bridging and terminal coordination modes, the former being relatively rare.

Gold(I) Complexes [N{(C3F7)C(Dipp)N}2]AuL (L = Ethylene, tert‐Butyl Isocyanide, Tetrahydrothiophene, Triphenylphosphine) and Different Triazapentadienyl Ligand Coordination Modes

Fluorinated 1,3,5‐triazapentadienyl ligand [N{(C3F7)C(Dipp)N}2] (Dipp = 2,6‐iPr2C6H3) has been used in the synthesis of monomeric gold(I)‐ethylene, tBuNC, tetrahydrothiophene (THT), and PPh3 complexes. X‐ray crystal structures show a rich diversity of coordination modes in which gold coordinates to the central nitrogen atom of 1,3,5‐triazapentadienyl ligand in tBuNCAu[N{(C3F7)C(Dipp)N}2] and (THT)Au[N{(C3F7)C(Dipp)N}2] or one of the two terminal nitrogen atoms in [N{(C3F7)C(Dipp)N}2]Au(THT) and [N{(C3F7)C(Dipp)N}2]Au(PPh3), or to both terminal nitrogen atoms in the chelated [N{(C3F7)C(Dipp)N}2]Au(C2H4). The triazapentadienyl ligand therefore serves as either κ1‐N or κ2‐NN donor, and the N3C3 backbone adopts either a distorted W‐ or U‐shaped conformation. The gold(I) THT adduct exists as a mixture of two isomers in the solid state, as evident from structural data. The gold(I) atom in tBuNCAu[N{(C3F7)C(Dipp)N}2], (THT)Au[N{(C3F7)C(Dipp)N}2], [N{(C3F7)C(Dipp)N}2]Au(THT), and [N{(C3F7)C(Dipp)N}2]Au(PPh3) display linear geometry, whereas [N{(C3F7)C(Dipp)N}2]Au(C2H4) has a three‐coordinate, trigonal‐planar gold site. Energies of each [N{(CF3)C(Dipp)N}2]AuL (L = ethylene, tBuNC, PPh3 and THT) in κ2‐NN chelating, κ1‐N central, and κ1‐N terminal coordination modes of triazapentadienyl ligand have also been investigated by using DFT.

Synthesis, characterization, and reactivity studies of a water-soluble bis(alkoxo)(carboxylato)-bridged diMn(III) complex modeling the active site in catalase.

A new diMn(III) complex, Na[Mn2(5-SO3-salpentO)(μ-OAc)(μ-OMe)(H2O)]·4H2O, where 5-SO3-salpentOH = 1,5-bis(5-sulphonatosalicylidenamino)pentan-3-ol, has been prepared and characterized. ESI-mass spectrometry, paramagnetic (1)H NMR, EPR and UV-visible spectroscopic studies on freshly prepared solutions of the complex in methanol and 9 : 1 methanol-water mixtures showed that the compound retains the triply bridged bis(μ-alkoxo)(μ-acetato)Mn2(3+) core in solution. In the 9 : 1 methanol-water mixture, slow substitution of acetate by water molecules took place, and after one month, the doubly bridged diMn(III) complex, [Mn2(5-SO3-salpentO)(μ-OMe)(H2O)3]·5H2O, formed and could be characterized by X-ray diffraction analysis. In methanolic or aqueous basic media, acetate shifts from a bridging to a terminal coordination mode, affording the highly stable [Mn2(5-SO3-salpentO)(μ-OMe)(OAc)](-) anion. The efficiency of the complex in disproportionating H2O2 depends on the solvent and correlates with the stability of the complex (towards metal dissociation) in each medium: basic buffer > aqueous base > water. The buffer preserves the integrity of the catalyst and the rate of O2 evolution remains essentially constant after successive additions of excess of H2O2. Turnovers as high as 3000 mol H2O2 per mol of catalyst, without significant decomposition and with an efficiency of k(cat)/K(M) = 1028 M(-1) s(-1), were measured for the complex in aqueous buffers of pH 11. Kinetic and spectroscopic results suggest a catalytic cycle that runs between Mn(III)2 and Mn(IV)2 oxidation states, which is consistent with the low redox potential observed for the Mn(III)2/Mn(III)Mn(IV) couple of the catalyst in basic medium.

A one-dimensional zinc(II) coordination polymer incorporating [1,1′-biphenyl]-4,4′-dicarboxylate andN,N′-bis(pyridin-3-ylmethyl)-[1,1′-biphenyl]-4,4′-dicarboxamide ligands

In the title compound, catena-poly[[[N,N'-bis(pyridin-3-ylmethyl)-[1,1'-biphenyl]-4,4'-dicarboxamide]chloridozinc(II)]-μ-[1,1'-biphenyl]-4,4'-dicarboxylato-[[N,N'-bis(pyridin-3-ylmethyl)-[1,1'-biphenyl]-4,4'-dicarboxamide]chloridozinc(II)]-μ-[N,N'-bis(pyridin-3-ylmethyl)-[1,1'-biphenyl]-4,4'-dicarboxamide]], [Zn2(C14H8O4)Cl2(C26H22N4O2)3]n, the Zn(II) centre is four-coordinate and approximately tetrahedral, bonding to one carboxylate O atom from a bidentate bridging dianionic [1,1'-biphenyl]-4,4'-dicarboxylate ligand, to two pyridine N atoms from two N,N'-bis(pyridin-3-ylmethyl)-[1,1'-biphenyl]-4,4'-dicarboxamide ligands and to one chloride ligand. The pyridyl ligands exhibit bidentate bridging and monodentate terminal coordination modes. The bidentate bridging pyridyl ligand and the bridging [1,1'-biphenyl]-4,4'-dicarboxylate ligand both lie on special positions, with inversion centres at the mid-points of their central C-C bonds. These bridging groups link the Zn(II) centres into a one-dimensional tape structure that propagates along the crystallographic b direction. The tapes are interlinked into a two-dimensional layer in the ab plane through N-H···O hydrogen bonds between the monodentate ligands. In addition, the thermal stability and solid-state photoluminescence properties of the title compound are reported.

Multi-functional d10 metal–organic materials based on bis-pyrazole/pyridine ligands supported by a 2,6-di(3-pyrazolyl)pyridine with different spanning flexible dicarboxylate ligands: synthesis, structure, photoluminescent and catalytic properties

A series of the novel zinc complexes, Zn3(H2L1)2(ox)3(H2O)2·4H2O (1), Zn(H2L1)(ad)·2H2O (2), Zn2(HL2)2(suc)0.5·(HCOO)·H2O (3), Zn2(HL2)2(glu)·2H2O (4), Zn2(HL2)2 (ad)0.5·(OH)·0.5H2O (5), Zn2(HL2)2(seb)(H2O)·2.5H2O (6), (H2L1 = 2,6-di(5-methyl-1H-pyrazol-3-yl)pyridine, H2L2 = 2,6-di(5-phenyl-1H-pyrazol-3-yl)pyridine, H2ox = oxalic acid, H2ad = adipic acid, H2suc = succinic acid, H2glu = glutaric acid, H2seb = suberic acid) were synthesized hydrothermally from the self-assembly of a Zn(II) ion with different types of the new bi-pyrazolyl pyridine derivative ligands and different spanning flexible dicarboxylic compounds as an auxiliary ligand. They were characterized by elemental analysis, IR and UV–vis spectroscopy, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. We found that they are all molecular compounds using the above detections. The structural analysis indicates that the zinc atom in complex 1 is a six-coordinate mode of ZnO3N3, forming a slightly distorted octahedral geometry, while zinc atoms in complexes 2–6 are all penta-coordination modes of ZnO2N3 and ZnON4 in a distorted bipyramidal geometry. The H2L1 ligand is in the form of a μ1–η1–η1–η1 coordination with metallic Zn in 1 and 2; while the HL2 ligand is in a μ2–η1–η1–η1–η1 coordination mode in 3–6. For the oxalate ligand, there are two kinds of coordination modes, μ2–η1–η1–η1–η1 bridging coordination mode and μ1–η1–η1 terminal coordination mode; the coordination mode of glutaric acid ligand is in the form of μ2–η1–η1; suc2− ligand is in the form of a μ4-bridging coordination fashion with each side carboxylate group in a μ2–η1–η1-monodentate mode; the coordination of the adipic acid ligand presents two coordination modes of μ2–η1–η1and μ4–η2–η2; suberic acid ligand acts in a monodentate terminal coordination mode. In addition, thermal behaviors and photoluminescent properties for 1–6 were all performed and are discussed in detail. The catalytic activity of the complexes is evaluated firstly by the reaction of hydrogen peroxide promoted oxidation of cyclohexane and cyclopentane under mild conditions. It is found that the Zn complexes with five different spanning flexible dicarboxylic acids as an auxiliary ligand with oxalic acid, succinic acid, glutaric acid, adipate acid or sebacic acid, respectively, have potential catalytic activity in the oxidation reaction of cyclohexane.

Preorganized assembly of three iron(ii) or manganese(ii) β-diketiminate complexes using a cyclophane ligand

A trinucleating cyclophane bearing three β-diketimine arms, and the corresponding iron(II) and manganese(II) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of μ(3), μ, and terminal coordination modes are observed for the halide donors.

Complexes of unsymmetric bis-hydrazide ligands: crystal structures and properties

Two unsymmetric bis-aroyl-hydrazines, N′-(2-hydroxybenzoyl)isonicotinohydrazide (L1) and N′-(2-hydroxybenzoyl)nicotinohydrazide (L2), were synthesized through reactions of salicyl hydrazide with isonicotinoyl chloride and nicotinoyl chloride, respectively. Reactions of metal salts with L1 or L2 gave three new complexes, [Cd(L1)2(SCN)2] n (1), [Zn(L1)2Cl2] · H2O (2), and [Zn(L2)2Cl2] (3). Complex 1 features a 1-D double-chain structure built by SCN– bridging six-coordinate CdII centers while 2 and 3 are mononuclear ZnII complexes. In 1–3, isomeric ligands L1 and L2 coordinate with metal ions in a terminal coordination mode. Ligands L1 and L2 through O–H···N and N–H···O hydrogen-bonding interactions in 1–3 are crucial for the structure extension into 3-D supramolecular structures of 1 and 2, or 2-D sheet of 3. Complexes 1–3 emit interesting blue-green luminescence. Thermal behaviors of 1–3 as well as the specific rotation of 2 were also investigated.

3-Phenyl-5-(2-pyridyl)pyrazolato Complexes of Lithium, Magnesium, Calcium, and Zinc

Abstract Metalation of 3-phenyl-5-(2-pyridyl)pyrazole (HPz, 1) with alkyllithium and -zinc compounds in tetrahydrofuran (thf) yields dinuclear products [(thf)Li(Pz)]2 (2) and [MeZn(Pz)]2 (3), respectively. Magnesiation of 1 with diethylmagnesium in tetrahydrofuran in the presence of 1,4-dioxane leads to cocrystallization of mononuclear [(thf)2Mg(Pz)2] (4a) and [(diox)2Mg(Pz)2] (4b). Metalation of 1 with KH followed by a metathesis reaction with CaI2 in tetrahydrofuran leads to the formation of dinuclear [{(thf)2Ca}(m-Pz)3Ca(Pz)] (5) with the calcium atoms in different coordination environments. The ligand precursor 1 crystallizes as a dimer with N-H···N bridges between the pyrazole fragments. The pyrazolate anions of the metal complexes 2 to 5 exhibit similar structural parameters regardless of a bridging or terminal coordination mode and the electronegativity of the coordinated metal.

Synthesis, Crystal Structures, Thermal and Magnetic Properties of New Selenocyanato Coordination Polymers with Pyrazine as Co‐Ligand

AbstractReaction of iron(II), cobalt(II) and nickel(II) selenocyanate with pyrazine in water at room temperature leads to the formation of the isotypic new ligand‐rich 1:2 (1:2 = ratio between metal and co‐ligand) compounds [M(NCSe)2(pyrazine)2]n (M = Fe (1), Co (2), Ni (3)). The crystal structure of 2 was determined by X‐ray single crystal analysis and those of 1 and 3 were refined from X‐ray powder data with the Rietveld method. In their crystal structure the metal(II) cations are coordinated by four pyrazine co‐ligands, which connect them into layers, and two terminally N‐bonded selenocyanato anions in a distorted octahedral arrangement. The terminal coordination mode of the selenocyanato anions was further emphasized by IR spectroscopic investigations. On heating, all compounds decompose in a single heating step without the formation of ligand‐deficient intermediates like previously reported for related thiocyanato compounds. Magnetic measurements of compound 1 show a long‐range antiferromagnetic ordering with an ordering temperature of TN = 6.7 K, which must be mediated by the aromatic π‐system of the pyrazine ligand, whereas 2 and 3 show only Curie–Weiss behavior with antiferromagnetic exchange interactions.

Synthesis, Crystal Structure, Thermal, Spectroscopic and Magnetic Properties of a 2D Grid‐like Copper(II) μ‐1,1 Isocyanato Coordination Polymer with Pyrazine Bridges

AbstractReaction of copper(II) cyanate with pyrazine leads to the formation of [Cu(NCO)2(pyrazine)]n (1), in which the Cu2+ cations are coordinated by two nitrogen atoms of the pyrazine ligands, as well as by four nitrogen atoms of the cyanate anions within a slightly distorted octahedral coordination. In the crystal structure the Cu2+ cations are connected by the pyrazine ligands into chains which are further linked by the cyanate anions through asymmetric μ‐1,1‐NCO coordination into layers. On heating compound 1 transforms quantitatively to copper(II) cyanate which decompose to elemental copper on further heating. No ligand deficent intermediates are observed. Magnetic measurements reval an antiferromagnetic ordering at lower temperatures mediated by the π‐system of the aromatic pyrazine ligand as well as net ferromagnetic interactions mediated by the μ‐1,1‐NCO bridging cyanato anions. A search in the Cambridge Crystal Structure Database shows that the terminal coordination mode in cyanato complexes as well as their azido and thiocyanato analogs is obviously energetically favored. In addition, a comparison of their symmetric and asymmetric end‐on (μ‐1,1) as well as end‐to‐end (μ‐1,3) bridging modes reveal interesting correlations.