The synthesis, characterization, and alkylation of nacnac chromium triflate derivatives

A Cr(III) triflate coordinated by the bulky β-diketiminate ^MeL^iPr (^MeL^iPr = 2,4-pentane N,N′-bis(2,6-diisopropylphenyl)diketiminate) was synthesized from the corresponding bridging iodide complex [^MeL^iPrCr(μ-I)]₂ by ligand substitution and subsequent oxidation with silver triflate (AgOTf). ^MeL^iPr Cr^III(OTf)₂ exhibits rare trigonal bipyramidal geometry about Cr(III). Attempts to alkylate this triflate synthon with 1,4-dilithiobutane (Li(CH₂)₄Li) led to reduction, while reaction with dimethylzinc (ZnMe₂) led to a mono-alkylated product; only the reaction with methyl lithium (MeLi) was successful in generating a dialkyl.     

Synthesis and properties of crown ether isocyanide silver(I) derivatives: X-ray structure of a self-assembled 22-membered diargentacycle

The crown ether isocyanide CNR (R = benzo-15-crown-5) reacts with silver(I) salts in the appropriate molar ratio to give [Ag(CNR)_n]X (n = 1, 2; X = CF₃SO₃, BF₄). X-ray diffraction studies of [Ag(CF₃SO₃)(CNR)] show the molecules associated in a dinuclear manner with an antiparallel orientation. The silver centers are tetracoordinated to the isocyanide and to three oxygens, one from the triflate anion and two from the second crown ether in the dimer. The molecular structure displays five cycles: the two 15-crown ether rings, two five-membered argentacycles and a 22-membered diargentacycle. The crown ether in these complexes is able to detect alkaline cations from M(CF₃SO₃) (M = Li, Na, K) by NMR in d₆-acetone solutions, and to distinguish Li⁺-Na⁺ from K⁺.     

One-dimensional coordination polymer and its hydrogen bonded 2D network generated from dimeric Ag(I) building units

A new dimeric silver(I) complex [Ag(PhPPy₂)(CH₃CN)]₂(ClO₄)₂ (1) (PhPPy₂ = bis(2-pyridyl)phenylphosphine) was synthesized by a direct reaction of [Ag(CH₃CN)₄]ClO₄ with ligand PhPPy₂. X-ray crystallographical studies revealed that in 1, two silver atoms are bridged by two PhPPy₂ ligands and bonded to each other. Each Ag(I) adopts a distorted trigonally bi-pyramidal geometry, and axially coordinated acetonitrile molecules are collinear with two silver atoms. By using 1 as a building block precursor, a 1D coordination polymer, [Ag₂(PhPPy₂)₂(1,3,5-C₆H₃(CO₂)₂(CO₂H))]_∞ (2) was prepared by replacing axially coordinated acetonitrile molecules in 1 with two carboxylate groups of a bridging ligand, 1,3,5-benzenetricarboxylate. In solid state, linear polymeric chains are oriented parallel to each other and interestingly interact by hydrogen bonding through their carboxylic/carboxylate groups to construct a novel wave-shaped 2D network. Both 1 and 2 exhibit similar photoluminescent properties in solid state at room temperature.     

Syntheses, thermal analyses, crystal structures and antimicrobial properties of silver(I)-saccharinate complexes with diverse diamine ligands

Five new silver(I)-saccharinate complexes [Ag₂(sac)₂(tmen)₂] (1), [Ag₂(sac)₂(deten)₂] (2), [Ag₂(sac)₂(dmen)₂] (3), [Ag(sac)(N,N-eten)] (4), and [Ag(sac)(dmpen)]_n (5); (sac = saccharinate, tmen = N,N,N′,N′-tetramethylethylenediamine, deten = N,N′-diethylethylenediamine, dmen = N,N′-dimethylethylenediamine, N,N-eten = N,N-diethylethylenediamine and dmpen = 1,3-diamino-2,2-dimethylpropan) have been synthesized and characterized by elemental analyses, IR, thermal analyses, single crystal X-ray diffraction and antimicrobial activities. The crystallographic analyses show that all the complexes crystallize in monoclinic space group P2₁/c. In 1, the sac ligand acts as a bridge to connect the silver centres through its imino N and carbonyl O atoms forming an eight-membered bimetallic ring in a chair conformation. Complex 2 has also a dimeric structure in which the monomeric [Ag(sac)(deten)] units are linked by Ag?Ag interactions. In 3, saccharinate ligand acts as a bridging bidentate ligand between two silver(I) centres through sulfonyl group and imino N atom, forming an alternating polymeric chain through the direction [0 1 0]. In 4, the inter-molecular N-H?O hydrogen bonds form one-dimensional polymeric chains through the a axis, and these linear chains are inter-connected to each other by N-H?O hydrogen bonds, which produce a chain of edge-fused and rings along [1 0 0]. Complex 5 is a coordination polymer in which the monomeric [Ag(dmpen)(sac)]_n units are linked by Ag?Ag interactions, and the dmpen ligand acts as a bridge between the silver(I) ions, forming a two-dimensional network parallel to the (1 0 0) plane.     

Syntheses, crystal structures, spectroscopic, fluorescence and thermal properties of silver(I) 5,5-diethylbarbiturato complexes with some aminopyridines

Three new silver(I) complexes of 5,5-diethlybarbiturate (barb), [Ag(barb)(apy)]·H₂O (1), {[Ag(μ-ampy)][Ag(μ-barb)₂]}_n (2) and [Ag(barb)(dmamhpy)] (3) [apy = 2-aminopyridine, ampy = 2-aminomethylpyridine and dmamhpy = 2-(dimethylaminomethyl)-3-hydroxypyridine] have been synthesized and characterized by elemental analysis and FT-IR. Single crystal X-ray diffraction analyses showed that complexes 1 and 3 are mononuclear. In 1, the silver(I) ion is linearly coordinated by a barb anion and a ampy ligand, while a bidentate dmamhpy ligand together with an N-coordinated barb anion forms a trigonal coordination geometry around silver(I) in 3. Complex 2 is a one-dimensional coordination polymer in which silver(I) ions are bridged by ampy ligands, leading to a cationic chain . The [Ag(barb)₂]⁻ units contains two N-bonded barb ligands, bridging the silver centers in the cationic and anionic units via the carbonyl O atoms. Thus, complex 2 contains two-coordinated and four-coordinated silver ions. All complexes display hydrogen-bonded network structures and exhibit appreciable fluorescence at room temperature. Thermal analysis (TG-DTA) data are in agreement with the structures of the complexes.     

An unprecedented iron(III) complex supported by an asymmetric N-capped tripodal ligand incorporating the NO2S donor set

The synthesis of an iron(III) complex [Fe(L)(1-Meim)] (1-Meim = 1-methylimidazole) coordinated by an asymmetric N-capped tripodal tetradentate ligand (L) equipped with three aromatic arms is described. X-ray crystallographic analysis shows that the complex adopts a distorted bipyramidal geometry with a new type of N₂O₂S coordination environment around the iron centre.     

Structure and solution behaviour of cyclooctadiene complexes of platinum(II)

The substitution behaviour of [PtCl(R)(COD)] (R⁻ = Me and Fc) complexes, by the stepwise addition of phosphine ligands, L (L = PPh₃, PEt₃ and P(NMe₂)₃), were investigated in situ by ¹H and ³¹P NMR spectroscopy. Addition of less than two equivalents of the phosphine ligand results in the formation of dimeric molecules with the general formula trans-[Pt(R)(μ-Cl)(L)]₂ for the sterically demanding systems where R⁻ = Me/L = P(NMe₂)₃ and R⁻ = Fc/L = PEt₃, PPh₃ and P(NMe₂)₃ while larger quantities resulted in cis- and trans mixtures of mononuclear complexes being formed. In the case of the relatively small steric demanding, strongly coordinating, PEt₃ ligand the trans-[PtCl(R)(PEt₃)₂] mononuclear complexes were exclusively observed in both cases. The crystal structures of the two substrates, [PtCl(R)(COD)] (R⁻ = Me or Fc), as well as the cis-[PtCl(Fc)(PPh₃)₂] substitution product are reported.     

The synthesis, crystal and molecular structures of two saccharinate-metal complexes with dipyridylamine (dipyr) as a co-ligand

The complexes [Cd(dipyr)₂(sac)(H₂O)] sac·H₂O 1 and [Hg(dipyr)(sac)₂] 2, where dipyr = dipyridylamine and sac = saccharinate, have been synthesised, and fully characterised by single-crystal X-ray diffraction at 120 K. The geometry around Cd in 1 is approximately octahedral, with the metal coordinated by two bidentate dipyr ligands, one N-bonded sac and one H₂O molecule; the second sac forms the counter-ion, and there is also a water of crystallisation. An extensive H-bonded network is formed. In the anhydrous Hg complex 2, the metal has approximately tetrahedral geometry, with coordination from a bidentate dipyr ligand and two N-bonded sac groups. H-bonding interactions are again extensive, even without the presence of H₂O molecules in the structure, leading to chains along the a-axis.     

A zigzag chain coordination polymer consisting of silver(I) ion having square planar geometry

Silver(I) complexes of hexakis(tolylsulfanyl)benzene (htsb), [Ag(htsb)](PF₆) (1), have been prepared and their molecular structures were determined by X-ray crystallography. In 1, the silver ion prefers a square planar coordination geometry comprized of four S atoms from two different htsb molecules and producing a zigzag chain structure of AgS in the silver coordination polymer. Based on the thermo-gravimetry analysis results, two tolylsulfanyl groups were easily eliminated at approximately 211 °C. However, [Ag(htsb)(2-butanone)] (PF₆) (2), which were obtained by the reactions in different solvents, showed a different colors and thermal degradation behaviors.     

The synthesis and characterisation of phenolate complexes of Cu(II) and Ni(II) that are capable of supporting a phenoxyl radical ligand

New Cu^II and Ni^II complexes of potentially tridentate N₂O Schiff base ligands 1 and 2 have been synthesised and characterised. [Cu(2)(OH₂)]⁺ possesses a square planar geometry in the solid state whereas [Ni(1)₂] possesses a distorted octahedral geometry in which the amine donors of 1 coordinate weakly to the Ni^II centre. EPR spectroscopy demonstrates that the N₂O₂ coordination sphere of [Cu(2)(OH₂)]⁺ is retained in CH₂Cl₂ solution. [Cu(2)(OH₂)]⁺ exhibits a reversible one electron oxidation at E_1/2 = 0.54 V versus [Fc]⁺/[Fc], the product of which has been characterised by UV-Vis absorption and EPR spectroscopies. The spectroscopic signature of the oxidised product is consistent with the formation of a stable phenoxyl radical ligand bound to a Cu^II centre. [Ni(1)₂] possesses a reversible metal-based oxidation process at E_1/2 = 0.03 V versus [Fc]⁺/[Fc] and a further oxidation, attributed to the generation of a phenoxyl radical centre, at  = 0.44 V versus [Fc]⁺/[Fc]. UV-Vis absorption and EPR spectroscopic studies indicate that the lower potential process is a formal Ni^III/II couple. In contrast, the pro-ligands 1H and 2H exhibit chemically irreversible oxidation processes at  = 0.42 and 0.40 V versus Fc⁺/Fc, respectively, and do not support the formation of stable phenoxyl radical species.     

The formation and isolation of benzisothiazole rings from the reactions of oxime-thiophenolate ligands

The reaction of [Ni(eftp)] [eftp = N,N-ethylene(6-formyl-4-methyliminatothiophenolato)] with hydroxylamine hydrochloride in the presence of potassium acetate in MeOH resulted in the formation of [Ni(L)₂], L = 2-mercapto-5-methyl-3-({2-[(5-methyl-benzo[d]isothiazol-7-ylmethylene)-amino]-ethylimino}-methyl)-benzonitrile. A single-crystal X-ray diffraction structural determination showed that the oxime groups of the proposed new binucleating ligand had reacted to produce a nitrile and an isothiazole ring, while two ligand molecules combined with one Ni(II) ion to form a new complex with a cis-S₂N₂ square-planar geometry. Also, the reaction of 2,6-diformyl-4-methylphenyl disulfide with hydroxylamine in MeCN resulted in the synthesis of 5-methyl-2-oxy-benzo[d]isothiazole-7-carbaldehyde oxime, where an isothiazole ring had formed via the cleavage of the disulfide bond. Again, a single-crystal X-ray diffraction study confirmed the presence of a benzisothiazole product.     

Structures and electrochemistry of monomeric and dimeric CpCo(dithiolene) complexes with substituted benzene-1,2-dithiolate ligand

The molecular structures of [CpCo(tdt)] and [CpCo(Cl₃bdt)] were determined by X-ray diffraction studies. [CpCo(tdt)] was monomeric in the crystal, coordinatively unsaturated with 16-electrons and had a two-legged piano-stool geometry. [CpCo(Cl₃bdt)] was dimeric, coordinatively saturated with 18-electrons and became a three-legged piano-stool geometry. There were two crystallographically independent molecules in [CpCo(tdt)] and both molecules were associated with intermolecular Cp?Cp face-to-face interaction. Some intermolecular Co?S interactions were also observed between the crystallographically identical molecules of [CpCo(tdt)]. The cyclic voltammograms of [CpCo(tdt)] and [CpCo(Cl₂bdt)] exhibited single oxidation waves, but those of [CpCo(Cl₃bdt)] and [CpCo(Cl₄bdt)] showed two oxidation waves due to both the monomer and dimer in the solutions. Electrochemical oxidations of these monomers occurred dimerizations by EC reactions in the solutions, and the oxidized dimers could be rereduced to form the original monomers by EC reactions. Spectroelectrochemical data using OTTLE supported the reversible ECEC reactions. Abbreviations of dithiolene ligands are as follows: tdt = toluene-3,4-dithiolate, Cl₂bdt = 3,6-dichlorobenzene-1,2-dithiolate, Cl₃bdt = 3,4,6-trichlorobenzene-1,2-dithiolate, and Cl₄bdt = tetrachlorobenzene-1,2-dithiolate.     

3D coordination polymers of [2.2]paracyclophane and in situ silver(I) perfluoro-dicarboxylates: effects of the dicarboxylate spacers and conformations on the formation of complexes

Coordination polymers of [2.2]paracyclophane (pcp) with in situ silver(I) perfluoro-dicarboxylates characterized by single crystal X-ray analysis are described. Structures are found to strongly depend on the dicarboxylate spacer (n). With disilver(I) tetrafluorosuccinate ((CF₂)_n(COOAg)₂, n = 2), 3D network with composition of [Ag₄(pcp)(C₂F₄(CO₂)₂)₂] (1) forms in which silver salts afford infinite double chains and pcp act as linkages between chains. Changing the silver salt to disilver hexafluoroglutarate ((CF₂)_n(COOAg)₂, n = 3) produces 3D pillared-layer structure of composition of [Ag₄(pcp)(C₃F₆(CO₂)₂)₂] · THF (2) (THF = tetrahydrofuran), in which silver salts form 2D sheets and pcp act as pillars between the sheets. With silver octafluoroadipate (HO₂C(CF₂)_nCO₂Ag, n = 4), 2-fold interpenetrated diamond structure, [Ag₂(pcp)₂(HO₂CC₄F₈CO₂)₂]₂ · 2toluene (3), is obtained in which silver-anion chains and silver-pcp chains are connected with each other in the perpendicular manner. The three complexes represent unprecedented metal-organic networks of silver(I) multicarboxylates and polycyclic aromatic compounds. Additionally, the effects of the dicarboxylate conformations as well as the solvents on the resulting structures were discussed.     

Synthesis, characterization and copper chemistry of a non-symmetric phenanthroline ligand: 2-Methyl-9-(3,5-dimethyl-N-pyrazolylmethyl)-1,10-phenanthroline

The synthesis of an unsymmetrical phenanthroline-based ligand, 2-methyl-9-(3,5-dimethylpyrazolylmethyl)-1,10-phenanthroline (L), and its cupric [Cu(II)] (1) and cuprous [Cu(I)] (2) complexes, are reported. The X-ray structures of each of these Cu complexes show distinct changes in coordination environments consistent with the geometrical preferences of the two oxidation states. In the solid-state, the Cu(II) complex (1) adopts a geometry best described as trigonal bipyramidal, while the Cu(I) complex (2) consists of a single dicationic dimer in which the ligand bridges between two copper ions, separated by 4.26 Å. The two Cu(I) coordination sites differ in 2 with one copper center complexed in a trigonal planar geometry and the other copper in a distorted tetrahedral environment; the latter coordination results from an additional CH₃CN ligand. Complex 1 exhibits a reversible redox process at −0.34 V versus Fc/Fc⁺ in CH₃CN, attributable to the Cu²⁺/Cu⁺ couple, while the dimeric Cu(I) complex (2) does not display this redox couple on the CV timescale. Over minutes however, complex 1 does oxidize in the presence of dioxygen to 2 in CH₃CN.     

Synthesis, structures, and magnetic properties of one-dimensional Fe-M (M = Ni, Cu) coordination polymers bridged by nitroprusside

Self-assembling [Fe(CN)₅(NO)]²⁻ and [M(L)]²⁺ (M = Ni, Cu; L = macrocycles) led to one-dimensional coordination polymers, [Ni(L1)][Fe(CN)₅(NO)] · 2H₂O (1) with parallel chains and [Cu(L2)][Fe(CN)₅(NO)] · 3H₂O (2) exhibiting a slanted chain structure. Compound 1 contains a planar macrocycle L1 coordinated to a slightly distorted octahedral Ni(II) ion in which the planarity of L1 gives rise to piling up chains in parallel. In contrast, a more flexible macrocyclic ligand L2 in 2 that surrounds a Cu center with a tetragonal elongation has bulky cyclohexyl groups together with pendant methyl side groups. The presence of the methyl groups on L2 in a chain makes the cyclohexyl groups in an adjacent chain tilted against the CuN₄ basal plane with the methyl groups, eventually resulting in the slanted chain structure. Magnetic data demonstrate that antiferromagnetic interactions (J ≈ −0.13 cm⁻¹) are operating although the paramagnetic centers are linked by the long diamagnetic [Fe(CN)₅(NO)]²⁻ anion.     

Palladium(II) complexes of 1,10-phenanthroline: Synthesis and X-ray crystal structure determination

Two palladium(II) complexes, [Pd(phen)(NCCH₃)₂][O₃SCF₃]₂ (1) and [Pd(phen)(μ-OH)]₂[O₃SCF₃]₂ · 2H₂O (2) (where phen = 1,10-phenanthroline), have been crystallized following the reaction of Pd(phen)Cl₂ with silver triflate, Ag(O₃SCF₃), in acetonitrile and water, respectively. The structures of both complexes are based on a Pd(phen)²⁺ metal core, with two acetonitrile molecules binding in a monodentate fashion in complex 1 and two hydroxo bridges holding together two cores to form a dimer in complex 2. Additionally, both complexes present a hydrogen bonded 3-D network involving the triflate anions in 1, and water and triflate anions in 2. Both complexes have been characterized by infrared and ¹H NMR spectroscopy and their crystal structures determined by X-ray crystallography.     

Synthesis, characterization, crystal structures, and photophysical properties of a series of room-temperature phosphorescent copper(I) complexes with oxadiazole-derived diimine ligand

In this paper, we report four phosphorescent Cu(I) complexes of [Cu(OP)(PPh₃)₂]BF₄, [Cu(Me-OP)(PPh₃)₂]BF₄, [Cu(OP)(POP)]BF₄, and [Cu(Me-OP)(POP)]BF₄ with oxadiazole-derived diimine ligands, where OP = 2-(5-phenyl-[1,3,4]oxadiazol-2-yl)-pyridine, Me-OP = 2-(5-p-tolyl-[1,3,4]oxadiazol-2-yl)-pyridine, POP = bis(2-(diphenylphosphanyl)phenyl) ether, and PPh₃ = triphenylphosphane, including their synthesis, crystal structures, photophysical properties, and electronic nature. The Cu(I) center has a distorted tetrahedral geometry within the Cu(I) complexes. Theoretical calculation reveals that all emissions originate from triplet metal-to-ligand-charge-transfer excited state. It is found that the inter-molecular sandwich structure triggered by inter- and intra-molecular pi-stacking within solid state Cu(I) complexes is highly effective on restricting the geometric relaxation that occurs in excited states, and thus greatly enhances the photoluminescence (PL) performances, including PL quantum yield improvement, PL decay lifetime increase, and emission blue shift.     

Synthesis, characterisation and crystal structures of a few coordination complexes of nickel(II), cobalt(III) and zinc(II) with N′-[(2-pyridyl)methylene]salicyloylhydrazone Schiff base

Four new coordination complexes, Ni^II(L)₂ (1), [Co^III(L)₂]ClO₄ (2), [Zn(HL)(L)]ClO₄ · H₂O (3) and [Zn(L)₂][Zn(L)(HL)]ClO₄ · 7H₂O (4) (where L is a monoanion of a Schiff base ligand, N′-[(2-pyridyl)methylene]salicyloylhydrazone (HL) with NNO tridentate donor set), have been synthesised and systematically characterised by elemental analysis, spectroscopic studies and room temperature magnetic susceptibility measurements. Single crystal X-ray diffraction analysis reveals that 1 is a neutral complex, while 2-4 are cationic complexes. Among them, 4 is a rare type of cationic complex with two molecules in the asymmetric unit. The ligand chelates the metal centre with two nitrogen atoms from the pyridine and imino moieties and one oxygen atom coming from its enolic counterpart. All the reported complexes show distorted octahedral geometry around the metal centres, with the two metal-N (imino) bonds being significantly shorter than the two metal-N (Py) bonds.     

Copper(I) halide complexes from cis-1,2-bis(diphenylphosphino) ethylene and some heterocyclic thiones

Reaction of copper(I) chloride or bromide with equimolar amounts of the diphos ligand cis-1,2-bis(diphenylphosphino)ethylene (dppet) and a heterocyclic thione (L) in acetonitrile/methanol solvent afforded mononuclear complexes of the type [CuX(dppet)(L)] with the diphosphine ligand acting as a chelating ligand. However, the same reaction carried out at higher temperatures proceeds, in some cases, with exclusion of the phosphine ligand from the coordination sphere leading to double-S-bridged dimers. In contrast, copper(I) iodide under the same conditions gave the thione-free dimeric compound [CuI(dppet)]₂ which contains double-bridging iodine atoms. A notable exception was for the reaction with 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH) which, under the same conditions, gave rise to the unexpected, simultaneous formation of the monomer [CuI(dppet)(CH₃CN)] as well as the above mentioned dimeric [CuI(dppet)]₂. Furthermore treatment [CuX(dppet)(L)] with two equivalents of triphenylphosphine was found to cause replacement of the diphos ligand, while substitution of the chlorine atom under HCl elimination and formation of [Cu(dppet)(mftztH)₂] occured in the unique case of treating [CuCl(dppet)(mftztH)] with one additional equivalent of the same thione ligand. The structures of one representative for each of the above mentioned types of complexes, namely [CuBr(dppet)(mftztH)], [Cu(dppet)(mftztH)₂], [Cu(μ-I)(dppet)]₂ · [CuI(dppet)(CH₃CN)] and [CuBr{μ-S(pymtH)}(pymtH)]₂ have been established by single-crystal X-ray diffraction.     

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.