Isolation and characterization of main group and late transition metal complexes using orthometallated imine ligands

Several late transition metal and main group orthometallated imine complexes were synthesized by utilizing ortholithiated imine precursors. Magnesium, aluminum, zinc, copper(I), and tin(IV) complexes were isolated and characterized. Subsequent reactions with electrophiles such as Ph(2)PCl, MeI and I(2) yielded several functionalized products, including a new iminophosphine ligand and its corresponding copper(I) complex. The coordination modes of the orthometallated imine ligands, as well as the structures of the metal complexes, were studied in the solid state using small molecule X-ray diffraction when possible.     

DFT characterization of 1-acetylpiperazinyl-dithiocarbamate ligand and its transition metal complexes

Employing DFT and handling the solvent effects with the PCM model, the 1-acetylpiperazinyldithiocarbamate acpdtc ligand and its M(acpdtc)₂ complexes, where M is Mn(II), Fe(II), Co(II), Ni(II) and Cu(II), are characterized computationally. The obtained results suggest that the piperazine ring adopts chair conformation in all the studied species. In the gas and solution phases, the chair form of the ligand is dominant. For the Mn, Fe and Co complexes the tetrahedral structure is more stable than the square form in the gas and solution phases. However, the Ni and Cu complexes adopt the square form, in which the complex has the inversion center. The calculated vibrational frequencies are in agreement with the experimental ones, confirming the suitability of the optimized geometries of the compounds. Atomic charges, electron distribution of the frontier orbitals, and stabilizing electron transfers are determined by the NBO analysis.     

Synthesis and structural characterization of nickel(II) hexaazamacrotetracyclic complexes with phthalate ligands

Highly crosslinked polymeric networks formed by cyclodextrins (CD) have recently been shown to be highly versatile nanosponge systems, being for instance very efficient both for drug delivery and for pollutants removal. Here we report some molecular simulation results for dry and hydrated CD nanosponge models aimed to study their swelling behavior. We also report simulation results about the water mobility in these systems in terms of the calculated diffusion coefficient of “free” and of “bound” water molecules confined within the nanosponge cavities. Furthermore, we also suggest the presence of surface-constrained water molecules temporarily bound to the network surface but eventually set free in the bulk.     

Synthesis, characterization, and lactide polymerization activity of group 4 metal complexes containing two bis(phenolate) ligands

A series of group 4 metal complexes Zr-(1)(2), Zr-(2)(2), Zr-(3)(2), Zr-(4)(2), Zr-(5)(2), Hf-(1)(2), and Hf-(4)(2) containing two bridged bis(phenolate) ligands of the (OSSO)-type were prepared by the reaction of the corresponding bis(phenol) and group 4 metal precursor MX(4) (X = O(i)Pr, CH(2)Ph) and isolated as robust, colorless crystals. NMR spectra indicate D(2) symmetry, in agreement with the solid state structure determined by single crystal X-ray diffraction study of the complexes Zr-(1)(2), Hf-(1)(2), Zr-(3)(2), Zr-(4)(2), and Zr-(5)(2). The complexes with the 1,4-dithiabutanediyl bridged ligands exhibit a highly symmetric coordination around the metal center. The introduction of the rigid trans-1,2-cyclohexanediyl bridged ligands led to a distorted coordination around the metal center in Zr-(4)(2) and Zr-(5)(2) when the ortho substituent is tert-butyl and the para substituent is larger than methyl. The complexes Zr-(1)(2), Zr-(2)(2), Zr-(3)(2), Zr-(4)(2) as well as Hf-(1)(2) and Hf-(4)(2) initiated the ring-opening polymerization of meso-lactide at 100 °C to give heterotactic polylactide with pronounced heterotacticity (>70%) and varying polydispersity (1.05 < M(w)/M(n) < 1.61). As shown by kinetic studies, zirconium complex Zr-(1)(2) polymerized meso-lactide faster than the homologous hafnium complex Hf-(1)(2).     

Synthesis and characterization of binuclear transition metal–rhenium(VII) complexes with bridging cyanide ligands

Reacting transition metal complexes in low oxidation states, containing one or two cyanide ligands, with methyltrioxorhenium(VII) leads to bridged mixed metal compounds in good yields. The Re(VII) core is then surrounded by five or six ligands, respectively. The strength of these CN bridges and thus the stability of the newly generated bimetallic compound strongly depends on the donor strength of the ligands surrounding of the Cr/Mo/W or Fe moiety. The stability of the mixed metal molecules is reflected in the temperature dependent behavior of their ¹⁷O-NMR spectra, in their IR (Re=O) stretching frequencies and force constants, as well as several other spectroscopic data. UV–vis absorption spectra show the appearance of charge transfer bands. In the case of the mixed Mo/Re complexes the ⁹⁵Mo-NMR spectroscopy is also a helpful tool to examine the donor capability of the Mo moiety. The described compounds also show photosensitivity.     

Spectral, structural and DFT studies of platinum group metal 3,6-bis(2-pyridyl)-4-phenylpyridazine complexes and their ligand bonding modes

Reactions of 3,6-bis(2-pyridyl)-4-phenylpyridazine (L^ph) with [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆), [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂, (M = Rh and Ir) and [(η⁵-Cp)Ru(PPh₃)₂Cl] (Cp = C₅H₅, C₅Me₅ and C₉H₇) afford mononuclear complexes of the type [(η⁶-arene)Ru(L^ph)Cl]PF₆, [(η⁵-C₅Me₅)M(L^ph)Cl]PF₆ and [(Cp)Ru(L^ph)(PPh₃)]PF₆ with different structural motifs depending on the π-acidity of the ligand, electronic properties of the central metal atom and nature of the co-ligands. Complexes [(η⁶-C₆H₆)Ru(L^ph)Cl]PF₆1, [(η⁶-p-ⁱPrC₆H₄Me)Ru(L^ph)Cl]PF₆2, [(η⁵-C₅Me₅)Ir(L^ph)Cl]PF₆5, [(η⁵-Cp)Ru(PPh₃)(L^ph)]PF₆, (Cp = C₅H₅, 6; C₅Me₅, 7; C₉H₇, 8) show the type-A binding mode (see text), while complexes [(η⁶-C₆Me₆)Ru(L^ph)Cl]PF₆3 and [(η⁵-C₅Me₅)Rh(L^ph)Cl]PF₆4 show the type-B binding mode (see text). These differences reflect the more electron-rich character of the [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ complexes compared to the other starting precursor complexes. Binding modes of the ligand L^ph are determined by ¹H NMR spectroscopy, single-crystal X-ray analysis as well as evidence obtained from the solid-state structures and corroborated by density functional theory calculations. From the systems studied here, it is concluded that the electron density on the central metal atom of these complexes plays an important role in deciding the ligand binding sites.     

Synthesis and structural characterization of ruthenium(II) complexes bearing phosphine-pyrazolyl based tripod ligands

Phosphine-pyrazolyl based tripod ligands ROCH₂C(CH₂Pz)₂(CH₂PPh₂) (R = H, Me, allyl; Pz = pyrazol-1-yl) were efficiently synthesized and characterized. Reactions of these ligands with [Ru(η⁶-p-cymene)Cl₂]₂ afforded complexes of the type [Ru(η⁶-p-cymene)Cl₂](L) (6-8) in which the ligands exhibit κ¹-P-coordination to the metal center. Complex [Ru(η⁶-p-cymene)Cl₂{Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}] (6) underwent chloride-dissociation in CH₂Cl₂/MeCN to give complex [RuCl(η⁶-p-cymene){κ²(P,N)-Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}][Cl] (9). Complexes 6-9 demonstrated poor to moderate catalytic activity in the transfer hydrogenation of acetophenone. All these complexes were fully characterized by analytical and spectroscopic methods and their molecular structures were determined by X-ray crystallographic study.     

Synthesis and structural characterization of three dinuclear Copper(II) complexes incorporating pyrazolyl-derived ligands

Three new binuclear copper complexes of formulae $ \left[ {{\text{Cu}}_{2}^{\text{II}} {\text{Pz}}_{2}^{\text{Me3}} {\text{Br}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ (1), $ \left[ {{\text{Cu}}_{ 2}^{\text{II}} {\text{Pz}}_{2}^{\text{Ph2Me}} {\text{Cl}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ (2) and $ \left[ {{\text{Cu}}_{2}^{\text{II}} \left( {{\text{Pz}}^{\text{PhMe}} } \right)_{ 4} {\text{Cl}}_{ 4} } \right] $ (3) (Pz^Me3?=?3,4,5-trimethylpyrazole, Pz^Ph2Me?=?4-methyl-3,5-diphenylpyrazole and Pz^PhMe?=?3-methyl-5-phenylpyrazole) have been synthesized and characterized by chemical analysis, FTIR and ³¹P NMR spectroscopy and single-crystal X-ray diffraction. Complex 1 is a doubly bromo-bridged dimer, while complexes 2 and 3 are chloro-bridged dimers. The Cu(II) centers are in a distorted tetrahedral geometry for 1 and 2 and a distorted square pyramidal N₂Cl₃ environment for 3.     

Mononuclear transition metal complexes with sterically hindered carboxylate ligands: Synthesis, structural and spectral properties

The metal coordination geometry in the active site of metalloproteins are very different from the one of small inorganic complexes, due to the inflexibility of the ligand set from amino acid side chains different from freely moving ligand set in synthesis. Using the sterically hindered 2,6-di-(p-fluorophenyl)benzoate(L) ligand, a series of mononuclear Co(II), Ni(II) and Cu(II) complexes of general formula [M(L)₂(Hdmpz)₂] (where, Hdmpz = 3,5-dimethyl pyrazole) have been synthesized and characterized by the variety of spectroscopic methods. A distorted octahedral geometry in case of nickel, tetrahedral geometry for cobalt and square pyramidal in copper was observed in the X-ray studies, which also revealed that the uncoordinated oxygen atom of the carboxylate group forms intramolecular hydrogen bonding with the N-H group of the coordinated 3,5-dimethylpyrazole in case of cobalt and copper.     

Synthesis and characterization of divalent metal complexes with bipyridylamide ligands

Reaction of N-(4-pyridyl)picolinamide (4-ppa), N-(4-pyridyl)nicotinamide (4-pna), N-(4-pyridyl)isonicotinamide (4-pina), and N-(2-pyridyl)isonicotinamide (2-pina) with divalent metal salts led to the formation of six new coordination complexes. The X-ray structure of [Zn(4-ppa)₂Cl₂] (1) shows a mononuclear structure with interesting intermolecular hydrogen bonding interactions. [Zn(4-pna)(OAc)₂]_n (2), Cu(4-pna)(OTf)₂(DMF)₂]_n (3), {[Zn(4-pina)(DMF)₄](OTf)₂}_n (4), {[Fe(4-pina)(DMF)₄](OTf)₂}_n (5), and [Cu(2-pina)(OTf)₂(DMF)₂]_n (6) are one-dimensional coordination polymers with conformational differences caused by the coordination donor disposition, which demonstrates the flexibility of the pyridylamide ligands in polymeric structures. Reflectance UV-visible spectra and thermal properties of the coordination polymers are also reported.     

Synthesis and reactivity of transition metal complexes containing halogenated boryl ligands

The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO₂C₆Cl₄) ligand are reported. Crystallographic study of the methylcyclopentadienyl derivative (η⁵-C₅H₄Me)Fe(CO)₂BO₂C₆Cl₄ allows comparison of structure and bonding with related complexes of the type (η⁵-C₅R₅)Fe(CO)₂B(OR)₂ and reveals that the relative orientation of (η⁵-C₅H₄Me)Fe(CO)₂ and BO₂C₆Cl₄ moieties is influenced by intramolecular CH?O hydrogen bonding. Additionally, an alternative route to catecholboryl complexes from dilithiocatechol is reported.     

Synthesis and structural characterization of two-coordinate low-valent 14-group metal complexes bearing bulky bis(amido)silane ligands

A series of germylene, stannylene and plumbylene complexes [η(2)(N,N)-Me(2)Si(DippN)(2)Ge:] (3a), [η(2)(N,N)-Ph(2)Si(DippN)(2)Ge:] (3b), [η(2)(N,N)-Me(2)Si(DippN)(2)Sn:] (4), [η(2)(N,N)-Me(2)Si(DippN)(2)Pb:](2) (5a), and [η(2)(N,N)-Ph(2)Si(DippN)(2)Pb:] (5b) (Dipp = 2,6-iPr(2)C(6)H(3)) bearing bulky bis(amido)silane ligands were readily prepared either by the transamination of M[N(SiMe(3))(2)](2) (M = Sn, Pb) and [Me(2)Si(DippNH)(2)] or by the metathesis reaction of bislithium bis(amido)silane [η(1)(N),η(1)(N)-R(2)Si(DippNLi)(2)] (R = Me, Ph) with the corresponding metal halides GeCl(2)(dioxane), SnCl(2), and PbCl(2), respectively. Preliminary atom-transfer chemistry involving [η(2)(N,N)-Me(2)Si(DippN)(2)Ge:] (3a) with oxygen yielded a dimeric oxo-bridged germanium complex [η(2)(N,N)-Me(2)Si(DippN)(2)Ge(μ-O)](2) (6). All complexes were characterized by (1)H, (13)C, (119)Sn NMR, IR, and elemental analysis. X-ray single crystal diffraction analysis revealed that the metal centres in 3b, 4, and 5b are sterically protected to prevent interaction between the metal centre and the nitrogen donors of adjacent molecules while complex 5a shows a dimeric feature with a strong intermolecular Pb···N interaction.     

Synthesis and structural characterization of Ni(II) complexes containing a heterocyclic NO donor ligand

Five novel nickel(II) complexes have been successfully synthesized with a heterocyclic ligand, Opdac, [Ni(Opdac)₂]Cl₂ (1), [Ni(Opdac)₂(CH₃OH)₂]Br₂(CH₃OH)₂ (2), [Ni(Opdac)₂]I₂ (3), [Ni(Opdac)₂NO₃]NO₃ (4) and [Ni(Opdac)₂ClO₄]ClO₄ (5) where Opdac = 4-(1-H-1,3-benzimidazole-2-yl)-1,5-dimethyl-2-phenyl-1-2-dihydro-3-H-pyrazol-3-one. All the complexes were characterized by elemental analysis, molar conductivity, CHN analysis, magnetic susceptibility measurements, spectroscopic studies and TG/DTA methods. In all the complexes, Opdac acts as a bidentate ligand coordinating to Ni(II) ion via the benzimidazole imine nitrogen and the pyrazolone oxygen atoms. The complexes 1 and 3 have a tetrahedral geometry while 2, 4 and 5 have an octahedral geometry around the Ni(II) center.     

Synthesis and characterisation of group nine transition metal complexes containing new mesityl and naphthyl based azaindole scorpionate ligands

Two novel boron-based flexible scorpionate ligands based on 7-azaindole, Li[HB(azaindolyl)(2)(1-naphthyl)] and Li[HB(azaindolyl)(2)(mesityl)] {Li[(Naphth)Bai] and Li[(Mes)Bai] respectively}, have been prepared (mesityl = 2,4,6-trimethylphenyl). These salts have been isolated in two forms, either as dimeric structures which contain bridging hydride interactions with the lithium centres or as crystalline material containing mono nuclear bis-acetonitrile solvates. The newly formed ligands have been utilised to prepare a range of group nine transition metal complexes with the general formula [M(COD){κ(3)-NNH-HB (azaindolyl)(2)(Ar)}] (where M = rhodium, iridium; Ar = 1-naphthyl, mesityl; COD = 1,5-cyclooctadiene) and [Rh(NBD){κ(3)-NNH-HB (azaindolyl)(2)(Ar)}] (where NBD = 2,5-norbornadiene; Ar = 1-naphthyl, mesityl). These new complexes have been compared to the previously reported compounds which contain the related scorpionate ligands Li[HB(azaindolyl)(2)(phenyl)] and K[HB(azaindolyl)(3)] {Li[(Ph)Bai] and K[Tai] respectively}. Structural characterisation of the complexes [Rh(COD){κ(3)-NNH-HB (azaindolyl)(2)(mesityl)}], [Ir(COD){κ(3)-NNH-HB (azaindolyl)(2)(mesityl)}] and [Rh(NBD){κ(3)-NNH-HB (azaindolyl)(2)(naphthyl)}] confirm the expected κ(3)-NNH coordination mode for these new ligands. Spectroscopic analysis suggests strong interactions of the B-H functional group with the metal centres in all cases.     

Synthesis of new ligands for transition metal complexes: menthyl- and neomenthyl-cyclopentadienes

Syntheses of (?)-menthylcyclopentadiene (MCp) and (+)-neomenthyl cyclopentadiene (NMCp) from (?)-menthol are described. These chiral ligands have been used to prepare (η⁵-MCp)₂TiCl₂, (η⁵-NMCp)₂, TiCl₂, (η⁵-MCp)₂ZrCl₂, (η⁵-NMCp)₂ZrCl₂, (η⁵-Cp)(η⁵-MCp)TiCl₂ and (η⁵-Cp)(η⁵-NMCp)TiCl₂. The structure and absolute configuration of (η⁵-Cp)(η⁵-MCp)TiCl₂ has been established by X-ray analysis.     

Synthesis and structural characterization of metal complexes based on pyrazole/imidazolium chlorides

A series of imidzoalium salt, L · HCl, for the potentially bidentate pyrazole/N-heterocyclic carbene was synthesized. Reactions of a 2:1 mixture between L · HCl bearing bulky N-substitution and Ag₂O produced Ag(L)Cl, whereas a novel compound with unique stoichiometry AgL₂(AgCl)_0.5Cl was produced from L · HCl bearing N-methyl group under identical condition. Reactions of L · HCl with PdCl₂ produced zwitterionic Pd^IICl₃L · H. Selected structural determinations on L · HCl, Ag(L)Cl, AgL₂(AgCl)_0.5Cl, and Pd^IICl₃L · H revealed intriguing crystal chemistry in which the less-stable gauche rotamers were obtained exclusively. A preliminary application of the zwitterionic complexes, Pd^IICl₃L · H, in Heck coupling reaction of aryl bromide with n-butyl acrylate shows effective activity.     

Synthesis,structural characterization,and photocatalytic study of transition metal coordination polymers constructed from mixed ligands

Three 3-D coordination polymers, [Cu(cca)(4,4′-bipy)]_n (1), [Co₃(pda)₃(1,10′-phen)₂]_n (2), and [Co(pda)(1,10′-phen)]_n (3), have been synthesized from 4-carboxycinnamic acid (cca), 1,4′-phenylenediacrylic acid (pda), 4,4′-bipyridine (4,4′-bipy), 1,10′-phenanthroline (1,10′-phen), and Cu and Co salts under different conditions. The X-ray crystal structures of these three complexes are presented. Complex 1 exhibits a threefold 3-D α-Po interpenetration network. Complex 2 with a 3-D framework with six-connected single α-Po framework constructed from Co₃ unit has been synthesized and characterized. Complex 3 shows a 3-D framework with bcu topology composed of 1-D rod-shaped secondary building units. Furthermore, the photocatalytic properties of 2 were studied. When excited by UV light, 2 exhibits photocatalytic activity, in 300?min, about 71% Rhodamine B decomposes.     

Synthesis, structural characterization and anion-sensing studies of metal(II) complexes based on 3,3',4,4'-oxydiphthalate and N-donor ligands

Using a multicarboxylate ligand, 3,3',4,4'-oxydiphthalic acid (H(4)ODPA), and N-donor ligands, five metal(II)-ODPA complexes formulated as Cu(4)(ODPA)(2)(L1)(4)(H(2)O)(10)·2H(2)O (L1 = 4-(2-(pyridin-4-yl)vinyl)pyridine) (1), Co(H(2)ODPA) (L1)(H(2)O) (2), Zn(2)(ODPA)(2)(H(2)PIP)(2)·H(2)O (PIP = 1,3-bis(4-piperidinyl)propane) (3), Mn(2)(ODPA)(phen)(H(2)O)(2) (phen = phenanthroline) (4) and Cu(2)(H(2)ODPA)(2)(phen)(4)·H(2)O (5) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 shows a three dimensional (3D) framework with an unprecedented (4.6(4).8)(2)(4(2).6(4)) topology generated by the polycatenation of 2D layers. Complex 2 exhibits a uninodal 4-connected 3D architecture with 6(5)8-cds topology. Complex 3 shows a uninodal 2D layer with 4(4)-sql topology. Complex 4 has a binodal (4,6)-connected non-interpenetrated 3D architecture with (3.4(3).5.6)(3(2).4(3).5(4).6(4).7(2)) topology. Complex 5 is a mononuclear Cu(II) complex. Complexes 1 and 5 can irreversibly and reversibly detect SCN(-), Cl(-), Br(-) and I(-) in water, respectively. Complexes 2-4 are not feasible candidates for colorimetric detection of anions in aqueous solution. The metal(II) species and the structure of the metal complex play important roles in the colorimetric detection.