Spectrophotometric determination of copper as tetraphenylarsonium or tetraphenylphosphonium thiocyanate-cuprate

The spectrophotometric determination of copper(II) with thiocyanate by extraction of the tetraphenylarsonium and tetraphenylphosphonium ion-association complexes is described. The extracted complexes in chloroform have a maximum absorbance at 465 nm, obey Beer's law in the range of 3–50 ppm of copper, and are stable for at least 3 hr. The molar absorptivity of the method is 2.8 × 10³ liters mol^?1 cm^?1. The compositions of the extracted complexes were studied in solution and they are [(C₆H₅)₄X]₂[Cu(NCS)₄] (X = As, P).     

Extraction and spectrophotometric determination of niobium by tetraphenylarsonium and phosphonium chloride from a hydrochloric acid solution

The extraction of niobium(V) in the form of a chloro complex has been studied. Radiometrical and spectrophotometrical studies show that niobium(V) is extracted practically completely from a solution containing more than 9 mol dm^?3 chloride in the range of 2–5 M hydrogen ion concentration by chloroform solutions of tetraphenylarsonium (TPA) and tetraphenylphosphonium (TPP) chloride and that niobium is not extracted at chloride concentrations less than 6 mol dm^?3. The mechanism of extraction is based on the formation of the ion-associated compounds that form between the onium cation and the oxotetra-chloroniobate(V) anion. The extracted complexes in chloroform have a maximum absorbance at 282 nm (TPA) and 285 nm (TPP); they obey Beer's law in the range of 1–10 μg Nb ml^?1, and are stable for at least 24 hr. The molar absorptivity of the method is 1.33 × 10⁴ dm³ mol^?1cm^?1. The composition of the extracted species [(C₆H₅)₄X] [NbOCl₄] where X = As or P was determined spectrophotometrically, radiometrically, and by characterization of the crystalline compounds isolated.     

Titanium and Zirconium Complexes with Non‐Salicylaldimine‐Type Imine–Phenoxy Chelate Ligands: Syntheses,Structures, and Ethylene‐Polymerization Behavior

New Ti and Zr complexes that bear imine–phenoxy chelate ligands, [{2,4‐di‐tBu‐6‐(RCH=N)‐C₆H₄O}₂MCl₂] ( 1 : M=Ti, R=Ph; 2 : M=Ti, R=C₆F₅; 3 : M=Zr, R=Ph; 4 : M=Zr, R=C₆F₅), were synthesized and investigated as precatalysts for ethylene polymerization. ¹H NMR spectroscopy suggests that these complexes exist as mixtures of structural isomers. X‐ray crystallographic analysis of the adduct 1 ?HCl reveals that it exists as a zwitterionic complex in which H and Cl are situated in close proximity to one of the imine nitrogen atoms and the central metal, respectively. The X‐ray molecular structure also indicates that one imine phenoxy group with the syn C?N configuration functions as a bidentate ligand, whereas the other, of the anti C?N form, acts as a monodentate phenoxy ligand. Although Zr complexes 3 and 4 with methylaluminoxane (MAO) or [Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ displayed moderate activity, the Ti congeners 1 and 2 , in association with an appropriate activator, catalyzed ethylene polymerization with high efficiency. Upon activation with MAO at 25 °C, 2 displayed a very high activity of 19900 (kg PE) (mol Ti)^?1 h^?1, which is comparable to that for [Cp₂TiCl₂] and [Cp₂ZrCl₂], although increasing the polymerization temperature did result in a marked decrease in activity. Complex 2 contains a C₆F₅ group on the imine nitrogen atom and mediated nonliving‐type polymerization, unlike the corresponding salicylaldimine‐type complex. Conversely, with [Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ activation, 1 exhibited enhanced activity as the temperature was increased (25–75 °C) and maintained very high activity for 60 min at 75 °C (18740 (kg PE) (mol Ti)^?1 h^?1). ¹H NMR spectroscopic studies of the reaction suggest that this thermally robust catalyst system generates an amine–phenoxy complex as the catalytically active species. The combinations 1 /[Ph₃C]⁺[B(C₆F₅)₄]^?/AliBu₃ and 2 /MAO also worked as high‐activity catalysts for the copolymerization of ethylene and propylene.     

Simultaneous endo and exo Complex Formation of Pyridine[4]arene Dimers with Neutral and Anionic Guests

The formation of complexes between hexafluorophosphate (PF₆⁻) and tetraisobutyloctahydroxypyridine[4]arene has been thoroughly studied in the gas phase (ESI‐QTOF‐MS, IM‐MS, DFT calculations), in the solid state (X‐ray crystallography), and in chloroform solution (¹H, ¹⁹F, and DOSY NMR spectroscopy). In all states of matter, simultaneous endo complexation of solvent molecules and exo complexation of a PF₆⁻ anion within a pyridine[4]arene dimer was observed. While similar ternary complexes are often observed in the solid state, this is a unique example of such behavior in the gas phase.     

Kinetics of substitution at ternary titanium(IV)–cyclopentadienyl,pyronato or pyridinato–halide or alkoxide complexes

Rate laws and kinetic parameters are reported for substitution at titanium(IV) complexes Ti(LL)₂X₂, where LLH=cyclopentadiene, the 4-pyrone ethylmaltol, several 4-pyridinones, and related ligands, and X=halide or alkoxide, in acetonitrile solution at 298.2 K. Reactivities are discussed in terms of the nature of the leaving group, the entering group and the non-leaving ligand LL^?. Activation volumes of ?15 and ?12 cm³ mol^?1 have been determined for thiocyanate attack at Ti(cp)₂Cl₂ and Ti(etmalt)₂Cl₂ respectively. Substitution mechanisms are discussed in the light of the kinetic parameters obtained.     

Synthesis of the pentacarbonyl(chalcocarbonyl)chromium(0) complexes,Cr(CO)5(CX) (X = S,Se)

The arene complexes, (η⁶-C₆H₆)Cr(CO)₂(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)₅(CX) complexes in high yield. The IR and NMR (¹³C and ¹⁷O) spectra of these complexes are in complete accord with the expected C_4v molecular symmetry. Like the analogous W(CO)₅(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)₅(CNC₆H₁₁). However, while W(CO)₅(CS) undergoes stereospecific CO substitution with halide ions (Y^? to form trans-[W(CO)₄(CS)Y]^?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)₅Y]^? and trans-[Cr(CO)₄(CX)Y]^?.     

Activation of biscyclopentadienyl hydride complexes of titanium and aluminum by NH- and OH-acids in the reactions of hydrogenation of olefins. Crystal and molecular structures of {(η5−Cp)2Ti(μ−H)2AlH]μ−N(C2H4)4O]}2 and [(η5−Cp)2Ti(μ−H(2AlH]2(μ−OC2H4OMe)[(μ1:μ5−C5H4)Ti(μ5−Cp)(μ−H)]2*

The reactions of Cp₂TiH₂AlH₂·Et₂O (1) with HN(C₂H₄)₂O, HOC₂H₄OMe, and water afforded the complexes {Cp₂TiH₂AlH[μ-N(C₂H₄)₂O]}₂ (5), [Cp₂TiH₂AlH(μ-OC₂H₄OMe)]₂ (6) and (Cp₂TiH₂AlH)₂O (4), respectively. Compounds 5 and 6 are dimers containing bridging Al?E₂?Al fragments (E=N or O). Complex 6 in solution converted to the hexanuclear compound [(η⁵?Cp)₂Ti(μ?H(₂AlH]₂(μ?OC₂H₄OMe)[(μ¹:μ⁵?C₅H₄)Ti(μ⁵?Cp)(μ?H)]₂ (8). The structures of complexes 5 and 8 were established by X-ray diffraction analysis. The rates of hydrogenation of hex-1-ene were determined using compounds 4–6 and the complexes [Cp₂TiH₂AlH(NEt₂)]₂ and [Cp₂TiH₂AlH(OEt)]₂ as catalysts. The probable mechanism of hydrogenation with the participation of bimetallic hydride complexes of aluminum and titanocene is discussed.     

Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system

The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q⁺Cl^?) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)₂,nQ⁺Cl^?₍₀₎(?⁵⁰⁰ = 3.73·10⁴l mol^?1cm^?1) at about pH 5 and 2Q⁺ NiR^2-_2(o)(?⁵⁰⁰ = 8.08·10⁴ l mol^?1 cm^?1) at above pH 8.5. The extraction constant for 2Q⁺ NiR^2-_2(o) was evaluated as [2Q⁺ NiR^2-₂]₀/[NiR^2-₂] [Q⁺]² = 10^11.16 at μ = 0.1 (Na₂SO₄. Synergic extraction studies of the Ni(HR)₂ species under slightly acidic conditions show that the species is Ni(HR)₂(H₂O)₂in auqeous solution and is extracted into chloroform as the adduct Ni(HR)₂(TBP)₂ (?⁵³⁵ = 3.57·10⁴ l mol^?1 cm^?1. Based on the extraction behavior of these complexes, the structures of the Ni²⁺—PAR complexes are discussed.     

Halide and complex halogeno anions as salts of oxinato bis(η5-indenyl)titanium(IV)/zirconium(IV) chelates

Bis(η⁵-indenyl)titanium(IV) dichloride and bis(η⁵-indenyl)zirconium(IV) dichloride, when treated with 8-hydroxyquinoline (oxine) in aqueous medium form ionic derivatives of the type [(η⁵-C₉H₇)₂ML]⁺Cl^? (M = Ti(IV), Zr(IV), L is the conjugate base of oxine). A number of halide and complex halogeno anions present in aqueous solution were isolated as salts of these ionic complexes giving derivatives of the type, [(η⁵-C₉H₇)₂ML]⁺X^? (X = Br^?, I^?, ZnCl₃(H₂O)^?, CdCl₄^2?, HgCl₃^?). Conductivity measurements in nitrobenzene indicate that these complexes are electrolytes. Both the IR and ¹H NMR spectral studies demonstrate that the ligand L is chelating. Consequently there is tetrahedral coordination about the titanium(IV) or zirconium(IV) ion.     

Carbonyl complexes of molybdenum and tungsten with sulfur donors: V. Reactions of carbonyl complexes of molybdenum(0) with uninegative (X,Y)-donor ligands (X,Y = S,N, O)

The reactions of the zerovalent carbonyl complexes Mo(CO)₆ and Mo(CO)₄(bipy) with a series of uninegative bidentate (X,Y)-donor ligands (X,Y = xanthates, dithiocarbamates, o-aminophenoxide, o-aminothiophenoxide, 2-picolinate and thioacetate) lead to new anionic tetracarbonyl complex anions [Mo⁰(X,Y)(CO)₄]^?. These anions, which can be isolated as their tetraphenylphosphonium salts, contain the (X,Y)-ligand as a bidentate group. In the case of (X,Y) = monothioacetate the decarbonylated species [PPh₄][Mo^II(TA)₃] is formed. The reacions of the new complexes with allyl bromide and methyl iodide are described.     

Site‐Selective Ligand Exchange on a Heteroleptic TiIV Complex Towards Stepwise Multicomponent Self‐Assembly

A series of heteroleptic [Ti 1 ₂X]^? complexes have been selectively constructed from a mixture of Ti^IV ions, a pyridyl catechol ligand (H₂ 1 ; H₂ 1 =4‐(3‐pyridyl)catechol), and various bidentate ligands (HX) in the presence of a weak base, in addition to a previously reported [Ti 1 ₂(acac)]^? (acac=acetylacetonate) complex. Comparative studies of these Ti^IV complexes revealed that [Ti 1 ₂(trop)]^? (trop=tropolonate) is much more stable than the [Ti 1 ₂(acac)]^? complex, which allows the replacement of acac with trop on the [Ti 1 ₂(acac)]^? complex. This Ti^IV‐centered site‐selective ligand exchange reaction also takes place on a heteronuclear Pd^II? Ti^IV ring complex with the preservation of the Pd^II‐centered coordination structures. Intra‐ and intermolecular linking between two Ti^IV centers with a flexible or a rigid bis‐tropolone bridging ligand provided a tetranuclear and an octanuclear Pd^II? Ti^IV complex, respectively. These higher‐order structures could be efficiently constructed only through a stepwise synthetic route.     

Syntheses,characterizations, and antimicrobial activities of binuclear ruthenium(III) complexes containing 2-substituted benzimidazole derivatives

Binuclear ruthenium(III) complexes [RuX₃L]₂?·?nH₂O (X?=?Cl, L?=?L¹, L², L³; n?=?1, L⁴ and L⁵, X?=?Br; L?=?L³), [RuX₃L_1.5]₂?·?nH₂O (X?=?Br, L?=?L¹; n?=?0, L⁴; n?=?6 and L⁵; n?=?10), and [RuX₃L₂]₂ (X?=?Br, L?=?L²) have been isolated by treatment of hydrated RuX₃ (X?=?Cl/Br) in acetone with 2-(2′-aminophenylbenzimidazole) (L¹), 2-(3′-aminophenylbenzimidazole) (L²), 2-[(3′-N-salicylidinephenyl)benzimidazole] (L³), 2-(3′-pyridylbenzimidazole) (L⁴), and 2-(4′-pyridylbenzimidazole) (L⁵) in acetone. The complexes were characterized by elemental analysis, conductivity and magnetic susceptibility measurements, IR, electronic, EPR, and mass spectral studies. The complexes were dimeric; based on analytical and spectral studies, an octahedral geometry was proposed for the complexes. The synthesized complexes were screened against Gram-positive and Gram-negative bacteria and fungi.     

Synthesis and magnetic properties of μ-phenolato copper (Ⅱ) binuclear complexes with different exogenous bridges

The syntheses and magnetic properties are reported for a series of copper(Ⅱ) complexes prepared from a pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoyl-hydrazone) (H3L). These complexes incorporate different exogenous ions (X-) into a bridging position to form copper(Ⅱ) binuclear complexes of the formula [Cu2(H2L)X]2+, where X-= Br-(1), Cl-(2), HO-(3), C2H5O-(4) and C3H3N2- (5). The complexes have been characterized with variable temperature magnetic susceptibility (4.2-300 K) and the observed data were fit to those from a modified Bleaney-Bowers equation by least-squares method, giving the exchange integral 2J = -6.2 cm-1 for 1, -76.4 cm-1 for 2, -241.9 cm-1 for 3, -231.1 cm-1 for 4 and -343.8 cm-1 for 5. This suggested that there is an antiferromagnetic interaction between the Cu(Ⅱ) ions and the sequence of the effect of some exogenous bridging ligands on magnetic coupling is corresponding to that in spectrochemical series.     

Effect of Heme–Heme Interactions and Modulation of Metal Spins by Counter Anions in a Series of Diiron(III)‐μ‐hydroxo Bisporphyrins: Unusual Stabilization of Two Different Spins in a Single Molecular Framework

A new family of five ethene‐bridged diiron(III)‐μ‐hydroxo bisporphyrins with the same core structure but different counter anions, represented by the general formula [Fe₂(bisporphyrin)]OH ? X (X=counter anion), is reported herein. In these complexes, two different spin states of Fe are stabilized in a single molecular framework. Protonation of the oxo‐bridged dimer 1 by strong Brønsted acids such as HI, HBF₄, HPF₆, HSbF₆, and HClO₄ produces the μ‐hydroxo complexes with I₅^? ( 2 ), BF₄^? ( 3 ), PF₆^? ( 4 ), SbF₆^? ( 5 ), and ClO₄^? ( 6 ) as counter anions, respectively. The X‐ray structures of 2 and 6 have been determined, which provide a rare opportunity to investigate structural changes upon protonation. Spectroscopic characterization has revealed that the two iron(III) centers in 2 are nonequivalent with nearly high and admixed‐intermediate spins in both the solid state and solution. Moreover, the two different Fe^III centers of 3 – 5 are best described as having admixed‐high and admixed‐intermediate spins with variable contributions of S=5/2 and 3/2 for each state in the solid, but two different admixed‐intermediate spins in solution. In contrast, the two Fe^III centers in 6 are equivalent and are assigned as having high and intermediate spin states in the solid and solution, respectively. The X‐ray structures reveal that the Fe? O bond length increases on going from the μ‐oxo to the μ‐hydroxo complexes, and the Fe‐O(H)‐Fe unit becomes more bent, with the dihedral angle decreasing from 150.9(2)° in 1 to 142.3(3)° and 143.85(2)° in 2 and 6 , respectively. Variable‐temperature magnetic data have been subjected to a least‐squares fitting using the expressions derived from the spin Hamiltonians H=?2JS₁?S₂?μ?B+D[${S{{2\hfill \atop z\hfill}}}$ ?1/3S(S+1)] (for 2 , 3 , 4 , and 5 ) and H=?2JS₁?S₂ (for 6 ). The results show that strong antiferromagnetic coupling between the two Fe^III centers in 1 is attenuated to nearly zero (?2.4 cm^?1) in 2 , whereas the values are ?46, ?32.6, ?33.5, and ?34 cm^?1 for 3 , 4 , 5 , and 6 , respectively.     

Synthesis and characterization of tridentate [O−N(H)X] titanium complexes and their applications in olefin polymerization

A series of [O^?N(H)X]TiCl₃ complexes derived from (arylamino)methylene phenol are prepared. The molecular structures of the complexes are characterized by ¹H NMR, ¹³C NMR, and X‐ray analysis. Upon activation with modified methylaluminoxane (MMAO), the titanium complexes display high thermal stability and single‐site like ethylene (co)polymerization behavior at the temperatures of up to 150 °C. 1‐Octene and 1‐octadencene prove suitable to be incorporated into polyethylene backbone at 110 °C and the highest activity of 1.89 × 10⁶ g/mol(Ti)·h·atm can be achieved. The pendant group X has great influence on the catalytic behaviors of the complexes, and PPh₂ proves to be the optimal group. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2495–2503     

Preparation and Characterization of Half‐Sandwich (Pentamethylcyclopentadienyl)(triflato)titanium(IV) Complexes: Solid‐State Structural Motifs and Catalysis Studies

Half‐sandwich (pentamethylcyclopentadienyl)(triflato)titanium(IV) complexes of the type [Ti(Cp*)(TfO)₂X] (X=MeO ( 1 ), Me ( 2 ), 2,4,6‐Me₃C₆H₂O ( 5 )) or [Ti(Cp*)(o‐OC₆H₄O)(TfO)] ( 7 ) were readily synthesized via methathesis of the corresponding chloride complexes with silver triflate (Cp*=(η⁵‐1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl)). In addition, the complex 3 with X=OH was prepared by controlled hydrolysis of 2 . The solid‐state structures of these new complexes were determined by single‐crystal X‐ray‐diffraction techniques. Three different structural motifs were identified; 1, 2, 3 , and 7 are dimeric, while 5 is monomeric. The complexes were screened for their ability to stereospecifically polymerize styrene under homogeneous conditions. In the absence of activators, such as MAO (methylaluminoxane), 1 and 2 readily catalyzed the formation of atactic polystyrene; a strong dependence on the steric size of X was noted. In the presence of MAO, all of the complexes showed high activity and strong preference for the synthesis of syndiotactic polystyrene that was superior to that of [TiCl₃(Cp*)]/MAO.     

Synthesis of 1‐Methyl‐3‐aryl‐substituted Titanocene and Zirconocene Dichlorides and Crystal Structure of Bis[η5‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium Dichloride

The syntheses of a series of l‐methyl‐3‐aryl‐substituted titanocene and zirconocene dichlorides are reported. These complexes are synthesized by the reaction of 2‐ and 3‐methyl‐6, 6‐dimethylfulvenes (1:4) with aryllithium, followed by the reaction with TiCl₄·2THF, ZrCl₄ and (CpTiCl₂)₂O respectively, to give complexes 1–5. The complex [η⁵‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium dichloride has been studied by X‐ray diffraction. The red crystal of this complex is monoclinic, space group P2_t/C with unit cell parameters: a =6.973(6) × 10^?1 nm, b =36.91(2) × 10^?1 nm, c = 10.063(4) × 10^?1 nm, α=β= γ = 93.35(5)°, V = 2584(5) × 10^?3 nm³ and Z = 4. Refinement for 1004 observed reflections gives the final R of 0.088. There are four independent molecules per unit cell.     

Preparation and properties of surface-active organocobalt complexes having long-chain alkyl groups

New types of surface-active organocobaltocenium(I) complexes, η-C_nH_2n+1X-C₅H₄(ηC₅H₅)₂Co⁺Y^? and(η-C_nH_2n+1X-C₅H₄)Co⁺Y^? (n = 6–16; X not present, NHCO or OCO; Y = Cl or PF₆) were prepared and their surface character studied. (1) The critical micelle concentrations of the cobaltocenium chlorides were much lower than those of corresponding trimethylammonium-type cationic surfactants. (2) The surface-active character of the cobaltocenium chlorides in aqueous solution (and the redox potentials of the hexafluorophosphates in acetonitrile) were affected by the substituents (X) in the cyclopentadienyl groups. (3) The surface activities of the cobaltocenium salts were lost on reduction with NaBH₄ to afford (alkyl-substituted cyclopentadiene) cyclopentadienylcobalt (0) complexes which were surface-inactive but could be re-oxidized to afford the surface-active cobaltoceium(I) salts. The cobalt complexes mentioned above may be the first examples of redoxresponsive surfactants.     

Anodic stripping voltammetry with mercury electrodes in extracts of cadmium,lead, thallium and indium diethyldithiocarbamate complexes and analysis of mixtures

The selectivity of the determination of traces of cadmium, lead, thallium and indium is improved by direct coupling of liquid/liquid extraction and anodic stripping voltammetry. Metals are extracted from aqueous solution to benzene or chloroform after the addition of sodium or zinc diethyldithiocarbamate. Stripping voltammetry of Cd, Tl and Pb at a hanging mercury drop electrode or mercury film electrode is done in benzene/methanol medium (1:1) with 0.1 M NaClO₄ as supporting electrolyte. For indium, the medium is chloroform/ethanol/water (1:4:1) with 0.005 M sodium acetate/0.06 M KBr/0.06 M HCl as supporting electrolyte. The complexes in acidic solution can be decomposed by mercury (II) ions, which provides useful shifts of deposition potentials. Calibration graphs are linear at concentrations of about 10^?7 M with a detection limit of 1×10^?8 M. The method is applied to determine a single metal in the presence of a large amount (1000-fold) of interfering metal.