Coupling Interactions between Sulfurous Acid and the Hydroperoxyl Radical

Radical–molecule complexes associated with the hydroperoxyl radical (HOO) play an important role in atmospheric chemistry. Herein, the nature of the coupling interactions between sulfurous acid (H₂SO₃) and the HOO radical is systematically investigated at the B3LYP/6‐311++G(3df,3pd) level of theory in combination with the atoms in molecules (AIM) theory, the natural bond orbital (NBO) method, and energy decomposition analyses (EDA). Eight stable stationary points possessing double H‐bonding features were located on the H₂SO₃???HOO potential energy surface. The largest binding energies of ?12.27 and ?11.72 kcal mol^?1 are observed for the two most stable complexes, where both of them possess strong double intermolecular H‐bonds of partially covalence. Moreover, the characteristics of the IR spectra for the two most stable complexes are discussed to provide some help for their possible experimental identification.     

Synthesis and thermal decomposition kinetics of the complexes [Sm(o‐NBA)3bipy]2·2H2O and [Sm(o‐BrBA)3bipy]2· 2H2O

Two new complexes [Sm(o‐NBA)₃bipy]₂·2H₂O ( 1 ) and [Sm(o‐BrBA)₃bipy]₂·2H₂O ( 2 ) (where o‐NBA is o‐nitrobenzoic acid, o‐BrBA is o‐bromobenzoic acid, and bipy is 2,2′‐bipyridine) were prepared and characterized by elemental analysis, IR, UV, and molar conductance, respectively. The thermal decomposition behaviors of the two complexes were investigated by means of TG–DTG and IR techniques. The thermal decomposition kinetics was studied by using advanced double equal‐double steps method, nonlinear integral isoconversional method, and nonlinear differential isoconversional method. The kinetic parameters of the second‐step process for the two complexes were obtained, respectively. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 607–616, 2008     

Synthesis and Thermal Decomposition Kinetics of Two Dy(III) Complexes with Benzoate Derivative and 2,2′‐Bipyridine as Co‐ligands

Two Dy(III) complexes with benzoate derivative and 2,2′‐bipyridine ligands, [Dy(2,4‐DClBA)₃bipy]₂ and [Dy(o‐MOBA)₃bipy]₂·4H₂O (2,4‐DClBA=2,4‐dichlorobenzoate; o‐MOBA=o‐methoxybenzoate; bipy=2,2′‐bipyridine), were prepared and characterized by elemental analysis, infrared spectra, ultraviolet spectra and thermogravimetry and differential thermogravimetry techniques. The thermal decomposition behavior of the two complexes under a static air atmosphere was discussed by thermogravimetry, differential thermogravimetry and infrared spectral techniques. The non‐isothermal kinetics were investigated by using a double equal‐double step method, a non‐linear isoconversional integral method and a Starink method. The mechanism functions of the first decomposition step for [Dy(2,4‐DClBA)₃bipy]₂ and the second decomposition step for [Dy(o‐MOBA)₃bipy]₂·4H₂O were determined. Meanwhile, the thermodynamic parameters (ΔH^ne;, ΔG^ne; and ΔS^ne;) and kinetic parameters (activation energy E and the pre‐exponential factor A) for the two complexes were also calculated.     

Single‐Molecule‐Magnet Behavior in the Family of [Ln(OETAP)2] Double‐Decker Complexes (Ln=Lanthanide,OETAP=Octa(ethyl)tetraazaporphyrin)

Double‐decker complexes of lanthanide cations can be readily prepared with tetraazaporphyrins (porphyrazines). We have synthesized and characterized a series of neutral double‐decker complexes [Ln(OETAP)₂] (Ln=Tb³⁺, Dy³⁺, Gd³⁺, Y³⁺; OETAP=octa(ethyl)tetraazaporphyrin). Some of these complexes show analogous magnetic features to their phthalocyanine (P_c) counterparts. The Tb³⁺ and Dy³⁺ derivatives exhibit single‐molecule magnet (SMM) behavior with high blocking temperatures over 50 and 10 K, respectively. These results confirm that, in double‐decker complexes that involve Tb or Dy, the (N₄)₂ square antiprism coordination mode has an important role in inducing very large activation energies for magnetization reversal. In contrast with their P_c counterparts, the use of tetraazaporphyrin ligands endows the presented [Ln(OETAP)₂] complexes with extraordinary chemical versatility. The double‐decker complexes that exhibit SMM behavior are highly soluble in common organic solvents, and easily processable even through sublimation.     

Highly efficient and chemoselective reduction of sulfoxides using the system silane/oxo-rhenium complexes

This work reports a novel method for the reduction of sulfoxides with silanes catalyzed by high valent oxo-rhenium(V) and (VII) complexes. The catalytic system PhSiH₃/ReIO₂(PPh₃)₂ (1 mol %) proved to be highly efficient for the reduction of a wide range of sulfoxides in excellent yields under mild conditions. This novel methodology is also highly chemoselective, tolerating several functional groups such as –CHO, –CO₂R, –Cl, –NO₂, and double or triple bonds.     

1,3-Dipolar cycloaddition reactions of alkenylalkoxycarbene chromium complexes

New spiropyrazoline derivatives from the 1,3-dipolar cycloaddition of diazomethane to alkenylalkoxycarbene complexes are isolated and fully characterized as Cr(CO) ₅ complexes. Me₃SiCHN₂ reacts selectively with the CC double bond to give new pentacarbonylchromium carbene complexes.     

The multiple conformational charge states of zinc(II) coordination by 2His‐2Cys oligopeptide investigated by ion mobility‐mass spectrometry,density functional theory and theoretical collision cross sections

Whether traveling wave ion mobility‐mass spectrometry (IM‐MS), B3LYP/LanL2DZ density functional theory, and ion size scaled Lennard‐Jones (LJ) collision cross sections (CCS) from the B3LYP optimized structures could be used to determine the type of Zn(II) coordination by the oligopeptide acetyl‐His₁‐Cys₂‐Gly₃‐Pro₄‐Tyr₅‐His₆‐Cys₇ (amb₅) was investigated. The IM‐MS analyses of a pH titration of molar equivalents of Zn(II):amb₅ showed that both negatively and positively charged complexes formed and coordination of Zn(II) increased as the His and Cys deprotonated near their pKa values. The B3LYP method was used to generate a series of alternative coordination structures to compare with the experimental results. The method predicted that the single negatively charged complex coordinated Zn(II) in a distorted tetrahedral geometry via the 2His‐2Cys substituent groups, whereas, the double negatively charged and positively charged complexes coordinated Zn(II) via His, carbonyl oxygens and the C‐terminus. The CCS of the B3LYP complexes were calculated using the LJ method and compared with those measured by IM‐MS for the various charge state complexes. The LJ method provided CCS that agreed with five of the alternative distorted tetrahedral and trigonal bipyramidal coordinations for the doubly charged complexes, but provided CCS that were 15 to 31 Ų larger than those measured by IM‐MS for the singly charged complexes. Collision‐induced dissociation of the Zn(II) complexes and a further pH titration study of amb_5B, which included amidation of the C‐terminus, suggested that the 2His‐2Cys coordination was more significant than coordinations that included the C‐terminus. Copyright © 2016 John Wiley & Sons, Ltd.     

Syntheses,Characterization and Crystal Structures of Three Structurally Similar Dinuclear Schiff Base Cadmium(II) Complexes with Bridging Azide or Thiocyanate Ligands

Three novel Schiff base cadmium(II) complexes, derived from the end‐on (μ‐1,1‐N₃) azide or end‐to‐end (μ‐1,3‐NCS) thio cyanate bridges and similar tridentate Schiff base ligands, have been synthesized under similar synthetic procedures and their crystal structures determined by X‐ray diffraction methods. They are the dinuclear double end‐on azide‐bridged [Cd₂(L1)₂(N₃)₂(μ‐1,1‐N₃)₂] ( 1 ), the dinuclear double end‐on azide‐bridged [Cd₂(L2)₂(N₃)₂(μ‐1,1‐N₃)₂] ( 2 ), and the dinuclear double end‐to‐end thiocyanate‐bridged [Cd₂(L3)₂(NCS)₂(μ_1,3‐NCS)₂] ( 3 ), where L1, L2 and L3 are three similar tridentate Schiff bases obtained by condensation of 2‐pyridylaldehyde with N,N‐diethylethane‐1,2‐diamine, of 2‐pyridylaldehyde with N‐isopropylethane‐1,2‐diamine, and of 2‐pyridylaldehyde with N,N‐dimethylpropane‐1,3‐diamine, respectively. Each cadmium(II) centre in the complexes is in a distorted octahedral coordination. There is a crystallographic inversion centre in each of the complexes. The similar small ligands used as the secondary ligands in the preparation of the cadmium(II) complexes with similar Schiff bases can result in similar structures.     

Synthesis and structures of gold(I) phosphine complexes containing monoanionic selenocarbamate ester ligands

A series of mono- and dinuclear gold(I) phosphine complexes of the type [Au{SeC(OMe)NPh}(P)] [P = PPh₃, PTA, P(o-tolyl)₃, P(p-MeOC₆H₄)₃] and [Au₂{SeC(OMe)NPh}₂(μ-PP)] (PP = dppm, dppe, dppp, dppf, dppee) were prepared from the reaction of the appropriate chlorogold(I) phosphine complexes with N-phenyl-O-methylselenocarbamide in the presence of base. These new complexes were fully characterised by spectroscopic techniques and, in several cases, by X-ray crystallography. The differences in the solid-state structures of these selenium complexes were compared with those of some sulfur analogues.     

Syntheses,Crystal Structures,Thermal and Photoluminescent Properties of Four Coordination Complexes with a Hetero­cyclic Thioether Carboxylate Ligand

A series of transition metal coordination complexes, {[Cu(3‐Sptta)₂] · 1/2H₂O}_n ( 1 ), {[Cd(3‐Sptta)₂] · 1/2H₂O}_n ( 2 ), [Zn(3‐Sptta)₂(H₂O)₄] ( 3 ), and [Co(3‐Sptta)₂(H₂O)₄] ( 4 ) were synthesized under solvothermal and solvent evaporation conditions using the newly designed heterocyclic N/NS carboxylate ligand [2‐(3‐pyridyl)‐1,3,4‐thiadiazole‐5‐]‐thio‐acetate (3‐Sptta) as a main building block. Their structures were determined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses and IR spectroscopy. The four complexes exhibit structural diversity: complexes 1 and 2 exhibit similar 2D “wave‐like” double‐layer framework with two shares of mutually parallel left‐handed and right‐handed helical chains, whereas 3 and 4 present mononuclear structures. Moreover, the thermal stabilities of complexes 1 – 4 were investigated. The luminescent properties of complexes 2 , 3 and the free ligand were also studied.     

Reactions of 2-(arylazo)aniline with ruthenium substrates: Isolation, characterizations and reactivities of delocalized diazoketiminato and orthometallated Ru(II) chelates

Reactions of 2-(arylazo)aniline, HL-NH₂ [H represents the dissociable protons upon complexation and HL-NH₂ is p-RC₆H₄NNC₆H₄-NH₂; R = H for HL¹-NH₂; CH₃ for HL²-NH₂ and Cl for HL³-NH₂] with Ru(H)(CO)(PPh₃)₃Cl and Ru(CO)₃(PPh₃)₂ afforded products of compositions [(HL-NH)Ru(CO)Cl(PPh₃)₂] and [(L-NH)Ru(PPh₃)₂(CO)], respectively. All the complexes were characterized unequivocally. The X-ray structures of the complexes 4c and 5c have been determined. The cyclic volatammograms exhibited one reversible oxidative response in the range of 0.56–0.16 V versus SCE for [(L-NH)Ru(PPh₃)₂(CO)] and a quasi reversible oxidative response within 0.56–0.70 V versus SCE for [(HL-NH)Ru(CO)Cl(PPh₃)₂]. The conversion of ketones to corresponding alcohols has been studied in presence of newly synthesized ruthenium complexes.     

Synthesis and characterisation of the platinum complexes [PtCl(CClPAr)(PPh3)2] and [PtCl(CClPAr′)(PPh3)2] as potential intermediates in the preparation of phosphaalkynes

Oxidative addition reactions of Cl₂CPR (R = 2,4,6-tris(trifluoromethyl)phenyl (Ar) or 2,6-bis(trifluoromethyl)phenyl (Ar′) with Pt(PPh₃)₄ yield the cis and trans (at platinum) complexes [PtCl(ClCPAr)(PPh₃)₂] and [PtCl(ClCPAr′)(PPh₃)₂]. All starting materials and intermediates have been characterised by NMR spectroscopy. The crystal and molecular structures of the trans-platinum complexes have been determined by single-crystal X-ray diffraction at low temperature.     

Design and synthesis of new thiobarbituric acid metal complexes as potent protease inhibitors: spectral characterization,thermal analysis and DFT calculations

Five novel metal complexes of thiobarbituric acid (TBAH) have been prepared with the general formulae: [Ti(TBA)₂(H₂O)₂]Cl₂·2H₂O, [Pd(TBA)₂]·4H₂O, Na[Ag(TBA)₂(H₂O)₂]·4H₂O, [Hg(TBA)₂(H₂O)₂] and [Ce(TBA)₂(H₂O)₃]SO₄·H₂O. The complexes have been fully characterized employing physicochemical and diverse spectroscopic techniques (IR, UV–Vis, mass and ¹H NMR) as well as thermal analysis. Elemental analyses and spectroscopic data have showed that the stoichiometries of all complexes were 1:2. Thermal analysis measurements indicated that the complexes have good thermal stability. Density functional theory calculations were carried out at the B3LYP levels of theory with a double basis set, LANL2DZ basis set for titanium, palladium, cerium atoms, or LANL2MB basis set for silver, mercury atoms and 6-31+G(d,p) basis set for the other atoms. The optimized geometry of the ligand and its complexes was obtained based on the optimized structures. The ligand and its metal complexes act as protease inhibitors and repressed their enzymatic activity significantly.     

Kinetic Analyis of TG Data XXXV. Spectroscopic and thermal studies of some cobalt(III) chelates with ethylenediamine

A number of 30 [Co(en)₃ ]Y₃ , [Co(en)₂ X₂ ]Y and [Co(en)₂ X(amine)]Y₂ type complexes (X =Cl, Br; Y =Cl, Br, I, NCO, NCS, NO₃ , ClO₄ , etc.; amine =aromatic and alkylamines) were obtained from trans-[Co(en)₂ Cl₂ ]Cl by double decomposition and by substitution reactions, respectively. The structure of the complexes was proved by means of far and middle FTIR spectra. The thermal decomposition was studied by TG, DTA and DSC measurements. Mass spectra were also recorded. In the case of [Co(en)₃ ]Y₃ complexes the nitrate, perchlorate and dimesoperiodates decompose suddenly, frequently explosion like. The halides and thiocyanates seem to substitute an ethylenediamine ligand, yielding a rather unstable intermediate. The pyrolysis of [Co(en)₂ X₂ ]Y type derivatives yields no relatively stable intermediates, but the decomposition temperatures may be correlated with the nature of Y and with the cis or trans configuration of the compound. With the [Co(en)₂ X(amine)]Y₂ type complexes one observes the formation of [Co(en)₂ XY]Y as intermediate product. From the TG curves kinetic parameters were derived for some dehydration and deamination processes, by using the nomogram method. The validity of a non-linear kinetic compensation law was observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A potentiometric and calorimetric study of the polynuclear and mononuclear complexes of nickel(II) with thioglycolic acid

The complex formation between nickel(II) and thioglycolic acid was studied by a potentiometric method at 25°C and in 0.5 M KN0₃. In solution two polynuclear complexes, B₃A₄ and B₄A₆, and one mononuclear complex, BA₂, were detected, and the following stability constants were determined: log β_3.4=32.219; log β_4.6=49.157; log β_1.2=12.759. The enthalpies of formation of the double (Ni-S-Ni) and single (Ni-S) bond were determined by calorimetric titration, and were found to be -5 kcal mol^-1 and -1.5 kcal mol^-1, respectively. It was shown that the stability of the polynuclear complexes is due to the enthalpy term, whereas the stability of the mononuclear complexes can be ascribed principally to the entropy term.     

Amidinato Germylene‐Zinc Complexes: Synthesis,Bonding, and Reactivity

Despite the explosive growth of germylene compounds as ligands in transition metal complexes, there is a modicum of precedence for the germylene zinc complexes. In this work, the synthesis and characterization of new germylene zinc complexes [PhC(NtBu)₂Ge{N(SiMe₃)₂}→ZnX₂]₂ (X= Br ( 2 ) and I ( 3 )) supported by (benz)‐amidinato germylene ligands are reported. The solid‐state structures of 2 and 3 have been validated by single‐crystal X‐ray diffraction studies, which revealed the dimeric nature of the complexes, with distorted tetrahedral geometries around the Ge and Zn center. DFT calculations reveal that the Ge–Zn bonds in 2 and 3 are dative in nature. The reaction of 2 with elemental sulfur resulted in the first structurally characterized germathione stabilized ZnBr₂ complexes PhC(NtBu)₂Ge(=S){N(SiMe₃)₂}→ZnBr₂ ( 5 ). Therefore, the Ge=S in 5 is in‐between Ge–S single and Ge=S double bond length, owing to the coordination of a sulfur lone pair of electrons to ZnBr₂.     

Synthesis and crystal structures of cyclodiazastannoxides fused cyclopentadienyl M-Sn (M = Mo, W) bonded organometallic heterocycle

The condensation reaction of CH₃COC₅H₄M(CO)₃SnCl₃ (M = Mo or W) with PyCONHNH₂ (Py = 2,3,4-pyridyl or 2-pyridylmethyl) in mild conditions yields cyclodiazastannoxides fused cyclopentadienyl M-Sn bonded organometallic heterocycle {μ-[C₅H₄(CH₃)CN-NC(O)PyH]M(CO)₃SnCl₃}. The similar reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with ArCONHNH₂ (Ar = 2-furanyl) gives complexes μ-[C₅H₄(CH₃)CN-NC(O)Ar]M(CO)₃SnCl₂(H₂O), in which the water molecule can be replaced by other N-donor ligands, such as pyridine or 4,4-bipyridine. Arene-bridged organometallic heterocyclic complexes μ-{[C₅H₄(CH₃)CN-NC(O)]₂C₆H₄}{M(CO)₃SnCl₂(Solvent)}₂ have also been prepared by the reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with terephthaloyl hydrazine. In these new organometallic heterocyclic complexes, it seems that the tin atom prefers to be six-coordinate through absorbing the chloridion or solvent molecules.     

Seeking new metalloligands: Synthesis and reactivity of palladacycles with pyridine and pyrimidine rings

Treatment of the Schiff base ligands 4-(NC₅H₄)C₆H₄C(H)N[2′-(OH)C₆H₄] (a), 3,5-(N₂C₄H₃)C₆H₄C(H)N[2′-(OH)-C₆H₄] (b) and 3,5-(N₂C₄H₃)C₆H₄C(H) N[2′-(OH)-5′-^tBuC₆H₃] (c) with palladium (II) acetate in toluene gave the poly-nuclear cyclometallated complexes [Pd{4-(NC₅H₄)C₆H₃C(H)N[2′-(O)C₆H₄]}]₄ (1a), [Pd{3,5-(N₂C₄H₃)C₆H₃C(H)N[2′-(O)-C₆H₄]}]₄ (1b) and [Pd{3,5-(N₂C₄H₃)C₆H₃C(H)N[2′-(O)-5′-^tBuC₆H₃]}]₄ (1c) respectively, as air stable solids, with the ligand acting as a terdentate [C,N,O] moiety after deprotonation of the –OH group. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species [Pd{4-(NC₅H₄)C₆H₃C(H) N[2′-(O)C₆H₄]}(PPh₃)], (2a), [Pd{3,5-(N₂C₄H₃)C₆H₃C(H) N[2′-(O)C₆H₄]}(PPh₃)], (2b) and [Pd{3,5-(N₂C₄H₃)C₆H₃C(H)N[2′-(O)-5′-^tBuC₆H₃)}(PPh₃)], (2c) in which the polynuclear structure has been cleaved and the coordination of the ligand has not changed [C,N,O]. When the cyclometallated complexes 1b and 1c were treated with the diphosphines Ph₂P(CH₂)₄PPh₂ (dppb), Ph₂PC₅H₄FeC₅H₄PPh₂ (dppf) and Ph₂P(CH₂)₂PPh₂ (t-dppe) in a 1:2 molar ratio the dinuclear cyclometallated complexes [{Pd[3,5-(N₂C₄H₃)C₆H₃C(H)N{2′-(O)C₆H₄}]}₂(μ-Ph₂P(CH₂)₄PPh₂)], (3b), [{Pd[3,5-(N₂C₄H₃)C₆H₃C(H) N{2′-(O)-5′-^tBuC₆H₃}]}₂(μ-Ph₂P(CH₂)₄PPh₂)], (3c), [{Pd[3,5-(N₂C₄H₃)C₆H₃C(H)N{2′-(O)C₆H₄}]}₂(μ-Ph₂P(η⁵-C₅H₄)Fe(η⁵-C₅H₄)PPh₂)], (4b), [{Pd[3,5-(N₂C₄H₃)C₆H₃C(H) N{2′-(O)-5′-^tBuC₆H₃}]}₂(μ-Ph₂P(η⁵C₅H₄)Fe(η⁵C₅H₄)P-Ph₂)], (4c) and [{Pd[3,5-(N₂C₄H₃)C₆H₃C(H)N{2′-(O)-5′-^tBuC₆H₃}]}₂(μ-Ph₂P(CHCH)PPh₂)], (5c) were obtained as air stable solids.     

Synthesis,Structure, and Supramolecular Chemistry of Three Azide Manganese Complexes with 2, 6‐Bis(benzimidazol‐2‐yl)pyridine

Three azide complexes with the tridentate ligand 2, 6‐bis(benzimidazol‐2‐yl)pyridine (H₂BBIP) were synthesized and their complicated supramolecular interactions were investigated with single‐crystal X‐ray diffraction. Interestingly, the complexes are assembled by bifurcated hydrogen bonding, double helical π–π stacking, or anion–π stacking interactions of the benzimidazole rings by tuning the reaction conditions (temperature, ratio, solvent). Complex 1 is a mononuclear compound, namely, Mn(H₂BBIP)N₃(CH₃O) · CH₃OH. In its 3D supramolecular network, the nitrogen atom of the azide anion is acting as hydrogen bonding bifurcated acceptor. Complex 2 is a dinuclear compound, namely, Mn₂(H₂BBIP)₂(N₃)₂ · (H₂O)_0.5. The dinuclear unit is connected by intramolecular π–π stacking interactions. Furthermore, double helical π–π stacking interactions in the benzimidazole rings are observed. Complex 3 , Mn₂(H₂BBIP)₂(N₃)₂ · CH₃OH, can be formulated as a pseudopolymorph of complex 2 , which exhibits intramolecular π–π stacking interactions as well as anion–π interactions in the dinuclear unit.