The synthesis of original bis(Cp/Flu) ligand systems linked at the C1-bridge through a phenylene group was developed starting from difulvene precursors. These ligand platforms were utilized for the preparation of homodinuclear zirconium and hafnium bis(dichloro ansa-metallocene) complexes via a regular salt-metathesis metallation protocol. The synthesis of a heterodinuclear zirconium / hafnium bis(dichloro ansa-metallocene) was also performed, although the desired product was generated as a statistical mixture with the corresponding homodinuclear complexes. For the first time, an advanced APPI mass-spectrometric method was applied to the characterization of dinuclear bis(ansa-metallocene) complexes and their mononuclear ansa-metallocene analogues, and relevant data were obtained.
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The EH calculations accurately predicted the orientation of the imido groups relative to one another in the other complexes studied, giving a fair indication for the structure adopted. In conclusion, then, only arylimido ligands w ith substituents in the 2- and 6- positions had a clear energetic preference for the linear-linear structure. All others, including the know n bent-linear bis(phenylimido) complex 1, had no strong preference for either structure and bending is predicted to occur w ith relative ease. Thus, physical effects, like crystal packing forces, should have a dom inant effect on the structure adopted for each molecule. This notion has already been expressed by Gibson and co-workers w ho argued that imido ligands w ith angles as small as 155° could still be regarded as "linear", the small angle being due to crystal-packing forces^^.
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The colorless reaction mixture has been changed to yellow. These newly synthesized Bis (cyclopentadienyl) zirconium (iv) Bis (dialkyl and alkylene dithiophosphate) complexes are yellow colored crystalline solid, non-volatile in nature, freely soluble in common organic solvents, and extremely sensitive towards atmospheric moisture. The molecular weights of all derivatives were determined and tabulated in table 1, which indicated that all of them are in monomeric form.
not applicable to ruthenium, and more advanced probes of charge at the metal such as X- ray absorption near-edge structure (XANES) are not readily available. Wolczanski has proposed Charge Distribution via Reporters (CDVR) as a novel method to “flip” the oxidation state formalism to analyze charge distribution with metal complexes. 43 This interesting approach requires assigning a constant reference oxidation state for each metal to interrogate charge distribution in the ligands. This is most easily accomplished by analyzing IR stretching frequencies of carbon monoxide ligands. Overall, Wolczanski makes a very compelling case that the formal oxidation state for a given transition metal is largely constant across a wide range of complexes. The bis(phosphine) complexes under consideration here do not contain ligands amenable to such spectroscopic interrogation, but structural analysis of bond distances in the [N 3 ] ligands can be
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There is much interest in the investigation o f homonuclear copper alkoxide complexes stimulated by the possible applications in MOCVD and chemical sol-gel processes.37'3*-43-57"63 Until recently, efforts to prepare cuprate-oxide superconductors from alkoxide-precursor solutions suffered firom the lack o f soluble copper(II) precursors.64"6*-71 In order to synthesize new soluble Cu(II) precursor compounds for high temperature superconductors, the choice o f ligand is very important. O ne o f the largest and most important groups o f ligands is that in which the coordination to the metal ion occurs through the oxygen atom. If the oxygen atom is bonded to carbon, the resulting complexes may be divided into two classes. In the first class are complexes such as metal carboxylates, carbonates etc., which are usually stable to air and moisture and can be obtained readily. In the second class are metal alkoxides which generally have low stability to moisture and air and require the use o f oxygen-free and moisture-free synthetic techniques. This restricts the range o f complexes which may be prepared.42-72 As reported in several reviews, alkoxides can be excellent precursors for the chemical vapour deposition (CVD) o r sol-gel production o f various metal oxide products.37"38 One successful approach to improving solubility and volatility o f precursor compounds involves the use o f multidentate alkoxy ligands. For example, Cu(OCH2CH2OCH2CH2OMe)260, Cu(OCH2CH2OBu)261, BaCOCHjCHjOBuk63 are soluble in a range o f organic solvents and CuCOCHMeCHjNMe^ 62 is one o f the most volatile copperfll) alkoxides known, subliming at 60°C under vacuum. The multidentate alkoxy ligands containing -OBu, -NEt2 o r -CF3 groups appear to improve the solubility and volatility o f precursor molecules to meet MOCVD and sol-gel requirements. The ligand used in this w ork is a multidentate amino alcohol ligand, l,3-bis(dimethylamino)-2-propanol (bdmapH). The
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E ight different zirconium phenoxyimine complexes were synthesized, characterized and tested as catalysts for ethylene polymerization. The phenoxyimine compounds were prepared by condensation of substituted salicylaldehydes with aliphatic and aromatic amines, the substituted salicylaldehydes from ortho substituted phenols and paraformaldehyde. The introduction of iodo substituents was achieved either by iodination of the aldehyde component followed by condensation with amines or the iodination of the aldehyde after the condensation with amines or the iodination via condensation with iodo substituted amines. Deprotonation of the hydroxy function of phenoxyimine compounds and reaction with zirconium tetrachloride gave mononuclear bis(phenoxyimine) zirconium complexes in good yields. These complexes were activated with methylaluminoxane (MAO) and applied for ethylene polymerization. The performances of the various catalysts were compared and structure-property-relationships were discussed. Polyolefins J (2018) 5: 157-165
with a Z of 4. The molecular structures and selected bond angles and distances of both complexes are shown in Figure 2.10 and Figure 2.11. The coordination geometry of the palladium center is square planar connected to one iodo, one bis(trimethylsilyl)phosphido and two NHCs in both trans-3 or trans-5. The bond distances (Å) of Pd(1)-C(1) (2.027(4) and 2.022(6)) are identical while Pd(1)-P(1) (2.3442(12) and 2.3648(17)) are different, respectively in trans-3 and trans-5. A distortion from linearity is more seen in the angles of C(1)-Pd(1)-C(1) (171.41(13) º ) and I(1)-Pd(1)-P(1) (166.42(3) º ) in trans-3 than those of trans- 5 (176.6(2) º and 174.55(4) º ), respectively. The geometry around the P atom in trans-3 (98.53(6) º ) and trans-5 (100.68(9) º ) is distorted tetrahedral. These collected data show that n butyl substituents in trans-5 provide more free space and less distortion around palladium
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to those in polymeric copper complexes containing metal centres linked by double triazole bridges (Liu et al., 1999, 2003). The copper centres are also attached to two O atoms from a terminal oxalato anion which acts as a bidentate ligand. The O1ÐCuÐO1 i bond angle of 83.7 (1) in the ®ve-
All the complexes were screened in-vitro for their antimicrobial activity against bacteria and fungi. Iron (III) complexes analyzed for antifungal and antibacterial activities in vitro conditions. All the complexes inhibit the growth of bacteria and fungi. For this study, we used lactobacillus bacteria in curd and A. Niger, Mucer on pickle. To check the
Physically, describes the escaping tendency of electrons from an equilibrium system. The values of for the six complexes are presented in Table 8. The trend in electronic chemical potential is 5a (-3.47 eV) > 5e (-3.51eV) > 5b (-3.60 eV) > 2a (-3.78 eV) > 2e (-3.87 eV) > 2b (-3.89 eV). The largest electronic chemical potential is attributed to the most reactive complex. In conclusion the substitution decreases the reactivity. The global electrophilicity index, is a measure of the molecule’s ability to accept electrons , was approximated by
catalysis. Here, we present results of NMR- and EPR-spectroscopic studies on reduction reactions of several (SBI)Zr(IV) complexes with sodium amalgam and with diisobutylaluminum hydride, which give access to a variety of trivalent zirconocene species and on interconversion reactions of some of these Zr(III) complexes. This provides a more complete reference for studying Zr(III) products, that might arise under catalytic conditions, and offers first insights into possible mechanisms of their formation. Additionally, initial studies regarding the potential for Zr(III) species to be ‘reactivated’ to Zr(IV) precatalysts are discussed.
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condensation method of Tabushi 6 was among the first reported C-C linked tetraazamacrocyclic compounds. 7 The presence of the amide functions introduces a number of specific properties, making ligands of this type resemble oligopeptides 8 in two respects – (i) incorporation of the metal ion into the macrocyclic cavity requires deprotonation of the amide groups and hence complex formation is strongly pH-dependent; (ii) complexes thus formed show the ability to stabilize uncommon oxidation states such as Cu III and Ni III . 9 A detailed investigation carried out on L 14B confirmed formation of the stable electroneutral dicopper(II) complex under mild basic conditions and easy oxidation of the copper ions to the trivalent state in two consecutive one- electron steps separated by 110 mV. 7 However, attempts to isolate initial dicopper(II) complex as a solid were unsuccessful 10 and its structure remains unknown. Somewhat surprisingly,
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naphthalenide. In the case of reduction of ,-unsaturated group 6 carbenes, there are few reports, and these deal mainly with the use of simple reducing agents (GoÂmez-Gallego et al., 2000; ManchenÄo et al., 1999). Studies have also been extended to include potassium graphite as a reducing agent for a variety of chromium and tungsten carbenes (Sierra et al., 2002). Normally, bis-carbene complexes are produced from this reaction when quenched with 10% H 2 SO 4 , but, in the case of
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benzoxazolyl and benzimidazolyl) titanium complexes (Figure 9) shows great dependence on both heteroatom and bridging units. For example the complexes derived from the ligand systems bis(benzothiazolyl) shows the following order 1, 1-bis(benzothiazolyl) methane 37 > 1, 2- bis(benzothiazolyl) benzene 51 > 1, 2-bis(benzothiazolyl) ethane 44. The bis(benzoxazolyl, benzimidazolyl) derived titanium complexes shows the same activity order 1, 1-bis(benzoxazolyl) methane 38 > 1, 2- bis(benzoxazolyl) ethane 45 > 1, 2-bis (benzoxazolyl) benzene 52. 1, 1-bis (benzimidazolyl) methane 41 > 1, 2- bis (benzimidazolyl) ethane 48 > 1, 2-bis (benzimidazolyl) benzene 55. The similar activity order of O, N containing ligands can be attributed to the similarities between the two hetero atoms. The 1,1-bis(benzoxazolyl) methane complex 38 shows a higher activity than the 1,2-bis(benzoxazolyl) benzene complex 52 and the 1,2-bis(benzoxazolyl) ethane complex 45. They show higher activities than those obtained from the benzothiazole ligand of the same type (Figure 9). This is most probably due to extra stabilization of the active species caused by the strong electronegative oxygen atom leading to an increase in electrophilicity of the metal center.
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While the majority of metal±oxalate compounds form low- solubility polymeric structures, discrete mononuclear complexes can be formed when the oxalate bridging potential is reduced. One way to achieve this is to saturate the metal coordination sphere, either by using high oxalate/metal ratios, or by some inert capping ligand. This has been demonstrated with chelating amines and kinetically inert ions such as Cr III
Bis-hydrazine metal iminodiacetates have been synthesized by the aqueous reaction between respective metal nitrate hydrate and aqueous solution containing a mixture of iminodiacetic acid and hydrazine hydrate in an appropriate ratio. The compositions of the complexes were assigned on the basis of chemical analyses, magnetic moments, electronic absorption spectra, infrared spectra, thermal analyses and X-ray powder diffraction and found to be MNH(CH 2 COO) 2 (N 2 H 2 ) 2 where M = Co, Ni or Zn. Infrared spectra indicate the presence of both bridging bidentate
In coordination chemistry, Schiff bases have a significant role as ligands still a century after their discovery. The importance of Schiff bases and their metal complexes are important owing to their biochemical, electrochemical, analytical, antifungal, antibacterial activitiesand redox catalysts. Schiff bases with NO donors have structural similarities with natural biological systems and imports in elucidating the mechanism of transformation and racemisation reaction in biological systems due to presence of imine (-N = CH-) group, also the presence of nitrogen and oxygen donor atoms tunes the properties of the complexes to a great extent as effective and stereo specific catalysts for oxidation, reduction and hydrolysis, 2-Hydroxy Schiff bases and their metal complexes have been extensively studied and exhibit wide applications, especially in biological systems. The studies on binuclear metal complexes in which the two metal centres are held in close proximity have addressed ligand environment, redox behaviour, magnetic exchange interactions and spectroscopic properties; therefore these kinds of complexes still continue to play a very important role in our understanding of various aspects of coordination chemistry of metal. Also binuclear Schiff bases complexes have been found to be better catalysts than the mononuclear Schiff base complexesThe present situation, as described above in the field of research of metal (II) coordination compounds, has prompted us to undertake a programme of work to synthesize and characterize a series of newnovel Schiff bases derived by condensing 1, 2-bis (o/m/p-aminophenoxy) ethane with 1, 2dihydroximino -1- chlropropane along with binuclear zinc complexes.
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Most drugs used for cancer treatment are known to affect many vital organs such as liver kidney and heart. For example, cisplatin, one of the metal complexes widely used for cancer treatment, induces tissue toxicity, in particular to the kidney (Giaccone, 2000). The undesirable side effects of most of the available chemotherapeutic agents encouraged continuous research for new reagents that exhibit anti-tumor activity. We have recently reported the existence of in vivo antitumor activity for both Co and Cr complexes of bis-(4-bromobenzaldehyde-iminoacetophenone), BBIA-Co and BBIA-Cr, against Ehrlich ascites carcinoma cells (EAC) induced in mice , . We aimed in the current study to explore the biological functions of some of the vital organs including liver, kidney and heart of EAC bearing mice post treatment with either of the two complexes. Furthermore, evaluating the antioxidant status of EAC bearing mice under treatment and examining the histopathological changes in liver, kidney and heart tissues of treated animals were carried out.
For background to five-membered heterocycle ligands in compounds with metal-organic framework structures, see: Wang et al. (2010); Yu et al. (2010); He et al. (2006); Wei et al. (2010). For related complexes with mixed ligands, see: Zhai et al. (2007); Garcı´a-Couceiro et al. (2005); Prasad et al. (2002).
A series of Ru(II) arene complexes with 3-(1H-benzimidazol-2- yl)-1H- quinoxalin-2-one, bearing pharmacophoric groups of known protein kinase inhibitors and related benzoxazole and benzothiazole derivatives have been synthesized. In addition, the corresponding Os complexes of the unsubstituted ligands have also been prepared. The compounds are characterized by NMR, UV-Vis. and IR spectroscopy, ESI mass spectrometry, elemental analysis, and by X-ray crystallography. Antiproliferative activity in three human cancer cell lines (A549, CH1, SW480) was determined by MTT assays, yielding IC 50 values of 6-60 μM for three unsubstituted metal-free ligands, whereas values for the metal complexes vary in a broad range from 0.3 to 140 μM. Complexation with osmium of quinoxalinone derivatives with benzimidazole or benzothiazole results in a more consistent increase in cytotoxicity than complexation with ruthenium. For selected compounds, the capacity to induce apoptosis was confirmed by fluorescence microscopy and flow cytometric analysis, whereas cell cycle effects are only moderate 100 .
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