EPR study on the ligand-exchange reaction between bis(diethyldiselenocarbamato)copper(II) and bis(octyldithiocarbonato)copper(II)

EPR study on the ligand-exchange reaction between bis(diethyldiselenocarbamato)copper(II), Cu(Et2dsc)2, and bis(octyldithiocarbonato)copper(II), Cu(octxant)2, in CH2Cl2, CHCl3, CCl4, C6H6 and C6H5.CH3 is reported for the first time. Mixing of equimolar amounts of the parents (chromophores CuSe4 and CuS4, respectively) in C6H6, C6H5.CH3 and CH2Cl2 makes EPR signals of both parents superimposed by the spectrum of a mixed-chelate Cu(xant)(dsc) complex (chromophore CuS2Se2). A new additional EPR spectrum appears in CHCl3 or CCl4 due to a five-coordinate mixed-ligand complex with the chromophore Cu(S3Se)S as follows by comparing the g-values of parents and mixed-ligand complexes. The appearance of this complex could be explained having in mind donor-acceptor properties of complexes, solvents and the resultant reaction of Cu(octxant)2 with the ester of diselenocarbamic acid yielded in Cu(Et2dsc)2 destruction by CCl4 or CHCl3.     

EPR study on ligand-exchange reaction between bis(diethyldiselenocarbamato)copper(II) and some bis(acetylacetonato)copper(II) complexes

The paper is a study on the formation and properties of mixed-chelate copper(II) complexes, in which one ligand is strongly covalently bound diselenocarbamate (dsc), and the other belongs to a series of differently substituted acetylacetonates (acac), all forming weak covalent bonds. Thenoyltrifluoro- and trifluoro- substituted acetylacetonates only partly form mixed-chelate complexes, stable in toluene, benzene or dichloromethane, but gradually decomposing in chloroform or carbontetrachloride by analogy with Cu(Et(2)dsc)(2) behavior in these solvents. Hexafluoro-acetylacetonato copper(II) completely turns into a mixed-chelate Cu(dsc)(hfacac), which remains unchanged for more than 8 months of monitoring in all solvents used. The stability of Cu(dsc)(hfacac) is attributed to the reduced remaining negative charge on selenium atom embarrassing the formation of weak D-A complex with haloalkanes. The obtained EPR parameters suggest significant lowering of the contribution of the 4s AO of copper(II) in the mixed-chelate complexes. It is shown that Cu(acac)(2) does not react with Cu(Et(2)dsc)(2).     

Template reactions with polynuclear complexes. The reaction of octachlorodimolybdate(II) with 2-aminobenzaldehyde

The binuclear molybdenum(II) anion [Mo₂Cl₈]^4? acts as a template for the self-condensation of 2-aminobenzaldehyde. The dimolybdenum unit is retained in the molybdenum(IV) product, [Mo₂(A)₂(H₂O)⁴⁺.4Cl^?, where A is a macrocyclic tetradentate ligand containing two Schiff base nitrogen donors. The product forms as two isomers, whose ¹H nmr spectra are discussed.     

Cu(Ⅱ)脱乙酰壳聚精配位聚合物的配位数

IR,ESR和XPS的测试结果表明,脱乙酰壳聚糖(简记CS)膜在铜氨水溶液浸渍过程中Cu(Ⅱ)既与CS发生配位反应形成Cu(Ⅱ)-CS配位聚合物,也产生吸附作用.ESR谱示出CuCl_2·2H_2O与Cu(Ⅱ)-CS膜中的Cu(Ⅱ)均含有一个单电子,可以利用XPS的Shake-up效应研究Cu(Ⅱ)-CS配位聚合物的配位数,所得结果为4.又以同样的方法研究Cu(Ⅱ)-聚乙烯醇(简记PVA)配位聚合物的配位数,发现Cu(Ⅱ)是以低自旋状态的dsp~2杂化空轨道与PVA的羟基氧配位,其配位数也是4,这与资料所报道的一致,从而间接地验证了此方法研究Cu(Ⅱ)-CS配位聚合物配位数的可靠性.     

Coordination compounds of palladium(II) and platinum(II) with benzotriazoles

Summary The nitrogen-donor ligands 1-methylbenzotriazole (1Mebta), 5-methylbenzotriazole (5MebtaH), 5-chlorobenzotriazole (5ClbtaH) and 5-nitrobenzotriazole (5NO₂btaH) react with palladium(II) and platinum(II) to give cis-[PdL₂Cl₂], cis-[PtL₂Cl₂] (L = 1Mebta, 5MebtaH, 5ClbtaH or 5NO₂btaH), [Pt(5ClbtaH)₄]Cl₂, [Pd-(5MebtaH)Cl₂]₂, [Pd(5ClbtaH)Cl₂]₂ and [Pd(5NO₂btaH)-Cl₂]₂. The complexes were characterized by physicochemical and spectroscopic methods. The benzotriazoles act as monodentate ligands binding through N(3). Monomeric square planar structures are assigned for the 12 complexes and [Pt(5ClbtaH)₄]Cl₂ in the solid state. Centrosymmetric, chloro-bridged, dinuclear square planar structures of C_2h symmetry are proposed for the 11 palladium(II) compounds.     

High-performance ligand-exchange liquid chromatography (HPLEC) of aromatic amines with copper(II), nickel(II) and zinc(II) loaded chelating silica gel columns

Summary An 8-hydroxyquinoline, 8-hydroxy-5-sulphonic-acid-quinoline and a 2-amino-1-cyclopentene-1-dithiocarboxylic acid silica gel, loaded with copper(II), nickel(II) or zinc(II) were examined for the separation of some aromatic amines in the normal phase mode. All phases studied interact strongly with the sample compounds, but the presence of cations increases the selectivity of the columns drastically in some cases. Nickel(II) or zinc(II) loading proved to be better than copper(II) loading, because with these ions strong peak broadening and disturbances of the baseline are avoided. Endcapping of the chelating silica gels was indispensable in order to obtain reasonable efficiencies.     

Coordination insertion reactions of acrylonitrile into Pd-H and Pd-methyl bonds in a diimine-palladium(II) system

Acrylonitrile (AN) displaces the ethyl ether ligand of the cationic complex [Pd(N-N)Me(Et₂O)]⁺ (N-N = (2,6-(i-Pr)₂C₆H₃)-NCMeCMeN-(2,6-(i-Pr)₂C₆H₃)) to form the N-bonded AN complex [Pd(N-N)Me(AN)]⁺, which exists as two interconverting rotamers. On standing or heating, [Pd(N-N)Me(AN)]⁺ undergoes 2,1-insertion to give [Pd(N-N)(CH(CN)CH₂Me)(AN)]⁺, which undergoes β-hydrogen elimination to give the intermediate hydride, [Pd(N-N)H(AN)]⁺, which in turn inserts AN to give the cyanoethyl complex [Pd(N-N)(CH(CN)Me)]⁺. Dimerization of the [Pd(N-N)(CH(CN)CH₂CH₃)]⁺ moiety via bridging nitrile groups also occurs, giving the dicationic species . Although [Pd(N-N)Me(AN)]⁺ does behave as a typical Brookhart ethylene polymerization catalyst, it does not catalyze AN polymerization and in fact added AN suppresses ethylene polymerization.     

Coordination behaviour of azines towards iron(II), palladium(II) and platinum(II)

Summary The coordination behaviour of Schiff bases derived from the condensation of some of the heterocyclic aldehydes with hydrazine hydrate, towards Fe^II, Pd^II and Pt^II, has been studied. The 1:1 and 1:2 molar reactions of MCl₂ with the Schiff bases result in coloured solids which have been characterised by elemental analysis, conductance and magnetic measurements. The mode of bonding has been deduced from i.r. and n.m.r. (¹H and¹³C) studies.     

The palladium(II)-catalyzed Nazarov reaction

The PdCl(2)-catalyzed cyclization of alpha-alkoxy dienones leads to 2-hydroxycyclopentenones, whereas the Pd(OAc)(2)-catalyzed reaction leads to cross-conjugated cyclopentenones through an oxidative process. [reaction: see text]     

Coordination of uridine and adenosine to Pd(II) and Pt(II) complexes

Uridine (and thymidine) undergo proton loss at N3 and coordinate as anions to displace all water molecules from dienPd(OH₂)²⁺, dienPt(OH₂)²⁺, enPd(OH₂)₂²⁺ and enPt(OH₂)₂²⁺ to form fully substituted complexes in neutral solutions. Though favored at equilibrium at low pH, the reactions of the ligands with the Pt(II) complexes proceed slowly because of the sluggishness of Pt(II) substitutions and the small fractions of ligands with pK_a from 9.3 to 9.8 in the anionic basic form. Both dienPd(OH₂)²⁺ and dienPt(OH₂)²⁺ form two mononuclear complexes with the metal ion at N1 and N7 of adenosine and a binuclear complex with metal ions at both sites. In the mononuclear complexes dienPd(II) favors N1 over N7 coordination by 5 to 1 while dienPt(II) is nearly equally distributed between the two sites when reacting with a neutral adenosine molecule.     

Copolymerization of ethylene with polar monomers: chain propagation and side reactions. A DFT theoretical study using zwitterionic Ni(II) and Pd(II) catalysts

Calculations utilizing anionic substituted derivates of the cationic N(wedge)N--Ni(II) and Pd(II) diimine Brookhart complex have been carried out on the barriers of ethylene and acrylonitrile insertion into a M- methyl, propyl and CH(CN)Et bond for M = Ni, Pd. The possibility of side reactions such as chelate formation with the polar functionality and oligomerization of the active species after acrylonitrile insertion are explored. The diimine ring system N--N = -NR' 'CR(1)CR(2)NR' ' with R' ' = 2,6-C(6)H(3)(i-Pr)(2) and R(1),R(2) = Me was functionalized by adding one or two anionic groups (BF(3)(-), etc.) in place of i-Pr on the aryl rings or by replacing one Me diimine backbone group (R(1)) with BH(3)(-). The objective of this investigation is computationally to design catalysts for ethylene/acrylonitrile copolymerization that have activities that are comparable to that of the cationic Ni(II) diimine or at least the Pd(II) diimine Brookhart system for ethylene homopolymerization. Complexes that might meet this objective are discussed.     

Iron(II) and magnesium(II) porphyrin acid solvolysis reactions

Rate = k(M-P)(H⁺)² for a Mg²⁺ and Fe²⁺ water soluble porphyrin acid solvolysis reaction. Such rates parallel Buchler's stability index, S_i, and the kinetic stability to acid solvolysis of 2+ metal ions is Ni>Cu>Co>Zn>Fe>Mn>Mg>Cd.     

Multi‐Dimensional Cobalt(II) and Nickel(II) Coordination Polymers

A series of metal coordination polymers, [Co₂(NB)₄(bpp)₂(H₂O)]·H₂O ( 1 ), [Co₂(e,e‐trans‐chdc)(e,a‐cis‐chdc)(bpp)₂] ( 2 ), [Ni(e,e‐trans‐chdc)(bpp)(H₂O)₂] ( 3 ), [Ni₂(PDA)₂(bpp)₂(H₂O)₃]·H₂O ( 4 ), and [Ni‐(mBDC)(bpp)] ( 5 ) (NB = 3‐nitrobenzoate anion; bpp = 4,4′‐trimethylene dipyridine; chdc = cyclohexane‐1,4‐dicarboxylate anion; PDA = 1,4‐phenylenediacetate anion; mBDC = 1,3‐benzene dicarboxylate anion), were synthesized from metal ions and organic mixed‐ligands by hydrothermal reactions. The single crystal structure analysis revealed that 1, 3, and 4 were 2D sheets with bilayer (1 and 4) and 2‐fold interpenetrated layers (3), 2 is a 3D binodal (4,5)‐connected framework, and 5 is a 1D chains. The non‐covalent interactions of H‐bonds and π–π stacking caused this conformation of highly cross‐linked networks. Compounds 1‐5 were further characterized by thermal gravimetric analysis, powder X‐ray diffraction, UV‐vis, infrared, and PL spectroscopy.     

Coordination ability of 3-pyridinyl coumarins with palladium(II) and platinum(II)

The coordination ability of two 3-pyridinyl coumarins with Pd(II) and Pt(II) both in solution and in solid state is elucidated by conventional and linear-polarized IR-spectroscopy of oriented colloid suspensions in nematic liquid crystal, ¹H- and ¹³C-NMR, UV-Vis spectroscopy, positive and negative ion mass spectrometry (ESI), HPLC tandem mass spectrometry (HPLC ESI MS/MS), TGV, and DSC methods. The four metal complexes are compared with free ligands. Density functional theory calculations are performed to obtain the electronic structure and vibrational properties of the compounds to support the experimental data.     

Chiral CE of aromatic amino acids by ligand-exchange with zinc(II)-L-lysine complex

A novel method of chiral ligand-exchange CE was developed with either L- or D-lysine (Lys) as a chiral ligand and zinc(II) as a central ion. This type of chiral complexes was explored for the first time to efficiently separate either individual pairs of or mixed aromatic amino acid enantiomers. Using a running buffer of 5 mM ammonium acetate, 100 mM boric acid, 3 mM ZnSO(4) x 7H(2)O and 6 mM L-Lys at pH 7.6, unlabeled D,L-tryptophan, D,L-phenylalanine, and D,L-tyrosine were well separated, giving a chiral resolution of up to 7.09. The best separation was obtained at a Lys-to-zinc ratio of 2:1, zinc concentration of 2-4 mM and running buffer pH 7.6. The buffer pH was determined to have a strong influence on resolution, while buffer composition and concentration impacted on both the resolution and peak shape. Boric acid with some ammonium acetate was an adoptable buffer system, and some additives like ethylene diamine tetraacetic acid capable of destroying the complex should be avoided. Fine-tuning of the chiral resolution and elution order was achieved by regulating the ratio of L-Lys to D-Lys; i.e. the resolution increased from zero to its highest value as the ratio ascended from 1:0 to 1:infinitive, and L-isomers eluted before or after D-isomers in excessive D- or L-Lys, respectively.