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Cu(I)(Py2NS) (1) is formed by addition of Cu(I) to a solution of the pyridyl-thiol ligand N-(2-mercaptopropyl)-N,N-bis(2-pyridylmethyl)amine (Py2NSH). Oxidation of complex 1 by air leads to the formation of Cu(II) sulfinate and Cu(II) sulfonate complexes, providing a model for the oxidative degeneration of copper-sulfur enzymes. Crystal structures were obtained for two Cu(II) sulfinate complexes, [Cu(II)2(Py2NSO2)2](BF4)2·2(CH3)2CO (4a) and [Cu(II)2(Py2NSO2)2(OTf)2] (4b), which were further characterized by UV-vis and EPR spectroscopy and cyclic voltammetry. Furthermore, two Cu(II) sulfonate complexes with the proposed formulas Cu(II)2(Py2NSO3)2(BF4)2 (5a) and Cu(II)2(Py2NSO3)2(OTf)2 (5b) have been isolated and characterized. Monitoring the oxidation of 1 by UV-vis indicates that the oxidation proceeds via a dinuclear Cu(II) μ-thiolate complex (3); as an intermediate an octanuclear mixed-valent Cu(I)4Cu(II)4 cluster with formula [Cu(I)4Cu(II)4(Py2NS)4(μ-OH)2(CH3CN)6](ClO4)6·2CH3CN (2) was isolated and characterized by X-ray single crystal structure determination.

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In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

Four new Ln(III) complexes (Ln = Eu, Tb) with furan-2,5-dicarboxylic acid (H2FDA) as a ligand have been synthesized and characterized in the solid state. Luminescence studies indicate that the compounds exhibit line-like luminescence characteristic of the lanthanide centre upon excitation in the ligand absorption bands. Single crystal X-ray diffraction study of {[Eu(FDA)(H2O)5]·½(FDA)·3H2O}n shows the formation of an inorganic polymer with infinite Eu-FDA chains.

The reaction of the complexes [FeCpX(CO)2] (X = Cl, Br, I) into either [FeCp(CO)(PP)]X or [FeCpX(PP)] (PP = a bidentate diphosphine ligand) is shown to be highly dependent of the phosphine ligand used. Diphosphine ligands that form stable chelates favor formation of the neutral complex, whereas diphosphine ligands that form less stable chelates favor formation of the cationic complex. Thus, with the use of dppdmp (= 1,3-bis(diphenylphosphino)-2,2-dimethylpropane) the [FeCpX(PP)] complexes (X = Cl, Br, I) are selectively formed, induced by a gem-dialkyl effect. Apart from the bidentate phosphine ligand, the halide ion present in the iron complex has a significant influence on the course of the substitution reaction.

Background: A remarkable change in porcine islet morphology was observed after infusion of the pancreas with collagenase. The aim of the present study was to quantify these morphological changes and to assess whether these changes were due to the volume expansion caused by the collagenase entering the islet or the result of its digestive effects. Methods: This study was performed in pancreata of 28 crossbred pigs. First, eight pancreata were intraductally injected with collagenase by a continuous controlled pressure of 180 mmHg. Pancreas samples before collagenase infusion were used as controls. All tissue samples, both before and after infusion, were stained with anti-insulin. To quantify the morphological change of the islets, the mean beta cell/endocrine content ratio of the infused and not-infused tissue samples was compared. In a second experiment, 20 pancreata were similarly assessed after intraductal injection with Hank's balanced salt solution (HBSS). Results: In both the collagenase- and HBSS-infused groups, mean beta cell/endocrine content ratio was lower than in the control samples. The observed decline in the beta cell/endocrine content ratio was not significantly different between collagenase- and HBSS-infused pancreata. This suggests that the lower beta cell/endocrine content ratio and thus the morphological change in the infused tissue samples is caused by volume expansion of the fluid entering the islet and that the digestive effect of collagenase plays no or only a minor role. Conclusion: Morphological changes of islets are observed after infusion of pancreata with collagenase and HBSS, most likely caused by volume expansion due to fluid entering the islets.

Oxalate from Air In light of increasing concerns about the consequences of excessive atmospheric carbon dioxide, there is demand for methods to use carbon dioxide in the preparation of more elaborate compounds. Though reactions with hydroxide salts to form carbonates tend to proceed fairly cleanly, reductive processes to form carboxylic acids, esters, and alcohols are often rather unselective. Angamuthu et al. (p. 313 ; see the news story by Service ) discovered that a copper complex exhibited remarkable selectivity in reductively coupling carbon dioxide to form oxalate through coordinative electron transfer, even in the presence of excess oxygen, normally a much more potent electron acceptor. Precipitation of the oxalate as a lithium salt and electrochemical re-reduction of the copper produced a preliminary catalytic cycle, demonstrated through six turnovers.

Complexes of the type [Pd(ligand)2](anion)2 were prepared with a series of bidentate di(o-methoxyphenyl)phosphine ligands with increasing steric bulk on the meta position of the phenyl groups: m-H (L1); m-MeO (L2); and m-Me (L3). The solid-state structure of [Pd(L2)2](OTs)2 revealed that the two ligands are symmetrically coordinated to Pd2+. In the solid state structure of [Pd(L3)2](OTs)2 however, the two ligands are unsymmetrically coordinated to Pd2+, yielding an unprecedented conformation of this bis-chelate P4Pd2+ complex. 1H-1H-COSY and NOESY analysis and a 31P-NMR simulation showed that the asymmetric structure of [Pd(L3)2](OTs)2 is retained in solution.

Vinyl polymerized norbornene has some useful properties such as good mechanical strength, optical transparency and heat resistance. Several transition metal complexes have been described in the literature as active catalysts for the vinyl polymerization of norbornene. We now report the use of three types of nickel(II) complexes with N-heterocyclic carbene (NHC) ligands in the catalytic vinyl polymerization of norbornene under a range of conditions. Specifically, two nickel complexes bearing a chelating bis(NHC) ligand, two nickel complexes bearing two chelating anionic N-donor functionalized NHC ligands as well as one diiodidonickel(II) complex with two monodentate NHC ligands were tested. The solid-state structure of bis(1,3-dimethylimidazol-2-ylidene)diiodidonickel(II), as determined by X-ray crystallography, is presented. The highest polymerization activity of 2.6 × 107 g (mol cat)−1 h−1 was observed using the latter nickel complex as catalyst, activated by methylaluminoxane. The norbornene polymers thus obtained are of high molecular weight but with rather low polydispersity.

The synthetic pathways towards Pd-II complexes of functionalized bidentate diphenylphosphane ligands of the type [Pd(ligand)(anion)(2)] and [Pd(ligand)(2)](anion)(2) have been investigated. Eighteen different ligands have been used in combination with strongly (acetate, OAc-) or weakly (tosylate, OTs-) coordinating anions, The solid-state structure of some representative complexes was determined with X-ray crystallography. It is shown that the solid-state structures are fully retained in solution, The formation of [Pd(ligand)-(anion)(2)]-type complexes was studied in detail by H-1- and P-31-NMR spectroscopy. Depending on the Ligand structure, the complex is formed instantaneously, via a polynuclear intermediate or is not formed at all. Complex formation is demonstrated to depend on the length and rigidity of the ligand backbone and on the steric bulk at the ortho position of the phenyl rings on phosphorus, It was also found that the coordinating ability of the anions can alter the structure of the kinetic and/or thermodynamic product.

A new mononuclear low-spin nickel(II) dithiolato complex, [NiL2] (1), reacts with copper iodide to form the heterooctanuclear cluster [{Ni(L)2}2(CuI)6] (2) with four trigonal-planar CuI2S and two tetrahedral CuI2S2 sites; anagostic interactions between the nickel(II) ions and aromatic protons have been demonstrated by variable-temperature NMR studies to pertain in solution.

The reaction of 1,3-dibenzylimidazolium bromide (Bn2Im · HBr) with silver(I) oxide yields the dinuclear compound {(Bn2Im)AgBr}2 as determined with X-ray crystallography. The structure turned out to differ significantly from the mononuclear complex (Bn2Im)2AgBr that was reported during our studies. It appears that the various structures are a result of different crystallization conditions. A new classification of solid-state structures of these and other silver(I) complexes containing monodentate N-heterocyclic carbenes is presented.