Synthesis and applications of multifunctional N-pyrrolyl phosphine ligands

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Diphosphines possessing electronically different donor groups : synthesis and coordination chemistry of the unsymmetrical di(N-pyrrolyl)phosphino-functionalized dppm analogue Ph2PCH2P(NC4H4)2

The unsymmetrical diphosphinomethane ligand Ph2PCH2P(NC4H4)(2) L has been prepared from the reaction of Ph2P-CH2Li with PCI(NC4H4)(2). The diphenylphosphino group can be selectively oxidized with sulfur to give Ph2P(S)CH2P(NC4H4)(2) 1. The reaction of L with [MCl2(cod)] (M = Pd, Pt) gives the chelate complexes [MCl2(L-kappa(2)P,P')] (2, M = Pd; 3, M = Pt) in which the M-P bond to the di(N-pyrrolyl)phosphino group is shorter than that to the corresponding diphenylphosphino group. However, the shorter Pd-P bond is cleaved on reaction of 2 with an additional 1 equiv of L to give [PdCl2(L-kappa(1)P)(2)] 4. Complex 4 reacts with [PdCl2(cod)] to regenerate 2, and with [Pd-2(dba)(3)].CHCl3 to give the palladium(l) dimer [Pd2Cl2(mu-L)(2)] 5, which exists in solution and the solid state as a 1:1 mixture of head-to-head (HH) and head-to-tail (HT) isomers. The palladium(11) dimer [Pd2Cl2(CH3)(2)(mu-L)(2)] 6, formed by the reaction of [PdCl(CH3)(cod)] with L, also exists in solution as a mixture of HH and HT isomers, although in this case the HT isomer prevails at low temperature and crystallizes preferentially. Complex 6 reacts with TIPF6 to give the A-frame complex [Pd-2(CH3)(2)(mu-Cl)(mu-L)(2)]PF6 7. The reaction of L with [RuCp*(mu(3)-Cl)](4) leads to the dimer [(RuCp2*)-Cp-2(mu-Cl)(2)(mu-L)] 8, for which the enthalpy of reaction has been measured. The reaction of L with [Rh(mu-Cl)(cod)](2) gives a mixture of compounds from which the dimer [Rh-2(U-Cl)(cod)(2)(U-L)]PF6 9 can be isolated. The crystal structures of 2.CHCl3, 3.CH2O2, 4, 5.1/4CH(2)Cl(2), 6, 7.2CH(2)Cl(2), 8, and 9.CH2Cl2 are reported

Method for the Detection of the Cleaved Form of Shiga Toxin 2a Added to Normal Human Serum

none8siThe pathogenesis of Escherichia coli-induced hemolytic uremic syndrome (eHUS) caused by infections with pathogenic Shiga toxin (Stx) producing E. coli (STEC) is centered on bacterial (e.g., Stx) and host factors (circulating cells, complement system, serum proteins) whose interaction is crucial for the immediate outcome and for the development of this life-threatening sequela. Stx2a, associated to circulating cells (early toxemia) or extracellular vesicles (late toxemia) in blood, is considered the main pathogenic factor in the development of eHUS. Recently, it was found that the functional properties of Stx2a (binding to circulating cells and complement components) change according to modifications of the structure of the toxin, i.e., after a single cleavage of the A subunit resulting in two fragments, A1 and A2, linked by a disulfide bridge. Herein, we describe a method to be used for the detection of the cleaved form of Stx2a in the serum of STEC-infected or eHUS patients. The method is based on the detection of the boosted inhibitory activity of the cleaved toxin, upon treatment with reducing agents, on a rabbit cell-free translation system reconstituted with human ribosomes. The method overcomes the technical problem caused by the presence of inhibitors of translation in human serum that have been stalled by the addition of RNAase blockers and by treatment with immobilized protein G. This method, allowing the detection of Stx2a at concentrations similar to those found by ELISA in the blood of STEC-infected patients, could be a useful tool to study the contribution of the cleaved form of Stx2a in the pathogenesis of eHUS.openRocchetti L.; Munari B.; Varrone E.; Porcellini E.; Orth-Holler D.; Wurzner R.; Carnicelli D.; Brigotti M.Rocchetti L.; Munari B.; Varrone E.; Porcellini E.; Orth-Holler D.; Wurzner R.; Carnicelli D.; Brigotti M

Synthesis and isomerisation of two metallated N,O-complexes of ruthenium:Models for the Murai reaction

Two isomers of the N,O-coordinated acetylpyrrolyl complex [Ru(PPh 3)2(CO)(NC4H3C(O)CH3)H] {cis-N,H (1) and trans-N,H (2)} have been prepared as models for catalytic intermediates in the Murai reaction. Complex 2 isomerises to 1 upon heating via a dissociative pathway (ΔH‡ = 195 ± 41 kJ mol-1; ΔS‡ = 232 ± 62 J mol -1 K-1); the mechanism of this process has been modeled using density functional calculations. Complex 2 displays moderate catalytic activity for the Murai coupling of 2′-methylacetophenone with trimethylvinylsilane, but 1 proved to be catalytically inactive under the same conditions.</p