Complexes optiquement actifs de la serie du titanocene. Premiere filiation absolue entre les derives carbones et les complexes du titane a chiralite centro-metallee

Optically active titanocene complexes are synthesised starting from a fulvene asymmetric reduction. The optical purity is determined by analogy of these compounds with ferrocene derivatives.An absolute configuration is proposed for some titanium chiral complexes by reference to chiral ferrocene compounds.     

Chiral biscyclopentadienylniobium(III) complexes

Summary Bimetallic chiral complexes [(⁵-C₅H₄CHMePh)(⁵-C₅H₅) Nb(CO)ML _n ] with ML _n =Co(CO)₄ and HFe(CO)₄ have been prepared and characterized. The lability of the metal-metal bond explains the lack of stereostability of these complexes. The two diastereoisomeric forms of polymetallic chiral complexes [(⁵- C₅H₅CHMePh)(⁵-C₅H₅)Nb(CO)[HFe₃(CO)₁₁] have been synthetized, separated and their stereostability has been investigated. All the complexes were characterized by elemental analysis i.r. and¹H n.m.r. spectroscopy.     

Insertion of activated acetylenes into the metal-hydride bond of [(η5-C5H5)2M(CO)H] (M = Nb,Ta)

Reactions of [Cp₂M(CO)H] (M = Nb, Ta; Cp = η⁵-C₅H₅) with various acetylenes RCCR having electron-withdrawing groups were investigated. They give the σ-al- kenyl complexes [Cp₂M(CO)(CRCHR)] via insertion of the alkyne into the MH bond. On the basis of ¹H and ¹⁹F NMR data the reactions were shown to be: (i) regioselective, monosubstituted alkynes giving only the α-R metallated complex; (ii) stereoselective, exclusive formation of the Z-isomer being observed with hexafluorobut-2-yne. The Z isomer has been shown to exist as two conformers, the steric requirements of the ligands creating a barrier to rotation of the alkenyl group around the MC σ bond.     

Instability of mercury in specimens of human urine for external quality assessment

An under-recovery of inorganic mercury added to urine and a wide range of results is observed in quality assessment schemes (EQAS) for trace elements. Furthermore, the under-recoveries are inconsistent suggesting features associated with the urine matrix may make the mercury unavailable for measurement. To investigate the instability of mercury in urine the following experiments were set up: (1) a sample of Hg²⁺ in water with various ‘stabilizers’ added was sent to UK external quality assessment scheme participants. (2) Urine was collected from volunteers who also completed a 3-day food diary. Hg, Ca, Mg, Se, uric acid, phosphate, creatinine, reducing substances and protein were measured. Inorganic mercury was spiked into the urine, stabilizers were added and the mercury determined following storage. The results confirmed under-recovery of mercury in association with the urine matrix. Further investigations of how urinary components affect the measurement of mercury are necessary.     

A dansylated peptide for the selective detection of copper ions

A new peptidyl fluorescent chemosensor for the selective detection of copper ions was studied.