Pb complexes

Pb complexes in the coastal diatom, Thalassiosira weissflogii, Environ. Sci. Tech-nol, 28, 1781-1790. 

Buffle, J., Mota, A. M. and Simoes Gonsalves, M. L. S. (1987). Adsorption of fulvic-like organic ligands and their Cd and Pb complexes at a mercury electrode, J. Electroanal. Chem., 223, 235-262. 

Recent data on several Pb + complexes can be found in Refs 59, 64. 

Unlike Si and Ge acetylacetonates (acac), in which the central M atom is hexacoordinated, the coordination number of the Sn atom in RSn(acac)3 is 7173. Hexacoordinated Si, Ge, Sn, Pb complexes with tropolone (Tp) are known. Tp4M molecules, where the metal atom is octacoordinated for M = Sn, Pb or hexacoordinated for M = Si, Ge, are of particular interest. The latter compounds correspond to the structure Tp3M+Tp- and exist as salts or ion pairs174. 

Addition of PbR2 to a benzene solution of iron complexes [CpFe(CO)2X] (X = I, Br or Cl) resulted in the formation of four-coordinated functionalized Fe—Pb complexes, [CpFe(CO)2 (PbR2X)]512. 

There are a limited number of structures reported for Fe—Pb complexes and these are recorded in Tables 16-18. For a series of iron carbonyl lead clusters, the Fe—Pb bond lengths vary from 2.624 A for an electron-deficient three-coordinate planar Pb cluster [FefCO jjPbl to 2.828 A for a tetrahedral bridging anionic Pb cluster... 

Phinney, J.T., and Bruland, K.W. (1994) Uptake of lipophilic organic Cu, Cd, and Pb complexes in the coastal diatom Thalassiosira weissflogii. Environ. Sci. Technol. 28, 1781-1790. 

Treatment of 17 with a Cd-Pb complex[l 1] in aqueous THF furnished the quinolizidine 18 in 92% yield as the only cyclized product. Stereochemistry of this quinolizidine was assigned by the NOE between Ha and Hb, in addition to the coupling constant of Hc. Finally, this assignment was confirmed by X-ray diffraction analysis. 

The speciation and stabihty constants of the Cu(n), Ni(II), Zn(II) and VO(II) complexes of mimosine (9) were determined . The Cu(II) and VO(II) complexes adopt a coordination chemistry analogous to the those of maltol (discussed below). The Zn(II) complex of the deprotonated mimosine analogue 48 has a 1 2 distorted square-pyramidal structure with trans configuration and a water molecule at the apex (49) . Pb(II) forms a 1 2 complex with 48, which further interacts with one enolate of an adjacent Pb(II) center via Pb-0 bridges (2.64 A) to yield a dinuclear Pb complex (50). Vanadate (with a -1-5 oxidation state on V) forms with 48 the 1 1 [V02(48 )(0H)(H20)] and 1 2 [V02(48 )2] complex anions, as shown by potentiometry, cyclic voltammetry and NMR and EPR spectroscopies, with V NMR peaks at —502 and —476 ppm, respectively, similar to the maltol complexes (peaks at —509 and —496 ppm) discussed in the next section. 

The synthesis of lead(II) porphyrin complexes has been efficiently performed in a solid-state reaction. Grinding together equimolar amounts of (por)H2 (porH2 = meso-(4-HO-C6H4)4-porphyrin, meso-(4-MeOC6H4)4-porphyrin, or meso-(4-N02-C6H4)4-porphyrin) with lead(II) acetate in a pestle and mortar with a trace of acetone leads to the (por)Pb complexes in excellent yield after chromatographic purification. ... 

These criticisms and possible action to eliminate or minimize them were discussed when the methodology was applied to study the complexation of Cd, Cu, Ph and Zn (32-34, 53, 104, 108). The results showed that Cu and Pb complexes were kinetically inert, with A ,/ values of between 10 and 10 s, which means that the lifetime of metal complexes, expressed by /ka, is some orders of magnitude higher than the residence time (1-100 ms) of complexes in the diffusion layer when Rotating Disk Electrodes (RDEs) are used. It can therefore be concluded that the reduction process is not appreciably affected by dissociation reaction inside the diffusion layer. Experiments showed instead that Cd complexes present a kinetic lability when Hanging Mercury Drop Electrode (HMDE) or RDE methods are used at low rotation speed (53). The results emphasized that dissociation from the electrode interface determines an underestimation of the conditional stability constant when low rotation speeds are used. To minimize the risk with respect to this problem the RDE method is normally used at the highest rotation speed. 

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