Mo-Pb bonds

The complex is air sensitive but thermally stable. The Mo-Pb bond of 2.55 A is very short and the almost linear geometry, Mo-Pb-C bond angle 177.8(2)°, clearly indicates the formation of a Mo=Pb triple bond. 

Hydrogen chloride attacks the Mn—Pb bonds to form lead chloride486. To compare the reactivity of the M—H bond with the M—Pb bond in the [(Cp2MH)2(Ai-Pb(02CMe)2] (M=Mo, W), the complexes were reacted with cyanoalkyne, HC=C—CN however, the only isolated product was Cp2M C(CN)=CH2 2515. 

Only salts of the dithio anions with large cations can be prepared177,178). Addition of Co+2,Pb+2, and Ce+3 to solutions of ammonium dithiomolybdate yielded solids that showed the absence of Mo-S bonding at 480—450 cm-1 178). Dithio salts so far prepared177) are given in Table 6. The salt Cs2W02Se2 has been also isolated as a stable solid by the addition of cesium chloride to a water solution of(NH4)2W02S2177). 

Complexes with Mo-Pb and W-Pb bonds have also been studied with esoec Mo NMR and co dUb co slant /( Pb w) in the case of... 

They indicated that the softness parameter may reasonably be considered as a quantitative measure of the softness of metal ions and is consistent with the HSAB principle by Pearson (1963, 1968). Wood et al. (1987) have shown experimentally that the relative solubilities of the metals in H20-NaCl-C02 solutions from 200°C to 350°C are consistent with the HSAB principle in chloride-poor solutions, the soft ions Au" " and Ag+ prefer to combine with the soft bisulfide ligand the borderline ions Fe +, Zn +, Pb +, Sb + and Bi- + prefer water, hydroxyl, carbonate or bicarbonate ligands, and the extremely hard Mo + bonds only to the hard anions OH and. Tables 1.23 and 1.24 show the classification of metals and ligands according to the HSAB principle of Ahrland et al. (1958), Pearson (1963, 1968) (Table 1.23) and softness parameter of Yamada and Tanaka (1975) (Table 1.24). Compari.son of Table 1.22 with Tables 1.23 and 1.24 makes it evident that the metals associated with the gold-silver deposits have a relatively soft character, whereas those associated with the base-metal deposits have a relatively hard (or borderline) character. For example, metals that tend to form hard acids (Mn +, Ga +, In- +, Fe +, Sn " ", MoO +, WO " ", CO2) and borderline acids (Fe +, Zn +, Pb +, Sb +) are enriched in the base-metal deposits, whereas metals that tend to form soft acids... 

Pimentel employed this three-center, four-electron (3c/4e) MO model to discuss the bonding in triiodide (I3-), bifluoride (FHF-), and other prototypical hypervalent species. In triiodide and other trihalides, for example, the relevant AOs are the (pa, Pb, Pc) orbitals along the bonding axis,... 

Figure 4.31. Crystal structure of the Chevrel phase Mo6PbS8. Portions of four rhombohedral unit cells with one common Pb atom (black) are shown. The bonding between different clusters is suggested by the Mo—S inter-cluster links.

The Pb9Mo(CO)3" also shows three ° Pb NMR resonances in a 4 4 1 ratio with the four-bonded Pbl being the most downfield at 27 ppm. The Mo NMR spectrum... 

In constructing a localized MO for the bond A—B it is necessary to specify an orbital centred on A (tpA) and an orbital centred on B (y ). In principle, provided symmetry about the bond axis is preserved (we are still considering only cr-bonded systems), our choice of tpA and pB is not restricted and we could use any well-defined mathematical function or combination of functions. Common sense, however, dictates that the most sensible functions to use for this purpose are the AOs of the free atoms A and B. There are three reasons why this is a sensible choice one mathematical, one chemical, and one practical. 

Fig. 16.67 Siructure of one of the Chevrel compounds. PbMo Ss. ( ) Mo (O) S (O) Pb [From Cotton. F. A. In Reactivity of Metal-Metal Bonds-, Chisholm, M. H., Ed. ACS Symposium Series 155 American Chemical Society Washington, DC 1981. Reproduced with permission.]...

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