Thallium block complexes

As a consequence, it is not surprising that there appears to be only one isolated structure claimed. This is of the indium(I) and thallium(I) complexes with a single M—C bond from a o--bonded benzene anion that carries two bulky tri-substituted benzene substituents in ortho positions these partially block approach of other potential donors to the metal cation (Figure 4.3). An X-ray crystal structure has been determined, defining the shape. It is a rare observation, as other complexes (such as Mn(I) and Fe(I)) of the same ligand bind another ligand at the open side of the molecule, as expected. In any case, this coordination number is trivial in the sense that it can have only one shape - a linear M—L arrangement. 

Table 6.8 gives stability constants for the complexes [FeX] and [HgX] for different halide ions while the stabilities of the Fe complexes decrease in the order F > CP > Br, those of the Hg complexes increase in the order F < CP < Br < P. More generally, in examinations of stability constants by Ahrland, Chatt and Davies, and by Schwarzenbach, the same sequence as for Fe + was observed for the lighter s- and /i-block cations, other early J-block metal cations, and lanthanoid and actinoid metal cations. These cations were collectively termed class (a) cations. The same sequence as for Hg complexes was observed for halide complexes of the later J-block metal ions, tellurium, polonium and thallium. These ions were collectively called class (b) cations. Similar patterns were found for other donor atoms ligands with O- and iV-donors form more stable complexes with class (a) cations, while those with S- and F-donors form more stable complexes with class (b) cations. 

The vast range in elemental properties, from those of metallic elanents such as thallium and lead that have very low electronegativities of 1.8 and 1.9 (respectively) to those of the nonmetalUc elements such as oxygen and fluorine that have the highest electronegativities of 3.5 and 4.0 (respectively), results in the great chemical diversity of the elements in the p block. These elements include metals, alloys, simple covalent compounds, enormous covalent network compounds, simple binary ionic compounds, and complex chain and layered ionic compounds. 

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