As might be anticipated from consideration of atomic and ionic radii, the 4d- and 5d-eries elements often have higher coordination numbers than their smaller 3d-series con-eners. Table 19.4 illustrates this trend for the luorido and cyanido complexes of the arly d metals. Note that with the small F ligand, these 3d-series metals tend to form six-oordinate complexes but that the larger 4d- and 5d-series metals in the same oxidation tate tend to form seven-, eight-, and nine-coordinate complexes. The octacyanidomoly- date complex, [Mo(CN)8]3, illustrates the tendency towards high coordination numbers with compact ligands. The same complex is readily reduced electrochemically or chemi-ally without change of coordination number:
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