Coordination number 2
المؤلف:
CATHERINE E. HOUSECROFT AND ALAN G. SHARPE
المصدر:
INORGANIC CHEMISTRY
الجزء والصفحة:
2th ed p 542
23-2-2017
1135
Coordination number 2
Examples of coordination number 2 are uncommon, being generally restricted to Cu(I), Ag(I), Au(I) and Hg(II), all d10 ions. Examples include [CuCl2]-, [Ag(NH3)2]+, [Au(CN)2]-, ) R3P(AuCl, [Au(PR3)2] (R = alkyl or aryl, Figure 1.1a) and Hg(CN)2, in each of which the metal center is in a linear environment. However, in the solid state, the Cu(I) centre in K[Cu(CN)2] is 3-coordinate by virtue of cyano-bridge formation (see Structure 21.67). Bulky amido ligands, e.g. [N(SiR3)2]-, are often associated with low coordination numbers. For example, in [Fe{N(SiMePh2)2}2] (∠N– Fe–N=1690), the sterically demanding amido groups force a 2-coordinate environment on a metal centre that usually prefers to be surrounded by a greater number of ligands.
Fig. 1.1 Examples of 2- and 3-coordinate structures (X-ray diffraction data): (a) [Au{P(cyclo-C6H11)3}2]+ in the chloride salt [J.A. Muir et al. (1985) Acta Crystallogr., Sect. C, vol. 41, p. 1174], (b) [AgTe7]3- in the salt [Et4N][Ph4P]2[AgTe7] [J.M. McConnachie et al. (1993) Inorg. Chem., vol. 32, p. 3201], and (c) [Fe{N(SiMe3(2}3] [M.B. Hursthouse et al. (1972) J. Chem. Soc., Dalton Trans., p. 2100]. Hydrogen atoms are omitted for clarity; colour code: Au, red; Ag, yellow; Fe, green; C, grey; P, orange; Te, dark blue; Si, pink; N, light blue.
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