Ligands inorganic

Few inorganic ligands form stable complexes with the beryllium ion in aqueous solution. This is a reflection of the fact that on the one hand Be2+ shows a strong preference for oxygen donor ligands such as water and the hydroxide ion, and on the other hand reacts with the more basic ligands such as ammonia to give the insoluble hydroxide. Reported equilibrium constants are in Table V. 

The fluoride ion is the only inorganic ligand to form a complete substitution series, Be(H20)4 flFJ(2 1 (n = 1-4), though there is considerable variation in the equilibrium constants that have been reported. The most reliable values are probably those of Anttila et al. (117) who used both glass and fluoride-ion selective electrodes and also took account of the competing hydrolysis reactions. They did not, however, make measurements in the conditions where BeF2 would have been formed. A speciation diagram based on reported equilibrium constants is shown in Fig. 12. It can be seen that the fluoride ion competed effectively with hydroxide at pH values up to 8, when Be(OH)2 precipitates. 

Stability Constants for Beryllium Complexes with Inorganic Ligands 

Ligand Method TCC) Medium Log of equilibrium constants, remarks Ref. 

Both the metal-atom and matrix techniques have many applications 91) in the study of complexes having such classical, inorganic ligands as CO, N2, O2, or phosphines. From a metal-atom point of view, novel complexes have been synthesized that have not been readily accessible via normal, chemical-synthesis techniques. The entrapment of such species permits both a rationalization of their spectroscopic and chemical properties and an evaluation of their stability. 

Two separate publications 125, 126) described the synthesis of a number of carbonyl complexes of vanadium. The mononuclear species V(CO) , n = 1-6, have all been identified by using CO matrix-dilution experiments and mixed CO- CO isotope experiments while main- 

The magnetic circular dichroism (MCD) spectrum of matrix-isolated 

V(CO)g generated by cocondensing presynthesized V(CO)g with at 10 K has been observed (44, 45). As suggested in a metal-atom study (125), the results indicated that a static, Jahn-Teller distortion is present. Matrix MCD also proved useful in confirming the predicted paramagnetism of Fe(CO 4 (45) (produced by photolysis of FeCCOls). In addition, matrix MCD was used to detect such paramagnetic species as MnOaClj in the presence of MnOaCl (45). 

Nonmetal-atom, matrix-isolation spectroscopy has proved useful in structure and isomer determination of stable, metal carbonyls. Fe(CO)4(NO) was investigated (157) in low-temperature matrices with CO enrichment, and it was demonstrated that the IR spectrum is consistent with Cjv symmetry (trigonal bipyramid with an equatorial NO), in agreement with X-ray studies (55). The work resolves the dis- 

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TABLE 8.12 Cumulative Formation Constants for Metal Complexes with Inorganic Ligands... 

In Section 8, the material on solubility constants has been doubled to 550 entries. Sections on proton transfer reactions, including some at various temperatures, formation constants of metal complexes with organic and inorganic ligands, buffer solutions of all types, reference electrodes, indicators, and electrode potentials are retained with some revisions. The material on conductances has been revised and expanded, particularly in the table on limiting equivalent ionic conductances. 

L. G. SiLLfiN and A. E. Martell, Stability Constants of Metal-ion Complexes, The Chemical Society, London, Special Publications No. 17, 1964, 754 pp., and No. 25, 1971, 865 pp. Stability Constants of Metal-lon Complexes, Part A. Inorganic Ligands (E. Hcigfeldt, ed.), 1982, pp. 310, Part B. Organic Ligands (D. Perrin, ed.), 1979, pp. 1263. Pergamon Press, Oxford. A continually updated database is now provided by L. D. Pettit and K. J. Powell (eds.), IVPAC Stability Constants Database, lUPAC and Academic Software. 

Idem, Part 12 - Fuger, J. Khodakovskij, I.L. Medvedev, V.A. Navratil, J.D. "The Actinide Complex Ions with Inorganic Ligands", in preparation. 

Martell, A. E. Smith, R. M. "Critical Stability Constants, Volume 4—Inorganic Ligands" Plenum Press New York, 1977, p. 49. 

A number of other metal atom-matrix studies have appeared in the literature, with such typical inorganic ligands as NO and H. In the following Section, we shall briefly summarize some of these results. 

Although buffer components are often present at the highest concentration in a medium, metals can also bind to inorganic ligands in solution. Ligands such as CL, OHand SO can form soluble complexes with many metals.127 These complexes remain in solution, but are considered to be less bioavailable than the free, ionic species under most conditions.97 Even though other soluble metal species are considered less bioavailable, they may play roles in metal toxicity. 

Both organic and inorganic ligands such as Cl and dissolved organic carbon (fulvie acid and carboxylic acids) decrease metal adsorption. In the arid soils with higher pH, folic acids increase the solubility of metals such as Cu and Zn. The interaction between the transition of heavy metals and silicate surfaces was reviewed by McBride (1991). 

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