E4a: Stepwise Association Constants
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The following table provides K_{i} and β_{i} values for selected metal–ligand complexes, arranged by the ligand (red). All values are from Martell, A. E.; Smith, R. M. Critical Stability Constants, Vols. 1–4. Plenum Press: New York, 1976. Unless otherwise stated, values are for 25 ^{o}C and zero ionic strength. Those values in brackets are considered less reliable. For more details read here.
Acetate \(CH_3COO^{}\) 
log K_{1} 
log K_{2} 
log K3 
log K4 
log K5 
log K6 
Mg^{2}^{+} 
1.27 





Ca^{2}^{+} 
1.18 





Ba^{2}^{+} 
1.07 





Mn^{2}^{+} 
1.40 





Fe^{2}^{+} 
1.40 





Co^{2}^{+} 
1.46 





Ni^{2}^{+} 
1.43 





Cu^{2}^{+} 
2.22 
1.41 




Ag^{2}^{+} 
0.73 
–0.09 




Zn^{2}^{+} 
1.57 





Cd^{2}^{+} 
1.93 
1.22 
–0.89 



Pb^{2}^{+} 
2.68 
1.40 




Ammonia: NH_{3} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Ag^{+} 
3.31 
3.91 




Co^{2}^{+} (T = 20 ^{o}C) 
1.99 
1.51 
0.93 
0.64 
0.06 
–0.73 
Ni^{2}^{+} 
2.72 
2.17 
1.66 
1.12 
0.67 
–0.03 
Cu^{2}^{+} 
4.04 
3.43 
2.80 
1.48 


Zn^{2}^{+} 
2.21 
2.29 
2.36 
2.03 


Cd^{2}^{+} 
2.55 
2.01 
1.34 
0.84 


Chloride: Cl^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Cu^{2}^{+} 
0.40 





Fe^{3}^{+} 
1.48 
0.65 




Ag^{+} (μ = 5.0 M) 
3.70 
1.92 
0.78 
–0.3 


Zn^{2}^{+} 
0.43 
0.18 
–0.11 
–0.3 


Cd^{2}^{+} 
1.98 
1.62 
–0.2 
–0.7 


Pb^{2}^{+} 
1.59 
0.21 
–0.1 
–0.3 


Cyanide: CN^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Fe^{2}^{+} 





35.4 (β_{6}) 
Fe^{3}^{+} 





43.6 (β_{6}) 
Ag^{+} 

20.48 β_{2} 
0.92 



Zn^{2}^{+} 

11.07 β_{2} 
4.98 
3.57 


Cd^{2}^{+} 
6.01 
5.11 
4.53 
2.27 


Hg^{2}^{+} 
17.00 
15.75 
3.56 
2.66 


Ni^{2}^{+} 



30.22 (β_{4}) 


Ethylenediamine

log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Ni^{2}^{+} 
7.38 
6.18 
4.11 



Cu^{2}^{+} 
10.48 
9.07 




Ag^{+} (T = 20 ^{o}C, μ = 0.1 M) 
4.700 
3.00 




Zn^{2}^{+} 
5.66 
4.98 
3.25 



Cd^{2}^{+} 
5.41 
4.50 
2.78 



EDTA

log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Mg^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
8.79 





Ca^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
10.69 





Ba^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
7.86 





Bi^{3}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
27.8 





Co^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
16.31 





Ni^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
18.62 





Cu^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
18.80 





Cr^{3}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
[23.4] 





Fe^{3}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
25.1 





Ag^{+} (T = 20 ^{o}C, μ = 0.1 M) 
7.32 





Zn^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
16.50 





Cd^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
16.46 





Hg^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
21.7 





Pb^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
18.04 





Al^{3}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
16.3 





Fluoride: F^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Al^{3}^{+} (μ = 0.5 M) 
6.11 
5.01 
3.88 
3.0 
1.4 
0.4 
Hydroxide: OH^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Al^{3}^{+} 
9.01 
[9.69] 
[8.3] 
6.0 


Co^{2}^{+} 
4.3 
4.1 
1.3 
0.5 


Fe^{2}^{+} 
4.5 
[2.9] 
2.6 
–0.4 


Fe^{3}^{+} 
11.81 
10.5 
12.1 



Ni^{2}^{+} 
4.1 
3.9 
3.




Pb^{2}^{+} 
6.3 
4.6 
3.0 



Zn^{2}^{+} 
5.0 
[6.1] 
2.5 
[1.2] 


Iodide: I^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Ag^{+} (T = 18 ^{o}C) 
6.58 
[5.12] 
[1.4] 



Cd^{2}^{+} 
2.28 
1.64 
1.08 
1.0 


Pb^{2}^{+} 
1.92 
1.28 
0.7 
0.6 


Nitriloacetate

log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Mg^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
5.41 





Ca^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
6.41 





Ba^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
4.82 





Mn^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
7.44 





Fe^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
8.33 





Co^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
10.38 





Ni^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
11.53 





Cu^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
12.96 





Fe^{3}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
15.9 





Zn^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
10.67 





Cd^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
9.83 





Pb^{2}^{+} (T = 20 ^{o}C, μ = 0.1 M) 
11.39 





Oxalate: C_{2}O_{4}^{2–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Ca^{2}^{+} (μ = 1 M) 
1.66 
1.03 




Fe^{2}^{+} (μ = 1 M) 
3.05 
2.10 




Co^{2}^{+} 
4.72 
2.28 




Ni^{2}^{+} 
5.16 





Cu^{2}^{+} 
6.23 
4.04 




Fe^{3}^{+} (μ = 0.5 M) 
7.53 
6.11 
4.85 



Zn^{2}^{+} 
4.87 
2.78 




1,10Phenanthroline

log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Fe^{2}^{+} 


20.7 (β_{3}) 



Mn^{2}^{+} (μ = 0.1 M) 
4.0 
3.3 
3.0 



Co^{2}^{+} (μ = 0.1 M) 
7.08 
6.64 
6.08 



Ni^{2}^{+} 
8.6 
8.1 
7.6 



Fe^{3}^{+} 


13.8 (β_{3}) 



Ag^{+} (μ = 0.1 M) 
5.02 
7.04 




Zn^{2}^{+} 
6.2 
[5.9] 
[5.2] 



Thiosulfate: S_{2}O_{3}^{2–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Ag^{+} (T = 20 ^{o}C) 
8.82 
4.85 
0.53 



Thiocyanate: SCN^{–} 
log K_{1} 
log K_{2} 
log K_{3} 
log K_{4} 
log K_{5} 
log K_{6} 
Mn^{2}^{+} 
1.23 





Fe^{2}^{+} 
1.31 





Co^{2}^{+} 
1.72 





Ni^{2}^{+} 
1.76 





Cu^{2}^{+} 
2.33 





Fe^{3}^{+} 
3.02 





Ag^{+} 
4.8 
3.43 
1.27 
0.2 


Zn^{2}^{+} 
1.33 
0.58 
0.09 
–0.4 


Cd^{2}^{+} 
1.89 
0.89 
0.02 
–0.5 


Hg^{2}^{+} 

17.26 (β_{2}) 
2.71 
1.83 

