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10.12: Formation Constants

Last updated

Feb 11, 2024
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- 10.11: Acid Dissociation Constants
- 10.13: Standard Reduction Potentials

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The following table provides $K_i$ and $\beta_i$ values for selected metal–ligand complexes, arranged by the ligand. 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 ^oC and zero ionic strength. Those values in brackets are considered less reliable.

Acetate $\ce{CH3COO-}$	log $K_1$	log $K_2$	log $K_3$
Mg²⁺	1.27
Ca²⁺	1.18
Ba²⁺	1.07
Mn²⁺	1.40
Fe²⁺	1.40
Co²⁺	1.46
Ni²⁺	1.43
Cu²⁺	2.22	1.41
Ag⁺	0.73	–0.09
Zn²⁺	1.57
Cd²⁺	1.93	1.22	–0.89
Pb²⁺	2.68	1.40

Ammonia $\ce{NH3}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$	log $K_5$	log $K_6$
Ag⁺	3.31	3.91
Co²⁺ (T = 20 °C)	1.99	1.51	0.93	0.64	0.06	–0.73
Ni²⁺	2.72	2.17	1.66	1.12	0.67	–0.03
Cu²⁺	4.04	3.43	2.80	1.48
Zn²⁺	2.21	2.29	2.36	2.03
Cd²⁺	2.55	2.01	1.34	0.84

Chloride $\ce{Cl-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$
Cu²⁺	0.40
Fe³⁺	1.48	0.65
Ag⁺ ( $\mu = 5.0 \text{ M}$ )	3.70	1.92	0.78	–0.3
Zn²⁺	0.43	0.18	–0.11	–0.3
Cd²⁺	1.98	1.62	–0.2	–0.7
Pb²⁺	1.59	0.21	–0.1	–0.3

Cyanide $\ce{CN-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$	log $K_6$
Fe²⁺					35.4 ( $\beta_6$ )
Fe³⁺					43.6 ( $\beta_6$ )
Ag⁺		20.48 ( $\beta_2$ )	0.92
Zn²⁺		11.07 ( $\beta_2$ )	4.98	3.57
Cd²⁺	6.01	5.11	4.53	2.27
Hg²⁺	17.00	15.75	3.56	2.66
Ni²⁺				30.22 ( $\beta_4$ )

Ethylenediamine $\ce{H2NCH2CH2NH2}$	log $K_1$	log $K_2$	log $K_3$
Ni²⁺	7.38	6.18	4.11
Cu²⁺	10.48	9.07
Ag⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	4.700	3.00
Zn²⁺	5.66	4.98	3.25
Cd²⁺	5.41	4.50	2.78

EDTA	log $K_1$	log $K_2$	log $K_3$	log $K_4$	log $K_5$	log $K_6$
Mg²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	8.79
Ca²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	10.69
Ba²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	7.86
Bi³⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	27.8
Co²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	16.31
Ni²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	18.62
Cu²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	18.80
Cr³⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	[23.4]
Fe³⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	25.1
Ag⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	7.32
Zn²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	16.50
Cd²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	16.46
Hg²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	21.7
Pb²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	18.04
Al³⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	16.3

Fluoride $\ce{F-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$	log $K_5$	log $K_6$
Al³⁺	6.11	5.01	3.88	3.0	1.4	0.4

Fluoride

$\ce{F-}$

log

$K_1$

log

$K_2$

log

$K_3$

log

$K_4$

log

$K_5$

log

$K_6$

Al³⁺

6.11

5.01

3.88

3.0

1.4

0.4

Hydroxide $\ce{OH-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$
Al³⁺	9.01	[9.69]	[8.3]	6.0
Co²⁺	4.3	4.1	1.3	0.5
Fe²⁺	4.5	]2.9]	2,6	–0.4
Fe³⁺	11.81	10.5	12.1
Ni²⁺	4.1	3.9	3.
Pb²⁺	6.3	4.6	3.0
Zn²⁺	5.0	[6.1]	2.5	[1.2]

Iodide $\ce{I-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$
Ag⁺	6.58	[5.12]	[1.4]
Cd²⁺ (T = 18 °C)	2.28	1.64	1.08	1.0
Pb²⁺	1.92	1.28	0.7	0.6

Iodide

$\ce{I-}$

log

$K_1$

log

$K_2$

log

$K_3$

log

$K_4$

log

$K_5$

log

$K_6$

Ag⁺

6.58

[5.12]

[1.4]

Cd²⁺ (T = 18 °C)

2.28

1.64

1.08

1.0

Pb²⁺

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 $K_6$
Mg²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	5.41
Ca²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	6.41
Ba²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	4.82
Mn²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	7.44
Fe²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	8.33
Co²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	10.38
Ni²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	11.53
Cu²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	12.96
Fe³⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	15.9
Zn²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	10.67
Cd²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	9.83
Pb²⁺ (T = 20 °C, $\mu = 0.1 \text{ M}$ )	11.39

Oxalate $\ce{C2O4^{2-}}$	log $K_1$	log $K_2$	log $K_3$
Ca²⁺ ( $\mu = 1 \text{ M}$ )	1.66	1.03
Fe²⁺ ( $\mu = 1 \text{ M}$ )	3.05	2.10
Co²⁺	4.72	2.28
Ni²⁺	5.16
Cu²⁺	6.23	4.04
Fe³⁺ ( $\mu = 0.5 \text{ M}$ )	7.53	6.11	4.83
Zn²⁺	4.87	2.78

1,10-phenanthroline	log $K_1$	log $K_2$	log $K_3$
Fe²⁺			20.7 ( $\beta_3$ )
Mn²⁺ ( $\mu = 0.1 \text{ M}$ )	4.0	3.3	3.0
Cu²⁺ ( $\mu = 0.1 \text{ M}$ )	7.08	6.64	6.08
Ni²⁺	8.6	8.1	7.6
Fe³⁺			13.8 ( $\beta_3$ )
Ag⁺ ( $\mu = 0.1 \text{ M}$ )	5.02	7.04
Zn²⁺	6.2	[5.9]	[5.2]

Thiosulfate $\ce{S2O3^{2-}}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$	log $K_5$	log $K_6$
Ag⁺ (T = 20 °C)	8.82	4.85	0.53

Thiosulfate

$\ce{S2O3^{2-}}$

log

$K_1$

log

$K_2$

log

$K_3$

log

$K_4$

log

$K_5$

log

$K_6$

Ag⁺ (T = 20 °C)

8.82

4.85

0.53

Thiocyanate $\ce{SCN-}$	log $K_1$	log $K_2$	log $K_3$	log $K_4$
Mn²⁺	1.23
Fe²⁺	1.31
Co²⁺	1.71
Ni²⁺	1.76
Cu²⁺	2.33
Fe³⁺	3.02
Ag⁺	4.8	3.43	1.27	0.2
Zn²⁺	1.33	0.58	0.09	–0.4
Cd²⁺	1.89	0.89	0.02	–0.5
Hg²⁺		17.26 ( $\beta_2$ )	2.71	1.83

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