Formation constants of complex ions

Stepwise (log K) and cumulative (log β) formation constants of metal ions with ammonia, halides, thiosulfate, thiocyanate and hydroxide. The copper–ammine distribution, silver chloride dissolving in ammonia and the amphoteric hydroxides are all computed from this table.


$\ce{Cu^2+}$	$\ce{NH3}$	$\ce{[Cu(NH3)]^2+}$	1	4.04	4.04	25 °C, I = 0
$\ce{Cu^2+}$	$\ce{NH3}$	$\ce{[Cu(NH3)2]^2+}$	2	3.43	7.47	25 °C, I = 0
$\ce{Cu^2+}$	$\ce{NH3}$	$\ce{[Cu(NH3)3]^2+}$	3	2.80	10.27	25 °C, I = 0
$\ce{Cu^2+}$	$\ce{NH3}$	$\ce{[Cu(NH3)4]^2+}$	4	1.48	11.75	25 °C, I = 0
$\ce{Zn^2+}$	$\ce{NH3}$	$\ce{[Zn(NH3)]^2+}$	1	2.21	2.21	25 °C, I = 0
$\ce{Zn^2+}$	$\ce{NH3}$	$\ce{[Zn(NH3)2]^2+}$	2	2.29	4.50	25 °C, I = 0
$\ce{Zn^2+}$	$\ce{NH3}$	$\ce{[Zn(NH3)3]^2+}$	3	2.36	6.86	25 °C, I = 0
$\ce{Zn^2+}$	$\ce{NH3}$	$\ce{[Zn(NH3)4]^2+}$	4	2.03	8.89	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)]^2+}$	1	2.72	2.72	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)2]^2+}$	2	2.17	4.89	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)3]^2+}$	3	1.66	6.55	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)4]^2+}$	4	1.12	7.67	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)5]^2+}$	5	0.67	8.34	25 °C, I = 0
$\ce{Ni^2+}$	$\ce{NH3}$	$\ce{[Ni(NH3)6]^2+}$	6	−0.03	8.31	25 °C, I = 0
$\ce{Cd^2+}$	$\ce{NH3}$	$\ce{[Cd(NH3)]^2+}$	1	2.55	2.55	25 °C, I = 0
$\ce{Cd^2+}$	$\ce{NH3}$	$\ce{[Cd(NH3)2]^2+}$	2	2.01	4.56	25 °C, I = 0
$\ce{Cd^2+}$	$\ce{NH3}$	$\ce{[Cd(NH3)3]^2+}$	3	1.34	5.90	25 °C, I = 0
$\ce{Cd^2+}$	$\ce{NH3}$	$\ce{[Cd(NH3)4]^2+}$	4	0.84	6.74	25 °C, I = 0
$\ce{Ag+}$	$\ce{NH3}$	$\ce{[Ag(NH3)]+}$	1	3.31	3.31	25 °C, I = 0
$\ce{Ag+}$	$\ce{NH3}$	$\ce{[Ag(NH3)2]+}$	2	3.91	7.22	25 °C, I = 0
$\ce{Ag+}$	$\ce{S2O3^2-}$	$\ce{[Ag(S2O3)]-}$	1	8.82	8.82	20 °C, I = 0
$\ce{Ag+}$	$\ce{S2O3^2-}$	$\ce{[Ag(S2O3)2]^3-}$	2	4.85	13.67	20 °C, I = 0
$\ce{Ag+}$	$\ce{Cl-}$	$\ce{AgCl(aq)}$	1	3.70	3.70	25 °C, I = 5 M
$\ce{Ag+}$	$\ce{Cl-}$	$\ce{[AgCl2]-}$	2	1.92	5.62	25 °C, I = 5 M
$\ce{Ag+}$	$\ce{Cl-}$	$\ce{[AgCl3]^2-}$	3	0.78	6.40	25 °C, I = 5 M
$\ce{Ag+}$	$\ce{Cl-}$	$\ce{[AgCl4]^3-}$	4	−0.30	6.10	25 °C, I = 5 M
$\ce{Pb^2+}$	$\ce{Cl-}$	$\ce{[PbCl]+}$	1	1.59	1.59	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{Cl-}$	$\ce{PbCl2(aq)}$	2	0.21	1.80	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{Cl-}$	$\ce{[PbCl3]-}$	3	−0.10	1.70	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{Cl-}$	$\ce{[PbCl4]^2-}$	4	−0.30	1.40	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{I-}$	$\ce{[PbI]+}$	1	1.92	1.92	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{I-}$	$\ce{PbI2(aq)}$	2	1.28	3.20	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{I-}$	$\ce{[PbI3]-}$	3	0.70	3.90	25 °C, I = 0
$\ce{Pb^2+}$	$\ce{I-}$	$\ce{[PbI4]^2-}$	4	0.60	4.50	25 °C, I = 0
$\ce{Fe^3+}$	$\ce{SCN-}$	$\ce{[Fe(SCN)]^2+}$	1	3.02	3.02	25 °C, I = 0
$\ce{Al^3+}$	$\ce{OH-}$	$\ce{Al(OH)^2+}$	1	—	9.01	25 °C, I = 0 (cumulative)
$\ce{Al^3+}$	$\ce{OH-}$	$\ce{Al(OH)4-}$	4	—	33.00	25 °C, I = 0 (cumulative)
$\ce{Zn^2+}$	$\ce{OH-}$	$\ce{Zn(OH)+}$	1	—	5.00	25 °C, I = 0 (cumulative)
$\ce{Zn^2+}$	$\ce{OH-}$	$\ce{Zn(OH)3-}$	3	—	13.60	25 °C, I = 0 (cumulative)
$\ce{Zn^2+}$	$\ce{OH-}$	$\ce{Zn(OH)4^2-}$	4	—	14.80	25 °C, I = 0 (cumulative)
$\ce{Fe^3+}$	$\ce{OH-}$	$\ce{Fe(OH)^2+}$	1	—	11.81	25 °C, I = 0 (cumulative)
$\ce{Fe^3+}$	$\ce{OH-}$	$\ce{Fe(OH)2+}$	2	—	22.31	25 °C, I = 0 (cumulative)

Values are for 25 °C and zero ionic strength unless noted: Ag⁺–Cl⁻ is for 5 M ionic strength and Ag⁺–S₂O₃²⁻ for 20 °C. For hydroxo complexes only the measured cumulative constants are listed; the estimated neutral species (e.g. Al(OH)₃(aq), Zn(OH)₂(aq)) are left out.

Sources

A. E. Martell & R. M. Smith, Critical Stability Constants (Plenum, 1974–1989), as tabulated in D. Harvey, Analytical Chemistry 2.1, Appendix 12.

Sources

Used in these lessons