Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Metal aquo complex
In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorates. They have the general stoichiometry [M(H2O)n]z+. Their behavior underpins many aspects of environmental, biological, and industrial chemistry. This article focuses on complexes where water is the only ligand ("homoleptic aquo complexes"), but of course many complexes are known to consist of a mix of aquo and other ligands.
Most aquo complexes are mono-nuclear, with the general formula [M(H2O)6]n+, with n = 2 or 3; they have an octahedral structure. The water molecules function as Lewis bases, donating a pair of electrons to the metal ion and forming a dative covalent bond with it. Typical examples are listed in the following table.
Tutton's salts are crystalline compounds with the generic formula (NH4)2M(SO4)2·(H2O)6 (where M = V2+, Cr2+, Mn2+, Co2+, Ni2+, or Cu2+). Alums, MM′(SO4)2(H2O)12, are also double salts. Both sets of salts contain hexa-aquo metal cations.
Silver(I) forms [Ag(H2O)4]+, a rare example of a tetrahedral aquo complex. Palladium(II) and platinum(II) were once thought to form square planar aquo complexes.
Aquo complexes of lanthanide(III) ions are eight- and nine-coordinate, reflecting the large size of the metal centres.
In the binuclear ion [Co2(OH2)10]4+ each bridging water molecule donates one pair of electrons to one cobalt ion and another pair to the other cobalt ion. The Co-O (bridging) bond lengths are 213 picometers, and the Co-O (terminal) bond lengths are 10 pm shorter.
The complexes [Mo2(H2O)8]4+ and [Rh2(H2O)10]4+ contain metal-metal bonds.
Monomeric aquo complexes of Nb, Ta, Mo, W, Mn, Tc, Re, and Os in oxidation states +4 to +7 have not been reported. For example, [Ti(H2O)6]4+ is unknown: the hydrolyzed species [Ti(OH)2(H2O)n]2+ is the principal species in dilute solutions. With the higher oxidation states the effective electrical charge on the cation is further reduced by the formation of oxo-complexes.
Hub AI
Metal aquo complex AI simulator
(@Metal aquo complex_simulator)
Metal aquo complex
In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorates. They have the general stoichiometry [M(H2O)n]z+. Their behavior underpins many aspects of environmental, biological, and industrial chemistry. This article focuses on complexes where water is the only ligand ("homoleptic aquo complexes"), but of course many complexes are known to consist of a mix of aquo and other ligands.
Most aquo complexes are mono-nuclear, with the general formula [M(H2O)6]n+, with n = 2 or 3; they have an octahedral structure. The water molecules function as Lewis bases, donating a pair of electrons to the metal ion and forming a dative covalent bond with it. Typical examples are listed in the following table.
Tutton's salts are crystalline compounds with the generic formula (NH4)2M(SO4)2·(H2O)6 (where M = V2+, Cr2+, Mn2+, Co2+, Ni2+, or Cu2+). Alums, MM′(SO4)2(H2O)12, are also double salts. Both sets of salts contain hexa-aquo metal cations.
Silver(I) forms [Ag(H2O)4]+, a rare example of a tetrahedral aquo complex. Palladium(II) and platinum(II) were once thought to form square planar aquo complexes.
Aquo complexes of lanthanide(III) ions are eight- and nine-coordinate, reflecting the large size of the metal centres.
In the binuclear ion [Co2(OH2)10]4+ each bridging water molecule donates one pair of electrons to one cobalt ion and another pair to the other cobalt ion. The Co-O (bridging) bond lengths are 213 picometers, and the Co-O (terminal) bond lengths are 10 pm shorter.
The complexes [Mo2(H2O)8]4+ and [Rh2(H2O)10]4+ contain metal-metal bonds.
Monomeric aquo complexes of Nb, Ta, Mo, W, Mn, Tc, Re, and Os in oxidation states +4 to +7 have not been reported. For example, [Ti(H2O)6]4+ is unknown: the hydrolyzed species [Ti(OH)2(H2O)n]2+ is the principal species in dilute solutions. With the higher oxidation states the effective electrical charge on the cation is further reduced by the formation of oxo-complexes.