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In coordination chemistry, a ligand [a] is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs , often through Lewis bases . [ 1 ]
In the covalent bond classification method, κ 1-carbonate is anX ligand and κ 2-carbonate is an X 2 ligand. With two metals, the number of bonding modes increases because carbonate often serves as a bridging ligand. It can span metal-metal bonds as in [Ru 2 (CO 3) 4 Cl 2] 5-, where again it functions as an (X) 2 ligand.
As a monodentate ligand, azide binds through one of the two terminal nitrogen atoms, i.e. M-N=N=N. Azide is a "pure" sigma donor. It is classified as an X ligand in the Covalent bond classification method. In the usual electron counting method, it is a one-electron ligand. The N 3 unit is linear or nearly so. The M-N-N angles are quite bent.
Chromium(II) ion in aqueous solution. Most aquo complexes are mono-nuclear, with the general formula [M(H 2 O) 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 ...
Most commonly, a solution containing the metal ion and the ligand in a medium of high ionic strength is first acidified to the point where the ligand is fully protonated. This solution is then titrated , often by means of a computer-controlled auto-titrator, with a solution of CO 2 -free base.
When given a metal complex and the trends for the ligand types, the complex can be written in a more simplified manner with the form [ML l X x Z z] Q±. The subscripts represent the numbers of each ligand type present in that complex, M is the metal center, and Q is the overall charge on the complex. Some examples of this overall notation are ...
The scheme below shows the dissociation pathway of a CO ligand in the cis and trans position to the X, followed by the association of ligand Y. This is an example of a dissociative mechanism, where an 18 e − complex loses a CO ligand, making a 16 e − intermediate , and a final complex of 18 e − results from an incoming ligand inserting in ...
In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules ...