Coordination Compounds

Vocabulary flashcards covering key definitions, types of structural and stereo-isomerism, and applications of coordination compounds from the lecture notes.

Central Ion (Centre of Coordination)

A central atom or ion in a coordination complex (either a cation or neutral metal atom) to which one or more neutral molecules or anions are attached.

Ligand

An ion or molecule that binds to a central metal atom.

Co-ordination Number (CN)

The number of atoms or ions immediately surrounding a central atom in a complex or crystal.

Co-ordination Sphere

The array of molecules and ions (the ligands) directly attached to the central metal atom.

Oxidation Number

A numerical value that represents the electric charge on the central metal atom of a complex ion.

Complex Ion (Complex Species)

An electrically charged or neutral species formed between a central metal ion and one or more surrounding ligands, molecules, or ions that contain at least one lone pair of electrons.

Structural Isomerism

Isomerism displayed by coordination compounds that have different ligands within their coordination spheres.

Ionization Isomerism

A type of structural isomerism that arises when the coordination compound gives different ions in solution.

Hydrate Isomerism

A type of structural isomerism that arises when different numbers of water molecules are present inside and outside the coordination sphere.

Coordination Isomerism

A form of structural isomerism in which the composition of the complex ion varies due to the interchange of ligands in both cationic and anionic ions.

Linkage Isomerism

A type of isomerism occurring in complex compounds that contain ambidentate ligands such as $\text{NO}_2^-$, $\text{S}_2\text{O}_3^{2-}$, $\text{SCN}^-$, $\text{CN}^-$, and $\text{CO}$.

Polymerisation Isomerism

A type of isomerism in complexes having the same empirical formula, but differing in molecular mass by integral multiples of the empirical mass.

Coordination Position Isomerism

A type of isomerism in which the total ratio of ligand to metal remains the same, but the ligands attached to a specific metal ion change.

Stereo-Isomerism

Isomerism where compounds contain the same ligands in their coordination spheres but differ in the way those ligands are arranged in space.

Geometrical Isomerism

A type of stereo-isomerism also known as cis-trans isomerism.

Optical Isomerism

A type of stereo-isomerism exhibited by coordination compounds with the same formula that differ in their abilities to rotate the plane of polarized light.

Enantiomers

A pair of optically active molecules that are non-superimposable mirror images of each other.

Dextro (d-form)

The optical isomer that rotates the plane of polarized light to the right direction.

Laevo (l-form)

The optical isomer that rotates the plane of polarized light to the left direction.

Mond's Process

A metallurgical process in which nickel is extracted by converting it into a volatile complex, nickel carbonyl ($\text{Ni(CO)}_4$), using carbon monoxide, which decomposes on heating into pure nickel and carbon monoxide.

Haemoglobin

The red blood pigment complex of iron (II) that acts as an oxygen carrier to different parts of the body in animals.

Vitamin B12

A biologically significant coordination complex of cobalt metal.

Chlorophyll

The green colouring matter of plants, which is a coordination complex of magnesium.