coordination

Examples of coordination in the following topics:

• Reactions of Coordination Compounds

  • Many metal-containing compounds consist of coordination complexes.
  • The central atom or ion, together with all ligands, comprise the coordination sphere.
  • The central atoms or ion and the donor atoms comprise the first coordination sphere.
  • Coordination refers to the coordinate covalent bonds (dipolar bonds) between the ligands and the central atom.
  • As applied to coordination chemistry, this meaning has evolved.

• Coordination Number, Ligands, and Geometries

  • In coordination chemistry, the coordination number is the number of ligands attached to the central ion (more specifically, the number of donor atoms).
  • Coordination numbers are normally between two and nine.
  • In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex.
  • For example, trans-spanning ligands are bidentate ligands that can span coordination positions on opposite sides of a coordination complex.
  • Calculate the coordination number of the metal in a coordination complex.

• Biomolecules

  • Coordination complexes are found in many biomolecules, especially as essential ingredients for the active site of enzymes.
  • Coordination complexes (also called coordination compounds) and transition metals are widespread in nature.
  • Metalloenzymes contain a metal ion bound to the protein with one labile coordination site.
  • It consists of a zinc ion coordinated by three imidazole nitrogen atoms from three histidine units.
  • The fourth coordination site is occupied by a water molecule.

• Metal Cations that Act as Lewis Acids

  • Ligands create a complex when forming coordinate bonds with transition metals ions; the transition metal ion acts as a Lewis acid, and the ligand acts as a Lewis base.
  • The number of coordinate bonds is known as the complex's coordination number.
  • For instance, Mg2+ can coordinate with ammonia in solutions, as shown below:
  • The product is known as a complex ion, and the study of these ions is known as coordination chemistry.
  • Examples of several metals (V, Mn, Re, Fe, Ir) in coordination complexes with various ligands.

• Naming Coordination Compounds

  • Transition-metal and coordination compounds are named using a set of rules that describe oxidation numbers and anion and cation composition.
  • More complicated coordination compounds are composed of an atom or ion (usually a metal) and a surrounding array of bound molecules or anions, known as ligands.
  • Coordination refers to the coordinate covalent bonds (dipolar bonds) between the ligands and the central atom.
  • Write a proper chemical name for each of the following coordination compounds:
  • Identify the proper name for a coordination complex given its molecular formula.

• Coloring Agents

  • The electronic configuration of some metal complexes gives them important properties, such as color in coordination compounds.
  • Changing the metal or the ligand can change the color of the coordination complex.
  • Reactions starting from NiCl2·6H2O can be used to form a variety of nickel coordination complexes because the H2O ligands are rapidly displaced by ammonia, amines, thioethers, thiolates, and organophosphines.

• Applying the VSEPR Model

  • The oxygen atom will therefore be tetrahedrally coordinated, meaning that it sits at the center of a tetrahedron.
  • Two of the coordination positions are occupied by the shared electron-pairs that constitute the O–H bonds, and the other two by the non-bonding pairs.
  • Therefore, although the oxygen atom is tetrahedrally coordinated, the bonding geometry (shape) of the H2O molecule is described as bent.
  • An AX4E molecule (one in which the central atom is coordinated to four other atoms and to one nonbonding electron pair) has a "see-saw" shape; substituting more nonbonding pairs for bonded atoms reduces the triangular bipyramid coordination to even simpler molecular shapes.
  • There are well known examples of 6-coordinate central atoms with one, two, and three lone pairs.

• Lone Electron Pairs

  • Coordination number refers to the number of electron pairs that surround a given atom, often referred to as the central atom.
  • The oxygen atom will therefore be tetrahedrally coordinated, meaning that it sits at the center of the tetrahedron.
  • Therefore, although the oxygen atom is tetrahedrally coordinated, the bonding geometry (shape) of the H2O molecule is described as bent.
  • Substituting nonbonding pairs for bonded atoms reduces the triangular bipyramid coordination to even simpler molecular shapes.
  • Although the oxygen atom is tetrahedrally coordinated, the bonding geometry (shape) of the H2O molecule is described as bent.

• Crystal Structure: Packing Spheres

  • Each sphere that participates in a crystal structure has a coordination number, which corresponds to the number of spheres within the crystalline structure that touch the sphere that is being evaluated.
  • For a sphere in the interior of a crystal lattice, the number of spheres contacting the sphere that is being evaluated is known as the bulk coordination number.
  • For a sphere at the surface of a crystal, the number of spheres contacting the sphere being evaluated is known as the surface coordination number.
  • By considering how atomic spheres are arranged relative to one another, their coordination numbers, and the dimensions of the unit cell, it is possible to form a general view of the structure and complexity of particular crystal structures.

• Isomers in Coordination Compounds

  • Coordination stereoisomers have the same bonds in different orientations; structural isomers have different bonding orientations.
  • As with other compounds, there are several kinds of coordination complex isomers.
  • In coordination isomerism, both positive and negative ions of a salt are complex ions and the two isomers differ in the distribution of ligands between the cation and the anion.
  • Explain the effect of isomerization on the properties of a coordination complex.