Co-Ordination Compounds

Name :- RISHI RAM MAHATOExam Roll No :- 14SCHE024547Class Roll No :- 146Session :- 2014-17

IntroductionCoordination refers to the "coordinate covalent bonds" (dipolar

bonds) between the ligands and the central atom. Hence, in this type of compounds a electron rich species donates its electron pair/pairs to the electron deficient species.

Coordination complexes have been known since the beginning of modern chemistry. Early well known coordination complexes include dyes such as Prussian blue.

In 1869, WILHELM BLOMSTRAND proposed the COMPLEX ION CHAIN THEORY.

Again it was improved by SOPHUS JORGENSEN.

*Alfred Warner was first to publish the most accepted theory of Complexes in 1893.

History

OccurrenceChlorophyll :- It’s a complex of Mg(II) directly

coordinated with Nitrogen with large Organic entity.Found in Leaves & Green parts of Plants.Plays vital role in existence of Living Things.

Hemoglobin :- It is Complex of Fe(II) directly linked to Nitrogen atoms of large organic entity (HEME structure).

This species is responsible for Red Coloration of Blood.It maintain the pH of the Blood as well.

Cytochrome :- Cytochromes are iron containing hemeproteins central to which are heme groups that are primarily responsible for the generation of ATP via electron transport.

They are found either as monomeric proteins (e.g., cytochrome c) or as subunits of larger enzymatic complexes that catalyze redox reactions.

Fluorite (also called fluorspar) :- is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. Fluorite is a colorful mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses.

Types According to their Geometry, These are classified as Linear for 2 coordination

Trigonal planar for 3 coordination

Tetrahedral or square planar for 4 coordination

Trigonal bipyramidal or square pyramidal for 5 coordination

Octahedral (orthogonal) for 6 coordination

Pentagonal Bipyramidal, capped octahedral or capped trigonal prismatic for 7 coordination

Square antiprismatic or dodecahedral for 8 coordination

Electrostatic model for bonding in transition metal complexes.Accounts for observed properties of transition metal

complexes.Focuses on d-orbitals.Ligands = point charges in case of anions or dipoles in case

of neutral molecules.Assumes metal ligand bond to be ionic.

Crystal Field Theory

Electrostatic Interactions(+) metal ion attracted to (-) ligands (anion or dipole provides stability

lone pair e-’s on ligands repulsed by e-’s in metal d orbitals interaction called crystal field influences d orbital energies

(not all d orbitals influenced the same way)

dx2-y2 dz2

dxy dxz dyz

X

Y Z

X

Y

X

Z

Y

Z

X

Greater Electrostatic Repulsion = Higher Potential Energy

Lobes Directed At Ligands

In Tetrahedral Complexes

dx2-y2 dz2

dxy dxz dyz

X

Y Z

X

Y

X

Z

Y

Z

X

less electrostatic repulsion = lower potential energy

Lobes directed between ligands

In Octahedral Complexes

Ligands Approach Along x, y, z Axes

(-) Ligands Attracted To (+) Metal Ion; Provides Stability

Octahedral Crystal Field

D Orbital E-’s Repulsed By (–) Ligands; Increases D Orbital

Potential Energy

+

-- -

--

-

PropertiesColors Of Transition Metal Complexes

1)A complex must have partially filled d subshell on metal to exhibit color.

2)A complex with 0 or 10 d e-s is colorless.3)Compounds/complexes that have color absorb specific wavelengths of visible light (400 –700 nm).4)Absorption of UV-visible radiation by atom, ion, or molecule:-

Occurs only if radiation has the energy needed to raise an e-

from its ground state to an excited state. i.e., from lower to higher energy orbital

5)wavelengths not absorbed are transmitted6)color observed = complementary color of color absorbed

Absorbed Color

Observed Color

Application

Cis-Platin :-(Cisplatin, Cisplatinum, Platamin, Neoplatin, Cismaplat or Cisdiamminedichloridoplatinum(ii) (CDDP) is a Chemotherapy Drug. It was the first member of a class of platinum containing anticancer drugs, which now also includes carboplatin and oxaliplatin. These platinum complexes react in the body, binding to DNA and causing the DNA strands to crosslink, which ultimately triggers cells to die in a programmed way.The compound is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.

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