Chemistry - A Molecular Science

Chapter 14 Inorganic Chemistry

configuration. The color of transition metals can

often be attributed to the metal absorbing

a visible photon as an electron is promoted from the lower set of d orbitals to the higher set.

Square planar and octahedral complexes can exist as either

cis

or

trans

isomers,

depending on whether two unique ligands are next to or opposite one another. In addition, octahedral complexes with three unique ligands can be either

mer

or

fac

isomers,

depending on whether the unique ligands are situated on the meridian or face of the octahedron.

Metals are critical to the proper function of living organisms. A magnesium ion

coordinated to a porphyrin derivative optim

izes the absorption of visible light in

photosynthesis, while manganese ions help the plant carry out the four-electron transfer reactions required for the production of car

bohydrates from carbon dioxide. Hemoglobin

uses an Fe

2+ ion at the center of a porphyrin that is bound to a protein to bind oxygen in

the lungs, where oxygen concentration is high.

It then releases it in tissue, where the

oxygen concentration is low.

Metals can also play key roles in drugs. Cisplatin,

cis

-[Pt(NH

) 32

Cl

], is an antitumor 2

drug that functions by binding to two sites of DNA. When bound to the platinum, the DNA double helix develops a kink. This change in secondary structure results in a modification of some of the DNA-protein inter

actions and prohibits the normal function of

the protein, causing the cell to die.

Transition metals can serve as either he

terogeneous or homogeneous catalysts. The

catalyst lowers the activation energy of a reaction by weakening the bonds of one of the reactants. The catalytic converter is a heterogene

ous catalyst that is used to rid automobile

exhaust of pollutants. Titanocene is a hom

ogeneous catalyst for the polymerization of

alkenes. It functions by coordinating th

e alkene and weakening the C=C double bond.

The crystalline structure of K

[Pt(CN) 2

]·3H 4

O shows that the Pt(CN) 2

2- 4

anions are

stacked face-to-face and form linear chains

in the solid. The interactions of the z

2 orbitals

on the platinum atoms result in an electronic band. The band is full and K

[Pt(CN) 2

]·3H 4

O 2

is an insulator. However, a partial oxida

tion transforms it into a metallic conductor.

Magnetic materials require unpaired elect

rons and a three-dimensional crystal

structure that aligns the spins of the electrons

. Cyanide ion has been used to bridge metals

with unpaired electrons to make magnets. The

first magnetic materials that are permanent

magnets above room temperature were prep

ared with cyanide-bridged vanadium and

chromium.

© by

North

Carolina

State

University