Who were the Titans that were involved in Titanomachy?

According to ancient sources, Coeus, Cronus, Crius, Hyperion, Iapetus, Atlas, Astraeus, Pallas and Perses were involved.

It is said that Atlas was their leader and through his leadership they were going to win the war, had Cronus not made too many enemies because of his greed and fear of losing his throne.

The Titans, elder Greek gods and first divine rulers

The mighty Titans were a powerful race that ruled the world before Olympians, in a time of the Golden Age of men. They were immortal giants of incredible strength and knowledge of old religion rituals and magic. They are also known as the Elder Gods and their dwelling place was at Mount Othrys. In Greek culture they were interpreted as personifications of the earth (Gaea) and the sky or heavens (Uranus).

The first generation of Titans were descendants of Gaea and Uranus who originally gave birth to Twelve Titans, six males and six females. Males were Coeus, Cronus, Crius, Hyperion, Iapetus and Oceanus and females were Mnemosyne, Phoebe, Rhea, Theia, Themis and Tethys. They arose to power when Cronus, in a plot with his mother and his brothers, castrated his father Uranus and took the rulership of Cosmos from him. More details about this conflict can be found in the Genesis.

During this reign, the titans and other primeval gods decided to pass on the godly genes and gave birth to the second generation of Titans. Hyperion and Theia gave birth to Eos, Helios and Selene, while Coeus and Phoebe brought forth Leto and Asteria. Oceanus and Tethys gave birth to Oceanids and Potamoi who are in general not referred as Titans. However, an Oceanid Clymene, a daughter of Oceanus and Tethys, helped Iapetus to continue the next generation and bore him Atlas, Prometheus, Epimetheus and Menoetius. Crius and his half-sister Eurybia, a daughter of Gaea and Pontus, brought forth Astraeus, Pallas and Perses and, eventually, Cronus and Rhea gave birth to younger gods, Zeus, Hades, Poseidon, Hera, Hestia and Demeter who rebelled against Cronus and his followers and later defeated them in a ten-year war, known as Titanomachy. They called themselves the Olympian Gods, after Mount Olympus which was their main dwelling place, and became the new rulers of Cosmos.

First Generation
Coeus

Titan of intelligence and farsight

Crius

Titan of heavenly constellations

Cronus

Titan of time and the ages

Hyperion

Titan of light

Iapetus

Titan of mortal life span

Mnemosyne

Titaness of memory and remembrance

Oceanus

Titan of all the salt water on earth

Phoebe

Titaness of prophetic radiance

Rhea

Titaness of fertillity and motherhood

Tethys

Titaness of all the fresh water on earth

Theia

Titaness of shining

Themis

Titaness of divine law and order

Second Generation
Atlas

Titan of endurance

Eos

Titaness of the dawn

Epimetheus

Titan of afterthought

Helios

Titan of the sun

Leto

Titaness of modesty and motherhood

Prometheus

Titan of forethought