The accepted carbene catalytic cycle was proposed by Yates in 1952.

Transmetalation is often used as a step in the catalytic cycles of cross-coupling reactions.

A catalytic cycle is not necessarily a full reaction mechanism.

The catalytic cycle can also be described as follows:

This suggests that ruthenium acetylides are not involved in the catalytic cycle.

There are many deviations from this traditional catalytic cycle.

The catalytic cycle (Figure 1) illustrates well how a modern inorganic chemist thinks.

These high field ligands may ensure the iron centers at the active site remain in a low spin state throughout the catalytic cycle.

This step occurs in-situ, or at the same time as the catalytic cycle in the reaction.

In some cases they serve as placeholder ligands, being removed during a catalytic cycle.