What is the role of pi donor and pi acceptor ligands in coordination chemistry?

Pi donor and pi acceptor ligands play a crucial role in coordination chemistry by donating or accepting electron density through their pi orbitals. Pi donor ligands, such as phosphines and alkyls, donate electron density to the metal center, while pi acceptor ligands, such as carbon monoxide and cyanide, accept electron density from the metal center. This interaction helps stabilize the metal complex and influences its reactivity and properties.