User:Praseodymium-141/Protactinocene

Protactinocene, Pa(C8H8)2, is an organoprotactinium compound composed of a protactinium atom sandwiched between two cyclooctatetraenide (COT2-) rings. As a solid it has a yellowish colour.

It was one of the first organoprotactinium compounds to be synthesised, and is a member of the actinocene family of actinide-based metallocenes. It was synthesized in 1974.

Structure
Protactinocene assumes a monoclinic crystal structure (P21/n space group) which is isomorphous to uranocene and thorocene.

Bonding
The protactinium-cyclooctatetraenyl bonding, like other actinide bonds, has been of interest for multiple theoretical studies. Computational chemistry methods indicate bonding with a large covalent character resulting mainly from the mixing of protactinium 6d orbitals with ligand π-orbitals, with a smaller interaction involving the protctinium 5f and ligand π-orbitals. The covalent component is characterised by donation of electron density to the protactinium.