title: Synthesis, structure and bonding of actinide disulphide dications in the gas phase.
abstract: Actinide disulphide dications, AnS22+, were produced in the gas phase for An = Th and Np by reaction of An2+cations with the sulfur-atom donor COS, in a sequential abstraction process of two sulfur atoms, as examined by FTICR mass spectrometry. For An = Pu and Am, An2+ions were unreactive with COS and did not yield any sulphide species. High level multiconfigurational (CASPT2) calculations were performed to assess the structures and bonding of the new AnS22+species obtained for An = Th, Np, as well as for An = Pu to examine trends along the An series, and for An = U to compare with a previous experimental study and DFT computational scrutiny of US22+. The CASPT2 results showed that, like in the case of uranium, the new AnS22+ions have ground states with triangular geometries, corresponding to the presence of a persulphide in the case of thorium that formally leads to a stable ThIVS22+species, while a supersulphide appears to be present in the case of U, Np and Pu, formally leading to a AnIIIS22+species. The computations also revealed that linear thioactinyl structures are higher in energy, with a difference that increases fourfold upon moving from U to Pu, apparently indicating that it will be even more pronounced for Am.
authors.affiliation: Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS, Portugal. jmarcalo@ctn.tecnico.ulisboa.pt.
authors.forename: Ana F
authors.initials: AF
authors.lastname: Lucena
authors.forename: Nuno A G
authors.initials: NAG
authors.lastname: Bandeira
authors.forename: Cláudia C L
authors.initials: CCL
authors.lastname: Pereira
authors.forename: John K
authors.initials: JK
authors.lastname: Gibson
authors.forename: Joaquim
authors.initials: J
authors.lastname: Marçalo