title: The shortest Th-Th distance from a new type of quadruple bond.
abstract: Compounds featuring unsupported metal-metal bonds between actinide elements remain highly sought after yet confined experimentally to inert gas matrix studies. Notwithstanding this paucity, actinide-actinide bonding has been the subject of extensive computational research. In this contribution, high level quantum chemical calculations at both the scalar and spin-orbit levels are used to probe the Th-Th bonding in a range of zero valent systems of general formula LThThL. Several of these compounds have very short Th-Th bonds arising from a new type of Th-Th quadruple bond with a previously unreported electronic configuration featuring two unpaired electrons in 6d-based δ bonding orbitals. H3AsThThAsH3is found to have the shortest Th-Th bond yet reported (2.590 Å). The Th2unit is a highly sensitive probe of ligand electron donor/acceptor ability; we can tune the Th-Th bond from quadruple to triple, double and single by judicious choice of the L group, up to 2.888 Å for singly-bonded ONThThNO.
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK. nikolas.kaltsoyannis@manchester.ac.uk.
authors.forename: Han-Shi
authors.initials: HS
authors.lastname: Hu
authors.affiliation: School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK. nikolas.kaltsoyannis@manchester.ac.uk.
authors.forename: Nikolas
authors.identifier: http://orcid.org/0000-0003-0293-5742
authors.initials: N
authors.lastname: Kaltsoyannis