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A Valence‐Delocalised Osmium Dimer capable of Dinitrogen Photocleavage: Ab Initio Insights into Its Electronic Structure
Author(s) -
Krewald Vera,
González Leticia
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704651
Subject(s) - osmium , ab initio , dimer , valence (chemistry) , chemistry , electronic structure , computational chemistry , catalysis , ruthenium , organic chemistry
The search for molecular catalysts that efficiently activate or cleave the dinitrogen molecule is an active field of research. While many thermal dinitrogen cleavage catalysts are known, the photochemical activation of N 2 has received considerably less attention. In this paper, the first computational study of the osmium dimer [Os (II,III) 2 (μ‐N 2 )(NH 3 ) 10 ] 5+ , which was shown to be capable of dinitrogen photocleavage, is presented. Despite its deceptively simple geometry, it has a complex electronic structure with a valence‐delocalized and electronically degenerate ground state. Using multiconfigurational methods, the electronic structure at the ground state geometry and along the dinitrogen cleavage coordinate was investigated. The results indicate that an unoccupied molecular orbital with σ‐bonding character between osmium and μ‐N atoms and σ‐antibonding dinitrogen character is most affected by N–N distance elongation. This implies that a lower barrier for thermal or photochemical N 2 activation in linear M‐N‐N‐M complexes can be achieved by lowering the energetic separation between this unoccupied orbital and the HOMO, representing a specific target for future catalyst design.