NO sub(2) bond cleavage by MoL sub(3) complexes

• Published in: Dalton transactions : an international journal of inorganic chemistry 2013-12, Vol.43 (4), p.1620-1629
• Main Authors: Shaw, Miranda F, Mahdizadeh Ghohe, Narges, Ariafard, Alireza, Brookes, Nigel J, Stranger, Robert, Yates, Brian F
• Format: Article
• Language: English
• Subjects: Barriers; Bonding; Cleavage; Equivalence; Formations; Isomers; Ligands; Nitrogen dioxide
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c3dt52554f

The cleavage of one N-O bond in NO sub(2) by two equivalents of Mo(NRAr) sub(3) has been shown to occur to form molybdenum oxide and nitrosyl complexes. The mechanism and electronic rearrangement of this reaction was investigated using density functional theory, using both a model Mo(NH sub(2)) sub(3) system and the full [N( super(t)Bu)(3,5-dimethylphe nyl)] experimental ligand. For the model ligand, several possible modes of coordination for the resulting complex were observed, along with isomerisation and bond breaking pathways. The lowest barrier for direct bond cleavage was found to be viathe singlet eta super(2)-N,O complex (7 kJ mol super(-1)). Formation of a bimetallic species was also possible, giving an overall decrease in energy and a lower barrier for reaction (3 kJ mol super(-1)). Results for the full ligand showed similar trends in energies for both isomerisation between the different isomers, and for the mononuclear bond cleavage. The lowest calculated barrier for cleavage was only 21 kJ mol super(-1)viathe triplet eta super(1)-O isomer, with a strong thermodynamic driving force to the final products of the doublet metal oxide and a molecule of NO. Formation of the full ligand dinuclear complex was not accompanied by an equivalent decrease in energy seen with the model ligand. Direct bond cleavage viaan eta super(1)-O complex is thus the likely mechanism for the experimental reaction that occurs at ambient temperature and pressure. Unlike the other known reactions between MoL sub(3) complexes and small molecules, the second equivalent of the metal does not appear to be necessary, but instead irreversibly binds to the released nitric oxide.