Synthetically Reversible, Proton-Mediated Nitrite N-O Bond Cleavage at a Dicopper Site.

A monocationic dicopper(I,I) nitrite complex [Cu(μ-κ:κ-ON)DPFN][NTf] () (DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine, NTf = N(SOCF)), was synthesized by treatment of a dicopper acetonitrile complex, [Cu(μ-MeCN)DPFN][NTf] (), with tetrabutylammonium nitrite ([BuN][NO]). DFT calculations indicate that is one of three linkage isomers that are close in energy and presumably accessible in solution. Reaction of the μ-κ:κ-ON complex with -TolSH produces nitrous acid (HONO) and the corresponding dicopper thiolate species via an acid-base exchange reaction. Notably, treatment of with HNTf results in N-O bond cleavage in the putative, HONO-ligated complex to form the more thermodynamically favorable nitrosyl-bridged dicopper complex [Cu(μ-NO)(μ-OH)DPFN][NTf] (). This scission can be reversed via deprotonation of the hydroxy ligand with KOBu. X-ray diffraction studies confirmed the solid-state molecular structures of and . DFT calculations were used to construct a reaction coordinate diagram detailing formation of the μ-NO complex and to describe its electronic structure. The nitrosyl ligand in is chemically labile, as demonstrated by its ready displacement in reactions with CO or NO.