Taming copper(I) cyanate and selenocyanate with N-heterocyclic carbenes

The synthesis of N-heterocyclic carbene (NHC) adducts of copper(I) cyanate and copper(I) selenocyanate has been successfully achieved via the reaction of [Cu(NHC)Cl] with silver(I) cyanate and potassium selenocyanate respectively. Three copper(I) cyanate complexes [Cu(IXy)(NCO)] (1), [Cu(IPr)(NCO)] (2) and [Cu(SIPr)(NCO)] (3) [IXy = 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene, IPr = 1,3- bis(2,6-diisopropylphenyl)imidazol-2-ylidene, SIPr = 1,3-bis(2,6- diisopropylphenyl)imidazolin-2-ylidene] have been prepared and fully characterised. The X-ray crystal structures reveal the three complexes to be monomeric species in which the cyanate ligand is end-on, N-bound. These complexes, represent the first examples of monomeric copper(I) cyanate complexes. In addition, the copper(I) selenocyanate species [Cu(IPr)(NCSe)]2 (4) was prepared and fully characterised. The X-ray crystal structure reveals that a centrosymmetric dimer is formed with bridging selenocyanate ligands bound through both N and Se. This is in contrast to the monomeric structure observed in the previously reported and related complex [Cu(IPr)(NCS)]. Complex 4 represents a rare example of a stable dimeric adduct of copper(I) selenocyanate.