Diphosphorus Release and Heterocumulene Oligomerisation by Nickel Complexes

The generation of diphosphorus molecules P-2 under mild conditions in solution is a useful strategy to generate diphosphines via [4+2] cycloadditions. We recently described the release of P-2 units from the nickel butterfly complex [{(IMes)Ni(CO)}(2)(mu(2),eta(2):eta(2)-P-2)] (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) upon addition of CO gas. Herein, we developed an alternative protocol for the same process using heterocumulenes. In addition to formation of P-4 (the dimerisation product of P-2), the reactions afford nickel complexes of novel pincer-type ligands. Aryl isothiocyanates undergo a trimerisation within the coordination sphere of nickel and afford square planar nickel complexes with S-C-S pincer-ligand frameworks. Carbon disulfide coordinates to the [(IMes)Ni]-fragment in an eta(2)-fashion, affording a dinuclear complex. Similar products are formed when the N-heterocyclic carbene nickel(0) complex [(IMes)Ni(vtms)(2)] is used as a precursor (vtms=vinyltrimethylsilane).

Automated summary

The generation of diphosphorus molecules P-2 under mild conditions in solution is a useful strategy to generate diphosphines via [4+2] cycloadditions. Here, we developed an alternative protocol for the same process using heterocumulenes, which not only produces the dimerization product of P-2, P-4, but also forms nickel complexes of novel pincer-type ligands.