Synthesis, Characterisation and Reactions of Truly Cationic Ni -Phosphine Complexes.

The recently published purely metallo-organic Ni salt [Ni(cod) ][Al(OR ) ] (1, cod=1,5-cyclooctadiene, R =C(CF ) ) provides a starting point for a new synthesis strategy leading to Ni phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp) ][Al(OR ) ] (2, dppp=1,3-bis(diphenylphosphino)propane), [Ni(dppe) ][Al(OR ) ] (3, dppe=1,3-bis(diphenyl-phosphino)ethane), three-coordinate [Ni(PPh ) ][Al(OR ) ] (4) and a remarkable two-coordinate Ni phosphine complex [Ni(PtBu ) ][Al(OR ) ] (5) were characterised by single crystal X-ray structure analysis.