Spectroscopic and structural characterization of O,O′-(diphenylphosphineoxide)amidate and acetylacetonate complexes of pentacoordinate nickel(II)

Heteroleptic nickel pentacoordinate complexes with the macrocyclic ligands 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (Me3-mcN3) or its 9-methyl derivative (Me4-mcN3), as ancillary ligands, and O,O′-(diphenylphosphineoxide)amidate ligands, [RC(O)NP(O)Ph2]¯ (R = C6H6 (1), C5H4N (2), C4H3S (3)), have been prepared as well as related acetylacetonate derivatives. The complexes have been studied by spectroscopic methods (IR, UV–Vis and 1H NMR). In acetone solution, the complexes exhibit isotropically shifted 1H NMR resonances. The full assignment of these resonances has been achieved using one- and two-dimensional 1H NMR techniques. The single-crystal structures of {(Me4-mcN3)Ni[OP(Ph2)NC(Tf)O]}[PF6] (9) and {(Me3-mcN3)Ni(acac)}[PF6] (10) have been established by X-ray diffraction.