Bulky iminophosphonamines for N–P–N coordination: Synthesis and structural characterization of lithium iminophosphonamides and homoleptic bis-chelates of Co(II), Ni(II) and Cu(II)

Abstract

Two new sterically demanding iminophosphonamine ligands (2,4,6-Me3C6H2NH)P(Ph 2)=N (C6H2-2,4,6-Me3)(1) and (2,6-iPr2C6H3NH)P(Ph2)=N(C6H2-2,4,6-Me3) (2) and their lithium derivatives as tmeda adducts (Li ⋅tmeda)[(2,4,6-Me3C6H2)NP(Ph2)=N(C6H2-2,4,6-Me3)] (3) and (Li ⋅tmeda)[(2,6-iPr2C6H3)NP(Ph2)=N(C6H2-2,4,6-Me3)] (4), respectively are reported here. Compounds 1–4 have been investigated by 1H, 13C and 13 P{1H} NMR spectroscopy. The 7Li NMR for complexes 3 and 4 has also been reported. Utility of the ligands and their lithium derivatives have been shown in the synthesis of bis-homoleptic metal complexes M[Ph2P(NC6H2-2,4,6-Me3)2]2 (M = Co (5), Cu (6) and Ni (7). Metal-bis-silylamide generated in situ was reacted with the ligand (for 5 and 6) or the lithium derivative of the ligand was reacted with the metal chloride (for 7). Molecular structure of compounds 1–7 has been elucidated by single crystal X-ray diffraction analyses. The complexes are formed in good yields and are highly lipophilic in a wide range of solvents. Two new lipophilic members in the iminophosphonamine family have been added including their lithium iminophosphonamides with the Li ion coordinated with tmeda. The first structurally characterized bis-chelate of Cu(II) has also been prepared in this study. The adjoining figure shows perfectly planar N2PNi metallacycle found in bis-chelate of Ni(II)iminophosphonamide.