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)

Two new sterically demanding iminophosphonamine ligands (2,4,6-Me3C6H2NH)P(Ph-2)=N (C6H2-2,4,6-Me-3) (1) and (2,6-iPr(2)C(6)H(3)NH)P(Ph-2)=N(C6H2-2,4,6-Me-3) (2) and their lithium derivatives as tmeda adducts (Li.tmeda)[(2,4,6-Me3C6H2)NP(Ph-2)=N(C6H2-2,4,6-Me-3)] (3) and (Li.tmeda)[(2,6-iPr(2)C(6)H(3))NP(Ph-2)=N(C6H2-2,4,6-Me-3)] (4), respectively are reported here. Compounds 1-4 have been investigated by H-1, C-13 and P-13{H-1} NMR spectroscopy. The Li-7 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-Me-3)(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.