Monoanionic salicylaldimine ligands with (thio)phosphoryl pendant arms: Synthesis and complexing features

Michael addition of P-nucleophiles to azoalkenes provides simple access to phosphine oxides bearing an alkylhydrazone moiety

β-Hydrazonophosphine oxides are precursors of useful organophosphorus compounds, including phosphorylated N-heterocycles, α-aminophosphonates, and vinylphosphonates. In this work, a general transition metal-free synthesis of β-hydrazonophosphine oxides was developed. The method relies on the Michael addition of phosphine oxides R₂P(O)H to reactive azoalkenes (1,2-diaza-1,3-butadienes), which are generated in situ from α-halohydrazones and Hunig's base. The reaction stereoselectively leads to Z-isomers of β-hydrazonophosphine oxides that are stabilized by intramolecular hydrogen bonding. The conversion of the products thus obtained into potential chelating ligands was showcased.

Structural comparison of group 7 tricarbonyl complexes of 2-{[2-(1H-imidazol-4-yl)ethyl]iminomethyl}-5-methylphenolate

Two tricarbonyl complexes of rhenium(I) and manganese(I) coordinated by the ligand 2-{[2-(1H-imidazol-4-yl)ethyl]iminomethyl}-5-methylphenolate are reported, viz. fac-tricarbonyl(2-{[2-(1H-imidazol-4-yl-κN(3))ethyl]iminomethyl-κN}-5-methylphenolato-κO)rhenium(I) methanol monosolvate, [Re(C16H14N3O4)(CO)3]·CH3OH, (I), and fac-tricarbonyl(2-{[2-(1H-imidazol-4-yl-κN(3))ethyl]iminomethyl-κN}-5-methylphenolato-κO)manganese(I), fac-[Mn(C16H14N3O4)(CO)3], (II), display facial coordination in a distorted octahedral environment. The crystal structure of (I) is stabilized by O-H···O, N-H···O and C-H···O hydrogen-bond interactions, while that of (II) is stabilized by N-H...O hydrogen-bond interactions only. These interactions result in two-dimensional networks and π-π stacking for both structures.