Synthesis and structural properties of metal complexes of dialkyl α-hydroxyiminophosphonates

Abstract

A range of dialky α-hydroxyiminophosphonates R′C=N(OH)P(O)(OR)₂, with substituents of varying bulk (R = Et, R′ = Me L¹, Et L², ^cPr L³, 3-heptyl L⁴; R = ⁱPr, R′ = Et L⁵, 3-heptyl L⁶; R = ⁿBu, R′ = Pr L⁷) have been used to synthesise neutral metal complexes with nickel(II) [Ni(L^1–3,5)Cl₂], cobalt(II) [Co(L^1–3,5)Cl₂] and lanthanides (La^III with L^1,2,5, Pr^III with L^1,2,4–7, Nd^III with L⁵, Gd^III with L^2,5 and Dy^III with L^2,5) the charge being balanced by anionic ligands chloride or nitrate. Included in this range are two 3-heptyl derivatives which have not previously been reported. All the metal complexes have been fully characterised by elemental analysis, IR, electronic and NMR spectroscopy and mass spectrometry. X-Ray crystallography has been used to establish the structure of six key metal complexes and one of the free ligands (L³). Three different bonding modes have been established. The d-block metal chlorides consistently show symmetrical bidentate coordination in [ML₂Cl₂], the lanthanide chlorides [ML₃Cl₃] are all asymmetrically bidentate and monodentate coordination was observed in the neodymium nitrate complex [NdL⁵₂(NO₃)₃(H₂O)].