Tris(pyrazolyl)phosphine oxides. Synthesis and coordination chemistry with copper(I)

Article abstract of DOI:10.1021/om300051f

A set of substituted tris(pyrazolyl)phosphine oxides (OP(pz ^x)₃) has been prepared in high yield and applied as neutral scorpion-type ligands. The P apex provides a convenient spectroscopic handle. Substitution at the 3-position of the pyrazolyl ring influences the steric demands of the ligand, while substitution at the 5-position enhances the stability. Copper(I) acetonitrile complexes of the OP(pz^x) ₃ ligands were prepared and tested in ligand exchange reactions with PPh₃ and CO. The v(CO) values of the carbonyl complexes demonstrate the electron-withdrawing properties of the ligands. These observations show that OP(pz^x)₃ ligands are an interesting extension of the widely used scorpion-type ligands.