The Coordination chemistry of hexamethylphosphoramide

<jats:title>Abstract</jats:title><jats:p>A number of new solvates and adducts containing hexamethylphosphoramide is reported. The solvates have the general formula M{[(CH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>N]<jats:sub>3</jats:sub>PO}<jats:sub>4</jats:sub> <jats:sup>2+</jats:sup>(anion)<jats:sub>2</jats:sub><jats:sup>2−</jats:sup>, in which M = Mg, Ca, Sr, Mn, Fe, Co, Ni, Zn and Cd and the anions are BF<jats:sub>4</jats:sub><jats:sup>−</jats:sup>, ClO<jats:sub>4</jats:sub><jats:sup>−</jats:sup> and B(C<jats:sub>6</jats:sub>H<jats:sub>5</jats:sub>)<jats:sub>4</jats:sub><jats:sup>−</jats:sup>. The adducts have the general formula M(anion)<jats:sub>n</jats:sub> {[(CH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>N]<jats:sub>3</jats:sub>PO}<jats:sub>m</jats:sub>, in which M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn, Cd, Al, Cr, Fe, Mo, n = 1 − 3, m = 1/2 − 5 and the anions are Cl<jats:sup>−</jats:sup>, Br<jats:sup>−</jats:sup>, I<jats:sup>−</jats:sup>, NO<jats:sub>3</jats:sub><jats:sup>−</jats:sup>, NCS<jats:sup>−</jats:sup>, CH<jats:sub>3</jats:sub>COO<jats:sup>−</jats:sup> and SO<jats:sub>4</jats:sub><jats:sup>2−</jats:sup>.</jats:p><jats:p>The compounds are characterized and identified by chemical analysis and physical measurements.</jats:p><jats:p>Infrared spectra in the region 4000‐200 cm<jats:sup>−1</jats:sup> have been investigated. The shift towards lower wave numbers in the P‐O stretching frequency and towards higher wave numbers in the P‐O bending frequency of the complexes is discussed. It is concluded, as has been suggested by other workers, that coordination takes place <jats:italic>via</jats:italic> the oxygen atom. A tentative assignment for the other ligand bands is proposed.</jats:p><jats:p>Ligand‐field spectra for the complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Cr(III) and Mo(III) have been investigated. Adapted values for Dq and B are reported and the ligand is placed in the spectrochemical and nephelauxetic series.</jats:p><jats:p>In agreement with results obtained by other workers it is concluded that if the anions are present as uncoordinated ions, or participate in the coordination as monodentate ligands, hexamethylphosphoramide has a tendency to form tetrahedrally surrounded complexes. With potential polydentate anions octahedrally surrounded cations are mostly found.</jats:p>