Synthesis, structure, and paramagnetism of manganese(II) iminophosphate complexes

The coordination chemistry of the bidentate bis(imino)bis(amino)phosphate ligands [Me 3SiN-P{NR}{N(H)R} 2] -, where R = n-propyl is [L 1H 2] -, R = cyclohexyl is [L 2H 2] -, and R = tert-butyl is [L 3H 2] -, with manganese(II), is described. The bis(imino)bis(amino)phosphate-manganese(II) complexes [(≠ 5-Cp) Mn(μ-L 1H 2)] 2 (1), [Mn(L 2H 2) 2]·THF (2·THF), and [(≠ 5-Cp) Mn(L 3H 2)] (3) were synthesized by monodeprotonation of the respective pro-ligands by manganocene, Cp 2Mn. The molecular structures of 1-3 reveal that the steric demands of the ligand N-substituents play a dominant role in determining the aggregation state and overall composition of the manganese(II) complexes. The coordination geometries of the Mn(II) centers are six-coordinate pseudotetrahedral in 1, four-coordinate distorted tetrahedral in 2, and five-coordinate in 3, resulting in formal valence electron counts of 17, 13, and 15, respectively. EPR studies of 1-3 at Q-band reveal high-spin manganese(II) (S = 5/ 2) in each case. In the EPR spectrum of 1, no evidence of intramolecular magnetic exchange was found. The relative magnitudes of the axial zero-field splitting parameter, D, in 2 and 3 are consistent with the symmetry of the manganese environment, which are D 2d in 2 and C 2v in 3. © 2012 American Chemical Society.