Synthesis, Structure, and Paramagnetism of Manganese(II) Iminophosphate Complexes

The coordination chemistry of the bidentate bis­(imino)­bis­(amino)­phosphate ligands [Me3SiNP­{NR}­{N­(H)­R}2]−, where R = n-propyl is [L1H2]−, R = cyclohexyl is [L2H2]−, and R = tert-butyl is [L3H2]−, with manganese­(II), is described. The bis­(imino)­bis­(amino)­phosphate-manganese­(II) complexes [(η5-Cp)­Mn­(μ-L1H2)]2 (1), [Mn­(L2H2)2]·THF (2·THF), and [(η5-Cp)­Mn­(L3H2)] (3) were synthesized by monodeprotonation of the respective pro-ligands by manganocene, Cp2Mn. 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 D2d in 2 and C2v in 3.