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Synthesis, Structure, and Paramagnetism of Manganese(II) Iminophosphate Complexes
文摘
The coordination chemistry of the bidentate bis(imino)bis(amino)phosphate ligands [Me3SiN鈺怭{NR}{N(H)R}2]鈭?/sup>, where R = n-propyl is [L1H2]鈭?/sup>, R = cyclohexyl is [L2H2]鈭?/sup>, and R = tert-butyl is [L3H2]鈭?/sup>, with manganese(II), is described. The bis(imino)bis(amino)phosphate-manganese(II) complexes [(畏5-Cp)Mn(渭-L1H2)]2 (1), [Mn(L2H2)2]路THF (2路THF), and [(畏5-Cp)Mn(L3H2)] (3) were synthesized by monodeprotonation of the respective pro-ligands by manganocene, Cp2Mn. The molecular structures of 1鈥?b>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鈥?b>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.
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