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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Methylene-bis[(aminomethyl)phosphinic acids]: Synthesis, acid-base and coordination properties
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Methylene-bis[(aminomethyl)phosphinic acids]: Synthesis, acid-base and coordination properties

机译：亚甲基双[（氨基甲基）次膦酸]：合成，酸碱和配位性能

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摘要

Three symmetrical methylene-bis[(aminomethyl)phosphinic acids] bearing different substituents on the central carbon atom, (NH_2CH_2)PO_2H-C(R1)(R2)-PO _2H(CH_2NH_2) where R~1 = OH, R~2 = Me (H_2L1), R~1 = OH, R~2 = Ph (H_2L~2) and R1,R2 = H (H_2L~3), were synthesized. Acid-base and complexing properties of the ligands were studied in solution as well as in the solid state. The ligands show unusually high basicity of the nitrogen atoms (log K_1 = 9.5-10, log K_2 = 8.5-9) if compared with simple (aminomethyl)phosphinic acids and, consequently, high stability constants of the complexes with studied divalent metal ions. The study showed the important role of the hydroxo group attached to the central carbon atom of the geminal bis(phosphinate) moiety. Deprotonation of the hydroxo group yields the alcoholate anion which tends to play the role of a bridging ligand and induces formation of polynuclear complexes. Solid-state structures of complexes [H_2NC(NH_2)_2][Cu_2(H_(-1)L 2)_2]CO_3·10H_2O and Li_2[Co_4(H_(-1)L_1)_3(OH)] ·17.5H_2O were determined by X-ray diffraction. The complexes show unexpected geometries forming dinuclear and cubane-like structures, respectively. The dinuclear copper(ii) complex contains a bridging μ2-alcoholate group with the -O-P(O)-CH~(2-)NH_2 fragments of each ligand molecule chelated to the different central ion. In the cubane cobalt(ii) complex, one μ3-hydroxide and three μ3-alcoholate anions are located in the cube vertices and both phosphinate groups of one ligand molecule are chelating the same cobalt(ii) ion while each of its amino groups are bound to different neighbouring metal ions. All such three metal ions are bridged by the alcoholate group of a given ligand.
机译：在中心碳原子上带有不同取代基的三个对称的亚甲基双[（氨基甲基）次膦酸]，（NH_2CH_2）PO_2H-C（R1）（R2）-PO _2H（CH_2NH_2），其中R〜1 = OH，R〜2 =合成了Me（H_2L1），R〜1 = OH，R〜2 = Ph（H_2L〜2）和R1，R2 = H（H_2L〜3）。在溶液以及固态下都研究了配体的酸碱和络合特性。如果与简单的（氨基甲基）次膦酸相比，该配体显示出异常高的氮原子碱性（log K_1 = 9.5-10，log K_2 = 8.5-9），因此，具有研究的二价金属离子的配合物具有很高的稳定性常数。研究表明，羟基与双（次膦酸酯）双键中心碳原子相连。羟基的去质子化产生醇化物阴离子，其倾向于起桥联配体的作用并诱导多核络合物的形成。配合物[H_2NC（NH_2）_2] [Cu_2（H _（-1）L 2）_2] CO_3·10H_2O和Li_2 [Co_4（H _（-1）L_1）_3（OH）]·17.5H_2O的固态结构为通过X射线衍射测定。配合物显示出意想不到的几何形状，分别形成双核和类古巴结构。双核铜（ii）配合物包含一个桥接的2-醇基团，每个配体分子的-O-P（O）-CH〜（2-）NH_2片段螯合到不同的中心离子上。在古巴钴（ii）络合物中，一个μ3-氢氧化物和三个μ3-醇酸根阴离子位于立方体顶点，并且一个配体分子的两个次膦酸酯基螯合相同的钴（ii）离子，而其每个氨基都被结合到不同的相邻金属离子。所有这三种金属离子均通过给定配体的醇基桥接。

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