Mao Jiang-Gao, Clearfield Abraham
Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA.
Inorg Chem. 2002 May 6;41(9):2319-24. doi: 10.1021/ic011094w.
Two novel divalent metal complexes with N-(phosphonomethyl)iminodiacetic acid, H(2)O(3)PCH(2)N(CH(2)CO(2)H)(2) (H(4)PMIDA), [Co(2)(PMIDA)(H(2)O)(5)] x H(2)O, 1, and [Zn(2)(PMIDA)(CH(3)CO(2)H)] x 2H(2)O, 2, have been synthesized and structurally characterized. The structure of complex 1 features two different kinds of Co(II) layers, namely, a cobalt phosphonate layer along the <100> plane and a cobalt carboxylate layer along the <300> plane. The Co(II) atoms in the phosphonate layer are octahedrally coordinated by 4 aqua ligands and 2 oxygen atoms from two phosphonic acid groups. Two Co(II) octahedra are bridged by a pair of phosphonic groups into a dimeric unit, and such dimers are interconnected into a layer through hydrogen bonding between aqua ligands. The Co(II) atoms in the carboxylate layer are octahedrally coordinated by a chelating PMIDA ligand, one aqua ligand, and one phosphonic oxygen atom from the neighboring PMIDA ligand. These Co(II) octahedra are interlinked by bridging carboxylic groups into a one-dimensional chain along the c-axis; such chains are held together by hydrogen bonds formed between carboxylic oxygen atoms and lattice water molecules, in such a way as to form a layer along the <300> direction. Two such layers are interconnected into a double layer via hydrogen bonding. These double layers are further interconnected with the Co(II) phosphonate layers through phosphonate tetrahedra along the a direction, resulting in the formation of a complicated three-dimensional network. The crystal structure of 2 contains a metal phosphonate and metal carboxylate hybrid layer along the <202> plane. One of the two zinc atoms in the asymmetric unit is tetrahedrally coordinated by four oxygen atoms from two phosphonic acid groups and two carboxylic groups; the other zinc atom is 5-coordinated by three oxygen atoms and a nitrogen atom from a chelating PMIDA ligand and one oxygen atom from the acetic acid. The above two types of zinc metal ions are interconnected by bridging carboxylic and phosphonic groups, resulting in the formation of a layered structure.
合成并表征了两种新型的与N-(膦酰甲基)亚氨基二乙酸（H₂O₃PCH₂N(CH₂CO₂H)₂，H₄PMIDA）形成的二价金属配合物，即[Co₂(PMIDA)(H₂O)₅]·H₂O（1）和[Zn₂(PMIDA)(CH₃CO₂H)]·2H₂O（2）。配合物1的结构具有两种不同类型的Co(II)层，即沿<100>平面的钴膦酸盐层和沿<300>平面的钴羧酸盐层。膦酸盐层中的Co(II)原子由4个水分子配体和来自两个膦酸基团的2个氧原子八面体配位。两个Co(II)八面体通过一对膦酸基团桥连形成一个二聚体单元，并且这些二聚体通过水分子配体之间的氢键相互连接成一层。羧酸盐层中的Co(II)原子由一个螯合的PMIDA配体、一个水分子配体和来自相邻PMIDA配体的一个膦酸氧原子八面体配位。这些Co(II)八面体通过桥连的羧基沿着c轴相互连接成一维链；这样的链通过羧基氧原子与晶格水分子之间形成的氢键聚集在一起，从而沿着<300>方向形成一层。两个这样的层通过氢键相互连接成双层。这些双层通过沿a方向的膦酸四面体与Co(II)膦酸盐层进一步相互连接，形成一个复杂的三维网络。配合物2的晶体结构包含沿<202>平面的金属膦酸盐和金属羧酸盐混合层。不对称单元中的两个锌原子之一由来自两个膦酸基团的四个氧原子和两个羧基四面体配位；另一个锌原子由来自螯合的PMIDA配体的三个氧原子和一个氮原子以及来自乙酸的一个氧原子五配位。上述两种类型的锌金属离子通过桥连的羧基和膦酸基团相互连接，形成层状结构。
