Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA.
Inorg Chem. 2011 May 2;50(9):4107-15. doi: 10.1021/ic200143b. Epub 2011 Mar 29.
A series of coordination compounds has been prepared comprising manganese, iron, nickel, and zinc bound by a hexaanionic cryptand where carboxamides are anionic N-donors. The metal complexes have been investigated by X-ray crystallography, and possess metal centers in trigonal monopyramidal geometries with intermetallic distances spanning d(Mn,avg) = 6.080 Å to d(Ni,avg) = 6.495 Å. All complexes featuring trigonal monopyramidal metal(II) ions crystallize in Cc, and feature extended three-dimensional networks composed of cryptate anions linked by bridging potassium countercations. We also report the first solid state structure of the free cryptand ligand, which features no guest in its cavity and which possesses an extended hydrogen-bonding network. SQuID magnetometry data of the metal complexes reveal weak antiferromagnetic coupling of the metal centers. Only the diiron(II) complex exhibits reversible electrochemistry, and correspondingly, its chemical oxidation yields a powder formulated as the diiron(III) congener. The insertion of cyanide into the intermetallic cleft of the diiron(II) complex has been achieved, and comparisons of its solid state structure to the recently reported dicobalt(II) analogue are made. The antiferromagnetic coupling between the diiron(II) and the dicobalt(II) centers when bridged by cyanide does not increase significantly relative to the unbridged congeners. A one-site model satisfactorily fits Mössbauer spectra of unbridged diiron(II) and diiron(III) complexes whereas a two site fit was needed to model the iron(II) centers that are bridged by cyanide.
一系列包含锰、铁、镍和锌的配位化合物已经被制备出来，它们由一个六元阴离子cryptand 结合，其中羧酸酰胺是阴离子 N-供体。这些金属配合物已经通过 X 射线晶体学进行了研究，具有三角单锥几何形状的金属中心，金属间距离跨越 d（Mn，平均值）= 6.080 Å 至 d（Ni，平均值）= 6.495 Å。所有具有三角单锥金属（II）离子的配合物都在 Cc 中结晶，并具有由cryptate 阴离子通过桥接的钾抗衡阳离子连接的扩展三维网络。我们还报告了游离 cryptand 配体的第一个固态结构，其腔体内没有客体，并且具有扩展的氢键网络。金属配合物的 SQuID 磁强计数据显示金属中心之间存在弱反铁磁耦合。只有二铁（II）配合物表现出可逆电化学，相应地，其化学氧化生成粉末形式的二铁（III）同系物。已经实现了氰化物插入二铁（II）配合物的金属间空隙中，并对其固态结构与最近报道的二钴（II）类似物进行了比较。当氰化物桥接二铁（II）和二钴（II）中心时，反铁磁耦合没有相对于未桥接的同系物显著增加。一个单位点模型令人满意地拟合了未桥接的二铁（II）和二铁（III）配合物的穆斯堡尔谱，而需要两个位点模型来模拟由氰化物桥接的铁（II）中心。
