Chun Hyungphil, Bill Eckhard, Weyhermüller Thomas, Wieghardt Karl
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
Inorg Chem. 2003 Sep 8;42(18):5612-20. doi: 10.1021/ic0301526.
Five-coordinate halido- and pseudohalido-bis(o-iminobenzosemiquinonato)iron(III) complexes [Fe(III)X(L(ISQ))(2)] (X = Cl(-) (1), Br(-) (2a, 2b), I(-) (3), N(3)(-) (4), and NCS(-) (5)) have been synthesized where (L(ISQ))(1)(*)(-) represents the pi radical anion N-phenyl-o-imino(4,6-di-tert-butyl)benzosemiquinonate(1-). The molecular structures of the two polymorphs 2a and 2b have been determined at 100, 220, and 295 K, respectively, by single crystal X-ray crystallography. Variable temperature magnetic susceptibility data reveal the following electronic ground states, S(t): For 1, it is (3)/(2). Polymorph 2a contains a 1:1 mixture of (3)/(2) and (1)/(2) forms in the range 4.2 to approximately 150 K; above 150 K the latter form undergoes a spin crossover (1)/(2) --> (3)/(2). Polymorph 2b contains only the S(t) = (3)/(2) form (4-300 K). Complex 3 contains the S(t) = (1)/(2) form in the range 4-130 K, but above 130 K, a spin crossover to the (3)/(2) form is observed which is confirmed by three crystal structure determinations at 100, 220, and 295 K. Complex 4 possesses an S(t) = (1)/(2) ground state at 80 K and undergoes a spin crossover at higher temperatures. Complex 5 has a temperature-independent S(t) = (3)/(2) ground state. All crystal structures of 1, 2a, 2b, 3, 4, and 5, regardless at which temperature the data sets have been measured, show that two o-iminobenzosemiquinonate(1-) pi radical anions are N,O-coordinated in all of these neutral iron complexes. The Fe-N and Fe-O bond distances are longer in the S(t) = (3)/(2) and shorter in the S(t) = (1)/(2) forms. The S(t) = (3)/(2) ground state is attained via intramolecular antiferromagnetic coupling between a high spin ferric ion (S(Fe) = (5)/(2)) and two ligand pi radicals whereas the S(t) = (1)/(2) form is generated from exchange coupling between an intermediate spin ferric ion (S(Fe) = (3)/(2)) and two ligand radicals.
已合成五配位卤代和拟卤代双（邻亚胺苯半醌）铁（III）配合物[Fe(III)X(L(ISQ))₂]（X = Cl⁻（1）、Br⁻（2a、2b）、I⁻（3）、N₃⁻（4）和NCS⁻（5）），其中(L(ISQ))₁⁻代表π自由基阴离子N - 苯基 - 邻亚胺基（4,6 - 二叔丁基）苯半醌（1 - ）。通过单晶X射线晶体学分别在100 K、220 K和295 K下测定了两种多晶型物2a和2b的分子结构。变温磁化率数据揭示了以下电子基态S(t)：对于1，其为³/₂。多晶型物2a在4.2至约150 K范围内包含³/₂和¹/₂形式的1:1混合物；在150 K以上，后一种形式发生自旋交叉¹/₂→³/₂。多晶型物2b仅包含S(t) = ³/₂形式（4 - 300 K）。配合物3在4 - 130 K范围内包含S(t) = ¹/₂形式，但在130 K以上，观察到向³/₂形式的自旋交叉，这通过在100 K、220 K和295 K下的三次晶体结构测定得到证实。配合物4在80 K时具有S(t) = ¹/₂基态，并在较高温度下发生自旋交叉。配合物5具有与温度无关的S(t) = ³/₂基态。1、2a、2b、3、4和5的所有晶体结构，无论数据集是在哪个温度下测量的，都表明在所有这些中性铁配合物中，两个邻亚胺苯半醌（1 - ）π自由基阴离子通过N、O配位。在S(t) = ³/₂形式中，Fe - N和Fe - O键长较长，而在S(t) = ¹/₂形式中较短。S(t) = ³/₂基态是通过高自旋铁离子（S(Fe) = ⁵/₂）与两个配体π自由基之间的分子内反铁磁耦合实现的，而S(t) = ¹/₂形式是由中间自旋铁离子（S(Fe) = ³/₂）与两个配体自由基之间的交换耦合产生的。
