Serres Ricardo García, Grapperhaus Craig A, Bothe Eberhard, Bill Eckhard, Weyhermüller Thomas, Neese Frank, Wieghardt Karl
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
J Am Chem Soc. 2004 Apr 28;126(16):5138-53. doi: 10.1021/ja030645+.
The reaction of low-spin [FeIICl(cyclam-ac)] with NO in CH3CN yields the octahedral, non-heme (nitrosyl)iron complex Fe(NO)(cyclam-ac) (2), S = 1/2, which can be one-electron oxidized with (tris(4-bromophenyl)ammoniumyl)hexachloroantimonate to the complex Fe(NO)(cyclam-ac)2 (1'), S = 0, or complex [Fe(NO)(cyclam-ac)]Cl(ClO4).H2O (1); (cyclam-ac)- represents the pentadentate monoanion of 1,4,8,11-tetraazacyclotetradecane-1-acetic acid. Similarly, in CH3CN solution 2 can be electrochemically or chemically reduced by one-electron to the neutral complex [Fe(NO)(cyclam-ac)]0 (3), S = 0. 1-3 represent members of the [FeNO]6-8 series, respectively. The electronic structure of these three species have been spectroscopically elucidated by EPR, UV-vis, Mössbauer, and IR spectroscopy. The crystal structures of 1 and 2 have been determined by X-ray crystallography. In addition, detailed density functional calculations have been performed for all three species taking into account the possibility that 3 is actually a protonated HNO or NOH species. For all complexes structures, energetics, IR parameters, and Mössbauer parameters as well as EPR parameters (g-values and hyperfine couplings) have been calculated using state-of-the art DFT methods which are compared to experiment. The results establish unequivocally that 3 is indeed the elusive [FeNO]8 species. Furthermore a detailed picture of the bonding in the low-spin non-heme iron nitrosyl series [FeNO]6, [FeNO]7, and [FeNO]8 has been developed. This allows a description of 1 as a low-spin ferrous complex containing an N-coordinated NO+, whereas 2 is a low-spin ferrous species with a NO* ligand and 3 is a low-spin ferrous complex with a coordinated NO-. On the basis of this description, all spectroscopic and geometric observables find a satisfactory interpretation.
低自旋的[FeIICl(环胺 - ac)]与CH3CN中的NO反应生成八面体、非血红素（亚硝酰基）铁配合物Fe(NO)(环胺 - ac) (2)，S = 1/2，它可以被（三（4 - 溴苯基）铵基）六氯锑酸盐单电子氧化为配合物Fe(NO)(环胺 - ac)2 (1')，S = 0，或配合物[Fe(NO)(环胺 - ac)]Cl(ClO4).H2O (1)；(环胺 - ac)-代表1,4,8,11 - 四氮杂环十四烷 - 1 - 乙酸的五齿单阴离子。类似地，在CH3CN溶液中，2可以通过单电子进行电化学或化学还原为中性配合物[Fe(NO)(环胺 - ac)]0 (3)，S = 0。1 - 3分别代表[FeNO]6 - 8系列的成员。这三种物质的电子结构已通过EPR、紫外 - 可见、穆斯堡尔和红外光谱进行了光谱学阐释。1和2的晶体结构已通过X射线晶体学确定。此外，考虑到3实际上可能是质子化的HNO或NOH物种的可能性，对所有三种物质进行了详细的密度泛函计算。对于所有配合物的结构、能量学、红外参数、穆斯堡尔参数以及EPR参数（g值和超精细耦合），已使用与实验进行比较的先进DFT方法进行了计算。结果明确确定3确实是难以捉摸的[FeNO]8物种。此外，还建立了低自旋非血红素铁亚硝酰基系列[FeNO]6、[FeNO]7和[FeNO]8中键合的详细图景。这使得可以将1描述为含有N配位的NO +的低自旋亚铁配合物，而2是具有NO*配体的低自旋亚铁物种，3是具有配位NO -的低自旋亚铁配合物。基于此描述，所有光谱和几何观测结果都得到了令人满意的解释。
