非血红素二价铁配合物与O₂反应中两种不同加合物的表征。
Characterization of two distinct adducts in the reaction of a nonheme diiron(II) complex with O2.
作者信息
Frisch Jonathan R, Vu Van V, Martinho Marlène, Münck Eckard, Que Lawrence
机构信息
Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA.
出版信息
Inorg Chem. 2009 Sep 7;48(17):8325-36. doi: 10.1021/ic900961k.
Two Fe(II)(2)(N-EtHPTB)(mu-O(2)X) complexes, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O(2)X is O(2)PPh(2) (1 x O(2)PPh(2)) or O(2)AsMe(2) (1 x O(2)AsMe(2)), have been synthesized. Their crystal structures both show interiron distances of 3.54 A that arise from a (mu-alkoxo)diiron(II) core supported by an O(2)X bridge. These diiron(II) complexes react with O(2) at low temperatures in MeCN (-40 degrees C) and CH(2)Cl(2) (-60 degrees C) to form long-lived O(2) adducts that are best described as (mu-eta(1):eta(1)-peroxo)diiron(III) species (2 x O(2)X) with nu(O-O) approximately 850 cm(-1). Upon warming to -30 degrees C, 2 x O(2)PPh(2) converts irreversibly to a second (mu-eta(1):eta(1)-peroxo)diiron(III) intermediate (3 x O(2)PPh(2)) with nu(O-O) approximately 900 cm(-1), a value which matches that reported for Fe(2)(N-EtHPTB)(O(2))(O(2)CPh) (3 x O(2)CPh) (Dong et al. J. Am. Chem. Soc. 1993, 115, 1851-1859). Mossbauer spectra of 2 x O(2)PPh(2) and 3 x O(2)PPh(2) indicate that the iron centers within each species are antiferromagnetically coupled with J approximately 60 cm(-1), while extended X-ray absorption fine structure analysis reveals interiron distances of 3.25 and 3.47 A for 2 x O(2)PPh(2) and 3 x O(2)PPh(2), respectively. A similarly short interiron distance (3.27 A) is found for 2 x O(2)AsMe(2). The shorter interiron distance associated with 2 x O(2)PPh(2) and 2 x O(2)AsMe(2) is proposed to derive from a triply bridged diiron(III) species with alkoxo (from N-EtHPTB), 1,2-peroxo, and 1,3-O(2)X bridges, while the longer distance associated with 3 x O(2)PPh(2) results from the shift of the O(2)PPh(2) bridge to a terminal position on one iron. The differences in nu(O-O) are also consistent with the different interiron distances. It is suggested that the O...O bite distance of the O(2)X moiety affects the thermal stability of 2 x O(2)X, with the O(2)X having the largest bite distance (O(2)AsMe(2)) favoring the 2 x O(2)X adduct and the O(2)X having the smallest bite distance (O(2)CPh) favoring the 3 x O(2)X adduct. Interestingly, neither 3 x O(2)AsMe(2) nor the benzoate analog of 2 x O(2)X (2 x O(2)Bz) are observed.
合成了两种[Fe(II)₂(N - EtHPTB)(μ - O₂X)]²⁺配合物，其中N - EtHPTB是N,N,N',N'-四(2 - 苯并咪唑基甲基)-2 - 羟基 - 1,3 - 二氨基丙烷的阴离子，O₂X为O₂PPh₂(1×O₂PPh₂)或O₂AsMe₂(1×O₂AsMe₂)。它们的晶体结构均显示铁原子间距离为3.54 Å，这源于由O₂X桥支撑的(μ - 烷氧基)二价铁(II)核心。这些二价铁(II)配合物在低温下于乙腈(-40℃)和二氯甲烷(-60℃)中与O₂反应，形成寿命较长的O₂加合物，最好将其描述为(μ - η¹:η¹ - 过氧)二价铁(III)物种(2×O₂X)，其ν(O - O)约为850 cm⁻¹。升温至-30℃时，2×O₂PPh₂不可逆地转化为第二种(μ - η¹:η¹ - 过氧)二价铁(III)中间体(3×O₂PPh₂)，其ν(O - O)约为900 cm⁻¹，该值与[Fe₂(N - EtHPTB)(O₂)(O₂CPh)]²⁺(3×O₂CPh)报道的值相符(Dong等人，《美国化学会志》，1993年，115卷，1851 - 1859页)。2×O₂PPh₂和3×O₂PPh₂的穆斯堡尔谱表明，每个物种中的铁中心通过约60 cm⁻¹的J值反铁磁耦合，而扩展X射线吸收精细结构分析显示，2×O₂PPh₂和3×O₂PPh₂的铁原子间距离分别为3.25 Å和3.47 Å。对于2×O₂AsMe₂也发现了类似的短铁原子间距离(3.27 Å)。推测与2×O₂PPh₂和2×O₂AsMe₂相关的较短铁原子间距离源于具有烷氧基(来自N - EtHPTB)、1,2 - 过氧和1,3 - O₂X桥的三桥连二价铁(III)物种，而与3×O₂PPh₂相关的较长距离是由于O₂PPh₂桥转移到一个铁原子上的末端位置。ν(O - O)的差异也与不同的铁原子间距离一致。有人认为O₂X部分的O...O咬距影响2×O₂X的热稳定性，咬距最大的O₂X(O₂AsMe₂)有利于2×O₂X加合物，咬距最小的O₂X(O₂CPh)有利于3×O₂X加合物。有趣的是，未观察到3×O₂AsMe₂或2×O₂X的苯甲酸酯类似物(2×O₂Bz)。
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