Reynolds III R. A., Dunham W. R., Coucouvanis D.
Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055.
Inorg Chem. 1998 Mar 23;37(6):1232-1241. doi: 10.1021/ic971537p.
The dimeric [M(2)(OAc)(5)(py)(2)&mgr;-(OH(2))]Et(4)N complexes, I (M = Mn, Fe, Co), have been isolated from pyridine solutions of M(II)(OAc)(2).xH(2)O and Et(4)N(OAc).4H(2)O. The X-ray structures of I (M = Mn, Fe, Co) have been determined and show the metal ions asymmetrically bridged by two acetate ligands and a water molecule. One of the metal ions is bound by a pyridine ligand and two monodentate acetate ligands that are hydrogen bonded to the bridging water molecule. The second metal ion is bound to a bidentate acetate ligand and a pyridine ligand. Recrystallization of I from acetonitrile leads to the reorganization of I and isolation of the M(3)(OAc)(8)(Et(4)N)(2) complexes, II (M = Mn, Fe, Co). The X-ray structure of II (M = Mn, Co) has been determined and shows the three metal ions connected by four bridging acetate ligands in a &mgr;(1), &mgr;(2) mode and two acetate ligands in the &mgr;(1),eta(1) mode, with a bidentate acetate ligand on each of the external metal ions completing the distorted octahedral geometry. Air oxidation of I-Fe in propionitrile leads to the formation of the mixed-valence [Fe(3)&mgr;(3)-(O)(OAc)(7)(OH(2))]Et(4)N(III). The X-ray structure of III has been determined and resembles the core of the basic acetate complexes; however, it has five bridging acetate ligands. The Mössbauer spectrum of III shows two quadrupole doublets in a 1:2 ratio with delta(Fe) = 1.29(1) and 0.48 mm/s; DeltaE(q) = 1.89 and 0.71 mm/s. The oxidation of I-Fe by H(2)O(2)/O(2) in pyridine solution in the presence of Cl(-) ligands affords Fe(4)&mgr;(3)-(O)(2)(OAc)(6)(py)(4)Cl(2) (IV). The X-ray structure of IV shows a rhombic {Fe(III)(4)(&mgr;(3)-O)(2)} core previously found in iron and manganese chemistry. The reaction of ferrocenium ion with I-Fe under basic conditions in dichloromethane solution led to the formation of the familiar mixed-valence Fe(3)&mgr;(3)-(O)(OAc)(6)(py)(3) complex (V) with the basic acetate structure. Complexes I-Fe, II-Fe, III, and IV catalyze the reaction of O(2) with adamantane under GiF conditions to give adamantanols and adamantanone. The similarity of the results in comparison to similar studies previously reported for iron/carboxylate complexes are noted and discussed.
二聚体[M₂(OAc)₅(py)₂&μ-(OH₂)]Et₄N配合物I（M = Mn、Fe、Co）是从M(II)(OAc)₂·xH₂O和Et₄N(OAc)·4H₂O的吡啶溶液中分离得到的。已测定了I（M = Mn、Fe、Co）的X射线结构，结果表明金属离子由两个乙酸根配体和一个水分子不对称桥连。其中一个金属离子与一个吡啶配体和两个单齿乙酸根配体结合，这两个单齿乙酸根配体与桥连水分子形成氢键。第二个金属离子与一个双齿乙酸根配体和一个吡啶配体结合。I从乙腈中重结晶会导致I发生重组，并分离得到M₃(OAc)₈(Et₄N)₂配合物II（M = Mn、Fe、Co）。已测定了II（M = Mn、Co）的X射线结构，结果表明三个金属离子通过四个以&μ(1)、&μ(2)模式桥连的乙酸根配体和两个以&μ(1)、η(1)模式的乙酸根配体相连，每个外部金属离子上的一个双齿乙酸根配体完善了扭曲的八面体几何构型。I-Fe在丙腈中被空气氧化会生成混合价态的[Fe₃&μ₃-(O)(OAc)₇(OH₂)]Et₄N(III)。已测定了III的X射线结构，其类似于碱性乙酸盐配合物的核心结构；然而，它有五个桥连乙酸根配体。III的穆斯堡尔谱显示出两个四重峰双峰，比例为1:2，δ(Fe) = 1.29(1)和0.48 mm/s；ΔE(q) = 1.89和0.71 mm/s。在Cl⁻配体存在下，I-Fe在吡啶溶液中被H₂O₂/O₂氧化得到Fe₄&μ₃-(O)₂(OAc)₆(py)₄Cl₂（IV）。IV的X射线结构显示出一个菱形的{Fe(III)₄(&μ₃-O)₂}核心，这在铁和锰的化学中曾被发现。在二氯甲烷溶液中，在碱性条件下二茂铁离子与I-Fe反应生成了具有碱性乙酸盐结构的常见混合价态Fe₃&μ₃-(O)(OAc)₆(py)₃配合物（V）。配合物I-Fe、II-Fe、III和IV在GiF条件下催化O₂与金刚烷的反应，生成金刚烷醇和金刚烷酮。文中指出并讨论了与先前报道的铁/羧酸盐配合物类似研究结果的相似性。
