Reactivity and Structural and Physical Studies of Tetranuclear Iron(III) Clusters Containing the [Fe₄(μ₃-O)₂]⁸⁺ “Butterfly” Core:  an Fe^III₄ Cluster with an S = 1 Ground State

Abstract

The initial use of di-2-pyridyl ketone oxime [(py)2CNOH] in iron(III) carboxylate chemistry has yielded the tetranuclear complex [Fe4O2Cl2(O2CMe)2{(py)2CNO}4] (1). Compound 1 can be synthesized either by the 1:2:1 molar ratio reaction between Fe(III), MeCO2-, and (py)2CNOH (complex 1a) or by the 1:3 molar ratio reaction between [Fe3O(O2CMe)6(H2O)3]Cl and (py)2CNOH (complex 1b). The presence of N3- in both reaction mixtures has afforded the tetranuclear complex [Fe4O2(N3)2(O2CMe)2{(py)2CNO}4] (2), which can be alternatively synthesized by the reaction of 1 with N3-. Compound 1a crystallizes in the tetragonal space group /-4 with (at 25 degrees C) a = 35.06(2) A, b = 35.06(2) A, c = 13.255(6) A, V = 16293(2) A(3), and Z = 8. Compound 1b crystallizes in the monoclinic space group P2(1)/c with (at 25 degrees C) a = 22.577(7) A, b = 17.078(6) A, c = 17.394(6) A, beta = 93.50(1) degrees , V = 6694(4) A(3), and Z = 4. Compound 2 crystallizes in the triclinic space group P1 with (at 25 degrees C) a = 13.658(9) A, b = 15.815(9) A, c = 17.29(1) A, alpha = 97.08(3) degrees , beta = 98.55(3) degrees , gamma = 112.12(3) degrees , V = 3355(4) A(3), and Z = 2. The structures of 1 and 2 contain the [Fe4(mu3-O)2]8+ core comprising four Fe(III) ions in a "butterfly" disposition and two mu3-O2- ions, each bridging three Fe(III) ions forming the "wings" of the "butterfly". The Mössbauer spectra of 1b and 2 consist of composite quadrupole-split doublets, with parameters typical for high-spin Fe(III) in octahedral environments. Magnetic susceptibility measurements on 1a revealed antiferromagnetic interactions between the S = 5/2 ferric ions, with best-fit parameters being J(wb) = -40.2 cm(-1) and J(bb) = -59.4 cm(-1) (H = -2SigmaJiJj) for wingtip-body and body-body interactions, respectively, yielding an S = 1 ground state. Both wingtip-body and body-body interactions are well determined.

Iron(III)‐Pivalate‐Based Complexes with Tetranuclear {Fe4(μ3‐O)2}8+ Cores and N‐Donor Ligands: Formation of Cluster and Polymeric Architectures

“…This well-known tetranuclear core comprises an innermost planar or almost planar entity of two (so-called "body") Fe atoms doubly bridged by two μ 3 -oxo atoms, connected outwards to the remaining ("wings") Fe atoms. The iron butterfly complexes can be also considered to consist of two edge-sharing {Fe 3 [14][15][16] There are "bent," "planar," and "chairlike" types (Scheme 1). The latter is a hybrid of the first two forms and has been rarely observed.…”

“…The latter is a hybrid of the first two forms and has been rarely observed. [16] were described as chairlike, but their four Fe atoms have an almost planar arrangement [their average displacements from the ideal plane are ca. 0.02 and 0.01 Å, respectively].…”

“…[18] but also in ref. [16,[19][20][21][22][23] . We have summarized several characteristic data of these compounds in [22] and [L 2 Fe 4 (μ 3 -O) 2 (Ph 2 C(OH)CO 2 ) 3 (sao) 2 ] (ClO 4 ), [25] in which L = 1,4,7-trimethyl-1,4,7-triazacyclononane and H 2 sao = salicylaldoxime, are the exceptions from this family.…”

Fe2 and Fe4 Clusters Encapsulated in Vacant Polyoxotungstates: Hydrothermal Synthesis, Magnetic and Electrochemical Properties, and DFT Calculations

“…The tetranuclear Fe 4 complex encapsulated between the two POMs belongs to a well-known family of butterfly complexes. [27] The Fe2 À Fe2* fragment (Figure 2b) features the body of the butterfly, and the Fe2-Fe1-Fe2* and Fe2-Fe1*-Fe2* triangles schematize www.chemeurj.org the wings, with the Fe1 and Fe1* ions thus occupying the "wingtip" positions. The dihedral angle between the leastsquares planes defined by the Fe1/Fe2/Fe2* and Fe1*/Fe2/ Fe2* ions is 175.58, thus the four Fe III ions are essentially coplanar.…”

Hetero-heptanuclear (Fe–Na) complexes of salicylaldehydes: crystal and molecular structure of [Fe2(3-OCH3-salo)8 · Νa5] · 3OH · 8H2Ο

“…), which are related to their crystal structure. In the last decade iron polynuclear complexes possessing various metal cores have been prepared [23][24][25][26][27]. The organic part of all these complexes contains mainly multifunctional ligands with N and/or O donor atoms, which have versatility in binding the metal centers.…”