Tuning the Condensation Degree of {FeIIIn} Oxo Clusters via Ligand

Jun 8, 2018 - Tuning the Condensation Degree of {FeIIIn} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents ... solvothermal conditions aff...
0 downloads 0 Views 4MB Size
Download PDF
Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

pubs.acs.org/IC

Tuning the Condensation Degree of {FeIIIn} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents Olga Botezat,†,‡ Jan van Leusen,‡ Paul Kögerler,‡ and Svetlana G. Baca*,† †

Institute of Applied Physics, Academiei 5, MD2028 Chisinau, Moldova Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany

‡

S Supporting Information *

ABSTRACT: Trinuclear μ3-oxo-centered iron(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron(III) oxo-hydroxo condensation products, isolated as (mdeaH 3 ) 2 [Fe 6 O(thme) 4 Cl 6 ]·0.5(MeCN)·0.5(H 2 O) (1), [Fe 12 O 4 (OH) 2 (teda) 4 (N 3 ) 4 (MeO) 4 ]N 3 (NO 3 ) 0.5 (MeO) 0.5 · 2.5(H 2 O) (2), [Fe 1 2 O 6 (teda) 4 Cl 8 ]·6(CHCl 3 ) (3), [Fe 22 O 16 (OH) 2 (O 2 CCHMe 2 ) 18 (bdea) 6 (EtO) 2 (H 2 O) 2 ]·2(EtOH)·5(MeCN)·6(H2O) (4), and [Fe 22 O 14 (OH) 4 (O 2 CCHMe 2 ) 18 (mdea) 6 (EtO) 2 (H 2 O) 2 ](NO3)2·EtOH·H2O (5), where tedaH4 = N,N,N′,N′-tetrakis(2hydroxyethyl)ethylenediamine; thmeH 3 = 1,1,1-tris(hydroxymethyl)ethane; mdeaH2 = N-methyldiethanolamine; and bdeaH2 = N-butyldiethanolamine. Complete carboxylate metathesis in the {Fe3} precursor complexes by thme3− or teda4− and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe6} product (1) in MeCN/CH2Cl2 or {Fe12} complexes (2 and 3) in MeOH/EtOH and CHCl3/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that 1 contains a [Fe6O(thme)4Cl6]2− cluster anion with a Lindqvist-type {Fe6(μ6-O)} core motif, charge-compensated by two protonated mdeaH3+ cations. 2 comprises a [Fe12O4(OH)2(teda)4(N3)4(MeO)4]2+ cation with a {Fe12O4(OH)2}26+ core, whereas 3 contains a charge-neutral [Fe12O6(teda)4(Cl)8] complex with an {Fe12O6}24+ core. Finally, employing flexible bdeaH2 or mdeaH2 ligands under soft reaction conditions afforded giant {Fe22} oxo-hydroxo complexes (4 and 5) with a central {Fe6} layer sandwiched between two outer {Fe8} groups. Magnetic studies of 1−5 revealed strong antiferromagnetic coupling between the FeIII spin centers in all clusters.

■

INTRODUCTION High-nuclearity FeIII compounds continue to attract significant interest due to their role as model structures for diverse natural processes, including understanding the formation and growth of the core of ferritin family proteins, involved in iron storage and mineralization in most living organisms.1 Additionally, high-nuclearity FeIII compounds can possess large ground-state spin values and show unusual magnetic properties such as a single-molecule magnet (SMM) characteristics or molecular spin frustration.2,3 Thus, the development of new synthetic strategies toward high-nuclearity iron species remains an attractive target, to which significant efforts have been devoted. In this context the use of predesigned metal-containing precursors as starting materials and source of the metal component in combination with flexible organic linkers containing alkoxide groups recommends itself as a very promising approach to polynuclear clusters. The well-known “basic carboxylate”, that is, μ3-oxo-centered trinuclear Fe(III) carboxylate clusters [Fe3O(O2CR)6(L)3]+ (L: neutral terminal ligand), represents a family of precursors with several advantages: First, they display synthetic convenience; specifi© XXXX American Chemical Society

cally, their terminal ligands (L) are frequently labile, providing an opportunity to assemble these trinuclear clusters into larger species through replacing L with selected bridging and chelating moieties. Moreover, their carboxylate ligands can be also partially or completely substituted to induce rearrangements that bridge the metal centers. Concerning the secondary organic ligands employed for the design of high-nuclearity complexes, flexible polyalcohol ligands have successfully been explored, resulting in numerous reported polynuclear transition-metal clusters.4 We previously employed polyalcoholamine ligands in the preparation of homometallic {Fe8}5 and heterometallic {Fe4Ln2}6,7 and {Fe18Ln6}7 polynuclear clusters, of which the smaller {Fe4Ln2} (Ln = Tb, Ho) and the currently largest {Fe18Ln6} (Ln = Dy, Tb) wheel-shaped clusters exhibit SMM properties. As an extension of our previous work on the synthesis of oxo-hydroxo-bridged polynuclear FeIII containing clusters, herein we employed 1,1,1-tris(hydroxymethyl)ethane (thmeH3), N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine Received: April 12, 2018

A

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

that were used as received without further purification. The precursor compound [FeIII3O(O2CCHMe2)6(H2O)3]NO3·2(MeCN)·2(H2O) was prepared using a published procedure.5 Caution! Care should be taken when using the potentially explosive sodium azide. IR spectra were recorded in the solid state (KBr pellets) on a PerkinElmer Spectrum One spectrometer in the 400−4000 cm−1 range. Thermogravimetric analysis (TGA)/differential thermal analysis (DTA) measurements were performed with a Mettler Toledo TGA/ SDTA 851 in dry N2 flux (60 mL min−1) at a heating rate of 10 K min−1 from 25 to 800 °C (1−3) or 1000 °C (4) (Supporting Information, Figures S6−S9). A Bandelin Sonorex RK-100H ultrasonic bath operating at 35 kHz with a maximum power output of 160 W was used for the ultrasonic irradiation. X-ray Crystallography. Diffraction data sets for 1−5 were collected at 100(2) K on a Bruker diffractometer with APEX II CCD detector using graphite-monochromatized Mo Kα radiation. The structures were solved by the direct methods and refined by full-matrix least-squares on weighted F2 values for all reflections using SHELX suite of programs.8 All non-H atoms in clusters were refined with anisotropic displacement parameters. H atoms were placed in fixed, idealized positions and refined as rigidly bonded to the corresponding atom. Some H atoms of solvent molecules (H2O, MeCN, and MeOH) and coordinated H2O and hydroxo groups could not be located in 1− 5. In 1, ethanol groups of solvate N-methyldiethanolamine were found to be disordered over two positions. In 3, solvate chloroform molecules also were revealed as disordered. Some methyl groups of isobutyrate in 4 and 5 were found to be disordered. Therefore, SIMU, DELU, SADI, ISOR, and DFIX restraints were used to deal with the disordered moieties in the structures and to obtain reasonable geometrical parameters and thermal displacement coefficients. Badly disordered solvent molecules (in 4 and 5) and counteranions (in 5) were removed by the SQUEEZE routine. Crystallographic data and structure refinements of 1−5 are summarized in Table S1, and selected bond distances are given in Table 1. The packing diagrams of 1−5 are presented in Supporting Information (Figures S1−S5). Magnetic Measurements. Magnetic susceptibility data for 1−5 were obtained using a Quantum Design MPMS-5XL SQUID magnetometer. The polycrystalline samples were compacted and immobilized into cylindrical poly(tetrafluoroethylene) (PTFE) capsules. The data were acquired as a function of field and temperature. All data were corrected for diamagnetic contributions from the sample holder and the compounds. Synthesis of (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1). A mixture of [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(MeCN)·2(H2O)

(tedaH4), N-buthyldiethanolamine (bdeaH2), and N-methyldiethanolamine (mdeaH2; Scheme 1) as binding ligands in the Scheme 1. Organic Ligands Used in the Syntheses of 1−5

combination with a trinuclear FeIII isobutyrate cluster under one-pot synthesis conditions at temperatures ranging from room temperature to solvothermal heating in different media to prepare larger FeIII clusters ranging in nuclearity from 6 to 22 (Scheme 2). These are isolated as the carboxylate-free hexanuclear compound (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1), the carboxylate-free dodecanuclear cluster compounds [Fe12O4(OH)2(teda)4(N3)4(MeO)4]N3(NO3)0.5(MeO)0.5·2.5(H2O) (2) and [Fe12O6(teda)4Cl8]·6(CHCl3) (3), and the carboxylate-containing doicosanuclear cluster compounds [Fe 2 2 O 1 6 (OH) 2 (O 2 CCHMe 2 ) 1 8 (bdea)6(EtO)2(H2O)2]·2(EtOH)·5(MeCN)·6(H2O) (4) and [Fe 22 O 14 (OH) 4 (O 2 CCHMe 2 ) 18 (mdea) 6 (EtO) 2 (H 2 O) 2 ](NO3)2·EtOH·H2O (5). We note that, although the nuclearity of the final product is usually difficult to predict, the nature of bridging polytopic ligands, sources of metal ions, and reaction temperature are all crucial synthesis parameters. We herein discuss the synthesis, structure, and magnetism of 1−5.

■

EXPERIMENTAL SECTION

Materials and General Procedures. All reactions were performed under aerobic conditions using chemicals and solvents

Scheme 2. Synthesis of 1−5

B

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Table 1. Selected Bond Distances (Å) for 1−5 1 Fe1−O7#1 Fe1−O3 Fe1−O2 Fe1−O5 Fe1−O1 Fe1−Cl1 Fe2−O4#1 Fe2−O4 symmetry transformations

1.978(7) Fe2−O3 1.991(8) 1.989(8) Fe2−O3#1 1.991(8) 1.990(8) Fe2−O1 2.250(11) 1.991(8) Fe2−Cl2 2.279(5) 2.254(2) Fe3−O6#1 1.985(7) 2.282(3) Fe3−O6 1.985(7) 1.985(7) Fe3−O5#1 1.995(8) 1.985(7) Fe3−O5 1.995(8) used to generate equivalent atoms: #1 x + 0, −y +3/2, −z + 9/4 2 Fe5−O24 Fe5−N15 Fe5−O17 Fe5−O12 Fe5−O3 Fe5−O15 Fe6−O17 Fe6−O16 Fe6−O4 Fe6−O18 Fe6−N6 Fe6−O15 Fe6−N5 Fe7−O6 Fe7−O22 Fe7−O2 Fe7−O1 Fe7−O25 Fe7−O9 Fe8−O13 Fe8−O25 Fe8−O8 Fe8−N12 Fe8−O2 Fe8−O11

Fe3−O1 Fe3−Cl3 Fe4−O7 Fe4−O2 Fe4−O4#1 Fe4−O6#1 Fe4−O1 Fe4−Cl4

2.264(11) 2.266(5) 1.983(8) 1.990(8) 1.996(7) 2.005(8) 2.223(1) 2.292(3)

1.948(16) 1.97(2) 2.018(16) 2.046(16) 2.049(16) 2.094(15) 1.960(15) 1.996(18) 2.061(15) 2.086(15) 2.25(2) 2.282(16) 2.31(2) 1.953(15) 1.955(14) 1.980(14) 2.013(15) 2.035(15) 2.123(15) 1.990(15) 2.008(16) 2.044(15) 2.05(2) 2.054(16) 2.111(17)

Fe9−O12 Fe9−O13 Fe9−O3 Fe9−O14 Fe9−O11 Fe9−N3 Fe9−N4 Fe10−O14 Fe10−O4 Fe10−O6 Fe10−O3 Fe10−O26 Fe10−O15 Fe11−O21 Fe11−O26 Fe11−N18 Fe11−O16 Fe11−O4 Fe11−O19 Fe12−O21 Fe12−O20 Fe12−O1 Fe12−O22 Fe12−O19 Fe12−N7 Fe12−N8

1.922(17) 1.937(16) 2.024(16) 2.107(15) 2.261(16) 2.280(19) 2.30(2) 1.961(15) 1.964(16) 1.982(15) 1.993(16) 2.020(15) 2.171(17) 2.016(16) 2.025(16) 2.040(19) 2.049(19) 2.055(14) 2.087(15) 1.935(15) 1.963(17) 2.049(14) 2.081(15) 2.272(15) 2.277(19) 2.304(18)

Fe1−O1 Fe1−O4 Fe1−O18 Fe1−O5 Fe1−O23 Fe1−O19 Fe2−O23 Fe2−N9 Fe2−O10 Fe2−O1 Fe2−O20 Fe2−O9 Fe3−O10 Fe3−O8 Fe3−O2 Fe3−O7 Fe3−O9 Fe3−N1 Fe3−N2 Fe4−O5 Fe4−O2 Fe4−O3 Fe4−O7 Fe4−O24 Fe4−O11

1.913(15) 1.947(15) 1.962(15) 1.969(15) 2.049(15) 2.142(14) 2.000(15) 2.007(19) 2.016(16) 2.062(14) 2.088(16) 2.119(14) 1.951(16) 1.977(15) 2.049(14) 2.085(15) 2.234(14) 2.278(19) 2.319(18) 1.932(15) 1.945(14) 1.953(15) 1.965(15) 2.029(16) 2.110(16)

Fe1−O9 Fe1−O3 Fe1−O2 Fe1−O1 Fe1−O6 Fe1−Cl1 Fe2−O10#1 Fe2−O5 Fe2−O2 Fe2−O12#1 Fe2−Cl3 Fe2−Cl1

1.937(6) 1.941(6) 1.960(6) 1.984(4) 2.062(7) 2.566(3) 1.983(7) 2.004(7) 2.017(6) 2.073(7) 2.337(3) 2.459(3)

Fe3−O8 Fe3−O5 Fe3−O7 Fe3−O2 Fe3−O6 Fe3−N2 Fe3−N1 Fe4−O8 Fe4−O11 Fe4−O26 Fe4−O6 Fe4−Cl4 Fe4−Cl2 symmetry transformations used to generate equivalent atoms: #1 −x, y, −z + 1/2 4

1.936(6) 2.000(7) 2.084(7) 2.107(7) 2.151(7) 2.305(8) 2.309(9) 2.010(7) 2.057(7) 2.096(6) 2.289(7) 2.432(3) 2.603(3)

Fe5−O3 Fe5−O7#1 Fe5−O4 Fe5−O2#1 Fe5−O12 Fe5−Cl2 Fe6−O11 Fe6−O10 Fe6−O3 Fe6−O9 Fe6−N3 Fe6−O12 Fe6−N4

1.908(7) 1.958(7) 1.980(4) 1.986(7) 2.151(6) 2.444(3) 1.957(7) 1.964(7) 2.038(6) 2.083(6) 2.272(8) 2.304(7) 2.348(8)

Fe1−O1 Fe1−O6 Fe1−O8 Fe1−O23 Fe1−O33 Fe2−O2 Fe2−O9 Fe2−O34

1.835(5) 1.957(5) 1.961(6) 2.016(6) 2.090(5) 1.908(5) 2.016(6) 2.024(6)

2.097(6) 1.909(6) 1.923(5) 1.929(5) 2.093(5) 2.141(5) 2.141(5) 1.933(5)

Fe8−O31 Fe8−O4 Fe8−O5 Fe8−O35 Fe9−O35 Fe9−O29 Fe9−O30 Fe9−O25

1.924(6) 2.077(5) 2.077(5) 2.087(6) 1.916(6) 1.991(6) 1.999(6) 2.028(7)

3

Fe4−O26 Fe5−O2 Fe5−O3 Fe5−O1 Fe5−O5 Fe5−O35 Fe5−O4 Fe6−O4 C

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Table 1. continued 4 Fe2−O7 Fe2−O8 Fe2−O6 Fe3−O3 Fe3−O34#1 Fe3−O6 Fe3−O6#1 Fe3−O11 Fe3−O7 Fe4−O2 Fe4−O35 Fe4−O27 Fe4−O10 Fe4−O17

2.039(5) Fe6−O28 1.970(6) 2.053(5) Fe6−O27 1.999(6) 2.082(6) Fe6−O14 2.010(6) 1.847(5) Fe6−O16 2.015(6) 1.957(6) Fe4−O3 2.191(7) 1.968(5) Fe6−N1 2.244(7) 2.011(5) Fe7−O3 1.912(5) 2.113(5) Fe7−O4 1.956(5) 2.117(6) Fe7−O32 1.991(6) 1.903(5) Fe7−O15 2.042(6) 1.982(6) Fe7−O12 2.047(6) 1.990(6) Fe7−O13 2.117(6) 2.024(6) Fe8−O30 1.910(6) 2.069(6) Fe8−O28 1.919(6) symmetry transformations used to generate equivalent atoms: #1 −x + 1, −y + 5

Fe1−O6 1.867(7) Fe1−O4 1.936(7) Fe1−O8 1.984(7) Fe1−O10 2.006(8) Fe1−O35 2.115(7) Fe2−O5 1.888(7) Fe2−O34#1 1.982(7) Fe2−O4 2.003(7) Fe2−O4#1 2.018(7) Fe2−O12 2.090(8) Fe2−O9 2.131(7) Fe3−O7 1.914(7) Fe3−O34 2.017(7) Fe3−O14 2.025(8) Fe3−O9 2.040(7) Fe3−O8 2.042(8) Fe3−O4 2.088(7) Fe4−O5 1.907(7) Fe4−O6 1.918(7) Fe4−O7 1.918(7) Fe4−O3 2.084(7) Fe4−O1 2.129(8) symmetry transformations used to generate equivalent

Fe4−O2 Fe5−O6 Fe5−O3 Fe5−O31 Fe5−O18 Fe5−O11 Fe5−O16 Fe6−O5 Fe6−O29 Fe6−O1 Fe6−O20 Fe6−O13 Fe6−O22 Fe7−O7 Fe7−O2 Fe7−O32 Fe7−O15 Fe7−O24 Fe7−O26 Fe8−O30 Fe8−O28 Fe8−O33 atoms: #1 −x + 2, −y + 2,

2.143(7) 1.892(7) 1.991(7) 1.991(8) 2.028(8) 2.059(8) 2.117(8) 1.908(8) 1.989(8) 1.989(8) 2.054(8) 2.056(8) 2.147(9) 1.903(7) 1.973(7) 1.997(9) 2.033(7) 2.048(7) 2.112(8) 1.932(7) 1.933(7) 1.944(8) −z

Fe9−O18 Fe9−N2 Fe10−O5 Fe10−O31 Fe10−O32 Fe10−O22 Fe10−O20 Fe10−N3 Fe11−O1 Fe11−O29 Fe11−O5 Fe11−O19 Fe11−O24 Fe11−O21 1, −z + 1

2.048(7) 2.226(8) 1.916(5) 1.988(5) 1.989(5) 2.018(6) 2.049(6) 2.258(7) 1.907(6) 1.972(6) 2.002(5) 2.047(6) 2.056(6) 2.075(6)

Fe8−O1 Fe8−O2 Fe8−O3 Fe9−O3 Fe9−O17 Fe9−O28 Fe9−O29 Fe9−O19 Fe9−N1 Fe10−O1 Fe10−O33 Fe10−O32 Fe10−O23 Fe10−O21 Fe10−N3 Fe11−O2 Fe11−O30 Fe11−O31 Fe11−O27 Fe11−O25 Fe11−N2

2.075(7) 2.080(7) 2.110(8) 1.923(7) 1.984(8) 1.985(8) 2.029(8) 2.070(8) 2.233(10) 1.929(8) 1.989(8) 2.003(8) 2.022(8) 2.027(8) 2.214(10) 1.934(7) 1.985(8) 2.007(8) 2.013(8) 2.050(8) 2.200(10)

C44.50H100.50Fe12N23.50O30.50 (2123.18 g mol−1): C, 25.17; H, 4.77; N, 15.5. Found: C, 25.26; H, 4.87; N, 14.86%. IR data (KBr pellet, cm−1): 3395br, 2861s, 2068vs, 1637w, 1468w, 1384m, 1339sh, 1268w, 1096s, 1057s, 934m, 911sh, 740w, 660w, 613sh, 497m, 442sh. Synthesis of [Fe12O6(teda)4Cl8]·6(CHCl3) (3). A stirred solution of [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(MeCN)·2(H2O) (0.066 g, 0.07 mmol), N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (0.036 g, 0.15 mmol), and N-methyldiethanolamine (0.029 g, 0.24 mmol) in 4 mL of CHCl3 and 4 mL of tetrahydrofuran (thf) was placed in a Teflon-lined stainless steel container (12 mL) and heated at 120 °C for 4 h, followed by slow cooling to room temperature over 48 h. The obtained red-brown crystals of 3 suitable for X-ray analysis were filtered off, washed with CHCl3, and dried in vacuum. Yield: 0.019 g, 49% (based on Fe). Anal. Calcd for 3, C42H82Cl14Fe12N8O22 (without 4 CHCl3, 2217.62 g mol−1): C, 22.75; H, 3.73; N, 5.05. Found: C, 22.47; 22.36; H, 4.46; 4.64; N, 5.09; 5.08%. IR data (KBr pellet, cm−1): 2872s, 1631m, 1469m, 1361vw, 1316vw, 1269vw, 1089vs, 1055sh, 934s, 909m, 740w, 634s, 536sh, 492s. Synthesis of [Fe22O16(OH)2(O2CCHMe2)18(bdea)6(EtO)2(H2O)2]·2(EtOH)·5(MeCN)·6(H2O) (4). A mixture of [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(MeCN)·2(H2O) (0.084 g, 0.089 mmol), sodium dicyanamide (0.02 g, 0.22 mmol), and Nbutyldiethanolamine (0.081 g, 0.5 mmol) in 10 mL of EtOH was

(0.066 g, 0.07 mmol), 1,1,1-tris(hydroxymethyl)ethane (0.062 g, 0.52 mmol), and N-methyldiethanolamine (0.079 g, 0.66 mmol) in 4 mL of MeCN and 4 mL of CH2Cl2 was stirred for 5 min and placed in a Teflon-lined stainless steel container (12 mL) and heated at 120 °C for 4 h, then cooled to room temperature over 48 h. Red-brown crystals of 1 suitable for X-ray analysis were filtered off, washed with acetonitrile, and dried in air. Yield: 0.029 g, 65% (based on Fe). Anal. Calcd for 1, C31H68.50Cl6Fe6N2.50O17.50 (1304.18 g mol−1): C, 28.54; H, 5.29; N, 2.69. Found: C, 29.18; 29.38; H, 5.29; 5.22; N, 2.77; 2.71%. IR data (KBr pellet, cm−1): 3414br, 2954m, 2921m, 2862s, 1463w, 1398vw, 1119m, 1018vs, 619sh, 590m, 521vs, 474w. Synthesis of [Fe12O4(OH)2(teda)4(N3)4(MeO)4]N3(NO3)0.5(MeO)0.5· 2.5(H2O) (2). A stirred solution containing [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(MeCN)·2(H2O) (0.06 g, 0.064 mmol), N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (0.07 g, 0.3 mmol), NaN3 (0.013 g, 0.2 mmol), and N-methyldiethanolamine (0.07 g, 0.59 mmol) in 4 mL of MeOH and 4 mL of EtOH was placed in a Teflon-lined stainless steel container (12 mL) and heated at 120 °C for 4 h and then slowly cooled to 25 °C over 48 h. The dark-brown solution was filtrated and allowed to evaporate slowly at room temperature. Red-brown crystals of 2 suitable for X-ray analysis were filtered off after one week, washed with MeOH, and dried in vacuum. Yield: 0.006 g, 18% (based on Fe). Anal. Calcd for 2, D

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry put under ultrasonic treatment for 1 h and then filtered. The filtrate was kept in a closed vial at room temperature. Dark brown crystals of 4 suitable for X-ray analysis were filtered off after one month, washed with hexane, and dried in vacuum. Yield: 0.024 g, 44% (based on Fe). Anal. Calcd for 4, C138H285Fe22N11O78 (4575.45 g mol−1): C, 36.2; H, 6.23; N, 3.37. Found: C, 35.14; 35.14; H, 5.76; 5.75; N, 3.75; 3.72%. IR data (KBr pellet, cm−1): 3418br, 2963s, 2927sh, 2868sh, 2086vw, 1582vs, 1543vs, 1471m, 1427vs, 1364w, 1303w, 1169vw, 1096m, 1059sh, 1024sh, 905w, 838w, 759w, 725sh, 639sh, 584m, 520w, 464vw. Synthesis of [Fe22O14(OH)4(is)18(mdea)6(EtO)2(H2O)2](NO3)2·EtOH· H2O (5). The solution of [Fe3O(O2CCHMe2)6(H2O)3](NO3)· 2(MeCN)·2(H2O) (0.082 g, 0.087 mmol) and N-methyldiethanolamine (0.032 g, 0.27 mmol) in 12 mL of EtOH was stirred at room temperature for 3 h and 15 min and then filtered. The filtrate was kept in a closed vial at room temperature. Dark brown crystals suitable for X-ray analysis were filtered off after two months, washed with hexane, and dried in vacuum. Yield: 0.007 g, 15% (based on Fe). Anal. Calcd for C108H218Fe22N8O78 (4105.59 g mol−1): C, 31.60; H, 5.35; N, 2.73%. Found: C, 32.05; H, 5.81; N, 2.94%. IR data (KBr pellet, cm−1): 3417br, 2966s, 2924sh, 2869sh, 1582vs, 1549vs, 1471m, 1426vs, 1393s, 1302w, 1168vw, 1094m, 1055sh, 1026sh, 999w, 902w, 834vw, 761vw, 633sh, 585m, 533m.

[Fe 22 O 16 (OH) 2 (O 2 CCHMe 2 ) 18 (bdea) 6 (EtO) 2 (H 2 O) 2 ]·2(EtOH)·5(MeCN)·6(H2O) (4) in 29% yield. Changing the polytopic polyalcohol amine ligand, for example, from bdeaH2 to mdeaH2, and stirring the reaction solution at room temperature led to the precipitation of [Fe 22 O 14 (OH) 4 (O 2 CCHMe 2 ) 18 (mdea) 6 (EtO) 2 (H 2 O) 2 ](NO3)2·EtOH·H2O (5) in 9% yield. All bulk samples were further characterized by IR spectroscopy and TGA to confirm their identities (see Supporting Information for details). Structural Description. Structure of (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1). Single-crystal X-ray diffraction analysis revealed that compound 1 crystallizes in the tetragonal space group I4̅2d and consists of an anionic hexametalate [Fe6O(thme)4Cl6]2− cluster, two outer-sphere protonated mdeaH3+ moieties, and crystal solvent molecules. In the anionic cluster with C2 molecular symmetry a central μ6-oxo atom resides on twofold axis and is surrounded by six FeIII centers to form an octahedron, akin to the central motif of the Lindqvist structure archetype in polyoxometalate chemistry (Figure 1). Twelve alkoxo groups of four (triply deprotonated)

■

RESULTS AND DISCUSSION Synthetic Aspects. A simple approach for preparing the carboxylate-free hexanuclear (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1), dodecanuclear [Fe 12 O 4 (OH) 2 (teda) 4 (N 3 ) 4 (MeO) 4 ]N 3 (NO 3 ) 0.5 (MeO) 0.5 · 0.5(H2O) (2), and [Fe12O6(teda)4Cl8]·6(CHCl3) (3) complex compounds were developed around a one-pot solvothermal reaction using the small trinuclear [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(MeCN)·2(H2O) carboxylate species (Scheme 1). The interaction of the μ3-oxo trinuclear FeIII isobutyrate precursor with 1,1,1-tris(hydroxymethyl)ethane (thmeH3) and N-methyldiethanolamine (mdeaH2) in a 1:1 (v/v) MeCN/CH2CH2 mixture under solvothermal conditions afforded red-brown crystals of the hexanuclear cluster (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1) in a moderate yield of 45%. In case of the dodecanuclear clusters isolated as [Fe12O4(OH)2(teda)4(N3) 4(MeO) 4]N3(NO3)0.5(MeO)0.5·2.5(H2O) (2) and [Fe12O6(teda)4Cl8]· 6(CHCl3) (3), the reactions were performed using the same Fe III precursor and N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (tedaH4) with (2) or without (3) sodium azide in a solvent mixture (MeOH/EtOH (2) and CHCl3/thf (3)) in the presence of N-methyldiethanolamine under otherwise identical solvothermal conditions. The red-brown crystals of 2 were isolated from the filtrate in one week, whereas crystals of 3 were filtered from the Teflon-lined stainless steel reactor after finishing the solvothermal process. Similar to 1, in these compounds isobutyrate moieties are also completely replaced by the hexadentate polyalcohol ligand, solvent molecules, and azide or Cl− anions. Another important observation is that the solvothermal heating of starting materials in MeCN/CH2Cl2 or CHCl3/thf solution induces dehalogenation of dichloromethane or chloroform, yielding chloride ions in 1 and 3, respectively. The negative or positive charge of the core in 1 and 3 is compensated by mdeaH3+ in 1 and by NO3− and N3− in 2. Although N-methyldiethanolamine is not incorporated in the crystal structures of 2 and 3, its presence is crucial for the formation of these compounds. Ultrasonic treatment of ethanol solutions containing [Fe3O(O2CCHMe2)6(H2O)3](NO3)·2(H2O)·2(MeCN), sodium dicyanamide, and N-butyldiethanolamine produced

Figure 1. (a) Structure of [Fe6(μ6-O)(thme)4Cl6]2− cluster and (b) schematic view of a smaller Fe6 octahedron (orange faces) within a larger Cl6 octahedron (purple edges). Color scheme: Fe, green; Cl, purple; μ6-O, red spheres; C, gray; O, red; H, white sticks.

thme3− ligands additionally bridge the FeIII atoms: each of the thme3− ligands coordinates in a η2:η2:η2-μ3 mode with each oxygen bridging two metal sites. The remaining coordination site at each FeIII center is occupied by a Cl− ligand. Thus, the core of 1 can also be approximated as assembly of a smaller Fe6 octahedron within a larger Cl6 octahedron (Figure 1b). All FeIII atoms in 1 are six-coordinated and adopt an elongated octahedral O5Cl environment by a terminal chloride and five oxygen atoms: one central μ6-O atom and four O atoms from two neighboring thme3− ligands (Fe−(μ6-O): 2.223(1)− 2.264(11), other Fe−O: 1.978(7)−2.005(8), Fe−Cl: 2.266(5)−2.292(3) Å; Table 1). The similar octahedral {Fe6(μ6-O)} unit with a central μ6-oxo group was previously found in other hexanuclear FeIII complexes,9 where the role of cations play sodium, hydroxonium, tetramethylamonium, or pyridinium, as well as in several higher nuclearity complexes such as hepta-,10 dodeca-,1b and nonadecanuclear11 iron aggregates. Structure of [Fe 1 2 O 4 (OH) 2 (teda) 4 (N 3 ) 4 (MeO) 4 ]N3(NO3)0.5(MeO)0.5·2.5(H2O) (2) and [Fe12O6(teda)4(Cl)8]·6(CHCl3) (3). Compound 2 crystallizes in the tetragonal space group P4, whereas compound 3 crystallizes in the monoclinic space group C2/c. In both compounds, the coordination complexes have a saddlelike non-coplanar Fe12 ring arrangement (Figures 2a and 3a). The structure of 2 consists of a [Fe12O4(OH)2(teda)4(N3)4(MeO)4]2+ cation, charge-balanced E

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

planes) that are bridged by four μ4-O2− ions, two hydroxo μ2− OH− groups, and four teda4− ligands, whereas four N3− and four methoxy MeO− groups complete the FeIII coordination spheres. Two N atoms of teda4− coordinate to the metal atoms, and each of the O atoms of four hydroxy groups bridges neighboring Fe sites. Each teda4− ligand is coordinates in a η2:η2:η2:η2:η1:η1-μ6 bridging mode. Eight FeIII centers (Fe1, Fe2, Fe4, Fe5, Fe7, Fe8, Fe10, and Fe11) are hexa-coordinated; four of them have an O6 donor set (two O of two teda4− ligands, two μ4-O2−, one μ2-MeO−, one μ2−OH−), and the other four are in an O5N environment (three O of two teda4− ligands, one MeO−, one μ4-O2−, one azide N), with Fe−O: 1.913(15)−2.171(17), Fe−N: 1.97(2)−2.05(2) Å. The remaining four Fe sites (Fe3, Fe6, Fe9, and Fe12) are heptacoordinated with distorted pentagonal bipyramidal N2O5 environments from two N and four O atoms of teda4− ligand, and one μ4-O2− (Fe−O: 1.922(17)−2.272(15), Fe−N: 2.25(2)−2.319(18) Å). The outer azide anions in 2 form O− H···N hydrogen bonds (2.75(4) and 2.73(4) Å) with hydroxo groups of neighboring [Fe12O4(OH)2(teda)4(N3)4(OMe)4]2+ clusters to generate a cationic hydrogen-bonded {Fe12} clusterbased chain as shown in Figure 2b. To our knowledge, thus far only very few saddlelike dodecanuclear FeIII clusters have been reported.12,13 The core of cluster 3 is essentially the same as that in 2 and has the same saddlelike shape with two planar Fe6 layers (Figure 3b). Twelve FeIII atoms linked via four μ4-O2− ions and four teda4− ligands, except that hydroxo and methoxy groups are replaced by μ2-O2− and μ2-Cl− ligands, respectively, resulting in a [Fe12O6(teda)4Cl4]4+ unit with a {Fe12O6}24+ core. The coordination of four monodentate chlorides to FeIII atoms completes the structure of 3. Note that the asymmetric unit of 3 consists of six Fe ions, two teda4− ligands, four chlorides, three oxo-groups, and three solvent chloroform. Four

Figure 2. Structure of the {Fe12} cluster (a) and a hydrogen-bonded chain (b) in 2. N atoms of bridging azide and O atoms of OH groups emphasized as blue and red balls. Color scheme: Fe, green spheres; N, blue; O, red, C, gray sticks. Hydrogen bonds are shown as blue dotted lines.

Figure 3. Top (a) and side (b) views of the structure [Fe12O6(teda)4(Cl)8] cluster in 3. Color scheme: Fe, green; Cl, purple spheres; N, blue; O, red, C, gray sticks. Hydrogen atoms are omitted for clarity.

by NO3−, MeO−, and N3− anions, and 2.5 solvent water molecules per formula unit. 3 consists of charge-neutral [Fe12O6(teda)4Cl8] clusters and solvent chloroform molecules. The core structure of 2 can be considered as the arrangement of two nearly planar Fe6 layers (deviation 0.20° between

Figure 4. (a) The structure of the [Fe22O16(OH)2(O2CCHMe2)18(bdea)6(EtO)2(H2O)2] cluster. (b) Structure of the outer {Fe8} layers (top view); (c) the central {Fe6} subunit (pentacoordinated Fe sites: olive spheres) within complex 4. Color scheme: Fe, green; μ4-O, red spheres; N, blue; O, red, C, gray sticks. Hydrogen atoms are omitted for clarity. F

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry FeIII centers are hexa-coordinated, with Fe2 and Fe4 in an O4Cl2 coordination environment (three O of teda4−, one μ4O2−) and Fe1 and Fe5 in an O5Cl environment (two O from two teda4−, two μ4-O2−, one μ2-O2−); Fe−O: 1.937(6)− 2.289(7), Fe−Cl: 2.337(3)−2.603(3) Å. Fe3 and Fe6 are hepta-coordinated with a distorted pentagonal bipyramidal N2O5 environment (two N and four O of teda4−, one μ4-O2−; Fe−O: 1.936(6)−2.304(7), Fe−N: 2.272(8)−2.348(8) Å). Structure of [Fe 2 2 O 1 6 (OH) 2 (O 2 CCHMe 2 ) 1 8 (bdea) 6 (EtO)2(H2O)2]·2(EtOH)·5(MeCN)·6(H2O) (4) and [Fe 22 O 14 (OH) 4 (O 2 CCHMe 2 ) 18 (mdea) 6 (EtO) 2 (H 2 O) 2 ](NO 3 ) 2 · EtOH·H2O (5). Compounds 4 and 5 crystallize in the triclinic space group P1.̅ The structures of 4 and 5 consist of 22 Fe centers (with 11 crystallographically independent sites) that form a {Fe22(μ4-O)8(μ3-O)6(μ2-O)2(μ2-OH)2(μ2-EtO)2} core in 4, and a {Fe22(μ4-O)8(μ3-O)6(μ2-OH)4(μ2-EtO)2} core in 5. Additional bridges between FeIII atoms are provided by 18 isobutyrate and six bdea2− (4) or mdea2− (5) ligands that are situated at the periphery of the molecules. A terminal H2O ligand completes the coordination sphere of two Fe atoms. The {Fe22} core in 4 and 5 can be formally constructed from three layers of two types. The upper and bottom {Fe8} layers consist of eight FeIII atoms interlinked by three μ4-O atoms to form three edge-sharing [Fe4(μ4-O)] tetrahedra, with shortest Fe−Fe distances of 2.834(2) Å in 4 and 2.849(2) Å in 5, resembling a propeller with three tilted blades (Figure 4b). Each {Fe8} layer is connected to the central {Fe6} layer via three μ3-O and three isobutyrate bridges. The central {Fe6} layer itself comprises two μ4-O, two μ2-EtO groups, and μ2-O or μ2-OH bridges. Four Fe atoms form a central [Fe4(μ4O)2(μ2-O)2(μ2-EtO)2]2+ fragment, to which two additional Fe atoms are attached as shown in Figure 4c. These two Fe atoms are pentacoordinated with an O5 donor set, whereas all other Fe atoms have distorted NO5 or O6 octahedral environments (Fe−O: 1.838(5)−2.143(5), Fe−N: 2.200(10)−2.258(8) Å, consistent with those of the above-mentioned clusters and the reported Fe22 species).4e It is noteworthy that there are strong intracluster hydrogen bonds between the coordinated water molecules (O33 (4), O35 (5)) and one oxygen atom from the bridging isobutyrates (O7 [−x + 1, −y + 1, −z + 1], O21:2.570(7) and 2.806(8) Å (4); O9 [−x + 2, −y + 2, −z], O16:2.562(9) and 2.896(9) Å (5)). Further, hydroxo groups are hydrogen bonded to one of the carboxylate oxygen (O8···O26:2.805(8) (4), 2.793(1) Å (5)). Magnetochemistry. The magnetic data of (mdeaH3)2[Fe6O(thme)4Cl6]·0.5(MeCN)·0.5(H2O) (1) are presented as χmT versus T and Mm versus B curves in Figure 5. At 290 K, the value of χmT is 11.13 cm3 K mol−1 at 0.1 T, which is well-below the spin-only value of six noncoupled highspin FeIII centers (26.26 cm3 K mol−1, Seff = 5/2, giso = 2). Decreasing temperature, the χmT values continuously decrease to 0.07 cm3 K mol−1 at 2.0 K. At this temperature, the molar magnetization is an almost linear function of the applied magnetic field, reaching 0.2 NA μB at 5.0 T. These observations are in line with dominant antiferromagnetic exchange interactions between the six FeIII centers and with minor paramagnetic impurities. The presence of the latter can be derived from the very small but non-negligible values of the molar magnetization (0.1 NA μB < Mm ≪ 2.0 NA μB at 5.0 T) taking into account the saturation value of a single FeIII center Mm,sat = 5.0 NA μB. Additionally, since saturation steps may occur at 0, 2, 4, ..., and 30 NA μB for six interacting Seff = 5/2

Figure 5. Temperature dependence of the product χmT at 0.1 T and molar magnetization Mm vs applied magnetic field B at 2.0 K (inset) of 1.

centers, we conclude that the molecular ground state of 1 is characterized by a total effective spin of Stot = 0. The magnetic properties of the {Fe12} compounds 2 and 3 are analyzed on the basis of the χmT versus T and Mm versus B plots shown in Figure 6. As expected from structure, the data of

Figure 6. Temperature dependence of the product χmT at 0.1 T and molar magnetization Mm vs applied magnetic field B at 2.0 K (inset) of 2 (blue) and 3 (black ○).

both compounds share common features, and the χmT curves are qualitatively similar: At 290 K, χmT = 22.40 and 24.30 cm3 K mol−1 for 2 and 3, respectively, at 0.1 T. Again, these values are well-below the spin-only value of 12 non-interacting highspin FeIII centers (52.52 cm3 K mol−1). Cooling the compounds yields decreasing χmT values that reach 0.22 (2) and 0.86 cm3 K mol−1 (3) at 2.0 K. The molar magnetizations at 2.0 K show larger deviations from each other: For 2, Mm is almost linear in B up to 5.0 T taking a maximum value of 0.8 NA μB. For 3, a distinct change of the slope is observed at ∼1.5 T: steeper for lower fields, and less so for higher fields, for which the slopes of the Mm versus B curves of 2 and 3 are eventually the same (ca. B > 3 T). Mm reaches 1.4 NA μB at 5.0 T. Therefore, both compounds are characterized by dominant antiferromagnetic exchange interactions between the 12 iron centers of each compound. In addition, the strength of the interactions as well as the exchange pathways are comparable. Since the difference of χmT is not constant for all temperatures, the exchange interactions are potentially slightly different. However, both samples exhibit different small levels of paramagnetic impurities as revealed by the small difference of χmT at 2.0 K, and notably G

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry by the qualitatively different Mm curves. Although not as clear as for 1, the ground states of both compounds are most likely also characterized by a total effective spin of Stot = 0, since the saturation step for Stot = 1 occurs at 2 NA μB, which is not reached at 5.0 T. In addition, the shape of the Mm versus B curve of 3 below 2 T is characteristic for a single FeIII center if the corresponding contribution would be scaled down to ∼0.2 FeIII centers per formula unit of 3, which also causes a χmT value at 2.0 K as observed in the χmT versus T plot. The magnetic data of the {Fe22} compounds 4 and 5 are shown in Figure 7. As for 3 and 4, the χmT versus T curves are

essentially determines the exchange pathway and that the nature of exchange interactions is similar to the expectations of the superexchange model. Using these formulas to approximate the exchange interactions between the iron(III) centers of 1−5 reveals antiferromagnetic exchange interactions for almost all exchange pathways with 2J values between −10 and −40 cm−1 with a few exceptions up to −80 cm−1. In addition, the formulas indicate (potential) ferromagnetic exchange interactions for 1, 4, and 5: For 1, strictly following the rule of shortest Fe−O distances yields antiferromagnetic exchange interactions between the FeIII centers without exception. However, alternative but longer pathways including the central oxygen ion prefer a ferromagnetic exchange interaction. Since the FeIII ions additionally do not form a perfect but a slightly distorted octahedron, some of the interactions may be of ferromagnetic nature, for example, avoiding potential geometric spin frustration. For 4 and 5, the two central FeIII centers forming the axis of the propeller-shaped outer {Fe8} layers are calculated to interact ferromagnetically. This is in agreement with the analyses of similar shaped {Fe8} compounds.5 Since the χmT versus T curves of 4 and 5 do not reveal the characteristic features of ferromagnetic exchange interactions, the corresponding contributions of both axes (of the two {Fe8} substructures) most likely cancel each other due to an opposed alignment of their total magnetic moment. We hypothesize that this is caused by the molecular cluster structures in 4 and 5, where within a {Fe22} cluster the two {Fe8} subunits (and thus their axes) are inversion-symmetric to each other. Nevertheless, the estimations for all compounds prefer dominant antiferromagnetic exchange interactions within the compounds as found by the experimental data.

Figure 7. Temperature dependence of the product χmT at 0.1 T and molar magnetization Mm vs applied magnetic field B at 2.0 K (inset) of 4 (green) and 5 (brown).

similar as expected from the molecular structures. They exhibit a room-temperature value of χmT = 32.93 (4) and 32.56 cm3 K mol−1 (5) at 0.1 T, which are distinctly below the spin-only value of 22 non-interacting high-spin FeIII centers of 96.29 cm3 K mol−1. The values continuously decrease by decreasing temperature. At 2.0 K, they reach a value of 0.98 and 0.37 cm3 K mol−1 for 4 and 5, respectively. At this temperature, the molar magnetization as a function of the applied field of 4 is concave up to ca. 1.5 T, reaching 0.9 NA μB, which is indicative of small paramagnetic impurities. For higher fields, the curve becomes convex with steadily climbing values of Mm, up to 2.2 NA μB at 5.0 T. For 5, the concave segment of the curve is barely noticeable, therefore indicating almost negligible paramagnetic impurities. The Mm versus B curve is thus essentially a convex curve with a maximum value of 1.7 NA μB at 5.0 T. On the basis of both observations, the ground state of 5 is most likely characterized by a total effective spin of Stot = 0. In addition, the first excited state is only a few inverse centimeters above the ground state, which causes a nonvanishing magnetization due to a small thermal population even at 2.0 K. The conclusions are similar for 4, though a larger amount of paramagnetic impurities was present in the measured sample. Other than that, the magnetic properties of 4 and 5 vary in slightly different magnitudes of the exchange interactions. The observed magnetic data can be readily rationalized in terms of geometrical parameters, namely, the Fe−O distances and the FeIII−(μn-O)−FeIII angles. On the basis of the angular overlap model (AOM), Weihe and Güdel,14a and Werner et al.14b derived structure−property relationships for estimating the exchange interaction parameter J for oxo- and hydroxobridged FeIII sites. When corresponding AOM parameters are fit to experimental values, primarily from dinuclear iron(III) compounds, these models find that the shortest Fe−O distance

■

CONCLUSIONS

■

ASSOCIATED CONTENT

The presented {FeIIIn} cluster compounds demonstrate that an increase in nuclearity (n) correlates with an increasing degree of condensation processes in the clusters’ formation reactions, resulting in commensurately increasing (μn-O)/Fe ratios. Whereas it is 1:6 for the smallest {Fe6} product, this ratio reaches 6:12 and 18:22 for the {Fe12} and {Fe22} compounds, respectively. The title compounds highlight the pivotal role of multidentate O,N-ligands, namely, polyalcoholamines, that can induce partial or complete metathesis of the carboxylate ligands of the {Fe3} precursor, enabling subsequent condensation steps in the presence of small amounts of water, which appear to be controlled by both the solvents and the reaction temperature. Interestingly, the high-nuclearity {Fe12} and {Fe22} cluster structures (compounds 2−5) form for different ligand/solvent combinations, indicating a particular thermodynamic stability of their iron oxo core structures. Given the “building block” character of the {Fe22} cluster structures that can formally be decomposed into two {Fe8} and one {Fe6} subunits, we anticipate that further molecular growth is possible if we can employ the {Fe22} clusters as precursors in consecutive reactions, akin to the controlled molecular condensation reaction strategies that have greatly advanced polyoxometalate chemistry.

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b00994. H

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

(3) (a) Kögerler, P.; Tsukerblat, B.; Müller, A. Structure-related frustrated magnetism of nanosized polyoxometalates: aesthetics and properties in harmony. Dalton Trans. 2010, 39, 21−36. (b) Schröder, C.; Nojiri, H.; Schnack, J.; Hage, P.; Luban, M.; Kögerler, P. Competing Spin Phases in Geometrically Frustrated Magnetic Molecules. Phys. Rev. Lett. 2005, 94, 017205. (4) (a) Zhou, A.-J.; Leng, J.-D.; Hu, J.-S.; Tong, M.-L. High symmetry superoctahedron cluster [MnIII18O14]26+ from the use of N, N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine. Dalton Trans. 2013, 42, 9428−9431. (b) Ferguson, A.; Thomas, L. H.; Murrie, M. Coordinative flexibility of the 2-amino-2-(hydroxymethyl)propane-1,3diol ligand in the synthesis of polynuclear Fe(III) complexes. Polyhedron 2013, 52, 227−233. (c) Jones, L. F.; Low, D. M.; Helliwell, M.; Raftery, J.; Collison, D.; Aromí, G.; Cano, J.; Mallah, T.; Wernsdorfer, W.; Brechin, E. K.; McInnes, E. J. L. Fe(III) clusters built with tripodal alcohol ligands. Polyhedron 2006, 25, 325−333. (d) Brechin, E. K. Using tripodal alcohols to build high-spin molecules and single-molecule magnets. Chem. Commun. 2005, 5141−5153. (e) Foguet-Albiol, D.; Abboud, K. A.; Christou, G. High-nuclearity homometallic iron and nickel clusters: Fe22 and Ni24 complexes from the use of N-methyldiethanolamine. Chem. Commun. 2005, 4282− 4284. (f) Wittick, L. M.; Murray, K. S.; Moubaraki, B.; Batten, S. R.; Spiccia, L.; Berry, K. J. Synthesis, structure and magnetism of new single molecule magnets composed of MnII2MnIII2 alkoxo-carboxylate bridged clusters capped by triethanolamine ligands. Dalton Trans. 2004, 1003−1011. (5) Botezat, O.; van Leusen, J.; Ch Kravtsov, V.; Ellern, A.; Kögerler, P.; Baca, S. G. Iron(III) carboxylate/aminoalcohol coordination cluster with propeller-shaped Fe8 cores: approaching reasonable exchange energies. Dalton Trans. 2015, 44, 20753−20762. (6) Baca, S. G.; van Leusen, J.; Speldrich, M.; Kögerler, P. Understanding the magnetism of {Fe2Ln} dimers, step-by-step. Inorg. Chem. Front. 2016, 3, 1071−1075. (7) Botezat, O.; van Leusen, J.; Kravtsov, V. Ch.; Kögerler, P.; Baca, S. G. Ultralarge 3d/4f Coordination Wheels: From Carboxylate/ Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings. Inorg. Chem. 2017, 56, 1814−1822. (8) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (9) (a) Batchelor, L. J.; Shaw, R.; Markey, S. J.; Helliwell, M.; McInnes, E. J. L. An All-Vanadium(III) Hexametalate Lindqvist Structure and Its Chromium and Iron Analogues. Chem. - Eur. J. 2010, 16, 5554−5557. (b) Jiang, G.; Bai, J.; Xing, H.; Li, Y.; You, X. A. Tetrahedral Water Tetramer in a Zeolite-like Metal−Organic Framework Constructed from {(H3O)2[Fe6O{(OCH2)3CCH3}4Cl6]·4H2O}. Cryst. Growth Des. 2006, 6 (6), 1264−1266. (c) Spandl, J.; Kusserow, M.; Brüdgam, I. Alkoxo Compounds of Iron(III): Syntheses and Characterization of [Fe2(OtBu)6], [Fe2Cl2(OtBu)4], [Fe2Cl4(OtBu)2], and [N(nBu)4]2[Fe6OCl6(OMe)12]. Z. Anorg. Allg. Chem. 2003, 629, 968−974. (d) Chae, H. K.; Hwang, Ch.; Dong, Y.; Yun, H.; Jang, H. G. Synthesis of Na2[Fe6(OCH2CH2OCH3)18(μ6-O)]: Its Sol−Gel Application to Sr2FeMoO6. Chem. Lett. 2000, 29, 992−993. (10) Finn, R. C.; Zubieta, J. Solvatothermal Syntheses and Structural Characterizations of Polyoxoalkoxometalates: The Heptanuclear [{Fe(OH)(CH3CN)2} Fe6OCl6{(OCH2)3CCH2OH}4], the Decanuclear [Fe 10 O 2 Cl 8 {(OCH 2 ) 3 CCH 2 CH 3 } 6 ], and the Bimetallic [(VO)2Fe8O2Cl6{(OCH2)3CCH2CH3}6]. J. Cluster Sci. 2000, 11, 461−482. (11) Nachtigall, O.; Kusserow, M.; Clérac, R.; Wernsdorfer, W.; Menzel, M.; Renz, F.; Mrozinski, J.; Spandl, J. [Fe19] “Super-Lindqvist” Aggregate and Large 3D Interpenetrating Coordination Polymer from Solvothermal Reactions of [Fe2(OtBu)6] with Ethanol. Angew. Chem., Int. Ed. 2015, 54, 10361−10364. (12) Bagai, R.; Daniels, M. R.; Abboud, K. A.; Christou, G. Unusual Structural Types in Polynuclear Iron Chemistry from the Use of N, N,N′,N′-Tetrakis(2-hydroxyethyl)ethylenediamine (edteH4): Fe5, Fe6, and Fe12 Clusters. Inorg. Chem. 2008, 47, 3318−3327.

Description of IR spectra, packing diagrams, TGA/DTA curves (PDF) Accession Codes

CCDC 1823922−1823926 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +373-22-738154. Fax: +373-22-738149. ORCID

Paul Kögerler: 0000-0001-7831-3953 Svetlana G. Baca: 0000-0002-2121-2091 Author Contributions

The manuscript was written through contributions of all authors. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS Authors thank U. Englert for collecting X-ray diffraction data sets for 1−5. O.B. acknowledges a DAAD fellowship. REFERENCES

(1) (a) Theil, E. C.; Raymond, K. N. Transition-Metal Storage, Transport, and Biomineralization. In Bioinorganic Chemistry; Bertini, I., Gray, H. B., Lippard, S. J., Valentine, J. S., Eds.; University Science Books: Mill Valley, CA, 1994; pp 1−35. (b) Taft, K. L.; Papaefthymiou, G. C.; Lippard, S. J. Synthesis, Structure, and Electronic Properties of a Mixed-Valent Dodecairon Oxo Complex, a Model for the Biomineralization of Ferritin. Inorg. Chem. 1994, 33, 1510−1520. (c) Taft, K. L.; Papaefthymiou, G. C.; Lippard, S. J. A mixed-valent polyiron oxo complex that models the biomineralization of the ferritin core. Science 1993, 259, 1302−1305. (d) Chasteen, N. D.; Harrison, P. M. Mineralization in ferritin: an efficient means of iron storage. J. Struct. Biol. 1999, 126 (3), 182−189. (2) (a) Ako, A. M.; Mereacre, V.; Lan, Y.; Wernsdorfer, W.; Clerac, R.; Anson, C. E.; Powell, A. K. An Undecanuclear FeIII SingleMolecule Magnet. Inorg. Chem. 2010, 49, 1−3. (b) Bagai, R.; Wernsdorfer, W.; Abboud, K. A.; Christou, G. Exchange-Biased Dimers of Single-Molecule Magnets in OFF and ON States. J. Am. Chem. Soc. 2007, 129, 12918−12919. (c) Cornia, A.; Fabretti, A. C.; Garrisi, P.; Mortalo, C.; Bonacchi, D.; Gatteschi, D.; Sessoli, R.; Sorace, L.; Wernsdorfer, W.; Barra, A. L. Energy-barrier enhancement by ligand substitution in tetrairon(III) single-molecule magnets. Angew. Chem., Int. Ed. 2004, 43, 1136−1139. (d) MoraguesCanovas, M.; Riviere, P.; Ricard, L.; Paulsen, C.; Wernsdorfer, W.; Rajaraman, G.; Brechin, E. K.; Mallah, T. Resonant Quantum Tunneling in a New Tetranuclear Iron(III)-Based Single-Molecule Magnet. Adv. Mater. 2004, 16, 1101−1105. (e) Gatteschi, D.; Sessoli, R.; Cornia, A. Single-molecule magnets based on iron(III) oxo clusters. Chem. Commun. 2000, 725−732. (f) Goodwin, J. C.; Sessoli, R.; Gatteschi, D.; Wernsdorfer, W.; Powell, A. K.; Heath, S. L. Towards nanostructured arrays of single molecule magnets: new Fe 19 oxyhydroxide clusters displaying high ground state spins and hysteresis. J. Chem. Soc., Dalton Trans. 2000, 12, 1835−1840. (j) Barra, A. L.; Caneschi, A.; Cornia, A. F.; de Biani, F.; Gatteschi, D.; Sangregorio, C.; Sessoli, R.; Sorace, L. Single-Molecule Magnet Behavior of a Tetranuclear Iron(III) Complex. The Origin of Slow Magnetic Relaxation in Iron(III) Clusters. J. Am. Chem. Soc. 1999, 121, 5302−5310. I

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry (13) Zhou, A.; Bao, X.; Tong, M. New twisted-saddle dodecanuclear iron(III) clusters with adamantane-like [Fe4O6] core. Front. Chem. China 2009, 4 (4), 368−382. (14) (a) Weihe, H.; Güdel, H. U. Angular and Distance Dependence of the Magnetic Properties of Oxo-Bridged Iron(III) Dimers. J. Am. Chem. Soc. 1997, 119, 6539−6543. (b) Werner, R.; Ostrovsky, S.; Griesar, K.; Haase, W. Magnetostructural correlations in exchange coupled phenoxo-, alkoxo-, and hydroxo-bridged dinuclear iron(III) compounds. Inorg. Chim. Acta 2001, 326, 78−88.

J

DOI: 10.1021/acs.inorgchem.8b00994 Inorg. Chem. XXXX, XXX, XXX−XXX