Synthesis and Characterization of <i>N</i>¹-(4-Toluenesulfonyl)-<i>N</i>¹- (9-anthracenemethyl)triamines

A modular synthetic approach was developed to access triamines with varying tether lengths from commercially available aminoalkanols. Initial N-alkylation via reductive amination with anthracene-9-carbaldehyde provided the secondary amines in good yield. Subsequent ditosylation with excess TsCl yielded the respective bis-N,O-tosylates. The tosylates were reacted with excess putrescine to give the final triamines. X-ray crystallography revealed that the polyamine tail is preferentially oriented over the shielding cone of the anthracene ring

Unusual Weakly Coordinating Anion Reactivity in Metallocene Chemistry. Formation of Tantalocene Cation−Dinuclear Anion Pairs

Unlike the clean reaction of group 4 metallocene alkyls with B(C6F5)3, the reaction of Cp2TaMe3 with M(C6F5)3 (M = B, Al) in benzene or toluene produces an oily product mixture containing the expected Cp2TaMe2+CH3M(C6F5)3- as well as the unexpected Cp2TaMe2+[(C6F5)3MCH3M(C6F5)3]- in equilibrium, along with unreacted Cp2TaMe3. The surprising reactivity of weakly coordinating anions CH3M(C6F5)3- in the abstractive metallocene chemistry renders formation of novel μ-Me-bridged dinuclear anions. Subsequently, the reaction of Cp2TaMe3 with 2 equiv of Al(C6F5)3 cleanly generates the tantalocene cation−dinulcear anion ion pair Cp2TaMe2+[(C6F5)3AlCH3Al(C6F5)3]- as colorless crystals in a quantitative yield. A crystallographic study confirms the structure, which reveals unassociated cation−anion pairs with nearly symmetrical μ-CH3 bridging in the anion portion

New Mixed-Valent Mn Clusters from the Use of <i>N</i>,<i>N</i>,<i>N′</i>,<i>N′</i>-Tetrakis(2-hydroxyethyl)ethylenediamine (edteH₄): Mn₃, Mn₄, Mn₆, and Mn₁₀

The syntheses, crystal structures, and magnetochemical characterization are reported for the new mixed-valent Mn clusters [Mn2IIMnIII(O2CMe)2(edteH2)2]­(ClO4) (1), [MnII2MnIII2(edteH2)2(hmp)2Cl2]­(MnIICl4) (2), [MnIII6O2(O2CBut)6(edteH)2(N3)2] (3), [Na2MnIII8MnII2O4(OMe)2(O2CEt)6(edte)2(N3)6] (4), and (NEt4)2[Mn8IIIMn2IIO4(OH)2-(O2CEt)6(edte)2(N3)6]­(5), where edteH4 is N,N,N′,N′-tetrakis-(2-hydroxyethyl)­ethylenediamine and hmpH is 2-(hydroxymethyl)­pyridine. 1–5 resulted from a systematic exploration of the effect of different Mn sources, carboxylates, the presence of azide, and other conditions, on the Mn/edteH4 reaction system. The core of 1 consists of a linear MnIIMnIIIMnII unit, whereas that of 2 is a planar Mn4 rhombus within a [MnII2MnIII2(μ3-OR)2] incomplete-dicubane unit. The core of 3 comprises a central [MnIII4(OR)2] incomplete-dicubane on either side of which is edge-fused a triangular [MnIII3(μ3-O)] unit. The cores of 4 and 5 are similar and consist of a central [MnII2MnIII2(μ3-OR)2] incomplete-dicubane on either side of which is edge-fused a distorted [MnIIMnIII3(μ3-O)2(μ3-OR)2] cubane unit. Variable-temperature, solid-state direct current (dc) and alternating current (ac) magnetization studies were carried out on 1–5 in the 5.0–300 K range, and they established the complexes to have ground state spin values of S = 3 for 1, S = 9 for 2, and S = 4 for 3. The study of 3 provided an interesting caveat of potential pitfalls from particularly low-lying excited states. For 4 and 5, the ground state is in the S = 0–4 range, but its identification is precluded by a high density of low-lying excited states

Carboxylate-Free Mn^III₂Ln^III₂ (Ln = Lanthanide) and Mn^III₂Y^III₂ Complexes from the Use of (2-Hydroxymethyl)pyridine: Analysis of Spin Frustration Effects

The initial employment of 2-(hydroxymethyl)pyridine for the synthesis of Mn/Ln (Ln = lanthanide) and Mn/Y clusters, in the absence of an ancillary organic ligand, has afforded a family of tetranuclear [MnIII2MIII2(OH)2(NO3)4(hmp)4(H2O)4](NO3)2 (M = Dy, 1; Tb, 2; Gd, 3; Y; 4) anionic compounds. 1–4 possess a planar butterfly (or rhombus) core and are rare examples of carboxylate-free Mn/Ln and Mn/Y clusters. Variable-temperature dc and ac studies established that 1 and 2, which contain highly anisotropic LnIII atoms, exhibit slow relaxation of their magnetization vector. Fitting of the obtained magnetization (M) versus field (H) and temperature (T) data for 3 by matrix diagonalization and including only axial anisotropy (zero-field splitting, ZFS) showed the ground state to be S = 3. Complex 4 has an S = 0 ground state. Fitting of the magnetic susceptibility data collected in the 5–300 K range for 3 and 4 to the appropriate van Vleck equations revealed, as expected, extremely weak antiferromagnetic interactions between the paramagnetic ions; for 3, J1 = −0.16(2) cm–1 and J2 = −0.12(1) cm–1 for the MnIII···MnIII and MnIII···GdIII interactions, respectively. The S = 3 ground state of 3 has been rationalized on the basis of the spin frustration pattern in the molecule. For 4, J = −0.75(3) cm–1 for the MnIII···MnIII interaction. Spin frustration effects in 3 have been quantitatively analyzed for all possible combinations of sign of J1 and J2

Unusual Structural Types in Manganese Cluster Chemistry from the Use of <i>N</i>,<i>N</i>,<i>N</i>‘,<i>N</i>‘-Tetrakis(2-hydroxyethyl)ethylenediamine: Mn₈, Mn₁₂, and Mn₂₀ Clusters

The syntheses, crystal structures, and magnetochemical characterization are reported for three new mixed-valent Mn clusters [Mn8O3(OH)(OMe)(O2CPh)7(edte)(edteH2)](O2CPh) (1), [Mn12O4(OH)2(edte)4Cl6(H2O)2] (2), and [Mn20O8(OH)4(O2CMe)6(edte)6](ClO4)2 (3) (edteH4 = (HOCH2CH2)2NCH2CH2N(CH2CH2OH)2 = N,N,N‘,N‘-tetrakis(2-hydroxyethyl)ethylenediamine). The reaction of edteH4 with Mn(O2CPh)2, MnCl2, or Mn(O2CMe)2 gives 1, 2, and 3, respectively, which all possess unprecedented core topologies. The core of 1 comprises two edge-sharing [Mn4O4] cubanes connected to an additional Mn ion by a μ3-OH- ion and two alkoxide arms of edteH22-. The core of 2 consists of a [Mn12(μ4-O)4]24+ unit with S4 symmetry. The core of 3 consists of six fused [Mn4O4] cubanes in a 3 × 2 arrangement and linked to three additional Mn atoms at both ends. Variable-temperature, solid-state dc and ac magnetization (M) studies were carried out on complexes 1−3 in the 5.0−300 K range. Fitting of the obtained M/NμB vs H/T data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave ground-state spin (S) and axial ZFS parameter (D) of S = 8, D = −0.30 cm-1 for 1, S = 7, D = −0.16 cm-1 for 2, and S = 8, D = −0.16 cm-1 for 3. The combined work demonstrates that four hydroxyethyl arms on an ethylenediamine backbone can generate novel Mn structural types not accessible with other alcohol-based ligands

A New N,N,O Chelate for Transition Metal Chemistry: Fe₅ and Fe₆ Clusters from the Use of 6-Hydroxymethyl-2,2‘-bipyridine (hmbpH)

The initial use of the anion of 6-hydroxymethyl-2,2‘-bipyridine (hmbpH) as a chelate in coordination chemistry is described. The syntheses, crystal structures, and magnetochemical characterization are reported of four new iron(III) clusters [Fe5O2(OH)(O2CMe)5(hmbp)3](ClO4)2 (1) and [Fe6O2(OH)2(O2CR)6(hmbp)4](NO3)2 (R = Ph (2), Me (3), But (4); hmbpH = 6-hydroxymethyl-2,2‘-bipyridine). The reaction of Fe(ClO4)3, hmbpH, and sodium acetate in a 1:1:∼4 ratio in EtOH gave 1, and the reaction between [Fe3O(O2CR)6(H2O)3](NO3) (R = Ph, Me, But) and hmbpH in a 1:1 ratio in MeCN gave 2−4, respectively. The core of 1 consists of a [Fe4(μ3-O)2]8+ butterfly unit to which is attached a fifth Fe atom by bridging O atoms. The core of 2−4 also consists of a [Fe4(μ3-O)2]8+ butterfly unit to which are attached an Fe atom on either side by bridging O atoms. Variable-temperature (T) and -field (H) solid-state DC and AC magnetization (M) studies were carried out on complexes 1−4 in the 5.0−300 K range. Fitting of the data revealed that 1 has an S = 5/2 ground state spin whereas 2−4 possess an S = 5 ground state. Fitting of the M/NμB vs H/T data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave values of the axial ZFS parameter |D| of 0.75, 0.36, 0.46, and 0.36 cm-1 for 1−4, respectively

Carboxylate-Free Mn^III₂Ln^III₂ (Ln = Lanthanide) and Mn^III₂Y^III₂ Complexes from the Use of (2-Hydroxymethyl)pyridine: Analysis of Spin Frustration Effects

The initial employment of 2-(hydroxymethyl)pyridine for the synthesis of Mn/Ln (Ln = lanthanide) and Mn/Y clusters, in the absence of an ancillary organic ligand, has afforded a family of tetranuclear [MnIII2MIII2(OH)2(NO3)4(hmp)4(H2O)4](NO3)2 (M = Dy, 1; Tb, 2; Gd, 3; Y; 4) anionic compounds. 1–4 possess a planar butterfly (or rhombus) core and are rare examples of carboxylate-free Mn/Ln and Mn/Y clusters. Variable-temperature dc and ac studies established that 1 and 2, which contain highly anisotropic LnIII atoms, exhibit slow relaxation of their magnetization vector. Fitting of the obtained magnetization (M) versus field (H) and temperature (T) data for 3 by matrix diagonalization and including only axial anisotropy (zero-field splitting, ZFS) showed the ground state to be S = 3. Complex 4 has an S = 0 ground state. Fitting of the magnetic susceptibility data collected in the 5–300 K range for 3 and 4 to the appropriate van Vleck equations revealed, as expected, extremely weak antiferromagnetic interactions between the paramagnetic ions; for 3, J1 = −0.16(2) cm–1 and J2 = −0.12(1) cm–1 for the MnIII···MnIII and MnIII···GdIII interactions, respectively. The S = 3 ground state of 3 has been rationalized on the basis of the spin frustration pattern in the molecule. For 4, J = −0.75(3) cm–1 for the MnIII···MnIII interaction. Spin frustration effects in 3 have been quantitatively analyzed for all possible combinations of sign of J1 and J2

Largest Mixed Transition Metal/Actinide Cluster: A Bimetallic Mn/Th Complex with a [Mn₁₀Th₆O₂₂(OH)₂]¹⁸⁺ Core

A high-nuclearity mixed transition metal/actinide complex has been prepared from the reaction of a MnIII4 complex with Th(NO3)4 in MeCN/MeOH. The complex [Th6Mn10O22(OH)2(O2CPh)16(NO3)2(H2O)8] is the largest such complex to date and the first Th/Mn species. It is rich in oxide groups, which stabilize all of the metals in the high ThIV and MnIV oxidation levels. Magnetic characterization establishes that the complex has an S = 3 ground-state spin value

A New N,N,O Chelate for Transition Metal Chemistry: Fe₅ and Fe₆ Clusters from the Use of 6-Hydroxymethyl-2,2‘-bipyridine (hmbpH)

The initial use of the anion of 6-hydroxymethyl-2,2‘-bipyridine (hmbpH) as a chelate in coordination chemistry is described. The syntheses, crystal structures, and magnetochemical characterization are reported of four new iron(III) clusters [Fe5O2(OH)(O2CMe)5(hmbp)3](ClO4)2 (1) and [Fe6O2(OH)2(O2CR)6(hmbp)4](NO3)2 (R = Ph (2), Me (3), But (4); hmbpH = 6-hydroxymethyl-2,2‘-bipyridine). The reaction of Fe(ClO4)3, hmbpH, and sodium acetate in a 1:1:∼4 ratio in EtOH gave 1, and the reaction between [Fe3O(O2CR)6(H2O)3](NO3) (R = Ph, Me, But) and hmbpH in a 1:1 ratio in MeCN gave 2−4, respectively. The core of 1 consists of a [Fe4(μ3-O)2]8+ butterfly unit to which is attached a fifth Fe atom by bridging O atoms. The core of 2−4 also consists of a [Fe4(μ3-O)2]8+ butterfly unit to which are attached an Fe atom on either side by bridging O atoms. Variable-temperature (T) and -field (H) solid-state DC and AC magnetization (M) studies were carried out on complexes 1−4 in the 5.0−300 K range. Fitting of the data revealed that 1 has an S = 5/2 ground state spin whereas 2−4 possess an S = 5 ground state. Fitting of the M/NμB vs H/T data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave values of the axial ZFS parameter |D| of 0.75, 0.36, 0.46, and 0.36 cm-1 for 1−4, respectively

Unusual Structural Types in Manganese Cluster Chemistry from the Use of <i>N</i>,<i>N</i>,<i>N</i>‘,<i>N</i>‘-Tetrakis(2-hydroxyethyl)ethylenediamine: Mn₈, Mn₁₂, and Mn₂₀ Clusters

The syntheses, crystal structures, and magnetochemical characterization are reported for three new mixed-valent Mn clusters [Mn8O3(OH)(OMe)(O2CPh)7(edte)(edteH2)](O2CPh) (1), [Mn12O4(OH)2(edte)4Cl6(H2O)2] (2), and [Mn20O8(OH)4(O2CMe)6(edte)6](ClO4)2 (3) (edteH4 = (HOCH2CH2)2NCH2CH2N(CH2CH2OH)2 = N,N,N‘,N‘-tetrakis(2-hydroxyethyl)ethylenediamine). The reaction of edteH4 with Mn(O2CPh)2, MnCl2, or Mn(O2CMe)2 gives 1, 2, and 3, respectively, which all possess unprecedented core topologies. The core of 1 comprises two edge-sharing [Mn4O4] cubanes connected to an additional Mn ion by a μ3-OH- ion and two alkoxide arms of edteH22-. The core of 2 consists of a [Mn12(μ4-O)4]24+ unit with S4 symmetry. The core of 3 consists of six fused [Mn4O4] cubanes in a 3 × 2 arrangement and linked to three additional Mn atoms at both ends. Variable-temperature, solid-state dc and ac magnetization (M) studies were carried out on complexes 1−3 in the 5.0−300 K range. Fitting of the obtained M/NμB vs H/T data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave ground-state spin (S) and axial ZFS parameter (D) of S = 8, D = −0.30 cm-1 for 1, S = 7, D = −0.16 cm-1 for 2, and S = 8, D = −0.16 cm-1 for 3. The combined work demonstrates that four hydroxyethyl arms on an ethylenediamine backbone can generate novel Mn structural types not accessible with other alcohol-based ligands