Versatile Reactivity of MnII Complexes in Reactions with N-Donor Heterocycles: Metamorphosis of Labile Homometallic Pivalates vs. Assembling of Endurable Heterometallic Acetates

Abstract

Reaction of 2,2′-bipyridine (2,2′-bipy) or 1,10-phenantroline (phen) with [Mn(Piv)2(EtOH)]n led to the formation of binuclear complexes [Mn2(Piv)4L2] (L = 2,2′-bipy (1), phen (2); Piv- is the anion of pivalic acid). Oxidation of 1 or 2 by air oxygen resulted in the formation of tetranuclear MnII/III complexes [Mn4O2(Piv)6L2] (L = 2,2′-bipy (3), phen (4)). The hexanuclear complex [Mn6(OH)2(Piv)10(pym)4] (5) was formed in the reaction of [Mn(Piv)2(EtOH)]n with pyrimidine (pym), while oxidation of 5 produced the coordination polymer [Mn6O2(Piv)10(pym)2]n (6). Use of pyrazine (pz) instead of pyrimidine led to the 2D-coordination polymer [Mn4(OH)(Piv)7(µ2-pz)2]n (7). Interaction of [Mn(Piv)2(EtOH)]n with FeCl3 resulted in the formation of the hexanuclear complex [MnII4FeIII2O2(Piv)10(MeCN)2(HPiv)2] (8). The reactions of [MnFe2O(OAc)6(H2O)3] with 4,4′-bipyridine (4,4′-bipy) or trans-1,2-(4-pyridyl)ethylene (bpe) led to the formation of 1D-polymers [MnFe2O(OAc)6L2]n·2nDMF, where L = 4,4′-bipy (9·2DMF), bpe (10·2DMF) and [MnFe2O(OAc)6(bpe)(DMF)]n·3.5nDMF (11·3.5DMF). All complexes were characterized by single-crystal X-ray diffraction. Desolvation of 11·3.5DMF led to a collapse of the porous crystal lattice that was confirmed by PXRD and N2 sorption measurements, while alcohol adsorption led to porous structure restoration. Weak antiferromagnetic exchange was found in the case of binuclear MnII complexes (JMn-Mn = −1.03 cm−1 for 1 and 2). According to magnetic data analysis (JMn-Mn = −(2.69 ÷ 0.42) cm−1) and DFT calculations (JMn-Mn = −(6.9 ÷ 0.9) cm−1) weak antiferromagnetic coupling between MnII ions also occurred in the tetranuclear {Mn4(OH)(Piv)7} unit of the 2D polymer 7. In contrast, strong antiferromagnetic coupling was found in oxo-bridged trinuclear fragment {MnFe2O(OAc)6} in 11·3.5DMF (JFe-Fe = −57.8 cm−1, JFe-Mn = −20.12 cm−1).

Stability of Manganese(II)–Pyrazine, –Quinoxaline or –Phenazine Complexes and Their Potential as Carbonate Sequestration Agents

“…As far as we know, there are no reports concerning the formation constants of the manganese(II) complexes with pyrazine, quinoxaline or phenazine in methanol or any other solvent. Nevertheless, a few manganese(II) complexes with pyrazine- [ 26 , 27 , 28 , 29 ], quinoxaline- [ 30 , 31 , 32 ] or phenazine- [ 33 , 34 ] based ligands have been reported before. The electronic spectra of the methanol solutions of manganese(II)–pyrazine complexes are shown in Figure S1 , those for the manganese(II)–quinoxaline complex are shown in Figure S2 and those for the manganese(II)–phenazine complex are shown in Figure S3 .…”

Structural and Magnetic Properties of a Pyridyl(vinyl)benzoate-Based Metal–Organic Framework with Iron(II) as Spin Carrier

“…Therefore, versatile ligands with various coordination modes such as carboxylate derivatives are envisaged for their potential to generate a plethora of structural arrangements and topologies . This synthetic approach, based on the variation of metal ions and carboxylate based ligands, can also be expanded by the functionalization of the carboxylate derivatives with other coordination sites and/or with the use of short bridging oxo- or hydroxo coligands, giving rise to oxo- or hydroxo-centered carboxylato-based polynuclear motifs as secondary building units for the development of CPs with more complex topologies. − Although oxo- or hydroxo-centered carboxylato-based compounds with transition and/or lanthanide metal ions are reported, − those with triangular iron motifs are notable for their intriguing and complex magnetic properties. − …”

Cage-like manganesesilsesquioxanes: features of their synthesis, unique structure, and catalytic activity in oxidative amidations

“…Even less is known about the properties and catalytic applications of these metallacomplexes. 38,39 Keeping in mind the uniqueness of molecular topologies and potential reactivity of these complexes, [40][41][42][43][44][45] we became interested in further exploring Mn-based silsesquioxanes, especially in the context of the first catalytic evaluation of these compounds in oxidative amidation (OA) of alcohols. Many research groups focus on this catalytic transformation because amide bonds are mainly present in natural products, essential medicals, and polyfunctional materials.…”