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

Ruslan Polunin,Anton Lytvynenko,Artem Bogomyakov,Igor Eremenko,Olivier Cador,Igor Evstifeev,Stéphane Golhen,Sergey Kolotilov,Nikolay Efimov,Konstantin Gavrilenko,Lahcène Ouahab,Vadim Minin,Mikhail Kiskin

doi:10.3390/molecules26041021

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).

Highlights

[Mn initial reaction system resulted in rearrangement of the dinuclear molecules to tetranuclear complexes [Mn2 II Mn2 III O2 (Piv)6 L2 ] (L = 2,20 -bipy (3), phen (4))
The use of pyrazine instead of pyrimidine in the reaction with [Mn(Piv)2 (EtOH)]n in MeCN under an argon atmosphere led to the formation of the 2D-coordination polymer [Mn4 (OH)(Piv)7 (μ2 -pz)2 ]n (7)
The composition of the coordination polymers based on MnFe2 O(OAc)6 was probably governed by a fine balance between formation and crystallization kinetics and solubility of certain species, in contrast to the ratio of potential vacations in the coordination spheres of metal ions and the number of donor atoms)

Summary

Introduction

Polynuclear coordination compounds of transition metals are widely used as catalysts in various reactions [1,2,3,4,5], as starting materials for the preparation of nanosized oxidesPolynuclear coordination compounds of transition metals are widely used as cata‐lysts in various reactions [1,2,3,4,5], as starting materials for the preparation of nanosized ox‐ides or metals [6,7,8], as well as the basis creation newmagnetic magneticmaterials materials [9,10,11,12,13] [9,10,11,12,13]or metals [6,7,8], as well as the basis forfor thethe creation ofofnew and coordination polymers with remarkable properties [14,15,16,17,18,19,20].In the majority of these and coordination polymers with remarkable properties [14,15,16,17,18,19,20]. Polynuclear coordination compounds of transition metals are widely used as catalysts in various reactions [1,2,3,4,5], as starting materials for the preparation of nanosized oxides. Introduction of pyrimidine ligands resulted in formation new coordination polymers. The use of pyrazine (pz) instead of pyrimidine in the reaction with [Mn(Piv) (EtOH)]n in MeCN under an argon atmosphere led to the formation of the 2D-coordination polymer [Mn4 (OH)(Piv) (μ2 -pz)2 ]n (7). This complex was stable in air and was not soluble in. From an analysis of literature, as well as from the results of this study it can be noted that the tetranuclear unit {MnII 2 MnIII 2 O2 (O2 CR)6 } usually forms in the presence of chelating ligands, such as 2,20 -bipy and phen, while the hexanuclear unit

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