Synthesis and Reaction of [{HC(CMeNAr)₂}Mn]₂ (Ar = 2,6-iPr₂C₆H₃):  The Complex Containing Three-Coordinate Manganese(I) with a Mn−Mn Bond Exhibiting Unusual Magnetic Properties and Electronic Structure

Abstract

This paper reports on the synthesis, X-ray structure, magnetic properties, and DFT calculations of [[HC(CMeNAr)2]Mn]2 (Ar = 2,6-iPr2C6H3) (2), the first complex with three-coordinate manganese(I). Reduction of the iodide [[HC(CMeNAr)2]Mn(mu-I)]2 (1) with Na/K in toluene afforded 2 as dark-red crystals. The molecule of 2 contains a Mn2(2+) core with a Mn-Mn bond. The magnetic investigations show a rare example of a high-spin manganese(I) complex with an antiferromagnetic interaction between the two Mn(I) centers. The DFT calculations indicate a strong s-s interaction of the two Mn(I) ions with the open shell configuration (3d54s1). This suggests that the magnetic behavior of 2 could be correctly described as the coupling between two S1 = S2 = 5/2 spin centers. The Mn-Mn bond energy is estimated at 44 kcal mol(-1) by first principle calculations with the B3LYP functional. The further oxidative reaction of 2 with KMnO4 or O2 resulted in the formation of manganese(III) oxide [[HC(CMeNAr)2]Mn(mu-O)]2 (3). Compound 3 shows an antiferromagnetic coupling between the two oxo-bridged manganese(III) centers by magnetic measurements.

Theory‐Guided Experiments on the Mechanistic Elucidation of the Reduction of Dinuclear Zinc, Manganese, and Cadmium Complexes

“…Attempts to probe both intermediates Ia and Ib failed. To this end, we turned our attention from zinc to manganese and cadmium, because they not only show structural similarity in the reported M I M I ‐bonded dinuclear complexes [(κ 2 ‐Nacnac)MM(κ 2 ‐Nacnac)] (M=Zn,2o Mn;4 Nacnac=HC[C(Me)NDipp] 2 ) and [Ar′MMAr′] (M=Zn,2n Cd;5 Ar′=2,6‐(2,6‐ i Pr 2 C 6 H 3 ) 2 C 6 H 3 ), but also feature an identical MM σ‐bonding scheme. Herein we report structural transformations on reduction of dinuclear manganese and cadmium complexes [Mn 2 {κ 2 ‐Me 2 Si(NDipp) 2 } 2 ] ( 3 ) and [Cd 2 {μ‐κ 2 ‐Me 2 Si(NDipp) 2 } 2 ] ( 4 ).…”

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

“…Among the many compounds of diverse composition and structures, remarkable examples of low-valent metal β-diketiminate complexes have been isolated, including (BDI*) MM(BDI*) (M = Mg, 43 Mn, 44 Zn 45 ) and Al(BDI*), 46,47 reasonably formulated as complexes of Mg(I), Mn(I), Zn(I) and Al(I), respectively. Among the many compounds of diverse composition and structures, remarkable examples of low-valent metal β-diketiminate complexes have been isolated, including (BDI*) MM(BDI*) (M = Mg, 43 Mn, 44 Zn 45 ) and Al(BDI*), 46,47 reasonably formulated as complexes of Mg(I), Mn(I), Zn(I) and Al(I), respectively.…”

Non-innocence of β-diketiminato ligands

“…According to the easy tunability of the steric and electronic properties of these ligands as well as their variable binding motifs [4], which range from pure s to a combination of s and p donation, they have evolved into one of the most ubiquitous systems in coordination chemistry. The kinetic stabilization of low-coordinated metal complexes such as low-valent MeM dimers of zinc [5], magnesium [6], manganese [7] and tin, respectively [8], in which the metal atoms adopt the formal oxidation state þI, by use of sterically very demanding b-diketiminate ligands has been of particular interest [9e13]. Moreover, b-diketiminate metal complexes are promising catalysts in different catalytic reactions such as ring opening polymerization (ROP) of cyclic ethers and others [14e17] as well as in the copper catalyzed CeH amination and etherification [18,19], or magnesium and calcium catalyzed dehydrocoupling of amino-boranes [20].…”