Covalent Metal–Metal-Bonded Mn₄ Tetrahedron Inscribed within a Four-Coordinate Manganese Cubane Cluster, As Evidenced by Unexpected Temperature-Independent Diamagnetism

Abstract

The electronic structures of the manganese(IV) cubane cluster Mn(μ-NBu)(NBu) (1) and its one-electron-oxidized analogue, the 3:1 Mn/Mn cluster [Mn(μ-NBu)(NBu)][PF] (1[PF]), are described. The S = 0 spin quantum number of 1 is explained by a diamagnetic electronic structure where all metal-based d electrons are paired in Mn-Mn bonding orbitals. Temperature- and power-dependent studies of the S = / electron paramagnetic resonance signal of 1 are consistent with an electronic structure described as a delocalized one-electron radical.

Metal–Metal Bonds: From Fundamentals to Applications

“…Electron delocalization among the three high-spin Fe atoms results in an S = 11 / 2 ground state, which, when coupled with the axial anisotropy of the compound, results in single-molecule magnetic behavior with a blocking temperature of 1.5 K. Moving over from Fe to Mn and increasing the cluster size from 3 to 4, the Zdilla group describes a tetramanganese cubane-type cluster with bridging and terminal imido ligands. Although ligand-field theory predicts an S = 3 / 2 ground state for each Mn­(IV) ion, the Mn 4 16+ complex is diamagnetic because of delocalization of the Mn 4 orbitals via Mn–Mn bonds of 2.54–2.56 Å …”

“…Although ligand-field theory predicts an S = 3 / 2 ground state for each Mn(IV) ion, the Mn 4 16+ complex is diamagnetic because of delocalization of the Mn 4 orbitals via Mn−Mn bonds of 2.54−2.56 Å. 15 Besides cluster geometries, one-dimensional chain structures based on metal−metal bonds have been of significant interest since the days of Krogmann salts 16 and oligomeric platinum blues. 17 In this issue, Uemura and co-workers utilize one of the prototypical platinum blues, platinum(II) cis-diamminepivalamidate, as a unit that is linked to paramagnetic diruthenium tetraacetate.…”

Electrochemical Investigation of Low-Valent Multiply M≡M Bonded Group VI Dimers: A Standard Chemical Reduction Leads to an Unexpected Product

“…Multimetallic complexes bearing singly and multiply bonded metal ions play a major role in both biogenic and anthropogenic chemistries. , The study of these complexes ushered in many breakthroughs in a broad range of fields such as catalysis, photochemistry, and single-molecule magnets, with significant strides made over the course of the last 30 years. − Synthetically elusive targets, including but not limited to the first quintuply bonded transition-metal complex Ar′Cr 2 Ar′ (Ar′ = C 6 H 3 -2,6­(C 6 H 3 -2,6- i Pr 2 ) 2 ), a series of complexes bearing a uranium–M bond (where M = Ni, Pd, Pt), and collections of Fe 3 and Mn 4 clusters with unexpected magnetic properties, have all been prepared and investigated with respect to their reactivity. ,− While the outlook for synthetically novel metal–metal-bonded complexes is promising, there are still gaps in our understanding of the structure and reactivity of some of the most prototypical examples of metal–metal multiply bonded complexes, particularly those of the form M 2 (CH 2 CMe 3 ) 6 where M = W ( 1 ), Mo ( 2 ). − …”

Synthesis, Characterization and Magnetic Studies of a Tetranuclear Manganese(II/IV) Compound Incorporating an Amino-Alcohol Derived Schiff Base

“…The most common oxidation state originates in these hetero-valence manganese complexes are Mn II , Mn III and Mn IV [11][12][13]. Due to the presence of numerous possibilities in different magnetic coupling between pairs of ions in various oxidation states (II/II, II/III, II/IV, III/III, III/IV and IV/IV pairs), very high values of total molecular spin (S) [14][15][16][17] are an expected phenomenon in these complexes. The molecular magnetism of mixed-valence tetranuclear manganese clusters has been explored, and has been examined as biomimetic models of PS II [1,2,[14][15][16].…”