Many Mg–Mg bonds form the core of the Mg₁₆Cp*8Br₄K cluster anion: the key to a reassessment of the Grignard reagent (GR) formation process?

Abstract

It caused a sensation eight years ago, when the first room temperature stable molecular compound with a Mg–Mg bond (LMgMgL, L = chelating ligand) containing magnesium in the oxidation state +1 was prepared.

Addition of Carbon–Fluorine Bonds to a Mg(I)–Mg(I) Bond: An Equivalent of Grignard Formation in Solution

“…14 On the basis of preliminary observations, we suggest that carbon–fluorine bond cleavage may not proceed through radical intermediates and the concerted pathway remains most likely. 15 Although a crossover experiment between 1 and 3 results in slow formation of the asymmetric species 4 at 25 °C (Figure 4a and 5), this result could be explained by a ligand exchange reaction in which the Mg–Mg core remains intact.…”

(Multi‐)Metallic Cluster Growth

“…The cluster isomer represents the global minimum structure, obtained selectively after slow re‐arrangement processes at room temperature from the cyclic isomer, as the kinetic product. As observed for the tin atoms in [Sn 4 (GeAr′) 2 ], the germanium atoms in [Si 4 Ge 2 (Tip) 6 ] originate from a tetrel(II) precursor, GeCl 2 ⋅dioxane in this case. An analogue silicon cluster, [Si 6 (Tip) 6 ], is formed upon reduction of [Si 3 (Tip) 3 Cl 3 ] …”

“…In 2016, Schnöckel and co‐workers reported the first metalloid magnesium cluster, which represents a potential snapshot intermediate from the bulk metal to a Grignard reagent . A magnesium(I) halide was produced at higher temperature and stabilized in a metastable solution at −40 °C.…”

“…radical is assumed to be a transition state that immediately decomposes, e.g., in ether‐like solution into solid Mg and MgBr 2 . Energy values are given in kJ mol −1 ; values per mole of Mg atoms are given in brackets …”

Two‐Coordinate Magnesium(I) Dimers Stabilized by Super Bulky Amido Ligands

“…In every case, these compounds are kinetically stabilized by sterically bulky N , N ′‐chelating, or N , N ′, O ‐tripodal, anionic ligands, so far confined to a range of β‐diketiminates, a guanidinate, a diiminophosphinate, an ene‐diamide, and several diimine‐enolates (Figure ) . Additional examples include a remarkable mixed valence magnesium cluster anion, [Mg 16 Cp* 8 Br 4 K] − (Cp*=C 5 Me 5 − ), which was recently reported and shown by computational studies to contain no less than 27 Mg−Mg bonds …”