MgCl und Mg₂Cl₂: von theoretischen und thermodynamischen Überlegungen zur Spektroskopie und Chemie von Mg‐Mg‐Spezies

Abstract

Verbindungen mit Metall-Metall-Bindungen der Hauptgruppenelemente haben in jüngster Zeit eine unerwartet hohe Aufmerksamkeit erfahren. [1][2][3][4][5] Trotz der jüngsten strukturellen Befunde zu zwei kristallinen Mg 2 R 2 -Verbindungen (R1 = [ArNC(NiPr 2 )NAr] À ; R2= [{ArNCMe} 2 CH] À ; Ar= 2,6-Diisopropylphenyl, iPr = Isopropyl) [2] und trotz zahlreicher theoretischer Studien zu Molekülem mit Mg-Mg-Bindungen [10][11][12] Nachdem sich vor gut 50 Jahren der erste Hinweis auf stabile Erdalkali(I)-halogenide als Irrtum erwiesen hatte, [13] gelang vor knapp 40 Jahren der erste ESR-spektroskopische Nachweis unter anderem von MgF in einer Edelgasmatrix. [18] Hierzu wurde MgF 2 bei 1250 8C verdampft, die gasförmigen MgF 2 -Moleküle bei 2350 8C zu MgF und F-Atomen dissoziiert und anschließend in der Matrix abgeschieden.[19] Um zu einem für Synthesestudien praktikablen Verfahren analog zur AlCl-Synthese bei 900 8C zu gelangen, [6]

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

“…Cp*MgMgCp*, have met with failure. [9,10] Indeed, based on the results of experimental and computational studies, Schnöckel and co-workers have suggested that the synthesis of stable non-chelated magnesium(I) dimers will be "difficult, and perhaps impossible". [10] It should be noted here that the same group have developed specialized synthetic routes to metastable (decomp.…”

Experimentally Based DFT Calculations on the Hindered Disproportionation of [Al4Cp*4]: Formation of Metalloid Clusters as Intermediates on the Way to Solid Al Prevents the Decomposition of a Textbook Molecule

“…A similar scenario to [Zn 2 Cp* 2 ] may be expected for the so far unknown [Mg 2 Cp* 2 ] molecule with its strong MgÀMg s bond, [43] similar to that of Mg 2 Cl 2 , which has a bond strength of about 190 kJ mol À1 as determined experimentally. [44] In summary, the hindered decomposition of 1, which has Al À Al bonds of medium strength ( % 30 kJ mol À1 ) and the spontaneous decomposition of 2 have been outstanding, lucky discoveries that began the investigation presented herein. They shed light on three fundamental questions: 1) what kind of low-valent metastable organometallic compounds can be isolated; 2) what is the influence of metalloid clusters during the decomposition of organometallic compounds via a barrier; and 3) are metalloid clusters important snapshots for the nucleation during the crystallization of metals?…”

A Dimeric Magnesium(I) Compound as a Facile Two‐Center/Two‐Electron Reductant

“…Of these, Grignard reagents are undoubtedly the most important and have been utilized in innumerable synthetic transformations. [3] In addition, the reactions of the MgCl 2 C À radical with several ketones have been studied in the gas phase by mass spectrometry, and SET products were identified. Other magnesium reagents that can act as one-electron reductants include Mg/MgI 2 mixtures, which have been proposed to be in equilibrium with univalent magnesium, MgIC, in organic solutions.…”

“…[2] Although this species has not been characterized in solution, elegant recent work by Schnöckel, Henke, and Köppe has led to the spectroscopic characterization of related MgClC and Mg 2 Cl 2 in a solid inertgas matrix. [3] In addition, the reactions of the MgCl 2 C À radical with several ketones have been studied in the gas phase by mass spectrometry, and SET products were identified. [4] In late 2007, the first "bottleable" magnesium(I) compounds, [LMgMgL] (L = [(ArN) 2 CNiPr 2 ] À , Priso À (1) or [(ArNCMe) 2 CH] À , nacnac À (2; Scheme 1); Ar = 2,6-iPr 2 C 6 H 3 ), were reported.…”

“…[7] Treatment of these adducts with CyN=C=NCy led to no reaction, presumably because their magnesium centers were blocked towards coordination by the carbodiimide. Considering that magnesium(I) species have often been implicated as intermediates in substrate reductions involving organometallic or inorganic magnesium reagents, [1][2][3][4] it seemed that a systematic study of the reactivity of 2 towards unsaturated compounds would be of great interest to organic and organometallic chemists. Herein, we report preliminary results towards this end, which show that 2 acts as a facile two-center/two-electron reductant, yielding novel doubly reduced, C À C-or N À N-coupled products.…”