Accessing Stable Magnesium Acyl Compounds: Reductive Cleavage of Esters by Magnesium(I) Dimers

Abstract

The first examples of magnesium acyls, [(Nacnac)Mg{μ-C(Ph)O}(μ-OR)Mg(Nacnac)] (R=Me, tBu or Ph; Nacnac=[HC(MeCNAr) ] ; Ar=C H Me -2,4,6 ( Nacnac), C H Et -2,6 ( Nacnac), C H iPr -2,6 ( Nacnac)), have been prepared by reductive cleavage of a series of esters using dimeric magnesium(I) reducing agents, [{(Nacnac)Mg} ]. Crystallographic studies reveal the complexes to be dimeric, being bridged by both phenyl-acyl and alkoxide/aryloxide fragments. The crystal structures, combined with results of spectroscopic and computational studies suggest that the nature of the acyl ligands within these complexes should be viewed as lying somewhere between anionic umpolung acyl and oxo-carbene. However, reactions of the acyl complexes with a variety of organic electrophiles did not provide evidence of umpolung acyl reactivity. A number of attempts to prepare alkoxide free magnesium acyls were carried out, and while these were unsuccessful, they did lead to unusual products, the crystallographic and spectroscopic details of which are discussed.

N-Heterocyclic Carbene-Supported Aryl- and Alk- oxides of Beryllium and Magnesium

“…The carbene C−Be bond (1.797 Å) falls within the range of known carbene C−Be bond distances [50,53,54]. 17; O2−Be1−C1: 112.66 (15); O1−Be1−C1: 124.99 (17).…”

“…The carbene C−Be bond length is 1.855(4) Å, which is slightly longer than the starting material 1. The Be−O bond distances (1.621(4) Å and 1.641(4) Å ) are within the range of the 17; O2−Be1−C1: 112.66 (15); O1−Be1−C1: 124.99 (17).…”

“…The beryllium is centered in a distorted trigonal planar geometry, with the largest angle being O1−Be1−C1 at 124.99 17 2; N2−C4: 1.391(2); C2−C4: 1.362 (3). O2−Be1−O1: 122.34 (17); O2−Be1−C1: 112.66 (15); O1−Be1−C1: 124.99 (17).…”

“…Fedushkin synthesized MgO t Bu dimer stabilized by 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene [16]. Recently, Jones reported a series of NacNac-Mg acyl dimers bridged by O t Bu groups [17].…”

Bis(4‐methylbenzoxazol‐2‐yl)methanide in s‐Block Metal Coordination

“…[3][4][5] Despite the fact that bis(heterocyclo)methane ligands could act as a suitable platform for transition metal complexes because of their ability to behave as both, neutral and monoanionic ligands, [4] they have attracted very little attention in the field of maingroup coordination chemistry over the last three decades. [6] We embarked on extending the main-group chemistry, fired by the ubiquitous -diketiminate ligand [7][8][9][10][11][12][13][14] and its derivatives, to related bis(heterocyclo)methane and amine ligand systems. Starting from dipyridylmethane and -methanides [15][16][17][18] (A in Scheme 1) we extended the ligand class to the dipyridylamides, -phosphanides, and -arsenides (B).…”