Advances in organometallic synthesis with mechanochemical methods

Abstract

Solvent-based syntheses have long been normative in all areas of chemistry, although mechanochemical methods (specifically grinding and milling) have been used to good effect for decades in organic, and to a lesser but growing extent, inorganic coordination chemistry. Organometallic synthesis, in contrast, represents a relatively underdeveloped area for mechanochemical research, and the potential benefits are considerable. From access to new classes of unsolvated complexes, to control over stoichiometries that have not been observed in solution routes, mechanochemical (or 'M-chem') approaches have much to offer the synthetic chemist. It has already become clear that removing the solvent from an organometallic reaction can change reaction pathways considerably, so that prediction of the outcome is not always straightforward. This Perspective reviews recent developments in the field, and describes equipment that can be used in organometallic synthesis. Synthetic chemists are encouraged to add mechanochemical methods to their repertoire in the search for new and highly reactive metal complexes and novel types of organometallic transformations.

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

“…We describe herein the impact of the addition of variable amounts of PEG, PEG chain length and end terminal groups, for the preparation of diverse 3,5-disubstituted hydantoins from α-amino methyl esters 1 , via an in situ intramolecular cyclization reaction of the ureido derivative B , which was obtained from N -carbamoylimidazole activated amino ester derivative A by reaction with various amines [9–11] (Scheme 1). Hanusa’s formalism was used to represent the reaction activated by mechanochemical energy [12]. …”

Hydroformylation of Alkenes in a Planetary Ball Mill: From Additive‐Controlled Reactivity to Supramolecular Control of Regioselectivity

“…To begin with, we demonstrated that the hydrido-Rh precursor could be synthesized under mechanochemical conditions.A sd escribed for many other organometallic complexes, [23] ball milling allowed for the straightforward synthesis of the HRh(CO)(PPh 3 ) 3 complex, as confirmed on the basis of 1 Ha nd 31 PNMR spectroscopy (Figure 2a nd Figure 3). Thehydrido-Rh species was identified at À9.8 ppm on the 1 HNMR spectrum and the Rh-P bond was revealed by the doublet at 40.0 ppm ( 1 J Rh-P = 154.9 Hz) in the 31 PNMR spectrum.…”

Symmetric Assembly of a Sterically Encumbered Allyl Complex: Mechanochemical and Solution Synthesis of the Tris(allyl)beryllate, K[BeA′3] (A′ = 1,3-(SiMe3)2C3H3)

“…The coordinated ether in BeA' 2 ·OEt 2 proved impossible to remove without destroying the complex [11], and thus we investigated mechanochemical methods of synthesis as a means to bypass the use of ethereal solvents [14]. As detailed below, an unsolvated neutral complex was not isolated via this route, and the beryllate anion that was produced instead has structural parallels with previously described -ate complexes of Zn [15] and Sn [16].…”

“…The symbol for mechanical milling has been proposed in ref. [14]; b rystallized; limiting reagent taken into account; c Ref. [11]; d Products were observed with 9 Be NMR, ere not isolated.…”