μ-Methyl-ene-bis-[di-bromido(diethyl ether-κO)aluminium(III)]: crystal structure and chemical exchange in solution.

Ray J Butcher,Andrew P Purdy

doi:10.1107/s2056989021005302

Abstract

In the title compound, [Al2Br4(CH2)(C4H10O)2], the mol-ecule lies on a crystallographic twofold axis passing through the bridging C atom. Each AlIII atom is four-coordinate, being bonded to two bromide ions, bridging the CH2 group as well as the oxygen atom of a diethyl ether ligand in a slightly distorted tetra-hedral arrangement with angles ranging from 101.52 (8) to 116.44 (5)°. The Al-CH2-Al angle, 118.4 (2)°, is the smallest observed for a structure where this moiety is not part of a ring. In the crystal, weak C-H⋯Br inter-actions, characterized as R 2 2(12) rings, link the mol-ecules into ribbons in the [101] direction. The title compound is monomeric and coordinatively saturated in the solid state, as each aluminum is four-coordinate, but in solution the ether mol-ecules from either or both Al atoms can dissociate, and would be expected to rapidly exchange, and this is supported by NMR data.

Highlights

In the title compound, [Al2Br4(CH2)(C4H10O)2], the molecule lies on a crystallographic twofold axis passing through the bridging C atom
There is great current interest in the chemistry of reduced aluminum (Klemp et al, 2001, Bonyhady et al, 2018) and aluminum carbon clusters (Stasch et al, 2002; Uhl & Roesky, 2002; Kumar et al, 2004) as well as aluminum– carbon nanoparticles (Diaz-Droguett et al, 2020) because of their interesting structural chemistry and many theoretical studies have been carried out on potential derivatives and as analogs of the better known boron examples (Attia et al, 2017). This has lead to a renaissance in the chemistry of aluminum (Roesky, 2004). In view of this chemistry, there is a need for prepared precursors for the synthesis of these reduced aluminum and carbaalane clusters, and this is the motivation behind preparing organometallics with two or more Al atoms on a carbon atom
There are ten instances (BELLAH, BELLEL, BELLIP, BELLOW, BELLUP (Uhl et al, 2012a); JEZFID (Layh & Uhl, 1990); JUWMOD (Uhl et al, 1993); PENSEI (Uhl et al, 2012b); WOZJUQ, WOZKAX (Knabel et al, 2002) where the metrical parameters of the Al– CH2–Al fragment are not influenced by being part of a ring

Summary

Chemical context

There is great current interest in the chemistry of reduced aluminum (Klemp et al, 2001, Bonyhady et al, 2018) and aluminum carbon (carbaalanes) clusters (Stasch et al, 2002; Uhl & Roesky, 2002; Kumar et al, 2004) as well as aluminum– carbon nanoparticles (Diaz-Droguett et al, 2020) because of their interesting structural chemistry and many theoretical studies have been carried out on potential derivatives and as analogs of the better known boron examples (Attia et al, 2017).

Structural commentary

Supramolecular features

Synthesis and crystallization

Findings

Database survey