μ-Methyl­ene-bis­[di­bromido(diethyl ether-κO)aluminium(III)]: crystal structure and chemical exchange in solution

In the title compound, [Al(2)Br(4)(CH(2))(C(4)H(10)O)(2)], the mol­ecule lies on a crystallographic twofold axis passing through the bridging C atom. Each Al(III) atom is four-coordinate, being bonded to two bromide ions, bridging the CH(2) group as well as the oxygen atom of a diethyl ether ligand in a slightly distorted tetra­hedral arrangement with angles ranging from 101.52 (8) to 116.44 (5)°. The Al—CH(2)—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 inter­actions, characterized as R (2) (2)(12) rings, link the mol­ecules 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 mol­ecules from either or both Al atoms can dissociate, and would be expected to rapidly exchange, and this is supported by NMR data.