While the two-electron reduction of CO by a number of main group compounds to give systems of the type [CnOn] 2-has been reported, four-electron processes yielding the topologically linear [C4O4] 4-fragment have more limited literature precedent. We were therefore keen to probe the mechanism of this transformation through both experimental and quantum chemical methods. As a key mechanistic principle, we first set out to determine whether the dimeric nature of the aluminyl reagent, [1-K]2, is critical in driving the formation of the (four-electron reduction) product, [C4O4] 4-.