The dimerisation of formyl intermediates has been investigated computationally for other systems. Mechanisms toward magnesium ethenediolate 31 through bis(formyl) intermediates were explored computationally (Scheme 12a). Addition of CO to observed bridging formyl hydride complex 30 to give either cis-(60) or trans-(61) bis(formyl) intermediates were explored computationally. In both cases, the authors note no route to the observed ethenediolate 31 and higher energy barriers compared to the hydride insertion mechanism discussed in Scheme 9. In our study on ethenediolate formation at Cr---Mg complexes, DFT calculations suggest that direct dimerisation of a putative bis(formyl) intermediate ( ) is a high energy process (G° > 50 kcalmol -1 ), strongly suggesting that this mechanism is not in operation (Scheme 12b). Scheme 12. Reported DFT calculated pathways with (bis)formyl dimerisation mechanism for ethenediolate formation.