Addition of CO2 (1 bar) to a solution of 2a in C6D6 at room temperature results in an immediate colour change from pale red-orange to light orange. The new species formed, 3a, shows a sharp formate 1 H resonance at δH = 9.06 ppm. Analogous reactivity was achieved using t BuNCO (1.1 equiv.) to form aluminium formimidate 3b. In contrast, reaction of 1 with the same substrates leads to cycloaddition across the metal-metal bond to form 4a-b respectively. 4a-b feature a characteristic mutually coupled doublet (2P) and triplet (1P) resonance in their 31 P NMR spectra. In the solid state, the Fe-Al bond distances of 3a-b are very similar to 2a (3a: 2.3709(12) Å, fsr = 0.98; 3b: 2.3860(7) Å, fsr = 0.99).These compounds now show two distinct C=O and C=N vibrations in their IR spectra (3a: C=O: υ = 1841 cm -1 , OC=O: υ = 1670 cm -1 ; 3b: C=O: υ = 1841 cm -1 , OC=N: υ = 1632 cm -1 ). 4a-b also have a single characteristic C=N vibration (4a: υ = 1722 cm -1 ; 4b: υ = 1715 cm -1 ). The structures of 4a-b are largely similar to other cycloaddition products of this system. For example, 4b features an elongated metal-metal bond (4b: 2.3946(9) Å, fsr = 0.99) compared with that of 1, as well as a C-O and N=C bonds approaching the lengths for single and double bonds, respectively. b Range corresponds to the two independent molecules in the asymmetric unit.