We previously reported that the reaction of 1 with 4-methylpyridine in C6D6 resulted in the formation of 2 due to metalation of a sp 2 C-H bond (Figure ). We can now conclude that, 2 is only the kinetic product of this reaction. Heating a C 6 D 6 solution of 2 to 80 °C for 18 h, resulted in conversion into the thermodynamic product 3. 3 exhibits a sharp singlet resonance in the 31 P{ H} NMR spectrum at δP = 29.0 ppm as well as a broadened quartet resonance at δH = -15.57 ppm in the 1 H NMR spectrum. 3 clearly possesses a lower symmetry than 2 in solution. Most characteristic is the appearance of two distinct C{ 1 H} resonances at δc = 145.5 and 62.0 ppm for the quaternary carbons of the β-diketiminate, indicative for the presence one sp 2 and one sp 3 C-N moiety, respectively. Compound 3 is proposed to arise from C-to N-rearrangement of the pyridyl anion followed by a nucleophilic attack on one of the imine positions of the β-diketiminate ligand (Figure ). Examples for this kind of reactivity are known but rare. Reaction of 1 with 3,4-dimethylpyridine under the same conditions gave a mixture of two products in a 4:1 ratio (Figure ). The major species 4 originated from C-H activation of the C 6 -position of the substrate. The minor species 5 most likely results from the C-H activation of the C 2 -position followed by intramolecular nucleophilic attack on the β-diketiminate ligand. The ratio of 4 and 5 does not change over time suggesting that these species are not in equilibrium. Similarly, reaction of 1 with 3,5-dimethylpyridine in C6D6 at 25 °C exclusively led to the formation of 6, the product of nucleophilic addition to the ligand (Figure ). Contrary to the observed site selectivity in the present case, the reaction of 4-methyl and 3,5-dimethylpyridine with the parent Al(I) complex results in activation of remote CH or CH3 groups in the para-positions of these substrates. 21 This provides a further example how heterobimetallic cooperativity can affect the reactivity or selectivity of a main group species. Further variation of the substrate revealed that 1 can react selectively at sp 3 C-H bonds of pyridines in the presence of sp 2 C-H bonds. Hence, addition of 2-methylpyridine to 1 resulted in deprotonation of the CH3 group to afford 7 in >95 % NMR yield (Figure ). In the 1 H NMR spectrum of 7, the new CH2 group exhibits diastereotopic protons characterised by two doublets at δH = 3.70 and 3.06 ppm with a mutual coupling constant of JH-H = 17.4 Hz. The 13 C{ 1 H} NMR shows a resonance at δC = 59.4 ppm for the quaternary sp 3 carbon created upon nucleophilic addition of the pyridyl group to the β-diketiminate ligand. Heating a C6D6 solution of 7 to 80 °C for 18 h leads to the formation of 8 in which the deprotonated sidearm of the 2-methylpyridine substrate is bound to the aluminium centre.