To confirm this, we compared the C=O/C=C substrate preference using cooperative and non-cooperative Mn(I)-CNP counterparts: Mn-5 and Mn-7, respectively. As depicted in Figure , the N-H methylation in Mn-CNPs completely suppressed the ketone hydrogenation, but enabled the transposition of allylbenzene and even the hydrogenation of styrene. Notably, Mn-5 with the cooperative N-H functionality was inactive for either of C=C bond transformation paths. The displayed selectivity prompted a further mechanistic analysis of Mn-7 operation in the course of reaction. As a first step to the mechanistic investigation we conducted cross reactivity experiments with deuterium-labelled 11-d and non-deuterated 2a (Scheme 2). We observed both the intramolecular scrambling as well as the intermolecular crossover of the deuterium label between the olefin products. This is indicative of transposition proceeding via either alkyl or hydrogen atom transfer mechanisms, because the cross reactivity between deuterated and label-free olefins should involve a Mn-H species as a transfer medium. Together with the previous observation that KHBEt 3 activation was necessary for the catalytic reactivity (Table , entry 8), labelling data implies that the formation of Mn hydride must take place in the course of reaction. To verify this we monitored the KBHEt 3 activation of pre-catalysts Mn-7 followed by the catalytic turnover using NMR and IR spectroscopy.