Figure SI.1 shows the reaction coordinate diagram of hydrogenation of acetophenone by the trans-Ru(H)2[(S)-XylBINAP][(S,S)-DPEN] catalyst (system 1a/2a) along each possible pathway [Q1 (R-alcohol), Q2 (S-alcohol), Q3 (S-alcohol) andQ4 (R-alcohol)], which reveals the energy ranking for the four reaction pathways: Q1 < Q2 < Q3 < Q4. For the system 1c/2a, we have therefore only considered the Q1 and Q2 pathways. This was based on the following considerations.
Figure SI.2 shows the orientations of acetophenone with respect to thetrans-Ru(H)2[(S)-XylBINAP][(S,S)-DPEN] (system 1a/2a)in the asymmetric hydrogenation of acetophenone along the Q1, Q2, Q3, and Q4 pathways.Comparing Q1 and Q4 pathways, which both generate the R-alcohol, we note that along Q4, the approach of ACP is hindered by the naphthyl and the phenyl rings of the diphosphine (see arrows in Figure SI.2). For Q1 there is not such kind of steric impediment when ACP approaches the catalyst. When we replace the xylyl group (system 1a/2a) by the phenyl group (system 1c/2a), it is plausible to expect that the approach of ACP along Q4 will be also hindered by the naphthyl and the phenyl rings, and consequently energetically less favourable than Q1. Comparing the Pre-INT, INT (intermediate) and TS (transition state) of the system 1a/2a along Q2 and Q3, which both generate the S-alcohol, we notice that along Q2, once the ACP rotates upright, there is enough space for ACP to approach the catalyst. However for Q3, the phenyl group of the diamine blocks the entrance of ACP, no matter if the phenyl R = –CH3 is in the meta positions (system 1a/2a), R = –CH3 is in para position (system 1b/2a), or R = H (system 1c/2a). Therefore, considering Q1 as the lowest energy pathway for the system 1c/2a seems also justifiable.
Figure SI.3 shows the orientation of ACP with the complexes 1a/2a, 1b/2a and 1c/2a before forming the most stableintermediate (Pre-INT), in the most stable intermediate (INT), transition state (TS), and product [Phenylenthanol+ 16e- Species] (PRO). The structures and orientation of ACP in these intermediates are similar for the three systems 1a/2a, 1b/2a and 1c/2a, which suggest that the energy ranking of the Q1, Q2, Q3 and Q4 (Q1<Q2<Q3<Q4.) should be maintained when considering the system 1c/2a.
Figure SI.1Reaction coordinate diagram of the hydrogenation of acetophenone by the Ru(H)2[(S)-XylBINAP][(S,S)-DPEN] catalyst along each possible pathway ( Q1, Q2, Q3, and Q4). Values werecomputed at the DFT/PBE level of theory. (Pre-INT stands for the second stable intermediate before reaching the most stable intermediate; INT stands for the most stable intermediate; TS stands for the transition state; PRO stands for Phenylethanol + 16e species)
Q1-(R) / Q2-(S) / Q3-(S) / Q4-(R)Pre-INT / / / /
INT / / ─ / / ─
TS / / / /
PRO / / / /
Figure SI.2The structuresin the Pre-INT, INT, TS and PROin the asymmetric hydrogenation of acetophenone catalysed by the trans-Ru(H)2[(S)-XylBINAP][(S,S)-DPEN] along the Q1, Q2, Q3 and Q4 pathways.
Path / Pre-INT / INT / TS / PRO1a/
2a / Q1 / / / /
1b/
2a / Q1 / / / /
1c/
2a / Q1 / / / /
1a/
2a / Q2 / / /
1b/
2a / Q2 / / /
1c/
2a / Q2 / / /
Figure SI.3The structures in the Pre-INT, INT, TS and PRO in the hydrogenation of acetophenone (ACP) along the Q1 and Q2 in [ACP + 1a/2a], [ACP + 1b/2a], and [ACP + 1c/2a].
1