Ru-catalyzed hydrogenation of gaseous CO₂ in the presence of Lys^a.

Entry	Cat. [μmol, ppm]	Formateb [mmol]	% Yieldc (TON)d
1	Ru-1 [2.0, 400]	4.37	87 (2187)
2	Ru-1 [0.2, 40]	3.89	78 (19 440)
3	Ru-1 [0.02, 4]	3.95	79 (197 559)
4	Ru-2 [0.02, 4]	4.24	85 (212 139)
5	Ru-2 [0.01, 2]	1.48	30 (147 906)
6e	Ru-1 [0.02, 4]	2.77	55 (138 510)
7e	Ru-2 [0.02, 4]	2.90	58 (144 990)
8e	Ru-3 [0.02, 4]	0.29	6 (14 580)
9e	Ru-4 [0.02, 4]	2.35	47 (117 450)
10e	Fe-1 [0.02, 4]	n.d.	—

^aConditions: catalyst, Lys (5.0 mmol), H₂O (5.0 mL), THF (5.0 mL), CO₂ (20 bar), H₂ (60 bar), 145 °C, 12 h.

^bDetermined by ¹H NMR with DMF (250 μL, 3.24 mmol) as internal standard.

^cCalculated by formate [mmol]/Lys [mmol].

^dCalculated by formate [mmol]/catalyst [mmol].

^e3 h. n.d. = not detectable. Experiments were performed at least twice; average values are used (st. dev. < 10%).