Table 2. Catalytic CO₂ Hydrogenation with 1 Using Different H₂/CO₂ Partial Pressure Ratios^a.

entry	1/DBU	pH2/pCO2 (bar)	TONb	yield (%)c
1	1/1000	50/25	1000	100
2	1/1000	60/20	1000	100
3	1/2000	50/25	540	26.8
4	1/5000	50/25	98	1.9
5	1/10 000	50/25	109	1.1

^aReaction conditions: catalyst 1, 1–10 μmol; DBU, 10 mmol; THF, 5.5 mL; H₂/CO₂ (2:1 or 3:1) pressure; 80 °C, 24 h.

^bTON = (mmol formate)/(mmol catalyst).

^cYield = [(mmol formate)/(mmol DBU)] × 100. The amount of formate was calculated from the integration of the corresponding ¹H NMR signal in D₂O against an internal standard (DMF). All experiments were repeated at least twice to check for reproducibility; average error, ca. 6%.