Table 5.

Catalytic systems, major products, maximum FEs, and mechanisms of Ru and Os complexes in electrochemical CO₂ reduction (n.a.=not available, prop.=proposal, comp.=computational investigation, exp.=experimental evidence).

Entry	Cat. system	Substitution	Major product	Max. FE (%)	Mechanism	Basis	Method	Ref.
1a	[Ru(bpy)(CO)mLo]n+	L=Cp, CO2Me, py‐CO2 −, qui, Cl m=0, 1, 2; n=0, 1, 2; o=1, 2	CO/CO3 2− CO/H2O H3CCOCH3 [a]	97 [190] n.a. 70 [194]	ETM	comp. [197]	DFT	[189, 190, 194, 197, 198]
1b		R1=Me, tBu, pyrrol‐1‐ylethyl, CO2‐iPr, pyrrolylpropyl carbonate R2=Me, tBu, CO2‐iPr, pyrrolylpropyl carbonate	CO/H2O HCO2H	100 [189b] 97 [94b]	ETM (CO) [199] ETH (HCO2H) [199]	prop.	n.a.	[94b, 189b, 198a]
1c		R=Mes, CH2NEt2	CO/H2O HCO2H	95 [67] 9 [136]	ETH	exp.	IR‐SEC	[ 67 , 136 ]
1d	[Ru(di‐R‐bpy)2(CO)mLo]n+	L=H, EtOH, qui, 1,8‐napy, Cl m=0, 1, 2; n=0, 1, 2; o=0, 1, 2 R=H, CO2H	CO/CO3 2− CO/H2O HCO2 − H3CCOCH3 DMF[b] H2	78 [195] 88 [200] 84 [201] 16 [195] 21 [196] 51 [201]	ETM ETH	exp. [196] comp. [202] exp. [203]	IR, NMR [196] DFT IR, NMR, UV/Vis	[195, 196, 200–204]
2a	[Ru(tri‐R1‐tpy)L]n+	L=H2O, CH3CN, CO, di‐R2‐bpy, phen‐CO2 −, dmphen,[c] Mebim‐py,[d] pbn, 8‐(diphenylphosphanyl)‐qui, Cl n=1, 2 R1=H, tBu, NO2 R2=H, Me, tBu, OMe	CO/CO3 2− CO/H2O HCO2 −	95 [205] 85 [206] 42 [191]	ETM	comp. [207]	DFT	[191, 192, 205–208]
2b	[Ru(4‘‐R‐tpy)(L)(X)]n+	L=bpy, tpy n=1, 2 R=H, 4‐(tert‐butyl‐phenyl)‐1H‐1,2,3‐triazol‐4‐yl X= –, Cl	CO/H2O HCO2 − H2	38 10 33	ETM	prop.	n.a.	[209]
2c		R=PO3H2, PO3Et2	CO/H2O	63	ETM	prop.	n.a.	[210]
2d		N∩N∩N=tpy	CO/CO3 2−	22	n.a.	n.a.	n.a.	[211]
2e		Y=CH, NMe	CO/CO3 2−	35	ETM	exp.	IR‐SEC	[212]
3		–	CO/CO3 2−	97	ETM	comp.	DFT	[213]
4a		Y=CH, N	HCO2 − H2CO MeOH	n.a.	ETH	exp.	IR‐SEC	[214]
4b		–	CO/CO3 2−	96	ETM	comp.	DFT	[215]
5		L=bpy	HCO2 − C2O4 2−	90 70	ETM	exp.	IL, IR‐SEC	[216]
6a		R=H, Me	CO/H2O HCO2 − H2	19 25 24	ETM (CO) ETH (HCO2 −)	prop.	n.a.	[217]
6b		X= –, Cl	CO/H2O HCO2 − H2	73 40 27	ETM (CO) ETH (HCO2 −)	prop.	n.a.	[217]
6c		R=C6H4OMe	CO/CO3 2−	53	ETM	comp.	DFT	[218]
6d		R=C6H4OMe	CO/CO3 2−	25	ETM	comp.	DFT	[218]
7	[Os(CO)(di‐R‐bpy)(L)Cl2]	R=H, CH3, tBu, CO2‐iPr L=CO, PrCN, Cl	CO/CO3 2− HCO2 −	60 [219] 48 [219]	n.a.	n.a.	n.a.	[ 219 , 220 ]
8	[Os(CO)(bpy)2H]+	–	CO/H2O HCO2 −	90 [221] 25 [221]	ETM	exp.	IL	[ 221 , 222 ]

[a] After addition of (CH₃)₄NBF₄. [b] After addition of HNMe₂. [c] 2,9‐Dimethyl‐1,10‐phenanthroline. [d] 1‐Methylbenzimidazol‐2‐ylidene‐3‐(2′‐pyridine).