Table 4.

Catalytic systems, major products, maximum FEs, and mechanisms of Fe 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		R=Ph, C6F5, pyren‐1‐yl, meso‐thien‐2‐yl, meso‐5‐methylthien‐2‐yl	CO/H2O HCO2 −	100 [160d] 72[a] [164]	ETM	comp.[ 160f , 165 ]	DFT	FeII: [ 160a , 160d , 160g , 164 ] FeIII:[b] [ 160b , 160e , 160f , 160h , 160i , 160j , 162 , 166 ]
1b		R1=R2=CO2Me, NHCOtBu, NHCOC6H4CH2MeIm+, NMe3 +, trFc2, trCO2Me, tr‐4‐tBu R1∩R1/R2∩R2=NHCO(CH2)10CONH, NHCO(CH2)10ImCONH	CO/H2O	100 [160h]	ETM	comp.[ 160f , 166f ]	DFT	FeII: [166f] FeIII: [ 160f , 160h , 166a , 166b , 166c , 166e ]
1c		–	CO/H2O	65	ETM	comp.	DFT	[160f]
1d		R=Ph, pyren‐1‐yl, CO2Me, NMe3 +, SO3 −	CO/H2O H2	100 [160e] 84 [160f]	ETM	comp. [160f]	DFT	FeII: [167] FeIII:[ 160e , 160f , 160h , 160j , 168 ]
1e		R1=CH2CONHC6H3(CF3)2, NHCOCH2C6H3(CF3)2, NHCONH‐Fe‐TPP, OMe R2=H, NH2, OMe Y=CH, N	CO/H2O CH4	90 [169] 41 [163]	ETM	comp. [167]	DFT	[ 163 , 167 , 169 , 170 ]
1f		R=OH, OMe	CO/H2O	94 [160c]	ETM	prop.	n.a.	FeII: [160g] FeIII:[ 160c , 160e ]
1g		R=propylpyrene	CO/H2O	97	n.a.	n.a.	n.a.	[171]
1h		R=CH2CONHC6H3(CF3)2, NHCOCH2C6H3(CF3)2, OH	CO/H2O	96 [172]	ETM	comp. [167]	DFT	FeII: [167] FeIII: [172]
1i		R1=3,4,5‐trimethoxyphenyl R2=CNHNH2, C6H4OH, C6H4SO3H	CO/H2O	96	ETM	comp.	DFT	[173]
1j		R1=3,4,5‐trimethoxyphenyl R2=3,4,5‐trimethoxyphenyl	CO/H2O	100	ETM	prop.	n.a.	[174]
1k		R=Ph, Me3C6H2, C6F5, 2,6‐Cl2C6H3, 2,6‐F2C6H3	CO/H2O	92 [175]	ETM	prop. [175]	n.a.	[ 175 , 176 ]
2a		L=MeIm	CO/H2O HCO2 − C2O4 2−	42 74 11	ETM (CO/C2O4 2−) ETH (HCO2 −)	exp. prop.	IL,[c] IR‐SEC	[177]
2b		R1=Me, tBu R2=tBu, OH, OMe R3=tBu, OMe X=–, Cl	HCO2H H2	85 [178] 60 [178]	ETH	exp. [179] comp. [179]	IR‐SEC	[ 178 , 179 ]
							DFT
3	[Fe4Y(CO)11(L)]n‐	L=CO, PPh3, PPh2(CH2)2OH, PPh2C6H4tr n=1, 2 Y=C, N	HCO2 − H2	96±2 [180] 96±6 [181]	ETH	exp. [180]	IL, IR‐SEC, XRD	[ 180 , 181 , 182 ]
4		–	HCO2 −	80	ETM	comp.	DFT	[59]
5	[Fe(N∩N)3]2+	N∩N=bpy, phen	CO/CO3 2−	n.a.	outer sphere	exp. comp.	UV/Vis‐SEC DFT	[183]
6	[Fe(tpy)2]2+	–	CO/CO3 2−	n.a.	outer sphere	exp. comp.	UV/Vis‐SEC DFT	[183]
7		R=Me, tBu Y=CH2, C2H4, O	CO/H2O	98 [161b]	ETM	exp. comp.	chem. isol., IR‐SEC DFT	[161]
8		–	CO/H2O	48	ETM	exp. comp.	IR‐, UV/Vis‐SEC DFT	[184]
9		L=H2O, MeCN, CF3SO3 − n=0, 1, 2 R=H, NHEt, NEt2, OH, OMe	CO/H2O	81 [185]	ETM	comp. [186]	DFT	[ 185 , 186 ]
10	[Fe(N2)(dmpe)2]	–	CO/CO3 2−	n.a.	ETM	exp.	IL, NMR, XRD	[187]
11		L=MeCN R=Ph	HCO2 − MeOH[d]	97 69	ETH	exp.	IL, NMR	[188]

[a] After addition of Et₃N. [b] The metal is coordinated by an axial halide ligand. [c] IL=isotopic labeling. [d] After addition of NHEt₂.