Table 1.

The test set of compounds used for benchmarking in this work. The six-letter codes refer to the Cambridge Structural Database identifiers. The coupling constant J is given when known. The ligands are encoded as follows: BIPhMe = bis(1-methylamidazol-2-yl)phenylmethoxymethane, DTSQ = bis(dithiodithiosquarato-S,S′) dianion, Et-HPTB = N,N,N′,N′-tetrakis(N-ethyl-2-benzimidazolylmethyl)- 1,3-diaminopropane), ImH = imidazole, HB(mtda^R)₃ = tris(mercaptothiadiazolyl)borate, HBpz₃ = hydrotris-1-(pyrazolyl)borate, HO₂CAr^Mes = 2,6-bis(mesityl)benzoic acid, MBTHx = bis(N-methylbenzothiohydroxamato) anion, Me₃TACN = 1,4,7-trimethyl-1,4,7-triazacyclonane, OEP = dianion of octaethylporphyrin, OEP = dianion of trans-7,8-dihydro-octaethylporphyrin, Piv = pivalate, “S2” = 1,2-Benzenedithiolato-S,S′ dianion, TAML = tetra-amido macrocyclic ligand,¹⁰¹ TMEN = N,N,N′,N′-tetramethylethylenediamine, TMIP = tris(methylimidazol-2-yl)phosphine, TPA = tris(2-pyridylmethyl)amine, TTC = tetrachlorocatecholato-O,O′ dianion, XDK = acid anion of m-xylenediamine bis(Kemp’s triacid)-imide

No.	System	Code	Fe oxidation	Spin	δ, mm/s	|Δ E |, mm/s	J, cm−1	R-factor, %	Reference
1.	Fe2 (O2CH)2(BIPhMe)2	SISKOU	+2	0	1.26	2.56	~ 0	4.1	78
			+2		1.25	3.30
2.	Fe(HB(mtdaR)3)2	JOHCEP	+2	0	0.49	0.26	–	4.83	79
3.	Fe2 (OAc)2(TPA)22+	VUNMIA	+2	0	1.12	3.33	~ 1	4.7	80
4.	Fe2 (ImH)2(XDK)(O2CPh)2 (MeOH)	YUZKAF10	+2	0	1.35	3.04	−0.51	8	81
			+2		1.12	2.83
5.	Fe2 (py)2 (O2CArMes)4	XIGDIA	+2	0	1.14	3.23	30	5.44	82
6.	Fe(OEP)CO	YEQPOA	+2	0	0.27	1.84	–	2.85	83
7.	Fe(OEP)	DEDWUE	+2	1	0.63	2.55	–	7.2	84
8.	Fe(OEC)	BUYKUB10	+2	1	0.62	1.71	–	6	84
9.	Fe3 (SPh)6(CO)6	FATBOR	+2	2	1.00	2.00		3.9	85
			+2		0.10	0.22
10.	Fe2 (H2O)(O2CPh)4 (TMEN)2	VUPJUL	+2	2	1.25	3.11	small	4.4	86
			+2		1.26	2.70
11.	Fe2 (H2O)(OAc)4(TMEN)2	VUPJOF	+2	2	1.27	2.75	small	5.5	86
12.	$\text{Fe}{(\text{DTSQ})}_2^{2-}$	PTSQFE10	+2	2	0.67	4.01	5.5		87
13.	$\text{Fe}{(\text{SPh})}_4^{2-}$	PTHPFE10	+2	2	0.66	3.24	4.7		87
14.	Fe2 O(HBpz3)2(OAc)2	CACZIP10	+3	0	0.52	1.60	−121	4	88
15.	Fe2 (OH)(HBpz3)2(OAc)2	COCJIN10	+3	0	0.47	0.37	~ −17	4.8	93
16.	${\text{Fe}}_2(\text{OH}){({\text{O}}_2\text{P}{(\text{OPh})}_2)}_3{({\text{HBpz}}_3)}_2^{2+}$	PIMTAG	+3	0	0.44	0.44	~ minus;15	6.9	93
17.	${\text{Fe}}_2\text{O}{(\text{PiV})}_2{({\text{Me}}_3\text{TACN})}_2^{2+}$	ZOCPEM	+3	0	0.48	1.54	−111	6.6	89
18.	${\text{Fe}}_2{(\text{O})}_2{(6-{\text{Me}}_3-\text{TPA})}_2^{2+}$	YOCKAC	+3	0	0.50	1.93	54	6.5	90
19.	Fe2 (NO)2(Et-HPTB)(O2CPh)	RABHAD	+31	0	0.67	1.44	−23	8.5	91
20.	Fe2 (S-t-Bu)2 (NO)2	GIDKIN02	+3	0	0.15	0.90		2.11	92
21.	(Fe(Me3 TACN)(TTC))2O	YOHMOX	+3	0	0.46	1.41	−90	6.5	94
22.	${\text{Fe}}_2\text{O}{(\text{TMIP})}_2{(\text{OAc})}_2^{2+}$	JIGNUI	+3	0	0.52	1.61	−120	5.7	95
23.	$\text{Fe}(\text{OEP}){(4-{\text{NMe}}_2\text{Py})}_2^{2+}$	VOFLOR	+3	1/2	0.26	2.15	–	6.7	96
24.	Fe(S-t-Bu)3 NO	WEDXAF	+3	3/2	0.26	0.46	–	2.93	92
25.	FeCl5 (H2O)2−	VOCBAQ	+3	5/2	0.49	0.56	–	3.2	97
26.	$\text{Fe}{(\text{SEt})}_4^{-}$	CANDAW10	+3	5/2	0.25	0.62	–	5	98
27.	$\text{Fe}{(\text{NO})}_2{(\text{S}(p-\text{Me})\text{Ph})}_2^{-}$	SONMUE	+3	5/2	0.18	0.69	–	3.55	99
28.	FeCl(MBTHx)2	CELVEU	+3	5/2	0.43	0.98	–	3.8	100
29.	(Fe(TAML)2)2O−	KAJBIH	+4	0	−0.07	3.3	> 100	5.32	101
30.	Fe(PPh3)2(“S”)2	SOCVUB	+4	1	0.16	1.52	–	5.9	102
31.	Fe(PPh3)(“S2”)2	SOCWAI	+4	1	0.12	3.03	–	4.6	102