Table 2.

Comparison of Deviations from Experiment and Mean Absolute Deviations (MAD) of Selected Calculated Average Bond Distances (Å) of the Fe₄S₄ Structures of this Study^a

		Expt.	OLYP	OPBE	PW91	BP86	B3LYP	B3LYP*	B3LYPb	B3LYP*b
[Fe4S4(SPh)4]2−	Fe–Fe	2.736	−0.012	−0.075	−0.066	−0.052	n/ac	n/ac	+0.144	+0.147
	Fe–S	2.286	+0.022	−0.017	−0.014	−0.007			+0.071	+0.075
[Fe4S4(OPh)4]2−	Fe–Fe	2.753	+0.017	−0.031	−0.051	−0.037	+0.205	+0.157	+0.150	+0.153
	Fe–S	2.294	+0.028	−0.010	−0.008	−0.002	+0.076	+0.062	+0.071	+0.076
[Fe4S4(SPh)2Cl2]2−	Fe–Fe	2.745	+0.010	−0.071	−0.060	−0.043	n/ac	+0.127	+0.155	+0.110
	Fe–S	2.278	+0.029	−0.011	−0.007	−0.001		+0.066	+0.080	+0.033
[Fe4S4(OPh)2Cl2]2−	Fe–Fe	2.766	+0.005	−0.061	−0.060	−0.001	+0.206	+0.133	+0.159	+0.155
	Fe–S	2.285	+0.028	−0.007	−0.005	+0.001	+0.084	+0.063	+0.079	+0.080
[Fe4S4Cl4]2−	Fe–Fe	2.700	+0.005	−0.072	−0.063	−0.049	+0.159	+0.114	+0.130	+0.126
	Fe–S	2.289	+0.017	+0.017	−0.014	−0.009	+0.064	+0.051	+0.063	+0.066
[Fe4S4(SCH2CO2Et)4]2−	Fe–Fe	2.754	−0.008	−0.093	−0.084	−0.066	n/ac	n/ac	+0.116	+0.117
	Fe–S	2.303	+0.018	−0.015	−0.015	−0.013			+0.098	+0.077
[Fe4(NO)4(μ3-S)4]	Fe–Fe	2.651	−0.016	−0.097	−0.049	−0.045	+0.208	+0.131	+0.307	+0.298
	Fe–S	2.217	−0.010	−0.064	−0.038	−0.034	+0.094	+0.069	+0.143	+0.145
[Fe4(NO)4(μ3-S)4] −	Fe–Fe	2.688	+0.015	−0.080	−0.039	−0.031	+0.208	+0.151	+0.232	+0.229
	Fe–S	2.231	+0.008	−0.051	−0.032	−0.027	+0.107	+0.083	+0.127	+0.129
MAD (Fe–Fe)			0.011	0.073	0.059	0.041	0.197	0.136	0.174	0.167
MAD (Fe–S)			0.020	0.023	0.017	0.012	0.085	0.066	0.092	0.085

^aCalculated values reported as deviations from experiment. Unless otherwise noted, all values are calculated at the OLYP/STO-TZP COSMO level of theory in ADF.

^bCalculated with ORCA using COSMO in combination with a CP(PPP) basis set on Fe and a TZVP basis set on the remaining atoms.

^cGeometry is not available at this level of theory. The OLYP/STO-TZP COSMO geometry is used instead. See Computational Methods section for details.