Table 1.

Interatomic distances in optimized FeMo-co^N for selected oxidation states. Experimental distances are given for the average of four FeMo-co structures from the crystal structure² along with those from two EXAFS studies.^{6, 72} Superscripts (Fe) and (Mo) refer to the [4Fe-3S] and [Mo-3Fe-3S] subclusters, respectively; (b) denotes the bridging sulfides. HC(O_hydroxyl) refers to the deprotonated (O⁻) or protonated (OH) hydroxyl group of the homocitrate ligand.

	calculated distances (Å)									experiment
	2FeII-5FeIII-X				4FeII-3FeIII-X					Ref. 2, 6, 72
X =	C4−		N3−		C4−		N3−		O2−
HC(Ohydroxyl)	O−	OH	O−	OH	O−	OH	O−	OH	O−
S(Cys)-Fe	2.22	2.20	2.20	2.18	2.30	2.28	2.27	2.26	2.25	2.27
Fe-S(Fe)	2.26	2.25	2.25	2.25	2.32	2.32	2.31	2.31	2.32	2.28
Fe…Fe(Fe)	2.63	2.62	2.63	2.63	2.73	2.72	2.73	2.72	2.73	2.66
S(Fe)-Fe(Fe)	2.28	2.27	2.28	2.27	2.32	2.31	2.31	2.30	2.30	2.27
Fe(Fe)-S(b)	2.19	2.19	2.19	2.19	2.24	2.23	2.23	2.23	2.22	2.23
Fe(Fe)…Fe(Fe)	2.65	2.64	2.69	2.68	2.66	2.65	2.67	2.67	2.80	2.65
Fe(Fe)-X	2.01	2.00	2.03	2.03	2.01	2.00	2.01	2.01	2.10	1.98
Fe(Fe)…Fe(Mo)	2.59	2.57	2.58	2.57	2.62	2.61	2.62	2.61	2.76	2.59
Fe(Mo)…Fe(Mo)	2.66	2.66	2.68	2.68	2.61	2.60	2.63	2.63	2.74	2.61
Fe(Mo)-S(b)	2.20	2.19	2.20	2.18	2.24	2.22	2.23	2.21	2.23	2.22
Fe(Mo)-X	2.00	2.00	2.00	2.00	2.01	2.00	2.02	2.01	2.12	2.02
Fe(Mo)…Mo	2.76	2.72	2.78	2.74	2.74	2.70	2.75	2.71	2.76	2.69
S(Mo)-Fe(Mo)	2.28	2.28	2.29	2.29	2.29	2.28	2.29	2.28	2.28	2.23
S(Mo)-Mo	2.40	2.37	2.40	2.37	2.39	2.37	2.40	2.38	2.41	2.35
Mo-N(His)	2.25	2.22	2.24	2.21	2.26	2.24	2.26	2.22	2.24	2.30
Mo-Ocarboxyl	2.12	2.11	2.10	2.08	2.16	2.16	2.14	2.13	2.11	2.18
Mo-Ohydroxyl	2.01	2.22	1.98	2.20	2.05	2.26	2.03	2.23	2.01	2.20
avg. Mo-O/N	2.13	2.19	2.11	2.16	2.16	2.22	2.14	2.19	2.12	2.23
Fe…Mo	7.02	6.94	7.02	6.95	7.17	7.11	7.17	7.10	7.22	7.00
avg. error	−0.01	−0.02	−0.01	−0.01	0.02	0.02	0.02	0.02	0.05
RMS dev.	0.06	0.04	0.07	0.05	0.06	0.04	0.07	0.04	0.11
core avg. error	0.01	0.00	0.02	0.01	0.03	0.02	0.03	0.02	0.07
core RMS dev.	0.04	0.03	0.05	0.04	0.04	0.03	0.04	0.03	0.09