Table 1. DFT Calculated Zr–O Bond Lengths^a.

		terminal ligands		central ligands
I	CO–Zr	2.215	2.158	2.205	2.283
	NO–Zr	2.269	2.326	2.270	2.223
II	CO–Zr	2.220	2.167	2.205	2.291
	NO–Zr	2.266	2.298	2.263	2.218
III (ref 13)	CO–Zr	2.261	2.254	2.199	n/a
	NO–Zr	2.121	2.220	2.111	n/a
III	CO–Zr	2.277	2.284	2.211	n/a
	NO–Zr	2.142	2.249	2.144	n/a
IIIa	CO–Zr	2.262	2.281	2.237	n/a
	NO–Zr	2.197	2.142	2.188	n/a
IV	CO–Zr	2.347	2.362	2.442	n/a
	NO–Zr	2.367	2.229	2.417	n/a
Zr(1,2-HOPO)4	CO–Zr	2.222	2.222	2.212	2.212
	NO–Zr	2.252	2.252	2.242	2.242
Zr(hydroxamate)4 crystal (ref 35)	CO–Zr	2.172	2.196	2.163	2.199
	NO–Zr	2.215	2.233	2.189	2.178

^aAll bond lengths reported in Å. DFT calculations were performed using the Gaussian 09 program with CEP-121G as the basis set.