Selected average bond distances (Å) determined through theoretical (calc.) and experimental (XRD = single-crystal X-ray diffraction; EXAFS = extended X-ray absorption fine structure) techniques for 1, 2 and 3^a.

	An–O			An–N(py)			An–N(tBu)
	Calc.	XRD	EXAFS	Calc.	XRD	EXAFS	Calc.	XRD	EXAFS
Pu (1)	2.296	2.231	2.239	2.546	2.500	2.496	N/A	N/A	N/A
Np (2)	2.245	N/A	2.245	2.576	N/A	2.528	N/A	N/A	N/A
Am (3)	2.329	2.297	N/A	2.544	2.549	N/A	N/A	N/A	N/A
	2.430(b)	2.416(b)		2.673(b)	2.634(b)		2.805(b)	2.641(b)

^apy = N atom of pyridine ring in hydroxylaminato ligand; ^tBu = N atom connected to the tert-butyl group of the hydroxylaminato ligand b = bridging distance; distances are non-bridging unless denoted by (b). In monomeric 1 and 2 there are no An–N_(^tBu) or any bridging interactions. Complex 3 is a dimer, with each Am ion 8-coordinate containing terminal An–O and An–N_(py) bonds as well as three types of bridging interactions: An–N_(py), An–N_(^tBu) and An–O.