Origin of Selectivity of a Triazinyl Ligand for Americium(III) over Neodymium(III)

Abstract

Abstract [M(EtBTP) 3 ][BPh 4 ] 3 ⋅ 3 CH 3 CN (M=Nd, Am; EtBTP=2,6‐bis(5,6‐diethyl‐1,2,4‐triazin‐3‐yl)pyridine) have been synthesized from reactions of MCl 3 ⋅ n H 2 O with EtBTP in acetonitrile followed by anion metathesis. Structural analysis reveals that these compounds contain M 3+ cations bound by tridentate EtBTP ligands to create a tricapped trigonal prismatic geometry around the metal centers. Collection of high‐resolution, single‐crystal X‐ray diffraction data also allowed reduction in bond lengths esd's, such that a slight contraction of Δ=0.0158(18) Å in the Am−N versus Nd−N bond lengths was observed, even though these cations ostensibly have matching ionic radii. Theoretical evaluation revealed enhanced metal–ligand bonding through back donation in the [Am(EtBTP) 3 ] 3+ complex that is absent in [Nd(EtBTP) 3 ] 3+ .