Data for paper: Targeted Synthesis of End-on Dinitrogen-bridged Lanthanide Metallocenes and their Reactivity as Divalent Synthons

Dataset for Targeted Synthesis of End-on Dinitrogen-bridged Lanthanide Metallocenes and their Reactivity as Divalent Synthons published in Journal of the American Chemical Society September 2023

Data files
CIF and checkCIF files for all crystal structures.

IR spectroscopy data for all compounds.

Raman spectroscopy data for all compounds.

UV/visible spectroscopy data for all compounds.

Magnetic measurement data for all compounds.

Article abstract
High-yield syntheses of the lanthanide dinitrogen complexes [(Cp2tttM)2(μ-1,2-N2)] (1M, M = Gd, Tb, Dy; Cpttt = 1,2,4-C5tBu3H2), in which the [N2]2– ligands solely adopt the rare end-on or 1,2-bridging mode, are reported. The bulk of the tert-butyl substituents and the smaller radii of gadolinium, terbium, and dysprosium preclude formation of the side-on dinitrogen bonding mode on steric grounds. Elongation of the nitrogen-nitrogen bond relative to N2 is observed in 1M, and their Raman spectra show a major absorption consistent with N═N double bonds. Computational analysis of 1Gd identifies that the local symmetry of the metallocene units lifts the degeneracy of two 5dπ orbitals, leading to differing overlap with the π* orbitals of [N2]2–, a consequence of which is that the dinitrogen ligand occupies a singlet ground state. Magnetic measurements reveal antiferromagnetic exchange in 1M and single-molecule magnet (SMM) behavior in 1Dy. Ab initio calculations show that the magnetic easy axis in the ground doublets of 1Tb and 1Dy align with the {M–N═N–M} connectivity, in contrast to the usual scenario in dysprosium metallocene SMMs, where the axis passes through the cyclopentadienyl ligands. The [N2]2– ligands in 1M allow these compounds to be regarded as two-electron reducing agents, serving as synthons for divalent gadolinium, terbium, and dysprosium. Proof of principle for this concept is obtained in the reactions of 1M with 2,2′-bipyridyl (bipy) to give [Cp2tttM(κ2-bipy)] (2M, M = Gd, Tb, Dy), in which the lanthanide is ligated by a bipy radical anion, with strong metal–ligand direct exchange coupling.