Extended metal atom chain complexes (EMAC) are 1-D arrangements of three or more metal atoms that often contain direct metal-metal bonding and their linearity makes them potential models for molecular wires. Additionally, EMAC of first-row transition metals can have interesting magnetic behaviors because of their propensity towards high spin, the possibility of direct exchange between closely spaced metal atoms, and the possibility of large spin ground states through ferromagnetic coupling. EMAC of this type can be synthetically challenging with first-row transition metals because of their weaker M-M bonds and stronger M-L bonds, a consequence of their smaller size compared to their second and third row counterparts. There are many trimetallic EMAC supported the dipyridyl amine (dpa) ligand, but these complexes commonly take the form M3(dpa)4X2 where M = Cr, Mn, Co, Ni, or Cu and X is a halide or small monoanion. This family of complexes are structurally similar with most containing four dpa ligands in a tetragonal arrangement and the axial ligands aligned co-linear with the metal bonding axis. Presented herein are investigations of unique, trimetallic EMAC of Fe(II) and Co(II) that have three 2,6-bis(trimethylsilylamido)pyridine (L2-) supporting ligands for a composition of M3L3. Much like the dpa supported complexes, these complexes are linear and have two M-M bonds, however they deviate significantly in that the M-M bonds are symmetric, the ligands are in a trigonal arrangement about the {MMM} core, and the axial sites are vacant. Additionally, we are interested in how the {MMM} core responds to modifications to the number of electrons. Our recent attempts to isolate anionic and cationic derivatives from the neutral Fe3L3 and Co3L3 complexes, and the corresponding structural changes, will be presented along with their characterization by X-ray diffraction and 1H NMR including Evan’s method. Preliminary computational results for both neutral complexes will be presented indicating that current methods are able to replicate the experimental results. However, computational investigations into the oxidized and reduced species have yet to converge on a reasonable output.

Structural, electrochemical, and computational investigations of trimetallic, extended metal atom chain complexes of Fe(II) and Co(II) supported by 2,6-bis(trimethylsilylamino)pyridine and their cationic and anionic derivatives

ACS Fall 2021

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