Abstract
The structural effects of varied steric bulk on 2,(4),6‐substituted dimethylthallium(III) phenoxides has been examined. The facile reaction of Me~3~Tl with a series of 2,(4),6‐substituted phenols in toluene or diethyl ether resulted in the formation of the species [Me~2~TlO(2,6‐R~2~C~6~H~3~)]~2~ [R = H (4), Me (5), __i__Pr (6), Ph (7)] and [Me~2~TlO(2,4,6‐__t__Bu~3~C~6~H~2~)] (8). All compounds have been characterized by elemental analysis as well as their melting point; FTIR, FT‐Raman, solution ^1^H and ^13^C{^1^H} NMR spectroscopy; and X‐ray crystallography. The structures of 4–7 are dimeric through short intermolecular Tl–O interactions, which yield a symmetric Tl~2~O~2~ unit and a distorted seesaw C~2~O~2~ bonding environment for thallium. An increase in the steric bulk in 4–6 has little effect on Tl–O bond lengths, whereas the C~Me~–Tl–C~Me~ bond angle was found to significantly decrease. Further, the phenoxide ligands in 5 and 6 were found to be oriented perpendicular to the Tl~2~O~2~ unit to minimize steric interactions. Alternatively, compound 7 shows an increase in Tl–O bond lengths and an increase in the C~Me~–Tl–C~Me~ bond angle compared to 4–6, and orientation of the phenoxide ligands perpendicular to the Tl~2~O~2~ core. The significant steric bulk imposed by the –O(2,4,6‐__t__Bu~3~C~6~H~2~) ligand in 8 precludes dimer formation and allows for isolation of a monomeric species that contains a three‐coordinate T‐shaped C~2~O bonding environment for thallium. DFT calculations show that the energetic favorability of dimer formation decreases with increased phenoxide steric bulk.