Synthesis, characterization, and alkoxide transfer reactivity of dimeric Tl2(OR)2 complexes

Abstract

Reaction of LiOC^tBu₂Ph with TlPF₆ forms the dimeric Tl₂(OC^tBu₂Ph)₂ complex, a rare example of a homoleptic thallium alkoxide complex demonstrating formally two-coordinate metal centers. Characterization of Tl₂(OC^tBu₂Ph)₂ by ¹H and ¹³C NMR spectroscopy and X-ray crystallography reveals the presence of two isomers differing by the mutual conformation of the alkoxide ligands, and by the planarity of the central Tl–O–Tl–O plane. Tl₂(OC^tBu₂Ph)₂ serves as a convenient precursor to the formation of old and new [M(OC^tBu₂Ph)_n] complexes (M = Cr, Fe, Cu, Zn), including a rare example of T-shaped Zn(OC^tBu₂Ph)₂(THF) complex, which could not be previously synthesized using more conventional LiOR/HOR precursors. The reaction of [Ru(cymene)Cl₂]₂ with Tl₂(OC^tBu₂Ph)₂ results in the formation of a ruthenium(II) alkoxide complex. For ruthenium, the initial coordination of the alkoxide triggers C–H activation at the ortho-H of [OC^tBu₂Ph] which results in its bidentate coordination. In addition to Tl₂(OC^tBu₂Ph)₂, related Tl₂(OC^tBu₂(3,5-Me₂C₆H₃))₂ was also synthesized, characterized, and shown to exhibit similar reactivity with iron and ruthenium precursors. Synthetic, structural, and spectroscopic characterizations are presented.