203,205Tl NMR Studies of Crystallographically Characterized Thallium Alkoxides. X-ray Structures of [Tl(OCH2CMe3)]4 and [Tl(OAr)]∞, Where OAr = OC6H3(Me)2-2,6 and OC6H3(CHMe2)2-2,6
journal contributionposted on 28.03.2001, 00:00 by Cecilia A. Zechmann, Timothy J. Boyle, Dawn M. Pedrotty, Todd M. Alam, David P. Lang, Brian L. Scott
[Tl(OCH2Me)]4 (1) was reacted with excess HOR to prepare a series of [Tl(OR)]n, where OR = OCHMe2 (2, n = 4), OCMe3 (3, n = 4), OCH2CMe3 (4, n = 4), OC6H3(Me)2-2,6 (5, n = ∞), and OC6H3(CHMe2)2-2,6 (6, n = ∞). Single-crystal X-ray diffraction experiments revealed that in the solid state the alkoxide-ligated compound 4 adopts a cubane structure, whereas the aryloxide derivatives, 5 and 6, formed polymeric chains. Compounds 1−6 were also characterized by 203,205Tl solution and 205Tl solid-state NMR spectroscopy. In solution it was determined that 1−4 retained the [Tl−O]4 cube structure, whereas the polymeric species 5 and 6 appeared to be fluxional. Variations in the solution and solid-state structures for the [Tl(OR)]4 cubes and polymeric [Tl(OAr)]∞ are influenced by the steric hindrance of the ligand. The acidity of the parent alcohol influences the degree of covalency at the Tl metal center, which is reflected in the 203,205Tl chemical shifts for 1−6.