Synthesis and Reactivity of Dimeric Ar‘TlTlAr‘ and Trimeric (Ar‘ ‘Tl)3 (Ar‘, Ar‘ ‘ = Bulky Terphenyl Group) Thallium(I) Derivatives: Tl(I)−Tl(I) Bonding in Species Ligated by Monodentate Ligands
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posted on 2005-04-06, 00:00 authored by Robert J. Wright, Andrew D. Phillips, Shirley Hino, Philip P. PowerThe synthesis and characterization of three new organothallium(I) compounds are reported.
Reaction of (Ar‘Li)2 (Ar‘ = C6H3-2,6-(C6H3-2,6-Pri2)2) and Ar‘ ‘Li (Ar‘ ‘ = C6H3-2,6-(C6H3-2,6-Me2)2) with TlCl
in Et2O afforded (Ar‘Tl)2 (1) and (Ar‘ ‘Tl)3 (2). The “dithallene” 1 is the heaviest group 13 dimetallene and
features a planar, trans-bent structure with Ar‘Tl−Tl = 119.74(14)° and Tl−Tl = 3.0936(8) Å. Compound
2 is the first structurally characterized neutral, three-membered ring species of formula c-(MR)3 (M = Al−Tl; R = organo group). The Tl3 ring has Tl−Tl distances in the range ca. 3.21−3.37 Å as well as pyramidal
Tl geometries. The Tl−Tl bonds in 1 and 2 are outside the range (2.88−2.97 Å) of Tl−Tl single bonds in
R2TlTlR2 compounds. The weak Tl−Tl bonding in 1 and 2 leads to their dissociation into Ar‘Tl and Ar‘ ‘Tl
monomers in hexane. The Ar‘Tl monomer behaves as a Lewis base and readily forms a 1:1 donor−acceptor
complex with B(C6F5)3 to give Ar‘TlB(C6F5)3, 3. Adduct 3 features an almost linear thallium C(ipso)−Tl−B
angle of 174.358(7)° and a Tl−B distance of 2.311(2) Å, which indicates strong association. Treatment of
1 with a variety of reagents resulted in no reactions. The lower reactivity of 1 is in accord with the reluctance
of Tl(I) to undergo oxidation to Tl(III) due to the unreactive character of the 6s2 electrons.
