Synthesis and reactivity of dimeric Ar′TITIAr′ and trimeric (Ar′′TI)3 (Ar′, Ar′′= bulky terphenyl group) thallium(I) derivatives:: TI(I)-TI(I) bonding in species ligated by monodentate ligands

The synthesis and characterization of three new organothallium(I) compounds are reported. Reaction of (Ar'Li)(2) (Ar' = C6H3-2,6-(C6H3-2,6-Pr'(2))(2)) and Ar"Li (Ar" = C6H3-2,6-(C6H3-2,6-Me-2)(2)) with TICI in Et2O afforded (Ar'TI)(2) (1) and (Ar"TI)(3) (2). The "dithallene" 1 is the heaviest group 13 dimetallene and features a planar, trails-bent structure with Ar'TI-TI = 119.74(14)degrees and TI-TI = 3.0936(8) angstrom. Compound 2 is the first structurally characterized neutral, three-membered ring species of formula c-(MR)(3) (M = AI-TI; R = organo group). The TI3 ring has TI-TI distances in the range ca. 3.21-3.37 angstrom as well as pyramidal TI geometries. The TI-TI bonds in 1 and 2 are outside the range (2.88-2.97 angstrom) of TI-TI single bonds in R2TITIR2 compounds. The weak TI-TI bonding in 1 and 2 leads to their dissociation into Ar'TI and Ar"TI monomers in hexane. The Ar'TI monomer behaves as a Lewis base and readily forms a 1:1 donor-acceptor complex with B(C6F5)(3) to give Ar'TIB(C6F5)(3), 3. Adduct 3 features an almost linear thallium C(ipso)-TI-B angle of 174.358(7)degrees and a TI-B distance of 2.311(2) angstrom, 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 TI(I) to undergo oxidation to TI(III) due to the unreactive character of the 6s(2) electrons.