(1,1',3,3'-TETRA-TERT-BUTYL-5,5'-PENTAFULVALENE)DITHALLIUM - SYNTHESIS AND CRYSTAL-STRUCTURE - A CONTRIBUTION TO THE DISCUSSION OF NONCLASSICAL TL(I)-TL(I) INTERACTIONS

Reaction of 1,1',3,3'-tetra-tert-butyl-5,5'-dihydropentafulvalenediyldilithium with stoichiometric amounts of thallium chloride affords the dinuclear complex (eta-5:eta-5-tBu4C10H4)Tl2 (2). Compound 2 is air- and moisture-sensitive, and photolabile. It crystallizes in the space group P1BAR and consists of two (cyclopentadienyl)thallium units which are connected by a central C-C bond and twisted against each other by 70-degrees. The monomeric units of 2 form a two-dimensional polymer with d zick-zack chain of Tl atoms and a periphery of substituted cyclopentadienyl ligands. Rather short Tl - Tl contacts of 3.760 and 3.998 angstrom are formed within a dimeric substructure. The geometry of the cyclopentadienyl ligands around the shortest Tl - Tl bond is similar to that predicted by the theory for weak Tl - Tl interactions.