Organothallium-sulfur compounds

Dimethyl(diphenylphosphinodithioformato-5,5 )thallium(III), Me2Tl(S2CPPh2) THF, forms supramolecular arrays, 45, via Tl- -S secondary bonds (Tl- -S 3.21 A) slightly longer than the chelating Tl-S primary bonds (2.98 and 3.04 A) [158]. 

Organothalhum(III) thiosemicarbazone derivatives are usually self-organized in solid state supramolecular architectures. An example is (/ -anisaldehyde thiosemi-carbazonato) dimethylthallium(III), which contains four-membered chelate rings (with Tl-N 2.56 A and Tl-S 2.991 A) interconnected in chains by Tl- -S secondary bonds (T1---S 3.304 A) [159], 

Several organothallium(III) dithiophosphates and dithiophosphinates are also assembled in the solid state as supramolecular architectures. These include dime-thylthallium(III) dialkyl dithiophosphates, Me2TlS2P(OR)2, with R = Me, Et, Cy [160], dimethylthallium diethyldithiophosphinate, Me2TlS2PEt2 (Tl-S 2.981 and 

Occasionally the self-assembly modes are more complex and can simultaneously involve Tl- S and Tl - 0 secondary bonds. Thus, dimethylthallium(III) methyl-xanthate, Me2Tl(S2COMe), is associated into a complex architecture, 47, by Tl- - -S bonding (3.19 and 3.35 A, longer than the chelate bonds Tl-S 2.96 A) and Tl- - -O bonding from the methoxy group (Tl- - -O 3.13 A) [165]. 

Similarly, dimethylthallium(III) pyridine-1-oxide 2-thiolate, contains both inter-molecular Tl- - S bonds (3.284 A) and TI2O2 four-membered quasi-cyclic moieties formed by Tl- -O bonding (2.849 A). These connect the chelate tectons into infinite ehains, 48, running along the c axis of the erystal [166]. Dimethylthallium(111) pyridine-2-thiolate is also a chain-like supramolecular array in which the tectons are connected by Tl- -S (2.870 and 3.160 A) and Tl- - -N (2.494 A) bonds [166a]. 

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A general consensus is that hardness increases (or softness decreases) with increasing positive oxidation state. For example, Ni(0) is soft, Ni(II) is borderline, but Ni(IV) is hard the sulfur atom in RS is soft, medium soft in RSO , and it is hard in RSOf is softer than SO 3 . There are a few exceptions to the rule, however. For instance, Tl(III), Sn(IV), and Pb(IV) are softer than their respective lower valent ions. Because T1(I), Sn(II), and Pb(II) ions have electrons in their outermost shells, the shielding of the d electrons decreases the so/tness of the lower valent species (12). One factual demonstration of this reverse hardness/valence relationship is that inorganic thallium compounds are generally more stable in the -1-1 valence state, while covalent organothallium derivatives are stable only in the -i-3 state. 

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