7  Oxygen, sulfur, selenium and tellurium

Abstract

This chapter reviews original highlights in the chemistry of the Group 16 elements reported during 2002. The bulk of the review focuses on the chemistry/interaction of the chalcogens with other p-block elements. Due to the vast abundance and diversity of research into chalcogen chemistry, the report has been limited to materials with discrete molecular structure, either as novel products or reagents, or obtained by new synthetic strategies. The most important advances in 2002 include the isolation of hitherto unknown functionalities or bonding modes 28,56,60,64 and unusual, unique or unexpected structures. 53,63,79,81 Sulfur, selenium and telluriumAs in previous years, we start by looking at the ability of the heavier chalcogens to form compounds with other p-block elements, and do so by working from left to right across the periodic table starting with Group 13. The preparation of crystalline thioboric acid, (HBS 2 ) 3 , involves the reaction of hydrogen sulfide gas bubbled through molten B 2 S 3 at 500 ЊC. 1 The experimental procedure has several advantages over previous methodologies (e.g. higher purity, lower reaction temperatures) and the material is an important precursor to thioborate glasses and polycrystals. Studies on chalcogen-containing boron clusters included: the S-alkylation and S-amination of methyl thioethers of closo-[B 12 H 12 ] Ϫ derivatives as potential materials for boron neutron capture therapy of cancer; 2 the structural analysis by microwave spectroscopy and quantum chemical calculations of 1-thia-closo-decaborane( 9), 1-SB 9 H 9 ; 3 the single crystal X-ray characterisation of three dinuclear half-sandwich complexes containing bridging dicarba-closo-dodecaboranes:A two-coordinate thallium compound {[Me 2 Si(µ-N t Bu) 2 P᎐ ᎐ S(NPh)-κN-κS]Tl} and two tetrahedral aluminium complexes {[Me 2 Si(µ-N t Bu) 2 P᎐ ᎐ S(NPh)-κN-κE ]AlMe 2 } and {[Me 2 Si(µ-N t Bu) 2 P᎐ ᎐ Se(NPh)-κN-κE ]AlMe 2 } have been synthesised from the reaction of P-anilino-P-chalcogeno(imino)diazasilaphosphetidines and thallium monochloride and trimethylaluminium. 5 The first X-ray crystal structures of homoleptic aluminium alkanethiolate complexes have been reported; [Al(µ-SR)-(SR) 2 ] 2 (R = t-Bu and i-Pr) were prepared from the reactions of NaCSMe 3 with AlBr 3