Role of electronic factors in the formation of anionic complexes of tellurium(IV): Crystal structure of bis(4-methylbenzoylmethyltriphenylphosphonium) hexabromotellurate(IV)

Abstract

Reactions of [(4-MeOC 6H 4COCH 2)Ph 3P]Br ( 1c) with (4-XC 6H 4COCH 2) 2TeBr 2 (X = H, 2a; Me, 2b; OMe, 2c) lead to Te–C bond cleavage to afford [(4-MeOC 6H 4COCH 2)Ph 3P] 2[TeBr 6] ( 3c). The analogous complexes [(4-MeC 6H 4COCH 2)Ph 3P] 2[TeBr 6] ( 3b) and [(C 6H 5COCH 2)Ph 3P] 2[TeBr 6] ( 3a) are obtained from the reaction of the corresponding phosphonium bromide with 2c. The 1:1 adducts [(4-XC 6H 4COCH 2)Ph 3P] +[(4-XC 6H 4COCH 2) 2TeBr 3] −, formed as intermediates, could be isolated only in case of X = H or Me. The crystal structure of 3b, which crystallizes with one molecule of dichloromethane, shows the presence of close C–H⋯Br/Cl contacts among the ions and solvated molecules. These weak interactions distort, though marginally, the otherwise ideal octahedral shape of the [TeBr 6] − anion adopted as a consequence of stereochemical inertness of the lone pair on the central tellurium atom. The supramolecular extended arrays of ionic molecular units formed by means of solvated head-to-tail linkers are identified.