Structural studies of diorganotin(IV) sulfonates: The synthesis of [(n-C4H9)2Sn{OSO2C6H3(CH3)2-2,5}2] and [(n-C4H9)2Sn{OSO2R)2·2(hexamethylphosphoric triamide)] [R=CH3, 4-C6H4CH3, 2,5-C6H3(CH3)2, 2,4,6-C6H2(CH3)3] and crystal structures of [(n-C4H9)2Sn(μ-OH)(OSO2C6H3(CH3)2-2,5)]2 and (n-C4H9)2Sn{OSO2R)2·2(hexamethylphosphoric triamide)] [R=4-C6H4CH3, 2,5-C6H3(CH3)2, 2,4,6-C6H2(CH3)3

Abstract

Reaction of ( n -C 4 H 9 ) 2 SnO with 2,5-dimethylbenzenesulphonic acid yields [( n -C 4 H 9 ) 2 Sn{OSO 2 C 6 H 3 (CH 3 ) 2 - 2 , 5 } 2 ] which on crystallization yields a dimeric compound [( n -C 4 H 9 ) 2 Sn(μ-OH)(OSO 2 C 6 H 3 (CH 3 ) 2 - 2 , 5 )] 2 containing bridging hydroxyl groups between Sn atoms and covalently bonded sulfonate anions. The syntheses of [( n -C 4 H 9 ) 2 Sn{OSO 2 C 6 H 3 (CH 3 ) 2 - 2 , 5 } 2 ] ( 1 ) and [( n -C 4 H 9 ) 2 Sn{OSO 2 R) 2 · 2HMPA] [R = CH 3 ( 3 ) , 4 -C 6 H 4 CH 3 ( 4 ), 2 , 5 -C 6 H 3 (CH 3 ) 2 ( 5 ), 2 , 4 , 6 -C 6 H 2 (CH 3 ) 3 ( 6 )] have been carried out to study their structures and to delineate the coordination behavior of the weakly coordinating sulfonate anions. Compound 1 hydrolyzes slowly to [( n -C 4 H 9 ) 2 Sn(μ-OH)(OSO 2 C 6 H 3 (CH 3 ) 2 - 2 , 5 )] 2 ( 2 ) when kept in CH 2 Cl 2 for a few days. The crystal structure shows that 2 has a dimeric structure in which tin atoms are bridged by two hydroxy groups and each tin atom is further bonded to two n -Bu groups and a mono-coordinated sulfonate anion thus generating a trigonal bipyramidal geometry at tin atom. However, the coordination geometry at tin can be visualized as a severely distorted octahedron, if a relatively weak Sn–O bond of 2.690 Å between Sn and an O atom of the neighboring sulfonate anion is also considered. Compounds 3–6 are obtained by the consecutive reaction of ( n -C 4 H 9 ) 2 SnO with the appropriate sulphonic acid and hexamethylphosphoric triamide (HMPA). X-ray crystal structures of 4, 5 and 6 s how octahedral geometry around tin atom in the two compounds in which the sulfonate ligands are covalently bonded in a monodentate mode. Compounds 3–6 are nonionic in polar solvents. The Sn–O (sulfonate) bond distances 2.354(2), 2 ; 2.233(2), 4 ; 2.237(5), 5 and 2.227(3) Å, 6 suggest some degree of ionic character in the metal-anion bonds. These compounds have also been characterized by multinuclear ( 1 H, 13 C and 119 Sn) NMR studies.