SPIRO-LAMBDA(4)-SULFANES WITH O-LIGANDS OF DIFFERENT ELECTRONEGATIVITY IN AXIAL POSITIONS - A COMPARISON OF CH2O-S-IV-OCO AND CH2O-S-CENTER-DOT-CENTER-DOT-CENTER-DOT-O=C BOND SYSTEMS(IV)

Two novel diaryl(alkoxy)(acyloxy)spiro-lambda(4)-sulfanes (3 and 5) ex hibiting isomerism in relation to swapping of the five- and six-member ed spiro-rings and two analogous cyclic alkoxysulfonium salts (4 and 6 ) with intramolecular S ... O interaction have been prepared and their molecular structures determined by X-ray diffraction, In all cases th e arrangement of the ligands about the central sulfur atom shows a sli ghtly distorted trigonal bipyramidal (TBP) geometry, In unsymmetrical spiro-lambda(4)-sulfanes the S-O(alkoxy) and the considerably polarize d S-O(acyloxy) bond lengths are 1.686(2) and 2.109(2) Angstrom for 3 a nd 1.683(2) and 2.047(2) Angstrom for 5, respectively. In the analogou s cyclic sulfonium salts the corresponding interatomic distances are 1 .645(3) and 2.255(3) Angstrom for 4 and 1.616(2) and 2.349(2) Angstrom for 6, respectively, The sums of the individual S-O interatomic dista nces found in the investigated spiro-lambda(4)-sulfanes and cyclic alk oxysulfonium salts are 3.795(2) and 3.730(2) Angstrom for 3 and 5, whe reas they are 3.900(3) and 3.965(2) Angstrom for 4 and 6, showing a si gnificant difference between the two intervals, The individual S-O(alk oxy), S-O(acyloxy), S ... O(carbamoyl) and S-C-ar bond lengths, as wel l as the C-ar-S-C-ar bond angles are compared and discussed. The five- and six-membered spiro-rings assume a flattened envelope and a somewh at inverted half-chair conformation, respectively, The almost linear O -S-O bond system is not affected significantly by the different size o f the spiro-rings except the case of sulfur-oxygen nonbonded interacti on.