Structure, bonding, and dipole moment of (CH3)(3)N-SO3. A microwave study

Six isotopic derivatives of the complex (CH3)(3)N-SO3 have been studied in the gas phase by microwave spectroscopy. The N-S bond length is 1.912(20) A ngstrom, and the NSO angle is 100.1(2)degrees. The dipole moment, determine d from Stark effect measurements, is 7.1110(69) D, representing an enhancem ent of 6.5 D over the sum of the dipole moments of the free monomers. Analy sis of the N-14 nuclear hyperfine structure indicates that about 0.6 e is t ransferred from the nitrogen to the SO3 upon formation of the complex. Comp arison between the gas-phase structure and that previously determined for t he adduct in the solid state reveals small but significant differences, ind icating that the formation of the dative bond is slightly less advanced in the gas. Gas-phase and solid-state structural data are compared for several related amine-SO3 systems.