A dynamic NMR study of sulphur inversion in transition metal complexes of 2,6-dithiaspiro[3.3]heptane (2,6-DTSH), 2,6-DTSH-2-oxide and 2,6-DTSH-2,2-dioxide

The following complexes were synthesised [W(CO)(5)L-1], [{W(CO)(5)}(2)L-1], [W(CO)(5)L-2], [W(CO)(5)L-3], [{PdCl2(PPh3)}(2)L-1], [PdCl2(PPh3)L-2] and [PdCl2(PPh3)L-3] where L-1=2,6-dithiaspiro[3.3]heptane (2,6-DTSH), L-2=2,6- DTSH-2-oxide and L-3=2,6-DTSH-2,2'-dioxide. In solution these complexes exh ibit pyramidal inversion of the metal-coordinated sulphur atom(s), rates an d activation energies of which were evaluated by total NMR bandshape analys is. Delta G double dagger values were in the range 45-50 kJ mol(-1). These magnitudes are discussed in terms of ring geometry distortions and sulphur lone pair interactions. (C) 1999 Elsevier Science Ltd. All rights reserved.