An NMR study of 2-lithio-1, 3-dithiane and 2-triorganosilyl-, 2-tert-butyl-and 2-phenyl-2- lithiodithianes reveals that all are contact ion pair species in THF and all become separated ions with excess HMPA. The dithianes differ greatly in their ease of ion separation, with the parent lithiodithiane the most difficult.
