It has been postulated that 'Frustrated Lewis Pairs' preform an ‘encounter complex’ associated by van der Waals forces, and that is it is this complex that interacts, and activates hydrogen, in a bi-molecular fashion. The formation of encounter complexes has been proposed from theory, however there have been only very limited experimental studies to support their existence. This objectives of these studies are to gain a direct experimental observation of the encounter complex between pairs of hindered Lewis acids and bases in solution.