Abstract: Novel catalyst compositions comprising complexes of tin(IV) salts and amine compounds are used to prepare polyurethanes, polyureas, polycarbodiimides and polyisocyanurates. The complexes, which preferably employ primary amines, allow delay of gelation until they dissociate under certain reaction conditions. The complexes can be prepared neat or in situ in an active hydrogen containing formulation component. The complexes serve to delay gelation of the formulation because they can be prepared to be relatively stable to moisture and will predictably dissociate upon heating, either as a result of the exothermic nature of the reaction being catalyzed or with application of an external heat source. The catalyst compositions are particularly useful for preparation of carpet underlay and in other applications requiring significant delay prior to gelation.