Experiment and theory have been used to study reactive alkyne pi complexes, intermediates in anti-Markovnikov alkyne hydration by GpRu bis(phosphine) catalysts with heterocyclic substituents. Each heterocycle accepts a hydrogen bond from an acetylene C-H, as revealed by NMR coupling constants between alkyne C-13 and H-1 nuclei as well as between alkyne C-13 and pyridine N-15 ((2h)J(CN)). Moreover, further alkyne transformations occur at temperatures from 50 to 90 degrees C below what is needed to convert a control compound without the heterocycles.