Ab initio calculations were used to analyze interactions of BH 4 -with 1-4 molecules of H 2 O at the MP2/6-311??G(d,p) and B3LYP/6-311??G(d,p) computational levels. The negative cooperativity for dihydrogen bond clusters containing H 2 OÁÁÁH 2 O hydrogen bonds is more remarkable. The negative cooperativity is increased with increasing the size and also the number of hydrogen bonds in the cluster. The B-H stretching frequencies show blue shifts with respect to cluster formation. Also greater blue shift of stretching frequencies where predicted for B-H bonds which did not contribute in dihydrogen bonding with water molecules. The structures obtained have been analyzed with the Atoms in Molecules (AIM) methodology.