Potential energy surfaces of neutral and anionic B4H5 clusters were sampled using the Coalescence Kick method. We found that the neutral B4H5 cluster has two optical isomers as either a global minimum structure, or as almost degenerate isomers with the global minimum structure. For the B4H5- anion only the third lowest isomer forms a pair of optical isomers. The chemical bonding patterns revealed by the Adaptive Natural Density Partitioning (AdNDP) analysis can easily explain the geometric structure of even very exotic isomers and global minima. Theoretical vertical electron detachment energies (VDEs) were calculated for comparison with future experimental work. (C) 2011 Elsevier B.V. All rights reserved.