AbstractMNDO parameters for helium are derived from an optimization that employs only atomic and diatomic reference data. Comparisons with published high‐levelab initioresults indicate that MNDO correctly predicts the existence of covalently bonded helium compounds and normally reproduces the geometries of these small charged molecules reasonably well. Endohedral fullerene–helium complexes and the transition states for their formation are studied for C60, C60, and C 602+. The calculated barriers are discussed and compared with those for the passage of helium through C6H6, C6H 6+, and C6H 62+. © 1993 John Wiley