Ab initio calculations of H interaction on [Formula presented], [Formula presented] ([Formula presented], Mo and W) and [Formula presented] fullerene ([Formula presented]) show relatively weak binding of H in agreement with experimental results of H free [Formula presented] and [Formula presented] clusters. Adsorption of H enhances [Formula presented] bonding between the Si atoms, weakens the [Formula presented] cage interactions and leads to distortions in the cages. [Formula presented] has [Formula presented] magnetic moment in contrast to zero for [Formula presented]. Removal of the [Formula presented] atom leads to stable empty cages of [Formula presented], [Formula presented] and [Formula presented] with large highest occupied–lowest unoccupied molecular orbital gaps of 2.5–3.0 eV, making them attractive for optoelectronic applications. {\textcopyright} 2003 The American Physical Society.