Abstract
Crystal structure, chemical bonding and physical property are discussed for the metal-rich cluster compound Nb6I11-xBrx containing discrete clusters and the layered cluster compound Y2-xMxC2Br2-yIy, focusing on the effect of replacement by other atoms having different mass, size and bonding. Nb6I11-xBrx undergoes a spin cross-over phase transition and with increasing Br content the transition temperature shifts from 274 to 170 K. The highest superconducting transition temperature in the yttrium ethenide halides occurs at a intermediate composition rather than at each end-member.
