Diverse solid-state clusters with strong metal-metal bonding. In praise of synthesis

The synthesis, structure and bonding of two types of metal clusters are described. A large family of zirconium cluster halides of the general type A(x)(1)Zr(6)(Z)X(12+n) are obtained with A = Na to Cs, X = Cl, Pr or I, 0 < x, n less than or equal to 6, and the required interstitial Z atom as variables. Extension to the rare-earth elements (Sc, Y, lanthanides) gives some new, hypostoichiometric cluster variations as well as condensed oligomeric and infinite-chain compounds. Zintl-phase concepts and the alkali-metal compounds that contain anionic 'naked' clusters or cluster networks of the triel elements Ga, In and T1 are also covered. The clusters include empty hypoelectronic examples as well as those that are centred by a heterometal or a triel element. The last compounds are remarkable parallels of the interstitial halides described.