In this thesis, the nature of the Sn₉4- in solution and its reactivity with transition metal atoms and electrophiles have been studied. The Sn₉4- ion is a very strong Brønsted base that deprotonates en to form the Sn₉H3- ion and is a potent ion sequestering agent that competes with 2,2,2-crypt for binding K+. The Sn₉H3- ion has a pK_a in a range of 32.2– 44 in dmso and can be reversibly interconverted to K₃Sn₉- through addition of K+ and base. Addition of K+ to Sn₉H3- in the absence of base gives the proposed coupled Sn₉–Sn₉6- dimer. The diamagnetic Sn₉H3- ion was mischaracterized as the Sn₉3- paramagnetic radical in numerous publications since 1983. The Sn₉H3- ion reacts with Ni(cod)₂ and Pd(PPh₃)₄ complexes and give the M@Sn₉H3- clusters (M= Ni, Pd). The Ni@Sn₉H3- ion reacts with (arene)M(CO)₃ complexes to form is the Ni@Sn₉M(CO)₃4- ion. Endohedral d–10 atoms do not affect the pK_a's of the hydrido clusters, whereas coordination of M(CO)₃ group (M= Cr, Mo) significantly increases the acidity.

The M@Sn₉SnCy₃3- ions, where M= Ni and Pd, have been prepared with two different synthetic routes from Ni@Sn₉H3- and Sn₉SnCy₃3- ions, respectively. The Ni@Sn₉H3- ion reacts with Cy₃SnCl and gives the Ni@Sn₉SnCy₃3- ion. The Sn₉SnCy₃3- ion reacts with Pd(PPh₃)₄ and gives the Pd@Sn₉SnCy₃3- cluster. The Pd@Sn₉PdSnCy₃3- ion has been prepared from a new type of reaction, where the Pd metal is oxidatively inserted into the exo-bond of Pd@Sn₉—SnCy₃3-.

Two new fused deltahedral clusters have been prepared from Sn₉4-, Ge₉4-, Pd(PPh₃)₄, and Ni(cod)₂ precursors to give the Pd₂@Sn₁₈4-, the largest-known deltahedral cluster to-date, and Ni@Sn₈(μ–Ge)Ni@Sn₈4-, the first example of an endohedral heteroatom cluster.

119Sn, 1H, 13C NMR studies show these clusters to be highly dynamic. The Sn₉SnR₃3- ions (R= Cy and nBu) and M@Sn₉R3- ions (M= Ni, Pd and R= H, SnCy₃) exhibit fast intramolecular exchange of the all 9-Sn atoms, while the exo-substituent groups scramble around the clusters. The Sn₉–iPr3- ion has non-mobile alkyl substituent, which removes the exo-bonded Sn atom from exchanging with the remaining 8-Sn atoms of the cluster.