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[Co@Sn6 Sb6 ]3− : An Off-Center Endohedral 12-Vertex Cluster

We report on the asymmetric occupation of a 12-vertex cluster centered by a single metal atom. Three salts of related intermetalloid cluster anions, [Co@Sn6Sb6](3-) (1), [Co-2@Sn5Sb7](3-) (2), and [Ni-2@Sn7Sb5](3-) (3) were synthesized, which have pseudo-C-4v-symmetric or pseudo-D-4h-symmetric 12-vertex Sn/Sb shells and interstitial Co- ions or Ni atoms. Anion 1 is a very unusual single-metal-"centered" 12-atom cluster, with the inner atom being clearly offset from the cluster center for energetic reasons. Quantum chemistry served to assign atom types to the atomic positions and relative stabilities of this cluster type. The studies indicate that the structures are strictly controlled by the total valence electron count-which is particularly variable in ternary intermetalloid cluster anions. Preliminary Sn-119 NMR studies in solution, supported by quantum-chemical calculations of the shifts, illustrate the complexity regarding Sn:Sb distributions of such ternary systems

STERICALLY CROWDED σ‐ AND π‐BONDED METAL ARYL COMPLEXES

Homoleptic complexes in which alkyl or aryl groups are η1-bound to a transition metal form one of the cornerstones of organometallic chemistry. For example, most transition metals form both neutral and anionic complexes with σ-bonding aryl ligands. This chapter discusses the synthesis of the dimesityl iron (II) dimer (FeMes2)2 and its pyridine complex. It describes a series of homoleptic aryl complexes of the first row transition elements manganese, iron, and cobalt. The chapter features the transition metal elements iron and cobalt coordinated to naphthalene or anthracene in an η4 fashion. This coordination mode is indicative of weakened metal ligand bonding. Complexes with naphthalene or anthracene bonded in this way are of interest primarily because of their utility as synthons. It has been recently shown that sterically demanding m-terphenyl ligands can stabilize two-coordinate transition metal centers, in homoleptic complexes