Metal Atom Chemistry. (η⁵-Cyclopentadienyl)Metal and (η⁶-Arene)Metal Fragments as Building Blocks for Transition Metal Clusters

The synthesis of small ligand stabilized metal clusters is the subject of this account. Homo and mixed metal clusters of group VIII metals Co and Ni with varying organic ligand environment can be prepared by reaction of naked metal atoms with various substituted cyclopentadienyl and arene ligands and a number of different organometallic complexes. In three component reactions, Co or Ni atoms react with mesitylene or pentamethylcyclopentadiene Me₅CpH, and either [Fe(CO)₅] or [CpR Co(CO)₂] (R = H, Me₅, iso-Prop₂, tert-Bu₂) to form homo or mixed trinuclear clusters with Co₃, Co₂Fe, Ni₂Co or Ni₂Fe metal core. This technique of reacting metal atoms with organometallics in presence of an appropriate organic ligand offers an unusual access to molecular organometallic clusters and holds some promise as a general method for synthesis of ligand stabilized metal clusters. Another valuable synthetic approach to organometallic cluster chemistry we have studied along this line is reaction of metal atoms with equimolar amounts or organic ligands. In reactions of cobalt and nickel atoms with differently alkyl substituted Cp ligands we have found a variety of unexpected products from these reactions. The underlying principle which might be responsible for the formation of either simple mononuclear or higher nuclearity metal cluster compounds in these metal atom reactions is discussed.

metal atoms - metal ligand fragments - organometallic clusters - metal atom synthesis