Linked arene clusters

Abstract

The synthesis, isolation and characterisation of a number of [2_n]cyclophane transition metal clusters with nuclearities ranging from four to twelve atoms is described. The primary objective of this work has been to prepare molecules composed of alternating cyclophane and cluster subunits which may be considered as precursors to novel organometallic polymer chains and networks. This aim has been achieved to a certain degree using the [2.2.2]paracyclophane ligand, which has been shown to interact with metal clusters (e.g. tetracobalt nonacarbonyl) via all three of its aromatic rings. Also, the dimerisation of a hexa- ruthenium-[2.2.2]paracyclophane complex has yielded a remarkable dodecanuclear bis-arene cluster which may form the basis for a novel linear polymeric chain containing only metal atoms in the backbone. We have also been able to demonstrate that the coordinated [2.2.2]paracyclophane unit is able to embrace metal ions such as Ga^I and Ag^I giving rise to a concomitant change in the observed IR spectrum of the attached cluster. This perspective highlights these areas of research and also examines the factors controlling coordination mode preferences of the [2_n]cyclophane ligand and the central cluster nuclearity and geometry.