P-BLOCK METALLOCENES - THE OTHER SIDE OF THE COIN

Although transition metal metallocenes {such as ferrocene, [(C5H5)(2)F e]} have been a cornerstone in the development of modern organometalli c chemistry and continue to be a focus for chemical and structural stu dies, in comparison the chemistry of the main group metal counterparts has remained relatively undeveloped. The recent resurgence of interes t in p-block (Groups 13-15) metallocenes in particular has given fresh insights into the structural preferences, bonding requirements and re activity of these under-publicised species, which in many ways represe nt 'the other side of the coin'. The more varied (ionic and covalent) character of the metal-ligand bonds and the less restricted electronic requirements of p-block metals leads to greater structural diversity and radically different reactivity than is found for the transition me tal relatives. This short review focuses on the remarkable range of p- block complexes that has so far been uncovered and attempts to unravel some of the electronic and structural trends in these species.