Recent advances in the chemistry of the Group 13 metals: hydride derivatives and compounds involving multiply bonded Group 13 metal atoms

Two aspects of Group 13 metal chemistry are surveyed in the light of recent research, particularly that reported in the period 1992-1998. The first concerns compounds containing M-H bonds (M = Al, Ga or In) and including binary as well as mixed derivatives in either the base-free or complexed conditions. The second concerns compounds offering the opportunity for the metal atom to engage in multiple bonding. Seemingly unrelated, the two types of molecular compound have several features in common. Both typically contain highly reactive functional groups that are unusually susceptible to oxidation, hydrolysis or aggregation: as a result, developments in both areas have depended on similar strategies. The account focuses (i) on the reactions giving access to the relevant compounds; (ii) on the methodologies of trapping or shielding needed for the preservation of reactive M-H fragments or putative multiple bonds to M atoms; (iii) on the characteristics of the compounds, with particular reference to the structures they assume, and to their response to thermal. photolytic and chemical stimuli; and (iv) on the interplay between experimental and theoretical methods. Some of the hydrides show promise as synthetic reagents or as sources of the metal or metal compounds with extended structures of predefined morphology. On the evidence to hand, pi-type interactions play only a minor role in the chemistry of the Group 13 metals, their contribution being obscured by the effects of low coordination number and non-covalent forces. (C) 1999 Elsevier Science S.A. All rights reserved.