Diruthenium and diosmium tetracarboxylates: synthesis, physical properties and applications

Dimetal tetracarboxylates, [M-2(O2CR)(4)](n), have received much coverage in the literature. The metals include Cr, Mo, W, Tc, Re, Ru, Os, Co, Rh, Ir, Ni and Cu with n ranging from -2 to +4 (0 to +2 being most common). Diruthenium and diosmium tetracarboxylates form two of the younger families of these ubiquitous compounds and are known to exist as homovalent Ru,(II,II) and Os,(III,III) and mixed-valent Ru,(II,III) and Os,(II,III) species. This paper will provide a comprehensive review of these complexes and include such things as their discovery, synthesis and crystal structures; electronic, vibrational (IR and Raman), ESR and photoelectron spectroscopy; magnetic susceptibility; electrochemistry; kinetics; calorimetry; theoretical calculations such as SCF-X alpha-SW and CASSCF; and more recent studies of their mesomorphic behaviour and biological and catalytic applications. The ruthenium compounds, in particular, have shown a potential application as liquid crystals. Current work (including this author's) is also focused on the development of linear chains involving these metal carboxylate units and bidentate bridges with the view to developing ferromagnetic materials and conductive polymers. There have been no previous reviews on ruthenium (and osmium) carboxylates per se. Cotton and Walton give them some coverage in the context of metal-metal bonds in Multiple Bonds Between Metal Atoms (2nd ed., 1993) however the direct coverage of Ru-2(O2CR)(4) and Os-2(O2CR)(4) type complexes is cursory and dispersed throughout the book. As well, the coverage is only comprehensive through December 1990 with some references from 1991. The current review will be complete through to mid-1997. (C) 1998 Elsevier Science S.A.