“…Throughout this paper the form [T~----O] 3+ is used to describe the Tc--oxo multiple bond according to the well known bond situation in oxo complexes where the M--O bond has three components (one ~r and two rr), out of which two are covalent and one is donor-acceptor (Tc----~O) (Shustorovich, Porai-Koshits & Buslaev, 1975). This formalism is useful to distinguish the bond situation in oxo [Tc-~-O] 3+ complexes, where Tc--O distances fall in the range 1.61-1.68 A with stretching frequencies in the range 920-1020cm -~, from that in dioxo [O--Tc=O] + complexes where the distances and stretching frequencies occur in the ranges 1.74-1.75 A and 790-880cm -~ respectively (Zuckman, Freeman, Troutner, Volkert, Holmes, Van Derveer & Kent Barefield, 1981;Kastner, Lindsay & Clarke, 1982;Jurisson, Aston, Fair, Schlemper, Sharp & Troutner, 1987).…”