Investigation of paramagnetic species formed during the thermolysis, photolysis, and oxygenation of some bi- and tri-nuclear organometallic compounds of chromium, iron, and molybdenum

Abstract

Oxygenation of the products derived thermally (–70 °C) from [Cr₂(η-C₅H₅)₂(CO)₆](1 a) or photochemically from [Hg{Cr(η-C₅H₅)(CO)₃}₂](2a) or [{(η-C₅H₅)Cr(CO)₃Cu(phen)}_n](3; phen = 1,10-phenanthroline) gives rise to a paramagnetic species [Cr(η-C₅H₅)(CO)_n(O₂)](n⩽ 3), most probably containing a peroxo-ligand and with n= 2. Evidence in support of the structure of this dioxygen complex is adduced from, among other things, experiments using ²H- and ¹⁷O-labelled precursors. Attempts to identify an intermediate in the reaction of (1 a) by using the spin-trapping agents RNO (R = Bu^t or C₆Me₄H) have produced paramagnetic species believed to be side-on bonded nitroso-complexes [Cr(η-C₅H₅)(CO)₂(ONR)](4b); when R = Bu^t this complex decomposes thermally to form Bu^t₂NO and a possible mechanism for this process is discussed.

The solution photolyses are described of derivatives (7), [Fe(η-C₅H₅)(CO)(L)X][L = CO, X = Fe(η-C₅H₅)(CO)₂, HgFe(η-C₅H₅)(CO)₂, SnPh₃, or PbPh₃; L = PPh₃ or alkene, X = SnPh₃], in vacuo with and without added nitrosodurene and also in the presence of air or dioxygen. E.s.r. parameters of the resulting paramagnetic products are reported and discussed. Iron–aminyl oxide complexes are formed with nitrosodurene at –40 °C but at higher temperatures (ca.–10 to +20 °C) photolyses of complexes (7d), (7e), and (7i)(L = CO or PPh₃, X = SnPh₃; L = CO, X = PbPh₃) form a nitroxide (C₅H₅)NO(C₆Me₄H) resulting from Fe–(η-C₅H₅) bond fission. Also, when X = SnPh₃(7d) and (7f)–(7h) or X = PbPh₃(7i) photolysis in vacuo produces paramagnetic iron derivatives which contain the Group 4B metal and the nature of these products is discussed. Solution photolyses of complexes (11), [Mo(η-C₅H₅)(CO)₂(L)X][L = CO, X = Mo(η-C₅H₅)(CO)₃, HgMo(η-C₅H₅)(CO)₃, or CdMo(η-C₅H₅)(CO)₃; L = PPh₃, X = HgMo(η-C₅H₅)(CO)(PPh₃)], are described; e.s.r. data are presented for paramagnetic products arising from reaction with nitrosodurene in vacuo and from oxygenation.