Carbonyl cyclopentadienylnitro complexes of iron and ruthenium and their oxygen atom transfer reactions.

Abstract

New and reactive nitro organometallics, Fe(C₅H₅)(CO)₂(NO₂), Ru(C₅H₅)(CO)₂(NO₂), their nitrogen-15 derivatives, Fe(C₅H₅)(CO)(PPh₃)(NO₂), and [Fe(C₅H₅)(CO)(PPh₃)L]NOₓ (where L = MeOH or MeCN and x = 2 or 3), were isolated and characterized by elemental analysis, IR, and NMR. The compounds were made by reactions of [Fe(C₅H₅)(CO)₂]₂, Fe(C₅H₅)(CO)₂I, [Ru(C₅H₅)(CO)₂]₂, and Fe(C₅H₅)(CO)(PPh₃)I with silver nitrite. The molecular and packing structures of Fe(C₅H₅)(CO)₂(NO₂) and Ru(C₅H₅)(CO)₂(NO₂) were determined by single-crystal X-ray diffractometry at -100°C and 26°C, respectively. Although stable at low temperature, Fe(C₅H₅)(CO)₂(NO₂) and Fe(C₅H₅)(CO)(PPh₃)(NO₂) decomposed at room temperature with evolution of CO₂ and concomitant formation of unstable metal nitrosyl complexes. In the case of Fe(C₅H₅)(CO)₂(NO₂), the mixture of products included Fe(C₅H₅)(CO)(NO), [Fe(C₅H₅)(NO)]₂, Fe(C₅H₅)₂, N₂O, CO, intractable material, and [Fe(C₅H₅)(CO)₂]₂. The kinetics of the oxygen transfer reactions of Fe(C₅H₅)(CO)₂(NO₂) and Fe(C₅H₅)(CO)(PPh₃)(NO₂) have been studied by NMR and IR of the solution, by IR and manometry of the gas phase, and by IR and elemental analysis of the intractable residues. The enthalpies and entropies of activation were obtained from Eyring plots of the reaction rate constants of Fe(C₅H₅)(CO)₂(NO₂) at 20, 30, and 40°C. Ru(C₅H₅)(CO)₂(NO₂) decomposes slowly with evolution of CO₂ at 40°C. In addition to the experiments outlined above, the dissertation includes discussions of the coordination chemistry of the new compounds in light of the few reports of other nitro organometallics and the calculations of molecular orbitals and energies. Also, the angular orientation of the basicity of the nitrite ion was probed by extended Huckel calculations of the orbital energies of hydrogen nitrite as the proton was moved around the nitrite ion. Lastly, ⁵⁷Fe-¹³P spin-spin coupling was measured in Fe(CO)₄(PPh₃) by ³¹P NMR.