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|Title:||A study of paramagnetic transition metal carbonyls and cyanides by electron spin resonance spectroscopy.|
|Authors:||Wyatt, Jane L.|
|Presented at:||University of Leicester|
|Abstract:||Exposure of diamagnetic transition metal carbonyls and cyanides either as the pure compounds or as dilute solutions to ionizing radiation at 77 K results in the formation of electron-loss and electron-capture centres. Working at low temperatures enables unstable complexes to be studied that are not detectable by conventional procedures. The low concentrations produced are ideal for e.s.r. studied since spin-spin broadening is avoided. Four types of complex are studied, each involving a different transition metal-ligand bond. Exposure of dilute solutions of Fe(CO)5 in 2-methyltetrahydrofuran to 60Co ?-rays at 77 K resulted in electron addition to give a 3d9 species, tentatively identified as Fe(CO)5-. The form of the g-tensor components requires a 3d1z2 assignment for the unpaired electron on Fe. A similar study of Mn2 (CO)8 (PR3)2 and M(CO)5X (M = Cr, Mo, W, Re; X = Br, I) shows the excess electron to be accommodated in the metal- metal and metal-halogen o* orbitals respectively. Resolved hyperfine coupling from the 2 axial 31P nuclei in Mn2(CO)8 (PR3)2 reveals information regarding the delocalisation of the excess electron upon the axial ligands. Electron addition to mixed ligand complexes, MCp(CO)nX, (M = Mo, W, Fe; X = C1, I) results in electron capture into the metal-halogen o* orbitals, suggesting this is preferred to association with the organic ligand. The transition metal-hydrogen atom bond was probed in the same way. ?-Radiolysis of Pt(CN)42- ions in aqueous sulphuric acid matrices at 77 K results in the formation of [H-Pt (CN)4]2-, the unpaired electron being in a o* orbital confined to hydrogen and platinum. Finally, it was hoped to form a transition metal-alkyl bond in the same way, using Pt(CN)42- and Ni(CN)42- ions in a variety of solvents known to produce alkyl radicals on radiolysis, but these experiments have so far been inconclusive.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Chemistry|
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