Paramagnetic transition metal carbonyls : IV. ESR study of anions derived from (CO)5MnPbPh3 and (CO)4CoPbPh3 by high energy radiation |
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Authors: | Oren P. Anderson Stephen A. Fieldhouse Charles E. Forbes Martyn C.R. Symons |
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Affiliation: | Department of Chemistry, The University, Leicester, Le1 7RH Great Britain |
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Abstract: | Exposure of (CO)5MnPbPh3 to 60Co γ-ray at 77 K gave one major paramagnetic species detectable by ESR spectroscopy. This exhibited an anisotropic hyperfine interaction with 55Mn, near free-spin g-values, and a small, almost isotropic coupling to 207Pb. The form of the A(55Mn) and g-tensor components suggest an orbital of dz2 symmetry on manganese for the unpaired electron, but this cannot be directed along the MnPb bond since the 207Pb hyperfine coupling indicates a very low spin-density on lead. We suggest that the centre is formed by electron addition to manganese to give a formal d7 centre, with concomitant loss of one equatorial carbonyl ligand. We defind z as the direction of the lost ligand. A second centre, detected at high gain, having a large hyperfine coupling to 207Pb and a 31 G coupling to 55Mn is tentatively identified as the parent cation.In marked contrast, the molecule (CO)4CoPbPh3 gave a single centre having comparable 59Co hyperfine and g-tensor components, but also a very large hyperfine coupling to 207Pb (ca. 3300 G). Thus, in this case, an electron gain centre (d9) has been formed, the electron being accomodated in the highest MO having a large dz2 component on cobalt (z being now the CoPb direction).Reasons for the adoption of these different structures are discussed. |
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Keywords: | To whom correspondence should be addressed. |
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