Delocalization of metal

Study of the phosphorescence (and absorption) spectra of chromium(III) complexes has been used to determine to what extent delocalization of metal d electrons onto the ligands is possible. Using the absorption spectrum of Cr(H20)83 +, for example, it is possible to... 

In the experimental UPS of HRe(CO)5 (87, 161, 174) the splitting of the first and second bands is 0.31 eV and that between the second and third bands is 0.34 eV (Fig. 9). These relative spacings are consistent only with Scheme III, thus confirming that the e MO is less stable than the b2 MO. The spin—orbit coupling parameter, f5d(Re), of 0.25 eV deduced from the spectra compares with the range 0.26-0.34 eV estimated for the Re2 cation (136, 156). The reduction of fsd(Re) in HRe(C0)4 is consistent with the delocalization of metal 5d electrons into the 2ir MOs of the CO ligands. 

In order to further experimentally probe the covalenf delocalization of metal and ligand valence orbitals in the CuCl complex, variable energy. photoelectron spectroscopy of the valence band of and CuCl has been employed. Through knowledge of... 

As far as optical spectra are concerned, Jorgensen (19, 20, 22) has rationalized a large body of experimental data in terms of the parameters 10 Dq and B. Two different origins of the nephelauxetic effect have been advanced (19) (i) the central-field covalency is due to screening the nuclear charge of the central ion by electrons of the ligands (ii) the symmetry-restricted covalency is caused by delocalization of metal d electrons onto the ligands (the delocalization is symmetry dependent eg electrons for... 

EPR spectroscopy suggests that part of this stabilization arises from Jt-delocal-ization. g values in [Co(9S3)2] (Table 5) deviate little from g, a reflection of appreciable delocalization of metal electron density onto the ligands [22, 99]. 

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