Esca study of some chromium complexes: ionization energies and multi-peak structure of the spectra

Catalyst Residue and Oxygen Species Inhibition of the Formation of Hexahapto-Metal Complexes of Group 6 Metals on Single-Walled Carbon Nanotubes

“…The full width half max (FWHM) for our spectra Cr 2p 3/2 signal (without curve fitting) is 2.6-2.9 eV, which is similar to that reported by Kalinina et al (2.3-2.7 eV) [7]. While these values are smaller than that observed for Cr 2 O 3 (3.0 eV) without taking into consideration multiplet splitting [22], they are significantly larger than those reported for bona fide zero valent chromium compounds (1.7 and 2.3 eV) [10]. Based upon the forgoing, it appears that while our spectra are in agreement with those reported previously [7], these peaks are actually indicative of Cr 2 O 3 , suggesting that either oxidation of the Cr has occurred during the reaction or upon exposure to air post-reaction.…”

“…However, comparing the deconvoluted spectra ( Figure 1a, Table 1) with the literature values for various Cr species (Table 2), it appears that these peaks are more likely associated with Cr oxides, since the literature reports that the Cr 2p 3/2 peaks for (C 6 H 6 )Cr(CO) 3 and (C 6 H 6 )Cr(C 6 H 6 ) occur at 576.1 and 575.2 eV, respectively [10]. Thus, the reported C 2017, 3, 17 3 of 15 value of 576.9 eV is too high for either the "(SWCNT)Cr(CO) 3 " or "(SWCNT)Cr(C 6 H 6 )" complexes.…”

“…However, spin-orbit splitting for zero valent Cr compounds is generally between 8.7 and 9.2 eV [22]. In this regard, the values for Cr(CO) 6 , (C 6 H 6 )Cr(CO) 3 , and (C 6 H 6 )Cr(C 6 H 6 ) are 8.9, 8.8, and 9.1 eV, respectively [10]. In contrast, the value for Cr 2 O 3 is 9.7 eV [22].…”

“…Thus, the reported C 2017, 3, 17 3 of 15 value of 576.9 eV is too high for either the "(SWCNT)Cr(CO) 3 " or "(SWCNT)Cr(C 6 H 6 )" complexes. In addition, the literature also reports a multi-peak structure for the Cr 2p spectra of Cr(CO) 6 and (C 6 H 6 )Cr(CO) 3 from shake-up-shake-off processes [10]. Neither our spectra, nor those previously assigned to (SWCNT)Cr(CO) 3 , display these shake up peaks, despite having the same local structure as (C 6 H 6 )Cr(CO) 3 [7].…”

“…The Haddon Group reported a Cr 2p 3/2 binding energy for (SWCNT)Cr(CO) 3 of 576.9 eV as being consistent with Cr(0) η 6 -complexes [7]; however, the accepted value for (C 6 H 6 )Cr(CO) 3 is 576.1 eV [10]. We note that they also reported the binding energy for Cr 2 O 3 to be 575.5 eV, which does not fall within the accepted literature values of 575.7-578.9 eV [11].…”