Ultraviolet vapour-phase absorption spectra of d6 metallocenes

Rydberg transitions in titanium sandwich complexes: Gas-phase and solution-phase photoabsorption study of (η7-C7H7)(η5-C5H5)Ti, (η8-C8H8)(η5-C5H5)Ti, and (η8-C8H8)(η5-C5Me5)Ti

“…The Rydberg transitions contributing to the (Ch)(Cp)Ti gasphase spectrum are much broader than those originating at the metal d z 2 orbital in sandwich complexes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] This agrees well with a more delocalised character of the e 2 orbital as compared to MO a 1 in the (Ch)(Cp)M molecules. The ab initio 24 and DFT 32 MO calculations predict 38-44% metal contribution to the e 2 orbital of (Ch)(Cp)M (M ¼ Ti, V, Cr, Nb, Ta) while ca.…”

“…3) shows a progression with the components separated by 230 cm À1 . Similar values characterise vibronic structures of the R4p x,y transition in the spectra of (Z 6 -C 6 H 6 ) 2 Cr, 6 (Ch)(Cp)Cr, 11,14 (Cp) 2 Fe 15,16 and (Ch)(Cp)V. 18 This separation correlates very well with the frequency of the symmetric metal-ligands stretching vibration in the (Z 6 -C 6 H 6 ) 2 Cr and (Cp) 2 Fe molecules (277 and 304 cm À1 , respectively [42][43][44] ). The appearance of the vibrational progression confirms the Rydberg nature of the 27 300 cm À1 band (Figs.…”

“…Transition metal sandwich compounds appear to reveal in the gas-phase absorption spectra interesting features which arise from electronic transitions originating at the non-bonding metal a 1 (d z 2) level and terminating at Rydberg MOs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Molecular Rydberg orbitals are derived from the AOs with principal quantum numbers higher than those for valence-shell MOs. 20,21 They are atomic-like and can be characterised by azimuthal quantum numbers l. The l value determines the type of a Rydberg MO (s, p, d, ...).…”

“…The spectra of metallocenes 15,16 and mixed sandwich complexes (Ch)(Cp)M (M ¼ V, Nb) 17,18 show only lower-lying individual Rydberg bands which have been assigned on the basis of their term values. The T magnitudes are similar for the lowest transitions to the Rydberg orbitals of each type in various sandwiches.…”

Ruthenocenes and Osmocenes

“…58 Electronic absorption spectra of MCp 2 , MCp* 2 and RuCpCp* have been assigned; the spectra are sensitive to changes in molecular symmetry as shown in the mixed system which shows an extra absorption. 59 In the gas phase, absorptions not present in the corresponding solution spectra were assigned to the Rydberg transitions nd {a[ ,->(« + l)p (ei > or (n + l)p (fli > while, for RuCpCp*, Ad -> 5 5 and 5 r c transitions were found.…”