Photoelectron spectra and bonding in cerocene, bis(.pi.-[8]annulene)cerium(IV)

Abstract

3(µ3-) group was confirmed by the NMR at 20 °C [ -1.04, septet, 2 3*/(PH) = 4.5, '/(PtH) = 598 Hz] and by the -coupled l95Pt NMR spectra,14 and the presence of CO was confirmed by the IR spectrum [¡-(CO) = 1982 cm"1, cf. ¡-(CO) for 1 = 1750 cm'1].8 At -60 °C the '/(PtH) coupling was reduced to 573 Hz and the chemical shift was -1.47. Further characterization was obtained by treating 3 with 13CO to give 2* (* = 13CO labeled). At -90 °C, the hydride signal was at -1.67 ('/(PtH) = 558 Hz and a doublet splitting with /(13CH) = 40 Hz was also observed), and in the 13C NMR spectrum the carbonyl resonance was at 191 as a septet with '/(PtC) = 434 Hz [cf. 209, '/(PtC) = 776 Hz for l]18 with the intensities expected for a Pt3^3-CO) group.12 At room temperature only a broad resonance in the 13C NMR spectrum was observed at 191 without 195Pt satellites and the coupling of 13C to the 3(µ3-) resonance in the NMR was also lost. These data strongly indicate that reversible dissociation of CO from 2 occurs rapidly (14) Migration of a proton through a triangle of metal atoms has been suggested to explain the reversible protonation of [Ni12(CO)21]H4_"]"" in which the hydride ligands are interstitial and may also be involved in the protonation of [Co6(CO)15]2-and in the migration of hydrogen atoms through metallic lattices. This appears to be the first direct evidence and the first time that the barrier to inversion has been determined. The data do not rule out transition states with lower symmetry, for example, with hydride bridging one edge, but these are less likely. A complex with an almost planar Er3(q-H) group is known.

Cerocene Revisited: The Electronic Structure of and Interconversion Between Ce2(C8H8)3and Ce(C8H8)2

“…31 Opening the capillary and examining the volatile material by 1 H NMR spectroscopy shows it to be free EPR Spectrum and ground state of Ce 2 (cot) 2 . As shown in Figure 5, Ce 2 (cot) 3 has the characteristic spectrum of a spin triplet state with axial symmetry, which is clearly indicated by the present of the half-field peak with g=4.83. 20 The zero-field splitting of g ⊥ disappears as the sample temperature is increased above ~3 K, presumably due to exchange narrowing (see Supporting Information, Figure S1).…”

“…29 The TIP value of 1.7(2) × 10 -4 emu/mol compares well with the published value of 1.4(2) × 10 -4 emu/mol using Pascal´s constants. Thermal conversion of Ce(cot) 2 to Ce 2 (cot) 3 . Unlike Th(cot) 2 , which sublimes at 135-160 °C in vacuum, 27,30,31 and U(cot) 2 , which sublimes at 140-210 °C in vacuum, 26,32,33 cerocene does not sublime when heated under diffusion pump vacuum.…”

“…14 The potassium salt of the cerate is an important reagent since Ce(cot) 2 is prepared from it by oxidation with AgI or allyl bromide. 3,15 Alternatively, cerocene can be prepared from Ce(O-i-Pr) 4 •i-PrOH, C 8 H 8 and Et 3 Al. 1 However, this synthetic route requires large quantities of C 8 H 8 as reagent and solvent, which is now very expensive.…”

Study on Electronic Properties of Composite Clusters toward Nanoscale Functional Advanced Materials

“…In [Ln n -(COT) n+1 ], however, an orbital contributing to the ionization process is considered to be discontinuously localized along the molecular axis, because the cluster is bonded through ionic bonds and the charge is localized at each component. Since the first ionization is expected to occur from 4f (Ln) orbitals in (1, 2), 79,80 it is concluded that 4f orbital in the cluster is localized and scarcely interacts with neighboring Ln atoms in the cluster. According to the theoretical calculation of Dolg and co-workers, 74c [Nd(COT) 2 ] is a charge-transfer complex in which 3 of 6 electrons in Nd(6s 2 4f 4 ) transfer almost completely to 2COT, resulting in a configuration of Nd 3+ (COT 1.5¹ ) 2 .…”

“…Since COT 2¹ takes 10³ electronic configuration with the e 2u HOMO as shown in the inset of Figure 7, two ligands of COT 2¹ form two high-lying MOs of e 2u and e 2g with the level ordering e 2u > e 2g . 79,80 Then, the bands of X and A are undoubtedly associated with electron detachment from the highest occupied molecular orbital (HOMO; e 2u ) and the HOMO¹1 (e 2g ) molecular orbitals, respectively. …”