Infrared bands of isotopic benzenes: ν13 of 12C6D6 and ν12 of 13C6H6

Reversible Cleavage/Formation of the Chromium–Chromium Quintuple Bond in the Highly Regioselective Alkyne Cyclotrimerization

“…[10d] Since the inverted arene sandwich complexes were typically prepared from reduction of metal halide precursors in aromatic solvents, [17,18] 5 was alternatively obtained in ag ood yield (67 %) from KC 8 reduction of CrCl 2 (THF)(k 2 -HC(N-2,6-i Pr 2 C 6 H 3 ) 2 (9) [10d] with five equivalents of 1,3,5-(Me 3 Si) 3 C 6 H 3 in Et 2 O. Themost salient structural feature of 8 is that two less bulky 2,6-Me 2 C 6 H 3 substituents are arranged in the same side along the Cr···Cr axis with the torsion angle N2-Cr1-Cr2-N3 of 60.0(2)8 8.All six CÀCbond lengths of the central arene rings in 6 and 8 are very close and provide an average CÀC separation of 1.45 for both complexes.T hese bond lengths are comparable with those reported values found for the mh 6 :h 6 -arene ligands in inverted sandwich compounds, [17,18] but slightly longer than those reported for free benzene (1.397-(1) ) [19] and toluene (1.39 (1) ). Tw oCN 2 Cr four-membered rings are arranged in an orientation with aN 1-Cr1-Cr2-N4 torsion angle of 54.9(2) (5)a nd 67.4(2)8 8 (8).…”

Complex symmeterized analysis of benzene vibrations

“…The E 1 u vibrational energies, calculated with the determined force constant values (Table V), have been summarized in Table IV. From the data presented in Table IV, it is seen that the agreement between calculated and experimentally measured values is good, especially for the fundamentals and the lower overtones, where very reliable experimental data exist 13–15, 17, 18, 20, 21. On the other hand, from Table V it is seen that this good agreement was achieved at harmonic force constant values substantially different from those determined previously by Goodman et al 13.…”

“…Calculations were carried out not only on the three fundamental frequencies ν 18 , ν 19 , ν 20 but also on higher E 1 u CH stretch overtone energies CH(v), at v ≤ 6, as functions of the values of the relevant harmonic force constants in benzene C 6 H 6 . The calculated vibrational energies are compared to existing experimentally measured data 13–21. The determined values of the force constants, by adjustment of the calculated to the experimentally measured vibrational energies, are displayed in Table V, together with the previously empirically determined values by Goodman et al 13 for comparison.…”

Sub-Doppler rotationally resolved spectroscopy of the bands of benzene and benzene-d6

“…By measuring infrared spectra of isotopically substituted benzene molecules, Pl ıva et al [3] determined the distances r 0 C-C and r 0 C-H to be 1.3969 and 1.0815 A, respectively. By comparing the rotational structure of the S 1 1 B 2u S 0 1 A 1g absorption spectrum and the computed contours of C 6 D 6 and C 6 H 6 , Callomon et al [14] evaluated the C-C and C-H distances in the S 1 1 B 2u state to be 1.435 and 1.07 A, respectively.…”

“…High-resolution Raman and infrared spectra have been used to determine the molecular structure in the electronic ground state [1][2][3]. A high-resolution Fourier transform spectrometer and a tunable infrared laser spectrometer have been used to study many vibrational bands in the ground state, and accuracies of the molecular constants have been improved [3][4][5][6][7].…”