Applications of Carbon‐13 NMR in Inorganic Chemistry

Experimental and Molecular Dynamics Simulation Study of the Sublimation Energetics of Cyclopentadienyltricarbonylmanganese (Cymantrene)

“…The assignments were based on literature data. , 1 H NMR (400 MHz, CDCl 3 /TMS): δ = 4.756 (s, 5H, C 5 H 5 ); 13 C NMR (400 MHz, CDCl 3 /TMS): δ = 82.79 (s, 5C, C 5 H 5 ), δ = 224.1 (s, 3C, CO). The results of the 13 C NMR spectra are in good agreement with the previously reported values δ = 83.1 and δ = 225.1. , The powder pattern was indexed as monoclinic, space group P 2 1 / a , with a = 11.99 Å, b = 7.07 Å, c = 10.93 Å, and β = 117.8°. These values are in good agreement with a = 12.077(3) Å, b = 7.057(2) Å, c = 10.913(2) Å, and β = 117.68(2)°, previously obtained at room temperature from single-crystal X-ray diffraction experiments. , No phase transitions other than fusion were detected by DSC in the range between 283 K and the fusion temperature when using samples with masses in the range of 3.9−6.3 mg and a scan rate of 3 K·min −1 .…”

“…40 The enthalpy of sublimation of Mn(η 5 -C 5 H 5 )(CO) 3 at 298. 15 Eq 5 was derived from a linear least-squares fitting to the C p,m o (g) values in the range 280-320 K, calculated by statistical thermodynamics, 41 by using structural unscaled vibration frequency data obtained at the B3PW91/SDDAll level of theory, together with harmonic-oscillator/rigid-rotor partition functions. Equation 6 was determined from a similar fitting to the C p,m o (cr) results obtained by DSC in the range 280-318 K. Where comparison is possible, these results agree to within 1-2% with the corresponding adiabatic calorimetry data reported for temperatures below 300 K. 5 The enthalpy of sublimation of Mn(η 5 -C 5 H 5 )(CO) 3 was also measured by Calvet drop-sublimation microcalorimetry, at 305.2 K, leading to ∆ sub H m o (305.2 K) ) 75.80 ( 0.37 kJ • mol -1 .…”

“…The results of the 13 C NMR spectra are in good agreement with the previously reported values δ ) 83.1 and δ ) 225.1. 14,15 The powder pattern was indexed as monoclinic, space group P2 1 /a, with a ) 11.99 Å, b ) 7.07 Å, c ) 10.93 Å, and β ) 117.8°. These values are in good agreement with a ) 12.077(3) Å, b ) 7.057(2) Å, c ) 10.913(2) Å, and β ) 117.68(2)°, previously obtained at room temperature from single-crystal X-ray diffraction experiments.…”

Homoleptic Isocyanidemetalates of 4d- and 5d-Transition Metals: [Nb(CNXyl)6]-, [Ta(CNXyl)6]-, and Derivatives Thereof1

“…In particular, two carbonyl 13 C environments are present in a 1:4 ratio, where the unique axial CO, δ C = 221.1 ppm, is about 5 ppm downfield of the value for the equatorial carbonyls, δ C = 216.2 ppm, which establishes that CNXyl is a better donor and weaker acceptor than CO in 8 . A similar 13 C NMR spectrum has been reported for [Ta(CO) 5 NH 3 ] - , δ 225.0 (1C, axCO), 219.4 (4C, eq CO), where the 3−4 ppm downfield shifts of the axial and equatorial CO resonances, compared to those of 8 , are due to the better donor ability of NH 3 relative to CNXyl …”

“…A similar 13 C NMR spectrum has been reported for [Ta(CO) 5 NH 3 ] -, δ 225.0 (1C, axCO), 219.4 (4C, eq CO), 39 where the 3-4 ppm downfield shifts of the axial and equatorial CO resonances, compared to those of 8, are due to the better donor ability of NH 3 relative to CNXyl. 43 Another indication CO is a better acceptor ligand than CNXyl in 8 is that its isocyanide carbon resonance, δ C ) 182.4 ppm, is quite upfield of the analogous shift observed for the homoleptic anion 7, δ C ) 210.4 ppm. Nevertheless, the 13 C resonance of the ligating isocyanide carbon in 8 is appreciably deshielded relative to that observed for free CNXyl, δ C ) 165.4 ppm, 44 indicating a substantial dπ (Ta) to pπ* (CNXyl) backbonding in 8, a conclusion in accord with IR spectral data, vide supra.…”