The presence of an intramolecular XH...HM interaction between the imine proton donor and the terminal hydride in H(mu-H)Os-3(CO)(10)(HN=CPh2) has been investigated by X-ray analysis, NMR and IR spectroscopy and theoretical calculations. The localization of the hydrogen atoms in the crystal structure yielded a H...H distance of 1.79(6) Angstrom for this "unconventional" H...H interaction; theoretical calculations suggested an H...H distance of 1.89 Angstrom in the solid state. A NMR determination of the interproton distance, obtained from the isolation of the selective H,H dipolar contribution to the hydride relaxation time, afforded a value of 2.00 +/- 0.05 Angstrom. The difference between NMR and solid state determinations may be explained on the basis of the occurrence, in solution, of a large amplitude oscillatory motion of the imine ligand along the N-Os coordination axis. Further evidence of the presence of the favorable N-H...H-M intramolecular hydrogen bond interaction has been obtained from the red shift of the nu(N-H) stretching in H(mu-H)Os-3(CO)(10)(HN=CPh2) with respect to that of the related Os-3(CO)(11)(HN=CPh2) compound. DFT(B3LYP) calculations gave results in agreement with the experimental findings and allowed further insight into the nature of the N-H...H-M dihydrogen bond, pinpointing the electrostatic nature of this interaction and the role of the high polarizability of the Os-H bond.
Structural and spectroscopic study of the dihydrogen bond in an imine triosmium complex
AIME, Silvio;DIANA, Eliano;GOBETTO, Roberto;VITERBO, Davide
2002-01-01
Abstract
The presence of an intramolecular XH...HM interaction between the imine proton donor and the terminal hydride in H(mu-H)Os-3(CO)(10)(HN=CPh2) has been investigated by X-ray analysis, NMR and IR spectroscopy and theoretical calculations. The localization of the hydrogen atoms in the crystal structure yielded a H...H distance of 1.79(6) Angstrom for this "unconventional" H...H interaction; theoretical calculations suggested an H...H distance of 1.89 Angstrom in the solid state. A NMR determination of the interproton distance, obtained from the isolation of the selective H,H dipolar contribution to the hydride relaxation time, afforded a value of 2.00 +/- 0.05 Angstrom. The difference between NMR and solid state determinations may be explained on the basis of the occurrence, in solution, of a large amplitude oscillatory motion of the imine ligand along the N-Os coordination axis. Further evidence of the presence of the favorable N-H...H-M intramolecular hydrogen bond interaction has been obtained from the red shift of the nu(N-H) stretching in H(mu-H)Os-3(CO)(10)(HN=CPh2) with respect to that of the related Os-3(CO)(11)(HN=CPh2) compound. DFT(B3LYP) calculations gave results in agreement with the experimental findings and allowed further insight into the nature of the N-H...H-M dihydrogen bond, pinpointing the electrostatic nature of this interaction and the role of the high polarizability of the Os-H bond.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.