Experimental determination of the equilibrium isotope effect for the dihydride/dihydrogen tautomerism (EIET) in the Kubas complex W(CO)3(PCy3)2(η2-H2) has not yet been achieved because of the lack of vibrational frequencies for the dihydride form. Even so, Bender, Kubas, Hoff, and co-workers3 have estimated a normal EIET, which predicts that deuterium favors the classical site at 300 K. In this work, EIET for the Kubas complex tautomerism is theoretically studied by using two levels of calculation. First, the standard harmonic oscilator approach is used to obtain the harmonic partition functions and the corresponding harmonic EIET, which turns out to be inverse (0.485 at 300 K). Next, anharmonicity is included in some normal modes in order to obtain an improved EIET. Following a new scheme developed by our group in a previous work,5 DVR nuclear calculations over bidimensional potential energy surfaces are employed to obtain the associated anharmonic partition functions and the corresponding anharmonic EIET, which turns out to be also inverse (0.534 at 300 K). So, theoretical corrected EIET predicts that deuterium favors the nonclassical site at 300 K. © 2001 American Chemical Society.
|Journal||J. Phys. Chem. A|
|Publication status||Published - 17 May 2001|