Ab-initio SCF potential energy surfaces for the nucleophilic attack of hydride on coordinated carbon monoxide

Abstract

Ab-initio SCF calculations are reported for the nucleophilic addition of the hydride ion H-on the iron pentacarbonyl Fe(CO)5 complex. The stereochemistry of the attack has been established from the determination of two potential energy surfaces. The reaction is shown to be highly exothermic and with no activation barrier. This activation of CO towards the nucleophilic addition is rationalized in terms of molecular orbital interactions.

Theoretical Study of Gas-Phase Reactions of Fe(CO)5 with OH- and Their Relevance for the Water Gas Shift Reaction

“…The experimental value 18 for reaction 2 has been recently reported to be −60.8 ± 3.4 kcal mol -1 , which is in very good agreement with our calculated data. The present results are also in agreement with previous works by Dedieu and Nakamura, , where a computed SCF reaction energy of −71.3 kcal mol -1 for the same nucleophilic addition 35 and of −69.2 kcal mol -1 for the nucleophilic addition 36 of H - were reported. These authors also examined the reaction path for hydride addition and found likewise there was no barrier …”

“…Since nucleophiles are employed as cocatalysts in a variety of metal carbonyl catalyzed reactions, nucleophilic activation of coordinated CO holds considerable interest. , Despite it, there have been few detailed quantitative studies of such a common step in catalysis. , Besides the works mentioned above, , one of the most relevant studies may be that by Trautman et al., who examined the kinetics of CH 3 O - and OH - addition to Fe(CO) 5 to give the corresponding adducts. Methoxide proved to be a more powerful nucleophile than hydroxyde under comparable conditions.…”

Theoretical Studies of Some Transition-Metal-Mediated Reactions of Industrial and Synthetic Importance

“…Moreover, only indirect evidence exists that the postulated reactions should occur in the sequence 13−17 given above since these steps have only been studied individually. For instance, from a computational point of view, step 13 has been the subject of two works by Dedieu and Nakamura (DN), , where a computed SCF reaction energy of −298.3 kJ mol -1 was reported. DN also explained the high exothermicity encountered in this nucleophilic addition in terms of MOs.…”

Ab initio calculations of transition-metal organometallics: structure and molecular properties

“…A high barrier of 31 kcal/mol has been reported for MoOCHCHsHCHâ nd linked to the presence of an oxo ligand in the coordination sphere. 212 The structure of lowest energy for C14W=CH2 is a TBP with the carbene ligand in the equatorial plane. 124 The most stable conformation of the trans-Mo(CO)4(CH2)2 complex has the two carbene ligands mutually perpendicular and eclipsing the Mo-C bonds, with a rotation barrier close to 0.219 6.…”