Density Functional Study of N 2 Activation by Molybdenum(III) Complexes. Unusually Strong Relativistic Effects in 4d Metal Compounds
1997; American Chemical Society; Volume: 16; Issue: 5 Linguagem: Inglês
10.1021/om9607863
ISSN1520-6041
AutoresKonstantin M. Neyman, Владимир А. Наслузов, Jutta Hahn, Clark R. Landis, Notker Rösch,
Tópico(s)Catalytic Processes in Materials Science
ResumoAll-electron generalized-gradient density functional (DF) calculations have been carried out on both the nonrelativistic and relativistic levels to address the mechanism of N2 cleavage by L3Mo(III) complexes. The reaction features computed for the model reactants with L = NH2, NMe2, and Me are compared to the recently published values for the (H2N)3Mo derivative obtained with the help of the effective core potential (ECP) DF method and to the experimental data reported for the reaction of N2 with (RArN)3Mo (R = C(CD3)2CH3, Ar = 3,5-C6H3Me2). Despite a qualitative agreement between the reaction parameters of the present relativistic and the previous ECP DF calculations, some important quantitative differences are found, like a lower activation barrier by more than 10 kJ mol-1 and a higher overall reaction exothermicity by about 80 kJ mol-1. The influence of the electronic and steric properties of the ligands L on the parameters of the cleavage reaction has been analyzed. The Mo(III) trialkyl complexes, at least those with small ligands, are predicted to scissor N2 molecules less efficiently than the triamido derivatives. The relativistic effects, which are unusually large for 4d metal compounds, have been calculated and are attributed to the exceptionally strong Mo⋮N bonds.
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