Title

Activation and Cleavage of H-R Bonds through Intermolecular H...H Bonding upon Reaction of Proton Donors HR with 18-Electron Transition Metal Hydrides

Document Type

Article

Journal/Book Title

Journal of Physical Chemistry

Publication Date

1999

Publisher

American Chemical Society

Volume

103

Issue

4

First Page

514

Last Page

520

DOI

10.1021/jp9827779

Abstract

The H−R cleavage upon reaction MH + HR → MH···HR → M(η2-H2)R, where MH represents 18-e trans-dihydrides Ru(H)(H)(PH2CH2PH2)2 (1), Ru(H)(H)(PH3)4 (2), Ru(H)(H)(NH3)4 (3); HR are HX (X = F, Cl) and HOR (R = H, CH3) is studied using the DFT B3PW91/LANL2DZ level of theoretical calculations. The H−R bond splits upon interaction of the HR with 1 and 3 which possess a hydride H of high proton attracting power and significantly electropositive H of PH2 and NH3 groups. The basicity of the transition metal plays only a minor role in H−R splitting. The H−R cleavage proceeds via transfer of the H atom from R to hydride H in Ru−H···H−R···H−P(N), as an exothermic process without barrier or H···H intermediate. The less acidic HOR yields a multi-H-bonded intermediate Ru−H···H−O···(H−P(N))2, where the H−O bond cleaves with a low barrier. Such an energetically facile mechanism of H−R splitting was not found for 2, where H of PH3 is too inert to interact with R and a multi-H-bonded complex is not formed. The computed relative energies and barriers are in agreement with available experimental data.

Comments

Originally published by American Chemical Society in the Journal of Physical Chemistry.

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