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Dynamic behavior of hydrogen in transition metal bis(silyl) hydride complexes

A series of rhodium complexes CpRh(SiMe2X)2(SiMe 3)(H) (X = Me, Cl, Br, I), Cp1-Cp4, CpRh(SiMe2X) 2(PMe3)(H)+ (X = Me, Cl, Br, I), Cp5-Cp8, CpRh(SiMe3)2(SiF3)(H), Cp9, CpRh(SiMe 3)2(SiH3)(H), Cp10, TpRh(SiH3) 2(SiMe3)(H), Tp1, TpRh(SiH3) 2(PMe3)(H)+, Tp2, and TpRh(SiF 3)2(PMe3)(H)+, Tp3, were studied computationally to understand the hydrogen behavior in the Si·· ·H···Si moiety. The hydride ligand interacts with at least one of the silyls, and in many cases with both, but is located asymmetrically with regard to them, giving rise to a double-well potential energy surface (PES) for hydrogen motion. The hydrogen transfer barriers ΔE vary from 0.03 to 3 kcal·mol-1. For selected complexes Tp1, Tp2, Tp3, and Cp9 the three-dimensional PESs were constructed and the vibrational Schrödinger equation was solved. The PES is highly anharmonic in all four cases. The hydrogen is delocalized between two silicons in complexes Tp1, Tp3, and Cp9, but localized around the energy minima in complex Tp2. Complex Tp3 is an intermediate case with a substantial tunneling. The delocalized behavior is pertinent to systems with ΔE < 0.25 kcal·mol-1. For complexes Tp1, Tp2, Tp3, and Cp9 the J(Si-H) spin-spin coupling constants were calculated taking into account the vibrational motion of hydride. For Tp1, Tp3, and Cp9 both J(Si1-H) and J(Si 2-H) are negative due to simultaneous Si 1···H···Si2 interactions, while for Tp2J(Si2-H) is positive, indicating a single Si···H interaction only. Negative J(Si-H) values were obtained even for Si···H distances as large as 2.3 Å (complex Tp3). A possible effect of vibrations on the J(Si-H) values is also discussed

We are grateful to Professor G. I. Nikonov of Brock University, Canada, for a stimulating discussion. Financial support from the Spanish Ministerio de Ciencia e Innovacion (grant CTQ2011-23156/BQU) and the European Fund for Regional Development (grant UNGI08-4E-003) is gratefully appreciated

© Organometallics, 2013, vol. 32, núm. 2, p. 514-526

American Chemical Society (ACS)

Author: Horbatenko, Yevhen
Vyboishchikov, Sergei F.
Date: 2013 January 28
Abstract: A series of rhodium complexes CpRh(SiMe2X)2(SiMe 3)(H) (X = Me, Cl, Br, I), Cp1-Cp4, CpRh(SiMe2X) 2(PMe3)(H)+ (X = Me, Cl, Br, I), Cp5-Cp8, CpRh(SiMe3)2(SiF3)(H), Cp9, CpRh(SiMe 3)2(SiH3)(H), Cp10, TpRh(SiH3) 2(SiMe3)(H), Tp1, TpRh(SiH3) 2(PMe3)(H)+, Tp2, and TpRh(SiF 3)2(PMe3)(H)+, Tp3, were studied computationally to understand the hydrogen behavior in the Si·· ·H···Si moiety. The hydride ligand interacts with at least one of the silyls, and in many cases with both, but is located asymmetrically with regard to them, giving rise to a double-well potential energy surface (PES) for hydrogen motion. The hydrogen transfer barriers ΔE vary from 0.03 to 3 kcal·mol-1. For selected complexes Tp1, Tp2, Tp3, and Cp9 the three-dimensional PESs were constructed and the vibrational Schrödinger equation was solved. The PES is highly anharmonic in all four cases. The hydrogen is delocalized between two silicons in complexes Tp1, Tp3, and Cp9, but localized around the energy minima in complex Tp2. Complex Tp3 is an intermediate case with a substantial tunneling. The delocalized behavior is pertinent to systems with ΔE < 0.25 kcal·mol-1. For complexes Tp1, Tp2, Tp3, and Cp9 the J(Si-H) spin-spin coupling constants were calculated taking into account the vibrational motion of hydride. For Tp1, Tp3, and Cp9 both J(Si1-H) and J(Si 2-H) are negative due to simultaneous Si 1···H···Si2 interactions, while for Tp2J(Si2-H) is positive, indicating a single Si···H interaction only. Negative J(Si-H) values were obtained even for Si···H distances as large as 2.3 Å (complex Tp3). A possible effect of vibrations on the J(Si-H) values is also discussed
We are grateful to Professor G. I. Nikonov of Brock University, Canada, for a stimulating discussion. Financial support from the Spanish Ministerio de Ciencia e Innovacion (grant CTQ2011-23156/BQU) and the European Fund for Regional Development (grant UNGI08-4E-003) is gratefully appreciated
Format: application/pdf
ISSN: 0276-7333 (versió paper)
1520-6041 (versió electrònica)
Document access: http://hdl.handle.net/10256/11401
Language: eng
Publisher: American Chemical Society (ACS)
Collection: MICINN/PN 2012-2014/CTQ2011-23156
Reproducció digital del document publicat a: http://dx.doi.org/10.1021/om300981y
Articles publicats (D-Q)
Is part of: © Organometallics, 2013, vol. 32, núm. 2, p. 514-526
Rights: Tots els drets reservats
Subject: Enllaços d’hidrogen
Hydrogen bonding
Lligands
Ligands
Title: Dynamic behavior of hydrogen in transition metal bis(silyl) hydride complexes
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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