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Title: Hydride oxidation from a titanium–aluminum bimetallic complex: insertion, thermal and electrochemical reactivity

Abstract

We report the synthesis and reactivity of paramagnetic heterometallic complexes containing a Ti(III)-μ-H-Al(III) moiety. Combining different stoichiometries amounts of Cp 2TiCl and KH 3AlC(TMS) 3 (Cp = cyclopentadienyl, TMS = trimethylsilyl) resulted in the formation of either bimetallic Cp 2Ti(μ-H) 2(H)AlC(TMS) 3 (2) or trimetallic (Cp 2Ti) 2(μ-H) 3(H)AlC(TMS) 3 (3) via salt metathesis pathways. While these complexes were indefinitely stable at room temperature, the bridging hydrides were readily activated upon exposure to heteroallenes, heating, or electrochemical oxidation. In each case, formal hydride oxidation occurred, but the isolated product maintained the +3 oxidation state at both metal centers. The nature of this reactivity was explored using deuterium labelling experiments and Density Functional Theory (DFT) calculations. It was found that while C–H activation from the Ti(III) bimetallic may occur through a σ-bond metathesis pathway, chemical oxidation to Ti(IV) promotes bimolecular reductive elimination of dihydrogen to form a Ti(III) product.

Authors:
 [1];  [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1399463
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 8; Journal Issue: 7; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Brown, Alexandra C., Altman, Alison B., Lohrey, Trevor D., Hohloch, Stephan, and Arnold, John. Hydride oxidation from a titanium–aluminum bimetallic complex: insertion, thermal and electrochemical reactivity. United States: N. p., 2017. Web. doi:10.1039/c7sc01835e.
Brown, Alexandra C., Altman, Alison B., Lohrey, Trevor D., Hohloch, Stephan, & Arnold, John. Hydride oxidation from a titanium–aluminum bimetallic complex: insertion, thermal and electrochemical reactivity. United States. doi:10.1039/c7sc01835e.
Brown, Alexandra C., Altman, Alison B., Lohrey, Trevor D., Hohloch, Stephan, and Arnold, John. Wed . "Hydride oxidation from a titanium–aluminum bimetallic complex: insertion, thermal and electrochemical reactivity". United States. doi:10.1039/c7sc01835e. https://www.osti.gov/servlets/purl/1399463.
@article{osti_1399463,
title = {Hydride oxidation from a titanium–aluminum bimetallic complex: insertion, thermal and electrochemical reactivity},
author = {Brown, Alexandra C. and Altman, Alison B. and Lohrey, Trevor D. and Hohloch, Stephan and Arnold, John},
abstractNote = {We report the synthesis and reactivity of paramagnetic heterometallic complexes containing a Ti(III)-μ-H-Al(III) moiety. Combining different stoichiometries amounts of Cp2TiCl and KH3AlC(TMS)3 (Cp = cyclopentadienyl, TMS = trimethylsilyl) resulted in the formation of either bimetallic Cp2Ti(μ-H)2(H)AlC(TMS)3 (2) or trimetallic (Cp2Ti)2(μ-H)3(H)AlC(TMS)3 (3) via salt metathesis pathways. While these complexes were indefinitely stable at room temperature, the bridging hydrides were readily activated upon exposure to heteroallenes, heating, or electrochemical oxidation. In each case, formal hydride oxidation occurred, but the isolated product maintained the +3 oxidation state at both metal centers. The nature of this reactivity was explored using deuterium labelling experiments and Density Functional Theory (DFT) calculations. It was found that while C–H activation from the Ti(III) bimetallic may occur through a σ-bond metathesis pathway, chemical oxidation to Ti(IV) promotes bimolecular reductive elimination of dihydrogen to form a Ti(III) product.},
doi = {10.1039/c7sc01835e},
journal = {Chemical Science},
number = 7,
volume = 8,
place = {United States},
year = {Wed May 31 00:00:00 EDT 2017},
month = {Wed May 31 00:00:00 EDT 2017}
}

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Works referenced in this record:

Aluminum hydride as a hydrogen and energy storage material: Past, present and future
journal, September 2011