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Synthesis of Singly and Doubly Bridgedansa-Zirconocene Hydrides. Formation of an Unusual Mixed Valence Trimeric Hydride by Reaction of H_2 with {(Me_2Si)_2(η^5-C_5H_3)_2}Zr(CH_3)_2and Generation of a Dinitrogen Complex by Reaction of N_2 with a Zirconocene Dihydride

Chirik, Paul J. and Henling, Lawrence M. and Bercaw, John E. (2001) Synthesis of Singly and Doubly Bridgedansa-Zirconocene Hydrides. Formation of an Unusual Mixed Valence Trimeric Hydride by Reaction of H_2 with {(Me_2Si)_2(η^5-C_5H_3)_2}Zr(CH_3)_2and Generation of a Dinitrogen Complex by Reaction of N_2 with a Zirconocene Dihydride. Organometallics, 20 (3). pp. 534-544. ISSN 0276-7333. https://resolver.caltech.edu/CaltechAUTHORS:20170808-074543551

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Abstract

A series of singly and doubly bridged ansa-zirconocene dihydride complexes has been prepared from hydrogenation of the corresponding dimethyl complexes. For the singly [SiMe_2]-bridged species, the hydrogenation reaction is facile at 25 °C, whereas for the doubly [SiMe_2]-bridged complexes hydrogenation occurs over the course of days at 87 °C. Hydrogenation of {meso-Me_2Si(η^5-C_5H_3-3-CMe_3)_2}ZrMe_2 affords the isomeric dimeric dihydrides [{meso-Me_2Si(η^5-C_5H_3-3-CMe_3)_2}ZrH]_2(μ_2-H)_2, one of which has been characterized by X-ray diffraction. The racemo isomer of Me_2Si(η^5-C_5H_2-2-SiMe_3-4-CMe_3)_2ZrMe_2 (BpZrMe_2) reacts with dihydrogen, affording the first example of a monomeric ansa-zirconocene dihydride, {rac-Me_2Si(η^5-C_5H_2-2-SiMe_3-4-CMe_3)_2}ZrH_2 (rac-BpZrH_2). In the presence of dinitrogen, rac-BpZrH_2 undergoes thermal reductive elimination of H_2 and reaction with N_2, yielding the dinitrogen complex BpZr(μ_2,η^2,η^2-N_2)ZrBp, for which the dinitrogen ligand is coordinated in a side-on fashion to both zirconiums with a N−N bond distance of 1.241(3) Å. The doubly [SiMe_2]-bridged zirconium dimethyl complex {(Me_2Si)_2(η^5-C_5H_3)_2}ZrMe_2 (RpZrMe_2) undergoes hydrogenation under forcing conditions, affording the mixed valent (Zr(IV)/Zr(IV)/Zr(III)) hydride trimer [RpZr]_3(μ_3-H)_2(μ_2-H)_3, which has been characterized by X-ray diffraction. More substituted doubly [SiMe_2]-bridged zirconocene dihydrides such as [{(Me_2Si)_2(η^5-C_5H-3,5-(CHMe_2)_2)(η^5-C_5H_2-4-CHMeEt}ZrH]_2(μ_2-H)_2 ([sec-BuThpZrH]_2(μ_2-H)_2) and [(Me_2Si)_2(η^5-C_5H-2,4-(CHMe_2)_2)(η^5-C_5H_2-4-CHMe_2)ZrH]_2(μ_2-H)_2 ([^iPrThpZrH]_2(μ_2-H)_2) have been prepared and shown to be robust dimers in solution.


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http://dx.doi.org/10.1021/om000739hDOIArticle
http://pubs.acs.org/doi/abs/10.1021/om000739hPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/om000739hPublisherSupporting Information
Additional Information:© 2001 American Chemical Society. Received 23 August 2000. Published online 11 January 2001. Published in print 1 February 2001. This work has been supported by USDOE Office of Basic Energy Sciences (Grant NO. DE-FG03-85ER13431) and Exxon Chemicals America. We wish to thank Dr. Chris Jones for assistance in acquiring the FT-Raman spectra. The authors thank Professor Ged Parkin (Columbia University) for very helpful suggestions concerning the X-ray structure determination for 5.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-85ER13431
Exxon Chemicals AmericaUNSPECIFIED
Issue or Number:3
Record Number:CaltechAUTHORS:20170808-074543551
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170808-074543551
Official Citation:Synthesis of Singly and Doubly Bridged ansa-Zirconocene Hydrides. Formation of an Unusual Mixed Valence Trimeric Hydride by Reaction of H2 with {(Me2Si)2(η5-C5H3)2}Zr(CH3)2 and Generation of a Dinitrogen Complex by Reaction of N2 with a Zirconocene Dihydride Paul J. Chirik, Lawrence M. Henling, and John E. Bercaw Organometallics 2001 20 (3), 534-544 DOI: 10.1021/om000739h
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79904
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 Aug 2017 20:40
Last Modified:03 Oct 2019 18:25

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