Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

Christina M. Brammell; Emily J. Pelton; Chun Hsing Chen; Andrey A. Yakovenko; Wei Weng; Bruce M. Foxman; Oleg V. Ozerov

doi:10.1016/j.jorganchem.2011.07.017

Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

Christina M. Brammell, Emily J. Pelton, Chun Hsing Chen, Andrey A. Yakovenko, Wei Weng, Bruce M. Foxman, Oleg V. Ozerov

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Abstract

The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP = [(4-Me-2-ⁱPr ₂P-C₆H₃)₂N]). (PNP)HfCl₃ (3) was prepared via reaction of (PNP)Li (2) with HfCl₄(OEt ₂). Reactions of (PNP)HfCl₃ with alkyl Grignards led to triple alkylation to produce (PNP)HfMe₃ (4) with a small methyl or only double alkylation to give (PNP)Hf(CH₂SiMe₃) ₂Cl (5) with a larger alkyl. Structures of 3, 4, and 5 in the solid state were established by X-ray diffraction studies. Structures of the alkyl complexes 4 and 5 display remarkably irregular coordination environments about Hf, while in 3 it is approximately octahedral. Compound 4 was found to be thermally stable at 75 °C. On the other hand, thermolysis of 5 at similar conditions led to a mixture of products, the major one of which is believed to be a Hf alkylidene on the basis of in situ NMR spectroscopic observations (e.g., δ 248.2 ppm in the ¹³C{¹H} NMR spectrum).

Original language	English (US)
Pages (from-to)	4132-4137
Number of pages	6
Journal	Journal of Organometallic Chemistry
Volume	696
Issue number	25
DOIs	https://doi.org/10.1016/j.jorganchem.2011.07.017
State	Published - Dec 15 2011
Externally published	Yes

Bibliographical note

Funding Information:
We are grateful to the US National Science Foundation for support of this research through grants CHE-0809522 and CHE-0944634 to O.V.O., through support of E.J.P. as an REU participant in 2007 (grant CHE-0552767 for an REU site at Brandeis University), through support of C.M.H. as an REU participant in 2008 (grant CHE-0552767 for an REU site at Brandeis University) and 2009 (grant CHE-0755207 for an REU site at Texas A&M University), and through grant CHE-0521047 for the purchase of a new X-ray diffractometer at Brandeis University. We are also grateful for the support from the Welch Foundation (grant A-1717 to O.V.O), the Dreyfus Foundation (Camille Dreyfus Teacher-Scholar Award to O.V.O.), and the Sloan Foundation (Alfred P. Sloan Research Fellowship to O.V.O.). We thank Dr. Christos Douvris and Yanjun Zhu for help with some of the experiments in this paper.

Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.

Keywords

Alkylidene
Hafnium
Metal alkyl
Pincer
X-ray crystallography

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title = "Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation",

abstract = "The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP = [(4-Me-2-iPr 2P-C6H3)2N]). (PNP)HfCl3 (3) was prepared via reaction of (PNP)Li (2) with HfCl4(OEt 2). Reactions of (PNP)HfCl3 with alkyl Grignards led to triple alkylation to produce (PNP)HfMe3 (4) with a small methyl or only double alkylation to give (PNP)Hf(CH2SiMe3) 2Cl (5) with a larger alkyl. Structures of 3, 4, and 5 in the solid state were established by X-ray diffraction studies. Structures of the alkyl complexes 4 and 5 display remarkably irregular coordination environments about Hf, while in 3 it is approximately octahedral. Compound 4 was found to be thermally stable at 75 °C. On the other hand, thermolysis of 5 at similar conditions led to a mixture of products, the major one of which is believed to be a Hf alkylidene on the basis of in situ NMR spectroscopic observations (e.g., δ 248.2 ppm in the 13C{1H} NMR spectrum).",

keywords = "Alkylidene, Hafnium, Metal alkyl, Pincer, X-ray crystallography",

author = "Brammell, {Christina M.} and Pelton, {Emily J.} and Chen, {Chun Hsing} and Yakovenko, {Andrey A.} and Wei Weng and Foxman, {Bruce M.} and Ozerov, {Oleg V.}",

note = "Funding Information: We are grateful to the US National Science Foundation for support of this research through grants CHE-0809522 and CHE-0944634 to O.V.O., through support of E.J.P. as an REU participant in 2007 (grant CHE-0552767 for an REU site at Brandeis University), through support of C.M.H. as an REU participant in 2008 (grant CHE-0552767 for an REU site at Brandeis University) and 2009 (grant CHE-0755207 for an REU site at Texas A&M University), and through grant CHE-0521047 for the purchase of a new X-ray diffractometer at Brandeis University. We are also grateful for the support from the Welch Foundation (grant A-1717 to O.V.O), the Dreyfus Foundation (Camille Dreyfus Teacher-Scholar Award to O.V.O.), and the Sloan Foundation (Alfred P. Sloan Research Fellowship to O.V.O.). We thank Dr. Christos Douvris and Yanjun Zhu for help with some of the experiments in this paper. Copyright: Copyright 2011 Elsevier B.V., All rights reserved.",

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doi = "10.1016/j.jorganchem.2011.07.017",

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T1 - Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

AU - Brammell, Christina M.

AU - Pelton, Emily J.

AU - Chen, Chun Hsing

AU - Yakovenko, Andrey A.

AU - Weng, Wei

AU - Foxman, Bruce M.

AU - Ozerov, Oleg V.

N1 - Funding Information: We are grateful to the US National Science Foundation for support of this research through grants CHE-0809522 and CHE-0944634 to O.V.O., through support of E.J.P. as an REU participant in 2007 (grant CHE-0552767 for an REU site at Brandeis University), through support of C.M.H. as an REU participant in 2008 (grant CHE-0552767 for an REU site at Brandeis University) and 2009 (grant CHE-0755207 for an REU site at Texas A&M University), and through grant CHE-0521047 for the purchase of a new X-ray diffractometer at Brandeis University. We are also grateful for the support from the Welch Foundation (grant A-1717 to O.V.O), the Dreyfus Foundation (Camille Dreyfus Teacher-Scholar Award to O.V.O.), and the Sloan Foundation (Alfred P. Sloan Research Fellowship to O.V.O.). We thank Dr. Christos Douvris and Yanjun Zhu for help with some of the experiments in this paper. Copyright: Copyright 2011 Elsevier B.V., All rights reserved.

PY - 2011/12/15

Y1 - 2011/12/15

N2 - The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP = [(4-Me-2-iPr 2P-C6H3)2N]). (PNP)HfCl3 (3) was prepared via reaction of (PNP)Li (2) with HfCl4(OEt 2). Reactions of (PNP)HfCl3 with alkyl Grignards led to triple alkylation to produce (PNP)HfMe3 (4) with a small methyl or only double alkylation to give (PNP)Hf(CH2SiMe3) 2Cl (5) with a larger alkyl. Structures of 3, 4, and 5 in the solid state were established by X-ray diffraction studies. Structures of the alkyl complexes 4 and 5 display remarkably irregular coordination environments about Hf, while in 3 it is approximately octahedral. Compound 4 was found to be thermally stable at 75 °C. On the other hand, thermolysis of 5 at similar conditions led to a mixture of products, the major one of which is believed to be a Hf alkylidene on the basis of in situ NMR spectroscopic observations (e.g., δ 248.2 ppm in the 13C{1H} NMR spectrum).

AB - The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP = [(4-Me-2-iPr 2P-C6H3)2N]). (PNP)HfCl3 (3) was prepared via reaction of (PNP)Li (2) with HfCl4(OEt 2). Reactions of (PNP)HfCl3 with alkyl Grignards led to triple alkylation to produce (PNP)HfMe3 (4) with a small methyl or only double alkylation to give (PNP)Hf(CH2SiMe3) 2Cl (5) with a larger alkyl. Structures of 3, 4, and 5 in the solid state were established by X-ray diffraction studies. Structures of the alkyl complexes 4 and 5 display remarkably irregular coordination environments about Hf, while in 3 it is approximately octahedral. Compound 4 was found to be thermally stable at 75 °C. On the other hand, thermolysis of 5 at similar conditions led to a mixture of products, the major one of which is believed to be a Hf alkylidene on the basis of in situ NMR spectroscopic observations (e.g., δ 248.2 ppm in the 13C{1H} NMR spectrum).

KW - Alkylidene

KW - Hafnium

KW - Metal alkyl

KW - Pincer

KW - X-ray crystallography

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Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

Abstract

Bibliographical note

Keywords

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