Zn-promoted C-H reductive elimination and H2 activation via a dual unsaturated heterobimetallic Ru-Zn intermediate

Fedor Miloserdov; Nasir Rajabi; John Lowe; Mary Mahon; Stuart Macgregor; Michael Whittlesey

doi:10.1021/jacs.0c01062

Zn-promoted C-H reductive elimination and H2 activation via a dual unsaturated heterobimetallic Ru-Zn intermediate

Fedor Miloserdov, Nasir Rajabi, John Lowe, Mary Mahon, Stuart Macgregor, Michael Whittlesey

Heriot-Watt University

Research output: Contribution to journal › Article › peer-review

32 Citations (SciVal)

Abstract

Reaction of [Ru(PPh ₃) ₃HCl] with LiCH ₂TMS, MgMe ₂, and ZnMe ₂ proceeds with chloride abstraction and alkane elimination to form the bis-cyclometalated derivatives [Ru(PPh ₃)(C ₆H ₄PPh ₂) ₂H][M′] where [M′] = [Li(THF) ₂] ⁺ (1), [MgMe(THF) ₂] ⁺ (3), and [ZnMe] ⁺ (4), respectively. In the presence of 12-crown-4, the reaction with LiCH ₂TMS yields [Ru(PPh ₃)(C ₆H ₄PPh ₂) ₂H][Li(12-crown-4) ₂] (2). These four complexes demonstrate increasing interaction between M′ and the hydride ligand in the [Ru(PPh ₃)(C ₆H ₄PPh ₂) ₂H] ^- anion following the trend 2 (no interaction) < 1 < 3 < 4 both in the solid-state and solution. Zn species 4 is present as three isomers in solution including square-pyramidal [Ru(PPh ₃) ₂(C ₆H ₄PPh ₂)(ZnMe)] (5), that is formed via C-H reductive elimination and features unsaturated Ru and Zn centers and an axial Z-type [ZnMe] ⁺ ligand. A [ZnMe] ⁺ adduct of 5, [Ru(PPh ₃) ₂(C ₆H ₄PPh ₂)(ZnMe) ₂][BAr ^F ₄] (6) can be trapped and structurally characterized. 4 reacts with H ₂ at-40 °C to form [Ru(PPh ₃) ₃(H) ₃(ZnMe)], 8-Zn, and contrasts the analogous reactions of 1, 2, and 3 that all require heating to 60 °C. This marked difference in reactivity reflects the ability of Zn to promote a rate-limiting C-H reductive elimination step, and calculations attribute this to a significant stabilization of 5 via Ru → Zn donation. 4 therefore acts as a latent source of 5 and this operational "dual unsaturation" highlights the ability of Zn to promote reductive elimination in these heterobimetallic systems. Calculations also highlight the ability of the heterobimetallic systems to stabilize developing protic character of the transferring hydrogen in the rate-limiting C-H reductive elimination transition states.

Original language	English
Pages (from-to)	6340-6349
Number of pages	10
Journal	Journal of the American Chemical Society
Volume	142
Issue number	13
Early online date	5 Mar 2020
DOIs	https://doi.org/10.1021/jacs.0c01062
Publication status	Published - 1 Apr 2020

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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@article{975f520f653641e8929a99ef46f57e3d,

title = "Zn-promoted C-H reductive elimination and H2 activation via a dual unsaturated heterobimetallic Ru-Zn intermediate",

abstract = "Reaction of [Ru(PPh 3) 3HCl] with LiCH 2TMS, MgMe 2, and ZnMe 2 proceeds with chloride abstraction and alkane elimination to form the bis-cyclometalated derivatives [Ru(PPh 3)(C 6H 4PPh 2) 2H][M′] where [M′] = [Li(THF) 2] + (1), [MgMe(THF) 2] + (3), and [ZnMe] + (4), respectively. In the presence of 12-crown-4, the reaction with LiCH 2TMS yields [Ru(PPh 3)(C 6H 4PPh 2) 2H][Li(12-crown-4) 2] (2). These four complexes demonstrate increasing interaction between M′ and the hydride ligand in the [Ru(PPh 3)(C 6H 4PPh 2) 2H] - anion following the trend 2 (no interaction) < 1 < 3 < 4 both in the solid-state and solution. Zn species 4 is present as three isomers in solution including square-pyramidal [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe)] (5), that is formed via C-H reductive elimination and features unsaturated Ru and Zn centers and an axial Z-type [ZnMe] + ligand. A [ZnMe] + adduct of 5, [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe) 2][BAr F 4] (6) can be trapped and structurally characterized. 4 reacts with H 2 at-40 °C to form [Ru(PPh 3) 3(H) 3(ZnMe)], 8-Zn, and contrasts the analogous reactions of 1, 2, and 3 that all require heating to 60 °C. This marked difference in reactivity reflects the ability of Zn to promote a rate-limiting C-H reductive elimination step, and calculations attribute this to a significant stabilization of 5 via Ru → Zn donation. 4 therefore acts as a latent source of 5 and this operational {"}dual unsaturation{"} highlights the ability of Zn to promote reductive elimination in these heterobimetallic systems. Calculations also highlight the ability of the heterobimetallic systems to stabilize developing protic character of the transferring hydrogen in the rate-limiting C-H reductive elimination transition states. ",

author = "Fedor Miloserdov and Nasir Rajabi and John Lowe and Mary Mahon and Stuart Macgregor and Michael Whittlesey",

year = "2020",

month = apr,

day = "1",

doi = "10.1021/jacs.0c01062",

language = "English",

volume = "142",

pages = "6340--6349",

journal = "Journal of the American Chemical Society",

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TY - JOUR

T1 - Zn-promoted C-H reductive elimination and H2 activation via a dual unsaturated heterobimetallic Ru-Zn intermediate

AU - Miloserdov, Fedor

AU - Rajabi, Nasir

AU - Lowe, John

AU - Mahon, Mary

AU - Macgregor, Stuart

AU - Whittlesey, Michael

PY - 2020/4/1

Y1 - 2020/4/1

N2 - Reaction of [Ru(PPh 3) 3HCl] with LiCH 2TMS, MgMe 2, and ZnMe 2 proceeds with chloride abstraction and alkane elimination to form the bis-cyclometalated derivatives [Ru(PPh 3)(C 6H 4PPh 2) 2H][M′] where [M′] = [Li(THF) 2] + (1), [MgMe(THF) 2] + (3), and [ZnMe] + (4), respectively. In the presence of 12-crown-4, the reaction with LiCH 2TMS yields [Ru(PPh 3)(C 6H 4PPh 2) 2H][Li(12-crown-4) 2] (2). These four complexes demonstrate increasing interaction between M′ and the hydride ligand in the [Ru(PPh 3)(C 6H 4PPh 2) 2H] - anion following the trend 2 (no interaction) < 1 < 3 < 4 both in the solid-state and solution. Zn species 4 is present as three isomers in solution including square-pyramidal [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe)] (5), that is formed via C-H reductive elimination and features unsaturated Ru and Zn centers and an axial Z-type [ZnMe] + ligand. A [ZnMe] + adduct of 5, [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe) 2][BAr F 4] (6) can be trapped and structurally characterized. 4 reacts with H 2 at-40 °C to form [Ru(PPh 3) 3(H) 3(ZnMe)], 8-Zn, and contrasts the analogous reactions of 1, 2, and 3 that all require heating to 60 °C. This marked difference in reactivity reflects the ability of Zn to promote a rate-limiting C-H reductive elimination step, and calculations attribute this to a significant stabilization of 5 via Ru → Zn donation. 4 therefore acts as a latent source of 5 and this operational "dual unsaturation" highlights the ability of Zn to promote reductive elimination in these heterobimetallic systems. Calculations also highlight the ability of the heterobimetallic systems to stabilize developing protic character of the transferring hydrogen in the rate-limiting C-H reductive elimination transition states.

AB - Reaction of [Ru(PPh 3) 3HCl] with LiCH 2TMS, MgMe 2, and ZnMe 2 proceeds with chloride abstraction and alkane elimination to form the bis-cyclometalated derivatives [Ru(PPh 3)(C 6H 4PPh 2) 2H][M′] where [M′] = [Li(THF) 2] + (1), [MgMe(THF) 2] + (3), and [ZnMe] + (4), respectively. In the presence of 12-crown-4, the reaction with LiCH 2TMS yields [Ru(PPh 3)(C 6H 4PPh 2) 2H][Li(12-crown-4) 2] (2). These four complexes demonstrate increasing interaction between M′ and the hydride ligand in the [Ru(PPh 3)(C 6H 4PPh 2) 2H] - anion following the trend 2 (no interaction) < 1 < 3 < 4 both in the solid-state and solution. Zn species 4 is present as three isomers in solution including square-pyramidal [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe)] (5), that is formed via C-H reductive elimination and features unsaturated Ru and Zn centers and an axial Z-type [ZnMe] + ligand. A [ZnMe] + adduct of 5, [Ru(PPh 3) 2(C 6H 4PPh 2)(ZnMe) 2][BAr F 4] (6) can be trapped and structurally characterized. 4 reacts with H 2 at-40 °C to form [Ru(PPh 3) 3(H) 3(ZnMe)], 8-Zn, and contrasts the analogous reactions of 1, 2, and 3 that all require heating to 60 °C. This marked difference in reactivity reflects the ability of Zn to promote a rate-limiting C-H reductive elimination step, and calculations attribute this to a significant stabilization of 5 via Ru → Zn donation. 4 therefore acts as a latent source of 5 and this operational "dual unsaturation" highlights the ability of Zn to promote reductive elimination in these heterobimetallic systems. Calculations also highlight the ability of the heterobimetallic systems to stabilize developing protic character of the transferring hydrogen in the rate-limiting C-H reductive elimination transition states.

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U2 - 10.1021/jacs.0c01062

DO - 10.1021/jacs.0c01062

M3 - Article

SN - 0002-7863

VL - 142

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EP - 6349

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

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ER -

Zn-promoted C-H reductive elimination and H2 activation via a dual unsaturated heterobimetallic Ru-Zn intermediate

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