Dual Routes toward Observation of a trans-H2/Hydride Complex in an Iridium Pincer System and Hydrogenation Catalytic Activity

Agrawal, NK and Dash, SR and Vanka, K and Jagirdar, BR (2022) Dual Routes toward Observation of a trans-H2/Hydride Complex in an Iridium Pincer System and Hydrogenation Catalytic Activity. In: Organometallics .

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Abstract

Abstraction of chloride from a six-coordinate complex, trans-Ir(H)(Cl)(iPr)4(POCOP)(PPh3) (1) (iPr)4(POCOP) = 2,6-bis(di-iso-propylphosphinito)benzene, κ3-C6H3-1,3-OP(iPr)2]2], using NaBAr4f leads to the generation of a dinitrogen complex, trans-Ir(H)(N2)(iPr)4(POCOP)(PPh3)BAr4f (6). Addition of H2 to Ir(H)(N2)(iPr)4(POCOP)(PPh3)+ (6) under extremely mild conditions (1 bar, 298 K) resulted in the reversible coordination of H2 to generate the cis-Ir(H)(η2-H2)(iPr)4(POCOP)(PPh3)+ (cis-11) complex. The cis-Ir(H)(η2-H2)(iPr)4(POCOP)(PPh3)+ complex (cis-11) isomerized to a trans isomer, trans-Ir(H)(η2-H2)(iPr)4(POCOP)(PPh3)+ (trans-11), at 253 K. The isomerization process has been studied and supported by computations. Employing an alternative route, protonation of the trans-Ir(H)2(iPr)4(POCOP)(PPh3) complex (2) at 183 K resulted in the formation of an identical, trans-Ir(H)(η2-H2)(iPr)4(POCOP)(PPh3)+ complex (trans-11); upon warming the sample, the trans-H2/hydride complex isomerized to the cis isomer above 253 K. Two independent routes to obtain trans-Ir(H)(η2-H2)(iPr)4(POCOP)(PPh3)+ (trans-11) species have been established. Reaction of trans-Ir(H)(N2)(iPr)4(POCOP)(PPh3)BAr4f (6) with C2H4 gave the cis-Ir(H)(η2-C2H4)(iPr)4(POCOP)(PPh3)+ complex (cis-15), which also undergoes isomerization to yield an equilibrium mixture of cis/trans-Ir(H)(η2-C2H4)(iPr)4(POCOP)(PPh3)+ complexes (cis-15 and trans-15) at 253 K. The trans-Ir(H)(N2)(iPr)4(POCOP)(PPh3)+ complex (6) is an excellent catalyst for hydrogenation of ethylene to ethane under very mild conditions. © 2023 American Chemical Society.

Item Type:	Journal Article
Publication:	Organometallics
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	17 Mar 2023 09:53
Last Modified:	17 Mar 2023 09:53
URI:	https://eprints.iisc.ac.in/id/eprint/81034

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