A computational investigation of the role of the iridium dihydrogen pincer complex in the formation of the cyclic pentamer (NH 2BH 2) 5

Kamalika Ghatak; Kumar Vanka

doi:10.1016/j.comptc.2012.04.020

A computational investigation of the role of the iridium dihydrogen pincer complex in the formation of the cyclic pentamer (NH ₂BH ₂) ₅

Kamalika Ghatak, Kumar Vanka

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

16 Scopus citations

Abstract

Computational studies with density functional theory (DFT) and MP2 have been done to investigate the interaction between the iridium dihydrogen pincer complex: (POCOP)IrH ₂ (where POCOP=η ³-1,3(OPtBu ₂) ₂C ₆H ₃) and NH ₂BH ₂, the immediate product of ammonia borane (NH ₃BH ₃) dehydrogenation. A mechanism has been proposed for an oligomerisation process at the metal centre that involves competition between (i) insertion of an NH ₂BH ₂ molecule into the (NH ₂BH ₂) _n chain and (ii) termination of the chain leading to the formation of the cyclic (NH ₂BH ₂) _n oligomer. The calculated ΔG values show that the competition favours insertion over termination for the cases n=1 to n=4 but favours termination for n=5. The computational studies therefore indicate that the cyclic pentamer (NH ₂BH ₂) ₅ would be formed during NH ₃BH ₃ dehydrogenation by the (POCOP)IrH ₂ catalyst, agreeing with experimental findings. The mechanistic understanding gained has implications for the facile regeneration of ammonia borane.

Original language	English (US)
Pages (from-to)	18-29
Number of pages	12
Journal	Computational and Theoretical Chemistry
Volume	992
DOIs	https://doi.org/10.1016/j.comptc.2012.04.020
State	Published - Jul 15 2012
Externally published	Yes

All Science Journal Classification (ASJC) codes

Biochemistry
Condensed Matter Physics
Physical and Theoretical Chemistry

Keywords

Ammonia borane
Hydrogen storage
Iridium pincer ligand catalyst
Mechanistic studies
Oligomerisation cycle

Access to Document

10.1016/j.comptc.2012.04.020

Cite this

@article{79be65f86ae94ebd8adc382521309864,

title = "A computational investigation of the role of the iridium dihydrogen pincer complex in the formation of the cyclic pentamer (NH 2BH 2) 5 ",

abstract = "Computational studies with density functional theory (DFT) and MP2 have been done to investigate the interaction between the iridium dihydrogen pincer complex: (POCOP)IrH 2 (where POCOP=η 3-1,3(OPtBu 2) 2C 6H 3) and NH 2BH 2, the immediate product of ammonia borane (NH 3BH 3) dehydrogenation. A mechanism has been proposed for an oligomerisation process at the metal centre that involves competition between (i) insertion of an NH 2BH 2 molecule into the (NH 2BH 2) n chain and (ii) termination of the chain leading to the formation of the cyclic (NH 2BH 2) n oligomer. The calculated ΔG values show that the competition favours insertion over termination for the cases n=1 to n=4 but favours termination for n=5. The computational studies therefore indicate that the cyclic pentamer (NH 2BH 2) 5 would be formed during NH 3BH 3 dehydrogenation by the (POCOP)IrH 2 catalyst, agreeing with experimental findings. The mechanistic understanding gained has implications for the facile regeneration of ammonia borane.",

keywords = "Ammonia borane, Hydrogen storage, Iridium pincer ligand catalyst, Mechanistic studies, Oligomerisation cycle",

author = "Kamalika Ghatak and Kumar Vanka",

year = "2012",

month = jul,

day = "15",

doi = "10.1016/j.comptc.2012.04.020",

language = "English (US)",

volume = "992",

pages = "18--29",

journal = "Computational and Theoretical Chemistry",

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AU - Ghatak, Kamalika

AU - Vanka, Kumar

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Y1 - 2012/7/15

N2 - Computational studies with density functional theory (DFT) and MP2 have been done to investigate the interaction between the iridium dihydrogen pincer complex: (POCOP)IrH 2 (where POCOP=η 3-1,3(OPtBu 2) 2C 6H 3) and NH 2BH 2, the immediate product of ammonia borane (NH 3BH 3) dehydrogenation. A mechanism has been proposed for an oligomerisation process at the metal centre that involves competition between (i) insertion of an NH 2BH 2 molecule into the (NH 2BH 2) n chain and (ii) termination of the chain leading to the formation of the cyclic (NH 2BH 2) n oligomer. The calculated ΔG values show that the competition favours insertion over termination for the cases n=1 to n=4 but favours termination for n=5. The computational studies therefore indicate that the cyclic pentamer (NH 2BH 2) 5 would be formed during NH 3BH 3 dehydrogenation by the (POCOP)IrH 2 catalyst, agreeing with experimental findings. The mechanistic understanding gained has implications for the facile regeneration of ammonia borane.

AB - Computational studies with density functional theory (DFT) and MP2 have been done to investigate the interaction between the iridium dihydrogen pincer complex: (POCOP)IrH 2 (where POCOP=η 3-1,3(OPtBu 2) 2C 6H 3) and NH 2BH 2, the immediate product of ammonia borane (NH 3BH 3) dehydrogenation. A mechanism has been proposed for an oligomerisation process at the metal centre that involves competition between (i) insertion of an NH 2BH 2 molecule into the (NH 2BH 2) n chain and (ii) termination of the chain leading to the formation of the cyclic (NH 2BH 2) n oligomer. The calculated ΔG values show that the competition favours insertion over termination for the cases n=1 to n=4 but favours termination for n=5. The computational studies therefore indicate that the cyclic pentamer (NH 2BH 2) 5 would be formed during NH 3BH 3 dehydrogenation by the (POCOP)IrH 2 catalyst, agreeing with experimental findings. The mechanistic understanding gained has implications for the facile regeneration of ammonia borane.

KW - Ammonia borane

KW - Hydrogen storage

KW - Iridium pincer ligand catalyst

KW - Mechanistic studies

KW - Oligomerisation cycle

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