Challenges in ALD Precursor Design: Mechanism of Intramolecular C-H Activation by Internal Deprotonation of Tin(II) Precursors

Joe Goodall; Agustin Morales Aguilar; Samuel Foote; Ollie Clark; Benjamin Peek; Craig Robertson; Paul  Chalker; Claire McMullin; Andrew Johnson

doi:10.1039/d6dt01419d

Challenges in ALD Precursor Design: Mechanism of Intramolecular C-H Activation by Internal Deprotonation of Tin(II) Precursors

Joe Goodall
, Agustin Morales Aguilar
, Samuel Foote
, Ollie Clark
, Benjamin Peek
, Craig Robertson
, Paul Chalker
, Claire McMullin
, Andrew Johnson

University of Liverpool

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

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Abstract

Di(silylamido)stannylenes find application in chemical synthesis, catalysis and deposition of thin film materials. Homoleptic bis(N-alkyl-substituted-silylamido)stannylenes (i.e. [Sn{NtBu(TMS)}2], TMS = trimethylsilyl) have previously been reported to possess limited thermal stability. Here, we describe the experimental and computational investigation of the thermal decomposition of [Sn{NR(TMS)}2] [R = iPr, Cy, tBu, Ad (Ad = 1-adamantyl), CPh3] . For aliphatic N-alkyl groups, DFT calculations support an intramolecular C(sp3)–H activation by deprotonation of the TMS group via σ-bond metathesis (σBM), which forms a reactive four-membered heterocycle that is followed by disproportionation. When the N-alkyl group is substituted for the trityl group (–CPh3), the homoleptic stannylene could not be isolated, with the deprotonation of a neighbouring ortho-phenyl C(sp2)–H position via σBM occurring at room temperature. The resultant five-membered heterocyclic Sn(II) intermediate rapidly tetramerises into [Sn{κ2-Ph’CPh2N(TMS)}]4, which is stable with respect to disproportionation.

Original language	English
Pages (from-to)	11628-11635
Number of pages	8
Journal	Dalton Transactions
Volume	55
Issue number	31
Early online date	23 Jul 2026
DOIs	https://doi.org/10.1039/d6dt01419d
Publication status	Published - 11 Aug 2026

Data Availability Statement

Supplementary information (SI): full experimental and characterisation data for the complexes, including single-crystal X-ray diffraction collection and refinement details, full details of computational studies, including xyz geometries. See DOI: https://doi.org/10.1039/d6dt01419d.
CCDC 2525551–2525556 contain the supplementary crystal lographic data for this paper.66a–

Acknowledgements

Professor Michael S. Hill (University of Bath) is thanked for useful discussions. EPSRC (UK) are thanked for their support of this research (Grant No. EP/X01181X/1, A. M. and C. L. M.) and for a Prosperity Partnership with Pragmatic Semiconductor Ltd (Grant No. EP/X025195/1, J. C. G., B. J. P., P. R. C. and A. L. J.). The University of Bath are thanked for the provision of a PhD studentship to O. W. S. C. Innovate UK are thanked for their support of this research (Grant No. 511462, B. J. P. and P. R. C.). This research made use of the Anatra High Throughput Computing (HTC) service at the University of Bath. The authors gratefully acknowledge the University of Bath’s Research Computing Group (https://doi.org/10.15125/b6cd-s854) for their support in this work. This work was supported by Pegasus Chemicals, who provided funding and research facilities.

Funding

Professor Michael S. Hill (University of Bath) is thanked for useful discussions. EPSRC (UK) are thanked for their support of this research (Grant No. EP/X01181X/1, A. M. and C. L. M.) and for a Prosperity Partnership with Pragmatic Semiconductor Ltd (Grant No. EP/X025195/1, J. C. G., B. J. P., P. R. C. and A. L. J.). The University of Bath are thanked for the provision of a PhD studentship to O. W. S. C. Innovate UK are thanked for their support of this research (Grant No. 511462, B. J. P. and P. R. C.). This research made use of the Anatra High Throughput Computing (HTC) service at the University of Bath. The authors gratefully acknowledge the University of Bath's Research Computing Group ( https://doi.org/10.15125/b6cd-s854 ) for their support in this work. This work was supported by Pegasus Chemicals, who provided funding and research facilities.

Funders	Funder number
University of Bath
Pegasus Chemicals
EPSRC (UK)	EP/X025195/1, EP/X01181X/1
Innovate UK	511462

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Cite this

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title = "Challenges in ALD Precursor Design: Mechanism of Intramolecular C-H Activation by Internal Deprotonation of Tin(II) Precursors",

abstract = "Di(silylamido)stannylenes find application in chemical synthesis, catalysis and deposition of thin film materials. Homoleptic bis(N-alkyl-substituted-silylamido)stannylenes (i.e. [Sn\{NtBu(TMS)\}2], TMS = trimethylsilyl) have previously been reported to possess limited thermal stability. Here, we describe the experimental and computational investigation of the thermal decomposition of [Sn\{NR(TMS)\}2] [R = iPr, Cy, tBu, Ad (Ad = 1-adamantyl), CPh3] . For aliphatic N-alkyl groups, DFT calculations support an intramolecular C(sp3){\textendash}H activation by deprotonation of the TMS group via σ-bond metathesis (σBM), which forms a reactive four-membered heterocycle that is followed by disproportionation. When the N-alkyl group is substituted for the trityl group ({\textendash}CPh3), the homoleptic stannylene could not be isolated, with the deprotonation of a neighbouring ortho-phenyl C(sp2){\textendash}H position via σBM occurring at room temperature. The resultant five-membered heterocyclic Sn(II) intermediate rapidly tetramerises into [Sn\{κ2-Ph{\textquoteright}CPh2N(TMS)\}]4, which is stable with respect to disproportionation.",

author = "Joe Goodall and \{Morales Aguilar\}, Agustin and Samuel Foote and Ollie Clark and Benjamin Peek and Craig Robertson and Paul Chalker and Claire McMullin and Andrew Johnson",

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T1 - Challenges in ALD Precursor Design: Mechanism of Intramolecular C-H Activation by Internal Deprotonation of Tin(II) Precursors

AU - Goodall, Joe

AU - Morales Aguilar, Agustin

AU - Foote, Samuel

AU - Clark, Ollie

AU - Peek, Benjamin

AU - Robertson, Craig

AU - Chalker, Paul

AU - McMullin, Claire

AU - Johnson, Andrew

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N2 - Di(silylamido)stannylenes find application in chemical synthesis, catalysis and deposition of thin film materials. Homoleptic bis(N-alkyl-substituted-silylamido)stannylenes (i.e. [Sn{NtBu(TMS)}2], TMS = trimethylsilyl) have previously been reported to possess limited thermal stability. Here, we describe the experimental and computational investigation of the thermal decomposition of [Sn{NR(TMS)}2] [R = iPr, Cy, tBu, Ad (Ad = 1-adamantyl), CPh3] . For aliphatic N-alkyl groups, DFT calculations support an intramolecular C(sp3)–H activation by deprotonation of the TMS group via σ-bond metathesis (σBM), which forms a reactive four-membered heterocycle that is followed by disproportionation. When the N-alkyl group is substituted for the trityl group (–CPh3), the homoleptic stannylene could not be isolated, with the deprotonation of a neighbouring ortho-phenyl C(sp2)–H position via σBM occurring at room temperature. The resultant five-membered heterocyclic Sn(II) intermediate rapidly tetramerises into [Sn{κ2-Ph’CPh2N(TMS)}]4, which is stable with respect to disproportionation.

AB - Di(silylamido)stannylenes find application in chemical synthesis, catalysis and deposition of thin film materials. Homoleptic bis(N-alkyl-substituted-silylamido)stannylenes (i.e. [Sn{NtBu(TMS)}2], TMS = trimethylsilyl) have previously been reported to possess limited thermal stability. Here, we describe the experimental and computational investigation of the thermal decomposition of [Sn{NR(TMS)}2] [R = iPr, Cy, tBu, Ad (Ad = 1-adamantyl), CPh3] . For aliphatic N-alkyl groups, DFT calculations support an intramolecular C(sp3)–H activation by deprotonation of the TMS group via σ-bond metathesis (σBM), which forms a reactive four-membered heterocycle that is followed by disproportionation. When the N-alkyl group is substituted for the trityl group (–CPh3), the homoleptic stannylene could not be isolated, with the deprotonation of a neighbouring ortho-phenyl C(sp2)–H position via σBM occurring at room temperature. The resultant five-membered heterocyclic Sn(II) intermediate rapidly tetramerises into [Sn{κ2-Ph’CPh2N(TMS)}]4, which is stable with respect to disproportionation.

UR - https://www.scopus.com/pages/publications/105046026931

U2 - 10.1039/d6dt01419d

DO - 10.1039/d6dt01419d

M3 - Article

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ER -

Challenges in ALD Precursor Design: Mechanism of Intramolecular C-H Activation by Internal Deprotonation of Tin(II) Precursors

Abstract

Data Availability Statement

Acknowledgements

Funding

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