Diverse reactivity of amidinate-supported boron centers with the hypersilyl anion and access to a monomeric secondary boron hydride

Pahar, Sanjukta, van Ingen, Yara, Babaahmadi, Rasool, Kariuki, Benson M. ORCID: https://orcid.org/0000-0002-8658-3897, Wirth, Thomas ORCID: https://orcid.org/0000-0002-8990-0667, Richards, Emma ORCID: https://orcid.org/0000-0001-6691-2377 and Melen, Rebecca L. ORCID: https://orcid.org/0000-0003-3142-2831 2024. Diverse reactivity of amidinate-supported boron centers with the hypersilyl anion and access to a monomeric secondary boron hydride. Inorganic Chemistry 63 (18) , 8302–8311. 10.1021/acs.inorgchem.4c00612

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Abstract

Diverse reactivity of the bulky tris(trimethylsilyl)silyl substituent [Si(SiMe3)3], also known as the hypersilyl group, was observed for amidinate-supported dichloro- and phenylchloroborane complexes. Treatment of the dichloroborane with potassium tris(trimethylsilyl)silyl led to the activation of the backbone β-carbon center and formation of saturated four-membered heterocyclic chloroboranes R′{Si(SiMe3)3}C(NR)2BCl [R′ = Ph, R = Cy (3); R′ = Ph, R = iPr (6); R′ = tBu, R = Cy (8)], whereas the four-membered amidinate hypersilyl-substituted phenyl borane 4 {PhC(NCy)2B(Ph)[Si(SiMe3)3]} was observed for the case of an amidinate-supported phenylchloroborane. The highly deshielded 11B NMR spectroscopic resonance and the distinct difference in the 29Si NMR spectrum confirmed the presence of a σ-donating hypersilyl effect on compounds 3, 6, and 8. Reaction of 3 with the Lewis acid AlCl3 led to the formation of complex 11 in which an unusual cleavage of one of the C–N bonds of the amidinate backbone is observed. Nucleophilic substitution at the boron center of saturated chloroborane 3 with phenyllithium generated the phenylborane derivative 12, whereas the secondary monomeric boron hydride 13 was observed after treatment with alane (AlH3). All compounds (2–13) have been fully characterized by NMR spectroscopy and single-crystal X-ray structure determination studies.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Publisher:	American Chemical Society
ISSN:	0020-1669
Funders:	Leverhulme Trust and Royal Society
Date of First Compliant Deposit:	3 May 2024
Date of Acceptance:	8 April 2024
Last Modified:	07 May 2024 13:30
URI:	https://orca.cardiff.ac.uk/id/eprint/168706

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