A Rare Low-Spin CoIV Bis(β-silyldiamide) with High Thermal Stability: Steric Enforcement of a Doublet Configuration

Zanders, D. and Bačić, G. and Leckie, D. and Odegbesan, O. and Rawson, J. and Masuda, J.D. and Devi, A. and Barry, S.T.

Volume: 59 Pages: 14138-14142
DOI: 10.1002/anie.202001518
Published: 2020

Attempted preparation of a chelated CoII β-silylamide resulted in the unprecedented disproportionation to Co0 and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibited a room-temperature magnetic moment of 1.8 B.M. and a solid-state axial EPR spectrum diagnostic of a rare S=1/2 configuration for tetrahedral CoIV. Ab initio semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (−27 kcal mol−1) over higher spin configurations only for the bulky tert-butyl-substituted analogue. Unlike other CoIV complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in preliminary atomic layer deposition (ALD) surface saturation experiments. The ease of synthesis and high stability make 1 an attractive starting point to investigate otherwise inaccessible CoIV intermediates and for synthesizing new materials. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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