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

: Attempted preparation of a chelated Co(II) β -silylamide resulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis( β -silyldiamide): [Co[(N t Bu) 2 SiMe 2 ] 2 ] ( 1 ). Compound 1 exhibits 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 Co(IV). Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (-27 kcal/mol) over higher spin configurations only for the bulky tert-butyl substituted analogue. Unlike other Co(IV) 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 Co(IV) intermediates and for synthesizing new materials.