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

Abstract

Attempted preparation of a chelated Co II b-silylamide resulted in the unprecedented disproportionation to Co 0 and a spirocyclic cobalt(IV) bis(b-silyldiamide): [Co-[(N t Bu) 2 SiMe 2 ] 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 Co IV. Ab initio semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (À27 kcal mol À1) 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.

Manipulating metal spin states for biomimetic, catalytic and molecular materials chemistry

“…7 Other common generalisations that tetrahedral complexes are high-spin and square planar complexes low-spin, are less secure. Tetrahedral metal centres in high oxidation states [8][9][10] and/or with strong-field ligands 10,11 are sometimes low-spin. Conversely high-spin configurations occur in squareplanar chromium(II) complexes 12 and some manganese(II) tetrapyrroles.…”

Co(II) Amide, Pyrrolate, and Aminopyridinate Complexes: Assessment of their Manifold Structural Chemistry and Thermal Properties**

“…Glatz and coworkers, reacted two equivalents of Li-TMSMAPY with CoCl 2 in the presence of 4-tert-butylpyridine in THF to obtain an octahedral, mononuclear Co(II) complex, [Co-(TMSMAPY) 2 (TBUPY) 2 ], in which the TMSMAPY ligands adopted the expected chelating binding mode. [22] In a prior study Glatz and Kempe had introduced the related N 2 ,N 6 -bis(trimethylsilyl) pyridine-2,6-diamide ligand (BTMSAPY) for the complexation of Co(II). [36] They obtained a binuclear, symmetrical complex, [Co 2 (BTMSAPY) 3 ], in which both Co(II) ions were in slightly distorted tetrahedral coordination environments.…”

“…A comprehensive study was eventually motivated by our recent interest in the chemistry of Co as a potential interconnect material in microelectronics. [6,7] Even though operational modes and conditions of CVD and ALD processes differ, their complementary and precise applicability for the deposition of a broad range of thin film materials have made them industrially indispensable in fields like microelectronics, optoelectronics and photovoltaics. [8] Choosing the proper precursor is of crucial importance hereby as it requires specific thermal behavior: The precursor needs to meet demanding requirements such as high thermal stability, sufficient volatility, as well as high but controllable reactivity and stability at a surface.…”

Aryl–Cl vs heteroatom–Si bond cleavage on the route to the photochemical generation of σ,π-heterodiradicals

“…Computational analysis was carried out using DFT at the PW6B95-D3/def2-SVP level of theory incorporating the implicit contribution of methanol using the SMD solvent method [76]. PW6B95-D3 [77] is recognized as one of the best global hybrid functionals to reliably model thermochemistry, kinetics, and non-covalent interactions [78][79][80], being able to accurately predict open-shell species [81].…”