A Pair of Cobalt(III/IV) Terminal Imido Complexes

Abstract

The reaction of the cobalt(I) complex [(TIMMN mes )Co I ](BPh 4 )(2)(TIMMN mes = tris-[2-(3-mesitylimidazolin-2-ylidene)methyl]amine) with 1-adamantylazide yields the cobalt(III) imido complex [(TIMMN mes )Co III -(NAd)](BPh 4 )( 3)w ith concomitant release of dinitrogen. The N-anchor in diamagnetic 3 features an unusual, planar tertiary amine,w hich results from repulsive electrostatic interaction with the filled d(z 2 )-orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups.O ne-electron oxidation of 3 with [FeCp 2 ](OTf) provides access to the rare,h igh-valent cobalt(IV) imido complex [(TIMMN mes )Co IV (NAd)](OTf) 2 (4). Despite ah alflife of less than 1hat room temperature, 4 could be isolated at low temperatures in analytically pure form. Single-crystal Xray diffractometry and EPR spectroscopyc orroborate the molecular structure and the d 5 low-spin, S = 1 = 2 ,e lectron configuration. Ac omputational analysis of 4 suggests high covalency within the Co IV =NAdbond with non-negligible spin density located at the imido moiety,w hicht ranslates into substantial triplet nitrene character.

Between imide, imidyl and nitrene – an imido iron complex in two oxidation states

“…1 , left) oxidation led to a switch from the high-spin to the low-spin configuration (d 5 , S = 1/2). 9 For a trigonal planar dipyrromethane (dpm) based imido iron complex ( Fig. 1 , right) the high-spin state persisted, with an increase of the coordination number.…”

On the Synthesis of a T‐Shaped Imido Nickel Complex and Trigonal Amido Nickel Complexes

“…Thereby it shows that more intriguing bonding situations in such imido metal complexes, that deviates from the classic description as an [NR] 2− unit bound to a M n+2 ion, are increasingly found [18,19] . These encompass for iron, [11] cobalt [20,21] and nickel [16,22,23] very few examples of complexes with a metal bound imidyl [NR] − unit as well as an isolated and putative copper(I) nitrene species [24] …”

“…[11][12][13][14][15][16][17] Thereby it shows that more intriguing bonding situations in such imido metal complexes, that deviates from the classic description as an [NR] 2À unit bound to a M n + 2 ion, are increasingly found. [18,19] These encompass for iron, [11] cobalt [20,21] and nickel [16,22,23] very few examples of complexes with a metal bound imidyl [NR] À unit as well as an isolated and putative copper(I) nitrene species. [24] Taking a closer look at nickel, only a small number of isolable, structurally identified imido nickel complexes are known, all in a low-coordinate environment (coordination number � 3).…”

Chemo-selective Aziridination and Oxyamination of Alkenes with Nano-cobalt catalyst

“…The FTIR spectroscopy of the recycled catalyst from scheme 8a hinted the presence of cobalt imido or cobalt nitride species. 18 In order to verify the possible hydroamination intermediate pathway, compound 12 was prepared and subjected to the optimal conditions, however, 3a was not formed no matter with or without DPH, which ruled out the tandem hydroamination/intramolecular cyclization route (Scheme 8, c). Deuterated experiment employing 4-methylstyrene-d3 (13) as substrate afforded the product 14 with 78% yield, all deuterium stayed intact and no hydrogen-deuterium exchange was found (Scheme 8, d).…”