Linear, Trinuclear Cobalt Complexes with o‐Phenylene‐bis‐Silylamido Ligands

Abstract

Transamination of [Co{N(SiMe ) } ] with C H (NHSiiPr ) gave the centrosymmetric trinuclear [{Co N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Co ] (1) (Co , Co =terminal, internal Co, respectively), with 3-coordinate Co , and Co "sandwiched" between the o-phenylenes of the two ligands; experimental and computational data support Co centres and ditopic o-amido-imino-cyclohexen-allyl ligands; magnetic studies reveal intermetallic ferromagnetic interactions and single-molecule magnet (SMM) character. One-electron reduction of 1 yielded the salt [K(18-crown-6)(THF) ][{Co N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Co ] (4) with the anion isostructural to 1. The centrosymmetric Fe complex [{Fe N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Fe ] (5), analogous to 1, was also obtained.

[2Fe–2S] Cluster Supported by Redox-Active o-Phenylenediamide Ligands and Its Application toward Dinitrogen Reduction

“…28−31 Driess and Holland reported a series of [2Fe−2S] n+ (n = 2, 1, 0) clusters supported by βdiketiminate ligands. 32,33 Remarkably, the [2Fe−2S] + clusters with diethylphenyl-substituted β-diketiminato ligands CH-[CMeN(2,6-Et 2 C 6 H 3 )] 2 are extensively delocalized, as suggested by the 57 Fe Mossbauer and X-ray absorption spectroscopy/X-ray emission spectroscopy spectroscopic data and density functional theory calculations. 32 Jones reported a diferric [2Fe−2S] 2+ cluster supported by a guanidinato ligand.…”

“…57 Fe Mossbauer Spectroscopy. All measurements for 57 Fe Mossbauer spectroscopy were performed using nonenriched solids of the as-isolated complexes. All samples were prepared in an inertatmosphere glovebox equipped with a liquid-nitrogen fill port to enable sample freezing to 77 K within the glovebox.…”

“…Each sample was loaded into a Delrin Mossbauer sample cup for measurements and loaded under liquid nitrogen. Low-temperature 57 Fe Mossbauer measurements were performed using a See Co. MS4 Mossbauer spectrometer integrated with a Janis SVT-400T He/N 2 cryostat for measurements at 80 K. Isomer shifts were determined relative to αiron at 298 K. All Mossbauer spectra were fit using the program WMoss (See Co). Errors of the fit analyses were the following: δ ± 0.02 mm s −1 and ΔE Q ± 3%.…”

“…Redox-active ligands have multiple energetically accessible oxidation states. − Their coordination to metal centers induces radical reactivity and electron reservoir behavior, which is often utilized to develop exciting new examples of catalysis. − The N,N-chelating o -phenylenediamide (pda) is a classic example of a redox-active ligand, whose coordination chemistry has been explored toward a large number of transition metals and main-group elements. − It has been clearly established that the pda ligand exists in three different redox states in coordination compounds: the closed-shell dianion, open-shell π-radical monoanion ( S = 1 / 2 ), and closed-shell neutral form. − We have been investigating the coordination chemistry of the pda ligand toward transition metals and main-group elements. − Our group is interested in coordinating redox-active pda ligands to the diferric [2Fe–2S] 2+ cluster. We envision that the resulting complex can store multiple electrons (i.e., reduction equivalents) and mediate multielectron redox processes.…”

A family of 3d metal clusters based on N–N single bonds bridged quasi-linear trinuclear cores: the Mn analogue displaying single-molecule magnet behavior

“…Typical representative includes a family of quasi-linear {Mn III 2 Ni II 3 } SMMs showing pronounced quantum tunnelling steps in hysteresis loops, 5c and a linear {Co II 3 } SMM displaying two magnetic relaxation processes at zero dc bias fields, etc. 6 Nevertheless, this species is still rare until now, except above two cases. In Mn clusters family with so many SMM members, there were only three trinuclear and one tetranuclear linear cases reported to show SMM behavior so far as we know (list in Table S1 † ).…”