A Dicobalt Coordination Complex with a Short Cobalt‐Cobalt Distance

Abstract

The existence of a metal‐metal bond in organometallic and coordination complexes is a very important aspect. Metal‐carbonyl, carbene‐metal‐carbonyl and metal‐carbene complexes were studied for having this feature. Herein, an air stable dark green color dicobalt coordination complex [Co(III)2(hep)3(N3)3] (1) [hepH = 2‐(2‐ethylhydroxy)pyridine] with three μ‐alkoxide bridges has been synthesized and characterized by X‐ray single crystal diffraction, NMR and UV/vis spectroscopy. Complex 1 has a short Co⋅⋅⋅Co distance (2.595(6) Å) and thus it has been studied by theoretical calculations. QTAIM (quantum theory of atoms in molecules) as well as EDA‐NOCV analysis (energy decomposition analysis ‐ natural orbitals for chemical valence) do not indicate any significant metal‐metal interaction. The bonding in 1 can be best represented by the interaction of two alkokxy bridged valence electrons fragment Co(III)(hep)2N3 (3d6) with Co(III)(hep)(N3)2 (3d6) where the donation of the lone pair of electrons from three bridging Ohep‐atoms stabilizes the dinuclear Co(III) complex. Additionally, thermolysis of 1 at 550 oC led to the formation sponge like Co3O4 oxide.

[Co(NHC)(CO)3]: Isolation and Reactivity Study of a Model 17-Electron Species in the Oxo Process

“…To the best of our knowledge, complex 5 is the first isolable analogue of [Co 2 (CO) 6 ] molecule proposed to form upon UV irradiation of Co 2 (CO) 8 in an argon matrix 32 and studied theoretically. 33 The Co−Co distance of 2.4273(2) Å in 5 is among the shortest reported Co−Co distances 34 but is significantly longer (0.17−0.19 Å) than the value calculated for the Co−Co distance of [Co 2 (CO) 6 ]. 33 The formal Co−Co bond order in 5 and [Co 2 (CO) 6 ] can be 1 or 3 based on bond notations proposed by Perkin et al 35 The 1 H and 13 C{ 1 H} NMR spectra of 4 shows characteristic imidazolium singlet proton signal at 8.43 ppm and a Co(CO) 4 carbonyl 13 C signal centered at 215.84 ppm as broad eight peaks due to coupling to the S = 7/ 2, 59 Co nucleus ( 2 J CCo = 280.3 Hz).…”

Slow relaxation of the magnetization in two cobalt(iii)/cobalt(ii) dimers

“…The intramolecular Co1⋯Co2 and Co3⋯Co4 distances (3.006(1) and 2.989(1) Å, respectively) are also similar to those observed in 1 and in other related systems. 43–45…”

“…These values are similar to those found in other analogous systems. [43][44][45] The dimer 1B shows a very similar geometry but now the Co II centre (Co4) is coordinated axially by a Cl À anion instead of a terminal N 3 À anion (Fig. 1b).…”

“…The intramolecular Co1Á Á ÁCo2 and Co3Á Á ÁCo4 distances (3.006(1) and 2.989(1) Å, respectively) are also similar to those observed in 1 and in other related systems. [43][44][45] Compound 2 also shows the presence of several H-bonds connecting dimers 2A and 2B. Thus, the hydrogen atom, (H1N) of the imine nitrogen (N1) forms a N-HÁ Á ÁO interaction with an oxygen atom (O24A), of the non-coordinated ClO 4 À anion.…”