Synthesis and Characterization of Tetrahedral and Square Planar Bis(iminopyrrolyl) Complexes of Cobalt(II)

Abstract

A series of 2-iminopyrrole ligand precursors with increasing bulkiness [HNC4H3C(R)=N-2,6-R'2C6H3] (R = R' = H, 1a; R = Me, R'= H, 1b; R = H, R' = Me, 1c; R = R' = Me, 1d; R = H, R' = iPr, 1e; R = Me, R' = iPr, 1f) were synthesized and deprotonated with NaH to give the corresponding iminopyrrolyl sodium salts 2a-f. A set of homoleptic bis-ligand Co(II) complexes of the type [Co(kappa2N,N'-NC4H3C(R)=N-2,6-R'2C6H3)2] (R = R'= H, 3a; R = Me, R'= H, 3b; R = H, R' = Me, 3c; R = R' = Me, 3d; R = H, R' = iPr, 3e; R = Me, R' = iPr, 3f) was prepared by reaction of CoCl2 with the corresponding iminopyrrolyl sodium salts 2a-f. The new complexes were characterized by elemental analysis, magnetic susceptibility measurements, in powder and in solution, UV/vis/NIR, and, in some cases, X-ray crystallography. According to X-ray diffraction and magnetic measurements, the Co complexes 3a-e proved to be tetrahedral, which is the preferred geometry for Co(II) compounds. However, a square planar geometry is observed in the case of 3f, as determined by several characterization techniques. In this case, DFT calculations suggest the square planar geometry is slightly more stable than the tetrahedral one probably due to a combination of steric and electronic reasons.

High‐Spin Square‐Planar CoII and FeII Complexes and Reasons for Their Electronic Structure

“…These values are also consistent with those observed for the reported {CoN 4 } [12,17,32] [33] The decrease below 75 K is likely due to zero-field splitting and not a spin-state change. The small kink in the c M T values at approximately 260 K does not occur for powdered samples encased in eicosane ( Figure S3).…”

Cobalt(II) phenoxy‐imine complexes in radical polymerization of vinyl acetate: The interplay of catalytic chain transfer and controlled/living radical polymerization

“…The effective magnetic moment ( μ eff ) of complex 1a in the solid state was measured by a SQUID magnetometer as a relatively constant value of 4.21 μ B from 50 to 300 K (Supporting Information Fig. S10b), indicating a spin‐only tetrahedral cobalt(II) complex . The high‐spin electron configuration of complex 1a was demonstrated by S = 3/2 calculated from associated with g = 2.0010 and μ eff = 4.21.…”

Luminescent Di‐ and Trinuclear Boron Complexes Based on Aromatic Iminopyrrolyl Spacer Ligands: Synthesis, Characterization, and Application in OLEDs

“…In general, the linear bis(iminopyrrole) ligand precursors, 1,2‐(HNC 4 H 3 ‐C(H)N) 2 ‐C 6 H 4 ( 2 ), 1,3‐(HNC 4 H 3 ‐C(H)N) 2 ‐C 6 H 4 ( 3 ), 1,4‐(HNC 4 H 3 ‐C(H)N) 2 ‐C 6 H 4 ( 4 ), 4,4′‐(HNC 4 H 3 ‐C(H)N) 2 ‐(C 6 H 4 ‐C 6 H 4 ) ( 5 ), 1,5‐(HNC 4 H 3 C‐(H)N) 2 ‐C 10 H 6 ( 6 ), 2,6‐(HNC 4 H 3 C‐(H)N) 2 ‐C 10 H 6 ( 7 ), 2,6‐(HNC 4 H 3 C‐(H)N) 2 ‐C 14 H 8 ( 8 ), and the star‐shaped 1,3,5‐(HNC 4 H 3 ‐C(H)N‐1,4‐C 6 H 4 ) 3 ‐C 6 H 3 ( 9 ) were synthesized by the condensation reactions of 2‐formylpyrrole ( 1 ) with the corresponding aryl diamines, that is, o ‐phenylenediamine, m ‐phenylenediamine, p ‐phenylenediamine, 4,4′‐biphenylenediamine, 1,5‐naphthalenediamine, 2,6‐naphthalenediamine, 2,6‐anthracenediamine, and 4′,4′′,4′′′‐triamino‐1,3,5‐triphenylbenzene employing standard reaction conditions 13g. h The syntheses and purification of these ligand precursors are in general straightforward (except for the case of 8 ), being obtained mostly in good yields. Their characterization by 1 H and 13 C NMR spectroscopies are consistent with the literature values.…”