2‐Amino‐4‐(2‐pyridyl)thiazole as Chelating Ligand: A Dinuclear Oxido‐Bridged Ferric Complex and Mononuclear 3d Metal Complexes

Abstract

2‐Amino‐4‐(2‐pyridyl)thiazole (H2L) complexes of iron(III), iron(II), cobalt(II), nickel(II) and copper(II) have been prepared for the first time. The oxido‐bridged dinuclear ferric complex [(H2L)2FFeIII(μ‐O)FeIIIF(H2L)2](BF4)2 (1) and the mononuclear difluorido complex [FeIII(H2L)2F2](BF4) (2) were prepared with Fe(BF4)2·6H2O. Complex 1 contains strong antiferromagnetically coupled iron(III) ions. In addition, the mononuclear 3:1‐type complex [Co(H2L)3](ClO4)2 (3) and the mononuclear 2:1‐type complexes [Cu(H2L)2](ClO4)2 (4) and [M(H2L)2(NCX)2] (5: M = Fe, X = S; 6: M = Fe, X = Se; 7: M = Co, X = S; 8: M = Ni, X = S) were prepared.

Reactivity Differences for the Oxidation of FeIIFeII to FeIII(µ‐O)FeIII Complexes Caused by Pyridyl versus 6‐Methyl‐Pyridyl Ligands

“…Exchange couplings in µ‐oxo‐bridged complexes have been determined in numerous complexes and the coupling constants are in general in the range J = ‐100 ± 10 cm ‐1 . The strong dependence of J on the d (Fe–O) distance observed here is already well reflected in the two known complexes with a {Fe III F(µ‐O)Fe III F} core and with a J value provided: J = –88 cm ‐1 for d (Fe–O) = 1.82 Å and J = –106 cm ‐1 for d (Fe–O) = 1.79 Å …”

“…Thus, the introduction of the methyl groups elongates the Fe‐N py bonds reducing their covalency and therefore their electron density donation. Interestingly, this lower electron donation in [(susan 6‐Me ){Fe III F(µ‐O)Fe III F}] 2+ is not balanced by the µ‐O group, which is even slightly longer (1.801 vs 1.794 Å) in the 6‐methyl substituted complex (varies from 1.783 to1.825 Å in the three other known complexes with a {Fe III F(µ‐O)Fe III F} core) , , . While the Fe–F bonds do not change significantly at 1.86 Å (varies from 1.844 to1.918 Å in the three other known complexes with a {Fe III F(µ‐O)Fe III F} core),, , the amine donors slightly counter balance the lower charge donation of the 6‐methylpyridine donors as their bond lenghts decrease for the tripodal amines Fe–N2/N42 from 2.22 to 2.19 Å and for the central amines Fe–N1/N41 from 2.26 to 2.24 Å.…”

“…Interestingly, this lower electron donation in [(susan 6‐Me ){Fe III F(µ‐O)Fe III F}] 2+ is not balanced by the µ‐O group, which is even slightly longer (1.801 vs 1.794 Å) in the 6‐methyl substituted complex (varies from 1.783 to1.825 Å in the three other known complexes with a {Fe III F(µ‐O)Fe III F} core) , , . While the Fe–F bonds do not change significantly at 1.86 Å (varies from 1.844 to1.918 Å in the three other known complexes with a {Fe III F(µ‐O)Fe III F} core),, , the amine donors slightly counter balance the lower charge donation of the 6‐methylpyridine donors as their bond lenghts decrease for the tripodal amines Fe–N2/N42 from 2.22 to 2.19 Å and for the central amines Fe–N1/N41 from 2.26 to 2.24 Å. This slight Fe–N amine bond length decrease due to the introduction of the 6‐methyl group cannot completely counter balance the Fe‐N py bond lengths increase quantified by the Fe III bond valence sums which are 2.92 (Fe1) and 2.89 (Fe2) for [(susan){Fe III F(µ‐O)Fe III F}] 2+ and 2.83 (Fe1) and 2.75 (Fe2) for [(susan 6‐Me ){Fe III F(µ‐O)Fe III F}] 2+ .…”

Divergent Solution and Solid-State Structures of Mono- and Dinuclear Nickel(II) Pyridone Complexes

“…Cleavage of BF 4 – to form fluoride ions in the presence of transition metals has been reported, − although it is a rare observation and only occurs only in systems with strong N - heterocyclic ligands such as pyridines, pyrazoles, and imidazoles. The decomposition is thought to be the result of F coordination of BF 4 – to a coordinately unsaturated metal center (ML n ) followed by B–F bond cleavage to yield a [ML n –1 F] − complex and a L·BF 3 adduct .…”

Electrochemical enaminone C–H thiolation/C–N amination cascade for thiazole synthesis and its diastereoselective dearomatization

“…Moreover, the thiazole structure is also known as a useful ligand in coordination chemistry and catalysis. 8 Under the inspiration of the important applications of thiazoles in divergent areas, research on thiazole synthesis has been an issue of longstanding concern.…”