Homoleptic Trimethylsilylacetylide Complexes of Chromium(III), Iron(II), and Cobalt(III):  Syntheses, Structures, and Ligand Field Parameters

Berben, Louise A.; Long, Jeffrey R.

doi:10.1021/ic051551z

Cited by 47 publications

(31 citation statements)

References 70 publications

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“…The hexaacetylide approaches Co(CN) 6 3− in field strength (Δ oct = 34 000 cm −1 ) and is fairly similar in nepelauxetic character (B = 430 cm −1 ). 64 Successful application of the Tanabe−Sugano diagram to the UV−vis features of (κ-C,N-pyEA-Ar i Pr 2 ) 3 Co (3) in Figure 4 supports the assignment of the 493 and 370 nm bands as d−d transitions, but the field strength of ∼20 000 cm −1 thus derived is significantly lower than that of Co(CCSiMe 3 ) 6 3− . An sp 3 -alkyl might be expected to impart a stronger field on the basis of a better energy match with the cobalt 3d-orbitalsassuming all carbon-based σ-orbitals are lower than those of the cobaltthan the sp-hybridized alkynyl ligand, but this is not the case.…”

Section: ■ Discussionmentioning

confidence: 52%

First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds

et al. 2015

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Ene-amines Z-3-(2-pyridyl)-1-aza(2,6-i Pr 2 -Ph)propene, (pynac)H, and 2-(2-pyridyl)-1-aza(2,6-R,R′-Ph)propene, (pyEA-ArRR′)H, were synthesized by condensation procedures; corresponding lithium or potassium ene-amides were prepared via standard deprotonation protocols. Addition of 2 equiv of (pynac)H to {(Me 3 Si) 2 N} 2 Fe(THF) or 2 Li(pynac) to FeBr 2 (THF) 2 afforded (pynac) 2 Fe (1), while treatment of CrCl 2 (THF) 2 , MnCl 2 , FeBr 2 (THF) 2 , and CoCl 2 py 4 with 2 equiv of (pyEAAr i Pr 2 )K afforded pseudotetrahedral (pyEA-Ar i Pr 2 ) 2 M (2-M, M = Cr, Mn, Fe) and (pyEA-Ar i Pr 2 ) 2 Co-py (2-Co-py). Diamagnetic (κ-C,N-pyEA-Ar i Pr 2 ) 3 Co (3) was prepared in low yield (∼7%) from CoCl 2 , and its Co−C(sp 3 ) linkages are unusually low in field strength. Reactivity studies yielded little clean reactivity, but thermolysis of 2-Co-py afforded the bis-indolamide derivative {κ-N,N-N(C 6 H 3 (2-i Pr)CMe 2 C(Me)(2-py)} 2 Co (5-Co), and related thermolyses of 2-M (M = Cr, Mn, Fe), conducted on NMR tube scales, generated related 5-M (M = Cr, Mn, Fe) at roughly the same rates. This observation prompted thermolyses of (pyEA-ArRR′)Li, which rearrange to their corresponding indolamides in >90% yields. Rate studies, accompanied by KIE and EIE observations, revealed that an initial hydrogen transfer is reversible and is likely to correspond to an anionic rearrangement, whereas C−C bond formation is ratedetermining, as suggested by accompanying calculations. X-ray structure determinations of 1, 2-Fe, 2-Co-py, 3, and 5-Co were conducted. ■ INTRODUCTIONTransition metal compounds containing pyridine-imine (PI) 1−6 and pyridine-diimine (PDI) 7−19 moieties often exhibit redox noninnocent (RNI) 20−29 behavior due to multiple accessible charged states of the ligands. This capacity is most evident in first-row transition metals, where the ionic character of the metal−ligand bond limits charge distribution via covalency, and in early transition metals 29−32 that have limited redox capability. Ligands designed as PI variants consisting of 2-azaallyls, their precursors, or related chelates have led to intriguing carbon− carbon and C−X bond-forming reactions and afford examples of RNI, as illustrated in Figure 1.Compounds containing 1,3-di-2-pyridyl-2-azaallyl (smif) 33 tridentate ligands exhibit reversible and irreversible C−C bondforming reactions depending on steric factors (A), 34 while the generation of transient azaallyls within a tetradentate chelate have afforded [{Me 2 C(CHNCH-2-py) 2 }M] 2 (M = Cr, Co, Ni) dimers wherein three new carbon−carbon bonds have been formed around unique metal−metal bonds (B). 35 Incorporating PI precursors into a nacnac framework 36−39 permitted the isolation of carbon radical character, leading to C−C bond formation (C), 40 but in related tetradentate ligands, electrostatic stabilization of a 14e − π-system afforded very stable Fe(II) complexes (D). 41,42 Finally, a tetradentate di-PI ligand revealed five redox states (E) that were quite stable, while the metal formally remained Ni(II). 6 The s...

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Section: ■ Discussionmentioning

confidence: 52%

First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds

et al. 2015

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“…23 The DFT method was used as it gives good results for all 3d-metal complexes. [24][25][26] These B3LYP calculations were performed with the Gaussian03 program. 27 Various rotamers of compounds 1 and 2 were computed.…”

Section: Density Functional Methods Calculationmentioning

confidence: 99%

Synthesis, NMR, DFT and antimicrobial studies of Zn(II) complexes with N-benzyloxycarbonyl-S-alanine

Mitić¹,

Miodragović²,

Sladić³

et al. 2008

JSCS

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In this study, the first complexes of Zn(II) with the N-benzyloxycarbonyl-S-alaninato ligand (N-Boc-S-ala) were synthesized. The new complexes were characterized by elemental analysis, conductometric measurements, IR, 1 H-NMR, 13 C-NMR and 2D-NMR spectroscopy. On the basis of the experimental data, tetrahedral geometry of the Zn(II) complexes was proposed. A very good agreement between the NMR and DFT calculated data was obtained. Investigation of antimicrobial activity of the newly synthesized complexes was also performed. It was established that [Zn(N-Boc-S-ala) 2 ] was selective and acts only on Candida albicans.

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“…A number of such species have already been referred to in the section on complexes of bis(imino)pyridine (and related) ligands. 56 Analysis of the uniaxial magnetic properties of two coordinate [Fe(C(SiMe 3 ) 3 ) 2 ] has been reported. 57…”

Section: Complexes Of C-donorsmentioning

confidence: 99%

Iron, cobalt and nickel

Cotton¹

2006

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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Homoleptic Trimethylsilylacetylide Complexes of Chromium(III), Iron(II), and Cobalt(III): Syntheses, Structures, and Ligand Field Parameters

Cited by 47 publications

References 70 publications

First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds

First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds

Synthesis, NMR, DFT and antimicrobial studies of Zn(II) complexes with N-benzyloxycarbonyl-S-alanine

Iron, cobalt and nickel

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