Formation of a Paramagnetic Al Complex and Extrusion of Fe during the Reaction of (Diiminepyridine)Fe with AlR<sub>3</sub> (R = Me, Et)

Scott, Jennifer; Gambarotta, Sandro; Korobkov, Ilia; Knijnenburg, Quinten; Bruin, Bas de; Budzelaar, Peter H. M.

doi:10.1021/ja056135s

Cited by 147 publications

(131 citation statements)

References 37 publications

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“…We were unable to obtain any evidence of the corresponding monometallic species, even when reaction conditions were varied. Reactivity differences between AlMe 3 and AlEt 3 has also been noted by Gambarotta and co-workers [20]. The X-ray crystallographic analysis of bimetallic 4 was successful.…”

Section: Aluminium Alkyl Complexessupporting

confidence: 65%

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Johnstone

Aazam

Hitchcock

et al. 2010

Journal of Organometallic Chemistry

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Section: Aluminium Alkyl Complexessupporting

confidence: 65%

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Johnstone

Aazam

Hitchcock

et al. 2010

Journal of Organometallic Chemistry

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“…. [45] Also, comparable nitrogen and proton hfcs have been observed for solutions of a 2,2'-bipyridyl radical in ethylene diamine at room temperature (e.g., AA C H T U N G T R E N N U N G (H 5Àpy ) = 15.87 and AA C H T U N G T R E N N U N G (H 3Àpy ) = 4.32 MHz). [46] In summary, the redox chemistry of N-2,6-diisopropylphenylimino-2-pyridine (IPy) was investigated in detail including cyclic voltammetry.…”

mentioning

confidence: 77%

Sodium and Potassium Salts of Mono‐ and Dianionic α‐Iminopyridines

Nayek

Arleth

Trapp

et al. 2011

Chemistry A European J

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[a] a-Diimine (1,4-diaza-1,3-butadiene) ligands are well established in main-group, transition-metal, and lanthanide chemistry. [1][2][3][4][5][6][7] Beside their application as ligands for latetransition-metal complexes, which can function as active and selective catalysts for a-olefin polymerization, [8] a-diimine and related ligands are of special interest due to their ability to undergo redox chemistry.[9] They have frequently been described as "non-innocent" ligands. [10][11][12] For example, in lanthanide chemistry, it has been found that the formal oxidation state of Eu [13] and Yb [14] depends on the nature of the substituents on the a-diimine ligand and on the ligand on the metal center. Thus, in both cases, the a-diimine acts either as neutral ligand or as radical anion. Reduction of adiimines, using either alkali metals or electrochemical methods, leads in each case to the corresponding radical anions [15][16][17][18] and eventually to diamagnetic dianions, [17][18][19][20][21][22][23][24] albeit at much more negative potentials. In contrast to the well-established chemistry of a-diimines, the related a-iminopyridines are much less investigated. The three different redox states of a-iminopyridines are shown in Scheme 1. The neutral system L 0 has been extensively used as ligand for late transition metals. [4,[25][26][27][28][29] Only recently, the monoanion LC À and the doubly reduced dianion L 2À were investigated as ligands in more detail. Recent reports showed a series of bis(a-iminopyridine)-metal complexes featuring aluminum [30] and the first-row transition ions (Cr, Mn, Fe, Co, Ni, and Zn) [31,32] with the monoanionic, and thus paramagnetic p-radical form of the ligand in coordination complexes. The a-iminopyridine N-2,6-diisopropylphenylimino-2-pyridine (IPy) has also been introduced in lanthanide chemistry. [33,34] In this context, a potassium derivative of the monoanionic form of a-iminopyridine was prepared in situ, but not further characterized.[34] The doubly reduced dianion has only been observed in two magnesium complexes so far. [35] In contrast, the reaction of "GaI" with a-iminopyridine leads to reductive coupling of the coordinated ligand to give neutral diamido-digallium complexes. [36] Based on this information, we were interested in a comprehensive study of the properties of the alkali metal salts of the monoanionic p-radical and the doubly reduced dianion of a-iminopyridine in solution and in the solid state. We report here the synthesis, characterization and magnetic properties of sodium and potassium salts of the mono-and dianionic a-iminopyridines.N-2,6-Diisopropylphenylimino-2-pyridine (IPy) was prepared according to literature procedures.[37] As a first entry point, we examined the electrochemical properties of IPy using cyclic voltammetry at room temperature in THF. As can be seen from Figure 1, we detected a quasi-reversible one-electron reduction process centered at E 0 1=2 = À2.57 V (vs. the ferrocene/ferrocenium couple, Fc/Fc + ), with a peakto-peak separation of 15...

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“…Such chemistry has recently been highlighted for homogeneous catalysts by Budzelaar et al [22][23][24][25] In an attempt to elucidate similar chemistry on our silica supported (imino)-pyridyl iron complexes we employed XPS on our model catalysts after treatment with aluminium alkyls (Figure 3).…”

Section: Stability Of the Supported Bis(imino)pyridyl Iron Complexesmentioning

confidence: 76%

“…Our results are in nice agreement with the proposed iron extrusion by iron to alumina transmetallation as proposed in ref. [23] The stability of the N1s emission with respect to intensity and peak shape may indicate that the nitrogen environment does not change further during interaction with aluminium alkyls. However, the sensitivity of XPS with respect to more subtle changes in the ligand is rather limited.…”

Section: Stability Of the Supported Bis(imino)pyridyl Iron Complexesmentioning

confidence: 99%

A Flat Model Approach to Tethered Bis(imino)pyridyl Iron Ethylene Polymerization Catalysts

Han

Niemantsverdriet

Thüne

2007

Macromolecular Symposia

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Summary: A surface science model for a silica supported bis(imino)pyridyl iron complexes is applied to reveal the surface chemistry of these heterogeneous polymerization catalysts. The polymerization activity of these models and the molecular weight distribution of the resulting polymer are comparable to similar catalysts supported on amorphous silica. The catalyst deactivates partially during the first hour of ethylene polymerization. Based on photoelectron spectroscopy (XPS) we attribute this deactivation to iron extrusion by the aluminium alkyl activator.

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Formation of a Paramagnetic Al Complex and Extrusion of Fe during the Reaction of (Diiminepyridine)Fe with AlR₃ (R = Me, Et)

Cited by 147 publications

References 37 publications

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Sodium and Potassium Salts of Mono‐ and Dianionic α‐Iminopyridines

A Flat Model Approach to Tethered Bis(imino)pyridyl Iron Ethylene Polymerization Catalysts

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Formation of a Paramagnetic Al Complex and Extrusion of Fe during the Reaction of (Diiminepyridine)Fe with AlR3 (R = Me, Et)

Cited by 147 publications

References 37 publications

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Sodium and Potassium Salts of Mono‐ and Dianionic α‐Iminopyridines

A Flat Model Approach to Tethered Bis(imino)pyridyl Iron Ethylene Polymerization Catalysts

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Formation of a Paramagnetic Al Complex and Extrusion of Fe during the Reaction of (Diiminepyridine)Fe with AlR₃ (R = Me, Et)