392292-96-5Relevant academic research and scientific papers
Redox-active ligands and organic radical chemistry
Zhu, Di,Thapa, Indira,Korobkov, Ilia,Gambarotta, Sandro,Budzelaar, Peter H. M.
, p. 9879 - 9887 (2011)
Knowledge about bonding in diiminepyridine (L) halide, alkyl, and dinitrogen complexes of the metals iron, cobalt, and nickel is summarized, and two new examples are added to the set: L1Ni(Me) and L 1Ni(N2). Reactivity of
Earth-Abundant Metal Catalysis Enabled by Counterion Activation
Agahi, Riaz,Challinor, Amy J.,Carter, Neil B.,Thomas, Stephen P.
, p. 993 - 997 (2019/02/14)
A precatalyst activation strategy has been developed for earth-abundant metal catalysis enabled by counterion dissociation and demonstrated through alkene hydroboration. Commercially available iron and cobalt tetrafluoroborate salts were found to catalyze
Radical mechanisms in the reaction of organic halides with diiminepyridine cobalt complexes
Zhu, Di,Korobkov, Ilia,Budzelaar, Peter H. M.
, p. 3958 - 3971 (2012/07/14)
The formally Co(0) complex LCo(N2) (L = 2,6-bis(2,6- dimethylphenyliminoethyl)pyridine) can be prepared via either Na/Hg reduction of LCoCl2 or hydrogenolysis of LCoCH2SiMe3. In the latter reaction, LCoH could be trapped by reaction with N≡CC 6H4-4-Cl to give LCoN=CHC6H4-4-Cl. LCo(N2) reacts with many alkyl and aryl halides RX, including aryl chlorides, to give a mixture of LCoR and LCoX in a halogen atom abstraction mechanism. Intermediacy of free alkyl and aryl radicals is confirmed by the ring-opening of cyclopropylmethyl to crotyl, and the rearrangement of 2,4,6-tBu3C6H2 to 3,5- tBu2C6H3CMe2CH 2, before binding to Co. The organocobalt species generated in this way react further with activated halides R′X (alkyl iodides; allyl and benzyl halides) to give cross-coupling products RR′ in what is most likely again a halogen abstraction mechanism. DFT studies support the proposed radical pathways for both steps. MeI couples smoothly with LCoCH2SiMe 3 to give LCoI and CH3CH2SiMe3, but the analogous reaction of tBuI leads in part to radical attack at the 3 and 4 positions of the pyridine ring to form (tBu 2-L)CoI and (tBu2-L)CoI2.
Chelate bis(imino)pyridine cobalt complexes: Synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation
Kleigrewe, Nina,Steffen, Winfried,Bloemker, Tobias,Kehr, Gerald,Froehlich, Roland,Wibbeling, Birgit,Erker, Gerhard,Wasilke, Julia-Christina,Wu, Guang,Bazan, Guillermo C.
, p. 13955 - 13968 (2007/10/03)
Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C 6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (lig Me)CoCH3 (17) with Li[B(C6F5) 4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)-1 h-1 bar-1 at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (ligOMe) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (lig OMe)CoMe (25/26). Treatment of 25/26 with excess B(C 6F5)3 gave the η6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.
Investigations into the mechanism of activation and initiation of ethylene polymerization by bis(imino)pyridine cobalt catalysts: Synthesis, structures, and deuterium labeling studies
Humphries, Martin J.,Tellmann, Kilian P.,Gibson, Vernon C.,White, Andrew J. P.,Williams, David J.
, p. 2039 - 2050 (2008/10/09)
The activation of bis(imino)pyridine cobalt(II) precatalysts by MAO leads initially to a bis(imino)pyridine cobalt(I) cationic species with no cobalt-C(alkyl) bond into which insertion can occur. Mechanistic studies have shown that the initiation of polym
Generation of bis(iminoalkyl)pyridine cobalt(I) cations under metal alkyl free conditions that polymerize ethene
Steffen, Winfried,Bloemker, Tobias,Kleigrewe, Nina,Kehr, Gerald,Froehlich, Roland,Erker, Gerhard
, p. 1188 - 1189 (2007/10/03)
Treatment of the bis(iminoethyl)- or bis(iminobenzyl)pyridine cobalt dichlorides 3a,b with "butadiene-magnesium" (a, R = CH3) or methyllithium (b, R = Ph) yields the corresponding bis(iminoalkyl)pyridine cobalt(i) chloride complexes 7a,b. Chlor
Olefin polymerization with [{bis(imino)pyridyl}CoIICl2]: Generation of the active species involves CoI
Kooistra, T. Martijn,Knijnenburg, Quinten,Smits, Jan M. M.,Horton, Andrew D.,Budzelaar, Peter H. M.,Gal, Anton W.
, p. 4719 - 4722 (2007/10/03)
Activated by reduction: On treatment with methylaluminoxane (MAO), the Brookhart/Gibson cobalt-based polymerization precatalyst [LCoIICl2] is first reduced to [LCoICl], subsequently alkylated to [LCoIMe], and finally converted into the (as yet unknown) active species (see scheme, PE=polyethene).
The nature of the active species in bis(imino)pyridyl cobalt ethylene polymerisation catalysts
Gibson, Vernon C.,Humphries, Martin J.,Tellmann, Kilian P.,Wass, Duncan F.,White, Andrew J. P.,Williams, David J.
, p. 2252 - 2253 (2020/09/03)
Studies on cobalt ethylene polymerisation catalysts bearing bis(imino)pyridine ligands strongly indicate that the activated species is not the anticipated cobalt(II) alkyl cation.
