Iron‐Catalyzed Polymerization of Isoprene and Other 1,3‐Dienes

Raynaud, Jean; Wu, Jiacheng; Ritter, Tobias

doi:10.1002/ange.201205152

Cited by 28 publications

(27 citation statements)

References 30 publications

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“…13,64 However, there is a long-term problem with use of lanthanides for this purpose. 67 Our catalysts 5-7, then, are the only 3d transition metal complexes capable of producing high M n polyisoprene of >75% cis-1,4 content at industrially preferable ambient or above-ambient temperature with satisfactory activity. In fact, the most abundant transition metal, iron, would be ideal, and has some precedent.…”

Section: Catalyst Performance Comparisonmentioning

confidence: 89%

“…62 The most recent work in the area has been dominated by investigation of Rare Earths, which do indeed offer higher cis selectivity and activity. 67 However, in order to attain a good activity (1250 mol IP mol À1 Fe h À1 ) and a good cis-1,4 selectivity (83%), and sufficient M n (23 Â 10 5 ) it was necessary to use cryogenic temperatures (À78 C). 2 As discussed in our previous paper on butadiene, 36 there are strongly competing uses for the unique magnetic and optical properties of the lanthanides, and it is strongly preferable to use base metals where possible.…”

Section: Catalyst Performance Comparisonmentioning

confidence: 99%

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The behaviour of β-triketimine cobalt complexes in the polymerization of isoprene

Alnajrani

Mair

2015

RSC Adv.

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Four new b-triketimine cobalt complexes [(LCo-m-Br) 2 ][BArF] 2 where L ¼ N,N 0 ,N 00 -triaryl-b-diketimine were synthesised and then characterized by single-crystal X-ray diffraction, MALDI-MS and elemental analysis. In combination with three previously reported, they provided a series of seven subtly different complexes which were screened for activity in the catalysis of isoprene polymerization: the structure of the ligand (L) had strong effects on activity and stereoselectivity. The produced polyisoprene contained a mixture of cis-1,4, trans-1,4 and 3,4-enchained monomers; 4,1-errors followed 3,4 errors. The highest percentage of cis-1,4 content (80%) was obtained with complex 5 where two electron-withdrawing fluorine substituents occupied the 2-and 6-positions of two of the imino-aryl rings. This polymer was obtained in 98.5%conversion. Both cis-1,4 content and activity decreased when electron donor substituents were present on the aryl rings, so that complex 1, with three methyl substituents in positions 2, 4 and 6 gave the lowest cis-1,4 content (73.6%), with a conversion of only 58.5%, under identical conditions. The temperature of the polymerization, the type of aluminium co-catalyst used, and the Al/Co ratio strongly affected the activity and microstructure of the polyisoprene produced. Ethylaluminiumsesquichloride was the most active of a range of organoaluminiums screened. A kinetic study using complex 6 as catalyst demonstrated that the polymerization was first-order in monomer, and that approximately 12% of cobalt formed active centers. The combination of high molecular weight (>10 5 ) with moderately high activity at conveniently accessible temperatures to give predominantly cis-1,4-polyisoprene but with 3,4 units to promote efficient crosslinking is potentially attractive, and has not previously been attained with 3d elements.

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Section: Catalyst Performance Comparisonmentioning

confidence: 89%

Section: Catalyst Performance Comparisonmentioning

confidence: 99%

The behaviour of β-triketimine cobalt complexes in the polymerization of isoprene

Alnajrani

Mair

2015

RSC Adv.

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“…Ritter et al. recently established the use of iron iminopyridine complexes as catalysts for the 1,4‐hydrosilylation of 1,3‐dienes,9 the 1,4‐hydroboration of 1,3‐dienes,10 the 1,4‐addition of terminal olefins to 1,3‐dienes,11 and the polymerization of 1,3‐dienes 12…”

Section: Introductionmentioning

confidence: 99%

Iron Dicarbonyl Complexes Featuring Bipyridine‐Based PNN Pincer Ligands with Short Interpyridine CC Bond Lengths: Innocent or Non‐Innocent Ligand?

Zell

Milko

Fillman

et al. 2014

Chemistry A European J

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A series of iron dicarbonyl complexes with bipyridine-based PNN pincer ligands were synthesized and characterized by multinuclear NMR spectroscopy ((1) H, (13) C, (15) N, (31) P), IR spectroscopy, cyclic voltammetry, (57) Fe Mössbauer spectroscopy, XPS spectroscopy, and single-crystal X-ray diffraction. The complexes with the general formula [(R-PNN)Fe(CO)2 ] (5: R-PNN=tBu-PNN=6-[(di-tert-butylphosphino)methyl]-2,2'-bipyridine, 6: R-PNN=iPr-PNN=6-[(diisopropylphosphino)methyl]-2,2'-bipyridine, and 7: R-PNN=Ph-PNN=6-[(diphenylphosphino)methyl]-2,2'-bipyridine) feature differently P-substituted PNN pincer ligands. Complexes 5 and 6 were obtained by reduction of the corresponding dihalide complexes [(R-PNN)Fe(X)2 ] (1: R=tBu, X=Cl; 2: R=tBu, X=Br; 3: R=iPr, X=Cl; 4: R=iPr, X=Br) in the presence of CO. The analogous Ph-substituted complex 7 was synthesized by a reaction of the free ligand with iron pentacarbonyl. The low-spin complexes 5-7 (S=0) are diamagnetic and have distorted trigonal bipyramidal structures in solution, whereas in the solid state the geometries around the iron are best described as distorted square pyramidal. Compared to other structurally characterized complexes with these PNN ligands, shortened interpyridine CC bonds of about 1.43 Å were measured. A comparison with known examples, theoretically described as metal complexes bearing bipyridine π-radical anions (bpy(.) (-) ), suggests that the complexes can be described as Fe(I) complexes with one electron antiferromagnetically coupled to the ligand-based radical anions. However, computational studies, at the NEVPT2/CASSCF level of theory, reveal that the shortening of the CC bond is a result of extensive π-backbonding of the iron center into the antibonding orbital of the bpy unit. Hence, the description of the complexes as Fe(0) complexes with neutral bipyridine units is the favorable one.

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“…Tobias Ritter (Harvard University) has been awarded the 2012 Klung Wilhelmy Weberbank Prize for his achievements in the area of organometallic chemistry and the selective fluorination of biochemically relevant molecules. Ritter has previously been highlighted here,6a,b and has recently published a Communication in Angewandte Chemie on the iron‐catalyzed polymerization of dienes 6c. His Review on the synthesis of fluorinated compounds is in press 6d…”

Section: Awarded …︁mentioning

confidence: 99%

Novartis Early Career Award: S. E. Reisman and C. R. J. Stephenson / Carl Duisberg Plaque: G. Gauglitz / Basolo Medal: R. Eisenberg / Bohlmann Lecture: D. W. C. MacMillan / Klung Wilhelmy Weberbank Prize: T. Ritter

2012

Angew Chem Int Ed

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Iron‐Catalyzed Polymerization of Isoprene and Other 1,3‐Dienes

Cited by 28 publications

References 30 publications

The behaviour of β-triketimine cobalt complexes in the polymerization of isoprene

The behaviour of β-triketimine cobalt complexes in the polymerization of isoprene

Iron Dicarbonyl Complexes Featuring Bipyridine‐Based PNN Pincer Ligands with Short Interpyridine CC Bond Lengths: Innocent or Non‐Innocent Ligand?

Novartis Early Career Award: S. E. Reisman and C. R. J. Stephenson / Carl Duisberg Plaque: G. Gauglitz / Basolo Medal: R. Eisenberg / Bohlmann Lecture: D. W. C. MacMillan / Klung Wilhelmy Weberbank Prize: T. Ritter

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