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Synthesis of Heptamethylindenylcobalt complexes as catalysts for C-H activation / eingereicht von Magdalena Sophie Zachl, BSc
AuthorZachl, Magdalena Sophie
CensorHapke, Marko
PublishedLinz, 2018
Description69 Blätter : Illustrationen
Institutional NoteUniversität Linz, Masterarbeit, 2018
Document typeMaster Thesis
URNurn:nbn:at:at-ubl:1-26037 Persistent Identifier (URN)
 The work is publicly available
Synthesis of Heptamethylindenylcobalt complexes as catalysts for C-H activation [2.37 mb]
Abstract (English)

Goal of this work was the synthesis of cobalt complexes carrying the heptamethylindenyl (Ind*) ligand(7), a class of compounds closely related to the well-known pentamethylcyclopentadienyl (Cp*) (4) complexes, which however have never been reported. An efficient synthesis of heptamethylindene (40) was soon established, gaining 2,3,4,5,6,7-hexamethyl-2,3-dihydro-1H-inden-1-one (47b) in a one-pot procedure in nearly quantitative yields, which after two steps yielded the product in roughly 50% overall yield. Once the ligand was obtained, various approaches were tried to gain access to Ind*Co(CO)2 (41), but only a single synthetic approach, using n-BuLi, lead to the desired result, although the complex could not be obtained in completely pure form. Ind*Co(CO)I2 (42) was synthesized from this compound, but again purification proved problematic. The subsequent dimerization could not be carried out successfully, as high temperatures are employed in this step while Ind*Co compounds appear to be more unstable than their Cp* analogues, both in regard to thermal stability and air and moisture sensitivity. It was also attempted to produce Ind*Co complexes carrying phosphite ligands, starting from Ind*Co(CO)2 (41), CoX[P(OR)3]3 (where X = halogen) (66a-f) or using a direct procedure from CoCl2. However, 31P NMR suggested in all cases that the ligand could not be coordinated successfully. Due to these problems with catalyst synthesis, giving only Ind*Co(CO)2 (41) and Ind*Co(CO)I2 (42) in insufficient purity, no screening reactions testing the performance of the novel complexes in C-H functionalizations were conducted. Additionally, some attempts were made to produce Cp*-like ligands carrying a fused ring, which could be regarded as hydrogenated Ind* species, which would probably exhibit the unproblematic coordination behaviour of Cp* ligands. Carbonylations of diynes and the Pauson-Khand reaction of enynes were strategies employed to achieve the preparation of these ligands.

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