Synthesis of Metallocene Derivatives: Precursors for the Preparation of [1]Metallocenophanes
Date
2015-03-16
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ORCID
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Degree Level
Masters
Abstract
The planar-chiral C2-symmetrical dibromoferrocene derivatives, (S,S,Sp,Sp)-1,1'-dibromo-2,2'-di(2-butyl)ferrocene (88) and (S,S,Sp,Sp)-1,1'-dibromo-2,2'-bis{2-[1-(trimethylsilyl)propyl]} ferrocene (92), were synthesized using the well-established “Ugi’s amine” chemistry. The steric influences of the alkyl groups on ferrocenes 88 and 92 in salt-metathesis reactions were investigated. The reaction of 88 and 92 with iPr2NBCl2 yielded mixtures of bora[1]ferrocenophanes (bora[1]FCPs) 94 and 99 and 1,1'-bis(boryl)ferrocenes 95 and 100 respectively. Ferrocene 92 was expected to yield the highest product ratio of bora[1]FCPs to 1,1' bis(boryl)ferrocenes due to the significant amount of steric bulk on ferrocene from the alkyl groups; however, the product ratio was less than the product ratio obtained for the less bulky ferrocene 88. The product ratios for 88 and 92 were compared to the known product ratios for (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ferrocene (78) and (Sp,Sp)-1,1'-dibromo-2,2'-di(3-pentyl)ferrocene (79) to determine the effects of the alkyl groups in salt-metathesis reactions. To gain more insight into the effects of the alkyl groups on ferrocenes 88 and 92, a series of conformational analyses of 78, 88, and 92 were performed using density functional theory (DFT) calculations. The DFT calculations aided in the explanation for the unexpectedly low product ratio obtained for ferrocene 92.
In efforts to obtain new [1]ruthenocenophanes ([1]RCPs), the synthesis of the ruthenium analog of 78, (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ruthenocene (105), was attempted. To accomplish this, (R,R)-1,1'-bis(α-N,N-dimethylaminoethyl)ruthenocene (109) was prepared using the same chemistry that was used to prepare its ferrocene analog. However, the synthesis of (R,R,Sp,Sp)-1,1'-dibromo-2,2'-bis(α-N,N-dimethylaminoethyl)ruthenocene (110) via the dilithiation of 109 was unsuccessful.
The synthesis of dibromoferrocene derivatives using “Ugi’s amine” chemistry is a long and inflexible process. Therefore, a method to prepare dibromoferrocene derivatives through an alternative synthetic pathway was investigated. The synthesis of (Ss,Ss)-1,1'-bis(p-tolylsulfinyl) ferrocene (118) was accomplished by reacting dilithioferrocene•tmeda with (1R,2S,5R)-(-)-menthyl (SS)-p-tolylsulfinate (117). The diastereoselective dilithiation and subsequent silylation of 118 to obtain (Ss,Ss,Sp,Sp)-2,2'-bis(trimethylsilyl)-1,1'-bis(p-tolylsulfinyl)ferrocene (120) proved to be problematic.
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Keywords
Metallocene, Metallocenophane, Ferrocene, Organometallics, Synthesis, Boron, Metallopolymers
Citation
Degree
Master of Science (M.Sc.)
Department
Chemistry
Program
Chemistry