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金長煥,李鳴儀 연세대학교 대학원 1977 延世論叢 Vol.14 No.2
In order to see the effect of d-orbitals of silicon on the ring π-electrons of ferrocene, the trice- thylsilyl derivatives of ferrocene were prepared. The reaction of 1,1'-bis (trimethylsilyl) ferrocene with mercery (II) chloride gave 1'-trimetalylsilylferrocenylmercury (II) chloride, which was converted to 1-carboxy-1'- (trimethylsilyl) ferrocene through lithiation followed by carbonation reaction. By the potentiometric titration, the pKa values of ferrocenecarboxylic acid and 1-carboxy-1'- (trimethylsilyl) ferrocene were found to be 6.11 and 5.98 respectively at 25℃ and were compared with the literature values of other alkylated ferrocenecarboxylic acids. Contrary to the expectation by the inductive effect of trimethylsilyl group, 1-carboxy-1'- (trimethylsilyl) ferrocene was found to be slightly stronger acid than ferrocenoic acid. This can be explained only by assuming that the 3d-orbital of silicon overlap extensively With the ring π-orbital find form dπ-pπ dative bond. This dπ-dπ bonding appears to be an important factor, enough to compensate the inductive effect, in stabilizing the conjugate base form of the trimethylsilyl substituted ferrocenoic acid by withdrawing the electronic charge away from the cyclorentadienyl ring system.