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Synthesis of Soluble 1,3‐Bridged Ferrocene‐Acetylene Polymers and the Divergent‐Convergent Synthesis of Defined Oligomers
Author(s) -
Plenio Herbert,
Hermann Jörg,
Leukel Jörg
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199812)1998:12<2063::aid-ejic2063>3.0.co;2-c
Subject(s) - ferrocene , chemistry , sonogashira coupling , metallocene , cyclopentadienyl complex , acetylene , medicinal chemistry , polymer , polymer chemistry , polymerization , organic chemistry , electrochemistry , palladium , catalysis , electrode
A –CH 2 NMe 2 group attached to ferrocene can be used as an ortho / ortho ‐directing group to selectively synthesize 1,2,3‐substituted ferrocenes, which are used as starting materials for novel 1,3‐linked ferrocene polymers and oligomers. The Sonogashira coupling reaction of 1‐(I),2‐(CH 2 NMe 2 )‐ferrocene with HC≡CSiEt 3 results in 1‐(C≡CSiEt 3 ),2‐(CH 2 NMe 2 )‐ferrocene ( 1b ), which – following an ortho ‐lithiation/iodination sequence – is converted into 1‐(I),2‐(CH 2 NMe 2 ),3‐(C≡CSiEt 3 )‐ferrocene ( 1d ). Removal of the –SiEt 3 protective group yields 1‐(I),2‐(CH 2 NMe 2 ),3‐(C≡CH)‐ferrocene, which can be polymerized under Sonogashira conditions to yield a soluble, bimodal ferrocene‐acetylene polymer of M W = 3700/7100 and M n = 4272. To understand the properties of the polymer better and to evaluate the effect of 1,3‐substitution on the electronic communication between the metal centers, a divergent‐convergent approach was used to synthesize defined di‐, tri‐ and tetranuclear ferrocenes. Accordingly, 1d was cross‐coupled with 1‐(CH 2 NMe 2 ),2‐(C≡CH)‐ferrocene to give [2‐(CH 2 NMe 2 )‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH 2 NMe 2 ),3‐(C≡CSiEt 3 )‐ferrocene‐1‐yl] ( 2a ). Removal of the protective group in 2a led to [2‐(CH 2 NMe 2 )‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH 2 NMe 2 ),3‐(C≡CH)‐ferrocene‐1‐yl] ( 2b ), which was treated with [1‐(I),2‐(CH 2 NMe 2 )ferrocene‐3‐yl]‐C≡C‐[2‐(CH 2 NMe 2 ),3‐(C≡CSiEt 3 )‐ferrocene‐1‐yl] ( 2c ) to result in the corresponding tetrameric ferrocene ( 4a ).