Synthesis of Soluble 1,3-Bridged Ferrocene-Acetylene Polymers and the Divergent-Convergent Synthesis of Defined Oligomers

Abstract

A –CH2NMe2 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‐(CH2NMe2)‐ferrocene with HC≡CSiEt3 results in 1‐(C≡CSiEt3),2‐(CH2NMe2)‐ferrocene (1b), which – following an ortho‐lithiation/iodination sequence – is converted into 1‐(I),2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene (1d). Removal of the –SiEt3 protective group yields 1‐(I),2‐(CH2NMe2),3‐(C≡CH)‐ferrocene, which can be polymerized under Sonogashira conditions to yield a soluble, bimodal ferrocene‐acetylene polymer of MW = 3700/7100 and Mn = 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‐(CH2NMe2),2‐(C≡CH)‐ferrocene to give [2‐(CH2NMe2)‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene‐1‐yl] (2a). Removal of the protective group in 2a led to [2‐(CH2NMe2)‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CH)‐ferrocene‐1‐yl] (2b), which was treated with [1‐(I),2‐(CH2NMe2)ferrocene‐3‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene‐1‐yl] (2c) to result in the corresponding tetrameric ferrocene (4a).

Palladium-catalyzed reaction of 2-iodoferrocenyl alcohols with internal alkynes: Synthesis of functionally 1,2-disubstituted ferrocenes and ferroceno-pyrans

“…The solution was concentrated in a rotary evaporator and the remaining reddishbrown oil residue was subjected to the chromatography on silica gel using 10:10:1 (ethyl acetate:hexane:triethylamine) as eluent to yield 4 (2.60 g, 67%, dark red oil). The physical and spectroscopic data are in agreement with those reported previously for this compound [90,96].…”

“…For example, inspired by the successful Sonogashira coupling reaction of 2-(N,N-dimethylaminomethyl)iodoferrocene with terminal alkynes [96], we reasoned that similar catalytic conditions might also be applicable for our purpose. Therefore, 2-iodoferrocenyl alcohol 1 (1.00 mmol) and diphenylacetylene (6a) (2.00 mmol) in diisopropylamine (7.00 mL) were treated with (Ph 3 P) 2 PdCl 2 (0.01 mmol) at 100 C for 24 h (Table 1, entry 1).…”

Organometallic Polymers of the Transition Metals

“…Plenio and coworkers have reported the synthesis of 1,2,3-substituted ferrocenes containing one iodo and one acetylene group. [119,120] Polymerization using Sonogashira coupling conditions resulted in the production of polymers with optical activity [119] or with functionalized side chains. [120] Scheme 30 shows the synthesis of a homoannular polyferrocene with an aza crown ether attached to the skeletal cyclopentadienyl ring.…”

“…[119,120] Polymerization using Sonogashira coupling conditions resulted in the production of polymers with optical activity [119] or with functionalized side chains. [120] Scheme 30 shows the synthesis of a homoannular polyferrocene with an aza crown ether attached to the skeletal cyclopentadienyl ring. [120] The reaction of diiodoferrocenes with diethynyl monomers has also been used in the production of polymetallocenes with acetylene units in their backbones as shown in Scheme 31.…”

“…[120] Scheme 30 shows the synthesis of a homoannular polyferrocene with an aza crown ether attached to the skeletal cyclopentadienyl ring. [120] The reaction of diiodoferrocenes with diethynyl monomers has also been used in the production of polymetallocenes with acetylene units in their backbones as shown in Scheme 31. [121][122][123] These palladium-catalyzed reactions resulted in the formation of polymers displaying semiconducting properties upon doping with iodine.…”