Oxidative purification of halogenated ferrocenes

Abstract

We report the large scale syntheses and 'oxidative purification' of fcI 2 , fcBr 2 and FcBr (fc = ferrocene-1,1'diyl, Fc = ferrocenyl). These valuable starting materials are typically laborious to separate via conventional techniques, but can be readily isolated by taking advantage of their increased E 1/2 relative to FcH/FcX contaminants. Our work extends this methodology towards a generic tool for the separation of redox active mixtures. Scheme 1 Synthesis and oxidative purification of (a) FcI (Goeltz and Kubiak), 21 and fcBr, and (b) fcI 2 and fcBr 2 (this work) (A − = Cl − , [FeCl 3 ] − or [FeCl 4 ] − ).

Hole Transfer from Photoexcited Quantum Dots: The Relationship between Driving Force and Rate

“…In this study, the electron-withdrawing group was bromine, which was found to lower the energy of the highest occupied molecular orbital (HOMO) on ferrocene by approximately 130 meV per additional bromine, in accordance with previous literature results. 32 To achieve higher HOMO energies, electron donating methyl substituents were employed. Higher HOMO energies will correspond to larger driving forces for hole transfer from the QD to the ferrocene.…”

Rapid Sonogashira cross-coupling of iodoferrocenes and the unexpected cyclo-oligomerization of 4-ethynylphenylthioacetate

“…A systematic study into the Sonogashira cross-coupling of 1,1'-diiodoferrocene (fcI 2 ) confirms that the Pd(0)/P( t Bu) 3 system provides a remarkable rate increase over Pd(0)/(PPh 3 ) 2 . Attempts to couple 4-ethynylphenylthioacetate (2) with fcI 2 instead produced a novel cyclic trimer of the 10 former, from syn addition of S-Ac across C≡C.…”

“…Full experimental details may be found in the supporting information. † 65 Intrigued as to why previous reactions using PdCl 2 (PhCN) 2 /P( t Bu) 3 had proven unsuccessful, we noted that in these attempts substrates had featured thioacetyl and pyridyl functionalities. 15 This prompted investigation into 70 Scheme 1 Model reaction used to study the Sonogashira cross-coupling 75 of iodoferrocenes and terminal alkynes.…”

“…Whilst large quantities of pure iodo-1 and 1,1'-diiodoferrocene 2 can now easily be obtained, the full synthetic exploitation of these useful starting materials may only be realized through 15 optimizing onward reaction conditions (enabling high product yields). Towards this end, increasing the typically low/moderate reactivity of iodoferrocenes 3 (versus aryliodides/bromides) under Sonogashira cross-coupling conditions was considered a primary target.…”

Phosphino‐amine (PN) Ligands for Rapid Catalyst Discovery in Ruthenium‐Catalyzed Hydrogen‐Borrowing Alkylation of Anilines: A Proof of Principle

“…As a first step, the parent aminoferrocene was synthesized from iodoferrocene [23] and NH3(aq) in the presence of a CuI-Fe2O3 catalyst, as described recently by Gasser et al [24] While the original protocol employed NaOH (2.3 equiv), in our hands omitting this base was beneficial, leading to partial suppression of the proto-deiodination side reaction and resulting in a 77% yield of aminoferrocene on a 3.5 mmol scale (see Supporting Info). This primary amine underwent smooth coupling with both electron-rich and electron-poor benzyl alcohols (Table 4, Ca-Cc).…”