Planar‐Chiral 1,1′‐Diiminoferrocenes [Fe{η5‐C5H3‐1‐(N=CHPh)‐2‐(C≡CAr)}{η5‐C5H4(N=CHPh)}] Containing a Bulky Ethynyl Substituent Adjacent to One of the Imino Groups
Year: 2025
Type: article
Abstract: The planar‐chiral stannylated diaminoferrocene [Fe{η5‐C5H3‐1‐(SnnBu3)‐2‐(NH2)}{η5‐C5H4(NH2)}] (A) and its diimine derivative [Fe{η5‐C5H3‐1‐(SnnBu3)‐2‐(N=CHPh)}{η5‐C5H4(N=CHPh)}] (B) gave unsatisfactory results in attempts to achieve Stille cross‐coupling reactions with PhBr in the presence of [PdCl2(PPh3)2] or [Pd(PPh3)4]/CuO as catalysts. Analogous attempts aiming at the Stille cross‐coupling of the iodo derivative [Fe{η5‐C5H3‐1‐I‐2‐(N=CHPh)}{η5‐C5H4(N=CHPh)}] (C) with PhSnnBu3 are equally fruitless, whereas Sonogashira cross‐coupling reactions of C are successfully performed with ethynylbenzene, ethynyl‐2,4,6‐trimethylbenzene, 4‐ethynyl‐1,1′‐biphenyl, 9‐ethynylphenanthrene, and 1‐ethynylpyrene, affording [Fe{η5‐C5H3‐1‐(N=CHPh)‐2‐(C≡CAr)}{η5‐C5H4(N=CHPh)}] (Ar = phenyl, mesityl, 1,1′‐biphenyl‐4‐yl, 9‐phenanthryl, and 1‐pyrenyl for 1, 2, 3, 4, and 5, respectively) in ≈60% yield under optimized conditions (C/ArC≡CH/[Pd(PtBu3)2]/CuI/NiPr2Et = 1/4/0.5/3/40, toluene, 70 °C, 16 h). 4 (Ar = 9‐phenanthryl) is structurally characterized by single‐crystal X‐ray diffraction (XRD). The suitability of the diimines of this study for metal chelation is demonstrated by reactions with [PdCl2(MeCN)2]. [PdCl2(C)] and [PdCl2(5)] are structurally characterized by XRD. The 1‐pyrenyl unit present in [PdCl2(5)] effectively blocks one side of the N,N‐chelated metal center by wall‐like steric shielding.
Institution: University of Kassel
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,050
OpenAlex ID: W4411412850