[n]Ferrocenophanes (n = 2, 3) with Nitrogen and Phosphorus in Bridging Positions

Abstract

The in situ prepared dilithio derivative of the known species 1-bromo-1'-(trimethylsilylamino)ferrocene (1) reacted with tBuPCl2 to form the first example of a [2]ferrocenophane ([2]FCP) bridged by nitrogen and phosphorus (2). Sulfurization of 2 followed by column chromatography on silica gel gave the expected [2]FCP with a tBu(S)PN(SiMe3) bridging moiety (3a) and its desilylated counterpart with a tBu(S)PNH bridging moiety (3b). The molecular structure of 3b was determined by single-crystal X-ray analysis (α = 18.40(11)°). Using a common synthetic methodology, two new 1-amino-1'-bromoferrocene derivatives were prepared, one species with a PhCH2 (6a) and another with a tBuCH2 group (6b) on nitrogen. Dilithiation of 6a followed by addition of tBuPCl2 gave a mixture of three constitutional isomers: the targeted [2]FCP (7a), the 1,1'-disubstituted ferrocene derivative (tBuPH)(PhCH═N)fc (8a), and the [3]FCP bridged by a (NH)(CHPh)PtBu moiety (9a). NMR spectroscopy revealed that 8a is the precursor for 9a. The salt-metathesis reaction of the dilithio derivative of 6b with tBuPCl2 exclusively gave the 1,1'-disubstituted ferrocene derivative (tBuPH)(tBuCH═N)fc (8b), which does not isomerize to the respective [3]FCP. DFT calculations at the M06/6-311+G(d,p) level were used to better rationalize these unexpected results.

N-Metallocenyl Ynamides: Preparation, Reactivity and Synthesis of ansa[3]-Ferrocenylamides

“…24 The reaction between 8a and 2 equivalents of (diacetoxyiodo)benzene (PIDA) in acetonitrile led to the isolation of ansa-ferrocene derivative 12a with 25% yield (Scheme 3). The unique structure of 12, quite different from previously reported nitrogen-containing ferrocenophanes, [32][33][34] encouraged us to optimize its synthesis (see SI for details).…”

Synthesis and coordination chemistry of (PNEt2)2-bridged [2]ferrocenophanes

“…[13][14][15][16][17] The significant strain of the ferrocene unit in both the free form and metal complex species might facilitate ring-opening reactions to afford a rich chemistry that provides ring-expansion and ring-opened monomers and polymers. [18][19][20] Phosphorus-bridged [2]ferrocenophanes have been reported by several groups, including ours, [21][22][23][24][25][26] but their chemistry is still unexplored compared with that of the [1]ferrocenophanes. Allcock et al reported the first diphospha [2]ferrocenophane with two pentavalent phosphorus atoms in the ansa bridge.…”

Tailoring the Fe → Pd interaction in cationic Pd(ii) complexesviastructural variation of the ligand scaffold of sterically demanding dppf-analogs and their P,N-counterparts

“…Although there are several synthetic strategies reported for compound 1, [73][74][75][76][77] due to low obtainable yields, 73,[75][76][77] and apparently impure final product, 73,74,76,77 a newly reported pathway, which involves Staudinger-type reaction on 1,1′-azidobromoferrocene (Scheme 1A), 78 was used for this compound. Compound 1 was initially purified by column chromatography, followed by a flask-to-flask sublimation, which resulted in bright colored golden yellow crystals, which were found suitable for characterization by single crystal X-ray diffraction (Fig.…”

“…Adapting a known procedure for reductive amination on aminoferrocenes, 77,79,80 compound 1 was further reacted with paraformaldehyde and NaCNBH 3 , in presence of glacial acetic acid to obtain N,N-dimethyl substituted 1,1′-azabromoferrocene 2 (Scheme 1B). When compound 2 was lithiated and in situ reacted with one equivalent of Ph 2 PCl or Mes 2 PCl, compound 3a and 3b were obtained in yields of 69% and 21%, respectively, calculated based on starting material 1 (Scheme 1B).…”