Chen, Jiawei Kuate, Alain C. Tagne Lalancette, Roger A. Jäkle, Frieder Heteroatom-Bridged <i>ortho</i>-Biferrocenes: Stereoselective Synthesis, Structural Features, and Electrochemical Properties A versatile synthetic protocol is described for the synthesis of heteroatom-bridged biferrocene derivatives, including the symmetric species <b>2-SnSn</b> and the planar-chiral species <b>2-SnSi</b>, <b>2-BSi</b>, and <b>2-SnP</b>. Treatment of (p<i>R</i>,<i>S</i><sub>S</sub>)-2-lithio-1-(<i>p</i>-tolyl­sufinyl)-ferrocene with 0.5 equiv of Me<sub>2</sub>SnCl<sub>2</sub> afforded the tin-bridged biferrocene <b>1-Sn</b>. A second Sn, Si, or P bridge was then incorporated by substitution of the sulfinyl group in the ortho-position with a dimethylstannyl, dimethylsilyl, or <i>tert</i>-butylphosphino group, respectively, to give the doubly bridged biferrocenes <b>2-SnSn</b>, <b>2-SnSi</b>, and <b>2-SnP</b>. The dimethylstannyl moiety of <b>2-SnSi</b> was subsequently replaced with a borane bridge via a two-step transmetalation procedure comprising treatment with HgCl<sub>2</sub>, followed by PhBCl<sub>2</sub>. The formation of ferrocene-fused six-membered heterocycles was confirmed by multinuclear NMR spectroscopy and high-resolution MS analyses. The stereochemical configuration of the chiral biferrocenes <b>2-SnSi</b>, <b>2-SnP</b>, and <b>2-BSi</b> was studied by single-crystal X-ray diffraction, chiral HPLC, and optical rotation measurements. The redox characteristics and absorption properties were investigated as well. The longest wavelength absorption experienced a bathochromic shift and an increase in intensity for <b>2-BSi</b> relative to <b>2-SnSn</b> and <b>2-SnSi</b>, indicative of significant charge transfer character. The cyclic voltammograms of <b>2-SnSn</b> and <b>2-SnSi</b> displayed two separate one-electron oxidations as expected for the presence of two ferrocene units in close proximity to one another. The incorporation of boron in <b>2-BSi</b> resulted in an anodic shift of both oxidation waves and an enlarged peak potential separation. The chemical oxidation of <b>2-BSi</b> was carried out with [Ag­(CH<sub>2</sub>Cl<sub>2</sub>)]­{Al­[OC­(CF<sub>3</sub>)<sub>3</sub>]<sub>4</sub>}, and the reaction was monitored by NMR spectroscopy. Attempts to crystallographically characterize the corresponding doubly oxidized species proved unsuccessful. p R;SnSn;SnSi;multinuclear NMR spectroscopy;0.5 equiv;charge transfer character;anodic shift;dimethylstannyl moiety;cyclic voltammograms;MS analyses;Stereoselective Synthesis;oxidation waves;chiral HPLC;biferrocene;HgCl 2;bathochromic shift;transmetalation procedure;wavelength absorption;chemical oxidation;PhBCl 2;rotation measurements;ferrocene units;BSi;sulfinyl group;2 SnCl 2;P bridge;redox characteristics;Electrochemical Properties;Structural Features;SnP;species;borane bridge;stereochemical configuration;NMR spectroscopy;absorption properties;butylphosphino group 2016-06-01
    https://acs.figshare.com/articles/journal_contribution/Heteroatom-Bridged_i_ortho_i_-Biferrocenes_Stereoselective_Synthesis_Structural_Features_and_Electrochemical_Properties/3409039
10.1021/acs.organomet.6b00272.s001