Dibenzo[c,g]fluorene: The Combination of Cyclopentadiene and 1,1′‐Binaphthyl in One Ligand

Synthesis of Optically Pure Helicene Metallocenes

“…In contrast, only afew examples of chiral Cp complexes with chirality originating from the helicity of the Cp ligand are known. [3][4][5] Katz et al reported Co and Fe complexes with ahelicene ligand with Cp moieties at the edge of its skeleton (Figure 2a). [4] Thec omplexes exhibited alarge absorption in the visible region and astrong signal in its circular dichroism (CD) spectra.…”

“…In 2007, Thiel et al made great contributions in the synthesis of as eries of metal complexes with dibenzo[c,g]fluorenyl (Dbf) ligand ( Figure 2b). [5] Although the Cp ligand in the complexes showed ah elical-chiral conformation in the crystal state owing to the axial chirality of the binaphthyl backbone, racemization proceeded rapidly at room temperature in solution. [5a] Recently,w er eported the synthesis of rac-9H-cyclopenta[1,2-c:4,3-c']diphenanthrene (LH), which has ar igid helical shape comprised of seven fused rings (Scheme 1).…”

“…Mono-helicene ferrocene (M)-1 Fe was also synthesized by reaction of deprotonated (M)-LH with one equivalent of [Cp*Fe-(MeCN) 3 ]OTf (Scheme 1c). Notably, [ 7]helicene La fforded optically pure helicene metallocenes,w hile optically pure complexes with [5]helicene Dbf could not be isolated owing to the rapid racemization of Dbf. [5a] Single crystals of the obtained complexes were analyzed by X-ray diffraction ( Figure 3, Table 1).…”

Synthesis of Optically Pure Helicene Metallocenes

“…[3][4][5] Katz et al reported Co and Fe complexes with ahelicene ligand with Cp moieties at the edge of its skeleton ( Figure 2a). [5] Although the Cp ligand in the complexes showed ah elical-chiral conformation in the crystal state owing to the axial chirality of the binaphthyl backbone, racemization proceeded rapidly at room temperature in solution. In 2007, Thiel et al made great contributions in the synthesis of as eries of metal complexes with dibenzo[c,g]fluorenyl (Dbf) ligand ( Figure 2b).…”

“…Synthesis of Ru complexes with [7]heliceneligands in a) racemic and b) optically pure forms, and c) opticallyp ure [7]helicene ferrocene. Notably, [ 7]helicene La fforded optically pure helicene metallocenes,w hile optically pure complexes with [5]helicene Dbf could not be isolated owing to the rapid racemization of Dbf. Ther eaction of deprotonated rac-LH with 0.5 equivalent of RuCl 2 (dmso) 4 afforded bis-helicene ruthenocene 2 as am ixture of (P,P)and (M,M)-2 (rac-2), and (P,M)-2 (meso-2)i na7:3r atio,i n 26 %total yield.…”