New Media for Classical Coordination Chemistry: Phase Transfer of Werner and Related Polycations into Highly Nonpolar Fluorous Solvents

Optimized
procedures for the previously reported conversions of
1,3-diiodo­benzene and perfluoro­hexyliodide (Rf6I; copper, DMSO, 140 °C) to 1,3-C6H4(Rf6)2 (3; 86–70%) and 3 to Br­(3,5-C6H3(Rf6)2 (2; NBS, H2SO4/CF3CO2H; 88–75%) are described. The latter is converted
(t-BuLi, BCl3) to the “fluorous
BArf” salt NaB­(3,5-C6H3(Rf6)2)4 (1 or NaBArf6; 77–70%), as given earlier. When orange aqueous solutions
of [Co­(en)3]­Cl3 (en = ethylene­diamine)
are treated with perfluoro­(methyl­cyclo­hexane) (PFMC) solutions
of 1 (1:3 mol ratio), the aqueous phase decolorizes and
[Co­(en)3]­(BArf6)3 can be isolated
from the fluorous phase (96%). Similar reactions with the trans-1,2-cyclo­hexane­diamine analogue [Co­(R,R–chxn)3]­Cl3 and [Ru­(bipy)3]­Cl2 give [Co–(R,R–chxn)3]­(BArf6)3 (92%) and [Ru­(bipy)3]­(BArf6)2 (95%). All of these salts are isolated
as hydrates and exhibit toluene/PFMC partition coefficients of ≤1:≥99,
establishing that the anion BArf6– can
efficiently transport polar polycations into highly nonpolar fluorous
phases. When equal volumes of CH2Cl2 and PFMC
are charged with the “nonfluorous” BArf (B­(3,5-C6H3–(CF3)2)4) salt [Co­(en)3]­(BArf)3 and 3.0
equiv of the fluorous salt NaBArf6, the cobalt trication
partitions predominantly into the fluorous phase (64:36). The arene 2 crystallizes in a polar space group (tetragonal, I4, Z = 8) with fluorous and nonfluorous
domains and all eight bromine atoms located essentially on one face
of the unit cell.