2.1.3. Reaction with phosphinites
The basicity of phosphinites is intermediate between those of phosphines
and phosphites. The reaction of K+[HFe(CO)4]− with PPh2OMe (h=132°, pKa
=2.69) in THF leads to the monosubstituted hydridocarbonylferrate
K+[HFe(CO)3(PPh2OMe)]− (Eq. (16)) [43], as in the case of phosphites.
K+[HFe(CO)4]−+PPh2OMe CA THF
−CO
K+[HFe(CO)3(PPh2OMe)]−
85%
(16)
2.1.4. Reaction with phosphinite–ammonium ligands
The reactivity of K+[HFe(CO)3{P(OMe)3}]− for the selective reduction of
a-dicarbonyl compounds [13] opens the way to possible enantioselective reductions
by introducing a chirality centre on the phosphorus ligand. Beyond this possibility,
a new concept has been introduced which relies on the zwitterionic control of the
chirality transfer [44]. Zwitterionic, chiral non-racemic monosubstituted hydridocarbonylferrates
have been synthesized from ‘‘ephosiums’’, which are new phosphinite–
ammonium ligands derived from the ephedrine skeleton (Eq. (17)).