Chiral Tripodal Ligands Bearing a Phosphite Donor Group: Synthesis and Coordination Chemistry

Article abstract of DOI:10.1002/cber.19961290617

The mechanism of the reaction of epichlorohydrine (O-CH₂-CH-CH₂Cl) (I) with lithium phosphides is analysed. A neighbouring-group mechanism has been found to be the essential driving force in this reaction, Monophosphanyl alcohols such as HOCH(CH₂P(Ph)₂)(CH₂Cl) (2) and epoxides (Ph)₂PCH₂-CH-CH₂-O (3) are characterized as intermediates. The mechanism leads to a rapid one-pot method for the synthesis of chiral racemic as well as enantiomencally pure bis(phosphanyl) alcohols HOCH(CH₂PR₂){CH₂PR₂) (4). The resulting bis(phosphanyl) alcohols 4 react easily with X₂PCl (X= Cl; Ph; or X₂= 1,2-ethanedioxy-i 2,2′-biphenyldiyldi-oxy-) to yield the mixed donor group tripodal ligands X₂POCH(CH₂PR₂)(CH₂PR₂) (5, 8) containing both phosphite, phosphinite or phosphorodichloridite and phosphane donor groups. The identity of these compounds were proved by 'H-, ³¹P- and ¹³C-NMR spectroscopy, mass spectra, microanalysis as well as X-ray analysis. The coordination capabilities of these novel ligands are demonstrated by the synthesis and characterization of a (cyclooctadiene)rhodium complex {[(5c)Rh(I)COD]PF₆) (7) of the ligand 5c, exhibiting the typical hetero-bicyclooctane tripod metal cage of this type of tripod complexes. VCH Verlagsgesellschaft mbH, 1996.