Optically active asymmetric di(tertiary phosphines).: Crystal and molecular structure of [SP-4-3-(SP,S)]-{1-[(2-chlorophenyl)methylphosphino]-2-(dimethylphosphino)benzene-P,P′}{1-[1-(dimethylamino)ethyl]naphthyl-C2,N}palladium(II) hexafluorophosphate

Mono-deprotonation of the bis(secondary phosphine) (R-P*,R-P*)- and (R-P*,S-P*)-1,2-phenylenebis(methylphosphine) has been achieved using potassium in liquid ammonia to give a ca. 4 : 1 mixture of (+/-)-1-(dimethylphosphino)-2-(methylphosphino)benzene and 1,2-phenylenebis(dimethylphosphine) upon addition of a solution of methyl iodide in the same solvent. This mixture has been further treated with sodium in THF followed by the addition of 1,2-dichlorobenzene to give (+/-)-(2-chlorophenyl)(2-dimethylphosphinophenyl)methylphosphine and unchanged 1,2-phenylenebis(dimethylphosphine). The two di(tertiary phosphines) are readily separated by fractional distillation. Asymmetric di(tertiary phosphine) (+/-)-(2-chlorophenyl)(2-dimethylphosphinophenyl)methylphosphine has been resolved by separation via fractional crystallisation of internally diastereomeric palladium(II) complexes containing the racemic ligand and orthometallated (S)-dimethyl[1-(1-naphthyl)ethyl]amine. The absolute configuration of the R enantiomer of the ligand has been assigned by a crystal structure determination of the least soluble diastereomeric palladium(II) complex [SP-4-3-(S-P,S)]{1-[(2-chlorophenyl)methylphosphino]-2-(dimethylphosphino)benzene-P,P'}{1-[1-(dimethylamino)ethyl]naphthyl-C-2,N}palladium(II) hexafluorophosphate.