Sym. Chooi et al., OPTICAL RESOLUTIONS AND CHELATING PROPERTIES OF -OR-MINUS)-[2-(METHYLSULFINYL)ETHYL]DIPHENYLARSINE AND ITS PHOSPHORUS ANALOG, Inorganic chemistry, 32(22), 1993, pp. 4812-4818
An optical resolution of the asymmetric chelating agents (+/-)-[Ph2ECH
2CH2S(O)Me] (E = As or P) has been achieved via fractional crystalliza
tion of a pair of diastereomeric palladium(II) complex cations contain
ing the appropriate sulfinyl-substituted ligand and ortho-metalated (S
)-(1-(dimethylamino)ethyl)naphthalene. The crystal and molecular struc
ture of the perchlorate salt of the less soluble phosphine-palladium c
omplex has been determined. Crystal data: monoclinic pale yellow prism
s, P2(1), a = 10. 147(2) angstrom, h = 10.955(2) angstrom, c = 26.888(
5) angstrom, beta = 97.76(2)-degrees, Z = 4, and R = 0.0302. The optic
ally pure compound, [alpha]D-16.1-degrees (c 1.0, dichloromethane), cr
ystallizes as a pair of interconvertible conformers arising from the a
doption of different helicities by the nonplanar chelate rings. In bot
h conformers, the sulfinyl-substituted phosphine coordinates to the pa
lladium via phosphorus and oxygen with the uncoordinated sulfur stereo
center of S absolute configuration. Optically pure (S)-[2-(methylsulfi
nyl)ethyl]-diphenylphosphine, [alpha]D+67.5-degrees (c 1.0, dichlorome
thane), was displaced from the resolving palladium complex with 1,2-bi
s(diphenylphosphino)ethane. The (R)-(-)589 enantiomer of the phosphine
ligand was obtained in a state of 85% optical purity from the residua
l mixture of diastereomeric complexes and was subsequently brought to
purity by fractional crystallization of the corresponding enantiomorph
ic complex containing (R)-(1-(dimethylamino)ethyl)naphthalene. Enantio
merically pure forms of [2-(methylsulfinyl)ethyl]diphenylarsine are ob
tained similarly from the corresponding resolved palladium complexes b
y treatment with cyanide. The various enantiomeric forms of the sulfin
yl-substituted ligands are capable of coordinating to square-planar pl
atinum metal ions via their E, E-0, or E-S donor atoms The mode of coo
rdination is governed by the stereoelectronic factors of the product c
omplexes.