Resolution of racemic tertiary phosphines of the types PAr1Ar2Ar3 (P1*) and PArR1r2 (P2*) have been achieved with chloro-bridged chiral Pd(II) complexes, (+)-di-μ-chloro-bis[(S)-N,N-dimethyl-α-phenylethylamine-2C,N]dipalladium (1) ([(SJ-Pd1]2), and -di-μ-chloro-bis[(R)-N,N-dimethyl-α-(2-naphthyl)ethylamine-3C,N]dipalladium (2) ([(R)-Pd2h), or with (+)-cis-dichlorobis[(S)-sec-butyl isocyanide]palladium (3) by virtue of the solubility difference between diasteromeric monophosphine compounds, [(S)-Pd1-P1*], [(R)-Pd2-P2*], or (RNC)(P1*)PdCl2. Racemic phospholene, PhPCH=C(Me)CH2CH2 (P3*), was resolved via the bisphospholene complex, [(R)-Pd2-(P3*)2]. Addition of the achiral diphos, Ph2PCH2CH2PPh2, caused the preferential crystallization of one diastereomeric complex leaving one enantiomeric phospholene ligand in solution. Chiral tertiary phosphines thus obtained are (optical purity and resolving agent) PPh(t-Bu)Me (77.8%, 2); PPh(t-Bu)(i-Pr) (~100%, 2), PhPCH⩵C(Me)CH2CH2 (43.6%, 2), PPh(α-Naph)-(p-PhC6H4) (—, 3), PPh(α-Naph)(p-MeOC6H4) (—, 3), P(α-Naph)Ph(o-MeC6H4) (—, 1), and PPh(α-Naph)(p-EtOC6H4) (—, 1). The molecular structure and absolute configuration of [(S)-isopropyl-tert-butylphenylphosphine][(R)-N,N-dimethyl-α-(2-naphthyl)ethyl-amine-3C,N]chloropalladium(II) has been determined by single-crystal x-ray diffraction methods. The compound crystallizes in the monoclinic space group C22-P21 with two molecules in the unit cell of dimensions a=10.409 (4) Å, b=10.094 (4) Å, c=13.151 (5) Å, (β=109.38 (2)°, and V=1303.5 Å3; pcalcd=1.397 and pobsd=1.39 g cm-3. The full-matrix least-squares refinement of the structure resulted in a final agreement index of 0.037 for the 3756 independent data for which Fo2 > 3σ(Fo2). The palladium complex has a distorted square-planar geometry. The tertiary phosphine is coordinated trans to the amine nitrogen atom while the chloro ligand (Pd-Cl=2.404 (2) Å) is opposite the ortho-metalated naphthyl ring (Pd-C=2.049 (2) Å). The Pd-P and Pd-N bond distances are 2.286 (2) and 2.167 (4) Å, respectively. The absolute configuration of the coordinated tertiary phosphine is S, thus confirming the predicted configuration based upon stereochemical correlations.
ASJC Scopus subject areas
- Colloid and Surface Chemistry