RESOLUTION OF A PLANAR-CHIRAL PLATINUM(II) COMPLEX - CRYSTAL AND MOLECULAR-STRUCTURE OF [SP-4-2-A]-(+)(589)-[PTCL(ACHIRAPHOS)(R-PMENPH(2))]PF6[ACHIRAPHOS= (R-ASTERISK,S-ASTERISK)-2,3-BIS(DIPHENYLPHOSPHINO)BUTANE R-PMENPH(2)=[1(R)-(1-ALPHA,2-BETA,5-ALPHA)]-DIPHENYLMENTHYLPHOSPHINE]

The new meso ligand (R*,S*)-2,3-bis(diphenylphosphino)butane (achiraphos) has been synthesized and used to prepare the prochiral square-planar meso complex [PtCl2(achiraphos)]. Displacement of one or the other of the enantiotopic chlorine atoms in the complex with [1R-(1 alpha,2 beta,5 alpha)]-diphenylmenthylphosphine (R-PMenPh(2)), and subsequent treatment of the intermediate salts with ammonium hexafluorophosphate, affords the diastereomeric complexes [SP-4-2-A]- and [SP-4-3-C]-[PtCl(achiraphos)(R-PMenPh(2))]PF6, which are epimeric at planar-chiral platinum(II). The homochiral SP-4-2-A epimer, C50H57ClF6P4Pt, [alpha](589)+22.4 degrees (c0.85, acetone), crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 9.900(3) Angstrom, b = 15.559(4) Angstrom, c = 32.789(10) Angstrom, Z = 4, R = 0.036, and R(w) = 0.042 for 3805 unique data having I> 3 sigma(I). The geometry around the platinum atom in the complex is square-planar with the R-PMenPh(2) ligand situated trans to the diphenylphosphino group attached to the S carbon of the achiraphos. The optically pure complex is configurationally stable in solution in the absence of chloride.