SYNTHESIS OF (1R,1'S)-(DIPHENYLPHOSPHINO)ETHYL]BENZENE AND (1S,1'S),(1R,1'R)-1,3-BIS[1-(DIPHENYLPHOSPHINO)ETHYL]BENZENE DERIVATIVES AND THEIR CYCLOMETALATION REACTIONS WITH PLATINUM(II) COMPOUNDS - X-RAY CRYSTAL-STRUCTURES OF [2,6-BIS[(DIPHENYLPHOSPHINO)METHYL]PHENYL]CHLOROPALLADIUM(II), [(1R,1'S)-2,6-BIS[1-(DIPHENYLPHOSPHINO)ETHYL]PHENYL]CHLOROPLATINUM(II), AND [(1R,1'R),(1S,1'S)-2,6-BIS[1-(DIPHENYLPHOSPHINO)ETHYL]PHENYL]CHLOROPLATINUM(II)

Equimolecular amounts of the ligands (1S,1'S),(1R,1'R)-1,3-bis[l-(diphenylphosphino)ethyl]benzene, rac-form, and of the corresponding meso-form, were obtained by two methods. The first involved the reaction of 1,3-bis[(diphenylthiophosphino)methyl]benzene (1) with n-butyllithium followed then with methyl iodide, (2) separation of the rac- and meso-forms of the products by fractional crystallization, and (3) their desulfurization with tri-n-butylphosphine. In the second method the methylation reaction was carried out on 1,3-bis[(diphenylphosphino)methyl]benzene-bisborane and the borane removed from the products by reaction with diethylamine. The complexes rac-[(1S,1'S),(1R,1'R)-1,3-bis[1-(diphenylphosphino)ethyl]phenyl]chloroplatinum(II), 9a,b, and the corresponding meso-form, 9c, were obtained by reacting the respective phosphines either with cis-[PtCl2(Pph3)2], followed by elemental sulfur, or with [Pt2(mu-Cl)2(eta3-2-MeC3H4)2]. Reaction of the above complexes with AgCF3SO3 gave the corresponding trifluoromethanesulfonates while the action of AgPF6 and (R)-methyl-4-tolyl sulfoxide gave the corresponding sulfoxide complexes as their PF6 Salts, 24a,b and 24c, respectively. The pure isomeric forms 24a and 24b could not be obtained by fractional crystallization. The complex [2,6-bis[(diphenylphosphino)methyl]phenyl]methylplatinum, when reacted with methyllithium, followed by methyl iodide, gave a mixture of rac-[(1S,1'S),(1R,1'R)-2,6-bis[l-(diphenylphosphino)ethyl]phenyl]methylplatinum 21a,b, and the corresponding meso-form, 21c, in ratios varying between 14 and 37 % of the former and the remainder of the latter, depending on the reaction temperature. Similar results were obtained when LDA was used as a base. Deprotonation of either pure 21a,b and 21c with methyllithium, followed by hydrolysis, gave isomeric mixtures with ratios corresponding to those quoted above. However, when LDA was used for this reaction, 21a,b was obtained in 45% yield. The X ray crystal structures of [2,6-bis[(diphenylphosphino)methyl]phenyl]chloropalladium, 7a, and. of 9a,band 9c are reported. Their structural features are very similar to those of several related compounds, the only significant difference between 9a,b and 9c being the steric repulsion between a terminal phenyl group and the equatorial methyl substituent in the latter compound.