Chiral phosphoramidite ligands based on 8-chloroquinoline and their rhodium(III), palladium(II), and platinum(II) complexes

The new chiral ligands 2-butyl-8-chloro-1-(4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cyclo-hepten-6-yl)-1,2-dihydroquinoline (BIPHENPHOSHQUIN, 3) and 2-butyl-8-chloro-1-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a']- dinaphthalen-4-yl)-1,2-dihydroquinoline (BINAPHOSHQUIN, 4; 4a: SaRC, 4b: SaSC) have been synthesized starting from the rigid backbone of 8-chloroquinoline. The reactions of 3 and 4 with rhodium(I), palladium(II), and platinum(II) substrates are reported. The reaction of 3 with [Rh(CO)(2)Cl](2) in a 2:1 molar ratio in hexane afforded a binuclear chloro-bridged rhodium(III) species by intramolecular oxidative addition of the C-Cl bond of ligand 3 across the rhodium(I) centers. The rhodium(III) complex 5, incorporating the enantiomers SaRC-3 and RaSC-3, has been fully characterized by X-ray diffractometry. Reactions of [Pd(PhCN)(2)Cl-2] with the ligands 3 and 4a in 1:2 molar ratio in toluene afforded the products cis-[Pd(3)(2)Cl-2] (9) and cis-[Pd(4a)(2)Cl-2] (10). Similarly, reaction of [Pt(COD)I-2] with 4a in a 1:2 molar ratio afforded the complex cis-[Pt(4a)(2)I-2] (11). An X-ray analysis has been carried out to obtain information on the effect of the ligand 4a on the overall structure of 11.