Rhodium (II) compounds with functionalized metalated phosphines as bridging ligands

Abstract

The reaction of Rh 2(O 2CCH 3) 4 · 2CH 3OH with the phosphine P(4-BrC 6H 4) 2(C 6H 5), 2, results in the formation of the monometalated compound Rh 2(O 2CCH 3) 3[PC] · 2CH 3CO 2H (PC representing a metalated P(4-BrC 6H 4) 2(C 6H 5)). The reaction involves selective metalation of the phosphine at one Br-substituted ring (12:1 isomer ratio). The reaction of Rh 2(O 2CCH 3) 3[(4-BrC 6H 3)P(4-BrC 6H 4)(C 6H 5)] · 2CH 3CO 2H, 4, with one additional mol of triphenylphosphine yields a mixture of two main stereoisomers Rh 2(O 2CCH 3) 2[(4-BrC 6H 3)P(4-BrC 6H 4)(C 6H 5)] [(C 6H 4)P(C 6H 5) 2] · 2CH 3CO 2H, 5a and 5b, that were isolated as pure compounds. These two compounds were resolved in the corresponding M and P enantiomers as trifluoroacetate derivatives that show good enantioselectivities in catalytic transformation of α-diazocarbonyl compounds.