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

The reaction of Rh2(O2CCH3)4 · 2CH3OH with the phosphine P(4-BrC6H4)2(C6H5), 2, results in the formation of the monometalated compound Rh2(O2CCH3)3[PC] · 2CH3CO2H (PC representing a metalated P(4-BrC6H4)2(C6H5)). The reaction involves selective metalation of the phosphine at one Br-substituted ring (12:1 isomer ratio). The reaction of Rh2(O2CCH3)3[(4-BrC6H3)P(4-BrC6H4)(C6H5)] · 2CH3CO2H, 4, with one additional mol of triphenylphosphine yields a mixture of two main stereoisomers Rh2(O2CCH3)2[(4-BrC6H3)P(4-BrC6H4)(C6H5)] [(C6H4)P(C6H5)2] · 2CH3CO2H, 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.

Graphical abstractTwo biscyclometalated compounds of formula Rh2(O2CCH3)2[PC] · [PC′] · 2CH3CO2H containing a mixed set of orthometalated phosphimes, P(4-BrC6H4)2(C6H5) and P(C6H5)3 have been obtained. The compounds contain a backbone configuration and a stereogenic centre. They have been resolved in the corresponding M and P enantiomers that show good enantioselectivities in catalytic transformation of α-diazocarbonyl compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide