Development of asymmetric C-H bond activation mediated by new transition metal complexes having a metal centered chirality

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1.We have developed a new method for the construction of a stereogenic center on the metal by the diastereoselective addition of the Meerwein reagent (Me_3OBF_4) to rhodium carbonyl complexes having the Cp'-P ligand, [{3-(R)Ind-P}_<n=2>]H [R = H(a), Et(b), Cy(c), 1'S,2'S,5'R-neomenthyl (NM) (d), 1'R,2'R,5'R-neoisomenthyl (NIM) (e)], in which an indenyl group having a substituent (R) at the 3-position and a diphenylphosphino group are connected by an ethylene group.2.The Index ligands, in which an indenyl group and an oxazoline ring are connected by an ethylene or propylene spacer, have been designed and their iridium(III) and rhodium(III) cationic complexes having a stereogenic center at the metal have been prepared stereoselectively by the ligand exchange reaction of their neutral complexes bearing two prochiral iodido ligands with AgOTf.3.We would like to show the preparation of π-allyl iridium(III) and rhodium(III) complexes having the Cp'-P ligand by using the oxidative addition method. In this case, if a substituent is attached to one of the terminal carbons of the π-allyl ligand, the π-allyl complexes bearing the Cp'-P ligand have a chirality on the metal center. In other words, control of the coordination mode of the p-allyl ligand in the complexes bearing the Cp'-P ligand is the same meaning as control of the stereochemistry around a stereogenic center arising at the metal. Since several substituents are easily introduced at the 3-position of the indenyl group of the Cp'-P ligand, we examined the effect of the substituent to the selectivity of π-allyl complexes. Higher selectivity of the major isomer was obtained when bulkier substituents were introduced at the indenyl group in the Cp'-P ligand.