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Induction of Planar Chirality in Formation of (η51-1-(1-Cyclohexyl-2-(diphenylphosphino)ethyl)indenyl)carbonylrhodium and (η51-1-(2-Phenyl-2- (diphenylphosphino)ethyl)indenyl)carbonylrhodium

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journal contribution
posted on 2001-09-18, 00:00 authored by Daniel C. Brookings, Stephen A. Harrison, Richard J. Whitby, Barry Crombie, Ray V. H. Jones
The enantiopure bidentate indenyl−phosphine ligands (1S)-[2-(3H-inden-1-yl)-1-phenylethyl]diphenylphosphine (9) and [(2R)-2-cyclohexyl-2-(3H-inden-1-yl)ethyl]diphenylphosphine (18) were synthesized in 20% yield and three steps from (R)-styrene oxide and in 61% yield and four steps from vinylcyclohexane, respectively. In both cases ring opening of a spirocyclopropane-1,1‘-indene with potassium diphenylphosphide was a key step. Addition of the lithium salts of 9 and 18 to [Rh(μ-Cl)(CO)2]2 gave (η51-indenyl-CH2CH(Ph)PPh2)RhCO and (η51-indenyl-CH(Cy)CH2PPh2)RhCO as 75:25 and 78:22 mixtures of diastereoisomers, from which the major complexes were readily obtained by crystallization. The chiral centers in the linking chain β and α to the indenyl ring had thus induced good planar chirality of the complexed indenyl moiety. Both complexes were characterized by X-ray crystallography.