Preparation and Stereochemistry of Cobalt(III) Complexes Containing 2,11-Diphenyl-5,8-diaza-2,11-diphosphadodecane or (4<i>S</i>,9<i>S</i>)-4,9-Dimethyl-2,11-diphenyl-5,8-diaza-2,11-diphosphadodecane, (C6H5)(CH3)PCH2CHRNHCH2CH2NHCHRCH2P(CH3)(C6H5) (R=H or CH3)

Abstract

Abstract New quadridentate ligands having two chiral phosphorus donor atoms, 2,11-diphenyl-5,8-diaza-2,11-diphosphadodecane (mp-PNNP) and (4S,9S)-4,9-dimethyl-2,11-diphenyl-5,8-diaza-2,11-diphosphadodecane (SS(C)-mp-PNNP), and their cobalt(III) complexes, trans-[CoCl2(mp- or SS(C)-mp-PNNP)]+ and cisβ-[Co(acac)(mp- or SS(C)-mp-PNNP)]2+ (acac=2,4-pentanedionate ion) were prepared and characterized. For both mp- and SS(C)-mp-PNNP, the dichloro and acac complexes formed three and four isomers, respectively, which were separated by column chromatography or fractional crystallization. No cisα-acac complex was yielded. The acac complexes of SS(C)-mp-PNNP formed a Λ-isomer stereoselectively. The absolute configurations of the phosphorus donor atoms in the SS(C)-mp-PNNP complexes were assigned on the basis of the 1H NMR and CD spectra. It was shown that the phosphorus donor atoms at chemically unequivalent coordination positions in cisβ-[Co(acac)(SS(C)-mp-PNNP)]2+ give remarkably different vicinal effects on the CD spectra.