Optically active co-ordination compounds. Part VII. Tris-complexes of (+)-hydroxymethylenecamphor

Abstract

The tris-complexes of (+)-hydroxymethylenecamphorate with chromium(III), cobalt(III), and rhodium(III) have been investigated in detail. The geometrical-optical isomers obtained pure are characterised by studies of electronic, and proton resonance spectra, and Cotton effect. The isomers obtained from cobalt(III) are D-1,2,3-(–)[Co(+hmc)₃] and D-1,2,6-(–)-[Co(+hmc)₃], while the sole isolable product containing chromium(III) is D-1,2,6-(+)-[Cr(+hmc)₃], though an unstable L-isomer may also exist. However, with rhodium(III), the isomers D-1,2,6-(–)-[Hh(+hmc)₃] and an L-isomer, probably L-1,2,6(+)-[Rh(+hmc)₃] were isolated. A distinction is made between kinetic and thermodynamic control of stereoselectivity in complexes. The absolute configurations of all the isolated isomers of [M(+hmc)₃] are given. The variation of optical rotatory power of (–)-[Co(+hmc)₃] as a function of solvent is presented, and correlated with properties of the solvent and of the complex, in particular its absorption spectrum.