Chiral Rhodium(I) Complexes of 1,2-Bis-(chloroalkoxyphosphanyl)- and 1,2-Bis-(amidoalkoxyphosphanyl)-1,2-dicarba-closo-dodecaboranes(12)

1,2-Bis(chloroalkoxyphosphanyl)-1,2-dicarba-closo-dodecaboranes(12) and 1,2-bis(amido-(-)-menthyloxyphosphanyl)-1,2-dicarba-closo-dodecaboranes(12) were synthesised by the reaction of dilithiated 1,2-dicarba-closo-dodecaborane(12) with the corresponding dichloro- or chloroamidophosphite. For 1,2-bis-(chloro-1-adamantyloxyphosphanyl)-1,2-dicarba-closo-dodecaborane(12) epimerisation in solution was observed and the free activation enthalpy was determined experimentally and theoretically. An indirect determination of the meso configuration was obtained by formation of the corresponding molybdenum tetracarbonyl complex. Chlorido-bridged dimeric chiral rhodium(I) complexes showing planar or folded Rh2Cl2 rings were prepared. Density functional calculations indicate that steric and packing factors play a much more significant role than electronic effects in influencing the bending of the rhodium complexes.