ORTHO-METALATION OF P(M-MEC6H4)3 IN DIRHODIUM(II) TETRAACETATE - MOLECULAR-STRUCTURE OF RH2(O2CCH3)2[(M-MEC6H3)P(M-MEC6H4)2]2(HO2CCH3)2.CH3CO2H

The thermal reaction of Rh2(O2CCH3)4(MeOH)2 and P(m-MeC6H4)3 in a 1:2 molar ratio in acetic acid yielded Rh2(O2CCH3)2[(m-MeC6H3)P(m -MeC6H4)2]2(HO2CCH3)2. Purple monoclinic crystals of this compound and one molecule of acetic acid, space group P21/c, were obtained by evaporation of a solution of the original reaction product in acetic acid/CH2Cl2 mixture. The unit cell parameters are a = 21.346(3), b = 11.909(2), c = 20.071 Å, β = 97.98(1)° and Z = 4. The structure consists of a dinuclear rhodium core bridged by cisoid acetate groups and two ortho-metallated phosphine ligands. The ortho-metallation occurs at the least sterically hindered carbon atom which is trans to the methyl substituent. If the reaction is performed in a 1:1 molar ratio, a monometallated species Rh2(O2- CCH3)3[(m-MeC6H3)P(m-MeC6H4)2](HO2CCH3)2 is obtained in high yield, with the above mentioned doubly metallated compound as a minor reaction product. © 1990.