Unligated dirhodium tetra(trifluoroacetate): preparation, crystal structure and electronic structure

The title compound, Rh₂(O₂CCF₃)₄, without any exogenous axial ligands, has been obtained in crystalline form by sublimation. Its crystal structure has been determined: space group P1 with α = 5.2499(5), b = 8.491(2), c = 9.172(2) A ̊, α = 88.80(2), β = 88.53(1), γ = 76.43(1)°, V = 397.3(1) A ̊³, Z = 1. The molecules are linked by axially ligating each other to form infinite chains. The Rh-Rh distance is 2.3813 (8) Å. The volatility of Rh₂(O₂CCF₃)₄ should allow spectrospcopic study of the isolated molecules and therefore the electronic structure has been treated by the SCF-Xα-SW method. The level ordering and composition show significant differences from those of Rh₂(O₂CH)₂, although in both molecules there is a strong Rh-Rh σ bond. Ionizatio potential have been estimated by the transition state method.