Macrocyclic Rhodium(III) Hydrides and a Monomeric Rhodium(II) Complex

Several mononuclear N₄-macrocyclic Rh(III) hydrides were prepared and characterized in the solid state and in solution. ¹H NMR, IR, and UV data are reported. The complex {trans-(Cl)([14]aneN₄)RhH}₂(ZnCl₄)·dmso (1· dmso) crystallizes in the triclinic system, space group P1̄, in a unit cell of dimensions a = 10.680(3) Å, b = 13.460(3) Å, c = 14.277(4) Å, α = 86.49(2)°, β = 83.18(2)°, γ = 66.64(2)°. The data refined to a final value of R = 0.070 and R_w, = 0.13 based on 2687 observed reflections. UV photolysis of chloride-free (H₂O)L¹RhH²⁺ results in homolytic Rh−H bond cleavage. The rhodium(II) product, L¹Rh(H₂O)²⁺, was characterized by ESR and UV spectroscopies. This species survives in acidic aqueous solution for over half an hour at room temperature. The photolysis of (H₂O)L¹RhH²⁺ in the presence of O₂ produces the superoxorhodium(III) ion, trans-L¹RhOO²⁺.