X-ray Crystallographic Studies of the Products of Oxidative Additions of Iodine to Cyclic Trinuclear Gold(I) Complexes: Directional Effects for Au-I.I-Au Interactions.

The crystal structures of cyclic trinuclear organogold compounds, Au(3)I(n)()(CH(3)N=COCH(3))(3) (n = 2, 4, 6) reveal that pairs of iodine atoms are added successively to each of the gold atoms in the triangular complexes. Deep red needles of Au(3)I(6)(CH(3)N=COCH(3))(3).CH(2)Cl(2) crystallize in the monoclinic space group P2(1)/c, with a = 14.762(4) Å, b = 8.723(3) Å, c = 22.278(6) Å, and beta = 91.58(2) degrees at 123 K with Z = 4. Refinement of 6591 reflections and 164 parameters yielded R = 0.055. The structure consists of columns of the molecular units united by weak iodine.iodine interactions which range in length from 3.636(2) to 3.716(2) Å. Within the molecular unit, all iodine.iodine distances are well beyond the sum of their van der Waals radii and fall in the range from 3.965(2) to 4.211(2) Å. The gold coordination is significantly distorted from planarity with I-Au-I angles of ca. 163 degrees. In Au(3)I(6)(CH(3)N=COCH(3))(3) the intermolecular I.I interactions are significantly shorter than the intramolecular I.I contacts. Red parallelepipeds of the tetraiodo complex, Au(2)I(4)Au(CH(3)N=COCH(3))(3), crystallize in the triclinic space group P&onemacr;, with a = 7.404(2) Å, b = 9.278(2) Å, c = 16.331(3) Å, alpha = 80.77(3) degrees, beta = 78.68(3) degrees, and gamma = 81.85(3) degrees at 123 K with Z = 2. Refinement of 4963 reflections and 124 parameters yielded R = 0.048. No noteworthy intermolecular contacts are present in this compound. Orange-red hexagonal plates of the diiodo complex, AuI(2)Au(2)(CH(3)N=COCH(3))(3), crystallize in the monoclinic space group P2(1)/c, with a = 9.309(4) Å, b = 13.597(4) Å, c = 14.899(5) Å, and beta = 101.26(3) degrees at 123 K with Z = 4. Refinement of 4133 reflections and 121 parameters yielded R = 0.064. This structure consists of discrete molecular units displaying no noteworthy inter- or intramolecular contacts.