Structural Flexibility of the Hydrogen-Free Acceptor Ligand Octachloro-1,10-phenanthroline in Its Complexes with d10 Metal Ions

A remarkable pattern of structural diversity has been observed for the conformation of octachloro-1,10-phenanthroline (ocp) in its free form and in its d10 metal complexes [M(ocp)2]+, M = Cu, Ag, and Cl2Hg(ocp). Ocp:  C12Cl8N2, monoclinic, space group P21/c, a = 5.6390(10) A, b = 24.970(3) A, c = 10.4660(10) A, β = 101.33°, Z = 4; [Ag(ocp)2](PF6)·CH2Cl2, C25H2AgCl18F6N4P, monoclinic, space group P2/n, a = 13.185(2) A, b = 9.4740(10) A, c = 16.106(2) A, β = 92.05°, Z = 2; Cl2Hg(ocp)·2.5C6H6:  C27H15Cl10HgN2, triclinic, space group P1, a = 10.391(2) A, b = 12.911(3) A, c = 13.647(3) A, α = 103.53(3)°, β = 111.85(3)°, γ = 103.69(3)°, Z = 2. While ocp is virtually planar in the previously characterized ion [Cu(ocp)2]+, the analogous silver(I) complex contains slightly twisted ocp ligands. In contrast, both the free, noncoordinated ligand and its dichloromercury(II) complex exhibit distincly saddle-shaped ocp. Cl2Hg(ocp) in particular contains a rather distorted chelate ligand. Ab initio calculations at the 6...