Structural Flexibility of the Hydrogen-Free Acceptor Ligand Octachloro-1,10-phenanthroline in Its Complexes with d 10 Metal Ions
1997; American Chemical Society; Volume: 36; Issue: 12 Linguagem: Inglês
10.1021/ic960837o
ISSN1520-510X
AutoresChristoph Titze, Wolfgang Kaim, Stanislav Záliš,
Tópico(s)Metal-Organic Frameworks: Synthesis and Applications
ResumoA 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) Å, b = 24.970(3) Å, c = 10.4660(10) Å, β = 101.33°, Z = 4; [Ag(ocp)2](PF6)·CH2Cl2, C25H2AgCl18F6N4P, monoclinic, space group P2/n, a = 13.185(2) Å, b = 9.4740(10) Å, c = 16.106(2) Å, β = 92.05°, Z = 2; Cl2Hg(ocp)·2.5C6H6: C27H15Cl10HgN2, triclinic, space group P1̄, a = 10.391(2) Å, b = 12.911(3) Å, c = 13.647(3) Å, 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 6-31G** level show a flat energy hypersurface for ocp with an absolute minimum at a saddle-shaped conformation and a second energy minimum, 2.7 kcal/mol higher, for the coplanar arrangement. Nonbonded interactions between the chlorine atoms are responsible for the structural flexibility and limited coordination ability of ocp; electronically, ocp is a good acceptor ligand with two stabilized and close-lying unoccupied π* orbitals but much reduced σ donor capacity.
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