Endo and Exo coordination to cofacial binuclear copper(II) complexes

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A structural study of internal (endo) and external (exo) coordination to cofacial binuclear complexes is reported. Cu2(NBA)2(NBAH 2=3,3′-[2,7-naphthalenediylbis(methylene)]-bis(2,4- pentanedione)) is large enough to accommodate 2-methylpyrazine as an intramolecularly coordinated guest molecule. Cu2(NBA)2(μ-(2-Mepyz))·4CH2Cl 2, Cu2C53H58N2O8Cl 8, orthorhombic, space group Pnma (No. 62); a = 22.4674(11); b = 22.230(2); c = 11.4520(6) Å; V = 5719.6(6) Å3 (at 100 K); Z = 4; R = 0.058; Rw = 0.167 for 344 parameters and 5339 reflections with I > 2σ(I). The Cu2(NBA)2(μ-(2-Mepyz)) molecules possess crystallographic m symmetry, with the Cu⋯Cu vector (Cu⋯Cu′ 7.4801(8) Å) perpendicular to the mirror plane; this requires disorder in the 2-Mepyz guests. The two "Cu(acac)2" moieties (acacH = 2,4-pentanedione) are not quite parallel (dihedral angle between (acac)2 planes = 3.93(7)°), forming a slightly wider opening on the side of the methyl group in the 2-Mepyz guest. On the other hand, the cavity in Cu2(XBA)2 (XBAH2 = 3,3′-[1.3-phenylenebis(methylene)]-bis(2,4-pentanedione)) is smaller, so that CH3CN must bind externally. Cu2(XBA)2(CH3CN)2·1.5CH 3CN·H2O, Cu2C43H52.5N3.5O9, monoclinic, space group P21/c (No. 14); a = 11.7361(16); b = 14.197(3); c = 13.299(3) Å; β= 92.22(2)°; V = 2214.3(7) Å3 (at 100 K); Z = 2; R = 0.044; Rw = 0.124 for 275 parameters and 4983 reflections with I > 2σ(I). This structure contains centrosymmetric Cu2(XBA)2 units (Cu⋯Cu′ 4.8302(12) Å) with externally coordinated CH3CN ligands. The crystal packing in Cu2(NBA)2(μ-(2-Mepyz))·4CH2Cl 2, which contains close π contacts between layers of Cu2(NBA)2(μ-(2-Mepyz)) moieties, is also similar to that in three other crystalline host-guest adducts M2(NBA)2(μ-G). Cu2(XBA)2(CH3CN)2·1.5CH 3-CN·H2O does not contain similar layers of molecules, presumably because the adduct molecules do not have the same type of exposed flat surfaces.

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Journal of Inclusion Phenomena

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