Endo and Exo coordination to cofacial binuclear copper(II) complexes
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.
Publication Source (Journal or Book title)
Journal of Inclusion Phenomena
Maverick, A., Billodeaux, D., Ivie, M., Fronczek, F., & Maverick, E. (2001). Endo and Exo coordination to cofacial binuclear copper(II) complexes. Journal of Inclusion Phenomena, 39 (1-2), 19-26. https://doi.org/10.1023/A:1008183506115