METAL-BETAINE INTERACTIONS .17. A STUDY OF INTRADIMER CU...CU DISTANCE VARIATION IN COPPER(II) BETAINE COMPLEXES CONTAINING [CU2(CARBOXYLATO-O,O')4L2]N+ SPECIES

Four copper(II) complexes of betaines, [Cu2(BET)4Cl2][Cu(BET)2Cl2]Cl2 (2), [Cu2 (pyBET)4Cl2]3 [CuCl4]2 Cl2 (3), [Cu2 (pyBET)4 (H2O)2] (NO3)4.2H2O (4), and [Cu2(ppBET)4(H2O)2](ClO4)4.4H2O (5), (BET = Me3N+CH2COO-; pyBET = C5H5N+CH2COO-; ppBET = C5H5N+CH2CH2COO-), have been prepared and characterized by X-ray crystallography. These complexes all contain dimeric [Cu2 (carboxylato-O,O')4L2] structures [basal Cu-O = 1.955(4) approximately 1.991(2), Cu ... Cu 2.602(1) approximately 2.759(1) angstrom] with the apical ligand L = Cl- in (2) and (3) [Cu-Cl = 2.415(1) approximately 2.436(3) angstrom] and L = H2O in (4) and (5) [Cu-OH2 = 2.158(4) approximately 2.192(3) angstrom]; also present are a discrete [Cu(BET)2Cl2] molecule with a compressed tetrahedral CuO2Cl2 chromophore involving two unidentate carboxylate ligands [Cu-O = 1.916(2), Cu-Cl = 2.254(l) angstrom] in (2), and a discrete C3v [CuCl4]2- anion in (3). Generally the intradimer Cu ... Cu distance may be correlated to the electronic repulsion of the metal-ligand bonds in the CuO4L chromophore, as well as the steric interaction between the carboxylate moieties and the apical ligand.