Coordination properties of β-alanine: new complexes with some transition metals cobalt(II), nickel(II), and copper(II)

The neutral six-coordinated tetragonal Co(β-ala)2•2H2O complex(β-ala = NH2CH2CH2COO−) was prepared. In this complex β-alanine acts as an O,N-chelating agent, as in the known Cu(β-ala)2•6H2O and Ni(β-ala)2•3H2O complexes. We also prepared some complexes of a type that is new for β-alanine, with stoichiometries such as M(β-alaH)2X2, M(β-alaH)4(ClO4)2 (M = Co and Ni), Cu(β-alaH)3(ClO4)2, and Cu(β-alaH)Cl2[Formula: see text] in which the ligand acts as a zwitterion and coordinates toward the carboxy group as a formally neutral ligand. The possibility of formulating the complexes as H2[M(β-ala)2X2] is discussed. The electronic spectra and the magnetic moments of the halide complexes are in accord with pseudo-tetrahedral, octahedral, and tetragonal stereochemistry for the cobalt(II), nickel(II), and copper(II) ions, respectively, while those of the perchlorate complexes are in accord with pseudooctahedral stereochemistry. The β-alanine hydrohalide salts and the bis(β-alaninium)tetrachlorocuprate complex were also prepared and are discussed.