STERIC INFLUENCES IN THE FORMATION OF COMPLEXES OF SCHIFF-BASE DERIVATIVES OF 2-ACETYLPYRROLE WITH CU(II)

A series of Cu(II) complexes of Schiff base derivatives of 2-acetylpyrrole with ammonia, n-butylamine and benzylamine have been synthesized, as well as the bis chelate complex of 2-acetylpyrrole with Cu(II). The stoichiometry of each complex is shown to depend on the amine used. Small amines (NH3 and CH3NH2) produce trans bis ketimine Cu(II) chelates, while ethylamine and the larger primary amines effect mixed ligand products containing one 2-acetylpyrrole chelate and one Schiff base chelate per metal center with pyrrole groups cis to one another. Cu(II) is shown to mediate Schiff base formation while also maintaining a square planar stereochemistry. Crystals of the trans bis Schiff base derivative of 2-acetylpyrrole with ammonia, Cu(C6H7N2)2 (1a), are monoclinic with space group P2(1)/n with a = 11.698(2), b = 5.406(l), c = 10.687(3) angstrom, beta = 115.92(1)-degrees, V = 607.8 angstrom3 and Z = 2. Crystals of the trans bis Schiff base adduct of 2-acetYlpyrrole with benZYlamine, CU(C13H13N2)2 (3b), are monoclinic with space group P2(1)/c with a = 10.647(3), b = 12.737(4), c = 16.371(3) angstrom, beta = 90.31(2)-degrees, V = 2220.1 angstrom3 and Z=4. Cu(C6H6NO)2 (4a), the bis Cu(II) chelate of 2-acetylpyrrole, is monoclinic with space group P2(1)/a with a = 8.143(2), b = 14.452(3), c = 5.189(l) angstrom, beta = 106.82(2)-degrees, V = 584.5 angstrom3 and Z = 2.