No abstract

The synthesis and properties of two N-(2-pyridiny1)ketoacetamide ligands and their mono-and binuclear copper(i1) complexes are described. A crystal structure determination for one of the ligands, benzoyl-N-(2-pyridinyl)acetamide, HL2 (as its hydrochloride hydrate), shows that it belongs to the orthorhombic space group P212,21, with a = 16.224(9), b = 12.045(6), and c --= 7.41 5(4) A. The P-diketone moiety exists in the enol tautomeric form with unequal C-0 bond lengths [1.24(1) and 1.37(1) A] and other geometric features similar to those in related P-diketones. In solution the ligands display keto-enol tautomerism. Mononuclear copper(ii) complexes of type [CuL,] display spectral and magnetic properties typical of square-planar copper( ii) P-diketone chelates. In contrast, binuclear species of type [Cu,L,( CIO,),] display very strong antiferromagnetic coupling. The crystal structure of one example involving the N-(2-pyridinyl) -acetoace_tamide ligand, viz. [Cu,L' ,( CI0,),]-2H20, shows that it belongs to the triclinic space group P1, with a = 10.522( 6), b = 9.1 32@), c =-8:3$6-F) A, a = 102.38( 12), p = 121.86( 14), and y = 93.75( 10)'. The binucleating ligands, L', are disposed trans to each other in a planar arrangement about the two Cu atoms. The pyridine N and keto 0 atoms are co-ordinated to each Cu with the amide 0 acting as a bridging atom. The Cu-Cu distance [3.022(2) A] and Cu-0-Cu angle [102.0(2)"] can be correlated with the size of the exchange constant, W = -588 cm-', in a similar manner to the values for related p-alkoxo-copper( 11) complexes. The perchlorate groups are weakly co-ordinated to each Cu atom in a bridging bidentate manner.

Magnetostructural correlations are made on the matched pair of O‐bridged and S‐bridged binuclear Cu(II) complexes (Ia) and (Ib).

311ChemInform Abstract The first examples of binuclear Ni and Cu complexes (V) bonded to binucleating Schiff base ligands containing an endogenous alkanethiolato-bridging sulfur atom are synthesized as shown. The structure of (Va) is determined by an X-ray analysis (space group P21/c, Z=4). The Cu complex (Vb) represents one of the few known stable alkanethiolate species. Variable-temp. magnetic susceptibility measurements show weak antiferromagnetic exchange coupling.

ChemInform Abstract The title compounds (III) are prepared in a "one-pot" reaction. The failure of certain thionation methods in the preparation of (III) from the analogue N-(2-pyridyl)-ketoacetamide is demonstrated. The compounds (III) show analogous spectroscopic properties to the ketoacetamide derivative and display thioketo-enol tautomerism in solution but are readily oxidized to (IV). This redox activity is shown to be decreased at low temp. and eliminated in the N-benzylated derivatives (VI). The complexes (VIII), prepared in warm solution for M=Ni and Zn and ice-cooled for M=Cu, are characterized by IR, electronic, 1H and 13C NMR spectra.