Structural, spectroscopic, and magnetic properties of mono- and bi-nuclear copper(II) complexes of N-(2-pyridinyl)ketoacetamides

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.

Syntheses, Structures, and Magnetic Properties of Copper(II) Complexes with 1,3‐[Bis(2‐pyridylmethyl)amino]benzene (1,3‐tpbd) as Ligand

“…[55] Furthermore, from the X-ray structure data of 4 the intermolecular exchange interaction can be excluded: the shortest intermolecular copperϪcopper distance is 8.67 Å , with no ligand present which could provide a possible exchange pathway. Consequently, the exchange pathway involved in the ferromagnetic coupling observed in 4 is operating through the meta-phenylenediamine bridge.…”

2-Acetyl-3′-chloroacetanilide

“…The title compound was prepared by a method similar to that of Lliopoulos et al (1986). A solution of 3-chloroaniline (10 mmol) in benzene (30 ml) was added to a solution of ethyl acetoacetate (10 mmol) and the reaction mixture was re¯uxed for 2 h with stirring.…”

N-(3,4-Dichlorophenyl)-3-oxobutanamide

“…For the synthesis and biological activity of the title compound, see: Lliopoulos et al (1986); Grissar et al (1982). For related structures, see: Whitaker (1986Whitaker ( , 1987Whitaker ( , 1988; Whitaker & Walker (1987); Brown & Yadav (1984); Tai et al (2005); Sundar et al (2005); Guo (2004); Robin et al (2002).…”