Copper(II)-oxime complexes: A structural and spectroscopic study for a diamine dioxime ligand

Abstract

The preparations are reported for copper(11) complexes with the ligand 4,4,9,9-tetramethyl-5,s-diazadodecane-2,l-dione dioxime, LH2. Syntheses from the syn (methyl) and anti isomers of the ligand give the same products. The complexes characterized are Cu(LH2)X2,yH2O (X = Cl-, ClO4-; y = 0, 1, 2) and Cu(LH)X (X = Cl-, Br-, ClO4-). The complex Cu(LH)Br is shown by X-ray structure analysis to contain dimeric units (Cu(LH))22+ with crystallographic C2 symmetry and with the copper atom in a trigonal bipyramidal coordination environment. Stability constants for the reactions Cu2+ + LH2 ←→ Cu(LH2)2+ (log K = 13.24 � 0.05) and Cu(LH2)2+ ←→ Cu(LH)+ + H+ (log K = -3.24 � 0.08) are reported, as well as the magnetic susceptibilities, i.r. spectra, and electronic absorption spectra of the complexes.

Computer simulation of nickel in blood-plasma following the in vitro investigations of complex formation chemistry with polyamine(amide) ligands

“…These pK M-NOH values indicate that the proton(s) are indeed lost from the terminal oxime groups rather than from axially bound water molecules. In fact, the loss of these protons is easier by approximately 8.3 and 2.8 log units compared to the free ligand (pK a ≈ 12.3) 17 indicating the involvement of the metal ion in this process.…”

“…6) around the small, diamagnetic Ni(II) ion. Electronic spectra of Cu 2+ complexes of 3,3,8,8-tetramethyl-4,7-diazadecane-2,9-dione dioxime (EnAO) 2 and 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11dione dioxime (H 2 tmdddo) 17 indicate that dissociation of an oxime proton causes an increase in the donor strength of the oxime nitrogen atom. There is no red shift in the d-d transition upon formation of [NiL 1 H −2 ] from [NiL 1 H −1 ].…”

“…The hydrogen bond is believed to play a less significant role in these nickel(II) species compared with copper(II)-oxime ligand complexes. 2,17 In fact, the NH-CH(CH 3 ) 2 CH(CH 3 )N-OH fragment in L 1 and NH-COCHN-OH moiety in L 2 can be viewed as electron sinks for metal ions such as Ni(II), which are capable of deprotonating the oxime and/or amide groups. In contrast to the above observations, nickel does not seem to deprotonate the amide nitrogens of L 3 .…”

Iron and cobalt complexes of 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione dioxime ligand: Synthesis, characterization and reactivity studies

“…17 The nickel(II) complexes have been shown to undergo a proton-assisted coupling of oxime with nitriles resulting in the iminoacylation of oxime H 2 L. The dioxime ligand forms complexes with other metal ions like iron(II), cobalt(II), and zinc(II) ions. [18][19][20] The flexible N4 ligand is expected to stabilize mononuclear complexes in the presence of a bidentate coligand. This * For correspondence would therefore find application in biomimetic chemistry for designing model complexes.…”

(4,4,12,12-Tetramethyl-5,8,11-triazapenta-2,14-dione 2-oxime 14-oximato-κ5N)copper(II) perchlorate: a copper(II) compound with a pentadentate triamine–oxime–oximate ligand

“…The structures of a number of copper(II) compounds with tetradentate diaza±oxime±oximate ligands with short OÐ HÁ Á ÁO hydrogen-bonded 14-to 16-membered pseudo-cyclic structures have been reported. These generally have squarepyramidal coordination, with water (Nunes et al, 1999;Anderson & Packard, 1979;Lee et al, 1990;Pal et al, 1986;Kiani et al, 2002) or an anion (Tahirov et al, 1993(Tahirov et al, , 1995Jiang et al, 1993;Nunes et al, 1999;Gavel & Schlemper, 1979;Lee et al, 1991;Liss et al, 1975;Schlemper et al, 1981) coordinated axially, or have dinuclear (Tahirov et al, 1993;Fraser et al, Acta Crystallographica Section C…”