Oxime Oxygen Atoms Research Articles

Ab initio molecular dynamics study of the hydration of the formohydroxamate anion

We apply ab initio molecular dynamics (AIMD) to study the hydration structures and electronic properties of the formohydroxamate anion in liquid water. We consider the cis- nitrogen-deprotonated, cis- oxygen-deprotonated, and trans- oxygen-deprotonated formohydroxamate tautomers. They form an average of 6.3, 6.9, and 6.0 hydrogen bonds with water molecules, respectively. The predicted pair correlation functions and time dependence of the hydration numbers suggest that water is highly structured around the nominally negatively charged oxime oxygen in O-deprotonated tautomers but significantly less so around the nitrogen atom in the N-deprotonated species. Wannier function analysis suggests that, in the O-deprotonated anions, the negative charge is concentrated on the oxime oxygen, while in the N-deprotonated case, it is partially delocalized between the nitrogen and the adjoining oxime oxygen atom.

Ligands Containing of a C=O and an –Nh–R Adjacent to the Oxime Group and their Cobalt(Ii), Nickel(Ii) and Copper(Ii) Complexes

Ligands having a C=O group and an –NH–R group adjacent to the oxime group have been prepared from ω-chloroisonitrosoacetophenone and aniline or aniline derivatives in the presence of NaHCO3. The Ni(II), Cu(II) and Co(II) complexes of the synthesised ligands have been prepared and characterised. The ligands are proposed to coordinate to the metal ions via the oxime oxygen and amide nitrogen atoms. Thermal analyses data reveals that the water in the complexes is non-coordinated to the metal ions. Binuclear and polymeric structures are suggested for all complexes. The complexes showed an antiferromagnetic effect.

Experimental and theoretical vibrational spectroscopy studies of acetohydroxamic acid and desferrioxamine B in aqueous solution: Effects of pH and iron complexation

The deprotonation and iron complexation of the hydroxamate siderophore, desferrioxamine B (desB), and a model hydroxamate ligand, acetohydroxamic acid (aHa), were studied using infrared, resonance Raman and UV-vis spectroscopy. The experimental spectra were interpreted by a comparison with DFT calculated spectra of aHa (partly hydrated) and desB (reactive groups of unhydrated molecule) at the B3LYP/6-31G* level of theory. The ab initio models include three water molecules surrounding the deprotonation site of aHa to account for partial hydration. Experiments and calculations were also conducted in D 2O to verify spectral assignments. These studies of aHa suggest that the cis-keto-aHa is the dominant form, and its deprotonation occurs at the oxime oxygen atom in aqueous solutions. The stable form of iron-complexed aHa is identified as Fe(aHa) 3 for a wide range of pH conditions. The spectral information of aHa and an ab initio model of desB were used to interpret the chemical state of different functional groups in desB. Vibrational spectra of desB indicate that the oxime and amide carbonyl groups can be identified unambiguously. Vibrational spectral analysis of the oxime carbonyl after deprotonation and iron complexation of desB indicates that the conformational changes between anion and the iron-complexed anion are small. Enhanced electron delocalization in the oxime group of Fe-desB when compared to that of Fe(aHa) 3 may be responsible for higher stability constant of the former.

Synthesis and Characterization of Tetradentate N2O2 Schiff Base Ligands and Their Transition Metal Complexes

Two new ligands, 1,2‐propylimino‐bis(isonitroso‐2‐acetylnaphthalene) (H2L1) and 1,2‐ethyl‐imino‐bis(isonitroso‐2‐acetylnaphthalene) (H2L2), have been synthesized by the reaction of isonitroso‐2‐acetylnaphthalene with 1,2‐diaminopropane or 1,2‐diamino‐ethane. These ligands were reacted with nickel(II), copper(II), cobalt(II), zinc(II), cadmium(II) and mercury(II) ions to form complexes containing tetradentate Schiff bases. Each metal ion is in a four‐coordinate environment of two imine nitrogen atoms and two oxime oxygen atoms. The new compounds have been characterized by elemental analyses, magnetic susceptibility, mass, IR, 1H and 13C NMR spectroscopy.

Rhenium Chemistry of Azooximes: Oxygen Atom Transfer, Azoimine Chelation, and Imine−Oxime Contrast

The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex [ReV(O)Cl(PPh3)2(L1)](PF6), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site. Upon treatment of [ReV(NPh)Cl3(PPh3)2] with L1OH in solution, the neutral azoimine complex [ReV(NPh)Cl3(L1H)], 3, resulted due to the spontaneous transfer of the oxime oxygen atom to a PPh3 ligand, which is eliminated as OPPh3. In contrast, the oxime of 2-acetylpyridine (L2OH, 4) did not undergo oxygen atom transfer and simply afforded the imine-oxime complex [ReV(NC6H4Y)Cl2(PPh3)(L2O)], 5, upon reacting with [ReV(NC6H4Y)Cl3(PPh3)2] (Y = H, Me, Cl). The spectral and electrochemical properties of 2, 3, and 5 and the structures of three representative compounds are reported. In the cation of 2 (X = H) the two PPh3 ligands lie trans to each other and the equatorial plane is defined by the five-membered azoimine chelate ring and the oxo and chloro ligands. The oxo ligand which forms a model triple bond (Re-O length 1.616(6) A) lies cis to the imine-N atom. In 3 (X = Cl) the ReCl3 fragment has meridional geometry and the imido nitrogen lies trans to the imine nitrogen of the planar azoimine chelate ring. In 5 x H2O (Y = Me), the Cl, oximato-N, and P atoms define an equatorial plane and the pyridine-N lies trans to the imido-N. The water of crystallization is hydrogen bonded to the oximato oxygen atom (O...O, 2.829(5) A). Reaction models in which chelation of the azooxime precedes oxygen atom transfer are proposed on the basis of oxophilicity of trivalent rhenium, Lewis acid activity of pentavalent rhenium, electron withdrawal by the azo group, and observed relative disposition of ligands in products.

Intramolecular and intermolecular OHO hydrogen bond in some nickel(II) complexes with tridentate amino–oxime ligands

The 3-[(2-pyridyl)methylamino]-butan-2-one oxime (H-LNH-py) tridentate ligand forms with Ni(II) the pseudo-octahedral complex [Ni(II)(H-LNH-py)(LNH-py)]ClO 4 where the coordination of two ligands to the metal atom leads to the formation of an equatorial chelating system containing an intramolecular hydrogen bond (OHO) involving the oxime oxygen atoms. In acidic medium the [Ni(II)(H-LNH-py) 2](ClO 4) 2, complex is formed, deriving of the precedent by addition of a proton to the OHO bridge. A third complex, [Ni(II)(H-LNH-py) 2(C 6H 2N 3O 7)](C 6H 2N 3O 7), was isolated, as picrate, containing a double intermolecular hydrogen bond with a picrate ion. X-ray analysis of these compounds allows defining in all three cases the geometry of the hydrogen bonding fragments.

Preparation and Photochemistry of Some Cobalt(III) Complexes of Tridentate Oxime-Diamine and Oxime-Amino Acid Ligands

Cobalt(III) complexes of tridentate ligands containing oxime-diamine and oxime-amino acid donor sets have been prepared, both by reduction of the related imine complexes. Many of the complexes have been characterized by X-ray crystallographic techniques. The photochemistry of these complexes has been studied. The oxime-diamine systems are rather unreactive, undergoing slow isomerization before decomposition. The oxime-amino acid systems appear to undergo decarboxylation reactions. Photolyses of tetrachlorozincate salts of some of the complexes result in binuclear species in which a trichlorozinc moiety is bound to the cobalt species through an oxime oxygen atom.

Study of complex formation with 2-hydroxyiminocarboxylates: specific metal binding ability of 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid

Complex formation properties of a novel water soluble thiazolyloxime 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (H 3L 1) with Cu 2+ and Ni 2+ were investigated in solution by potentiometrical and spectral (UV–Vis, EPR, NMR) methods. All Cu 2+ and most of Ni 2+ complex species detected in solution were found to have square-planar MN 4 core with oxime and heterocyclic nitrogen atoms which was rationalized in terms of destabilizing effect of repulsive interaction between oxygen atom of carboxylic group and nitrogen atom of thiazole ring in N, O-coordinated ligand conformation. It has been found that stability of metal complexes in a series of oxime ligands is dependent upon basicity of nitrogen atom of oxime group. The thiazolyloxime forms less stable complexes with Cu 2+ but stronger ones with Ni 2+ ions when compared to parent 2-(hydroxyimino)propanoic acid. The lower stability obtained for Cu 2+ complexes was elucidated in terms of negative inductive effect of the thiazole and nitrile substituents as well as an effect of intramolecular attractive interaction between thiazolyl sulfur and oxime oxygen atoms in thiazolyloxime. In the case of Ni 2+ the complexes formed are square-planar and it is why thiazolyl ligand is more effective in metal ion binding than simple 2-(hydroxyimino)propanoic acid forming only octahedral species. The solid state structure of the Co 3+ complex K 3[Co(HL 1) 3]·5.5H 2O ( 1) was studied by X-ray analysis. The thiazolyloxime ligand is coordinated to Co 3+ via oxime nitrogen and carboxylate oxygen atoms forming five-membered chelate rings.

Synthesis and Structure of Tetra- and Triarylantimony Oximates

Reactions of pentaphenyl- and penta-p-tolylantimony with benzophenone oxime or triarylantimony bis(benzophenone oximate) yield tetraarylantimony benzophenone oximates. Triarylantimony bis(benzophenone oximates) were prepared by oxidative addition from triarylstibine and benzophenone oxime in the presence of hydrogen peroxide. X-ray diffraction analysis was performed to show that benzophenone oxime is a dimer and tetraphenylantimony benzophenone oximate has a trigonal bipyramidal antimony atom and an axial oxime oxygen atom.

Crystal structures of nitridotechnetium(V) complexes of amine oximes differing in carbon chain lengths

Structures of nitridotechnetium(V) amine oxime complexes, [TcN(pnao)(H2O)][BPh4] 1, [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3 [Hpnao = HONCMeCMe2NH(CH2)3NHCMe2CMeNOH; Hbnao = HONCMeCMe2NH(CH2)4NHCMe2CMeNOH; Hpentao = HONCMeCMe2NH(CH2)5NHCMe2CMeNOH], differing in carbon chain length of the amine oxime ligands, were characterized by X-ray crystallography. These complexes are six-co-ordinated and distorted octahedral. Four nitrogen atoms of the amine oxime ligands are in the equatorial plane and both the nitrido and H2O ligands in the apical positions. These complexes have an asymmetrical intramolecular hydrogen bond between the two oxime oxygen atoms. Their intramolecular O· · ·O distances are 2.720 A in 1, 2.512 A in 2 and 2.531 A in 3. The longest O· · ·O distance in 1 is ascribed to a steric effect of the carbon chain length between the amine nitrogens. Namely, the shorter carbon chain of the pnao ligand causes strain on the co-ordinated pnao moiety, and the O· · ·O distance in 1 is longer than that in 2 and 3 with longer carbon chains.

Stabilization of Copper(III) Ions with Deprotonated Hydroxyiminoamide Ligands: Syntheses, Structures, and Electronic Properties of Copper(II) and Copper(III) Complexes

Copper(II) and copper(III) complexes were prepared with two novel ligands, N,N′-bis(2-(1-hydroxyimino-2-methyl-1-phenyl)propyl)dimethylmalondiamide (H4mal55) and N,N′ bis(-(1-hydroxyiminoethyl)phenyl)dimethylmalondiamide (H4mal66), both of which contain two amide and two oxime functionalities as potential ligand donor groups. The two copper(II) complexes (NEt4)[Cu(Hmal55)] (1) and (NEt4)[Cu(Hmal66)] (2) can be reversibly oxidized in acetonitrile at a redox potential of –0.120 and –0.075 V vs. the Fc/Fc+ redox couple, respectively. While the quantitative electrolysis of 1 results in the preparation of the oxidized complex [Cu(Hmal55)] (3), which is sufficiently stable to be isolated, isolation of the oxidation product of 2 was not attempted because of its long-term instability. The properties of the complexes were investigated by means of various spectroscopic methods (UV-vis, ESR, NMR, and IR spectroscopy) and by X-ray structure analysis. The structure determinations and the spectroscopic investigations of the complexes reveal a square-planar CuN4coordination environment for each complex in the solid state and in acetonitrile solution. In both the oxidized and reduced oxidation states of the complexes, the coordinated ligands remain triply deprotonated with a hydrogen atom bridging both oxime oxygen atoms. The ligands can therefore be regarded as pseudo-macrocyclic. The characterization of the oxidation products clearly identifies the electron-transfer reaction as being metal-centered. For the first time, the structure of a copper(III) complex with a ligand containing oximes as donor groups was determined. The redox potentials of the copper complexes are compared to related CuIII/CuII redox couples.

Reaction of ketoximes with aliphatic aldehydes and diphenylborinic acid. Crystal and molecular structure of a diphenylboron chelate derived from the pivaldehyde adduct to cyclohexanone oxime

Various ketoximes have been reacted with aliphatic aldehydes in the presence of oxybis(diphenylborane) in order to assess the influence of increasingly bulky residues on the nature of the products. Crystals of 5-tert-butyl-2-cyclohexylidene-3,3-diphenyl-1,4-dioxa-2-azonia-3-boratacyclopentane, 4c, are monoclinic, a = 14.0647(9), b = 11.416(1), c = 14.756(1) Å, β = 115.696(4)°, Z = 4, space group P21/c. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R = 0.038 (Rw = 0.038) for 2511 reflections with I >= 3σ(I). A bulky substituent at the aldehyde favors α-hydroxyalkylation at the oxime oxygen atom and subsequently leads to the formation of BOCON diphenylboron chelates, whereas formaldehyde reacts by N-alkylation of the oximes, resulting in COBON diphenylboron chelates.Key words: ketoximes, organoboron compounds, crystal structure.

Synthesis and characterization of two novel monooxovanadium(V) complexes with bidentate benzohydroxamate ligand

Two novel monooxovanadium(V) complexes [VOL1(bz)] (1) (H2L1 = N-salicylidenegglycine. Hbz = benzohydroxamic acid) and [VOL2(bz)]*(CH3OH) (2) (H2L2 = N-car☐yphenyl)salicylidenamine), were prepared and characterized by IR, Raman, UV,1H NMR spectra, cyclic voltammetry measurements and X-ray diffraction. The vanadium atoms in the two title complexes have a distorted octahedral geometry with VO(ONO)(OO) type coordination. The equatorial plane is defined by the O, N, O atoms of the tridentate ligand and the oxime oxygen atom of the benzohydroxamate ligand. The oxo group is trans to the carbonyl oxygen atom of the hydroxamate ligand, but not to the oxime oxygen atom of the same ligand. The two title complexes represent the first structural characterization of a vanadium hydroxamate complex with VO(ONO)(OO) coordination.

Syntheses and characterization of four novel monooxovanadium(v) hydrazone complexes with hydroxamate or alkoxide ligand

Four novel monooxovanadium(V) hydrazone complexes, [VOL 1(Hshi)] (1), [VOL 1(bz)] (2), [VOL 2(bz)]·CH 2Cl 2 (3), and [VOL 2(OCH 3)(CH 3OH)]·CH 3OH (4) (H 2L 1=salicylaldehyde benzoylhydrazone, H 2L 2=o-vanillin benzoylhydrazone, H 2shi=salicylhydroxamic acid, Hbz=benzohydroxamic acid), were prepared and characterized by IR, Raman, UV, 1H NMR spectra, cyclic voltammetry measurements and X-ray diffraction. The geometry around the vanadium atoms is a distorted VO(ONO)(OO) octahedron in complexes 1, 2 and 3, while the geometry is a distorted VO(ONO)(O)(O) octahedron in 4. The VO bond distance is 1.574(4), 1.593(5), 1.594(4) and 1.577(4) Å for complexes 1, 2, 3 and 4, respectively. In complexes 1, 2 and 3, the O, N, O atoms of a tridentate hydrazone ligand and one oxime oxygen atom of a bidentate hydroxamate ligand are coordinated to the vanadium(V) atom, forming an equatorial plane. In complexes 1, 2 and 3, the axial position trans to the oxo group is occupied by the carbonyl oxygen atom of the hydroxamate ligand, but not by the oxime oxygen atom. The bond distances in the equatorial plane in the title complexes follow the order: alkoxide oxygen<phenoxide oxygen, oxime oxygen<enolic oxygen<imine nitrogen. The complexes 1, 2 and 3 represent the first structural examples of vanadium complexes containing both hydrazone and hydroxamate ligands.

Co-ordination ability of novel tetradentate amide-and-oxime ligands: differential binding to CuII and NiII

Four cationic and anionic complexes of NiII and CuII with new open chain oxime-and-amide ligands, N,N′-bis(2-hydroxyiminopropionyl)-1,2-diaminoethane (H2pen) and 1,4-diaminobutane (H2pab) were isolated and characterised by X-ray crystallography and a variety of spectroscopic techniques. The ligands were found to exhibit two types of co-ordination modes depending on pH: N(oxime),O(amide) bis-bidentate and N2(oxime),N2(amide) tetradentate. The first bonding mode leads to bridging of the two ligands thus forming binuclear cationic complexes [{Cu(Hpab)(ClO4)·2H2O}2] 1b and Li[Ni(H–1pen)]·4H2O 2a which have been determined by single-crystal X-ray analysis. In 1b the bis-bidentate co-ordination mode leads to the formation of a dimeric complex cation containing a loose 22-membered macrocyclic cavity incorporating two CuII ions as a part of the ring skeleton. The central atoms in 1b are distorted square-pyramidal with the water molecule in the apical position. N4-tetradentate co-ordination observed in 2a leads to the formation of a square-planar complex anion with a closed pseudo-macrocyclic environment stabilised by a short intramolecular H-bond between the oxime oxygen atoms.

Bridging ability of a novel polydentate ligand (H2L) comprising an oxime function. Structures of a mononuclear precursor [NiL] and a dinuclear CuII2 complex. Magnetic properties of mononuclear (NiII and CuII), dinuclear (CuII2, NiII2, NiIICuII and CuIICrIII) and trinuclear (CuII3, CuIIMnIICuII and CuIIZnIICuII) complexes ‡

A novel non-symmetrical polydentate Schiff base ligand 3-({2-[(1-methyl-3-oxobut-1-enyl)amino]ethyl}imino)butan-2-one oxime (H2L) comprising an oxime function among various donor sites yields neutral [NiIIL] and [CuIIL] complexes. The structural determination of [NiL] confirms the deprotonation of the oxime function. The deprotonated oxime oxygen atom can react with auxiliary complexes to give homo- and hetero-di- and tri-nuclear entities. The structural determination of a homodinuclear copper complex clearly shows the presence of the expected oxime bridge, along with an unexpected ketonic bridge between the two copper centres leading to a Cu[O,NO]Cu core. A moderate antiferromagnetic interaction is present in the di- and tri-nuclear copper complexes. A similar interaction is also observed in the heteronuclear complexes (CuIINiII and CuIIMnII) and, more surprisingly, in the heterodinuclear CuIICrIII entity. A generalization of the Cu[O,NO]Cu structure leads to a justification of these magnetic properties.

Structural studies on copper(II) complex containing (Z)-2-(2-Aminothiazol-4-yl)- N-(2-hydroxyethyl)-2-(hydroxyimino) acetamide, A model compound for a cephalosporin antibiotic cefdinir

(Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for an orally active cephalosporin antibiotic, Cefdinir (CFDN). A binuclear copper(II) complex Cu 2L 4 (1) has been obtained from an aqueous solution containing CuCl 2 and HL, and its structure determined by means of X-ray crystallography: monoclinic, P2/c, a = 11.954(3) A ̊ , b = 10.661(3) A ̊ , c = 16.969(7) A ̊ , β = 108.13(3)°, Z = 2 . The molecular structure of 1 is a dimeric copper(II) complex consisting of two copper(II) complex units CuL 2, where the two molecules of L (L a and L b) are coordinated to the copper atom through their thiazole and oximate nitrogen atoms. L a is also coordinated to the copper atom of the other CuL 2 unit through the oximate oxygen atom, namely, the two complex units are bound to each other by forming a pair of oximate NO bridges of the two L a molecules. The coordination environment of the copper atom is a distorted trigonal bipyramid. In addition, based on the molecular structure, the coordination property of CFDN to copper(II) in water has been clarified by means of spectrophotometry and titration. Both copper(II) (0.05 mM)-HL (0.1 mM) and copper(II) (0.05 mM)-CFDN (0.1 mM) aqueous solutions gave broad d-d bands at ca. 720 nm above pH 6, corresponding to that observed in the diffuse reflectance spectrum of the crystals of 1. The results indicate that CFDN also forms a binuclear copper(II) complex, Cu 2(CFDN) 4, corresponding to Cu 2L 4 as the main species in water above pH 7. Stability constants are as follows: log β 110 = 11.12, log β 240 = 41.13 for copper(II)-L complexes. The theoretical species distribution diagram as a function of pH for the copper(II) (0.05 mM)-HL (0.1 mM) system shows that Cu 2L 4 exists as the main species above pH 7. The titration results are consistent with the spectral data. The spectral and titration studies indicate that not only HL, but also CFDN forms a binuclear complex Cu 2(CFDN) 4 corresponding to Cu 2L 4 as the main species under the neutral and basic conditions. In addition, the stability constants of CFDN complexes should be as large as those of CuL complexes, although titrations for copper(II)-CFDN systems could not be carried out due to precipitation of copper(II)-CFDN complexes.

Co-ordination of copper(II) and nickel(II) ions by a novel open chain oxime ligand

Potentiometric spectroscopic and X-ray studies of the open chain oxime ligand, N,N′-bis(2-hydroxyimino-propionyl)propane-1,3-diamine and its complexes with NiII and CuII ions showed a very high efficacy of the ligand studied in the co-ordination of both CuII and NiII ions. The metal complexes are very stable and square-planar with four nitrogens involved in metal-ion binding. These complexes may be additionally stabilised by hydrogen bonds between two oxime oxygen atoms.

Structural studies on an iron(III) complex containing (Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide, a model compound for a cephalosporin antibiotic Cefdinir

(Z)-2-(2-Aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for a cephalosporin antibiotic, Cefdinir. A trinuclear iron(III) complex [Fe3L6]Cl[OH]21 has been obtained from a methanol solution containing HL and FeCl3 and its structure determined by X-ray crystallography: monoclinic, space group P21/n, a= 15.559(1), b= 19.295(2), c= 10.963(1)Å, β= 101.29(1)°, Z= 2. The molecular structure contains a linear Fe(1)–Fe(2)–Fe(1′) arrangement, the central atom Fe(2) being an inversion centre. Atom Fe(1) is co-ordinated to three molecules of L through the thiazole and oximate nitrogen atoms to form Fe(1)L3, and Fe(2) to six oximate oxygen atoms of the two Fe(1)L3 units. The two Fe(1)L3 units are bridged by the central iron atom Fe(2). The Mössbauer spectrum of 1 gave an apparent doublet signal consisting of two doublets, A and B, assigned to Fe(1) and Fe(2), respectively. The isomer shifts δ of these doublets are the same (0.26 mm s–1), and are typical for high-spin iron(III). In addition, the reflectance spectrum did not show any intervalence bands. These spectral data indicate that the three iron atoms are high-spin iron(III). The compound co-ordinates to iron(III)via the thiazole ring nitrogen atom and the oximate nitrogen atom (2N mode) in methanol which is different from that in water, where L prefers to co-ordinate to an iron(III) through the oximate oxygen atom and the amide oxygen atom (2O mode).

Synthesis and crystal structure of a copper(II) complex with a tetradentate dithiadioxime ligand

A neutral five-coordinate dithiadioxime complex of copper(II), chloro[3,3′-(1,3-propanedithia)bis(3-methyl-2-butanone oximato)(1-)- S, S′, N, N′]copper( II) (Cu(LH)Cl), was prepared by reaction of CuCl 2 with the [3,3′-(1,3-propanedithia)bis(3-methyl-2-butanone oxime)] ligand (LH 2) in methanol-acetone. The crystal structure of the Cu(LH)Cl monohydrate, [CuCl(C 13H 25N 2S 2O 2)]·H 2O, reveals a square pyramidal geometry about the metal centre. The copper(II) ion is coordinated in an approximate square plane by the two oxime nitrogen atoms and two thioether sulphur atoms of the tetradentate dithiadioxime ligand, with the chlorine occupying an axial coordination site at a CuCl distance of 2.3931(8) Å. The copper-to-nitrogen distances average 1.997 Å, while the copper-to-sulphur distances average 2.3279 Å. The least-squares S 2N 2 plane is situated 0.467(1) Å below the copper centre. A proton bridges the two oxime oxygen atoms of the complex in the fashion typical of metal complexes containing cis-oxime functions.