SYA 013 analogs as moderately selective sigma-2 (σ2) ligands: Structure-affinity relationship studies

Several lines of evidence suggest that selective sigma-2 (σ₂) ligands might be useful for the treatment of solid tumors. However, very few selective σ₂ ligands have been identified. This study was aimed at identifying new selective σ₂ receptor ligands using a previously identified agent, SYA 013 as a lead. Four groups, homopiperazine, piperazine, tropane and selected oxime analogs of the homopiperazines were identified, synthesized and subsequently screened at the σ₁ and σ₂ receptors. The results demonstrate that these scaffolds can be modified to obtain selective σ₂ receptor ligands. 1-(5-Chloropyridin-2-yl)-4-(3-((4-fluorophenyl)thio)propyl)-1,4-diazepane, 7 and 3-(4-chlorophenyl)-8-(3-((2-fluorophenyl)thio)propyl)-8-azabicyclo[3.2.1]octan-3-ol, 21 were identified as the highest binding affinity ligands (σ₂Ki = 2.2 nM) and (4-(4-(5-chloropyridin-2-yl)-1,4-diazepan-1-yl)-1-(4-fluorophenyl)-butan-1-one oxime, 22 as a high affinity and the most selective ligand for the σ₂ receptor (σ₁Ki/σ₂Ki = 41.8).     

Ruthenium(II) thiacrown complexes: Synthetic, spectroscopic, electrochemical, DFT, and single crystal X-ray structural studies of [Ru([15]aneS5)Cl](PF6)

We wish to report the synthesis of the Ru(II) crown thioether complex, (1,4,7,10,13-pentathiacyclopentadecane)chlororuthenium(II) hexafluorophosphate, [Ru([15]aneS₅)Cl](PF₆), and a study of its properties utilizing single crystal X-ray diffraction, electronic spectroscopy, NMR spectroscopy, density functional theory calculations and cyclic voltammetry. The crystal structure shows a single [15]aneS₅ macrocycle and a chloro ligand coordinated in a distorted octahedral fashion around the ruthenium(II) center. A significant shortening (0.15 Å) of the trans Ru-S bond length occurs in this complex compared to the related PPh₃ complex (2.4458(10) to 2.283(1) Å) due to the differences in the trans influence of the two ligands. ¹³C NMR spectroscopy demonstrates that the structure of [Ru([15]aneS₅)Cl]⁺ is retained in solution. As expected for a Ru(II) complex, the electronic absorption spectrum shows two d-d transitions at 402 and 331 nm. These are red-shifted compared to hexakis(thioether)ruthenium(II) complexes and consistent with the weaker ligand field effect of the chloro ligand. The electrochemical behavior of the complex in acetonitrile shows a single one-electron reversible oxidation-reduction at +0.722 V versus Fc/Fc⁺ which is assigned as the Ru(II)/Ru(III) couple. DFT calculations for [Ru([15]aneS₅)Cl]⁺ show a HOMO with orbital contributions from a t_2g type orbital of the Ru ion, a π component from a p orbital of the axial S atom of [15]aneS₅, and a p orbital of the chloro ligand while the LUMO consists of orbital contributions of d_x²-y² orbital of the Ru center and p orbitals of the four equatorial S donors.     

A novel trinuclear nickel(II) complex of an unsymmetrical tetradentate ligand involving bridging oxime and acetylacetone functions

A novel trinuclear nickel(II) complex, [Ni₃(L)₂(H₂O)₂](ClO₄)₂, where L is a bridging unsymmetrical tetradentate ligand, involving o-phenylenediamine, diacetyl monoxime and acetylacetone (H₂L = 4-[2-(3-hydroxy-1-methyl-but-2-enylideneamino)-phenylimino]-pentan-2-one oxime) has been synthesized and characterized structurally. In the complex, an octahedral Ni(II) centre is held in the middle by two square planar units with the aid of oxime and ketonic bridges.     

The formation and isolation of benzisothiazole rings from the reactions of oxime-thiophenolate ligands

The reaction of [Ni(eftp)] [eftp = N,N-ethylene(6-formyl-4-methyliminatothiophenolato)] with hydroxylamine hydrochloride in the presence of potassium acetate in MeOH resulted in the formation of [Ni(L)₂], L = 2-mercapto-5-methyl-3-({2-[(5-methyl-benzo[d]isothiazol-7-ylmethylene)-amino]-ethylimino}-methyl)-benzonitrile. A single-crystal X-ray diffraction structural determination showed that the oxime groups of the proposed new binucleating ligand had reacted to produce a nitrile and an isothiazole ring, while two ligand molecules combined with one Ni(II) ion to form a new complex with a cis-S₂N₂ square-planar geometry. Also, the reaction of 2,6-diformyl-4-methylphenyl disulfide with hydroxylamine in MeCN resulted in the synthesis of 5-methyl-2-oxy-benzo[d]isothiazole-7-carbaldehyde oxime, where an isothiazole ring had formed via the cleavage of the disulfide bond. Again, a single-crystal X-ray diffraction study confirmed the presence of a benzisothiazole product.     

Synthesis, characterisation and crystal structure of hydroxylamido-κN,O(iodo)[tris(3,5-dimethylpyrazol-1-yl)borato]nitrosylmolybdenum(II)

The unusual 18e seven-coordinate Mo(II) complex [Mo(NO)(H₂NO-κ²N,O)(Tp^Me2)I] (1; [Tp^Me2]⁻ is hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been synthesised and characterised by IR, ¹H NMR and ESI-MS spectroscopies and by a single crystal X-ray diffraction study. The complex has a distorted pentagonal bipyramid structure with equatorial κ²-NH₂O⁻ ligand (d_N-O = 1.387 Å, d_Mo-N and d_Mo-O equal 2.049 and 2.092 Å, respectively). In the solid state 1 exists as a dimer (the point group C_i) due to the formation of two NH?O hydrogen bonds (d_N-H?O = 2.064 Å) between the adjacent NH₂O⁻ ligands, whilst in solution at/or above RT it resolves itself giving a monomer, which readily isomerises to more thermodynamically stable diastereoisomer.     

A two-dimensional copper(II) polymer with bridging μ-trans-oxamidate and μ2-picrate ligands: Synthesis, crystal structure and DNA binding studies

A two-dimensional copper(II) polymer with formula of [Cu₂(dmapox)(pic)₂]_n · nCH₃OH, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide and pic is picrate, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectra studies. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P2₁/c with crystallographic data: a = 14.076(7) Å, b = 13.896(7) Å, c = 9.278(5) Å, β = 106.909(6)° and Z = 2. The structure consists of uncoordinated methanol molecules and two-dimensional copper(II) polymeric coordination network constructed by the bis-tridentate trans-dmapox and tridentate picrate ligands. The environment around the copper(II) atom can be described as a distorted octahedron and the Cu?Cu separations through μ-trans-oxamidate and μ₂-picrate bridges are 5.227 Å and 8.359 Å, respectively. The copper(II) complex presents as a polymer in solid state, whereas in solution it presents as discrete neutral binuclear copper(II) species [Cu₂(dmapox)(pic)₂] due to the weak interactions between the copper(II) atoms and the para-nitro oxygens of the adjacent picrate ligands. The fluorescence titration and the ethidium bromide (EB) fluorescence displacement experiments reveal that the binding mode between the binuclear copper(II) complex [Cu₂(dmapox)(pic)₂] and Herring Sperm DNA might be intercalation.     

Novel triorganotin(IV) complexes of β-diketonates bearing two heterocycles in their structures

Novel triorganotin(IV) derivatives of β-diketonate Q ligands (HQ in general, in detail HQ^fur = 1-phenyl-3-methyl-4-(2-furancarbonyl)-pyrazol-5-one, HQ^thi = 1-phenyl-3-methyl-4-(2-thienylcarbonyl)-pyrazol-5-one) of general formula (Q)SnR₃·xH₂O (R = Ph, x = 0; R = Buⁿ or Me, x = 1) have been synthesized and spectroscopically and thermally characterized. Triphenyltin(IV) complexes have been isolated as anhydrous compounds while trialkyltin(IV) are always monohydrated. The structures of (Q^fur)SnPh₃ and (Q^thi)SnMe₃(OH₂) are recorded. The tin atoms are five-coordinate in both. In the first, the pyrazolonate ligand behaves as an O,O′-bidentate; there are two similar but independent molecules in the structure. In the quasi-trigonal-bipyramidal environments, Sn-O(acyl) are 2.478(3), 2.364(3), Sn-O(pyrazolonate) 2.050(2), 2.079(2), Sn-C 2.123(4)-2.162(3) Å with the longer O(acyl) and a phenyl group quasi-trans (O-Sn-C 162.5(1), 160.8(1)°). In (Q^thi)SnMe₃(OH₂), the three methyl groups are equatorial (Sn-C 2.1259(9)-2.1380(8) Å); Sn-O(Q^thi,OH₂) are 2.2143(5), 2.3350(6) Å, O-Sn-O 175.36(2)°. Trimethyltin(IV) derivatives decompose on heating with release of H₂O and SnMe₄ and formation of (Q)₂SnMe₂. Decomposition occurs also within two days after dissolution of (Q)SnMe₃(OH₂) in chloroform.     

Synthesis and characterization of an N-coordinated amidate copper(II) complex of deprotonated N-(2,6-diisopropylphenyl)-2-(bis-(2-pyridylmethyl))aminoethanamide

The title ligand, N-(2,6-diisopropylphenyl)-2-(bis-(2-pyridylmethyl))aminoethanamide (DIPMAE-H), was prepared by a nucleophilic substitution reaction between N-(2,6-diisopropyl)phenyl-2-bromoethanamide and bis-(2-pyridylmethyl)amine. An analogous ligand (TBPMAE-H) in which the 2,6-diisopropylphenyl group was substituted for a tert-butyl group was also prepared in this manner. Then, [(DIPMAE-H)CuBr]⁺Br⁻ and [(TBPMAE-H)CuBr]⁺Br⁻ were prepared by heating one equivalent of ligand and CuBr₂ in CH₃CN. In both compounds the geometry about the copper center is square pyramidal with distortions due to the geometrical constraints of the ligand. The amide oxygen occupies the axial position, and the three amine nitrogens and the bromide ligand form the basal plane of the square pyramid. Pairs of complexes in the unit cell are associated via weak donation of a lone pair on the bromide ligand of one complex to the copper center of another (Cu?Br distances in the range of 3.3576-3.4022 Å).The title compound, (DIPMAE)CuBr, was prepared by deprotonation of [(DIPMAE-H)CuBr]⁺Br⁻ using NaH. The key feature of (DIPMAE)CuBr is the amidate group η¹- and N-coordinated to the copper center. The compound also exhibits distorted trigonal bipyramidal coordination geometry with the bromide and tertiary amine donors occupying the axial sites and the amidate and pyridyl donors occupying the equatorial positions. The copper atom is displaced from the trigonal plane towards the bromide donor apex due to the geometrical demands of the ligand.     

Encapsulated two distinct infinite helical water chains in a cyano-bridged copper-iron heterometal complex

A bimetallic oligonuclear complex, [trans-{Cu(pmea)₂Fe(CN)₆]·9H₂O (1) (pmea = bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine), had been synthesized and structurally characterized. 1 crystallizes in monoclinic space group P2(1)/c with a = 23.924(5) Å, b = 10.911(2) Å, c = 21.094(4) Å, β = 112.46(3)° and Z = 4, which exhibits a three dimensional (3D) framework constructed from the water rich 2D sheets. Of particular interest, two kinds of helical water chains coexist in this complex. Comparing the experimental results, it is comprehensible that hosts constructed from the hexacyanometallates plays crucial roles in the formation of the helical structures and water aggregates. Additionally, the compound was characterized by TGA, IR spectroscopy, magnetism and elemental analysis.     

Synthesis, characterization, electrochemical and spectroscopic investigation of cobalt(III) Schiff base complexes with axial amine ligands: The layered crystal structure of [Co(salophen)(4-picoline)2]ClO4 · CH2Cl2

Cobalt(III) complexes with potentially tetradentate salophen (H₂salophen = N,N′-bis(salicylidene)-1,2-phenylenediamine) as equatorial ligand and with different axial amine ligands (NH₃, cyclohexylamine, aniline, 4-picoline and pyridine) were synthesized and characterized by IR, ¹H NMR, elemental analysis. Electronic spectra and electrochemical properties of the complexes were studied in DMF solutions. The lowest energy transitions, which occur between 464.8 and 477 nm, are attributed mainly to the intraligand charge transfer, confirmed by Zindo/S electronic structure calculations. The reduction potentials of Co(III)/Co(II) are more affected than those of Co(II)/Co(I) by the axial amine ligands. The crystal structure of the [Co^III(salophen)(4- picoline)₂]ClO₄ · CH₂Cl₂ was determined, indicating that the cobalt(III) center is six coordinated surrounded by the tetradentate salophen ligand and two 4-picoline ligands. The crystal packing of the complex shows a layered structure, in which the perchlorate counter ions and also the lattice solvent molecules are intercalated between the bc planes of the complex cations.     

The synthesis and characterization of a cationic technetium nitrosyl complex: The X-ray crystal structure of [TcCl(NO)(DPPE)2](PF6) · CH2Cl2

The reaction of the ammonium pertechnetate with a stochiometric excess of hydroxylamine hydrochloride in methanol yields a nitrosyl containing intermediate which can subsequently be reacted with reducing ligands to form nitrosyl complexes in various oxidation states. The reaction with a sixfold excess of diphenyl-phosphinoethane (DPPE) yields the Tc(I) cation [TcCl(NO)(DPPE)₂]⁺ which can be precipitated cleanly with tetraphenylborate. The infrared spectrum displays an absorption at 1728 cm⁻¹ which corresponds to the nitrosyl group. The ESI(+) mass spectrum displays the parent ion [TcCl(NO)(DPPE)₂]⁺ as the only signal at 960 m/z.The X-ray crystal structure of the hexafluorophosphate salt shows a mutually trans arrangement of the nitrosyl and chloride ligands with the two bidentate phosphine ligands coordinated in the equatorial plane. The nitrosyl and chloride ligands display the usual site disorder which makes discussion of bond lengths tenuous. However, the Tc-N-O bond angle of 179.0(2)° reflects the sp hybridization of the nitrosyl nitrogen atom. The Tc-P bonds are somewhat elongated at 2.3810(6), 2.3947(6), 2.4096(5) and 2.4321(6) Å, due to the steric congestion around the metal ion. The Tc-Cl bond is unexceptional at 2.3262(7) Å. The coordination geometry of this complex is best described as a distorted octahedron.     

Novel [Ru(polypyridine)(CO)2Cl2] and [Ru(polypyridine)2(CO)Cl]-type complexes: Characterizing the effects of introducing azopyridyl ligands by electrochemical, spectroscopic and crystallographic measurements

The reaction of ruthenium carbonyl polymer ([Ru(CO)₂Cl₂]_n) with azopyridyl compounds (2,2′-azobispyridine; apy or 2-phenylazopyridine; pap) generated new complexes, [Ru(azo)(CO)₂Cl₂] (azo = apy, pap). [Ru(apy)(CO)₂Cl₂] underwent photodecarbonylation to give a chloro-bridged dimer complex, whereas the corresponding pap complex ([Ru(pap)(CO)₂Cl₂]) was not converted to a dimer. The reactions of the chloro-bridged dimer containing the bpy ligand (bpy = 2,2′-bipyridine) with either apy or pap resulted in the formation of mixed polypyridyl complexes, [Ru(azo)(bpy)(CO)Cl]⁺. The novel complexes containing azo ligands were characterized by various spectroscopic measurements including the determination of X-ray crystallographic structures. Both [Ru(azo)(CO)₂Cl₂] complexes have two CO groups in a cis position to each other and two chlorides in a trans position. The azo groups are situated cis to the CO ligand in [Ru(azo)(bpy)(CO)Cl]⁺. All complexes have azo N-N bond lengths of 1.26-1.29 Å. The complexes exhibited azo-based two-electron reduction processes in electrochemical measurements. The effects of introducing azopyridyl ligands to the ruthenium carbonyl complexes were examined by ligand-based redox potentials, stretching frequencies and force constants of CO groups and bond parameters around Ru-CO moieties.     

Synthesis and characterization of heteroscorpionate dioxo-tungsten(VI) complexes

Twelve new dioxo W(VI) complexes of a family of heteroscorpionate ligands of the type [(L)WO₂Y], where L = N₂X ligand and Y = Cl or OR, have been synthesized and characterized. With the more sterically bulky ligands we show that these complexes exist as isolable cis and trans isomers and compare the rate of such isomerization with their corresponding dioxo Mo(VI) analogs.     

Stereoisomers of Mn(III) complexes of ethylenebis[(o-hydroxyphenyl)glycine]

We have prepared the Mn(III) complexes rac-Na[Mn(EHPG)]·3H₂O (1) and rac,meso-Na[Mn(EHPG)]·H₂O (2), where H₄EHPG is ethylenebis[(o-hydroxyphenyl)glycine], and determined their X-ray crystal structures. Complex 1 contains N(S,S)C(R,R) configurations at the N and C stereogenic centres, whilst in the unit cell of complex 2 there are two independent molecules, 2a (meso) and 2b (rac), with N(R,R)C(S,R) and N(R,R)C(S,S) configurations, respectively. Enantiomers of each complex are also present. The Mn(III) centres have Jahn-Teller-distorted octahedral geometry. The rac isomer has two long axial MnO(carboxylate) bonds (2.162-2.202 Å) and the equatorial plane contains two short MnN bonds (2.012-2.063 Å) trans to short MnO(phenolate) bonds (1.865-1.901 Å). The meso isomer has long axial MnN (2.194 Å) and MnO(carboxylate) (2.152 Å) bonds, and shorter equatorial MnN (2.005 Å) trans to MnO(phenolate) (1.901 Å) and MnO(carboxylate) (1.988 Å) trans to O(phenolate) (1.897 Å) bonds.     

The synthesis and X-ray structural characterization of mer and fac isomers of the technetium(I) nitrosyl complex [TcCl2(NO)(PNPpr)]

The nitrosyl complex H[TcNOCl₄] reacts with the tridentate ligand bis[(2-diphenylphosphino)propyl]amine (PNPpr) to yield a mixture of the mer or fac isomers of [TcCl₂(NO)(PNPpr)]. In acetonitrile, where the ligand is freely soluble, reaction occurs at room temperature to yield mostly the mer isomer with the linear nitrosyl ligand cis to the amine ligand; and the phosphine ligands arranged in a mutually trans orientation. The reaction in methanol requires reflux to dissolve the lipophilic ligand and generates the fac isomer of [TcCl₂(NO)(PNPpr)] as the major product, with the tridentate ligand in a facial arrangement, leaving the chlorides and nitrosyl ligand in the remaining facial sites. The steric bulk of the tridentate ligand’s diphenylphophino-moieties results in a significant distortion from octahedral geometry, with the P-Tc-P bond angle expanded to 99.48(4)°.The infrared spectra display absorptions from these nitrosyl ligands in the 1700 and 1800 cm⁻¹ regions for the fac and mer isomers, respectively. The ESI(+) mass spectra each display the parent ion at 647 m/z.     

Synthesis and X-ray structural characterization of tris(l-glycinato)vanadium(III) and trans-tetraquadichlorovanadium(III) chloride

Despite the importance of V^III in biology, only three V^III complexes of naturally occurring amino acids have been structurally characterized. We report the structure of the first vanadium complex incorporating a glycine ligand, [V(Gly)₃] · 2DMSO, which crystallizes in a monoclinic system with space group Cc, a = 8.9186(5) Å, b = 21.5347(9) Å, c = 9.9064(5) Å and β = 110.536(3)°. The X-ray structural data show the central V^III metal octahedrally coordinated by three bidentate glycinato ligands arranged a mer configuration, with both Δ and Λ enantiomers present in the unit cell. The bulk sample was isolated as [V(Gly)₃] · DMSO · NaCl. Structural comparisons are made with the corresponding homoleptic glycinato complexes of Co^III, Cr^III and Ni^II. The structure of trans-[V(OH₂)₄Cl₂]Cl · 2H₂O has also been re-determined. This latter complex crystallizes in a monoclinic system in the P2(1)/c space group, a = 6.4381(9) Å, b = 6.3843(9) Å, c = 11.7980(17) Å and β = 98.057(2)°. The vanadium atom lies at a crystallographic inversion centre within the distorted octahedron formed by the four water and two chloride ligands.     

A pyridine bridged dicarbene ligand and its silver(I) and palladium(II) complexes: synthesis, structures, and catalytic applications

The potentially tridentate ligand 2,6-bis[(3-methylimidazolium-1-yl)methyl]pyridine dibromide reacts readily with silver(I) oxide in dichloromethane or dimethylsulfoxide to give a dinuclear silver(I)-carbene complex that was isolated as the tetrafluoroborate salt. Single crystal X-ray crystallography shows that each silver(I) ion is bridged by two ligands bonding through the carbene donors. Treatment of the silver(I) complex with suitable palladium(II) precursors gave the complexes PdCl[(CNC)]BF₄ and [PdMe(CNC)]BF₄ (CNC=2,6-bis[(3-methylimidazolin-2-yliden-1-yl)methyl]pyridine), in which the pyridyl and both carbene moieties are coordinated to a single palladium(II). The palladium(II) complexes have been fully characterised, including X-ray crystallography, and exhibit good activities in the Heck coupling reaction of 4-bromoacetophenone and n-butyl acrylate.     

Synthesis, single crystal structure and DNA cleavage studies on first N-ethyl substituted three coordinate copper(I) complex of thiosemicarbazone

A copper(I) complex [Cu(CETH)₂Cl] (Ia), where CETH = cuminaldehyde-4-ethyl-3-thiosemicarbazone (I), is prepared and structurally characterised. The complex crystallizes in orthorhombic space group pna2(1) with the unit cell parameters; a = 9.8598(14) Å, b = 15.411(2) Å, c = 0.817(3) Å, V = 2055.9(4) Å³ and Z = 4. The neutral complex has the copper(I) centre bonded to two thioketonic sulphur donor in η¹-S bonding mode and one chloride giving ‘Y’ shape geometry. The complex is diamagnetic and exhibits a copper to ligand charge transfer bands at 351 and 398 nm in dimethylformamide. The complex shows quasireversible cyclic voltammetric response at 0.41 V (ΔEp = 300 mV) at 50 mVS⁻¹ in DMF for the Cu(II)/Cu(I) oxidation couple. Complex Ia shows marginal nuclease activity with pUC18 DNA in the presence of reducing agent (Dithiotretal) and hydrogen peroxide.     

Characterization and evaluation of pyrone and tropolone chelators for use in metalloprotein inhibitors

The tetrahedral zinc and cobalt complexes [(Tp^Ph,Me)ZnOH] (Tp^Ph,Me = hydrotris(3,5-phenylmethylpyrazolyl)borate) and [(Tp^Ph,Me)CoCl] were combined with 3-hydroxy-2H-pyran-2-one (3,2-pyrone), 3-hydroxy-4H-pyran-4-one (3,4-pyrone), and tropolone to form the corresponding [(Tp^Ph,Me)M(L)] complexes (L = bidentate ligand, M = Zn²⁺, Co²⁺). X-ray crystal structures of these complexes were obtained to determine the mode of binding for each chelator and the coordination geometry of each complex. The complexes [(Tp^Ph,Me)M(3,2-pyrone)] (M = Zn²⁺, Co²⁺) are the first structurally characterized metal complexes with this chelator. These complexes with the various chelators show that the cobalt(II) complexes are generally isostructural with their zinc(II) counterparts. In addition to structural characterization, inhibition data for each ligand against two different zinc(II) metalloproteins, matrix metalloproteinase-3 (MMP-3) and anthrax lethal factor (LF), were obtained. Examination of these chelators in the MMP-3 active site demonstrates the possible mode of inhibition.     

Syntheses, characterization and X-ray crystal structures of a mono- and a penta-nuclear nickel(II) complex with oximato Schiff base ligands

A mononuclear octahedral nickel(II) complex [Ni(HL¹)₂](SCN)₂ (1) and an unusual penta-nuclear complex [{(NiL²)(μ-SCN)}₄Ni(NCS)₂]·2CH₃CN (2) where HL¹ = 3-(2-aminoethylimino)butan-2-one oxime and HL² = 3-(hydroxyimino)butan-2-ylidene)amino)propylimino)butan-2-one oxime have been prepared and characterized by X-ray crystallography. The mono-condensed ligand, HL¹, was prepared by the 1:1 condensation of the 1,2-diaminoethane with diacetylmonoxime in methanol under high dilution. Complex 1 is found to be a mer isomer and the amine hydrogen atoms are involved in extensive hydrogen bonding with the thiocyanate anions. The dicondensed ligand, HL², was prepared by the 1:2 condensation of the 1,3-diaminopropane with diacetylmonoxime in methanol. The central nickel(II) in 2 is coordinated by six nitrogen atoms of six thiocyanate groups, four of which utilize their sulphur atoms to connect four NiL² moieties to form a penta-nuclear complex and it is unique in the sense that this is the first thiocyanato bridged penta-nuclear nickel(II) compound with Schiff base ligands.