Synthesis,Structural Characterization,and Antimicrobial Activities of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Triazole‐based Azodyes

The synthesis and characterization of new transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3‐(2‐hydroxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL¹ ) and 3‐(2‐hydroxy‐3‐carboxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL² ) have been carried out. Their structures were confirmed by elemental analyses, thermal analyses, spectral and magnetic data. The IR and ¹H NMR spectra indicated that HL¹ and HL² coordinated to the metal ions as bidentate monobasic ligands via the hydroxyl O and azo N atoms. The UV‐Vis, ESR spectra and magnetic moment data revealed the formation of octahedral complexes [Mn L¹ (AcO)(H₂O)₃] ( 1 ), [Co L¹ (AcO)(H₂O)₃]·H₂O ( 2 ), [Mn L² (AcO)(H₂O)₃] ( 6 ) and [Co L² (AcO)(H₂O)₃] ( 7 ), [Ni L¹ (AcO)(H₂O)] ( 3 ), [Zn L¹ (AcO)(H₂O)]·H₂O ( 5 ), [Ni L² (AcO)(H₂O)] ( 8 ), [Zn L² (AcO)(H₂O)]·10H₂O ( 10 ) have tetrahedral geometry, whereas [Cu L¹ (AcO)(H₂O)₂] ( 4 ) and [Cu L² (AcO)(H₂O)₂]·5H₂O ( 9 ) have square pyramidal geometry.. The mass spectra of the complexes under EI‐con‐ ditions showed the highest peaks corresponding to their molecular weights, based on the atomic weights of ⁵⁵Mn, ⁵⁹Co, ⁵⁸Ni, ⁶³Cu and ⁶⁴Zn isotopes; besides, other peaks containing other isotopes distribution of the metal. Kinetic and thermodynamic parameters of the thermal decomposition stages were computed from the thermal data using Coats‐Redfern method. HL² and complexes 6 – 10 were found to have moderate antimicrobial activities against Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Salmonella sp bacteria, and antifungal activity against Fusarium oxysporum, Aspergillus niger and Candida albicans. Also, in most cases, metallation increased the activity compared with the free ligand.     

Homo‐ and Heterodinuclear Ir and Rh Imine‐functionalized Protic NHC Complexes: Synthetic,Structural Studies,and Tautomerization/Metallotropism Insights

The influence of the potentially chelating imino group of imine‐functionalized Ir and Rh imidazole complexes on the formation of functionalized protic N‐heterocyclic carbene (pNHC) complexes by tautomerization/metallotropism sequences was investigated. Chloride abstraction in [Ir(cod)Cl{C₃H₃N₂(DippN=CMe)‐κN3}] ( 1 a ) (cod=1,5‐cyclooctadiene, Dipp=2,6‐diisopropylphenyl) with TlPF₆ gave [Ir(cod){C₃H₃N₂(DippN=CMe)‐κ²(C2,N_imine)}]⁺[PF₆]^? ( 3 a ⁺[PF₆]^?). Plausible mechanisms for the tautomerization of complex 1 a to 3 a ⁺[PF₆]^? involving C2?H bond activation either in 1 a or in [Ir(cod){C₃H₃N₂(DippN=CMe)‐κN3}₂]⁺[PF₆]^? ( 6 a ⁺[PF₆]^?) were postulated. Addition of PR₃ to complex 3 a ⁺[PF₆]^? afforded the eighteen‐valence‐electron complexes [Ir(cod)(PR₃){C₃H₃N₂(DippN=CMe)‐κ²(C2,N_imine)}]⁺[PF₆]^? ( 7 a ⁺[PF₆]^? (R=Ph) and 7 b ⁺[PF₆]^? (R=Me)). In contrast to Ir, chloride abstraction from [Rh(cod)Cl{C₃H₃N₂(DippN=CMe)‐κN3}] ( 1 b ) at room temperature afforded [Rh(cod){C₃H₃N₂(DippN=CMe)‐κN3}₂]⁺[PF₆]^? ( 6 b ⁺[PF₆]^?) and [Rh(cod){C₃H₃N₂(DippN=CMe)‐κ²(C2,N_imine)}]⁺[PF₆]^? ( 3 b ⁺[PF₆]^?) (minor); the reaction yielded exclusively the latter product in toluene at 110 °C. Double metallation of the azole ring (at both the C2 and the N3 atom) was also achieved: [Ir₂(cod)₂Cl{μ‐C₃H₂N₂(DippN=CMe)‐κ²(C2,N_imine),κN3}] ( 10 ) and the heterodinuclear complex [IrRh(cod)₂Cl{μ‐C₃H₂N₂(DippN=CMe)‐κ²(C2,N_imine),κN3}] ( 12 ) were fully characterized. The structures of complexes 1 b , 3 b ⁺[PF₆]^?, 6 a ⁺[PF₆]^?, 7 a ⁺[PF₆]^?, [Ir(cod){C₃HN₂(DippN=CMe)(DippN=CH)(Me)‐κ²(N3,N_imine)}]⁺[PF₆]^? ( 9 ⁺[PF₆]^?), 10? Et₂O ? toluene, [Ir₂(CO)₄Cl{μ‐C₃H₂N₂(DippN=CMe)‐κ²(C2,N_imine),κN3}] ( 11 ), and 12? 2 THF were determined by X‐ray diffraction.     

Di­aqua­tris­(pentane‐2,4‐dionato‐O,O′)­holmium(III) mono­hydrate and di­aqua­tris­(pentane‐2,4‐dionato‐O,O′)holmium(III) 4‐hydroxy­pentan‐2‐one solvate dihydrate

The structures of the title compounds, [Ho(C₅H₇O₂)₃(H₂O)₂]·H₂O and [Ho(C₅H₇O₂)₃(H₂O)₂]·C₅H₈O₂·2H₂O, both show an eight‐coordinate holmium(III) ion in a square antiprismatic configuration. The packing of these structures consists of an infinite two‐dimensional network of hydrogen‐bonded mol­ecules. In both structures, the same hydrogen‐bonded chain of Ho^III complexes is found.     

Synthesis,Interionic Structure,and Reactivity toward CO and p‐Methylstyrene of Palladacyclic Compounds Bearing α‐Diimine Ligands

Palladacyclic compounds [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] (R = Et, ⁱPr, 2,6‐ⁱPr₂C₆H₃; N? N = bpy = 2,2′‐bipyridine, or 1,4‐(o,o′‐dialkylaryl)‐1,4‐diazabuta‐1,3‐dienes; [X]^? = [BF₄]^? or [PF₆]^?) were synthesized from the dimers [{Pd(C₆H₄(C₆H₅C?O)C?N? R)(μ‐Cl)}₂] and N? N ligands. Their interionic structure in CD₂Cl₂ was determined by means of ¹⁹F,¹H‐HOESY experiments and compared with that in the solid state derived from X‐ray single‐crystal studies. [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] complexes were found to copolymerize CO and p‐methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4‐(o,o′‐dimethylaryl)‐1,4‐diazabuta‐1,3‐dienes were used, respectively. The reactions with CO and p‐methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd? C bonds were isolated and completely characterized in solution.     

N,N′‐Di­methyl­piperazinium(2+) phos­phonoacetate: hydrogen‐bonded anion sheets containing cation‐templated R66(28) rings

In the title compound, C₆H₁₆N₂²⁺·2C₂H₄O₅P^?, the cations lie across centres of inversion; in the anions, two of the H‐atom sites have 0.50 occupancy. The anions are linked by short O—H?O hydrogen bonds [O?O 2.465 (3)–2.612 (3) Å and O—H?O 165–171°] into sheets of alternating R(12) and R(28) rings, both of which are centrosymmetric; the cations lie at the centres of the larger rings linked to the anion sheet by N—H?O hydrogen bonds [N?O 2.642 (2) Å and N—H?O 176°].     

Investigation on Sonocatalytic Damage to Bovine Serum Albumin (BSA) Under Ultrasonic Irradiation in the Presence of Fe(III)–Citrate Complexes

The interaction of bovine serum albumin (BSA) with Fe(III)?Ccitrate complexes ([Fe^III(cit)(H₂O)₃]^? and [Fe^III(cit)₂]^5?) and the sonocatalytic damage of BSA under ultrasonic irradiation were studied. Additionally, the various factors influencing the sonocatalytic damage of BSA were also studied by means of UV?CVis and fluorescence spectra. The experimental results indicate that the probable fluorescence quenching mechanisms of BSA by Fe(III)?Ccitrate complexes ([Fe^III(cit)(H₂O)₃]^? and [Fe^III(cit)₂]^5?) are both static quenching. Under certain conditions, the degree of damage to BSA is aggravated with increases of ultrasonic irradiation time, Fe(III)?Ccitrate complex concentration, pH value and ionic strength. Moreover, all of the results demonstrate that [Fe^III(cit)₂]^5? displays higher sonocatalytic activity than [Fe^III(cit)(H₂O)₃]^? under the same experimental conditions during the damage process of BSA. Finally, the generation of ·O₂ ^? and ·OH during sonocatalytic processes was estimated using scavengers. Perhaps, the results will be significant for promoting sonodynamic treatment to treat tumors at the molecular level.     

1‐Oxa‐nido‐dodecaborate [OB11H12]− from the Controlled Oxidation of the closo‐Borates [B11H11]2− and [B12H12]2−

The closo‐dodecaborate [B₁₂H₁₂]^2? is degraded at room temperature by oxygen in an acidic aqueous solution in the course of several weeks to give B(OH)₃. The degradation is induced by Ag²⁺ ions, generated from Ag⁺ by the action of H₂S₂O₈. Oxa‐nido‐dodecaborate(1?) is an intermediate anion, that can be separated from the reaction mixture as [NBzlEt₃][OB₁₁H₁₂] after five days in a yield of 18 %. The action of FeCl₃ on the closo‐undecaborate [B₁₁H₁₁]^2? in an aqueous solution gives either [B₂₂H₂₂]^2? (by fusion) or nido‐B₁₁H₁₃(OH)^? (by protonation and hydration), depending on the concentration of FeCl₃. In acetonitrile, however, [B₁₁H₁₁]^2? is transformed into [OB₁₁H₁₂]^? by Fe³⁺ and oxygen. The radical anions [B₁₂H₁₂] ^{˙ ?} and [B₁₁H₁₁] ^{˙ ?} are assumed to be the primary products of the oxidation with the one‐electron oxidants Ag²⁺ and Fe³⁺, respectively. These radical anions are subsequently transformed into [OB₁₁H₁₂]^? by oxygen. The crystal structure analysis shows that the structure of [OB₁₁H₁₂]^? is derived from the hypothetical closo‐oxaborane OB₁₂H₁₂ by removal of the B3 vertex, leaving a non‐planar pentagonal aperture with a three‐coordinate O vertex, as predicted by NMR spectra and theory.     

Kinetics and mechanism of oxidation of the binary and ternary complexes of chromium(III) involving inosine and glycine by N -bromosuccinimide

The kinetics of oxidation of the chromium(III) complexes, [Cr(Ino)(H₂O)₅]³⁺ and [Cr(Ino)(Gly)(H₂O)₃]²⁺ (Ino?=?Inosine and Gly?=?Glycine) involving a ligands of biological significance by N-bromosuccinimide (NBS) in aqueous solution to chromium(VI) have been studied spectrophotometrically over the 25–45°C range. The reaction is first order with respect to both [NBS] and [Cr], and increases with pH over the 6.64–7.73 range in both cases. The experimental rate law is consistent with a mechanism in which the hydroxy complexes [Cr(Ino)(H₂O)₄(OH)]²⁺ and [Cr(Ino)(Gly)(H₂O)₂(OH)]⁺ are significantly more reactive than their conjugate acids. The value of the intramolecular electron transfer rate constant, k ₁, for the oxidation of the [Cr(Ino)(H₂O)₅]³⁺ (6.90?×?10^?4?s^?1) is lower than the value of k ₂ (9.66?×?10^?2?s^?1) for the oxidation of [Cr(Ino)(Gly)(H₂O)₂]²⁺ at 35°C and I?=?0.2?mol?dm^?3. The activation parameters have been calculated. Electron transfer apparently takes place via an inner-sphere mechanism.     

The effect of the substituents in the malonate anion and the solvent molecules on the structures of novel coordination polymers [Li2VO(R2mal)2]n

Reactions of vanadyl sulfate (VOSO₄?3H₂O) with dimethylmalonic (H₂Me₂mal = = C₃H₆(CO₂H)₂), cyclobutane-1,1-dicarboxylic (H₂cbdc = C₄H₆(CO₂H)₂), or butylmalonic acid (H₂Bumal = C₄H₁₀(CO₂H)₂) and Li₂CO₃ in a ratio of 1: 2: 2 afforded novel coordination polymers of similar compositions ([Li₂(VO)(Me₂mal)₂]_n (1), [Li₂(VO)(Me₂mal)₂(EtOH)-(H₂O)]_n (2), [Li₄(VO)₂(cbdc)₄(H₂O)₇]_n (3), and [Li₂(VO)(Bumal)₂(H₂O)_5.5]_n (4)) but different structures. The crystal structures of the compounds containing the Me₂mal^2– and Bumal^2– anions depend on the solvent nature.     

Guest‐Triggered Supramolecular Isomerism in a Pillared‐Layer Structure with Unusual Isomers of Paddle‐Wheel Secondary Building Units by Reversible Single‐Crystal‐to‐Single‐Crystal Transformation

Solvothermal reaction of Zn(NO₃)₂ ? 4 H₂O, 1,4‐bis[2‐(4‐pyridyl)ethenyl]benzene (bpeb) and 4,4′‐oxybisbenzoic acid (H₂obc) in the presence of dimethylacetamide (DMA) as one of the solvents yielded a threefold interpenetrated pillared‐layer porous coordination polymer with pcu topology, [Zn₂(bpeb)(obc)₂] ? 5 H₂O ( 1 ), which comprised an unusual isomer of the well‐known paddle‐wheel building block and the trans–trans–trans isomer of the bpeb pillar ligand. When dimethylformamide (DMF) was used instead of DMA, a supramolecular isomer [Zn₂(bpeb)(obc)₂] ? 2 DMF ? H₂O ( 2 ), with the trans–cis–trans isomer of the bpeb ligand with a slightly different variation of the paddle‐wheel repeating unit, was isolated. In MeOH, single crystals of 2 were transformed by solvent exchange in a single‐crystal‐to‐single‐crystal (SCSC) manner to yield [Zn₂(bpeb)(obc)₂] ? 2 H₂O ( 3 ), which is a polymorph of 1 . SCSC conversion of 3 to 2 was achieved by soaking 3 in DMF. Compounds 1 and 2 as well as 2 and 3 are supramolecular isomers.     

Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution

The kinetics of stripping of Ni²⁺ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H₂A₂, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is F_b (kmol/m²s) = 10^?4.35 [Ni²⁺] (1+10^?3.42 [H⁺]^?1)^?1 ([H₂A₂]_(o)^0.5+2.50 [H₂A₂]_(o))^?1 (1+6[SO₄^2?]) (1+3.20 [Ac^?]). Activation energy (E_a), entropy change in activation (ΔS^±), and enthalpy change in activation (ΔH^±) were measured under different experimental conditions. Based on the empirical flux equation, E_a and ΔS^±, the mechanism of Ni²⁺ stripping is provided. In a low [H⁺] region, the stripping reaction steps appear as [NiA⁺] → Ni²⁺ + A^? and [Ni(HA₂)₂]_(int) → [NiHA₂]⁺_(int) + HA_2(int)^? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO₄^2?] and [Ac^?] are kept low. However, at higher [H⁺] concentrations, the stripping is under diffusion control. With increasing [SO₄^2?] and [Ac^?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO₄^2? or HSO₄^? and Ac^? to form NiSO₄ or NiHSO₄⁺ and NiAc⁺ complexes. Negative ΔS^± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (S_N2) mechanism.     

Mechanistic Studies on the Oxidation of Nitrite by a μ‐Oxodiiron(III,III) Complex in Aqueous Acidic Media

Examined in this study is the kinetics of a net 2e⁻ transfer between [Fe₂(μ‐O)(phen)₄(H₂O)₂]⁴⁺ ( 1 ) and its hydrolytic derivatives [Fe₂(μ‐O)(phen)₄(H₂O)(OH)]³⁺ ( 2 ) and [Fe₂(μ‐O)(phen)₄(OH)₂]²⁺ ( 3 ) with in aqueous media and in presence of excess 1,10‐phenanthroline (phen). The reaction is quantitative with a 1 : 1 stoichiometry between the oxidant and reductant to produce ferroin ([Fe(phen)₃]²⁺) and . The order of reactivity of the oxidant species is 1 > 2 > 3 , in agreement with the progressive cationic charge reduction. The reactions appear to be inner‐sphere where the initial one‐electron proton‐coupled redox (1e⁻, 1H⁺; electroprotic) seems to be rate‐determining.     

2‐Amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium 2‐(3,4‐di­chloro­phenoxy)­acetate

The 1:1 organic salt of the title compound, C₇H₆ClN₂O⁺·C₈H₅Cl₂O₃^? or [(2‐ABOX)(3,4‐D)], comprises the two constituent mol­ecules associated by an R₂²(8) graph‐set interaction through the carboxyl­ate group of 3,4‐D across the protonated N/N sites of 2‐ABOX [N?O 2.546 (3) and 2.795 (3) Å]. Cation/anion pairs associate across an inversion centre forming discrete tetramers via an additional three‐centre hydrogen‐bonding association from the latter N amino proton to a phenoxy O atom [N?O 3.176 (3) Å] and a carboxyl­ate O atom [N?O 2.841 (3) Å]. This formation differs from the polymeric hydrogen‐bonded chains previously observed for adduct structures of 2‐ABOX with carboxyl­ic acids.     

Polymeric diaqua(μ2‐2,2′‐bipyrimidinyl‐κ4N1,N1′:N3,N3′)‐di‐μ3‐hydroxy‐bis(μ5‐benzene‐1,3,5‐tricarboxylato‐κ5O1:O2:O3:O3:O5)tetracobalt(II) dihydrate

The structure of the title compound, [Co₄(C₉H₃O₆)₂(OH)₂(C₈H₆N₄)(H₂O)₂]·2H₂O, contains three separate species, namely the μ₅‐bridging C₉H₃O₆^3? anion, the doubly chelating and therefore μ₂‐bridging C₈H₆N₄ ligand (bi­pyrimidine, BPM), and the dihydrated di­aqua­di­hydroxy tetranuclear cationic cluster, [Co₄(OH^?)₂(H₂O)₂]⁶⁺·2H₂O, which lies on a crystallographic centre of symmetry, as does the BPM ligand with, in this case, the centre of symmetry coincident with the midpoint of the C—C bond joining the six‐membered rings. Within the cation cluster, the Co atoms of one pair are five‐coordinate and those of the other six‐coordinate.     

Electron‐Rich Diferrous–Phosphane–Thiolates Relevant to Fe‐only Hydrogenase: Is Cyanide “Nature's Trimethylphosphane”?

The two‐step one‐pot oxidative decarbonylation of [Fe₂(S₂C₂H₄)(CO)₄(PMe₃)₂] ( 1 ) with [FeCp₂]PF₆, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2 – 6 , containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1 ²⁺ as the initial intermediate of the oxidation of 1 , even when a deficiency of the oxidant was employed. Subsequent addition of PR₃ gave rise to [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₃(PMe₃)₃]²⁺ ( 2 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₂(PR₃)₂]²⁺ (R=Me 3 , OMe 4 ) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₃(MeCN)]²⁺ ( 5 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)(PMe₃)₄(MeCN)]²⁺ ( 6 ) were fully characterized. Relevant to the H_red state of the active site of Fe‐only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.     

A novel metallo‐organically templated pentaborate: acetato[N,N′‐bis(2‐aminoethyl)ethane‐1,2‐diamine]zinc(II) 4,4′,6,6′‐tetrahydroxy‐2,2′‐spirobi[cyclotriboroxane](1−)

The title compound, [Zn(C₂H₃O₂)(C₆H₁₈N₄)][B₅O₆(OH)₄], contains mixed‐ligand [Zn(CH₃COO)(teta)]⁺ complex cations (teta is triethylenetetramine) and pentaborate [B₅O₆(OH)₄]⁻ anions. The [B₅O₆(OH)₄]⁻ anions are connected to one another through hydrogen bonds, forming a three‐dimensional supramolecular network, in which the [Zn(CH₃COO)(teta)]⁺ cations are located.     

Acetonyl­di­chloro­[(Z)‐2‐chloro‐2‐phenyl­vinyl]­tellurium(IV), helical chains of metal complexes

The primary geometry about the Te^IV atom in the title compound, [TeCl₂(C₈H₆Cl)(C₃H₅O)] or C₁₁H₁₁Cl₃OTe, is a pseudo‐trigonal‐bipyramidal arrangement, with two Cl atoms in apical positions, and the lone pair of electrons and C atoms in the equatorial plane. The Te^IV atom is involved in three secondary interactions, two intramolecular [Te?O = 2.842 (3) Å and Te?Cl3 = 3.209 (1) Å] and one intermolecular [Te?Cl = 3.637 (1) Å], the latter giving rise to a helical chain. These helices are linked by C—H?O interchain interactions.     

Dysprosiacarboranes as Organometallic Single‐Molecule Magnets

The dicarbollide ion, nido‐C₂B₉H₁₁^2? is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C₂B₉H₁₁)₂Ln(THF)₂][Na(THF)₅] (Ln=Dy, 1Dy ) and [(THF)₃(μ‐H)₃Li]₂[{η⁵‐C₆H₄(CH₂)₂C₂B₉H₉}Dy{η²:η⁵‐C₆H₄(CH₂)₂C₂B₉H₉}₂Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central Dy^III ion. The effective energy barrier (U_eff) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido‐C₂B₉H₁₁^2? and nido‐[o‐xylylene‐C₂B₉H₉]^2?, which show a U_eff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C₂B₉H₁₁)₂]^? is predicted to have comparable properties with the linear [Dy(Cp^Me3)₂]⁺ complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high‐performance single‐molecule magnets.     

[Ni(terpy)(H2O)]‐trans‐[Ni‐(μ‐CN)2‐(CN)2]n,a one‐dimensional linear tetra­cyano­nickelate chain

The one‐dimensional chain catena‐poly­[[aqua(2,2′:6′,2′′‐terpyridyl‐κ³N)­nickel(II)]‐μ‐cyano‐κ²N:C‐[bis­(cyano‐κC)nickelate(II)]‐μ‐cyano‐κ²C:N], [Ni(terpy)(H₂O)]‐trans‐[Ni‐μ‐(CN)₂‐(CN)₂]_n or [Ni₂­(CN)₄­(C₁₅H₁₁N₃)(H₂O)], consists of infinite linear chains along the crystallographic [10] direction. The chains are composed of two distinct types of nickel ions, paramagnetic octahedral [Ni(terpy)(H₂O)]²⁺ cations (with twofold crystallographic symmetry) and diamagnetic planar [Ni(CN)₄]^2? anions (with the Ni atom on an inversion center). The [Ni(CN)₄]^2? units act as bidentate ligands bridging through two trans cyano groups thus giving rise to a new example of a trans–trans chain among planar tetra­cyano­nickelate complexes. The coordination geometry of the planar nickel unit is typical of slightly distorted octahedral nickel(II) complexes, but for the [Ni(CN)₄]^2? units, the geometry deviates from a planar configuration due to steric interactions with the ter­pyridine ligands.