Synthesis and characterization of [Co(NH3)5NO2][M(NO2)4] (M = Pt, Pd) compounds and their thermolysis products

Compounds [Co(NH₃)₅NO₂][Pd(NO₂)₄] (I) and [Co(NH₃)₅NO₂][Pt(NO₂)₄] · 1.5H₂O (II) have been crystallized from solution. Their crystal structures have been solved, and thermolysis under various conditions studied. The thermolysis products are Co_0.5M_0.5 ordered solid solutions.     

Cyanide-bridged one-dimensional bimetallic complexes based on a tridentate copper(II) building block: synthesis,crystal structures and magnetic properties

The reactions of [M^III(CN)₆]^3? (M = Cr or Co) with Cu^II complexes of a tridentate schiff base [Cu(aemp)Cl] or [Cu(aemp)Ac]₂ (Haemp = 2-[(2-amino-ethylimino)-methyl]-phenol) give rise to 1D cyanide-bridged bimetallic coordination polymers [Cu₄(aemp)₄(H₂O)₂][Cr(CN)₆]Cl (1) and [Cu₃(aemp)₃(H₂O)][Co(CN)₆]·2H₂O·MeOH (2). In complex 1, the six cyanide ligands of the [Cr(CN)₆]^3? moiety are involved in bridging, while in complex 2 only five cyanide ligands act as bridges to give a neutral chain. Magnetic studies reveal that complex 1 exhibits intermetallic ferromagnetic coupling, with J = 8.2 cm^?1.     

Cyanide-bridged complexes based on dinuclear Cu(II)-M(II) [M = Pb and Cu] building blocks: Synthesis, crystal structures and magnetic properties

Four cyanide-bridged heterometallic complexes {[CuPb(L 1 )][Fe III (bpb)(CN) 2 ]} 2 ·(ClO 4 ) 2 ·2H 2 O·2CH 3 CN (1), {[CuPb(L 1 )] 2 [Fe II (CN) 6 ](H 2 O) 2 }·10H 2 O (2), {[Cu 2 (L 2 )][Fe III (bpb)(CN) 2 ] 2 }·2H 2 O·2CH 3 OH (3) and {[Cu 2 (L 2 )] 3 [Fe III (CN) 6 ] 2 (H 2 O) 2 }·10H 2 O (4) have been synthesized by treating K[Fe III (bpb)(CN) 2 ] [bpb 2-=1,2-bis(pyridine-2-carboxamido)benzenate] and K 3 [Fe III (CN)] 6 with dinuclear compartmental macrocyclic Schiff-base complexes [CuPb(L 1 )] (ClO 4 ) 2 or [Cu 2 (L 2 )]·(ClO 4 ) 2 , in which H 2 L 1 was derived from 2,6-diformyl-4-methyl-phenol, ethylenediamine, and diethylenetriamine in the molar ratio of 2:1:1 and H 2 L 2 from 2,6-diformyl-4-methyl-phenol and propylenediamine in the molar ratio of 1:1. Single crystal X-ray diffraction analysis reveals that compound 1 displays a cyclic hexanuclear heterotrimetallic molecular structure with alternating [FeⅢ (bpb)(CN) 2 ]- and [CuPb(L 1 )] 2+ units. Complex 2 is of a neutral dumb-bell-type pentanuclear molecular configuration consisting of one [Fe(CN)6] 4- anion sandwiched in two [CuPu(L 1 )] 2+ cations, and the pentanuclear moieties are further connected by the hydrogen bonding to give a 2D supramolecular framework. Heterobimetallic complex 3 is a tetranuclear molecule composed of a centrosymmetric [Cu 2 (L2)] 2+ segment and two terminal cyanide-containing blocks [FeⅢ (bpb)(CN)2 ]- . Octanuclear compound 4 is built from two [Fe(CN)6]3- anions sandwiched in the three [Cu 2 L 2 ] 2+ cations. Investigation of their magnetic properties reveals the overall antiferromagnetic behavior in the series of complexes except 2.     

Effect of heterometallic biscitratogermanates (-stannates) of Co(II) and Ni(II) on the polycondensation and properties of poly(glycol maleate phthalate) copolymers

The ability of heterometallic Ge(IV) and Sn(IV) complexes [Co(H₂O)₆][Ge(HCitr)₂] (I), [Co(H₂O)₆] [Sn(HCitr)₂] (II), [Ni(H₂O)₆][Ge(HCitr)₂] (III), [Ni(H₂O)₆][Sn(HCitr)₂] (IV), [Mg(H₂O)₆][Ge(HCitr)₂] (V), and [Mg(H₂O)₆][Sn(HCitr)₂] (VI) (H₄Citr is citric acid) to activate polycondensation of maleic and phthalic anhydrides with ethylene glycol was studied. Copolymerization of modified poly(glycol maleate phthalate) with triethylene glycol dimethacrylate was performed, and the copolymer characteristics were determined.     

Crystallization method controlled trinuclear or ion-pair Manganese(III)-porphyrin-based heterobimetallic complexes: Synthesis,spectra characterization,and crystal structure

Cyanide-bridged trinuclear heterometallic Ag(I)-Mn(III) complex {[Mn(TClPP)(H₂O)]₂[Ag(CN)₂]}₂ · 2Br · 2C₃H₆O · 3H₂O (I) and ion-pair complex {[Mn(TClPP)(CH₃OH)₂][Ag(CN)₂]} · 0.5H₂O (II) have been synthesized with [Mn(TClTPP)(H₂O)₂]Br (H₂TClTPP = meso-tetra(4-chlorophenyl)porphyrin) as assembling segment and K[Ag(CN)₂] as building block by using different crystallization method. These two complexes have been characterized by elemental analysis, IR spectroscopy and X-ray structure determination. In the trinuclear complex I, [Ag(CN)₂]^? as bidentate ligand coordinates with the two central Mn(III) atom of [Mn(TClPP)(H₂O)₂]⁺ through its two trans cyanide groups to form the complex cation of [Mn(TClPP)(H₂O)]₂[Ag(CN)₂]⁺, which further constructs the neutral complexes with the help of one Br^? as balanced anion. For the ion-pair complex II composed by free [Mn(TClPP)(CH₃OH)₂]⁺ cation and free [Ag(CN)2]^? anion, it can be linked into one-dimensional supramolecular structure with the dependence of the intermolecular O-H...N and O-H...O hydrogen bond interactions.     

Polymers based on anionic octahedral cluster chalcocyanohydroxorhenium complexes and cations [Cu(En)2]2+

Polymer compounds [Cu(En)₂(H₂O)₂][{Cu(En)₂}Re₆S₈(CN)₄(OH)₂] · 5.5H₂O (I) and [Cu(En)₂(H₂O)₂][{Cu(En)₂}Re₆Se₈(CN)₄(OH)₂] · 5H₂O (II) are synthesized by the layering of an ammonia solution of CuCl₂ with ethylenediamine (En) on aqueous solutions of the corresponding octahedral cluster chalcocyanohydroxorhenium complexes. The compounds are characterized by IR spectroscopy and elemental and X-ray diffraction analyses.     

Iron(III) hetero-ligand complexes containing 1,10-phenanthroline derivatives, chloride and dimethyl sulfoxide: synthesis, characterization, crystal structure determination and luminescent properties

[Fe(Me-phen)Cl₄][Me-phen·H] (1) and [Fe(Cl-phen)Cl₄][Cl-phen·H] (2) complexes were prepared from the reactions of FeCl₃·6H₂O with 5-methyl-1,10-phenanthroline (Me-phen) and 5-chloro-1,10-phenanthroline (Cl-phen), respectively, in a 0.1 M aqueous solution of HCl. Stepwise addition of dimethyl sulfoxide to the solution of 1 in methanol results in a mixed ligand complex, [Fe(Me-phen)Cl₃(DMSO)] (3). Complex 3 was also prepared by two other methods. The reaction of a methanol solution of [Fe(Me-phen)Cl₄][Me-phen·H] (1) with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:6 ratio led to 3. Complex 3 was also prepared from the reaction of 5-methyl-1,10-phenanthroline with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:1 ratio in methanol. The three complexes were characterized by IR, UV–Vis, ¹H NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. Calculation methods were employed to study the isomerization of (3) in solution.     

Three silver(I) coordination polymers assembled from 2-sulfoterephthalic acid and N-donor ligands: syntheses, crystal structures, and luminescence properties

The reactions of silver nitrate with 2-sulfoisophthalic acid (H₃stp) in the presence of N-donor ligands produced three coordination polymers; [Ag₃(stp)(pyz)_0.5]_n (1), {[Ag₄(dpp)₄]·2(Hstp)·9H₂O}_n (2), and {[Ag(bpe)]₂[Ag₂(bpe)₂]₂·2(stp)·19H₂O}_n (3) [pyz = pyrazine, bpp = 1,2-bis(4-pyridyl)propane, bpe = 1,2-di(4-pyridyl)-ethylene]. The complexes have been characterized by single-crystal X-ray diffraction, physico-chemical, and spectroscopic methods. Single-crystal X-ray diffraction reveals that complex 1 is a 2D silver carboxylate-sulfonate layered structure, in which the 2D layers are further linked by the N-donor atoms of pyz ligands into a 3D supramolecular structure. Complex 2 is an infinite 1D chain arrangement with the [Ag₂(dpp)₂]²⁺ unit in which weak Ag···Ag or Ag···O interactions extend the chains into 2D structures. Complex 3 has a 3D supramolecular structure constructed by hydrogen bonding, π–π stacking, and Ag···O interactions to link the ligands, metal atoms, and water molecules together. The luminescence properties of the complexes were investigated.     

Synthesis, structure, and magnetic properties of a cyanidebridged Fe(III)-Cu(II) bimetallic double-zigzag chain with slow relaxation of the magnetization

Using Bu₄N[Fe(Tp*)(CN)₃]^? (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) as the building block to react with Cu^II and N-methylimidazole, we obtained a one-dimensional (1D) heterobimetallic cyano-bridged chain, [Fe(Tp*)(CN)₃]₂Cu(N-methylimidazole)₂·2H₂O (1). The crystal structures and magnetic studies demonstrate that complex 1 exhibits slow relaxation of the magnetization due to strong intrachain ferromagnetic coupling and weak interchain interactions.     

Synthesis, properties, and thermal decomposition of compounds [Co(En)3][Fe(CN)6] · 2H2O and [Co(En)3]4[Fe(CN)6]3 · 15H2O

Binary complex salts, [Co(En)₃][Fe(CN)6] · 2H₂O and [Co(En)₃]₄[Fe(CN)₆]₃ · 15H₂O, are synthesized. The properties of the salts and their thermolysis in air, dihydrogen, and argon are studied. Oxides of the central ions of the binary complex salts are found to be the thermolysis products in an oxidative atmosphere. Solid solutions (intermetallic compounds) CoFe are the thermolysis products in the reductive atmosphere, whereas intermetallides containing considerable amounts of C and N and an impurity of Co and Fe oxides are the thermolysis products in an inert atmosphere. Gaseous thermolysis products in dihydrogen and argon are NH₃, hydrocarbons, and ethylenediamine.     

Synthesis, spectroscopic, and thermal investigation of transition and non-transition complexes of metformin as potential insulin-mimetic agents

Complexes of [Mn(MF)₂(Cl)₂]·2H₂O (1), [Fe(MF)₂(Cl)₂]Cl·4H₂O (2), [Ni(MF·HCl)₂(Cl)₂]·6H₂O (3), [Cu(MF·HCl)₂(Cl)₂] (4), [Zn(MF·HCl)₂](NO₃)₂·6H₂O (5), [Cd₂(MF·HCl)(Cl)₄(H₂O)] (6), [Mg(MF·HCl)₂(Cl)₂]·6H₂O (7), [Sr₂(MF·HCl)(Cl)₄(H₂O)] (8), [Ba(MF·HCl)₂(Cl)₂]·2H₂O (9), [Pt(MF)₄] (10), [Au(MF)₃]Cl₃ (11), and [Pd(MF)₂]Cl₂ (12) were synthesized from Legitional behavior of metformin drug as a diabetic agent. The authenticity of the transition and non-transition metal complexes were characterized by elemental analyses, molar conductivity, (infrared, UV–Vis) spectra, effective magnetic moment in Bohr magnetons, electron spin resonance, thermal analysis, X-ray powder diffraction as well as scanning electron microscopy. Infrared spectral studies as well as elemental analyses revealed the existence of metformin in the base or hydrochloride salt forms in the chelation state acts as a bidentate ligand while the platinum(IV) complex is coordinated through the deprotonation of –NH group. The magnetic and electronic spectra of Mn(II), Fe(III), Ni(II), and Cu(II) complexes suggest an octahedral geometry. Antimicrobial screening of metformin and its complexes were determined against the (G⁺ and G^?) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans).     

First MnIII complexes with tetradentate (N2O2) Schiff bases and tricyanomethanide: synthesis,crystal structure,and magnetic properties

The first Mn^III complexes with Schiff bases and tricyanomethanide-anion were synthesized: [Mn(salen)C(CN)₃(H₂O)] (1), [Mn(5-Brsalen)C(CN)₃(H₂O)] (2), [Mn(salpn)C(CN)₃(H₂O)] (3), [Mn(3-MeOsalen)C(CN)₃(H₂O)] (4), [Mn(5-Brsalen)(MeOH)(H₂O)][C(CN)₃] (5), and [Mn(3-MeOsalpn)(H₂O)₂][C(CN)₃] (6), where SalenH₂ is N,N′-bis(salicylidene)ethylenediamine, 5-BrsalenH₂ is N,N′-bis(5-bromosalicylidene)ethylenediamine, SalpnH₂ is N,N′-bis-(salicylidene)-1,3-diaminopropane, 3-MeOsalenH₂ is N,N′-bis(3-methoxysalicylidene)-ethylenediamine, 3-MeOsalpnH₂ — N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane. The tricyanomethanide anion in complexes 1–4 acts as a the terminal ligand, whereas in complexes 5 and 6 tricyanomethanide is not coordinated by Mn^III and acts as an out-of-sphere counterion. The structures of complexes 1–4 are characterized by the formation of dimers due to hydrogen bonds between the water molecules and oxygen atoms of the Schiff bases. The Mn...Mn distances inside the dimers are 4.69–5.41 Å. Complex 6 has a zigzag chain structure consisting of the [Mn(3-MeOsalpn)(H₂O)₂]⁺ cations bound by double bridging aqua ligands. The study of the magnetic properties of complexes 1, 3, 4, and 6 showed the existence of antiferromagnetic interactions between the Mn^III ions through the system of hydrogen bonds.     

Microwave-Assisted Synthesis,Structure and Properties of a Nano-Double-Bowl-Like Heptanuclear Nickel(II) Cluster

A nano-double-bowl-like heptanuclear nickel cluster [Ni₇(mmp)₆(OH)₆]₂·(ClO₄)₂·12H₂O (1, Hmmp is 2-methoxy-6-methyliminomethyl-phenol) has been synthesized through the microwave-assisted reaction of Ni(ClO₄)₂·6H₂O with 2-hydroxy-3-methoxy-benzaldehyde (Hhmb) and methylamine in distilled water only 29 min. The core of the complex 1 can be described as a double-bowl-like, while the dodecanuclear water cluster stands on the bowl. The magnetic investigation shows that 1 displays very weak ferromagnetic coupling between Ni^II ions.     

Syntheses,crystal structures,and magnetic properties of a series of double end-on azido-bridged dinuclear manganese(II) complexes

Four azido-bridged dinuclear Mn(II) complexes, [Mn₂(phen)₄ μ-₁,₁-N₃)₂][Fe^III(bpmb)(CN)₂]₂·H₂O (1), [Mn₂(phen)₄(μ-₁,₁-N₃)₂][Fe^III(bpClb)(CN)₂]₂·H₂O (2), and [Mn₂(phen)₄(μ-₁,₁-N₃)₂][M^III(bpdmb)(CN)₂]₂·3H₂O [M = Fe (3) or Cr (4); phen = 1,10-phenanthroline, bpmb^2– = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate, bpClb^2– = 1,2-bis(pyridine-2-carboxamido) 4-chloro-benzenate, bpdmb^2– = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate], have been synthesized using the synthetic strategy of large anion inducement. Single-crystal X-ray diffraction analysis reveals that all four complexes are doubly end-on (EO) azido-bridged binuclear Mn(II) complexes with two large [M(L)(CN)₂]^– (L = bpmb^2?, bpClb^2?, or bpdmb^2?) building blocks acting as charge-compensating anions. The magnetic properties of the complexes have been investigated, and the results indicate that the magnetic coupling between two Mn(II) centers through the EO azide bridges is ferromagnetic, with J = 0.64(1) cm^?1 for 1, 0.43(1) cm^?1 for 2, 0.50(1) cm^?1 for 3, and 0.66(2) cm^?1 for 4. The magneto-structural relationships of EO azido-bridged Mn(II) systems are discussed.     

Two Zn(II) and one Mn(II) complexes using two different hydrazone ligands: spectroscopic studies and structural aspects

Three new coordination complexes of Zn(II) and Mn(II) have been synthesised using two different tridentate N,N,O donor hydrazone ligands, Hpbh and Hacpbh respectively. The complexes [Zn(pbh)₂] (1) and [Zn(acpbh)₂] (2) have been synthesized by the treatment of ZnSO₄ · 7H₂O with Hpbh and Hacpbh hydrazone ligands, respectively. The Mn(II) complex [Mn(acpbh)₂] (3) was obtained on reacting Mn(NO₃)₂ · 4H₂O with the ligand Hacpbh. The ligands Hpbh and Hacpbh were prepared by condensing pyridine-2-carboxaldehyde and 2-acetylpyridine with benzhydrazide respectively. Inspite of varying the carbonyl functionality attached to the pyridine moiety present in the hydrazone ligands in both the Schiff bases, we obtained three mononuclear complexes 1, 2, and 3 which were clearly characterized from single crystal X-ray diffraction studies. Spectroscopic investigations like IR and UV/Vis have been carried out for 1, 2, and 3. Fluorescence studies have been performed for 1 and 2. For 3 cyclic voltammetry, room temperature magnetic study and EPR measurements have been recorded.     

Synthesis,crystal structures,and luminescent properties of three cluster-based heterometallic and monometallic compounds

Two heterometallic cluster compounds and one monometallic cluster compound, namely [Ni₉Co₆(PMIDA)₆(BTC)₂(H₂O)₁₂]·6H₂O (1), [Co₁₃Zn₂(PMIDA)₆(H₂O)₁₈]·6NO₃·15H₂O (2), and [Fe₁₅(PMIDA)₆(BTC)₂(H₂O)₂₂]·38H₂O (3), have been obtained under hydrothermal conditions using N-(phosphonomethyl)imino-diacetic acid (H₄PMIDA) and 1,3,5-benzenetricarboxylate acid (H₃BTC) as ligands, and structurally characterized by X-ray crystallography. Compound 1 exhibits a 3D open framework constructed from [Ni₉Co₆(PMIDA)₆(H₂O)₁₂]⁶⁺ heteronuclear clusters and BTC^3? ligands. Compounds 2 and 3 are both zero-dimensional polynuclear clusters, further extended into 3D supramolecular structures via hydrogen-bonding interactions. However, there are some differences in their crystal structures; compound 2 features an isolated spherical heteronuclear cation cluster based on PMIDA^4? ligands, such that the NO₃ ^? anions only balance the charge, whereas compound 3 is characterized as a neutral monometallic cluster incorporating two different types of organic acid ligands, namely PMIDA^4? and BTC^3?, and the two BTC^3? ligands exhibit regular distribution in each cluster. The luminescence properties of all three compounds have been investigated at room temperature.     

Honeycomb-like layers constructed by hydrogen bonds. Synthesis, structure, and property of two new supramolecular compounds based on polyoxotungstate

Two new compounds based on polyoxotungstate [Co₂(PCA)₄(H₂O)₆][SiW₁₂O₄₀]·8H₂O (1), [Cd₂(PCA)₄(H₂O)₆][SiW₁₂O₄₀]·8H₂O (2) (PCA = pyridine-4-carboxylic acid) are prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, and thermal analysis. The results of the single crystal X-ray diffraction analysis reveal that 1 and 2 are isomorphic and two water molecules in the compounds act as the bridging groups of two cobalt or cadmium atoms, forming dinuclear coordination cations. The ligand PCA adopts a monodentate coordination mode and its uncoordinated carboxyl oxygen atom and the protonized nitrogen atom form hydrogen bonds with other ligands, by which the cations are linked into a supramolecular 2D network with hexagonal grids. The polyoxotungstate anions are arranged above and below the cationic grids. A strong emission peak at 420 nm of 2 is attributed to a ligand-metal transition.     

Three types of heterometallic structural motifs based on [Mo(CN)8]3−/4− anion and MnII cation as building blocks

The reaction between K₃[Mo(CN)₈] · H₂O and MnCl₂ · 4H₂O in different reaction conditions have obtained three new bimetallic cyanide-bridged compounds, namely, {(tetrenH₂)_0.5[Mn(H₂O)₂][Mo^V(CN)₈] · 2H₂O} _n (1) (where, tetren is tetraethylenepentamine), {[Mn₂(H₂O)₄][Mo^IV(CN)₈] · 3H₂O} _n (2), and {[Mn₂(H₂O)₄][Mo^IV(CN)₈] · 4H₂O} _n (3). Compound 1 crystallizes in the orthorhombic system with space group Cmc21 and unit cell constants a = 7.8234(15), b = 26.013(5), c = 10.021(2) Å, β = 90°, and Z = 4. Compound 2 crystallizes in the monoclinic system with space group P21/n and unit cell constants a = 7.3329(11), b = 14.372(2), c = 18.070(3) Å, β = 90.869(2)°, and Z = 4. Compound 3 crystallizes in the tetragonal system with space group I4/m and unit cell constants a = b = 11.9371(8), c = 13.2930(18) Å, β = 90°, and Z = 4. X-ray single-crystal structures reveal that the Mo centers adopt a distorted square antiprism coordination environment for 1 and 3, while 2 closed to a bicapped trigonal prism. For these complexes, all the Mn^II centers in the extended structure adopt distorted octahedron geometry. For 1, each Mo^V coordinated via four cyanide groups to four Mn^II ions, and the other four cyanide groups are terminal, forming a two-dimensional framework. For 2, the Mo^IV center of structural unit coordinated via four cyanide groups to four Mn(1), and the other four cyanide groups coordinated to four Mn(2), forming a three-dimensional framework. For 3, each [Mo^IV(CN)₈]^4? building block is linked to Mn^II ions through its eight CN ligands, and each Mn^II center is connected to four Mo units forming a three-dimensional framework. In addition, magnetic studies of these complexes have also been presented.     

Adduct formation of cadmium(II) N,N-cyclo-hexamethylenedithiocarbamate, [Cd2{S2CN(CH2)6}4], with morpholine: Synthesis, molecular structure, and thermal behavior of a crystalline adduct cis-[Cd{NH(CH2)4O}2{S2CN(CH2)6}2]

The reaction of [Cd₂{S₂CN(CH₂)₆}₄] (I) with morpholine gives a crystalline adduct of cadmium N,N-cyclo-hexamethylenedithiocarbamate [Cd{NH(CH₂)₄O}₂{S₂CN(CH₂)₆}₂] (II), whose coordination sphere includes two molecules of the donor base. The structural organization and thermal behavior of II is studied by X-ray diffraction analysis and simultaneous thermal analysis in comparison with the original binuclear cadmium complex I. The central cadmium atom (coordination number 6) coordinates two morpholine molecules and two structurally equivalent S,S’-anisobidentate ligands HmDtc to form a chromophore [CdN₂S₄] with the structure of a distorted octahedron. The thermal destruction of II proceeds in two stages and includes consecutive steps of dissociation of the Cd-N bonds followed by the desorption of morpholine and thermolysis of the dithiocarbamate moiety of the adduct to form CdS as the final product. The structure of binuclear [Cd₂{S₂CN(CH₂)₆}₄] is refined for a correct refinement of the geometric characteristics of compounds I and II.     

Hydrate isomerism in [Cu(en)2(H2O)1.935]2[Fe(CN)6]·4H2O

The title compound, bis[di­aqua­bis­(ethyl­enedi­amine‐κ²N,N′)copper(II)­] hexa­cyano­iron(II) tetrahydrate, [Cu(C₂H₈N₂)₂(H₂O)_1.935]₂[Fe(CN)₆]·4H₂O, was crystallized from an aqueous reaction mixture initially containing CuSO₄, K₃[Fe(CN)₆] and ethyl­enedi­amine (en) in a 3:2:6 molar ratio. Its structure is ionic and is built up of two crystallographically different cations, viz. [Cu(en)₂(H₂O)₂]²⁺ and [Cu(en)₂(H₂O)_1.87]²⁺, there being a deficiency of aqua ligands in the latter, [Fe(CN)₆]⁴⁻ anions and disordered solvent water mol­ecules. All the metal atoms lie on centres of inversion. The Cu atom is octahedrally coordinated by two chelate‐bonded en mol­ecules [mean Cu—N = 2.016 (2) Å] in the equatorial plane, and by axial aqua ligands, showing very long distances due to the Jahn–Teller effect [mean Cu—O = 2.611 (2) Å]. In one of the cations, significant underoccupation of the O‐atom site is observed, correlated with the appearance of a non‐coordinated water mol­ecule. This is interpreted as the partial contribution of a hydrate isomer. The [Fe(CN)₆]⁴⁻ anions form quite regular octahedra, with a mean Fe—C distance of 1.913 (2) Å. The dominant intermolecular interactions are cation–anion O—H⋯N hydrogen bonds and these inter­actions form layers parallel to (001).