Grid‐like Cobalt(II) Layered Complex with an Unprecedented Double 1,2‐Bis(1,2,4‐triazole‐1‐yl)methane Bridges

A novel two‐dimensional cobalt complex, [Co(btrm)₂(dca)]ClO₄ ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R₁ = 0.0784, wR₂ = 0.2041. The cobalt atom involves a six‐coordinated CoN₆ environment, with a distorted octahedral coordination. Two btrm ligands connect the Co^II atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ_1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated.     

Cobalt(II) Complexes with Dicyanamide — from Binuclear Entities to Chains

One binuclear complex [Co(bpm*)₂(dca)]₂(ClO₄)₂ ( 1 ) and two 1D chain Co^II complexes, {[Co(bpm)₂(dca)](ClO₄)}_n ( 2 ) and [Co(dmf)₂(dca)₂]_n ( 3 ), (bpm*: bis[(3, 5‐dimethyl)pyrazolyl]methane; bpm: bis(pyrazolyl)methane; dca: dicyanamide; dmf: N, N‐dimethyl formamide) have been prepared and structurally characterized. The cobalt atoms are hexa‐coordinated forming a slightly distorted octahedral coordination. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, a = 9.849(3)Å, b = 21.944(7)Å, c = 13.814(5)Å, β = 94.824(6), Z = 4, R₁ = 0.0672, wR₂ = 0.1395. 1 is a binuclear complex linked by two dca ligands, and each Co^II ion is coordinated by two terminal bpm* ligands. Compound 2 crystallizes in the orthorhombic system, space group Cmcm, a = 10.377(4)Å, b = 13.594(5)Å, c = 15.999(6)Å, Z = 4, R₁ = 0.0609, wR₂ = 0.1328. The structure of 2 can be described as a one‐dimensional zigzag chain of Co^II ions bridged by one dca ligand. Each Co^II ion in the chain is coordinated by two bpm ligands. Compound 3 crystallizes in the monoclinic system, space group C₂, a = 13.559(15)Å, b = 7.393(8)Å, c = 8.110(9)Å, β = 112.228(15), Z = 2, R₁ = 0.0260, wR₂ = 0.0760. 3 has a one‐dimensional linear chain of Co^II ions bridged by two dca ligands, in which each Co^II ion is coordinated with two dmf molecules.     

Synthesis,Crystal Structure and Thermal Behavior of 4,5‐Diacetoxyl‐2‐(dinitromethylene)‐imidazolidine

A new energetic material, 4,5‐diacetoxyl‐2‐(dinitromethylene)‐imidazolidine (DADNI), was synthesized by the reaction of 4,5‐dihydroxyl‐2‐(dinitromethylene)‐imidazolidine (DDNI) and acetic anhydride, and characterized by single crystal X‐ray diffraction. Crystal data for DADNI are monoclinic, space group C2/c, a=15.9167(3) Å, b=8.6816(4) Å, c=8.5209(3) Å, β=103.294(9)°, V=1145.9(3) ų, Z=4, µ=0.150 mm⁻¹, F(000)=600, D_c=1.682 g·cm⁻³, R₁=0.0565 and wR₂=0.1649. Thermal decomposition behavior of DADNI was studied and an intensely exothermic process was observed. The kinetic equation of the decomposition reaction is: dα/dT=(10^16.64/β)×4α^3/4exp(−1.582×10⁵/RT). The critical temperature of thermal explosion is 163.76°C. The specific heat capacity of DADNI was studied with micro‐DSC method and theoretical calculation method. The molar heat capacity is 343.30 J·mol⁻¹·K⁻¹ at 298.15 K. The adiabatic time‐to‐explosion of DADNI was calculated to be 87.7 s.     

Syntheses and Structures of two 1‐D Complexes, [Co(dmf)2(NCNCN)2] and [Cu(bipy)(NCNCN)]ClO4 with Bridging Dicyanamide Ligands

Two novel dicyanamide complexes [Co(dmf)₂(NCNCN)₂] ( 1 ) and [Cu(bipy)(NCNCN)]ClO₄ ( 2 ) have been synthesized and structurally characterized. 1 crystallizes in the monoclinic space group C2 with a = 13.568(6)Å, b = 7.403(3)Å, c = 8.118(3)Å and Z = 2, whereas 2 crystallizes in the monoclinic system, Cc group, a = 14.270(7)Å, b = 9.143(5)Å, c = 12.371(1) Å, β = 118.612(7)°, and Z = 4. According to X‐ray crystallographic studies, in complex 1 each Co^II ion is six‐coordinated with four nitrogen atoms from four μ_{1, 5}‐dca (dca = dicyanamide) ligands and two oxygen atoms from two dmf ligands to form distorted octahedra. 1 forms a 1‐D network bridged via μ_{1, 5}‐dca. 2 consists of a uniform Cu(NCNCN)Cu chain, each Cu^II ion is octahedrally coordinated with four nitrogen atoms from two μ_{1, 5}‐dca ligands and one bipy ligand and two oxygen atoms from two ClO₄^— ions. The octahedral Cu^II ion shows a significant Jahn‐Teller distortion, with two axial oxygen atoms considerably farther from the copper than the four equatorial nitrogens.     

Synthesis of trans‐disubstituted cyclam ligands appended with two 6‐hydroxymethylpyridin‐2‐ylmethyl sidearms: Crystal structures of the 1,8‐dimethyl‐4,ll‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)cylam ligand and its Co(II) and Ni(II) complexes

Two new trans‐disubstituted cyclam ligands; 1,8‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)‐1,4,8,11‐tetra‐azacyclotetradecane ( 5 ) and 1,8‐dimethyl‐4, 11‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)‐1,4,8,11 ‐tetraaza‐cyclotetradecane ( 6 ); have been synthesized and characterized. The crystal structures of ligand 6 and its Ni(II) and Co(II) complexes have been determined. Crystal data are given for 6 , space group, P2₁/c, a = 11.095 (6) Å, b = 9.467 (5) Å, c = 13.283 (8) Å; β = 106.95 (5)°, Z = 2, R = 0.0715; for [Ni 6 ](C10₄)₂, space group P2₁/c, a = 9.4848 (14) Å, b = 33.941(6) Å, c = 9.793(2) A, β = 95.264(14)°, Z = 4, R = 0.0567; for [Co 6 ](C10₄)₂, space group, P2₁/c, a = 9.440 (6) Å, b = 33.848 (13) Å, c = 9.820 (3) Å, β = 95.16(3)°, Z = 4, R = 0.0718. In both complexes, the metal atoms are six‐coordinate with only one of the pendants interacting with the central metal atom and the other pendant remaining uncoordinated.     

Syntheses,and Crystal Structures of Indium Complexes with η2‐Piperidinyldithiocarbamate and η2‐Pyridine‐2‐Thionate Containing Ligands: Structures of [In(η2‐S2CNC5H10)3] and [In(η2‐pyS)3]

The η²‐thio‐indium complexes [In(η²‐thio)₃] (thio = S₂CNC₅H₁₀, 2 ; SNC₄H₄, (pyridine‐2‐thionate, pyS, 3 ) and [In(η²‐pyS)₂(η²‐acac)], 4 , (acac: acetylacetonate) are prepared by reacting the tris(η²‐acac)indium complex [In(η²‐acac)₃], 1 with HS₂CNC₅H₁₀, pySH, and pySH with ratios of 1:3, 1:3, and 1:2 in dichloromethane at room temperature, respectively. All of these complexes are identified by spectroscopic methods and complexes 2 and 3 are determined by single‐crystal X‐ray diffraction. Crystal data for 2 : space group, C2/c with a = 13.5489(8) Å, b = 12.1821(7) Å, c = 16.0893(10) Å, β = 101.654(1)°, V = 2600.9(3) ų, and Z = 4. The structure was refined to R = 0.033 and Rw = 0.086; Crystal data for 3 : space group, P2₁ with a = 8.8064 (6) Å, b = 11.7047 (8) Å, c = 9.4046 (7) Å, β = 114.78 (1)°, V = 880.13(11) ų, and Z = 2. The structure was refined to R = 0.030 and Rw = 0.061. The geometry around the metal atom of the two complexes is a trigonal prismatic coordination. The piperidinyldithiocarbamate and pyridine‐2‐thionate ligands, respectively, coordinate to the indium metal center through the two sulfur atoms and one sulfur and one nitrogen atoms, respectively. The short C‐N bond length in the range of 1.322(4)–1.381(6) Å in 2 and C‐S bond length in the range of 1.715(2)–1.753(6) Å in 2 and 3 , respectively, indicate considerable partial double bond character.     

Synthesis,crystal structure and magnetic properties of (acetato‐κ2O,O′)bis(5,5′‐dimethyl‐2,2′‐bipyridine‐κ2N,N′)nickel(II) perchlorate monohydrate

The title hydrated ionic complex, [Ni(CH₃COO)(C₁₂H₁₂N₂)₂]ClO₄·H₂O or [Ni(ac)(5,5′‐dmbpy)₂]ClO₄·H₂O (where 5,5′‐dmbpy is 5,5′‐dimethyl‐2,2′‐bipyridine and ac is acetate), (1), was isolated as violet crystals from the aqueous ethanolic nickel acetate–5,5′‐dmbpy–KClO₄ system. Within the complex cation, the Ni^II atom is hexacoordinated by two chelating 5,5′‐dmbpy ligands and one chelating ac ligand. The mean Ni—N and Ni—O bond lengths are 2.0628 (17) and 2.1341 (15) Å, respectively. The water solvent molecule is disordered over two partially occupied positions and links two complex cations and two perchlorate anions into hydrogen‐bonded centrosymmetric dimers, which are further connected by π–π interactions. The magnetic properties of (1) at low temperatures are governed by the action of single‐ion anisotropy, D, which arises from the reduced local symmetry of the cis‐NiO₂N₄ chromophore. The fitting of the variable‐temperature magnetic data (2–300 K) gives g_iso = 2.134 and D/hc = 3.13 cm⁻¹.     

catena‐Poly[thorium(IV)‐tetrakis(μ2‐3‐carboxyadamantane‐1‐carboxylato)]: a quadruple helical strand driven by a synergy of coordination and hydrogen bonding

The title compound, [Th(C₁₂H₁₅O₄)₄]_n, is the first homoleptic thorium–carboxylate coordination polymer. It has a one‐dimensional structure supported by the bidentate bridging coordination of the singly charged 3‐carboxyadamantane‐1‐carboxylate (HADC⁻) anions. The metal ion is situated on a fourfold axis (site symmetry 4) and possesses a square‐antiprismatic ThO₈ coordination, including four bonds to anionic carboxylate groups [Th—O = 2.359 (2) Å] and four to neutral carboxyl groups [Th—O = 2.426 (2) Å], while a strong hydrogen bond between these two kinds of O‐atom donor [O...O = 2.494 (3) Å] affords planar pseudo‐chelated Th{CO₂...HO₂C} cycles. This combination of coordination and hydrogen bonding is responsible for the generation of quadruple helical strands of HADC⁻ ligands, which are wrapped around a linear chain of Th^IV ions [Th...Th = 7.5240 (4) Å] defining the helical axis.     

Self‐Assembly,Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex

The self‐assembly of NiCl₂·6H₂O with a diaminodiamide ligand 4,8‐diazaundecanediamide (L‐2,3,2) gave a [Ni(C₉H₂₀N₄O₂)(Cl)(H₂O)] Cl·2H₂O ( 1 ). The structure of 1 was characterized by single‐crystal X‐ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two O atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) Å, b = 12.3463(4) Å, c = 14.6305(5) Å, Z = 4. Through NH···Cl–Ni (H···Cl 2.42 Å, N···Cl 3.24 Å, NH···Cl 158°) and OH···Cl–Ni contacts (H···Cl 2.36 Å, O···Cl 3.08 Å, OH···Cl 143°), each cationic moiety [Ni(C₉H₂₀N₄O₂) (Cl)(H₂O)]⁺ in 1 is linked to neighboring ones, producing a charged hydrogen‐bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L‐2,3,2)²⁺ in aqueous solution shows four absorption bands, which are assigned to the ³A_2g → ³T_2g, ³T_2g → ¹Eg, ³T_2g → ³T_1g, and ³A_2g → ³T_1g transitions of triplet‐ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni²⁺ is more easily reduced than Ni(L‐2,3,2)²⁺ in aqueous solution.     

Synthesis,Spectroscopic, and X‐Ray Diffraction Studies of cis‐Dichlorobis(4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl3 H‐pyrazol‐3‐onato) Tin(IV)

Reaction between an aqueous ethanol solution of tin(II) chloride and that of 4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐one in the presence of O₂ gave the compound cis‐dichlorobis(4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐onato) tin(IV) [(C₂₆H₂₆N₄O₄)SnCl₂]. The compound has a six‐coordinated Sn^IV centre in a distorted octahedral configuration with two chloro ligands in cis position. The tin atom is also at a pseudo two‐fold axis of inversion for both the ligand anions and the two cis‐chloro ligands. The orange compound crystallizes in the triclinic space group P 1 with unit cell dimensions, a = 8.741(3) Å, b = 12.325(7) Å, c = 13.922(7) Å; α = 71.59(4), β = 79.39(3), γ = 75.18(4); Z = 2 and D_x = 1.575 g cm^–3. The important bond distances in the chelate ring are Sn–O [2.041 to 2.103 Å], Sn–Cl [2.347 to 2.351 Å], C–O [1.261 to 1.289 Å] and C–C [1.401 Å] the bond angles are O–Sn–O 82.6 to 87.7° and Cl–Sn–Cl 97.59°. The UV, IR, ¹H NMR and ¹¹⁹Sn Mössbauer spectral data of the compound are reported and discussed.     

[1‐Allylpyridinium][Cu2Cl3]: Synthesis,X‐ray Structure and the Regularity of Crystal Architecture of 1‐Allyl/(amino)‐pyridinium Copper(I) Chloride π‐Complexes

By alternating‐current electrochemical technique crystals of copper(I) π‐complex with 1‐allylpyridinium chloride of [C₅H₅N(C₃H₅)][Cu₂Cl₃] ( 1 ) composition have been obtained and structurally investigated. Compound 1 crystallizes in monoclinic system, space group C2/c a = 24.035(1) Å, b = 11.4870(9) Å, c = 7.8170(5) Å, β = 95.010(5)°, V = 2150.0(2) ų (at 100 K), Z = 8, R = 0.028, for 4836 independent reflections. In the structure 1 trigonal‐pyramidal environment of π‐coordinated copper(I) atom is formed by a lengthened to 1.376(2) Å C=C bond of allyl group and by three chlorine atoms. Other two copper atoms are tetrahedrally surrounded by chlorine atoms only. The coordination polyhedra are combined into an original infinite (Cu₄Cl₆^2—)_n fragment. Structural comparison of 1 and the recently studied copper(I) chloride π‐complexes with 3‐amino‐, 2‐amino‐, 4‐amino‐1‐allylpyridinium chlorides of respective [LCu₂Cl₃] ( 2 ), [L₂Cu₂Cl₄] ( 3 ), and [LCuCl₂] ( 4 ) compositions allowed us to reveal the trend of the inorganic fragment complication which depends on pKa (base) value of the corresponding initial heterocycle.     

Complex Formation of 2, 6‐Bis‐(2′‐hydroxyphenyl)pyridine with AlIII,FeIII and CuII

Complex formation of 2, 6‐bis(2′‐hydroxyphenyl)pyridine (H₂Lⁱ) with Fe³⁺ and Cu²⁺ was investigated in a H₂O/DMSO medium (mole fraction x_DMSO = 0.2) by potentiometric and spectrophotometric methods. The pK_a values of [H₃Lⁱ]⁺ are 2.25, 10.51 and 14.0 (25 °C, 0.1 M KCl). The formation constants of [Fe^III(Lⁱ)]⁺ and [Cu^II(Lⁱ)] (25 °C, 0.1 M KCl) are log β₁ = 21.5 for Fe³⁺ and log β₁ = 18.5 for Cu²⁺. The crystal structures of [Al(Lⁱ)₂Na(EtOH)₃], [Fe(Lⁱ)₂Na(EtOH)₃], and [Cu(Lⁱ)(py)]₂ were investigated by single‐crystal X‐ray diffraction analyses. The Fe^III and the Al^III compound are isotypic and crystallize in the monoclinic space group P2₁/n. Al‐compound (215 K): a = 12.599(3) Å, b = 16.653(3) Å, c = 17.525(4) Å, β = 100.27(3)°, Z = 4 for C₄₀H₄₀AlN₂NaO₇; Fe‐compound (293 K): a = 12.753(3) Å, b = 16.715(3) Å, c = 17.493(3) Å, β = 99.68(3)°, Z = 4 for C₄₀H₄₀FeN₂NaO₇. Both compounds contain a homoleptic, anionic bis‐complex [M(Lⁱ)₂]^‐ of approximate D₂ symmetry. The Cu compound crystallized as an uncharged, dinuclear and centrosymmetric [Cu(Lⁱ)(py)]₂ complex in the monoclinic space group P2₁/n with (293 K) a = 13.386(3) Å, b = 9.368(2) Å, c = 14.656(3) Å, β = 100.65(3)°, Z = 2 for C₄₄H₃₂Cu₂N₄O₄. The structural properties and in particular the possible influence of the ligand geometry on the stability of the metal complexes is discussed.     

The crystal structure of 9‐chloro‐4,5‐dihydro‐2‐ethyl‐1‐(2,4,6‐trichlorophenyl)‐1H‐1,2,4‐triazolo[3,2‐d][1,5]‐benzoxazepinium hexachloroantimonate

The title compound 4 , i.e. 9‐chloro‐4,5‐dihydro‐2‐ethyl‐1‐(2,4,6‐trichlorophenyl)‐1H‐1,2,4‐triazolo[3,2‐d]‐[1,5]benzoxazepinium hexachloroantimonate, is a novel 6‐7‐5 tricyclic heterocycle. C₁₈H₁₄Cl₄N₃O·SbCJ₆, M = 764.61, P2₁/c(#14), a = 13.457(4), b = 11.583(2), c = 18.992(3) Å α = 90, β = 110.11(1)°, Z = 4, V = 2780(1) ų, D_c = 1.827 g/cc, μ (MoKα) = 19.69 cm^?1, F(000) = 1488.00, T = 293 K, R_int = 0.055 for 3094 independent reflections with I>3.00σ(I). The five‐membered heterocyclic ring is nearly planar, with the trichlorophenyl ring at N(2) almost perpendicular to it. However, the seven‐membered ring is not planar, but adopts a twist‐boat conformation.     

[1,5‐Bis(1‐methyl‐1H‐imidazol‐2‐yl­methyl‐κN3)‐1,5‐di­aza­cyclo­octane‐N,N′]chlorocobalt(II) perchlorate

The crystal structure of the title compound, [CoCl‐(C₁₆H₂₆N₆)]ClO₄, consists of discrete [CoCl­(C₁₆­H₂₆N₆)]⁺ cations and perchlorate anions. The five‐coordinate Co^II atom has four nitro­gen donors from the new mesocyclic ligand 1,5‐bis(1‐methyl‐1H‐­imidazol‐2‐ylmethyl)‐1,5‐di­aza­cyclo­octane [Co—N 2.046 (3)–2.214 (4) Å], and a chloride anion at the apical site [Co—Cl 2.3184 (13) Å]. The coordination geometry of the complex is essentially square pyramidal. The mesocyclic ligand takes a boat–chair configuration and the two imidazole pendants are not coplanar. The dihedral angle between the two imidazole planes is 15.97°. An H atom from the 1,5‐diaza­cyclo­octane group effectively blocks the axial coordination site opposite the Cl ligand.     

Bis­(aceto­nitrile‐κN)[(1RS,4RS,8SR,11SR)‐1,4,8,11‐tetra­aza­tetra­decane‐κ4N]copper(II) bis{tetrakis­[3,5‐bis­(tri­fluoro­methyl)­phenyl]­borate} 0.31‐hydrate

The title compound, [Cu(C₂H₃N)₂(C₁₀H₂₄N₄)](C₃₂H₁₂BF₂₄)₂·0.31H₂O, crystallizes as an ionic species with no interactions between the ions. The [Cu^II(cyclam)(MeCN)₂]²⁺ dication (cyclam is 1,4,8,11‐tetra­aza­tetra­decane), located on a 2/m symmetry site, forms as a distorted octahedral species with four Cu—N_cyclam bonds of 2.013 (2) Å and two C—N_MeCN bonds of 2.499 (4) Å. The [B{C₆H₃(CF₃)‐3,5}₄]⁻ anion, located on a twofold axis, is a distorted octahedral species. A small amount of water is present, occupying sites between columns of ions.     

Synthesis and Crystal Structure of Octahydro‐5H,12H‐4,11‐methano‐1H,7H‐bis[1,2,5]oxadiazolo[3,4‐d:3′,4′‐j][1,7,3,9]dioxadiazacyclododecine

The unusual 12‐membered ring compound, octahydro‐5H,12H‐4,11‐methano‐1H,7H‐bis[1,2,5]oxadiazolo[3,4‐d:3′,4′‐j][1,7,3,9]dioxadiazacyclododecine is obtained from the acid catalyzed reaction of 3‐amino‐4‐hydroxymethylfurazan with formaldehyde instead of the expected methylene‐bridged compound, 4,4′‐methylenebis[4,5‐dihydro‐7H‐[1,2,5]oxadiazolo[3,4‐d][1,3]oxazine]. The compound crystallizes in Tetragonal, P4₃2₁2, a = 6.4141(4) Å, b = 6.4141(4) Å, c = 26.525(3) Å, α = 90°, β = 90°, γ = 90°, V = 1091.27(16) ų, Z = 4, dcalc = 1.614 Mg/m³.     

[N,N′‐Bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′](trithiocyanurato‐κ2N,S)zinc(II) ethanol solvate

In the crystal structure of the title compound, [N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine‐κ⁴N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐tri­thionato(2−)‐κ²N,S]­zinc(II) ethanol sol­vate, [Zn(C₈H₂₂N₄)₂(C₃HN₃S₃)]·C₂H₆O, the Zn^II atom is octa­hedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a tri­thio­cyanurate(2−) (ttcH²⁻) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds.     

Low‐dimensional compounds containing cyano groups. XII.)copper(II) perchlorate

The title compound, [Cu(C₂N₃)(C₃H₁₀N₂)₂]ClO₄, is made up of [Cu(tn)₂{N(CN)₂}]⁺ complex cations (tn is 1,3‐diamino­propane) and ClO₄⁻ anions. The Cu^II atom is coordinated by four N atoms of two equatorial tn ligands, with an average distance of 2.041 (7) Å, and one nitrile N atom of the dicyanamide anion in an axial position, at a distance of 2.236 (3) Å, in a manner approaching square‐planar coordination geometry. The complex has C_s symmetry, with the mirror plane lying through the central C atoms of both tn ligands and the dca ligand. The ClO₄⁻ anion might be considered as very weakly coordinated in the opposite axial position [Cu—O = 2.705 (3) Å], thus completing the Cu^II coordination to asymmetric elongated octa­hedral (4+1+1*). The Cu atom and the perchlorate anion both lie on mirror planes.     

π‐Complexes of Copper(I) with Terminal Alkynes. Synthesis and Crystal Structure of [(HC≡CCH2NH3)(Cu2Br3)] π‐Complex

Crystals of the zwitterionic copper(I) π‐complex [(HC≡CCH₂NH₃)Cu₂Br₃] have been synthesized by interaction of CuBr with [HC≡CCH₂NH₃]Br in aqueous solution (pH < 1) and X‐ray studied. The crystals are monoclinic: space group P2₁/n, a = 6.722(4), b = 12.818(8), c = 9.907(3) Å, β = 100.25(4)°, V = 840.0(8) ų, Z = 4, R = 0.0592 for 3015 reflections. The crystal structure of the π‐complex contains isolated [(HC≡CCH₂NH₃)⁺(Cu₂Br₃)^?]₂ units which are incorporated into a framework by strong hydrogen N–H···Br and C≡C–H···Br bonds. The length of π‐coordinated propargylammonium C≡C bond is equal 1.216(8) Å and Cu(I)–(C≡C) distance equals 1.958(5) Å.