Low‐dimensional compounds containing cyano groups. XVI. (Dicyanamido‐κN1)bis(1,10‐phenanthroline‐κ2N,N′)copper(II) tetrafluoridoborate

The title compound, [Cu{N(CN)₂}(C₁₂H₈N₂)₂]BF₄, was prepared as part of our study of the shape of coordination polyhedra in five‐coordinated copper(II) complexes. Single‐crystal X‐ray analysis reveals that the structure consists of [Cu{N(CN)₂}(phen)₂]⁺ cations (phen is 1,10‐phenanthroline) and BF₄⁻ anions. The Cu centre is five‐coordinated in a distorted trigonal bipyramidal manner by four N atoms of two phen ligands and one N atom of a dicyanamide anion, which is coordinated in the equatorial plane at a distance of 1.996 (2) Å. The two axial Cu—N_phen distances have similar values [average 1.994 (6) Å] and are shorter than the two equatorial Cu—N_phen bonds [average 2.09 (6) Å]. This work demonstrates the effect of ligand rigidity on the shape of coordination polyhedra in five‐coordinated copper(II) complexes.     

Spectral and Structural Studies of the Copper(II) Complexes of 3, 4‐Hexanedione Bis(3‐azacyclothiosemicarbazones)

Copper(II) complexes of 3, 4‐hexanedione bis(piperidyl‐ and bis(hexamethyleneiminylthiosemicarbazone), H₂Hxpip and H₂Hxhexim, respectively, have been prepared and studied spectroscopically. The bis(thiosemicarbazones) have been characterized by their melting points, as well as IR, electronic and ¹H NMR spectra. Upon formation of their copper(II) complexes, loss of the hydrazinic hydrogen atoms occurs, and the ligands coordinate as dianionic, tetradentate N₂S₂ ligands. The crystal structures of H₂Hxpip, its 4‐coordinate copper(II) complex, [Cu(Hxpip)], and the related [Cu(Hxhexim)] have been determined by single crystal x‐ray diffraction. The nature of the four‐coordinate copper(II) complexes have also been characterized by ESR, IR, and electronic spectroscopy, as well as magnetic moments and elemental analyses.     

Influence of Cu(II) Ions on the Mechanism of the Ring Transformation of S‐(2‐Oxotetrahydrofuran‐3‐yl)‐N‐(4‐methoxyphenyl)isothiouronium Bromide

The effect of additional Cu(II) ions on the rate of transformation of S‐(2‐oxotetrahydrofuran‐3‐yl)‐N‐(4‐methoxyphenyl)isothiouronium bromide ( 1 ) into 5‐(2‐hydroxyethyl)‐2‐[(4‐methoxyphenyl)imino]‐1,3‐thiazolidin‐4‐one ( 2 ) has been studied in aqueous buffer solutions. The reaction acceleration in acetate buffers is caused by the formation of a relatively weakly bonded complex (K_c = 600 L·mol^?1) of substrate with copper(II) acetate in which the Cu(II) ion acts as a Lewis acid coordinating the carbonyl oxygen and facilitating the intramolecular attack, leading to the formation of intermediate T^±. The formation of the complex of copper(II) acetate with free isothiourea in the fast preequilibrium (K_c) is followed by the rate‐limiting transformation (k_Cu) of this complex. At the high concentrations of the acetate anions, the reaction is retarded by the competitive reaction of these ions with copper(II) acetate to give an unreactive complex [Cu(OAc)₄]^2?_. The influence of Cu(II) ions on the stability of reaction intermediates and the leaving group ability of the alkoxide‐leaving group compared to the Cu(II)‐uncatalyzed reaction is also discussed.     

catena‐Poly[[[2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­iminomethyl)phenolato]copper(II)]‐μ‐thio­cyanato]

The title complex, [Cu(C₁₃H₉Cl₂N₂O)(NCS)]_n, is a novel thio­cyanate‐bridged polynuclear copper(II) compound. The Cu^II atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base ligand and one terminal N atom of a bridging thio­cyanate ligand defining the basal plane, and one terminal S atom of another bridging thio­cyanate ligand occupying the axial position. The [2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­imino­methyl)­phenolato]­copper(II) moieties are linked by the bridging thio­cyanate ligands, forming polymeric chains running along the a axis.     

Copper(II) Halide Complexes with 1‐tert‐Butyl‐1H‐1,2,4‐triazole and 1‐tert‐Butyl‐1H‐tetrazole

1‐tert‐Butyl‐1H‐1,2,4‐triazole (tbtr) was found to react with copper(II) chloride or bromide to give the complexes [Cu(tbtr)₂X₂]_n and [Cu(tbtr)₄X₂] (X = Cl, Br). 1‐tert‐Butyl‐1H‐tetrazole (tbtt) reacts with copper(II) bromide resulting in the formation of the complex [Cu₃(tbtt)₆Br₆]. The obtained crystalline complexes as well as free ligand tbtr were characterized by elemental analysis, IR spectroscopy, thermal and X‐ray analyses. For free ligand tbtr, ¹H NMR and ¹³C NMR spectra were also recorded. In all the complexes, tbtr and tbtt act as monodentate ligands coordinated by Cu^II cations via the heteroring N⁴ atoms. The triazole complexes [Cu(tbtr)₂Cl₂]_n and [Cu(tbtr)₂Br₂]_n are isotypic, being 1D coordination polymers, formed at the expense of single halide bridges between neighboring copper(II) cations. The isotypic complexes [Cu(tbtr)₄Cl₂] and [Cu(tbtr)₄Br₂] reveal mononuclear centrosymmetric structure, with octahedral coordination of Cu^II cations. The tetrazole compound [Cu₃(tbtt)₆Br₆] is a linear trinuclear complex, in which neighboring copper(II) cations are linked by single bromide bridges.     

Four‐ and five‐coordinate copper(II) complexes with N‐(4,4‐diphenyl‐5‐oxo‐4,5‐dihydro‐1H‐imidazol‐2‐yl)glycine

The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂]·2C₃H₇NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂(H₂O)]·2C₃H₇NO, (II). In (I), the Cu^II ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the Cu^II ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks.     

Synthesis and coordination chemistry of new tetradentate N2S2 donor Schiff-base ligand ca2-dapte: Mononuclear and dinuclear copper(I) complexes [Cu(ca2dapte)]ClO4 and [{Cu(PPh3)(X)}2(ca2dapte)] (X = I and Br)

A mononuclear copper(I) complex, [Cu(ca₂dapte)]ClO₄ (1), and two dinuclear copper(I) complexes, [{Cu(PPh₃)(X)}₂(ca₂dapte)] (X = I (2) and Br (3)), of a new tetradentate N₂S₂ donor Schiff-base ligand ca₂dapte have been prepared (ca₂dapte = N,N′-bis(trans-cinnamaldehyde)-1,2-di(o-iminophenylthio)ethane). These compounds have been characterized by elemental analyses (CHN), FT-IR, UV–Vis and ¹H NMR spectroscopy. The crystal structures of these copper(I) complexes have been determined by single-crystal X-ray diffraction. The coordination geometry around Cu(I) centers in these complexes is a distorted tetrahedron. The ca₂dapte is coordinated to Cu(I) as a tetradentate ligand in 1, while it acts as a bis-bidentate bridging ligand in 2 and 3.     

A lariat‐functionalized copper(II) di­imine–dioxime complex

The dimeric title copper(II) complex, diaqua‐1κO,2κO‐bis[3,9‐dimethyl‐6‐(2‐pyridyl­methyl)‐4,8‐di­aza­undeca‐3,8‐di­ene‐2,10‐dione dioximato(1?)]‐1k⁴N²,N⁴,N⁸,N¹⁰;1:2κ⁵O²:N²,N⁴,N⁸,N¹⁰‐dicopper(II) diperchlorate, [Cu₂(C₁₇H₂₄N₅O₂)₂](ClO₄)₂, crys­tallizes with one Cu atom in a square‐pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water mol­ecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) Å] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water mol­ecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to Cu^II.     

catena‐Poly[[{4‐bromo‐2‐[2‐(dimethyl­amino)ethyl­imino­methyl]­phenol­ato}­copper(II)]‐μ‐azido]

The title complex, [Cu(C₁₁H₁₄BrN₂O)(N₃)]_n, is an inter­esting azide‐bridged polynuclear copper(II) compound. The Cu^II atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base and one terminal N atom of a bridging azide ligand defining the basal plane, and another terminal N atom of another bridging azide ligand occupying the axial position. The {4‐bromo‐2‐[2‐(dimethyl­amino)ethyl­imino­meth­yl]phenolato}copper(II) moieties are linked by the bridging azide ligands, forming polymeric chains running along the b axis. Adjacent chains are further linked by weak Br⋯Br inter­actions into a sheet.     

Syntheses,Spectroscopic, Structural,Fluorescent and Thermal Properties of Bis(saccharinato)copper(II) Complexes with two Bis(pyridylamine) Ligands

Two new copper(II) complexes of saccharinate (sac) with bis(2‐pyridylmethyl)amine (bpma) and N,N′‐bis[1‐(pyridin‐2‐yl)ethylidene]ethane‐1,2‐diamine (bapen), [Cu(bpma)(sac)₂] · H₂O ( 1 ) and [Cu(bapen)(sac)₂] ( 2 ), were synthesized and characterized by elemental analysis, TG‐DTA, X‐ray diffraction, and UV/Vis and IR spectroscopy, respectively. In 1 , the copper(II) ion is coordinated by two N‐bonded sac ligands, and three nitrogen atoms of bpma, in a distorted square‐pyramidal coordination arrangement, whereas the arrangement around the copper ion in 2 is a distorted octahedron with two N‐coordinated sac ligands and a tetradentate bapen ligand. In addition to hydrogen bonding involving the water molecule in 1 , the mononuclear species of 1 and 2 are further connected by weak intermolecular C–H ··· π and C–H ··· O interactions to form a three‐dimensional network. Both complexes are luminescent at room temperature and their emissions seem to be due to ligand‐based π–π* transitions.     

A novel thio­cyanate‐bridged one‐dimensional chain complex: [Cu(NCS)2(Hambi)] (Hambi is 2‐amino­methyl‐1H‐benz­imidazole)

Using 2‐amino­methyl‐1H‐benz­imidazole as the ligand, a new thio­cyanate‐bridged copper(II) complex, namely bis(2‐aminomethyl‐1H‐benz­imidazole‐κ²N²,N³)­di­thio­cyanato­copper(II),[Cu(NCS)₂(C₈H₉N₃)], has been synthesized and structurally characterized. The Cu atom is five‐coordinated and exhibits a distorted square‐pyramidal geometry. The thio­cyanate ions (NCS⁻) act as either bridging or terminal ligands. The bridging NCS⁻ ligands connect neighboring Cu atoms, constructing chains, while the terminal NCS⁻ ligands form hydrogen bonds with amine H atoms, leading to a complicated network.     

2D Hydrogen Bonded Copper (II) Coordination Network Constructed by the Combination of Flexible and Rigid Ligands

Complex [Cu(2,2′‐bipy)(H₂L¹)] (ClO₄)₂(1) has been synthesized by the self‐assembly of Cu(ClO₄)₂ with a rigid ligand 2,2′‐bipyridine and a flexible potential tetradentate ligand N, N'‐bis(hydroxyethyl)ethylenediamine (H₂L¹). Crystal analyses reveal that the potentially tetradentate ligand H₂L¹ acts in a tridentate mode by the coordination of one hydroxyl oxygen atom and two amino nitrogen atoms. The Cu(II) atom coordinates additionally with two bipyridyl nitrogen atoms, giving a distorted square pyramidal geometry. Each complex molecule is connected with four surrounding molecules along the ac plane by multiple hydrogen bonds, leading to 2D sheets constituted with 0.7874 nm × 1.0891 nm metallomacrocyclic rectangles. Each vertex of the rectangle is occupied by a copper atom, and the four sides are comprised of multiple hydrogen bonds.     

Supramolecular interactions in a copper(II) 4′‐(4‐bromophenyl)‐2,2′:6′,2′′‐terpyridine complex

The title compound, [4′‐(4‐bromophenyl)‐2,2′:6′,2′′‐terpyridine]chlorido(trifluoromethanesulfonato)copper(II), [Cu(CF₃O₃S)Cl(C₂₁H₁₄BrN₃)], is a new copper complex containing a polypyridyl‐based ligand. The Cu^II centre is five‐coordinated in a square‐pyramidal manner by one substituted 2,2′:6′,2′′‐terpyridine ligand, one chloride ligand and a coordinated trifluoromethanesulfonate anion. The Cu—N bond lengths differ by 0.1 Å for the peripheral and central pyridine rings [2.032 (2) (mean) and 1.9345 (15) Å, respectively]. The presence of the trifluoromethanesulfonate anion coordinated to the metal centre allows Br...F halogen–halogen interactions, giving rise to the formation of a dimer about an inversion centre. This work also demonstrates that the rigidity of the ligand allows the formation of other types of nonclassical interactions (C—H...Cl and C—H...O), yielding a three‐dimensional network.     

How Does a Coordinated Radical Ligand Affect the Spin Crossover Properties in an Octahedral Iron(II) Complex?

The influence of a coordinated π‐radical on the spin crossover properties of an octahedral iron(II) complex was investigated by preparing and isolating the iron(II) complex containing the tetradentate N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane and the radical anion of N,N′‐diphenyl‐acenaphtene‐1,2‐diimine as ligands. This spin crossover complex was obtained by a reduction of the corresponding low‐spin iron(II) complex with the neutral diimine ligand, demonstrating that the reduction of the strong π‐acceptor ligand is accompanied by a decrease in the ligand field strength. Characterization of the iron(II) radical complex by structural, magnetochemical, and spectroscopic methods revealed that spin crossover equilibrium occurs above 240 K between an S=1/2 ground state and an S=3/2 excited spin state. The possible origins of the fast spin interconversion observed for this complex are discussed.     

catena‐Poly[[(2,2′‐diamino‐4,4′‐bithiazole){μ3‐cis‐N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidato(3−)}dicopper(II)] nitrate 0.6‐hydrate]

The title complex, {[Cu₂(C₁₄H₁₆N₃O₄)(C₆H₆N₄S₂)]NO₃·0.6H₂O}_n, is a one‐dimensional copper(II) coordination polymer bridged by cis‐oxamide and carboxylate groups. The asymmetric unit is composed of a dinuclear copper(II) cation, [Cu₂(dmapob)(dabt)]⁺ {dmapob is N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidate and dabt is 2,2′‐diamino‐4,4′‐bithiazole}, one nitrate anion and one partially occupied site for a solvent water molecule. The two Cu^II ions are located in square‐planar and square‐pyramidal coordination environments, respectively. The separations of the Cu atoms bridged by oxamide and carboxylate groups are 5.2053 (3) and 5.0971 (4) Å, respectively. The complex chains are linked by classical hydrogen bonds to form a layer and then assembled by π–π stacking interactions into a three‐dimensional network. The influence of the terminal ligand on the structure of the complex is discussed.     

A novel three‐dimensional copper(I) coordination polymer constructed from a copper–bromide net and nicotinic acid ligands

The title compound, poly[μ₃‐bromido‐(pyridine‐3‐carboxylato‐κN)copper(I)], [CuBr(C₆H₅NO₂)]_n, is a novel coordination polymer based on a copper–bromide net and nicotinic acid ligands. The asymmetric unit contains one copper(I) ion, one bromide ligand and one nicotinic acid ligand, all on general positions. The Cu^I atom is tetrahedral and coordinated by three bridging Br atoms and the N atom from the nicotinic acid ligand. The Cu–Br units form alternating six‐membered chair‐patterned rings in net‐like layers. The attached nicotinic acid units point alternately up and down. The layers are assembled into a three‐dimensional network via intermolecular O—H...O and C—H...Br hydrogen‐bonding interactions.     

[N‐(Carboxyl­ato­methyl)­aspartato(3–)](ethyl­enedi­amine)­cobalt(III) trihydrate

The mononuclear title complex, [Co(C₆H₆NO₆)(C₂H₈N₂)]·3H₂O, contains an octahedrally coordinated Co^III atom. The N‐(carboxy­methyl)­aspartate moiety is coordinated as a tetradentate ligand, providing an OONO‐donor set and forming two trans five‐membered chelate rings and one six‐membered chelate ring. A seven‐membered chelate ring is also formed, which consists of part of the six‐membered chelate ring and part of one of the five‐membered chelate rings. The crystal structure of the complex is stabilized by hydrogen bonds with three water mol­ecules.     

An unusually flexible expanded hexaamine cage and its Cu(II) complexes: variable coordination modes and incomplete encapsulation

The bicyclic hexaamine "cage" ligand Me(8)tricosaneN(6) (1,5,5,9,13,13,20,20-octamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane) is capable of encapsulating octahedral metal ions, yet its expanded cavity allows the complexed metal to adopt a variety of geometries comprising either hexadentate or pentadentate coordination of the ligand. When complexed to Cu(II) the lability of the metal results in a dynamic equilibrium in solution between hexadentate- and pentadentate-coordinated complexes of Me(8)tricosaneN(6). Both [Cu(Me(8)tricosaneN(6))](ClO(4))(2) (6-coordinate) and [Cu(Me(8)tricosaneN(6))](S(2)O(6)) (5-coordinate) have been characterized structurally. In weak acid (pH 1) a singly protonated complex [Cu(HMe(8)tricosaneN(6))](3+) has been isolated that finds the ligand binding as a pentadentate with the uncoordinated amine being protonated. vis-NIR and electron paramagnetic resonance (EPR) spectroscopy show that the predominant solution structure of [Cu(Me(8)tricosaneN(6))](2+) at neutral pH comprises a five-coordinate, square pyramidal complex. Cyclic voltammetry of the square pyramidal [Cu(Me(8)tricosaneN(6))](2+) complex reveals a reversible Cu(II/I) couple. All of these structural, spectroscopic, and electrochemical features contrast with the smaller cavity and well studied "sarcophagine" (sar, 3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) Cu(II) complexes which are invariably hexadentate coordinated in neutral solution and cannot stabilize a Cu(I) form.     

Synthesis,spectral, thermal and structural characterization of {[Cu(H2O)3][Cu(MAL)2] · 2H2O}∞ and [Cu(MAL)(TEA)] · H2O (MAL = malonate and TEA = triethanolamine)

A polymeric malonato-bridged copper(II) complex, {[Cu(H₂O)₃][Cu(MAL)₂]· 2H₂O}, and a mononuclear malonato-copper(II) complex with triethanolamine, [Cu(MAL)(TEA)]·H₂O, have been prepared and characterized by elemental analyses, i.r., u.v.–vis, magnetic measurements and single crystal X-ray diffraction. The polymeric complex consists of one-dimensional chains containing the MAL bridged [Cu(H₂O)₃]²⁺ and [Cu(MAL)₂]^2– ions and each MAL ligand simultaneously exhibits chelating bidentate (at one copper atom) and bridging (at the adjacent copper atom) coordination modes. The intrachain Cu1...Cu2 separation is 4.963 Å and the polymeric complex exhibits antiferromagnetic behaviour. In the mononuclear complex, the copper(II) ion is octahedrally coordinated by one bidentate MAL and one tetradentate neutral TEA ligands. The i.r. spectra and thermal decompositions of both complexes are described.