Synthesis, crystal structure, spectroscopic and magnetic properties of copper(II) complexes with 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine (PyTT)

The copper(II) complexes [Cu(PyTT)₂(H₂O)](NO₃)₂ (A) and [CuCl₂(μ-PyTT)₂CuCl(H₂O)]Cl · 3H₂O (B) were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, UV-Vis-NIR diffuse reflectance and magnetic susceptibility measurements. In the mononuclear compound A the copper ion is in a distorted square pyramidal geometry, with the equatorial plane formed by two thiazoline nitrogen atoms, one imino nitrogen atom and one water molecule, whereas the axial site is occupied by one imino nitrogen atom. The compound B is dinuclear and both Cu(II) centres present environments that can be described as slightly distorted square pyramidal geometries. The observed molar magnetic susceptibility for A (μ=2.13 BM) allows to exclude metal-metal interactions, supporting a monomeric structural formulation for this compound. In compound B, magnetic susceptibility measurements in the temperature range 6.2-288 K show an intradimer antiferromagnetic interaction (J=−11.8 cm⁻¹).     

Effects of a derivative thiazoline/thiazolidine azine ligand and its cadmium complexes on phagocytic activity by human neutrophils

The complexes [CdCl₂(ATHTd)] (1) and [Cd(NO₃)₂(ATHTd)(H₂O)] (2) [ATHTd = N-(2-acetyl-2-thiazoline)-N′-(2-thiazolidin-2-one) azine] have been synthesized and characterized by a variety of physico-chemical techniques. X-ray data indicate that in 1 the coordination geometry around the metal ion can be considered a distorted square pyramid with cadmium(II) cation coordinated to one tridentate ATHTd ligand and two chloride ligands. In the case of 2, the coordination environment around Cd(II) atom approximates to a distorted pentagonal bipyramid with the cadmium atom bonded to one tridentate ATHTd ligand, one water molecule, one monodentate nitrate ligand and one bidentate nitrate ligand. The structure of ATHTd in the complexes presents an amino-2-thiazoline form instead of the iminothiazolidine one observed in free ATHTd. Likewise, the degree of rotation of the thiazoline rings around the C(1)-C(4) and C(6)-N(3) bonds has changed in complexes, which permit the coordination through thiazolinic nitrogen atoms. Besides, we study the phagocytic function in human neutrophils treated with ligand ATHTd, CdCl₂, Cd(NO₃)₂ and complexes 1 and 2. From the obtained results it can be concluded that the complexes 1 and 2 increase the phagocytic capacity of neutrophils with respect to Cd(II) salts and ATHTd.     

Coordination compounds of Cd(II) with several bidentate-NN′ and tridentate-NN′N nitrogen donor ligands. Cd NMR studies of monomeric compounds containing nitrogen donor atoms

Reaction of CdCl₂ with N-alkylaminopyrazole ligands 1-[(2-ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[(2-(tert-butylamino)ethyl)]-3,5-dimethylpyrazole (deat), bis-[(3,5-dimethylpyrazolyl)methyl]ethylamine (bdmae), and bis-[(3,5-dimethylpyrazolyl)ethyl]ethylamine (ddae) in absolute ethanol yields [CdCl₂(NN′)] (NN′ = deae (1), deat (2)), [CdCl₂(bdmae)] (3), and [CdCl(ddae)]₂[CdCl₄] (4). The Cd(II) complexes have been characterised by elemental analyses, conductivity measurements, IR, ¹H, ¹³C{¹H} and ¹¹³Cd NMR spectroscopies, and X-ray diffraction methods. ¹H and ¹¹³Cd NMR experiments at variable temperature for 3 and 4 show that dynamic processes are taking place in solution. We report the measurements of ¹¹³Cd NMR chemical shift data for complexes 1-4 in solution. X-ray crystal structures for complexes 2 and 3 have been determined. The Cd(II) is coordinated to the deat ligand, in 2, by one nitrogen atom of the pyrazolyl group and one nitrogen atom of the amine. It finishes a tetrahedral geometry with two chlorine atoms. The bdmae ligand is linked to Cd(II), in 3, by two nitrogens atoms of the pyrazolyl groups and one amine nitrogen, along with two chlorine atoms, in a distorted trigonal bipyramidal geometry.     

Effect of pendant arm length and nitrogen donor disposition on the topology of luminescent cadmium phenylenedicarboxylate coordination polymers with bis(pyridylmethyl)piperazine co-ligands

Hydrothermal synthesis has afforded divalent cadmium coordination polymers containing bis(pyridylmethyl)piperazine (bpmp) tethers and either phenylenediacetate (phda) or phenylenedipropionate (phdp) ligands. {[Cd(1,4-phda)(4-bpmp)]·1.5H₂O}_n (1) displays a (4,4)-grid layered structure based on 4-connected {Cd₂O₂} dimeric units. Extension of the pendant arms generated {[Cd(1,4-phdp)(H4-bpmp)](ClO₄)·3.5H₂O}_n (2, phdp = phenylenedipropionate), which possesses a rare (3,6) 2D trigonal lattice based on 6-connected {Cd₂O₂} dimers. Changing the nitrogen donor atom disposition by using 3-bpmp as the nitrogen co-ligand yielded [Cd(1,4-phdp)(3-bpmp)(H₂O)]_n (3), which crystallizes in a 3-fold interpenetrated achiral diamondoid lattice. [Cd(1,3-phda)(4-bpmp)]_n (4) adopts a very similar structure to that of 1. Complexes 1-4 undergo blue-violet luminescence upon exposure to ultraviolet radiation.     

Synthesis and crystal structure determination of 0D-, 1D- and 3D-metal compounds of 4-(pyrid-4-yl)-1,2,4-triazole with zinc(II) and cadmium(II)

The potentially tritopic bridging ligand 4-(pyrid-4-yl)-1,2,4-triazole (pytz) reacts with cadmium(II) nitrate tetrahydrate, Cd(NO₃)₂·4H₂O and sodium dicyanamide (Na-dca) to form the molecular complex [Cd(dca)₂(κN_py-pytz)₂(H₂O)₂] (1). The cadmium atom lies on a center of inversion and is coordinated in a slightly distorted octahedral geometry by the trans-oriented pytz ligands, dicyanamide anions and aqua ligands. The pytz ligand coordinates through the N_pyridin atom to the metal atom. The molecular complexes are connected to a 3D supramolecular network by O-H···N_dca and O-H···N_triazole hydrogen bonds. From zinc(II) bromide and pytz the compound 1D-[ZnBr₂(μ-κN_py,N_tz-pytz)] (2) is obtained where the pytz-ligand bridges between the tetracoordinated zinc(II) atoms through coordination of its N_pyridine- and N_triazole-atoms. Adjacent chains are connected through C-H···Br and C-H···N hydrogen bonds to form a 3D supramolecular structure. Single crystals of 2 crystallize homochiral in the non-centrosymmetric space group P2₁2₁2₁. The origin of the homochirality is the formation of hydrogen-bonded helices around the 2₁ screw axes with the same sense of rotation (left-handed or M in the investigated crystal). Cd(NO₃)₂·4H₂O, pytz and sodium thiocyanate (NaSCN) give the framework 3D-[Cd(μ-SCN)₂(μ-κN_py,N_tz-pytz)] (3). Parallel layers of 2D-{Cd(μ-SCN)₂}-nets with distorted (6,3)-net topology are assembled by the bridging pytz-ligands into a 3D-structure. The pytz-ligand bridges between two cadmium atoms by N_pyridine- and N_triazole-coordination.     

Synthesis, structures and properties of dinuclear cadmium(II) complexes based on polybenzimidazole binucleating ligands

Three novel cadmium(II) complexes [Cd₂(tbpo)(O₂CC₆H₄-p-NO₂)₂]ClO₄·3CH₃OH (1) [Cd₂(bbap)(O₂CC₆H₄-p-NO₂)₂]ClO₄·4.5CH₃OH·0.75H₂O (2) and [Cd(ntb)(O₂CC₆H₄-p-NO₂)]ClO₄·4CH₃OH (3) have been synthesized and characterized by IR, elemental analysis, ¹H NMR and X-ray crystallography, where tbpo⁻ and bbap⁻ are anions of N,N,N′,N′-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane and 2,6-bis[bis(2-benzimidazolylmethyl)aminomethyl]-4-methylphenol, respectively; ntb is tris(2-benzimidazolymethyl)amine. Complexes 1 and 2 contain μ-phenolate-bridged and μ-alkoxo-bridged dicadmium(II) cores with the Cd1?Cd2 separation of 3.671 Å for complex 1 and 3.718 Å for 2. One of the 4-nitrobenzoate anions bridged the two cadmium(II) ions in syn-anti mode through its carboxylate group, the other 4-nitrobenzoate is only coordinated with Cd2 in bidentate chelating mode. The two central cadmium(II) atoms are in trigonal bipyramidal and pentagonal bipyramidal geometry. In complex 3, the cadmium(II) atom is coordinated with four nitrogen atoms of ntb and one carboxylate oxygen atom of 4-nitrobenzoate in distorted trigonal bipyramidal geometry. Experiment shows that there is a higher affinity of 4-nitrobenzoate anion as coligand with the dinuclear [Cd₂(tbpo)]³⁺ and [Cd₂(bbap)]³⁺ cores than that with the mononuclear [Cd(ntb)]²⁺ core.     

Synthesis, structure and bonding of cadmium(II) thiocyanate systems featuring nitrogen based ligands of different denticity

Complexes catena-[di(4-amino-pyridine)di(μ-S,N-thiocyanato)cadmium(II)], , catena-[{(1-pyridine-2-yl-ethylene)-hydrazine}di(μ-S,N-thiocyanato)cadmium(II)], , and di-μ-S,N-thiocyanatobis{(N,N-diethyl-N′-(1-pyridine-2-yl-ethylidene)-ethane-1,2-diamine)(N-thiocyanato)cadmium(II)}, [Cd(NCS)(μ-SCN)(L³)]₂ (3) have been synthesized by reacting cadmium acetate/NH₄SCN with 4-amino-pyridine (L¹), C₅H₄N-C(CH₃)NNH₂ (L²), and C₅H₄N-C(CH₃)N-CH₂-CH₂-N(C₂H₅)₂ (L³), respectively, in methanol. Characterization by single-crystal X-ray crystallography shows that in compounds 1 and 2 the cadmium atoms have a 4N2S-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric chains. Compound 3 is a centrosymmetric dimeric complex, with the cadmium atom pseudo octahedrally surrounded by a 5N1S coordination sphere. In compound 1 the crystal packing is controlled mainly by interchain N-H?N and C-H?π interactions between the aminopyridine moieties, whereas in complexes 2 and 3 π-stacking interactions between the pyridyl planes stabilize the interchain or intermolecular packing, respectively. Thiocyanate and pyridylimine chelation to metal center is also scrutinized with EHMO analysis.     

Chemistry of molecular and supramolecular structures of vanadium(IV) and dioxygen-bridged V(V) complexes incorporating tridentate hydrazone ligands

Four hydrazone ligands: 2-benzoylpyridine benzoyl hydrazone (HBPB), di-2-pyridyl ketone nicotinoyl hydrazone (HDKN), quinoline-2-carbaldehyde benzoyl hydrazone (HQCB), and quinoline-2-carbaldehyde nicotinoyl hydrazone (HQCN) and four of their complexes with vanadyl salts have been synthesized and characterized. Single crystals of HBPB and complexes [VO(BPB)(μ₂-O)]₂ (1) and [VO(DKN)(μ₂-O)]₂·½H₂O (2) were isolated and characterized by X-ray crystallography. Each of the complexes exhibits a binuclear structure where two vanadium(V) atoms are bridged by two oxygen atoms to form distorted octahedral structures within cis-N₂O₄ donor sets. In most complexes, the uninegative anions function as tridentate ligands, coordinating through the pyridyl- and azomethine-nitrogen atoms and enolic oxygen whereas in complex [VO(HQCN)(SO₄)]SO₄·4H₂O (4) the ligand is coordinated in the keto form. Complexes [VO(QCB)(OMe)]·1.5H₂O (3) and 4 are found to be EPR active and showed well-resolved axial anisotropy with two sets of eight line pattern.     

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4−n] (n=3 and 4) and [Cd2Cl2(SC{O}Me)4]

We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)_nCl_4−n]²⁻ (n=3, 4) and [Cd₂Cl₂(SC{O}Me)₄]²⁻. Complexes of the formula [Ph₄P]₂[M(SC{O}Me)₄] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph₄PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1<2<3 as observed from the SMS angles in the crystal structures. The tendency of monoanionic complexes [Ph₄P][M(SC{O}Me)₃] to react with 1 mole equivalent of Ph₄PCl resulted in complexes of the type [Ph₄P]₂[M(SC{O}Me)₃Cl] (M=Cd(II) (4) or Hg(II) (5)). In the structures of 4 and 5, three sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the metal centers. However, in a 4:2:2 or 2:1:2 molar reaction of Me{O}CS⁻ with CdCl₂ and Ph₄PCl in aqueous medium resulted in a chloro bridged dimer, [Ph₄P]₂[Cd₂(μ-Cl)₂(SC{O}Me)₄] (6) as determined by X-ray crystallography.     

Syntheses, stereochemistry, reactivity, and some properties of sulfur-bridged cobalt(III)-cadmium(II) polynuclear complexes derived from mononuclear cobalt(III) complex with d-penicillaminate

A reaction of the octahedral bidentate metalloligand, trans(N)-[Co(d-pen)₂]⁻ (d-pen=d-penicillaminate) with Cd(NO₃)₂ or Cd(ClO₄)₂ gave a novel S-bridged trinuclear complex, [Cd(H₂O){Co(d-pen)₂}₂] (1). In this complex molecule, the central Cd atom is surrounded by four S atoms from two [Co(d-pen)₂]⁻ units and one O atom of a H₂O molecule to form a distorted five-coordinated geometry. Each of two terminal [Co(d-pen)₂]⁻ units takes an approximately octahedral geometry and has a similar trans(N) geometry to that of the starting material. On the other hand, the reaction of trans(N)-[Co(d-pen)₂]⁻ with CdCl₂ in the molar ratio of 1:1 gave an S-bridged dinuclear complex, [CdCl{Co(d-pen)₂}(H₂O)_m]·nH₂O (m+n=4) (2). The reactivity of trans(N)-[Co(d-pen)₂]⁻ toward CdCl₂ is significantly influenced by the ratio of two components, and the formation of a similar trinuclear species to 1 is also suggested under the condition with excess amount of trans(N)-[Co(d-pen)₂]⁻. Some spectrochemical properties of these complexes are also discussed in relation to their structures.     

Structural, molecular mechanics, and DFT study of cadmium(II) in its crown ether complexes with axially coordinated ligands, and of the binding of thiocyanate to cadmium(II)

The role of relativistic effects (RE) in the structures of Cd(II) complexes with crown ethers, and the reason the ‘soft’ Cd(II) strongly prefers to bind to SCN⁻ through N, are considered. The synthesis and structures of [Cd(18-crown-6)(thiourea)₂] (ClO₄)₂.18-crown-6 (1) and [Cd(Cy₂-18-crown-6)(NCS)₂] (2) are reported. (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; Cy₂-18-crown-6 = cis-anti-cis-2,5,8,15,18,21-hexaoxatricylo[20.4.0.0(9,14)]hexacosane). In 1 Cd is coordinated in the plane of the crown which has close to D_3d symmetry, with long Cd-O bonds averaging 2.688 Å. The two thiourea molecules form relatively short Cd-S bonds that average 2.468 Å, with an S-Cd-S angle of 164.30°. This structure conforms with the idea that Cd(II) can adopt a near-linear structure involving two covalently-bound donor atoms (the S-donors) with short Cd-S bonds, which resembles gas-phase structures for species such as CdCl₂. The structure of 2 is similar, with the two SCN⁻ ligands N-bonded to Cd, with short Cd-N bonds of 2.106 Å, and N-Cd-N angle of 180°. The crown in 2 forms long Cd-O bonds that average 2.698 Å. Molecular mechanics calculations suggest that a main reason Cd(II) prefers to bind to SCN⁻ through N is that when bound through S, the small Cd-S-C angle, which is typically close to 100°, brings the ligand into close contact with other ligands present, and causes steric destabilization. In contrast, the Cd-N-C angles for SCN⁻ coordinated through N are much larger, being 171.4° in 2, which keeps the SCN⁻ groups well clear of the crown ether. DFT (density functional theory) calculations are used to generate the structures of [Cd(18-crown-6)(H₂O)₂]²⁺ (3) and [Cd(18-crown-6)Cl₂] (4). In 3, the Cd(II) is bound to only three O-donors of the macrocycle, with Cd-O bonds averaging 2.465 Å. The coordinated waters form an O-Cd-O angle of 139.47°, with Cd-O bonds of 2.295 Å. In contrast, for 4, the Cd is placed centrally in the cavity of the D_3d symmetry crown, with long Cd-O bonds averaging 2.906 Å. The Cl groups form a Cl-Cd-Cl angle of 180°, with short Cd-Cl bonds of 2.412 Å. With ionically bound groups on the axial sites of[Cd(18-crown-6)X₂] complexes, such as with X = H₂O in 3, the Cd(II) does not adopt linear geometry involving the two X groups, with long Cd-O bonds to the O-donors of the macrocycle. With covalently-bound X = Cl in 4, short Cd-Cl bonds and a linear [Cl-Cd-Cl] unit results, with long Cd-O bonds to the crown ether.     

Cyclometalated ruthenium(II) complexes of benzo[h]quinoline (bzqH)[Ru(bzq)(NCMe)4], [Ru(bzq)(LL)(NCMe)2], and [Ru(bzq)(LL)2] (LL = bpy, phen)

Cyclometalation of benzo[h]quinoline (bzqH) by [RuCl(μ-Cl)(η⁶-C₆H₆)]₂ in acetonitrile occurs in a similar way to that of 2-phenylpyridine (phpyH) to afford [Ru(bzq)(MeCN)₄]PF₆ (3) in 52% yield. The properties of 3 containing ‘non-flexible’ benzo[h]quinoline were compared with the corresponding [Ru(phpy)(MeCN)₄]PF₆ (1) complex with ‘flexible’ 2-phenylpyridine. The [Ru(phpy)(MeCN)₄]PF₆ complex is known to react in MeCN solvent with ‘non-flexible’ diimine 1,10-phenanthroline to form [Ru(phpy)(phen)(MeCN)₂]PF₆, being unreactive toward ‘flexible’ 2,2′-bipyridine under the same conditions. In contrast, complex 3 reacts both with phen and bpy in MeCN to form [Ru(bzq)(LL)(MeCN)₂]PF₆ {LL = bpy (4) and phen (5)}. Similar reaction of 3 in methanol results in the substitution of all four MeCN ligands to form [Ru(bzq)(LL)₂]PF₆ {LL = bpy (6) and phen (7)}. Photosolvolysis of 4 and 5 in MeOH occurs similarly to afford [Ru(bzq)(LL)(MeCN)(MeOH)]PF₆ as a major product. This contrasts with the behavior of [Ru(phpy)(LL)(MeCN)₂]PF₆, which lose one and two MeCN ligands for LL = bpy and phen, respectively. The results reported demonstrate a profound sensitivity of properties of octahedral compounds to the flexibility of cyclometalated ligand. Analogous to the 2-phenylpyridine counterparts, compounds 4-7 are involved in the electron exchange with reduced active site of glucose oxidase from Aspergillus niger. Structure of complexes 4 and 6 was confirmed by X-ray crystallography.     

The complexes with end-to-end dicyanamide bridges: syntheses, characterization and crystal structures of [Cu(μ1,5-dca)2(phen)]n and [Cd(μ1,5-dca)2(py)2]n (phen=phenanthroline; py=pyridine; dca=dicyanamide, N(CN)2 )

Two new dicyanamide (dicyanamide=[N(CN)₂]⁻, dca) bridged complexes, [Cu(μ_1,5-dca)₂(phen)]_n (1) and [Cd(μ_1,5-dca)₂(py)₂]_n (2) have been synthesized and their structures have been determined by X-ray crystallography diffraction. Complex 1 crystallizes in the monoclinic space group P2(1)/c with a=10.1502(3), b=10.9815(4), c=14.5839(4) Å and Z=4. The adjacent copper atoms are connected by single end-to-end dca bridges to form a chain structure along the b axis. The chains are linked via Cu?N weak interactions to give rise to a 2D layer structure, which furthermore into a 3D structure by the π-π interaction between aromatic rings of adjacent layers. Complex 2 crystallizes in the monoclinic space group C2/m with a=6.6849(10), b=17.476(2), c=13.231(2) Å and Z=4. The cadmium(II) center is six-coordinated with a distorted octahedral geometry, bounded to four N atoms of four dca ligands and two N atoms of two-chelated py ligands. Neighbor Cd(II) atoms are linked by the double end-to-end dca bridges to generate a chain structure, which result in a 2D layer structure through the π-π interactions between the adjacent chains with distances 3.641 Å. EPR and magnetic results of 1 suggest that the complex exhibits a weak ferromagnetic interaction through CuNCNCNCu pathways.     

Preparation and crystal structure of two novel cadmium (II)-trimesates, Cd(HTMA)(NC5H5)2 · 0.5CH3OH · 0.5DMF and Cd(HTMA) · 2H2O

Two novel complexes, Cd(HTMA)(NC₅H₅)₂ · 0.5CH₃OH · 0.5DMF (1) and Cd(HTMA) · 2H₂O (2), of cadmium (II)-trimesates are obtained from slow vapor diffusion and urea hydrolysis, respectively. The Cd(II) centers in the two complexes are bridged by three separate HTMA³⁻ ligands using a same coordination fashion, which contains one monodentate and two chelating bidentate carboxyl groups to form the herringbone-like motif. The herringbone-like motif is further interlinked to construct the two-dimensional Cd(II)-HTMA layer, which is stacked by mutual π-stacking of pyridines for 1 and by hydrogen bond of waters for 2. Thermal stabilities of the two complexes were investigated and the results indicated that Cd(II)-TMA layers in the two complexes are stable still upon 190 °C.     

Effect of anions on cadmium(II) complexes with ligand 2-(pyrazin-2-yl)-1H-benzimidazole

Three new supramolecular complexes based on a 2-(pyrazin-2-yl)-1H-benzimidazole (Hpbi) and a series of Cd(II) salts have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of CdCl₂·2.5H₂O with Hpbi afforded a one-dimensional chain [Cd(Hpbi)Cl₂] (1), which exhibits a three-dimensional (3-D) supramolecular architecture through intermolecular X-H···Cl (X = N and C) hydrogen bonds and π-π stacking interactions. When using CdBr₂·4H₂O instead of CdCl₂·2.5H₂O under similar reaction conditions, a bisnuclear complex [Cd(Hpbi)₂Br₂] (2) is obtained, which obviously exhibits intermolecular X-H···Br (X = N and C) hydrogen bonds and π-π stacking interactions. When CdI₂ take place of CdCl₂·2.5H₂O, a mononuclear complex, [Cd(Hpbi)₂I₂] (3), is isolated, which shows a 3D supramolecule framework formed by intermolecule hydrogen bonds and π-π packing interactions. Interestingly, the Hpbi ligand exhibits the same coordination modes in complexes 1-3. It is noteworthy that the radius of anions plays an important role in affecting the structures and luminescent intensity of the final products. The TGA for 1-3 have been investigated and discussed in detail.     

Cd(II)-ethylenediamine mono- and bimetallic complexes - Synthesis and characterization by Cd NMR spectroscopy and single crystal X-ray diffraction

Formation of three Cd(II)-ethylenediamine (en) complexes ([Cd(en)_n]²⁺, n = 1-3) in aqueous solution and in DMSO solvent has been established by means of ¹¹³Cd NMR spectroscopy. It is clearly shown that Cd(II)-en complexes form primarily in basic solutions. A correlation between the ¹¹³Cd NMR chemical shifts and the ethylenediamine (en) coordination number has been observed and discussed. Two single crystals with the composition [Cd₂(en)₅](ClO₄)₄ (1) and [Cd(en)₃](ClO₄)₂ (2) were prepared from aqueous solution, and their structures were determined by single crystal X-ray diffraction. Cd(II) ions are coordinated by six atoms in both compounds, 1 and 2: via five N-donor atoms and one O-donor atom forming a bimetallic complex 1, and via six N-donor atoms forming a distorted octahedral monometallic complex 2. Raman spectra of complexes 1 and 2 also provide additional evidence that the cis-form of the bridging en is present in complex 1.     

Rectangular tetranuclear silver(I) and μ8-selenide-centered octanuclear copper(I) complexes containing bis(diphenylphosphino)amide ligands

Interaction of Ag(CF₃CO₂) with bis(diphenylphosphino)amide (dppa) in THF gave a tetranuclear Ag₄-coplanar silver(I) complex [Ag₄(μ-dppa)₂(μ₄-O₂PPh₂)₂(μ-CF₃CO₂)₂] (1). The trinuclear trigonal-bipyramid copper(I) complex [Cu₃(μ₃-Cl)₂(μ-dppa)₃][CuCl₂] (2) was obtained from the reaction of [CuCl] powder with bis(diphenylphosphino)amide (dppa) in THF. Treatment of 2 with (Me₃Si)₂Se in THF afforded a μ₈-selenide-centered octanuclear copper(I) complex [Cu₈(μ₈-Se)(μ₄-Se)(μ₄-SeH)₃(μ-dppa)₄][(Ph₂PO)₂N] (3). The structures of 1-3 were determined by single-crystal X-ray diffraction analyses. Complex 1 comprises a rectangular Ag₄ array with each edge bridged with a pair of μ-dppa, μ₄-O₂PPh₂ and μ-CF₃CO₂ ligands that are approximately perpendicular to each other. Complex 2 contains a trigonal-bipyramid [Cu₃(μ₃-Cl)₂]⁺ core surrounded by three μ-dppa ligands. The cationic complex in 3 consists of four [Cu₂(μ-dppa)] fragments side-capped by one μ₄-Se and three μ₄-SeH ligands and center-connected by a μ₈-Se atom.     

Synthesis and characterization of [H2NC(S)NP(S)(OiPr)2] complexes of Co(II), Ni(II), Zn(II) and Cd(II)

Reaction of the potassium salt of the N-thiophosphorylthiourea H₂NC(S)NHP(S)(OiPr)₂ (HL) with Co(II), Ni(II), Zn(II) and Cd(II) cations in aqueous EtOH leads to the chelate complexes [ML₂] all showing a 1,5-S,S′-coordination formed by the CS and PS sulfur atoms of two deprotonated ligands L⁻. The structures of the resulting compounds were studied by IR, UV-Vis, ¹H, ³¹P{¹H} NMR spectroscopy and microanalysis. The metal center is found in a tetrahedral environment in [CoL₂], [ZnL₂] and [CdL₂]. According to NMR and UV-Vis spectroscopy the metal cation of [NiL₂] exhibits square planar coordination geometry in CH₂Cl₂, CHCl₃ and C₆H₆, while tetrahedral geometry is observed in acetone, DMSO and DMF. Regardless of the solvent used for the crystallization of [NiL₂], the molecular structure in the solid is always square planar as was confirmed by XRD of single crystals and magnetic measurements of the polycrystalline material. The magnetic and photoluminescent properties of all complexes are also reported.     

A novel one-dimensional chain-like structure based on sandwich-type tungstoantimonate and cadmium(II)

A novel cadmium-substituted tungstoantimonate [Sb₂W₂₁Cd(OH)₂O₇₃]¹⁴⁻ (1), has been synthesized in aqueous solution and characterized by IR, elemental analysis, TGA and cyclic voltammetry (CV). Single-crystal X-ray analysis was carried out on K_4.5Na_9.5[Sb₂W₂₁Cd(OH)₂O₇₃] · 31H₂O (1a). Polyanion 1 consists of two Cd(W) ions linked to a [Sb₂W₂₀O₇₀]¹⁴⁻ fragment via Cd-O(W) bonds leading to a sandwich-type structure. Interestingly, the polyanion [Sb₂W₂₁Cd(OH)₂O₇₃]¹⁴⁻ (1) as basic building unit is assembled into a one-dimensional (1D) chain-like structure by Cd and W atoms sharing the same site with the 50% occupations, respectively. The electrochemical behavior of 1 was investigated in buffer solution (pH 3.0) by CV. In the potential range between −0.75 and 0.2 V, the compound 1 exhibits the successive redox processes of the addenda atoms (W). The electrocatalytic experiments of the compound show that this compound has good electrocatalytic activity towards the reduction of H₂O₂.