Cadmium Derivatives Research Articles

Metal Azolate/Carboxylate Frameworks as Catalysts in Oxidative and C-C Coupling Reactions.

The five metal azolate/carboxylate (MAC) compounds [Cd(dmpzc)(DMF)(H2O)] (Cd-dmpzc), [Pd(H2dmpzc)2Cl2] (Pd-dmpzc), [Cu(Hdmpzc)2] (Cu-dmpzc), [Zn4O(dmpzc)3]·Solv (Zn-dmpzc·S), and [Co4O(dmpzc)3]·Solv (Co-dmpzc·S) were isolated by coupling 3,5-dimethyl-1H-pyrazol-4-carboxylic acid (H2dmpzc) to cadmium(II), palladium(II), copper(II), zinc(II), and cobalt(II) salts. While Cd-dmpzc and Pd-dmpzc had never been prepared in the past, for Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S we optimized alternative synthetic paths that, in the case of the copper(II) and cobalt(II) derivatives, are faster and grant higher yields than the previously reported ones. The crystal structure details were determined ab initio (Cd-dmpzc and Pd-dmpzc) or refined (Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S) by means of powder X-ray diffraction (PXRD). While Cd-dmpzc is a nonporous 3D MAC framework, Pd-dmpzc shows a 3D hybrid coordination/hydrogen-bonded network, in which Pd(H2dmpzc)2Cl2 monomers are present. The thermal behavior of the five MAC compounds was investigated by coupling thermal analysis to variable-temperature PXRD. Their catalytic activity was assessed in oxidative and C-C coupling reactions, with the copper(II) and cadmium(II) derivatives being the first nonporous MAC frameworks to be tested as catalysts. Cu-dmpzc is the most active catalyst in the partial oxidation of cyclohexane by tert-butyl hydroperoxide in acetonitrile (yields up to 12% after 9 h) and is remarkably active in the solvent-free microwave-assisted oxidation of 1-phenylethanol to acetophenone (yields up to 99% at 120 °C in only 0.5 h). On the other hand, activated Zn-dmpzc·S (Zn-dmpzc) is the most active catalyst in the Henry C-C coupling reaction of aromatic aldehydes with nitroethane, showing appreciable diastereoselectivity toward the syn-nitroalkanol isomer (syn:anti selectivity up to 79:21).

Differences in cadmium transfer from tobacco to cigarette smoke, compared to arsenic or lead

Arsenic, cadmium and lead levels in tobacco filler and cigarette smoke were determined in a 568-sample worldwide survey. Median tobacco levels for arsenic, cadmium and lead were 237, 769 and 397ng/g respectively, comparable to those previously reported albeit somewhat lower for lead and cadmium. Median mainstream smoke yields for arsenic, cadmium and lead were <3.75, 18.2, and <12.8ng/cig. under ISO, and <8.71, 75.1 and <45.7ng/cig. under Health Canada Intense (HCI) smoking regime respectively. In the case of cigarettes with activated carbon, a selective retention of cadmium but not lead or arsenic was observed. This effect was more pronounced under ISO than under HCI smoking regimes. Cadmium selective retention by activated carbon was confirmed by testing specially designed prototype cigarettes and the causes for this selective filtration were investigated. The differences between cadmium, arsenic and lead in terms of their speciation in tobaccos and in cigarette smoke could be related to their distribution in the ash, butt, mainstream (in gas-phase and particulate-phase) and sidestream smoke of a smoked cigarette. The possible formation of organometallic cadmium derivatives in the smoke gas-phase is discussed, the presence of which could adequately explain the observed cadmium selective filtration.

Synthesis, characterization and bio-activity of a bidentate NS Schiff base of S-allyldithiocarbazate and its divalent metal complexes: X-ray crystal structures of the free ligand and its nickel(II) complex

Transition metal complexes ML2 (2–6) [where M = Ni(II), Cu(II), Zn(II), Cd(II), Pd(II) and HL = allyl-2-(4-benzyloxyphenylmethylene)hydrazine carbodithioate (1)] have been prepared by the reaction of the ligand with metal ions in 2:1 molar ratio and characterized by physicochemical techniques and spectroscopic methods. The crystal structures of the free ligand and its nickel(II) complex 2 have been determined by X-ray diffractometry. The ligand exists in its thione tautomeric form both in solution and in the solid state. In complex 2, square-planar coordination of nickel(II) was achieved by two chelating ligand moieties coordinating through the azomethine nitrogen and the deprotonated thione sulphur atom. Based on the crystal structures of analogous dithiocarbazate species, a square-planar geometry was assumed for the copper(II) and palladium(II) complexes, and a tetrahedral coordination sphere for the zinc(II) and cadmium(II) derivatives. The in vitro bactericidal activity suggests that the palladium(II) complex is strongly active against two bacteria. The cadmium(II) complex is moderately cytotoxic with an LC50 value of 409 μg/ml, but less active than gallic acid, LC50 = 78 μg/ml.

Diverse Topologies in Chiral Divalent Metal Camphorate Coordination Polymers Containing 4,4′-Dipyridylamine

Hydrothermal synthesis has afforded six chiral divalent metal coordination polymers containing d-camphorate (d-cmph) and 4,4′-dipyridylamine (dpa) ligands, whose topologies depend largely on metal coordination geometry preference. Both cadmium derivatives {[Cd(dpa)(d-cmphH)2(H2O)]·0.875H2O}n (1) and {[Cd(d-cmph)(dpa)(Hdpa)]ClO4}n (1a) exhibit one-dimensional (1-D) chains with protonated pendant ligands; 1 possesses sinusoidal chains with a “wavelength” of over 67 Å. [Zn2(d-cmph)2(dpa)(H2O)]n (2) exhibits a two-dimensional (2-D) 3,4-connected binodal net with (53)2(5482) topology. {[Ni(d-cmph)(dpa)]·3H2O}n (3) and {[M2(d-cmph)2(dpa)]·H2O}n (M = Co, 4; M = Cu, 5) manifest three-dimensional (3-D) networks. The nickel derivative has an uncommon 2-fold interpenetrated 4-connected 4284lvt topology, while the isostructural cobalt and copper complexes possess 6-connected pcu topologies based on {M2(OCO)4} paddlewheel dimers. Complexes 1/1a and 2 undergo visible light emission upon ultraviolet excitation. Variable temperature magnetic susceptibility experiments indicate weak (J = −3.6(2) cm–1) and strong (J = –202(5) cm–1) antiferromagnetic coupling for 4 and 5, respectively.

On Ligand Binding Energies in Porphyrinic Systems

Abstract Energy decomposition analysis is a powerful tool to study the bond properties of molecules. Here, we used a recent implementation by P. Su and H. Li (J. Chem. Phys. 131 (2009) 014102) to test the method for investigations of ligand binding to medium sized molecules (30–40 atoms). We studied the properties of the bond between porphyrins or phthalocyanines with central metals without (Mg) or with a closed d shell (Zn and Cd) to ligands binding via various row II and III atoms (nitrogen, oxygen, phosphorus and sulphur) using various methods and basis sets. Several interesting results could be deduced: In the porphyrins, ligands binding via a nitrogen atom were preferred to those binding via oxygen and sixfold coordination was readily available for magnesium as central metal atom as opposed to zinc and cadmium derivatives which also showed a weaker bond strength. In phthalocyanines, a tendency to form fivefold coordination was also seen for magnesium compounds and bonds to nitrogen and oxygen had the same strength. Ligation to row III elements created only weak bonds that were prone to fluctuations.

Ion-Selective Controlled Assembly of Dendrimer-Based Functional Nanofibers and Their Ionic-Competitive Disassembly

The construction of hierarchical materials through controlled self-assembly of molecular building blocks (e.g., dendrimers) represents a unique opportunity to generate functional nanodevices in a convenient way. Transition-metal compounds are known to be able to interact with cationic dendrimers to generate diverse supramolecular structures, such as nanofibers, with interesting collective properties. In this work, molecular dynamics simulation (MD) demonstrates that acetate ions from dissociated Cd(CH(3)COO)(2) selectively generate cationic PPI-dendrimer functional fibers through hydrophobic modification of the dendrimer's surface. The hydrophobic aggregation of dendrimers is triggered by the asymmetric nature of the acetate anions (AcO(-)) rather than by the precise transition metal (Cd). The assembling directionality is also controlled by the concentration of AcO(-) ions in solution. Atomic force (AFM) and transmission electron microscopy (TEM) prove these results. This well-defined directional assembly of cationic dendrimers is absent for different cadmium derivatives (i.e., CdCl(2), CdSO(4)) with symmetric anions. Moreover, since the formation of these nanofibers is controlled exclusively by selected anions, fiber disassembly can be consequently triggered via simple ionic competition by NaCl salt. Ions are here reported as a simple and cost-effective tool to drive and control actively the assembly and the disassembly of such functional nanomaterials based on dendrimers.

Structure and Physical Properties of Two- and Three-Dimensional Divalent Metal Adipate Coordination Polymers with Bis(4-pyridylmethyl)piperazine Tethers

Hydrothermal reaction of divalent metal salts, adipic acid and bis(4-pyridylmethyl)piperazine (bpmp), resulted in the generation of a series of coordination polymers whose two-dimensional and three-dimensional topologies depend on coordination environment, adipate conformation and carboxylate binding mode, and piperazinyl ring protonation. {[Cd(adipate)(H2bpmp)(H2O)]SO4·4H2O}n (1) manifests simple (4,4) grid cationic layers, while its oxoanion-free congener [Cd(adipate)(bpmp)]n (2) has a 5-fold interpenetrated diamondoid lattice. {[Cu(adipate)(Hbpmp)(H2O)]ClO4·3H2O}n (3) displays {Cu2O2} dimer-based (4,4) grid cationic layers. The isostructural complexes [M(adipate)(bpmp)(H2O)]n (M = Co, 4; M = Ni, 5) possess anti−syn bridged one-dimensional [M(OCO)]n chains and rare 3,5-connected binodal nets with (4.62)(4.6683) topology. The cadmium derivatives 1 and 2 undergo blue-violet light emission on excitation with ultraviolet. Antiferromagnetic coupling is observed in 3, while ferromagnetic superexchange occurs ...

Self-adaptation of a conformationally flexible yet restricted “piperazine-pyrazine” building block toward the design of coordination polymers

A family of divalent metal–organic coordination polymers (MOCPs) that contain a conformationally flexible N,N′-bis(2-pyrazinyl)piperazine (bpzp) ligand were reported. The MOCPs {[Cu(bpzp)2(NO3)2]·3H2O}n (1·3H2O), {[Co(bpzp)2(NCS)2]·CH2Cl2·2CH3OH}n (2·CH2Cl2·2CH3OH) and {[Ni(bpzp)2(NCS)2]n·4CH3OH}n (3·4CH3OH) possess nearly identical extended rhombic grid-like (4,4)-layered networks, of which the latter two are isostructural and isomorphous. These layers are stacked in an eclipsed AAA arrangement for 1 and in a stagered ABABAB arrangement for 2 and 3. This can be attributed to the different conformations of the bpzp ligand, namely a C-e,e-anti conformer observed in 1 and a C-a,a-anti conformer in 2 and 3. In the case of [Ni(bpzp)3(NO3)2]n (4) and [Cd(bpzp)3(ClO4)2]n (5), the bpzp ligand is present as both a bridged bismonodentate C-e,e-anti conformer and a terminal monodentate C-e,e-syn conformer, leading to the formation of nearly identical linear chain structures. On the other hand, the MOCP {[Cd2(bdc)2(bpzp)3(H2O)2]·H2O}n (6·H2O, bdc = 1,4-benzenedicarboxylate) exhibits a 2D honeycomb (6,3)-layer structure, comprised of 1D Cd(bdc)-chain subunits and C-a,a-anti configured bpzp linkages. The MOCP [Cd2(btec)(bpzp)]n (7, btec = 1,2,4,5-benzenetetracarboxylate) adopts an extended 3D network comprised of Cd(btec)-based layers and C-e,e-anti configured bpzp pillars. These materials are thermally stable at temperatures up to 200 °C. The photoluminescence properties of the free bpzp ligand and the cadmium derivatives were also examined.

Structural and Thermodiffractometric Analysis of Coordination Polymers. Part II:1 Zinc and Cadmium Derivatives of the Bim ligand [Bim = Bis(1-imidazolyl)methane

New polynuclear coordination species containing the ditopic bis(1-imidazolyl)methane (Bim) ligand have been prepared as microcrystalline powders and structurally characterized by ab initio X-ray powder diffraction methods. [Zn(CH3COO)2(Bim)]n contains 1D chains with tetrahedral metal atoms bridged by Bim ligands; [CdBr2(Bim)]n shows a dense packing with hexacoordinated Cd(II) ions and mu-Br and mu-Bim bridges; at variance, the isomorphous [ZnCl2(Bim)]n and [ZnBr2(Bim)]n species contain cyclic dimers based on tetrahedral Zn(II) ions. Thermodiffractometric analysis allowed estimation of the linear thermal expansion coefficients and strain tensors derived there from. Bim-rich phases, with 2:1 ligand-to-metal ratio, were also isolated: ZnBr2(Bim)2(H2O)3 and [Cd(CH3COO)2(Bim)2]n containing cis and trans MN4O2 chromophores, respectively, show 1D polymers built upon M2Bim2 cycles, hinged on the metal ions. In all species the conformation of the Bim ligands is Cs (or nearly so), while in the few sparse reports of similar coordination polymers the alternative C2 one was preferentially observed.

Synthesis, Structures, and Luminescence Behavior of Mixed Metal Alkynyl Platinum−Cadmium Complexes

This article describes the preparation, characterization, and optical properties of new bi- and trinuclear tweezer-type platinum cadmium derivatives, stabilized by η2-alkyne−cadmium bonding. Treatment of Q2[cis-Pt(C6F5)2(C⋮CR)2] (1a−1c) with CdCl2·2,5 H2O (1:1) produces dinuclear Pt−Cd adducts Q2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}(CdCl2)] (Q = NBu4, R = t-Bu 2a; Q = PMePh3, R = Ph 2b; R = Tol 2c). However, reaction of (NBu4)2[cis-Pt(C6F5)2(C⋮CR)2] with Cd(NO3)2·4H2O produces trinuclear Pt2Cd dianionic complexes (NBu4)2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}2Cd] (3a−3c). The analogous (PMePh3)2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}2Cd] (R = Ph 3b‘; Tol 3c‘) were prepared similarly starting from (PMePh3)2[cis-Pt(C6F5)2(C⋮CR)2]. The crystal structures of 2c and 3a,b show that the cadmium center is well embedded by the cis-bis(alkyne)platinate entities, leading to planar PtC4Cd cores. In the heterometallic species, the low-energy absorption, which is ascribed to an admixture of π → π*(C⋮CR) IL/dπ(Pt) → π*(C⋮CR) MLCT, exhibits a clear hypsochromic shift compared to its precursors, probably due to the existence of a lesser delocalization on the alkynyl fragments upon the η2-complexation. The arylalkynyl derivatives (b, c) display intense structured emission bands, arising from 3ππ*(C⋮CR) (IL) and/or mixed 3ππ*/Pt(dπ)(C⋮CR) → π*(C⋮CR) (3MLCT) manifolds with a predominant IL character.

Synthesis, Characterization, and Optical Properties of Pentafluorophenyl Complexes with a Pt−Cd Bond

Novel bimetallic neutral [(C6F5)4PtCd(cyclen)] and [(C6F5)2(C⋮CPh)2PtCd(cyclen)] (1, 2) and cationic [(C6F5)2(bzq)PtCd(cyclen)](ClO4) (3) pentafluorophenylplatinum(II)−cadmium(II) derivatives have been prepared by treatment of the adequate anionic starting precursors [Pt(C6F5)2X2]n- (n = 2, X = C6F5, C⋮CPh; n = 1, X2 = bzq) with Cd(ClO4)2 and cyclen. X-ray diffraction studies on complexes 1, 2, and 3 show that they are stabilized by a short Pt→Cd donor acceptor bond and, additionally, in complex 2 the Cd center is also coordinated to the Cα of one of the two alkynyl groups. In contrast, treatment of the binuclear compound [NBu4]2[Pt2(μ-Cl)2(C6F5)4] with [Cd(cyclen)(MeOH)2](ClO4)2 afforded the tetranuclear derivative [Pt(C6F5)2Cl(μ-Cl)Cd(cyclen)]2 (4) (X-ray), in which Pt and Cd atoms are connected by a μ3-Cl bridging ligand, and the binuclear cadmium complex [Cd2(μ-Cl)2(cyclen)2](ClO4)2 (5) (X-ray), in which two “Cd(cyclen)” fragments are bridged by two chlorine atoms. The photoluminescent properties of c...

ZINC AND CADMIUM DERIVATIVES CONTAINING SEVERAL 4-ACYL-5-PYRAZOLONATE DONORS AND ADDITIONAL ANCILLARY LIGANDS

Article ZINC AND CADMIUM DERIVATIVES CONTAINING SEVERAL 4-ACYL-5-PYRAZOLONATE DONORS AND ADDITIONAL ANCILLARY LIGANDS was published on May 1, 2001 in the journal Main Group Metal Chemistry (volume 24, issue 5).

Novel bis(acylpyrazolonato)cadmium(II) derivatives and their reactivity toward aromatic and aliphatic N2-donor ligands

By reaction of 1-phenyl-3-methyl-4-R-C(O)-pyrazol-5-one (HQT: R = CH2C(CH3)3; HQC: R = C6H11) with Cd(O2CCH3)2·2H2O in EtOH the derivatives [Cd(QT)2(EtOH)2] 1 and [Cd(QC)2(EtOH)2] 2 have been synthesised. Complex 1 has a molecular structure with a slightly distorted octahedral coordination of the cadmium atom with EtOH and QT ligands trans to each other. When the reaction between HQT or HQC and Cd(O2CCH3)2·2H2O was carried out in the presence of bidentate N-donor ligands L (L = 1,10-phenanthroline, 2,2′-bipyridyl, N,N′,N′-trimethylethylenediamine or tetramethylethylenediamine), [Cd(QT)2(L)] and [Cd(QC)2(L)] were always obtained. In the six-coordinate derivatives [Cd(QC)2(1,10-phenanthroline)] and [Cd(QT)2(tetramethylethylenediamine)] the cadmium atom is in a strongly distorted octahedral environment due to steric requirements of the bidentate N2-donor ligands. All complexes synthesized have been characterized spectroscopically by IR, 1H and 113Cd NMR. The behavior in solution is also discussed.

Group 12 metal complexes of tetradentate N 2O 2–Schiff-base ligands incorporating pyrazole : Synthesis, characterisation and reactivity toward S-donors, N-donors, copper and tin acceptors

New [M(Q) 2(X)] derivatives (where M=Zn, Cd or Hg; Q=1-phenyl-3-methyl-4-R(C=O)-pyrazolon-5-ato; in detail: Q L, R=C 6H 5; Q B, R=CH 2C(CH 3) 3; Q S, R=CH(C 6H 5) 2; X=EtOH or H 2O) have been synthesised and characterised. These compounds undergo a condensation reaction with the appropriate diamine in ethanol, affording novel Schiff-base metal derivatives [M(diaquo)bis(1-phenyl-3methyl-4-R(C=N)-pyrazolone)(CH 2) n diimmine] (L nH 2, R=C 6H 5, n=2, 3 or 4; B nH 2, R=CH 2C(CH 3) 3, n=2, 3 or 4; S nH 2, R=CH(C 6H 5) 2, n=2 or 3; M=Zn, Cd or Hg). These compounds possess a six-coordinate metal environment. A 113Cd NMR study has been carried out on cadmium derivatives. The derivative [Zn(L 2)(H 2O) 2] reacted with CuCl 2 and with Cu(ClO 4) 2 affording [Cu(Q L) 2] and [Cu(en) 2](ClO 4) 2 (en=ethylendiamine), respectively, upon breaking of the C=N bond in the Schiff-base donor. In addition [Zn(L 2)(H 2O) 2] reacted with 1,10-phenanthroline (phen), yielding the derivative [Zn(Q L) 2(phen)]. Whereas when [Zn(L 2)(H 2O) 2] reacted with CdCl 2, formation of [Cd(L 2)(H 2O) 2] due to exchange of the metal centre was observed. Finally the derivative [Zn(L 2)(Hmimt)], likely containing a five-coordinate ZnN 2O 2S central core, has been obtained from the exchange reaction between [Zn(L 2)(H 2O) 2] and 1-methylimidazolin-2-thione (Hmimt).

Boron and transition metal compounds derived from 2-uroylbenzimidazole

The coordination sites of 2-uroylben- zimidazole 1 toward diphenylborinic acid, as well as zinc, cadmium, copper, nickel and cobalt chlorides, bromides, and nitrates were investigated. The ligand is bonded in monodentate mode to ZnCl2, ZnBr2, CdCl2, CdBr2, and Cd(NO3)2, and in bidentate mode to all oth- ers. With diphenylborinic acid, two heterocycles are formed; in one, the boron is bonded to imidazole and the terminal NH2 group, and in the other the boron is bonded to imidazole and to the oxygen atom. Boron, zinc, and cadmium derivatives were studied by NMR spectroscopy. The X-ray diffraction structure of 2- uroylbenzimidazole is reported. q 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 577-584, 1999

Methylzinc or methylcadmium‐N,N,N‐trimethyl‐ propylenediaminedithiocarbamates: Precursors for zinc or cadmium sulfide. The X‐ray crystal structure of methylcadmiumtrimethylpropylene‐ diaminedithiocarbamate benzene solvate

Deposition of metal chalcogenides by metal‐organic chemical vapor deposition can be achieved using various systems, including alkyl‐metal‐dithio‐ or diselenocarbamates. Initial attempts to modify the behavior of such precursors by changing the nature of the carbamato ligand are reported. Among the results presented are the synthesis and characterization of the two title compounds and the single‐crystal X‐ray structure of one of them. For both the zinc and cadmium derivatives the films grown were of a better quality than those grown from the parent compounds or from zinc‐ or cadmium‐diethyldithiocarbamate.

Cadmium‐free stabilizer systems for flexible vinyl

AbstractRecently, cadmium‐containing additives for plastics have been designated as undesirable environmentally. Prior to this adverse characterization of cadmium derivatives most flexible vinyl in the United States involving severe stabilizer demand during processing or service utilized metal blends based on cadmium salts. As a result many vinyl formulators have been forced to find suitable alternatives. Replacement of a stabilizer composed of specific levels of barium/cadmium salts in flexible vinyl with another containing the same levels of barium/zinc has been found to give dramatically reduced performance in heat stability tests. Results of this study has shown that satisfactory replacement of barium/cadmium/zinc or barium/cadmium systems in flexible vinyl is possible with barium/zinc stabilizers. This replacement appears to depend on higher barium‐to‐zinc ratios than those utilized in barium/cadmium analogs, use of special ligands that compensate for the smaller sized zinc cation; and prevention of their destruction by inadvertent addition of competitors.

Cadmium-113 and carbon-13 NMR of cadmium(II) transferrins

The cadmium(II) derivatives of ovotransferrin and human serum transferrin have been investigated through {sup 113}Cd and {sup 13}C NMR spectroscopy. A sharp {sup 113}Cd signal due to the bound Cd(II) ion is observed at 21.6 and 11.7 ppM for ovotransferrin and human serum transferrin, respectively. These chemical shift values are consistent with the involvement of only one histidine in each metal-binding set of the protein, as indicated by the recent x-ray structure of human lactoferrin. In the {sup 13}C NMR spectra the protein-bound carbonate signal is found in both cases at 168.2 ppM, and it clearly splits into a doublet (J {approximately} 20 Hz) when the protein contains {sup 113}Cd-enriched cadmium, thus giving further evidence of direct metal-carbonate binding. The addition of the nonsynergistic anion perchlorate to the ovotransferrin derivative resulted in the removal of the bound cadmium. 29 refs., 5 figs.

Interaction of related open-chain and macrocyclic ligands incorporating oxygen- and nitrogen-donor atoms with COII, NiII, CuII, ZnII, and CdII. X-Ray structures of a seven-co-ordinate zinc(II) complex as well as seven- and eight-co-ordinate cadmium(II) derivatives

The interaction of CoII, NiII, CuII, ZnII, and CdII with an O2N3-donor open-chain ligand has been investigated and the properties of the resulting 1 : 1 complexes compared with those of two related macrocyclic derivatives. The log K values have been determined in 95% methanol (I= 0.1 mol dm–3, NEt4ClO4). X-Ray structures of the cadmium complexes of the open-chain ligand (L1) and the cyclic derivative (L3) are presented. The open-chain ligand complex is seven-co-ordinate with an approximate pentagonal-bipyramidal co-ordination geometry: nitrate ions occupy axial sites with the O2N3-donor set of the organic ligand co-ordinating equatorially. The complex of the macrocycle (L3)(O2N4-donor set) is eight-co-ordinate with the six macrocyclic donor atoms showing only a small deviation from planar co-ordination while the backbone of the macrocycle is not flat but adopts a puckered arrangement. A nitrate ion occupies one ‘axial’ co-ordination site while the second site is occupied by a water in half of the molecules and a methanol in the remaining half. Solution studies indicate that this latter cadmium complex is substantially more stable than its zinc analogue, an observation which may reflect the better accommodation of the larger cadmium ion by this (18-membered ring) macrocycle relative to ZnII. Molecular-mechanics calculations provide no evidence of any mismatch between the macrocyclic cavity and the cadmium ion. The X-ray structure of the zinc complex of the related O2N3-donor macrocycle (L2) has also been determined; ZnII is seven-co-ordinate with the macrocycle binding to this ion via its five donor groups in an approximately pentagonal-planar fashion. The axial sites are occupied by a nitrate ion and a water molecule, respectively.

ChemInform Abstract: The Direct Electrochemical Synthesis of Zinc and Cadmium Derivatives of α,ω‐Alkanedithiols and Their Reaction with Carbon Disulfide.

AbstractThe electrochemical oxidation of a metal anode (Cd or Zn) in a non‐aqueous solution (MeCN) of the title ligands gives the corresponding polymeric complexes (I).