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Tandem oxidative-dehydrogenation of primary alcohols to give α,β-unsaturated aldehydes in one pot are rare transformations in organic synthesis, with only two methods currently available. Reported herein is a novel method using the bench-stable salt methyltriphenylphosphonium perruthenate (MTP3), and a new co-oxidant NEMO·PF6 (NEMO = N-ethyl-N-hydroxymorpholinium) which provides unsaturated aldehydes in low to moderate yields. The Ley-Griffith oxidation of (hetero)arylated primary alcohols with N-oxide co-oxidants NMO (NMO = N-methylmorpholine N-oxide)/NEMO, is expanded by addition of the N-oxide salt NEMO·PF6 to convert the intermediate saturated aldehyde into its unsaturated counterpart. The discovery, method development, reaction scope, and associated challenges of this method are highlighted. The conceptual value of late-stage dehydrogenation in natural product synthesis is demonstrated via the synthesis of a polyene scaffold related to auxarconjugatin B.

Bis-thiosemicarbazones derived from the β-diketone benzoylacetone (H3banR, R=Me, Et, Ph) are potentially tetradentate N2S2 ligands whose coordination chemistry with copper is reported. In the absence of oxygen and in the presence of base they form anionic CuII complexes of the fully deprotonated ligands [CuII(banR)]–. Upon exposure to atmospheric oxygen they undergo a complex series of reactions leading to two types of products; one a ligand oxidised ketone complex [CuII(banRO)] and the other an unprecedented dimeric di-CuIII complex [(CuIII(banR))2] depending on the R substituent. Time-resolved UV-vis spectroscopy, cyclic voltammetry, spectroelectrochemistry, and electron paramagnetic resonance (EPR) spectroscopy have been used to identify intermediates on the way to stable products formed under both anaerobic and aerobic conditions. It is found that both ligand-centred and Cu-centred oxidation reactions are occurring in parallel leading to this unusually complicated mixture of products.

Marine derived cyclic peptides have inspired chemists for decades as the cavitand architecture can be compared with macrocyclic ligands, and hence easily conceived as mediators of metal-ion transport. Lissoclinamide 5 and ascidiacyclamide are two such cyclic peptides that have received much attention both for their metal ion complexation properties and biological activity; the metal ion binding properties of mimics of these two systems have been reported. Reported herein is a computational study aimed at evaluating the stability, and potential for copper(ii) ion binding by lissoclinamide 5 mimics that substitute the naturally occurring 4-carboxy-1,3-thiazole units for novel valine- and phenylalanine-derived 1,2,4-thiadiazole units. Our results suggest that one lissoclinamide 5 mimic, 1,2,4-thiadiazole (TDA)-lissoclinamide 9, may be capable of forming a complex with one CuII ion, [Cu(9-H)(H2O)]+. A complex with two CuII ions, [Cu2(9-H)(μ-OH)]2+, was also considered. These results set the stage for synthetic and experimental metal binding studies.

Several structurally related indium chlorido complexes of bis-thiosemicarbazones were prepared, starting from the appropriately substituted bis-thiosemicarbazones, using sodium methoxide in methanol. Detailed NMR studies were conducted to assign the structure including COSY, HSQC, and HMBC techniques. The structures of all indium complexes were solved using single crystal X-ray diffraction. The chlorido ligand was present at the apex of the square pyramidal coordination sphere in all indium complexes. In some complexes, an intermolecular hydrogen bond was present between the chlorine atom and an NH group. Three different indium chlorido complexes were converted into the corresponding fluorido-derivative by a simple halide exchange method using K18F. These novel complexes, containing the positron emitting isotope 18F, may have potential applications in positron emission tomography (PET).

A hexan-3,4-dione bis(4N-phenylthiosemicarbazone) gallium nitrate complex was synthesised and the structure was confirmed by NMR studies. The complex was prepared using an appropriately substituted dithiosemicarbazone and sodium methoxide in anhydrous methanol. The structure was further confirmed using single crystal X-ray crystallography. The crystal structure of gallium nitrate complex of diphenylthiosemicarbazone comprise a planar configuration of the tetradentate coordinated thiosemicarbazone with the Ga3+ ion, with the nitrate ligand occupying the apical coordination site. The X-ray structure of the gallium fluoride complex of pentan-2,3-dione bis(4N-phenylthiosemicarbazone) has been determined and confirms exchange of the nitrate can be achieved with fluoride. We show facile exchange of 18F, a positron emitter, to form the 18F-gallium complex under mild conditions, thus providing confirmation that such a transformation can be used to introduce 18F directly into nitrate-coordinated complexes of gallium-thiosemicarbozone complexes, a new labelling strategy for the preparation of imaging agents.

The hydroxyl radical is a well known reactive oxygen species important for interstellar, atmospheric, and combustion chemistry in addition to multiple biochemical processes. Although there are many methods to generate the hydroxyl radical, most of these are inorganic based, with only a few originating from organic precursor molecules. Reported herein is the observation that trimethylammonium benzyl alcohols and their corresponding deuterated isotopologues act as a good source of hydroxyl and deuteroxyl radicals in the gas-phase under collision-induced dissociation (CID) conditions. Attempts to replicate this chemistry in the condensed phase are described.

Five thiosemicarbazone ligands have been synthesized, and their coordination chemistry with gallium was investigated. The reaction of these thiosemicarbazones with gallium chloride in alcohol solutions in the presence of a base yielded the corresponding penta-coordinated Ga-Cl metal complexes. In contrast, the reaction of gallium nitrate with the ligands in the presence of alkoxides resulted in the formation of the corresponding Ga-alkoxides, rather than the anticipated Ga-nitrate complex. The crystal structures of gallium chloride and gallium methoxide complexes of diphenylthiosemicarbazone comprise a planar configuration of the tetradentate-coordinated thiosemicarbazone with Ga3+ ion, with the chloride or methoxide groups occupying the apical coordination site. The corresponding ethoxido complex was also prepared in an identical fashion, and NMR analysis confirmed structural similarity to the methoxido complex. Facile halogen exchange reactions of the gallium chloride complexes were achieved by treatment with silver nitrate, followed by addition of KF or KI to generate the gallium fluoride and iodide complexes, respectively. This method of exchange using halogenated inorganic salts aids the preparation of group 13 fluorides, which are notoriously insoluble in organic solvents, for complexation with organic ligands. All compounds have been fully characterized by NMR, and the X-ray crystal structures of two of the complexes are reported. Additionally, the positron-emitting isotope 18F was introduced in the structure of the diphenyl gallium thiosemicarbazone complex.

High resolution 13C NMR, supported by X-ray crystallography, shows the true nature of the trichloro derivative from manool or sclareol as a mixture of diastereomers comprising 70 % 13R and 30 % 13S isomers.

A new 3-alkylpiperidine compound (–)-acanthocyclamine A (1) has been obtained from the methanolic extract of Acanthostrongylophora ingens (order Haplosclerida, family Petrosiidae) collected from Wakatobi Marine National Park in South East Sulawesi, Indonesia. The structure of 1 was investigated by extensive 1D- and 2D-NMR experiments. The absolute configuration of 1 was established by X-ray crystallography from anomalous dispersion effects using Cu radiation as C2 (R), C3 (R), C7 (R), and C9 (R). A plausible biosynthetic scheme leading to 1 is presented, and compared with the biosynthetic pathway proposed for the manzamine alkaloids.

The Structure-Correlation Principle of Bürgi and Dunitz is invoked in an analysis of the structures of 2-chloro-8-methyl-4-(2-(4-picolinyl)imino-4H-pyrido[1,2-a]pyrimidine 8, 7-chloro-5-(2-thiazolyl)imino-5H-thiazolo[3,2-a]pyrimidine 9, 2-methylamino-4H-pyrido[1,2-a]pyrimidin-4-one 10, 7-methylthio-5H-thiazolo[3,2-a]pyrimidin-5-one 11, 2,3-dihydro-7-methylthio-5H-thiazolo[3,2-a]pyrimidin-5-one 12, and 1-methyl-2-[(o-tert-butylphenyl)imino]-1,2-dihydropyrido[1,2-a]pyrimidin-1-ium-4-olate 13, which have been determined by X-ray crystallography. The most notable structural peculiarities are the long ‘amidine’ and ‘amide’ C–N bonds (1.40–1.50 Å) and the tilting of the ‘amidine’ C=N and ‘amide’ C=O groups towards a ring nitrogen atom (NCX = 114–118°). Also the ‘amidine’ C=N (1.28 Å) and ‘amide’ C=O bonds (1.22–1.24 Å) are long, i.e. in the normal range for resonance-stabilized amidines and amides in spite of the lack of such resonance in these compounds. These features mimic the transition states for ring opening to ketenes. The long amidine and amide C–N bonds and acute NCX angles are in accord with the observed thermal ring opening to ketenimines and ketenes, respectively.

Three naphthaledene Schiff bases were synthesized and a detailed analysis by variable temperature X-ray crystallography and solid state electronic spectra was undertaken to assess the tautomeric composition. The crystal structures showed no significant changes despite the compounds changing colour with temperature. Solid state UV spectra were acquired at low temperature and showed that the major absorption band broadened as the temperature was increased. In one compound absorptions were observed that increased in intensity as the temperature increased. For these compounds, the major contribution to the colour change is the broadening of the absorption band as a function of temperature and not the change in enol-keto tautomeric composition.

Two polymorphs of 3-(3′-pyridyl)sydnone 4 have been investigated. It was established that the metastable P2/c form is the kinetically favoured product formed by recrystallization from solution, but this may be converted to the new, more stable, P21/c polymorph by sublimation or heating in the solid state.

This Research Front features papers selected from the 39th International Conference on Coordination Chemistry held in Adelaide (24–30 July 2010). This meeting, the premier inorganic coordination chemistry conference worldwide, had not been held in Australia since 1989. In 2010 it coincided with the RACI Inorganic Chemistry Divisional (IC’10) conference. This internationalmeeting featured excellent contributions across the various themes of the conference including materials chemistry, metals in synthesis, solar energy conversion, metals in catalysis, supramolecular chemistry, and metals in biological systems. It is from this last theme that papers have been chosen for this Research Front, and these span a wide range of topics within the ‘bioinorganic’ area. Inorganic chemistry taken literally in its original meaning from the days of ‘Vital Force Theory’, excludes the chemistry of life. Nearly 200 years after Friedrich Wohler rescued inorganic chemistry from biological irrelevance the roles of metals in biological systems are now, more than ever, the focus of intense research in biological chemistry. Within this Research Front we have two reviews. One a personal perspective by David Parker (Durham) on the development of fluorescent complexes for bio-imaging. The long fluorescent lifetimes of lanthanoid excited states enable time resolution to be used in fluorescence imaging with essentially zero background interference from any other fluorescent molecules in the sample. A second review is fromZhiguang Xiao and Tony Wedd (Melbourne) on the topic of metallo-oxidases, a fascinating family of enzymes that catalyze the oxidation of important low valent metals such as Cu(I), Fe(II), and Mn(II) bymolecular oxygen. These reactions are critical to maintaining balanced levels of redox active metals within cells and to their transport and uptake by other metalloproteins. The full papers in this Research Front are equally comprehensive in their coverage of contemporary biological inorganic chemistry. The emergence of organometallic complexes in medicinal chemistry has challenged traditional views on metal-based drugs and their interactions with biomolecules (see also the Research Front published in Aust. J. Chem. 2010, 63, issue 11). In this vein, a paper by Gilles Gasser (Zurich), Nils Meztler-Nolte (Bochum), and coworkers report new peptide nucleic acid containing ligands and their Re and Tc carbonyl complexes, the latter being of great interest in radio-imaging. The stability of these complexes and ease of formation is investigated and discussed. Water solubility can be challenge in developing ligands and complexes that exhibit suitable pharmacological properties. Paul Donnelly (Melbourne) and coworkers have developed new water soluble bisthiosemicarbazone ligands that strongly bind Cu, a suitable isotope for positron emission tomography diagnostic imaging. The effects on cellular uptake and the redox properties of their Cu(II) complexes are discussed. The use of synchrotron radiation as a tool for imaging metals within cells is covered in two different papers using distinct techniques. Trevor Hambley (Sydney) and coworkers, using X-ray absorption near-edge spectroscopy, have developed a way of extracting information about the relative proportions of Pt(II) and Pt(IV) within cells. Pt(II) complexes comprise the most thoroughly investigated metal-based anticancer drugs to date but their side effects, linked to reactions with other biomolecules, have led to new approaches including the use of more chemically inert Pt(IV) analogues. The present paper shows how the relative proportions of the Pt(II) and Pt(IV) forms of some complexes change over time within cells. Lou Rendina (Sydney), Hugh Harris (Adelaide), and colleagues have used synchrotron X-ray fluorescence (XRF) spectroscopy to identify the cellular location of a DNA-intercalating Pt-terpyridyl complex bearing a carborane thiolate ligand; a potential target in boron neutron capture therapy. Rather than localising within the nucleus, the bifunctional complex is found to be distributed throughout the cell both within and outside the nucleus. Addition of the Pt complex also has significant effects on the concentrations of other elements within the cell (alsomeasured with XRF) with an increase in Cl, K, and Cu being found while Fe levels decreased. The purple acid phosphatase (PAP) family are an interesting group of enzymes that require two metal ions in proximity, one in a trivalent and the other in a divalent oxidation state for activity. Lawrie Gahan and coworkers report a new binucleating ligand and its Fe(III)/Zn(II) complex that mimics the PAP active site found in the plant enzyme in structure and in function. This ligand also bears an olefinic substituent for future copolymerization of the complex. Only a relatively small selection of the work presented at ICCC39 was able to be included in this Research Front but the quality of these contributions, and the contributors, herein is representative of the meeting. I was fortunate to be a PhD student in 1989 when ICCC last came to Australia. It was a long wait of 21 years to see the conference return to Australia and then from a different perspective as one of the organizing committee. If this pattern is to be repeated I will have retired CSIRO PUBLISHING

The isomerization of terpinolene tetrabromide from the cis-2,4- (diaxial) dibromo isomer (A) to the more stable trans-2,4- (equatorial–axial) compound (B) has been investigated in the solid state. The progress of the solid-state reaction as a function of time was followed by solution NMR analysis, and, more effectively, by micropowder X-ray diffraction of the bulk material in situ. Characterization of the solid-state reaction mixture is facilitated by the existence of X-ray crystal structures of both compounds A (monoclinic) and B (reported previously) in addition to a new triclinic polymorph of compound A reported herein, all three forms being observed by powder X-ray diffraction.

This Special Issue of the Australian Journal of Chemistry is dedicated to Professor Alan M. Sargeson whose contributions to not only inorganic chemistry but Australian and international science were extraordinary. Over his career, Alan published more than 400 papers and more than 50 were published in Aust. J. Chem. Alan passed away in December 2008. There are several accounts of Alan’s life in chemistry. For those wishing to gain a personal insight to his academic career, particularly in the early days, his published interview with Len Lindoy makes great reading.[1] The papers in this issue come from all around the globe. All of the contributors accepted their invitation enthusiastically and without hesitation. Given space restrictions, there were only a limited number of papers that could be included here. Several contributions are from former postdoctoral fellows or graduate students who worked in his group at the Research School of Chemistry, Australian National University, and then went on to establish their own research programs. Others are international collaborators or those who simply admired and appreciated Alan’s contributions to chemistry. The chemistry of Alan Sargeson spanned all areas. Apart from his truly innovative macrocyclic ‘cage’ chemistry, his research was also groundbreaking in areas of inorganic reaction mechanisms and bioinorganic chemistry; these areas all feature prominently in this issue. My first appreciation of Sargeson chemistry came as a 3rd year chemistry undergraduate in 1985 when given the task of following synthesis of the complex [Co(diNOsar)]3+ that had been published a year before (Scheme 1).[2] The reaction involves the seemingly incongruous self assembly of nine molecules to give a crystalline product in high yield. The synthesis followed on from the groundbreaking publication reporting the analogous chemistry with ammonia, instead of nitromethane, as the capping reagent to create the first cage ligand sepulchrate complexed to CoIII and CoII.[3,4] There can be few better examples of the elegance of Sargeson ‘cage chemistry’ than this. HN HN

The new cyanido-bridged mixed valent FeII/CoIII macrocyclic complexes [L2CoIII(μ-NC)FeII(CN)5]– and trans-[L2CoIII(μ-NC)FeII(CN)4(μ-CN)CoIIIL2]2+ have been prepared and characterized spectroscopically. The trinuclear complex trans-[L2Co(μ-NC)Fe(CN)4(μ-CN)CoL2](ClO4)2·11H2O has been characterized crystallographically. The di- and trinuclear complexes exhibit metal-to-metal charge transfer transitions characteristic of Class II mixed valent chromophores and their redox and spectroscopic properties have been analyzed by Hush theory. The thiophene group attached to the macrocycle L2 in these complexes may serve as a precursor to conducting polythiophene-based hybrid materials incorporating redox active transition metal ions.

X-Ray crystallography establishes that the marine alkaloids (–)-haliclonacyclamine A 1 and (+)-haliclonacyclamine B 2 each have the configuration C2 (R), C3 (R), C7 (R), and C9 (R). The alkaloids appear to be enantiomerically pure; this provides an insight into the stereochemical consequences of the biosynthetic pathway leading to these bioactive 3-alkylpiperidine alkaloids.

As determined by X-ray crystallography, isoxazol-5(4H)-one derivatives 12–19 feature dihedral angles around the exocyclic C4=C6 double bonds of 26–90°. In the most highly twisted bis-tert-butylamino derivatives 18 and 19, the C4–C6 bonds are essentially single bonds. Density functional theory calculations at the B3LYP/6-31G(d) level with inclusion of a simulated solvent field, which helps stabilize zwitterionic structures, are in good agreement with the experimental crystallographic data. A good correlation between bond lengths and calculated π/π* orbital occupation quotients is observed. A good correlation between the twisting angle and the charge separation, measured by the calculated negative charge on the isoxazolone moiety, is also observed. Low barriers to rotation about the twisted exocyclic double bonds C4=C6 in compounds 13, 20, and 21 (ΔG ‡ = 15–16 kcal mol–1 (63–67 kJ mol–1)) were determined by dynamic 1H NMR coalescence measurements. The rotational barrier for 17 was estimated to be less than 10 kcal mol–1. The rotational barriers for compounds 10 and 18 were calculated to be ~8 kcal mol–1.

3- and 4-Pyridyliminopropadienones were prepared by flash vacuum thermolysis of Meldrum’s acid derivatives and characterized by low temperature IR spectroscopy. They react with dimethylamine to afford 1,5-, 1,6-, and 1,7-naphthyridones. The same naphthyridones are also obtained by microwave irradiation of the Meldrum’s acid derivatives. Quinolones were obtained by microwave irradiation of phenylaminomethylene-Meldrum’s acids and 1-phenylpyrrole-2,3-diones.

As determined by X-ray crystallography, Meldrum’s acid derivatives 5, 6, and 8 feature dihedral angles around the central C5=C7 double bond of 14–35°, whereas for the anion 9 this angle is 90°. Density functional theory and MP2 calculations are in agreement with the experimental X-ray data for compounds 5–8, but for anion 9 an angle of only ~65° is predicted. It is concluded that a part of the torsion is due to packing forces in the crystal. It is further concluded that these molecules undergo rapid rotation about the central CC bonds at room temperature (calculated activation barriers 5–14 kcal mol–1).

X-Ray crystallography affords the stereochemistry of three iodo compounds derived from mycophenolic acid. These included the crystallographic structure of a tertiary iodide.

Oxidoreductase enzymes catalyze single- or multi-electron reduction/oxidation reactions of small molecule inorganic or organic substrates, and they are integral to a wide variety of biological processes including respiration, energy production, biosynthesis, metabolism, and detoxification. All redox enzymes require a natural redox partner such as an electron-transfer protein (e.g. cytochrome, ferredoxin, flavoprotein) or a small molecule cosubstrate (e.g. NAD(P)H, dioxygen) to sustain catalysis, in effect to balance the substrate/product redox half-reaction. In principle, the natural electron-transfer partner may be replaced by an electrochemical working electrode. One of the great strengths of this approach is that the rate of catalysis (equivalent to the observed electrochemical current) may be probed as a function of applied potential through linear sweep and cyclic voltammetry, and insight to the overall catalytic mechanism may be gained by a systematic electrochemical study coupled with theoretical analysis. In this review, the various approaches to enzyme electrochemistry will be discussed, including direct and indirect (mediated) experiments, and a brief coverage of the theory relevant to these techniques will be presented. The importance of immobilizing enzymes on the electrode surface will be presented and the variety of ways that this may be done will be reviewed. The importance of chemical modification of the electrode surface in ensuring an environment conducive to a stable and active enzyme capable of functioning natively will be illustrated. Fundamental research into electrochemically driven enzyme catalysis has led to some remarkable practical applications. The glucose oxidase enzyme electrode is a spectacularly successful application of enzyme electrochemistry. Biosensors based on this technology are used worldwide by sufferers of diabetes to provide rapid and accurate analysis of blood glucose concentrations. Other applications of enzyme electrochemistry are in the sensing of macromolecular complexation events such as antigen–antibody binding and DNA hybridization. The review will include a selection of enzymes that have been successfully investigated by electrochemistry and, where appropriate, discuss their development towards practical biotechnological applications.

The structures of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl azide and 2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl azide were determined using X-ray crystallographic and one-dimensional NOESY techniques.

The non-bonding interaction between two bromine atoms sited 1,3-diaxially on a simple cyclohexane ring is explored by X-ray crystallography. The ring is distorted to allow the bromine atoms an interatomic distance of 3.54 Å.

Attempts to ring-close the nitrogen atom of 8-amino-p-menth-1-ene and of N-substituted 8-amino-p-menth-1-enes onto the C1–C2 double-bond carbons has led to a range of bicyclo[2.2.2] and bicyclo[3.2.1] products, together with the novel bicyclo[4.3.1]-1,3-oxazepine 9.

Laurobtusol, a minor metabolite from Laurencia obtusa, had been assigned constitution 1 and relative stereochemistry, 2. However, several stereoisomers of this novel, cyclopropane-containing system 1 have now been synthesized and spectral correspondence between the synthesized isomers and laurobtusol is lacking.

Complexation of cadmium(II) by the ditopic (bis-tridentate) thiocarbazone ligand 1,5-bis(6-methyl-2-pyridyl- methylene)thiocarbonohydrazide, H2L1, results in the self-assembly of a charge-neutral 2 × 2 molecular grid, [Cd4(L1)4], comprising four metals and four ligands in an interlocked cyclic array. The solid-state structure of this tetramer has been established by X-ray crystallography and in solution by 1H NMR spectroscopy. The presence of lower molecular weight oligomers was identified by both NMR and ESI-MS.

The 93 K X-ray crystal structure of tris(ethane-1,2-diamine)zinc(II) dinitrate is reported. As predicted by the spectroscopic studies of other workers, there is a reversible phase transition of the structure at low temperature. We have determined this temperature to be 143 K. The structure at this temperature and below resembles that of the room temperature structure, except the crystallographic D3 symmetry of the complex cation (296 K) is lowered to C2 (below 144 K) by subtle changes in cation–anion hydrogen bonding. No change in the conformation of the cation or its bond lengths and angles was found.

The major trans (1) and minor cis (2) isomers of 1,4,8,11-tetraazacyclotetradecane-6,13-dicarboxylate have been characterized as the complexes [Co(1)](ClO4) and [Co(H-2)(OH2)]Cl(ClO4).H2O. The former crystallized in the C-2/c space group and the latter in the P2(1)/c space group, with cell parameters a 16.258(7), b 9.050(3), c 15.413(6) Angstrom, beta133.29(3)degrees, and a 9.694(4), b 16.135(1), c 12.973(5) Angstrom, beta 93.00(2)degrees, respectively. Their characterization completes identification of the respective trans and cis isomers for the series of C-pendant macrocycles also including 1,4,8,11-tetraazacyclotetradecane-6-amine-13-carboxylate ((3), (4)) and 1,4,8,11-tetraazacyclotetradecane-6,13-diamine ((5), (6)). The complexes show limited distortion from octahedral geometry with the strain in the presence of the coordinated C-pendant carboxylate significantly reduced compared with that for the C-pendant amine in analogues, a consequence mainly of six-membered as opposed to five-membered chelate rings involving the pendant donor. A comparison of the physical properties for the trans isomers of the octahedral complexes of (1), (3), and (5), which reflect progressively increasing strain, is presented.

Chiral resolution of the cobalt cage complexes [Co(diNOsar)](3+) and [Co(diAMsarH(2))](5+) have been achieved by selective crystallization with the anion bis-mu-(R),(R)-tartratodiantimonate(III) ([Sb-2(R,R-tart)(2)](2-)) and also by column chromatography with Na-2[Sb-2(R, R-tart)(2)] as eluent. The X-ray crystal structures of Lambda-[ Co(diNOsar)][Sb-2(R, R-tart)(2)] Cl . 7H(2)O and Delta-[Co(diAMsarH(2))][Sb-2(R, R-tart)(2)](2)Cl . 14H(2)O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Lambda-enantiomer) to ammonio (Delta-enantiomer) and shows that the ammonio- substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb-2(R, R-tart)(2)](2-) anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na-2[Sb-2(R, R-tart)(2)] as eluent, Lambda-[Co(diNOsar)](3+) elutes first, which implies a tighter ion pairing interaction than for the Delta-enantiomer. On the other hand, Delta-[Co(diAMsarH(2))](5+) elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Delta-[Co(diAMsarH(2))](5+) and [Sb-2(R, R-tart)(2)](2-) relative to Lambda-[Co(diAMsarH(2))](5+) and [Sb-2(R,R-tart)(2)](2-).

The CeIII, PrIII, NdIII, GdIII and YbIII complexes of the heptadentate ligand 2,2´,2´´-tris(salicylideneimino) triethylamine, H3trensal (in its trianionic form), have been synthesized and characterized structurally by X-ray crystallography. These five [Ln(trensal)] structures complete a rare isomorphous and isostructural series of lanthanoid complexes in the trigonal P–3c1 space group with a ≈ 13.1 and c ≈ 16.5 A

The problems of structure in diastereomers where one chiral centre is remote from another are further investigated in the 1,2,8,9,9-pentabromo-p-menthane series.

The heptadentate ligand 2,2¢,2¢¢-tris(salicylideneimino)triethylamine (H3trensal) has been complexed with the lanthanides Sm III , Eu III , Tb III and Er III . The resulting [Ln(trensal)] complexes are isomorphous. We demonstrate that the method of preparation of these complexes is important in ensuring structural homogeneity across the Ln III series.

The reaction of the bis(1,2-diamine) copper(II) complexes of racemic propane-1,2-diamine (pn) and 2-methylpropane-1,2-diamine (dmen) with formaldehyde and nitroethane in methanol under basic conditions yields minor macrocyclic condensation products in addition to the major acyclic products. Where C-pendant methyl groups on the pair of coordinated diamines are in cis dispositions, the first -NH-CH2-C(CH3)(NO2)-CH2-NH- ring formation occurs at amine pairs distant from these C-methyl substituents, and further reaction to yield a macrocycle is not observed. However, where the C-methyl substituents are in trans dispositions, the chemistry proceeds to yield the macrocycle. Commencing with pn, trans-(6,13-diammonio-2,6,9,13-tetramethyl-1,4,7,10-tetraazacyclotetradecane)copper(II) perchlorate formed and crystallized in the space group P2(1)/n, with a 9.782(2), b 9.2794(6), c 17.017(4) Angstrom, beta 103.24(1)degrees. The copper ion is found in a square-planar environment, with the two methyl groups of the pn residues and the pairs of introduced pendant groups all in trans arrangements.

The anion (1c) of the branched polyamino acid 3-[(2'-aminoethyl)amino]-2-[(2''-aminoethyl)-aminomethyl]propionic acid (1b) binds as a quinquedentate ligand to cobalt(iii). Reaction with cobalt(II) chloride, followed by oxidation and acidification, yields exclusively one isomer of [Co(1c)Cl]+. The complex was crystallized readily as a perchlorate monohydrate salt, in the monoclinic space group P2(1)/n, a 7.921(2), b 17.357(4), c 11.852(4) angstrom, beta 107.25(2)-degrees, Z = 4; a single-crystal X-ray structure determination was refined to R 0.033 for 2099 'observed' reflections. The carboxylate and two adjacent secondary amines occupy an octahedral face, with the chloro ligand trans to the carboxylate, and the secondary amines adopt R,S stereochemistries. The Co-O distance [1.901(2) angstrom] is at the short end of the range of cobalt-carboxylate bonds, and Co-N distances [average 1.94(4) angstrom (primary amines), average 1.95(0) angstrom (secondary amines)] are slightly shorter than average for Co-N bonds. The Co-Cl distance is 2.255(1) angstrom. Molecular mechanics examination of all possible isomers and conformers of [Co(1c)Cl]+ and of the related pentaamine 1,5,9-triamino-5-methyl-3,7-diazanonane (2) indicate a greater variation in strain energy across the range of isomers and conformers in the latter more strained system.

Reaction of R,R:S,S-, R,R:R,R(or S,S:S,S)- bis (trans-cyclohexane-1,2-diamine)copper(II) with formaldehyde and nitroethane in aqueous base yields the macrocyclic molecular cation (4,15-dimethyl-4,15-dimethyl-4,15-dinitro-2,6,13,17-tetraazatricyclo[16.4.0.07,12] docosane )copper(II) with two -NH-CH2-C(Me)(NO2)-CH2-NH-links completing the macrocycle, as well as the molecular cation [N,N′- bis (2-aminocyclohexyl)-2-methyl-2-nitropropane-1,3-diamine]copper(II) with a single such link inserted. The rigid polycylic macrocycle , based on a 14-membered tetraazacycloalkane ( cyclam ) frame, may exist as a number of isomers. Spectroscopic and chiroptical properties of the isolated complexes are reported. Reduction of the nitro groups with zinc in aqueous acid produces the corresponding molecules with primary amine (or ammonium) pendants in good yield, as metal-free hydrochloride salts.

The substituted macrocycle 6,13-dimethyl-1,4,8,11- tetraazacyclotetradecane-6,13-diamine (L) can be crystallized as the perchlorate salt or the zinc dithionate complex. The crystal structures of [H4L](ClO4)4.6H2O (1) and [Zn(H2L)(S2O6)2].4H2O (2) have been determined by X-ray diffraction methods and refined to a residual of 0.058 for 1926 independent observed reflections for (1) and 0.022 for 2122 independent reflections for (2). The crystals of (1) are monoclinic, P21/c, a 10.657(2), b 12.466(7), c 12.216(3)Ǻ, β 96.73(2)° and those of (2) are monoclinic, P21/c, a 8.521(1), b 12.990(1), c 12.731(1)Ǻ,β 105.45(1)°. The pendant primary amines in the zinc(II) complex of L are protonated and not coordinated, with conformational geometry very similar in both structures.

Condensation of bis (ethane-1,2-diamine) copper(II) perchlorate with formaldehyde and diethyl malonate in basic methanol generates the new amino acid ester complex (ethyl hydrogen bis [(2-aminoethyl ) aminomethyl ] malonate )copper(II) perchlorate, [Cu(1)] (ClO4)2. Base- catalysed ester hydrolysis and decarboxylation in methanol of[Cu(1)]2+ yields, with reesterification, (methyl 3-[(2-aminoethy )amino]-2-[(2-aminoethyl) aminomethyl ]propionate)copper(II) perchlorate, [Cu(2)](ClO4)2. This complex crystallizes in the monoclinic space group P21/c, a 12.763(6), b 9.176(2), c 16.32(2)Ǻ, β 112.49 (6)°, Z 4, R 0.054 for 2626 independent 'observed' reflections. The copper ion lies in a near plane of four nitrogens with perchlorates occupying axial sites.

Reaction of the dicopper (II) complex of the binucleating ligand 5,5- bis (4-amino-2-azabutyl)-3,7-diazanonane-1,9-diamine with nitroethane and formaldehyde in water gives the respective macrobicyclic and macromonocyclic binucleating ligands 7,21-dimethyl-7,21-dinitro-2,5,9,12,16,19,23,26-octaazaspiro[13.13] heptacosane and 6,6-bis(4- amino-2-azabutyl)-13-methyl-13-nitro-1,4,8,11-tetraazacyclotetradecane , both as their dicopper (II) complexes. Similarly, condensation of the dicopper (II) complex of 5,5-bis(4-amino- 2-thiabutyl)-3,7-dithianonane-1,9-diamine with nitroethane and formaldehyde results in the binucleating macrobicycle 7,21-dimethyl- 7,21-dinitro-2,12,16,26-tetrathia-5,9,19,23-tetraazaspiro[13.13]-heptacosane. Physical properties of all complexes are reported and comparisons with mononuclear relatives are made. Structural parameters derived from electron paramagnetic resonance spectra are discussed.

Crystals of [H4L]1.5[Fe(CN)6]2.3H2O.¾HCN form readily from an aqueous solution of L=6HCI (L = 6,13-dimethyl-1,4,8,11- tetraazacyclotetradecane-6,13-diamine) and Na3 [Fe(CN)6]. The compound is monoclinic, space group P21/c, a 7.982(6), b 20.785(3), c 26.81(1) � , β 101.37(5), Z = 4. Protonation is complete at the terminal primary nitrogens, but in the ring one trans pair is protonated and the other not, with short trans H…H distances. Hydrogen-bonding interactions are a feature of the structure, but are concentrated more strongly at the terminal NH3+ groups. Interactions of [Fe(CN)6]3- nitrogens with both terminal amine protons and macrocycle ring amine protons are observed, and this structure represents a further example of a 'super complex' involving a complex anion and a protonated polyaza macrocycle.

Both nickel(II) and copper(II) complexes of the sterically hindered linear tetraamines 1,3,5,7-tetra-azabicyclo [3.3.l]nonane-3,7-bis( ethanamine (4) and 3,3′-(ethane-1,2-diyl)bis(1,3,5,7-tetraaza-bicyclo [3.3.1] nonane (7) have been prepared from reaction of ethane-1,2-diamine complexes with formaldehyde and ammonia or by reaction of the metal salt with the quaternary 'hexamminium' cation (8) and ammonia, respectively. Spectroscopic properties and kinetics of the acid hydrolyses of these complexes are reported. Observed pseudo-first-order rate constants are of the order of 10-1 s-1 at 25° in 1 mol dm-3 HCl/NaCl; acid dependencies are reported. In addition to (4), a further acid-stable and presumably macrocyclic compound could be produced from reaction of [cu(en)2]2+ with formaldehyde and ammonia, assigned tentatively as (9). Further reaction of the nickel(II) complex of (4) with formaldehyde and nitroethane yielded the macrocyclic complex of (10), which was characterized by a crystal structure analysis. Reduction with zinc amalgam yielded an amine-substituted macrocyclic complex from the nitro-substituted precursor. The title complex [Ni(10)](ClO4)2.H2O crystallized in the space group P21/n, a 14.367(2), b 13.099(2), c 12.325(3) � , β 101.01(1)�. The nickel(II) was located in a square plane of two secondary (Ni-N 1.92 � ) and two tertiary nitrogens (Ni-N 1.93 � ); the 'football' formed as one cap from ammonia and formaldehyde condensation was clearly defined.