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Thiosemicarbazone complexes possess structural diversity and variable bonding patterns and potential biological implications and ion sensing abilities. The ability of the transition metals to acquire different geometries like octahedral, square planar and tetrahedral in different coordination environments has encouraged researchers to explore the coordination chemistry of thiosemicarbazone complexes which can also vary upon changing aldehydes and ketones, substituents attached to the carbonyl moiety, metal and its oxidation state, geometries, counter ions, presence of a solvent or additional molecules in the structures and substituents on the S or N(4)-atoms. This review aims to summarize recent developments in the synthesis and medicinal importance of thiosemicarbazone ligands and particular emphasis on their metal complexes. The mixed ligand-metal complexes have an important role to play in biological systems because a number of ligands try to combine with the same metal ions in vivo. Different ligands have different biological activities producing synergetic results and enhancing the potency of the formed complex. They also have a role to play in the storage and transport of substances, therefore the review article also covers the mixed ligand complexes of thiosemicarbazones with hetero ligands like 1,10-phenanthroline, pyridine, triphenyl phosphine etc. and their mechanistic action and medicinal benefits in recent years. The binuclear complexes of thiosemicarbazones with two different and same metal ions have also been explored here. Dinuclear complexes have been shown to possess interesting structures and in most cases, such complexes containing metal–metal bond also affects the complex's magnetic properties as well. It has been well discussed in the course of this study that metal complexes show enhanced biological activity than the free ligand or metal ion. The studies cited in the review have been sourced from publications indexed in known databases. Some of the recently explored structural alterations have been discussed in the paper and future substituted thiosemicarbazones and their complexes may emerge as multi-target inhibitors. [ABSTRACT FROM AUTHOR]

Magnetoactive coordination compounds exhibiting bi- or multistability between two or more magnetic stable states present an attractive example of molecular switches. Currently, the research is focused on molecular nanomagnets, especially single molecule magnets (SMMs), which are molecules, where the slow relaxation of the magnetization based on the purely molecular origin is observed. Contrary to ferromagnets, the magnetic bistability of SMMs does not require intermolecular interactions, which makes them particularly interesting in terms of application potential, especially in the high-density storage of data. This paper aims to introduce the readers into a basic understanding of SMM behaviour, and furthermore, it provides an overview of the attractive Co(II) SMMs with emphasis on the relation between structural features, magnetic anisotropy, and slow relaxation of magnetization in tetra-, penta-, and hexacoordinate complexes. [ABSTRACT FROM AUTHOR]

Five metal dithiocarbamate complexes [M(PTHIQDTC)2] [where PTHIQDTC is (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate anion and M is Ni(II) (1), Sn(II) (2), Hg(II) (3), Pb(II) (4) and Zn(II) (5)] were synthesized from the reaction of MX2 (X is Cl– for 1–3 and OAc– for 4–5) with ligand of triethylammonium (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate [Et3NH][PTHIQDTC] in methanolic solution at room temperature. The five complexes were characterized by IR, 1H and13C NMR, mass spectrometry, elemental analysis and TGA analysis. Recrystallization of [Zn(PTHIQDTC)2] (5) in dimethylsulfoxide (DMSO) converts 5 to [Zn(PTHIQDTC)2(DMSO)] (6). The structure of complex 6 has been determined by X-ray crystallography. The X-ray structural analysis of 6 indicated that the zinc(II) is five-coordinated in a distorted trigonal-bipyramidal by four S atoms from two (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate anion ligands (PTHIQDTC) and one O atom from DMSO. [ABSTRACT FROM AUTHOR]

A DFT (density functional theory) investigation using the generalized gradient approximation BP86 and the hybrid B3LYP functionals and TZP basis set is dealing with the bonding, the electronic structure and the interaction types occurred within the XCuL' and (LCuL')+ (X = Cl, CH3, CN, CF3, L = CO, NH3, PH3, and L' = C2H2, C2H4, C4H6, C6H6, and NHC) complexes. The optimized structures and energy decomposition analysis of XCuL' and (LCuL')+ complexes were employed to provide a relationship between the bond lengths, the X-Cu-L' and L-Cu-L' bond angles, the Wiberg indices, the Mayer bond orders, interaction energies, and the Cu-L' bonding character. The energy decomposition analysis indicates that the interactions occurred for various L' ligands are more electrostatically than covalently bonded to the Cu(I) center formally of + I oxidation state. The different contributions stemming from electrostatic and orbital interactions are significant, in relationship with the ionic and covalent characters, respectively. The contribution from σ-donation to the bonding energy was found more important for the NHC ligand than the alkene and alkynes ones. However, the contribution from π-back-donation was found to be comparable for all complexes. The σ-bonding contributes more than 50% into the total orbital interaction overtaking those of π type, in accordance with the population of the copper 4s orbital, particularly in the presence of C6H6 and NHC ligands. The interactions in all complexes exhibit comparable deformation densities and NOCV orbital shapes. Besides, it has been shown that the ΔEprep contributes weakly in the deformation of the interacting fragments as well as the BSSE correction which impacts weakly or negligibly the interactions between the fragments composing different XCuL' and (LCuL')+ complexes. [ABSTRACT FROM AUTHOR]

In this paper, we report a facile hydrothermal route to prepare different morphologies of zinc sulfide nanostructures, using a new inorganic precursor, zinc phthalate [Zn(pht)(HO)], and different sulfur sources. This study focuses on the effect of different sulfur sources on the crystal structure and morphology of the products. The structural and morphological studies of the products were performed by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The high temperature (over 1020 °C) hexagonal ZnS nanostructured spheres self-assembled from ZnS nanocrystals have been synthesized at a low temperature of 160 °C by using thioglycolic acid as sulfur source. [ABSTRACT FROM AUTHOR]

Dioxygen binding at copper enzymatic sites is a fundamental aspect of the catalytic activity observed in many biological systems such as the monooxygenases, especially peptidylglycine α-hydroxylating monooxygenase (PHM), in which two mononuclear CuI sites are involved. Biomimetic models have been developed: dipods, tripods, and, more recently, functionalized calixarenes. The modelling of calixarene systems, although not unreachable for theory yet, requires, however, a number of preliminary investigations to ensure proper calibrations if relevant description of the metal–ligand interaction at the hybrid quantum mechanical/molecular mechanics levels of theory is the aim. In this paper, we report quantum chemistry investigations on a coherent series of representative cuprous tripodal species characterized by (1) monodentate ligands [Cu(ImH)3]+ (where ImH is imidazole), [Cu(MeNH2)3]+ and [Cu(MeNH2)4]+ , (2) neutral tripodal ligands [CuCH(ImH)3]+, [Cu(tren)]+ [where tren is tris(2-aminoethyl)amine], and [Cu(trenMe3)]+ [where trenMe3 is tris(2-methylaminoethyl)amine] and (3) a hydrido-tris(pyrazolyl)borate [CuBH(Pyra)3]. The structures of these complexes, the coordination mode ( η 2 side-on or η 1 end-on) of O2 to CuI and the charge transfer from the metal to dioxygen have been computed. For some systems, the coordination by CH3CN and CO is also reported. Beyond results relative to structural properties, an interesting feature is that it is possible to build from computational results only a set of abacuses linking the ν(16O–16O) vibrational frequency of the coordinated O2 molecule to the O–O bond length or to the net charge of the O2 moiety. Such abacuses may help experimentalists in distinguishing between the four possible ways of binding O2 to CuN3 and CuN4 cuprous centres, namely (1) end-on triplet states, (2) side-on triplet states, (3) end-on singlet states and (4) side-on singlet states. These abacuses are extended to three tripods obtained by the substitution of one nitrogen atom by either a phosphorus or a sulphur atom. Moreover, it is shown that any factor favouring pyramidalization at copper favours charge transfer and thus coordination of the incoming O2 moiety. All these allow insight into the coordination mode of O2 and into the charge transfer from CuI in site CuM of PHM. [ABSTRACT FROM AUTHOR]

By using quantum mechanical calculations, the most probable structure of the anionic complex species dodecabenzylbambus[6]uril–F− was derived. In this "asymmetrical" complex, the fluoride anion F−, included in the macrocyclic cavity, is bound by six weak C–H⋯F− hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the F− ion. The interaction energy, E(int), of the resulting anionic complex was found to be − 427.8 kJ mol−1, confirming also the formation of this complex species. [ABSTRACT FROM AUTHOR]

Stability and structure of complexes between silver (I) and l-methionine (L) deduced from potentiometric and 1H NMR measurements allow to assume the prevailing of several protonated species. The experimental data are compatible with the formation of the following complexes: AgL, AgL2, AgH2L, AgH1L2, AgH2L2, AgH3L2 and AgH4L2. The coordination sites are obtained by 1H NMR spectra, showing that only the bond between the methylthioether sulfur atom and silver (I) is responsible of the complex stability. The system is studied potentiometrically with silver and glass electrodes at 25 °C and 1.00 mol·dm−3 NaClO4 as ionic medium. Amino acids containing sulfur are few and not extensively studied. In particular, l-methionine, even if it is the most important, enantiomer and their complexes with silver (I) present anticarcinogenic properties, is quite not investigated. In the same experimental conditions, l-methionine protonation constants are determined. The 1H NMR data allow one to assume that, in moderately alkaline solution, silver (I) is bond with six membered chelate rings with sulfur and amino nitrogen, while carboxylic groups are not involved. No polynuclear species are present. The high stability of the complex with ratio 1:2 (silver (I)/l-methionine), involving also two hydrogen ions, predominating in a wide range of hydrogen ion concentration suggests to propose a study for the preparation of an electrode to measure the deprotonated l-methionine concentration. [ABSTRACT FROM AUTHOR]

Dihydroasparagusic acid is the first naturally occurring dimercaptanic compound that was isolated in 1948 from Asparagus concentrate. Although several synthetic procedures were proposed in the past decades for this natural substance, most of its chemical properties remain unstudied. In this work the capacity of the acid to act as an antidote against mercury(II) toxicity was evaluated in a simple biological model system, Saccharomyces cerevisiae, and is explained by the formation of a precipitate between mercury(II) and dihydroasparagusic acid. The precipitate was analyzed and studied. The solubility was determined by measuring in equilibrated solutions either the concentration of the total mercury(II) present in solution or the free concentration of hydrogen ions. The protonation constants were determined at 25 °C and in 1.00 M NaCl, as constant ionic medium, by means of potential difference measurements of a galvanic cell with a glass electrode. The experimental data are explained by proposing the chemical composition of the precipitate and the value of its solubility product. As the solubility of the precipitate increases by increasing the concentration of dihydroasparagusic acid, the further formation of a complex between mercury(II) and dihydroasparagusic acid is assumed. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The reaction of silver 4,4′-biphenyldicarboxylate with 1,3-diaminopropane (DAP) and 2-amino-5-methylpyridine (AMP) respectively results in the formation of two dinuclear silver(I) complexes: [Ag(DAP)](BPC)·2HO ( 1) and [Ag(BPC)(AMP)]·2HO ( 2), where BPC is 4,4′-biphenyldicarboxylate. The complexes are characterized by elemental analysis and X-ray crystallography. Complex 1 crystallizes in the triclinic system, P-1 space group, a = 8.585(2) Å, b = 8.849(2) Å, c = 9.890(3) Å, α = 107.893(3)°, β = 94.139(3)°, γ = 113.202(3)°, V = 640.9(3) Å, Z = 1. Complex 2 crystallizes in the triclinic system, P-1 space group, a = 11.818(3) Å, b = 13.132(4) Å, c = 13.281(4) Å, α = 92.571(4)°, β = 96.425(3)°, γ = 102.142(4)°, V = 1997.5(10) Å, Z = 2. Complex 1 consists of a macrocyclic dinuclear silver(I) dication, a 4,4′-biphenyldicarboxylate anion, and two water molecules of crystallization. Each Ag atom is in a linear coordination. Complex 2 consists of a dinuclear silver(I) complex molecule and two water molecules of crystallization. Each Ag atom is in a T-shaped coordination. The Ag...Ag separations are 5.127(2) Å in 1 and 3.172(2) Å in 2. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is an essential trace element for bacteria that is utilized in myriad metalloenzymes that directly couple to the biogeochemical cycling of nitrogen, sulfur, and carbon. In particular, Mo is found in the most common nitrogenase enzyme, and the scarcity and low bioavailability of Mo in soil may be a critical factor that contributes to the limitation of nitrogen fixation in forests and agroenvironments. To overcome this scarcity, microbes produce exudates that specifically chelate scarce metals, promoting their solubilization and uptake. Here, we have determined the structure and stability constants of Mo bound by protochelin, a siderophore produced by bacteria under Mo-depleted conditions. Spectrophotometric titration spectra indicated a coordination shift from a catecholate to salicylate binding mode for MoVI-protochelin (Mo-Proto) complexes at pH < 5. pKa values obtained from analysis of titrations were 4.8 ± 0.3 for MoVIO2H3Proto− and 3.3 ± 0.1 for MoVIO2H4Proto. The occurrence of negatively charged Mo-Proto complexes at pH 6 was also confirmed by mass spectrometry. K-edge Extended X-ray absorption fine structure spectroscopy confirmed the change in Mo coordination at low pH, and structural fitting provides insights into the physical architecture of complexes at neutral and acidic pH. These findings suggest that Mo can be chelated by protochelin across a wide environmental pH range, with a coordination shift occurring at pH < 5. This chelation and associated coordination shift may impact biological availability and mineral surface retention of Mo under acidic conditions. [ABSTRACT FROM AUTHOR]

Natural metal-organic complexes have gained much attention due to their self-assembly behaviors and photochemical properties. They perform various biological processes, including catalysis, anti-oxidation, molecular transport, and structural organization. Recently, the bio-inspired metal-phenolic complexes have been widely adopted as molecular scaffolds and redox-active molecules for the fabrication of functional materials. This review focuses on recent studies on the applications of metal-polyphenol complexes as bioinspired materials to build functional biomaterials possessing unique physical and chemical properties. Metal-phenolic coordination provides a simple fabrication route to complex and hierarchical structures as found in metal-ligand complexes in nature, leading to assembled supramolecular materials and robust interfaces of metal species with polyphenols. Furthermore, the metal-polyphenol chemistry features the versatile biochemical and structural functions of metal species through complexation with polyphenols as biocompatible ligands. This article is concluded with a discussion on the redox properties of metal-phenolic coordination potentially useful for biomedical applications. [ABSTRACT FROM AUTHOR]

The activity of the palladium salt catalysts was investigated on the benzaldehyde reactions with H2O2. The PdCl2 salt was the most efficient catalyst for the formation of the goal products. In CH3OH, benzaldehyde was selectively oxidized to benzoic acid and posteriorly esterified to methyl benzoate. In this process, the reaction of the PdCl2 catalyst with aqueous H2O2 provided H+ ions, which also promoted the esterification and acetalization reactions. The oxidant load played a key role in the selectivity controlling; while a large excess (9:1) gave benzoic acid (90%), with a lower ratio (3:1), acid and ester were formed with selectivity of 58 and 35%, respectively. With H2O2 at an equimolar ratio, the Pd(0) reduced the benzaldehyde to benzyl alcohol (30%). In absence of the oxidant, PdCl2 (2.5 mol %) condensated benzaldehyde and alcohol to acetal (90%). Therefore, PdCl2 directly catalyzed the oxidation and reduction reactions, and participated in acid-catalyzed reactions (i.e., condensation and esterification), generating H+ ions, demonstrating to be a highly versatile catalyst. An adequate adjusting of reaction conditions allowed to control the reaction selectivity toward the desired products (i.e., benzoic acid or ester benzyl, acetal, or benzyl alcohol). [ABSTRACT FROM AUTHOR]

Applying quantum chemical calculations, the most likely conformations of the anionic complex species dodecabenzylbambus[6]uril–PF6−, dodecabenzylbambus[6]uril–AsF6−, and dodecabenzylbambus[6]uril–SbF6− were found. In all these complexes, the considered anions, incorporated in the ligand cavity, are bound by hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units of the dodecabenzylbambus[6]uril ligand and fluorine atoms of the respective "central" anion. Moreover, the interaction energies of the investigated three anionic complexes were calculated. The absolute values of these calculated energies increase in the series of SbF6− < AsF6− < PF6−. [ABSTRACT FROM AUTHOR]

The calculations of bimetallic complexes of the type (X)[(Ind)M2(L)2] (M = Ni, Pd, L = CO, (PEt3) and X = Allyl, Cp and indenyl) have been done using two DFT functionals, namely BP86 and B3LYP*. The allyl, Cp and indenyl ligands adopt the same η3-coordination mode with a π bond and can be considered to be isolobal, while the chloride acts as σ- and π-donor. The computed structural and energetic parameters and energy decomposition yield chemically useful information. We report that the metal–metal bond distances are slightly sensitive to the electron donation and electron π-backdonation as the isolobal prediction suggests. Changing the metal from Ni to Pd has the result of increasing the metal–metal bond distance, decreasing the natural population of Pd and the weakness interactions between the X− ligand and the [(Ind)M2(L)2]+ fragment. The results showed that the four ligands behave quite similarly in terms of bonding, coordination mode and donation and π-backdonation properties highlighted by the orbitals' populations and the energy decomposition. However, the strength of interactions can be classified as follows: Cl < Cp ≈ Ind < Allyl. In all the complexes studied, the M22+ moiety adopts a single metal–metal bonding attributing the 16-MVE configuration to each M(I) cation. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) coated with whey peptides are shown to be a useful optical nanoprobe for the highly sensitive determination of Pd(II). The peptidic surface of the AgNPs works as a molecular receptor for the rapid detection of Pd(II) via a color change from dark yellow to orange/red along with a spectral red-shift with a gap about 120 nm. The effect is caused by the formation of a coordination complex between Pd(II) and the peptide ligands. This results in the aggregation of AgNPs and an absorbance spectral shift from 410 to 530 nm. The absorbance response is linear in the range 0.1 to 1.3 μM Pd(II) with a low detection limit of 115 nM. The nanoprobe responds within a few minutes and is not interfered by other metal ions except for Mg(II). The probe potentially can be applied to the determination of Pd(II) contamination in the products of Pd(II)−catalyzed organic reactions and in pharmaceutical settings. [ABSTRACT FROM AUTHOR]

Arginine and copper(II) play an important role in human physiology. Arginine is a precursor of NO which is a vasodilator and the right quantity of copper(II), bound to several amino acids, is necessary for the human body. The complex formation between copper(II) and arginine is studied at 25 °C and in two different ionic media: 1.00 mol dm−3 NaClO4 and 1.00 mol dm−3 NaCl. The investigation is carried out potentiometrically, by employing in 1.00 mol dm−3 NaClO4 cells involving glass and copper amalgam electrodes. In 1.00 mol dm−3 NaCl, only the glass electrode can be used. In both ionic media, the adoption of the constant ionic medium allows to extend the investigation to a large range of reagent concentration. Experimental data can be explained by assuming the formation of mononuclear complexes in copper(II). In 1.00 mol dm−3 NaClO4, complexes with the participation of hydrogen ions are assumed. The presence of the main complex in a large hydrogen ion concentration is supported also by spectrophotometric measurements. [ABSTRACT FROM AUTHOR]

Mn K-edge X-ray absorption spectroscopy experiments were performed on the solid- and solution-phase samples of [Mn(dpaq)](OTf) (R=H, Me) and [Mn(OH)(dpaq)](OTf). The extended X-ray absorption fine structure (EXAFS) data show distinct differences between the Mn and Mn-OH complexes, with fits providing metric parameters in excellent agreement with values from X-ray crystallography and density functional theory (DFT) computations. Evaluation of the EXAFS data for solid-phase [Mn(OH)(dpaq)](OTf) resolved a short Mn-OH bond distance of 1.79 Å; however, the short trans-amide nitrogen bond of the supporting ligand precluded the resolution of the Mn-OH bond distance in the corresponding solution-phase sample and for both [Mn(OH)(dpaq)](OTf) samples. The edge energy also increases by approximately 2 eV from the Mn to the Mn-OH complexes. Experimental pre-edge analysis shows the Mn complexes to have pre-edge areas comparable to the Mn-OH complexes, despite the presence of the relatively short Mn-OH distance. Time-dependent density functional theory (TD-DFT) computations illustrate that Mn 3 d-4 p mixing, a primary contributor to pre-edge intensities, decreases by ~ 0.3% from the Mn to Mn-OH complexes, which accounts for the very similar pre-edge areas. Collectively, this work shows that combined EXAFS and XANES analysis has great potential for identification of reactive Mn-OH intermediates, such as those proposed in enzyme active sites. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A capillary zone electrophoretic method has been developed for a separation of a reaction mixture of a rhenium complex. The rhenium complex was synthesized in a reaction of a rhenium precursor and 1,2,3-trihydroxybenzene in acetonitrile with triethylamine addition. The capillary electrophoretic method has been used for the separation in borate and phosphate buffer (pH 6.30-11.80). All components in the reaction mixture (unreacted precursor, ligand, and final rhenium complex) have been determined by capillary zone electrophoresis with UV-Vis detection in an aqueous running electrolyte within 10 min. Dependencies of effective electrophoretic ion mobility on the pH value have been determined for the ligand, unreacted precursor, and final complex in both electrolytes. Graphical abstract: [ABSTRACT FROM AUTHOR]

Cu(salpn), [salpn = N, N′-bis(salicylidene)-1,3-propanediimine], nanorods, and microtubes were successfully fabricated by template free hydro/solvothermal approach. Elemental analysis and FT-IR spectra confirmed the composition of Cu(salpn) complex and characteristic bands of this compound exactly. XRD pattern was well matched with X-ray diffraction simulated data. The SEM and TEM images revealed the nanorod morphology in hydrothermal process. The effect of various solvents (methanol, ethanol, 2-propanol, acetonitrile, and tetrahydrofuran) on the morphology of the products indicated that the microtubes Cu(salpn) just prepared in ethanol. Based on the growth process with respect to the morphological structure, the possible formation mechanism of Cu(salpn) nanocomplex has been proposed as a sequential two-step growth mechanism, heterogeneous complex nucleation, and directional growth processes. The nanorods of Cu(salpn) complex is the result of the faster growth rate along <001> direction. Probably, the dissolution-recrystallization process can proceed as favorable mechanism for microtube fabrication. Adjusting reaction times can selectively control the formation of microtubes and microrods. Graphical abstract: [ABSTRACT FROM AUTHOR]

Geometry optimizations have been performed on the M(Pyr) (M = Ti-Ni, Pd and Pt, Pyr = CH) complexes by means of DFT method using BP86 and mPW1PW91 functionals combined to the TZP basis set. The M moiety encapsulated between two pyrene ligands tends to establish M-L bonding with various hapticies from η to η. In accordance with the coordination modes, the pyrene behaves as neutral, dianionic, or tetraanionic ligand. For the Ti, V, and Fe, the low-spin (S = 0) and the high-spin (S = 1) structures are isoenergetic, while the Cr, Mn, and Co structures prefer the high-spin states. The Ni, Pd, and Pt structures are more favorable in low-spin state. The zigzag metallic chain is predicted to be more stable than that of the two-dimensional sheet for the Pd complexes. The spin state changes of the studied complexes in their ground states could be characterized in some cases by different molecular structure modifications (structural isomerisation, where structural modifications accompany the spin state modification like as bonds and angles), electronic configurations (low-spin or high-spin), or oxidation states with respect to the metal charges, in agreement with the metal nature. The optimized structures obtained by both BP86 and mPW1PW91 methods are consistent to each other, where the energetic parameters follow similar tendencies regarding the stability order between isomers. [ABSTRACT FROM AUTHOR]

A new mixed-valent Mn-Ln complex with an MnMnLa core $$ [{\text{Mn}}_{9}^{\text{III}} {\text{Mn}}_{2}^{\text{II}} {\text{La}}_{ 2} (\mu_{ 4} {-}{\text{O}})_{7} (\mu_{ 3} {-}{\text{O}})(\mu_{ 3} {-}{\text{OH}})_{ 2} ({\text{benzoate}})_{ 1 8} ({\text{NO}}_{3} )({\text{MeCN}})] $$ has been synthesized. Its magnetic characterization reveals a complex with dominating slow relaxation. In addition, alternating current (ac) susceptibility measurements reveal a frequency-dependent out-of-phase ( χ′′) signal below 4 K, suggesting the complex to be a single-molecule magnet. Graphical abstract: [ABSTRACT FROM AUTHOR]

N-Heterocyclic carbenes (NHCs) react readily with carbon disulfide to form stable, crystalline, zwitterionic adducts. In this review, we outline the various strategies that were applied to synthesize transition metal clusters based on such NHC·CS ligands. We also briefly survey their most salient structural features and catalytic properties. Because this research field is still in its infancy, only a limited number of structures containing metals from Group 7 (Mn and Re) and 8 (Fe and Ru) have been described so far. Homo- and heterobimetallic manganese and rhenium carbonyl clusters with the generic formula [MM′(CO)(μ-κ- S, S′-κ- S, C, S′-SC·NHC)] (MM′ = Mn, MnRe, or Re) were most thoroughly investigated. Isolated examples of dinuclear iron and tetranuclear ruthenium compounds, in which the dithiocarboxylate unit underwent fragmentation, were also reported. Other related polymetallic entities recently elaborated through the use of azolium-2-dithiocarboxylate zwitterions and Group 11 metals (Cu and Au) include copper-based coordination polymers, gold nanoparticles, and self-assembled monolayers. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Complexes of Er(III), Gd(III), and La(III) with (2 E,15 E)-2-[1-(2-aminophenyl)ethylidineamino]- N′-[1-(2-aminophenyl)ethylidene]benzoic acid hydrazide (AEBH) have been synthesized. The isolated complexes were characterized by elemental analyses, thermal analyses (TGA, DTA), IR, H NMR, C NMR, ES-MS, TEM, and conductance measurements. The results indicated that the ligand coordinates to La(III), Gd(III), and Er(III) in the keto form as neutral pentadentate ligand. The particle size and morphology have been determined by TEM. In vivo pharmacological evaluation of the synthesized compounds in collagen II-Freund's adjuvant model proved the presence of anti-inflammatory and analgesic activities of these compounds. Gd(III) complex showed higher effect in comparison with the well-known drug meloxicam. Graphical Abstract: [ABSTRACT FROM AUTHOR]

In the present work, a novel binuclear benzothiazole-oxime Pd(II) complex was synthesized, characterized (elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, nuclear magnetic resonance, and conductance measurements), and explored for its catalytic activity in Suzuki-Miyaura and Heck-Mizoroki cross-coupling reactions of different aryl- and heteroaryl halides with arylboronic acids and styrene, respectively, using the microwave irradiation conditions. The electronic arrangement, type of hybridization, and nature of bonding in the Pd-complex were investigated by natural bond orbital analysis. Time-dependent density functional theory calculations were carried out to understand the electronic transitions in the related experimental observations. Graphical abstract: [ABSTRACT FROM AUTHOR]

A high yield preparation, spectroscopic and crystallographic investigation of the crystalline Zn-complex of a di( β, β′-sulfoleno)pyrrin are reported here. In the brightly green fluorescent Zn-complex of the hardly luminescent di( β, β′-sulfoleno)pyrrin, the metal ion is bound by two di( β, β′-sulfoleno)pyrrin ligands, as revealed first by its mass spectra. The crystal structure of this Zn-complex of the di( β, β′-sulfoleno)pyrrin confirmed a regular 2:1 composition of the bidentate di( β, β′-sulfoleno)pyrrin ligand and the metal ion. The latter was coordinated in a distorted tetrahedral fashion, as found in other dipyrrin Zn-complexes. The here studied Zn-complex of a designed di( β, β′-sulfoleno)pyrrin ligand provides insights into the coordination properties of the proposed (2:1)- and (2:2)-complexes of phylloxanthobilin and bilirubin, respectively, which are two abundant natural bilin-type tetrapyrroles. Graphical abstract: [ABSTRACT FROM AUTHOR]

The synthesis of novel, homoleptic group 13 alkoxides is presented. M(OCH(CHNR)), where M=Al, Ga, In and R=Me, Et, are characterised by room temperature NMR spectroscopy and single-crystal XRD showing the monomeric nature of all aminoalcoholates. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report on a highly sensitive and remarkably selective fluorometric assay for mercury(II) ion. It is based on the formation of a complex between thymine (T) and Hg(II) to form the [Hg(T)(HO)] complex on the surface of reduced graphene oxide (rGO). This causes the fluorescence emission of rGO (peaking at 550 nm) to be quenched. Under optimal conditions, quenching is selective and fluorescence intensity is linearly related to the concentration of Hg(II) in the range between 100 and 700 nM. The limit of detection is 5 nM. In addition to its sensitivity and selectivity, the method is simple and direct. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Amphiphilic bifunctional phthalocyanine (Pc) derivatives (protonated compound: EO-HPc and copper(II) complex: EO-CuPc) having methylhexaethylene oxide (EO: -O(CHCHO)-CH) have been synthesized. Dimerization equilibria of EO-HPc in alcohols and complex formation with alkali metal ion (Li, Na, and K) in methanol have been studied by means of absorption and fluorescence spectrophotometry. EO-HPc in methanol exists predominantly as a dimer, (EO-HPc). By the reaction with alkali metal hydroxide, the dimer dissociates to monomer and forms complexes at the Pc moiety and/or EO moiety. Lithium ion is captured inside the cavity of the Pc ring and forms a stable complex, EO-LiPc. Sodium ion and potassium ion, the ion sizes of which are larger than the cavity size of Pc, form 'sitting a top' (SAT) complex, that is, the metal ion in the complex with Pc moiety is located on the outside of the Pc ring. By the reaction with NaOH, sodium ion is inserted between the dimeric Pc ring, (EO-NaPc) at the first step, then forms a monomeric 1:1 complex, EO-NaPc. In the case of reaction with KOH, the monomeric complex, in which potassium ion is coordinated at the EO moiety, (KEO)HPc, is formed as the first step. Then, the Pc moiety coordinates to the potassium ion, (KEO)-KPc. The structures of complexes were confirmed by the reaction of EO-CuPc. The order of stability of alkali metal ion complex is obtained as Li > > Na > K for Pc moiety and Li < Na < < K for EO moiety. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

As a result of systematic UV-Vis absorption spectroscopy studies in the U(VI) acetate system, the single component spectrum of [UOCHCOO] with characteristic parameters was evaluated and applied in quantitative deconvolution of multicomponent spectra. Free acetate concentrations were obtained by the use of geochemical and probabilistic modelling codes. A total of 51 UV-Vis spectra were collected in a wide range of experimental conditions where coordination of U(VI) by acetate ion was indicated by characteristic variations in the spectra structure as compared to UO. Using chemometric data analysis, the resulting factor structure was evaluated to obtain a subset of 14 spectra holding only one coordinated species next to UO. The molar absorption coefficient for the U(VI) monoaceto species was estimated as ε = 17.8 ± 1 dm mol cm. Spectral deconvolution was used to obtain an estimate of the species concentrations which allowed to calculate for each sample the free acetate concentration, the total U(VI) amount and, eventually, to estimate the formation quotient lg β = 2.8 ± 0.3 of UO(CHCOO). Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Arginine and zinc(II) play an important role in the human physiology. Arginine is a precursor of NO which is a vasodilator and zinc(II) is frequently an enzyme activator having also therapeutic role. The complex formation between zinc(II) and arginine is studied, at 25 °C and in 1.00 mol dm NaCl as ionic medium. The investigation is carried out potentiometrically, by employing cells involving glass and zinc amalgam electrodes, in a large range of reagent concentration. Experimental data can be explained by assuming the formation of mononuclear complexes in zinc(II), but with the participation of hydrogen ions. The formation of the following species with the relative stability constant explains the experimental data: ZnHL (log β = 16.11 ± 0.07), ZnHL (log β = 33.41 ± 0.05), ZnHL (log β = 45.93), ZnHL (log β = 36.04), and ZnHL(log β = 27.15), where L represents the completely deprotonated arginine. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Single crystals of 1-methylpiperazine-1,4-diium hexaaquatetrachlorodinickel(II) dichloride, (CHN)[NiCl(HO)]Cl, were grown by hydrothermal techniques in aqueous solution. The compound was characterised by differential thermal analysis (TG-TDXD), single crystal X-ray diffraction, and variable temperature magnetic susceptibility. The compound crystallizes in the triclinic system (space group P-1, Z = 2) with the following unit cell dimensions: a = 6.611(3) Å, b = 8.776(4) Å, c = 17.457(8) Å, α = 101.34(2)°, β = 96.31(2)°, and γ = 105.38(2)°. The structure was solved using 4,243 independent reflections and refined to R = 0.024. The structure of (CHN)[NiCl(HO)]Cl can be described as mixed organic-inorganic layers along the [−101] direction. The Ni dimers show ferromagnetic exchange ( J ~ 15 K), while the interactions between the dimers are antiferromagnetic ( J ~ −3 K). The 3D network is further linked by three types of hydrogen bonds (N-H···Cl, OW-H···Cl, and N-H···O), in order to build cation-anion cohesion. Dehydration of the precursor proceeds through three stages, leading to crystalline intermediary hydrate phases and an anhydrous compound. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Oxidovanadium(IV) bispicolinato compounds with dimethyl sulfoxide (DMSO), pyridine, 4-aminopyridine, 4-(dimethylamino)pyridine, and imidazole were prepared and their crystal structures determined. The coordination of VO(IV) is octahedral with the neutral ligand in cis position to the V=O moiety. X-ray crystallographic studies revealed different arrangements of the ligands around the vanadium metal center. The DMSO adduct presents the first crystallographic evidence of VO(IV) picolinato complexes with a nitrogen atom occupying the axial position trans to the V=O, leading to a geometry with both oxygen atoms from the picolinato ligands in cis position to the V=O and trans to each other. On the other hand, the compounds with N-ligands have an arrangement similar to some known structures with one carboxylic group in trans position to the V=O moiety. Quantum-mechanical calculations were performed on six possible isomers of DMSO and pyridine adducts, and their energy differences were studied. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

New square-planar Pd(II) and Pt(II) complexes with 8-quinolinecarboxaldehyde selenosemicarbazone have been synthesized and characterized by use of elemental analysis, molar conductivity measurements, and IR and NMR spectroscopy. The cytotoxic activity of the ligand, new Pt(II) and Pd(II) compounds, and previously synthesized Pd(II), Pt(II), Cd(II), and Ni(II) complexes with the analogous ligand, 2-quinolinecarboxaldehyde selenosemicarbazone, was tested against two human cancer cell lines: lung carcinoma (H460) and glioma (U251). The potential of these compounds to induce perturbations of the H460 cell cycle was also evaluated. These substances had an excellent radical-scavenging effect against ABTS radical cations. The best antimicrobial activity, among two yeasts and eight bacterial strains tested, was against Bacillus cereus. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The reaction of an isomeric mixture of [Co(dien)]Cl with sodium salt of p-aminobenzoic acid in aqueous medium leads to the formation of dark orange coloured crystals of composition s- fac-[Co(dien)]Cl( p-aminobenzoate)·3HO. The configuration of the cationic isomer was initially determined with the help of spectroscopic data (NMR, UV-Vis, and IR). The binding properties of s- fac-bis(diethylenetriamine)cobalt(III) cation with p-aminobenzoate anion has been determined (in solution phase) with the help of UV-Vis spectroscopic titrations. Single crystal X-ray structure determination of title complex reveals the presence of one cation, three anions (one Cl and two p-aminobenzoates) along with three lattice water molecules. The crystal lattice is stabilized by electrostatic forces of attraction and H-bond interactions (N-H···O, N-H···Cl, O-H···O, and O-H···Cl). The water molecules of crystallization play a major role in stabilizing the complex by forming intermolecular H-bonds with Cl and O atoms of p-aminobenzoate and water. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This study reports the synthesis of novel mixed ligand complexes of copper(II) with the xanthurenate anion (Xan) and nicotinamide ligand (NA): [Cu(Xan)(NA)(HO)]·HO and [Cu(Xan)(NA)(HO)]·3HO. The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. The first coordination sphere of copper(II) in [Cu(Xan)(NA)(HO)] consists of a water molecule, a nicotinamide ligand coordinated via the pyridine nitrogen and a xanthurenate dianion coordinated in a tridentate manner via carboxylate oxygen, nitrogen, and phenolate oxygen. The five donor atoms define a distorted square pyramid whose apex is occupied by the aqua ligand. The antioxidant activities of the compounds were investigated by the 2,2-diphenyl-1-picrylhydrazyl scavenging method, which showed that the IC values for both compounds are higher than for related [Cu(Xan)(HO)] complex. The title compounds also exhibit superoxide dismutase mimetic activity. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A family of new iridium phosphine-sulfonate complexes based on 2-dicyclohexylphosphino-4-benzenesulfonic acid was synthesized and characterized. An iridium(I) phosphine-sulfonate cyclooctadiene species was prepared from transmetalation of a silver salt of the phosphine-sulfonate ligand and iridium(I) cyclooctadiene chloride dimer. This diolefin iridium complex was found to be a functional precatalyst for cyclopentene hydrogenation. A corresponding iridium(I) phosphine-sulfonate dicarbonyl species was prepared by ligand substitution using carbon monoxide. Analysis by infrared spectroscopy established this metal-ligand platform as a relatively electron poor coordination environment. The iridium(I) phosphine-sulfonate cyclooctadiene species was further utilized as a precursor for the synthesis of two iridium(III) phosphine-sulfonate hydride compounds by treatment with strong acids. [ABSTRACT FROM AUTHOR]

X-ray crystal structure determination at 200 K revealed that NHCdF crystallizes in the orthorhombic space group Pnam, with unit cell dimensions a = 1,421.0(2), b = 694.29(11), c = 447.52(7) pm. The structure consists of NH cations and double Cd-F chains interconnected by a hydrogen bonding network. The N-N stretching vibration in NHCdF is active in infrared and Raman spectroscopy with an N-N stretching infrared band at 1,002 cm and a Raman band at 1,008 cm. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

( E, E′, E′′, E′′′)- N, N′, N′′, N′′′-[(1,2-ethenyliden)tetrakis[methylenoxy(2,1-naphthalinediyl)methylidyne]tetrakis[1,2,4-triazol-4-amine] and its novel homo-dinuclear Mn(II), Ni(II), Cu(II), and Zn(II) complexes have been synthesized and characterized by elemental analyses, spectroscopic data (i.e., IR, H and C NMR, UV-Vis), electrospray ionisation mass spectra, XRD, DSC, molar conductivity, and magnetic susceptibility measurements. The absorption bands observed in the electronic spectra and magnetic moment values confirm an octahedral environment around the metal ion. The molar conductivity measurements confirm the non-ionic character of these complexes. The DNA cleavage activities of the Schiff base and its homo-dinuclear complexes are also investigated. Results suggest that all the complexes used can be evaluated as nuclease mimics. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This contribution reports the results of potentiometric and Mössbauer investigations on the formation, stability, and structure of binary and ternary mono- and binuclear complexes of Sn with three hydroxocarboxylic ligands (namely L = tartrate, malate, and citrate) and chloride at T = 298.15 K in different ionic media and ionic strengths (0.15 and 1.00 mol dm in NaCl and 1.00 mol dm in NaNO). The stability constants of various simple SnHL and mixed SnHLCl species obtained in the different experimental conditions are reported, and various speciation diagrams of the simple and mixed systems are shown in different conditions. The sequestering ability of the three ligands toward Sn was assessed by means of the calculation of the pL parameter at different ionic strengths and in the different ionic media. The effect of the chloride anion on the stability of various species and on the sequestering ability of the investigated ligands toward Sn was also evaluated. The structural results obtained by Mössbauer spectroscopy supported the speciation schemes obtained by the potentiometric investigations and indicated the possible trigonal bipyramidal arrangement of various Sn/ligand species. Measurements at different temperatures were also performed in the case of citrate, in order to estimate the temperature dependence of the stability of these species. A modified version of the computer program STACO is briefly presented here for the first time and allows the simultaneous determination of the stability constants and the enthalpy changes of various species from potentiometric titrations at different temperatures. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Recently, we described the first inverse electron demand Diels-Alder reaction of 1,2-diazene catalyzed by a bidentate Lewis acid. Herein we investigate 1,2-phenylenediboronic esters as potential catalysts for this transformation offering higher stability and easier handling than the currently used boranthracene derivatives. Different 1,2-phenylenediboronic esters were prepared and their ability to form bidentate coordination complexes with phthalazine was analyzed. Although a 1:1 complex was observed, X-ray analysis revealed binding only in a monodentate fashion. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Copper(II) bis(pentane-2,4-dionato-κ O, O′) compounds with 2-pyridone ( 1) and 3-hydroxypyridine ( 2) were prepared by the reaction of bis(pentane-2,4-dionato-κ O, O′)copper(II) with selected ligands. The coordination of Cu(II) in both compounds is square pyramidal with the fifth coordination site occupied by the carbonyl oxygen atom of the 2-pyridone ligand in 1 and by the nitrogen atom of 3-hydroxypyridine in 2. The X-ray crystallographic studies revealed different crystal aggregation influenced by the ability of the 2-pyridone ligand to act as a hydrogen bond donor and acceptor, and 3-hydroxypyridine acting only as a hydrogen bond donor. Intermolecular N-H···O hydrogen bonding forms dimers in 1 and infinite chains in 2. Three-dimensional aggregation is achieved by π-π interactions and C-H···π (arene) hydrogen bonding. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The coordination cage of the metal center in Fe(II)-bleomycin has been proposed to consist of the secondary amines in β-aminoalanine, the pyrimidinylpropionamide and imidazole rings, and the amide nitrogen in β-hydroxyhistidine as equatorial ligands, and the primary amine in β-aminoalanine and either the carbamoyl group in mannose or a solvent molecule occupying the axial sites. With the aim of supporting or not supporting coordination of a water molecule to the metal center in Fe(II)-bleomycin, the solution structure of Fe(II)-azide-bleomycin has been derived from NMR data. The structural changes that occur in Fe(II)-bleomycin upon azide binding have been monitored by comparing the experimental results with those obtained from the calculated structures for both bleomycin adducts. The results of this investigation strongly support a model of Fe(II)-bleomycin with six endogenous ligands as the most likely structure held in solution by this metallobleomycin in the absence of DNA. [ABSTRACT FROM AUTHOR]

Supramolecular reactions between crystalline materials can be exploited to prepare both hydrogen bonded co-crystals and coordination networks. Mechanical mixing of molecular crystals as well as kneading provide an alternative, solvent-free, route to novel materials hence these methods represent a green route to supramolecular solid-state chemistry. [ABSTRACT FROM AUTHOR]

Schiff base metal complexes are a class of compounds that have been studied extensively because of their attractive chemical and physical properties, and their wide-ranging applications in numerous scientific areas. Researchers have incorporated Schiff base complexes into polymers, generating new materials with useful mechanical, thermal, chemical, and electronic properties. This work comprehensively reviews the developments in macromolecules containing Schiff base metal complexes, emphasizing new synthetic strategies and characterization techniques that were used to prepare and study these polymers. [ABSTRACT FROM AUTHOR]

The cobalt(III) complex salt [(C4H9)4N][ trans-Co(NH3)2(NO2)4] has been synthesized in high yield by reacting equimolar quantities of [(C4H9)4N]Br and K[ trans-Co(NH3)2(NO2)4] in aqueous medium at room temperature. The product thus formed has been re-crystallised from acetone-water mixture, in the monoclinic space group P 21/ n, with cell dimensions a=11.651(3) Å, b=19.005(4) Å, c=11.733(5) Å, β=90.28(3)°. The X-ray structure determination revealed the presence of discrete ions, [(C4H9)4N]+ and [ trans-Co(NH3)2(NO2)4]−. The central metal ion cobalt(III) in the anion is found in octahedral environment, in trans geometry, while the organic counterion is a quaternary alkylammonium cation. The crystal lattice is stabilized by electrostatic interactions between the cations and anions. [ABSTRACT FROM AUTHOR]

The title compound was synthesized by mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride and sodium 4-aminobenzoate in aqueous medium in 1:3 molar ratio and recrystallizing the product obtained, from hot water. Elemental analyses and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR) were used for characterizing the complex salt. X-ray structure determination revealed an ionic structure consisting of [Co(en)2(C7H6NO2)2]+ cation, (C7H6NO2)− anion and four lattice water molecules. The complex salt crystallizes in the triclinic space group P $$ {\rm \bar 1} $$ with cell dimensions a = 9.985(1) Å, b = 11.522(1) Å, c = 14.233(1) Å, α = 80.20(1)∘, β = 72.80(1)∘, γ = 86.43(1)∘, Z = 2, V = 1541.3(2) Å3, R1 = 0.0291, and wR2 = 0.0751. [ABSTRACT FROM AUTHOR]

The new crystalline compound of catena- μ-chloro-bis(acetonitrile)copper(I) [(H3CCN)2 CuCl]∞ has been synthesized and structurally characterized by X-ray crystallography. The compound is an infinite polymeric chain in which chlorides bridge the coppers. Copper exhibits tetrahedral coordination geometry with two acetonitrile molecules acting as coordinating ligands. The compound crystallizes in the orthorhombic Pbcm space group with a = 12.585(3) Å, b = 7.496(2) Å, and c = 7.275(2) Å. [ABSTRACT FROM AUTHOR]

Reaction of tetramethoxysilane or tetramethoxygermane with salicylic acid and morpholine (molar ratio 1:3:2) in tetrahydrofuran yielded morpholinium mer-tris[salicylato(2–)-O1,O3]silicate( mer -5) and morpholinium mer-tris[salicylato(2–)-O1,O3]germanate ( mer- 8), respectively. Treatment of tetramethoxysilane with 5-chlorosalicylic acid and piperidine (molar ratio 1:3:2) in tetrahydrofuran afforded piperidinium mer-tris[5-chlorosalicylato(2–)-O1,O3]silicate–ditetrahydrofuran ( mer- 6·2THF). Triethylammonium mer-tris[3-methylsalicylato(2–)-O1,O3]silicate ( mer- 7) was obtained analogously by reaction of tetramethoxysilane with three molar equivalents of 3-methylsalicylic acid and two molar equivalents of triethylamine in dichloromethane/diethyl ether. The racemic compounds mer- 5, mer- 6· 2THF, mer- 7, and mer- 8 were characterized by elemental analyses (C, H, N), single-crystal X-ray diffraction, as well as solid-state (29Si) and solution(1H, 13C, 29Si) NMR studies. The structural characterizationwas complemented by computational studies (HF studies, TZVP level) of the fac- and mer-tris[salicylato(2–)-O1,O3]silicatedianion. In addition, the behavior of mer- 7 in solution was studied by VT 1HNMR experiments. [ABSTRACT FROM AUTHOR]

The reaction of dinuclear rhodium(I) derivatives of the formula [Rh( DIOL) X]2 with the axially chiral phosphinyl phosphane 2-(diphenylphosphinyl)-2′-(diphenylphosphanyl)-1,1′-binaphthalene (( S)- BINAPO, 1) leads to the formation of cationic complexes [( BINAPO)Rh( DIOL)]+ where the ligand ( S)- BINAPO consistently displays a P,O-chelate coordination which is mantained even in solvents of fair polarity. The mononuclear rhodium(I) complexes ( S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,5-cyclooctadiene) rhodium tetrafluoroborate ( 3b) and ( S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,4-norbornadiene) rhodium tetrafluoroborate ( 3c) with 1,5-cyclooctadiene ( COD) and 2,5-norbornadiene ( NBD) as the diolefin were isolated and characterized. Both show a fluxional behaviour in solution which is due to the mobility of the diolefin rather than to a displacement-recombination of the oxygenated arm of the ligand. The mobility of the 1,4-norbornadiene ligand in 3c is extremely pronounced and the coordinated diolefin flexibility could be frozen only at about 200 K. These complexes are active but poorly stereoselective catalysts for the hydrogenation, hydroboration, and hydroformylation of alkenes. [ABSTRACT FROM AUTHOR]