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Bio-based poly(lactic acid) (PLA) composite films were produced using unmodified soda micro- or nano-lignin as a green filler at four different contents, between 0.5 wt% and 5 wt%. The PLA–lignin composite polymers were synthesized by solvent casting to prepare a masterbatch, followed by melt mixing. The composites were then converted into films, to evaluate the effect of lignin content and size on their physicochemical and mechanical properties. Differential scanning calorimetry (DSC), supported by polarized light microscopy (PLM), infrared spectroscopy (FTIR-ATR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to investigate the PLA crystallization and the interactions with Lignin (L) and Nanolignin (NL). The presence of both fillers (L and NL) had a negligible effect on the glass transition temperature (chain diffusion). However, it resulted in suppression of the corresponding change in heat capacity. This was indicative of a partial immobilization of the PLA chains on the lignin entities, due to interfacial interactions, which was slightly stronger in the case of NL. Lignin was also found to facilitate crystallization, in terms of nucleation; whereas, this was not clear in the crystalline fraction. The addition of L and NL led to systematically larger crystallites compared with neat PLA, which, combined with the higher melting temperature, provided indications of a denser crystal structure in the composites. The mechanical, optical, antioxidant, and surface properties of the composite films were also investigated. The tensile strength and Young’s modulus were improved by the addition of L and especially NL. The UV-blocking and antioxidant properties of the composite films were also enhanced, especially at higher filler contents. Importantly, the PLA–NL composite films constantly outperformed their PLA–L counterparts, due to the finer dispersion of NL in the PLA matrix, as verified by the TEM micrographs. These results suggest that bio-based and biodegradable PLA films filled with L, and particularly NL, can be employed as competitive and green alternatives in the food packaging industry.

In this work, we assessed the electronic structures of two pseudotetrahedral complexes of FeII, [Fe{(SPiPr2)2N}2] (1) and [Fe{(SePiPr2)2N}2] (2), using high-frequency and -field EPR (HFEPR) and field-dependent 57Fe Mossbauer spectroscopies. This investigation revealed S = 2 ground states characterized by moderate, negative zero-field splitting (zfs) parameters D. The crystal-field (CF) theory analysis of the spin Hamiltonian (sH) and hyperfine structure parameters revealed that the orbital ground states of 1 and 2 have a predominant dx2-y2 character, which is admixed with dz2 (∼10%). Although replacing the S-containing ligands of 1 by their Se-containing analogues in 2 leads to a smaller |D| value, our theoretical analysis, which relied on extensive ab initio CASSCF calculations, suggests that the ligand spin-orbit coupling (SOC) plays a marginal role in determining the magnetic anisotropy of these compounds. Instead, the dx2-y2β → dxyβ excitations yield a large negative contribution, which dominates the zfs of both 1 and 2, while the different energies of the dx2-y2β → dxzβ transitions are the predominant factor responsible for the difference in zfs between 1 and 2. The electronic structures of these compounds are contrasted with those of other [FeS4] sites, including reduced rubredoxin by considering a D2-type distortion of the [Fe(E-X)4] cores, where E = S, Se; X = C, P. Our combined CASSCF/DFT calculations indicate that while the character of the orbital ground state and the quintet excited states' contribution to the zfs of 1 and 2 are modulated by the magnitude of the D2 distortion, this structural change does not impact the contribution of the excited triplet states.

A proxy-based high-throughput experimental approach was used to explore the stability and activity of Co-based Fischer-Tropsch Synthesis catalysts with different promoters on a variety of supports. The protocol is based on XRD estimation of the active phase polymorph, particle size and ratio of crystalline phases of Co to support. Sequential sample libraries enabled exploration of four Co loadings with five different promoters on six support materials. Catalysts stable to aging in syngas, i.e. displaying minimal change of particle size or active phase concentration, were evaluated under industrial conditions. This procedure identified SiC as a support that confers catalyst stability and that a combination of Ru and Hf promotes the stabilisation of hcp Co. Unsupported bulk samples of Co with appropriate amounts of Ru and Hf revealed that the formation of hcp Co is independent of the support. The hcp Co-containing catalyst afforded the highest catalytic activity and C5+ selectivity amongst the samples tested in this study, confirming the effectiveness of the proxy-based high-throughput method.

The high-spin S = 2 Mn(III) complex [Mn{(OPPh2)2N}3] (1Mn) exhibits field-induced slow relaxation of magnetization (Inorg. Chem.2013, 52, 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter D. In order to explore the magnetic and electronic properties of 1Mn in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (1Mn/1Ga) of 1Mn in the diamagnetic gallium analogue, [Ga{(OPPh2)2N}3], indicates that the slow relaxation behavior of 1Mn is due to the intrinsic properties of the individual molecules of 1Mn. Investigation of the single-crystal magnetization of both 1Mn and 1Mn/1Ga by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and -field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms (D and E), fourth-order terms (B4m) are required in order to appropriately describe the magnetic properties of 1Mn. These studies provide accurate spin-Hamiltonian (sH) parameters of 1Mn, i.e., zfs parameters |D| = 3.917(5) cm-1, |E| = 0.018(4) cm-1, B04 = B42 = 0, and B44 = (3.6 ± 1.7) × 10-3 cm-1 and g = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of D. Parallel-mode X-band EPR studies on 1Mn/1Ga and CH2Cl2 solutions of 1Mn probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of 1Mn is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of D are obtained. The calculations provide also computed values of the fourth-order zfs terms B4m, as well as those of the g and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of 1Mn are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field.

The photocatalytic oxidation (PCO) of pollutants using TiO2-based materials can significantly improve indoor air quality (IAQ), which in turn, has a significant impact on human health and life expectancy. TiO2-based nanoparticles (NPs) are widely used as part of building materials to function as photocatalysts in PCO. In this work, a series of sulfur-doped TiO2 NPs immobilized on a silica matrix were synthesized by combining a sol-gel process with ball milling. The samples were structurally characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR) and N2 adsorption-desorption isotherms. Furthermore, the morphological characteristics were determined by dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic activity of the as prepared S-doped TiO2/SiO2 NPs in the degradation of liquid and air pollutants under visible-light irradiation was investigated. Our results show that sulfur is an effective dopant for activating TiO2/SiO2 photocatalysts under visible-light irradiation. Silica constitutes a “safe-by-design” approach and inhibits the aggregation of NPs during synthesis. The most efficient photocatalyst afforded 79% removal of methyl orange (5 h), 26% removal of acetaldehyde (1 h) and 12% oxidation of NO (1 h).

Conversion of 5-hydroxymethylfurfural (HMF) in water to the linear diketone derivatives 1-hydroxyhexane-2,5-dione (HHD) and 2,5-hexanedione (HXD) was investigated over a series of Beta zeolite-supported transition metal catalysts (Co, Ni, Cu, Ru, Pd). Their catalytic performance was tested in a batch stirred reactor (T = 110 °C, PH2 = 20 bar) with Pd showing the highest activity and selectivity to HHD and HXD. The effects of Pd particle size, zeolite Si/Al ratio and reaction conditions (T = 80–155 °C, PH2 = 5–60 bar) were also investigated. The incorporation of Pd into Beta zeolite by the deposition-coprecipitation method produced the most efficient catalyst, affording complete HMF conversion (T = 110 °C, PH2 = 60 bar) predominantly to HHD (68% selectivity) and HXD (8% selectivity). The combination of a bifunctional acid/redox solid catalyst and water enhances the hydrolytic ring-opening and subsequent hydrogenation of the furan ring. Catalytic activity can be partially restored by a simple regeneration treatment. This work establishes a catalytic route to produce valuable diketone derivatives from renewable furanic platform sources in water.

In this work, we assessed the electronic structures of two pseudotetrahedral complexes of Fe

A proxy-based high-throughput experimental approach was used to explore the stability and activity of Co-based Fischer Tropsch Synthesis catalysts with different promoters on various supports. The protocol is based on the estimation by XRD of active phase, Co, particle size and relative amounts of crystalline phases, Co to support. Sequential libraries samples enabled exploration of four Co loadings with five different promoters on six support materials. Catalysts stable to aging in syngas, displaying minimal change of particle size or relative area, were evaluated for their activity under industrial conditions. This procedure identified SiC as support for stable catalysts and a combination of Ru and Hf to promote the formation hcp Co. Unsupported bulk samples of Co with appropriate amounts of Ru and Hf revealed that the formation of hcp Co is independent of the support. The hcp Co containing catalyst presented the highest catalytic activity and C5+ selectivity amongst the samples tested in this study confirming the effectiveness of the proxy-based high-throughput method.

The high-spin

Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL‐101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non‐functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well‐defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.

The synthesis and catalytic properties in Kumada C C coupling of the [Ni(BIPHEP)X2] complexes, X = Cl (1), Br (2), are described. The crystal structures of the BIPHEP ligand and 2 are also presented and compared with previously reported crystal structures of atropisomeric bidentate phosphine ligands (P,P) and related [M(P,P)X2] complexes (M = Ni, Pd, Pt). BIPHEP crystallizes in the C2/c space group, with both enantiomers present in the unit cell. This is consistent with BIPHEP being a “tropos” ligand. Complex 2 crystallizes in the P21/a space group. There are two symmetry-independent molecules in the asymmetric unit, namely 2a and 2b, in which the BIPHEP ligand adopts the S or the R configuration, respectively. Complexes 2a and 2b exhibit a severely tetrahedrally-distorted square planar NiP2Br2 coordination sphere, with a PNiP bite angle of 93.3° and 94.7°, respectively. The observed catalytic behavior of complexes 1 and 2 in the Kumada coupling between p-tert-butyl-halogenobenzene and p-tolylmagnesium chloride is benchmarked against that of [Ni(dppp)Cl2], dppp = 1,3-bis(diphenylphoshpino)propane. However, all three complexes are catalytically inactive in the Suzuki-Miyaura coupling reaction.

The production of cyclopentanone derivatives from 5-hydroxymethylfurfural (HMF) using non-noble metal based catalysts is reported for the first time. Five different mixed oxides containing Ni, Cu, Co, Zn and Mg phases on an Al-rich amorphous support were prepared and characterised (XRD, ICP, SEM, TEM, H2-TPR, NH3/CO2-TPD and N2 sorption). The synthesised materials resulted in well-dispersed high metal loadings in a mesoporous network, exhibiting acid/base properties. The catalytic performance was tested in a batch stirred reactor under H2 pressure (20–50 bar) in the range T = 140–180 °C. The Cu–Al2O3 and the Co–Al2O3 catalysts showed a highly selective production of 3-hydroxymethylcyclopentanone (HCPN, 86%) and 3-hydroxymethylcyclopentanol (HCPL, 94%), respectively. A plausible reaction mechanism is proposed, clarifying the role of the reduced metal phases and the acid/basic sites on the main conversion pathways. Both Cu–Al2O3 and Co–Al2O3 catalysts showed a loss of activity after the first run, which can be reversed by a regeneration treatment. The results establish an efficient catalytic route for the production of the diol HCPL (reported for the first time) and the ketone HCPN from bio-derived HMF over 3d transition metals based catalysts in an environmental friendly medium such as water.

The reaction of i Pr 2 P(O)NHP(O) i Pr 2 with CoCl 2 ∙ 6H 2 O affords simultaneously the neutral tetrahedral [Co[ i Pr 2 P(O)NHP(O) i Pr 2 - O,O ′]Cl 2 ] and the ionic octahedral [Co[ i Pr 2 P(O)NHP(O) i Pr 2 - O,O ′] 3 ][CoCl 4 ] complexes. These Co (II) complexes, which are stable towards oxidation to Co (III) species, self-assemble via N-H···Cl hydrogen bonds into a “honeycomb” (6,3) network. The structural flexibility of i Pr 2 P(O)NHP(O) i Pr 2 that can accommodate both tetrahedral and octahedral geometries is discussed.

The catalytic response of Ni on Al2O3 obtained from Ni-Al layered double hydroxides was studied for the liquid-phase hydrogenation of hydroxymethyl furfural to tetrahydrofuran-2,5-diyldimethanol (THFDM) in water. The successive calcination and reduction of the precursors caused the removal of interlayer hydroxyl and carbonate groups and the reduction of Ni(2+) to Ni(0). Four reduced mixed oxide catalysts were obtained, consisting of different amount of Ni metal contents (47-68 wt%) on an Al-rich amorphous component. The catalytic activity was linked to Ni content whereas selectivity was mainly affected by reaction temperature. THFDM was formed in a stepwise manner at low temperature (353 K) whereas 3-hydroxymethyl cyclopentanone was generated at higher temperature. Coke formation caused deactivation; however, the catalytic activity can be regenerated using heat treatment. The results establish Ni on Al2O3 as a promising catalyst for the production of THFDM in water.

The synthesis and spectroscopic characterization of [Rh{R2P(S)NP(S)R2-S,S′}(cod)] [cod = 1,5-cyclooctadiene; R = Ph (1), iPr (4)], [Rh{Ph2P(S)NP(S)Ph2-S,S′}(CO)2] (2) and [Rh{Ph2P(S)NP(S)Ph2-S,S′}(CO)(PPh3)] (3) is described. The crystal structures of complexes 1 and 3 are also presented. The synthesized RhI complexes are essentially not catalytically active against olefin hydroformylation, in contrast to the previously reported complex [Rh{Ph2P(O)NPPh2-P,O}(CO)(PPh3)] (6). Differences in the catalytic activity were interpreted with the aid of a well-defined DFT-based protocol involving relativistic effects and dispersion correction. The steric and electronic effects of the RhI coordination environment with respect to their activation by H2 are discussed. The results demonstrate that the presence of the more electronegative oxygen atom in the RhI coordination sphere polarizes the H–H bond and promotes its heterolytic cleavage, thereby leading to the formation of a RhI–monohydride complex in which the oxygen atom of the ligand is protonated.

In this work, we demonstrate the potential of multi-edge X-ray absorption near-edge structure (XANES) analysis in completely defining the ground state electronic structure of a prototypical biomimetic complex of the [2Fe]-subcluster of the catalytic H-cluster of FeFe-hydrogenase. The spectral features at the ionization thresholds for Fe, S, C, and O 1s (K-edge) and Fe 2p (L-edge) core electrons were considered simultaneously to obtain the atomic compositions of the unoccupied frontier molecular orbitals. A systematic error analysis was carried out at the most informative S K-edge for spectra collected by multiple detection methods, at various data collection temperatures, and different sample preparation protocols. As expected for the difference in bonding between bridging and terminal Fe-S(thiolate) coordination, the Fe-S bond is more covalent in the [2Fe]-biomimetic complex with formally iron(I) centers (36 ± 2% S character per Fe-S bond) than in the previously described [2Fe-2S] clusters (25 ± 3% S character per Fe-S bond) with formally iron(III) centers. An electron hole-based analysis of the pre-edge features at Fe K-, Fe L-, and S K-edges experimentally defines the composition of the first three frontier unoccupied molecular orbitals to contain 4% Fe 4p, 44% Fe 3d, and 24% S 3p contributions per electron hole, respectively. The complementary CO ligand contribution thus can be defined as 28% per electron hole. These experimental orbital covalency values are important in rationalizing redox properties, electrophilicity of the metals, or nucleophilicity of the ligands, and critically evaluating the absolute accuracy of electronic structure calculations.

The catalytically active cluster of [FeFe]-hydrogenase (H-cluster) is unique due to its chemical composition and electronic and geometric structures. Protein crystallography revealed the presence of biologically unique diatomic ligands coordinating to the Fe centers and three light atoms bridging the sulfur atoms of its [2Fe]-subcluster. The identity of the light atoms remains uncertain, even at close to atomic resolution (1.39 A), as well as due to the lack of understanding at the molecular level of the cluster's biosynthetic pathway. By using all of the proposed ligand compositions, we carried out a comprehensive electronic structure analysis by evaluating the topology of the electron density and, particularly, the atomic spin density distribution derived from various population analysis methods for the free dithiolate ligands, the biomimetic [2Fe] complexes, and the entire H-cluster embedded in its approximately 3.5 A protein environment. In the biomimetic model complexes we found substantial spin density delocalization at the bridgehead of the dithiolate ligands. We attributed the presence of spin density to the through-space spin polarization interaction between the paramagnetic iron centers and the bridgehead group, as represented by the ring critical points for the [Fe–(S–R–S)–Fe] metallacycles. However, this spin polarization of the bridgehead group vanishes for some of the biomimetic models, as well as for the 208-atom computational model of the H-cluster, due to a network of weak interactions. When the bridgehead group becomes part of a conduit for transmitting the spin polarization towards the terminal ends of each interaction network, such as the distal water or H-bonded residues, the spin density vanishes. The variations of the Fe atomic spin densities were compared and contrasted for the proximal and distal iron sites in the crystallographic and the rotated conformations, respectively.

FeFe hydrogenases [1] catalyze the reversible oxidation of dihydrogen at a remarkable rate [2, 3]. Their active site, termed the H-cluster, comprises a classic [4Fe–4S] cubane that is covalently linked via a bridging cysteine residue to a biologically unprecedented organometallic binuclear 2Fesubcluster. The two clusters are electronically [4] and magnetically [5] inseparable. The low-spin and lowvalence iron centers of the 2Fe-subcluster are stabilized by diatomic carbonyl (CO) and cyanide (CN) strong-field ligands and they are bridged by a dithiolate group (SCH2XCH2S) , whose central atom (bridgehead) has not yet been unequivocally determined. On the basis of X-ray crystallography, Fourier transform IR spectroscopy, N hyperfine sublevel correlation spectroscopy, and theoretical calculations, the dithiolate ligand has been proposed to be 1,3-propanedithiolate (PDT; X is CH2) [6], dithiomethylamine (DTMA; X is NH) [7, 8], or dithiomethyl ether (DTME; X is O) [9]. This unprecedented coordination environment of the 2Fe-subcluster has stimulated an intensive biochemical research to identify the source and the exact biosynthetic pathway leading to the formation of these biologically unique ligands. However, the proposed hypotheses regarding the biosynthesis of the dithiolate bridging ligand are based only on chemical intuition [10, 11]. Therefore, in this communication we report a density-functional-theorybased, comparative evaluation of the energetic and mechanistic feasibility of various pathways. For the sake of completeness, all three possible candidates of dithiolates (X is CH2, NH, or O) were examined. Staying within the boundaries of known biochemical processes, we have found that a pathway that includes known S-adenosylmethionine (SAM)-catalyzed reactions is both energetically and mechanistically more favorable. Although we describe the pathway for the formation of PDT, it can be readily adopted for the biosynthesis of the DTMA and DTME analogues, provided that the proper precursor molecule is available. The enzymes HydE, HydF, and HydG have been identified as necessary and likely sufficient for the biosynthesis of the 2Fe-subcluster of the H-cluster. HydF shows GTPase activity and serves as the scaffold protein where the 2Fesubcluster is assembled [12, 13]. HydE and HydG belong to the radical-SAM superfamily of enzymes [14]. These enzymes generate the highly reactive 5-adenosyl radical (50-dA!) that can drive a variety of biochemical processes, including hydrogen atom abstraction, carbon–carbon bond cleavage, and sulfur insertion [15]. A biosynthetic hypothesis suggested that glycine could serve as the source of the diatomic ligands and it was supported by a computational investigation that is conceptually similar to the one presented here [10]. This hypothesis was recently experimentally verified, as the presence of CO and CN was detected when HydG was treated with tyrosine, through a mechanism that likely involves the formation of a glycyl radical [16, 17]. Therefore, HydE is most likely responsible for the biosynthesis of the dithiolate bridge on a [2Fe–2S] cluster located in the scaffold protein HydF. This [2Fe–2S] cluster is coordinated by three highly conserved cysteine residues, whereas the fourth ligand is readily exchangeable [13]. Moreover, the radical-SAM enzymes biotin synthase Electronic supplementary material The online version of this article (doi:10.1007/s00775-010-0698-y) contains supplementary material, which is available to authorized users.

Sulfur-containing mono- or bidentate types of ligands, usually form square planar Ni((II))S(4) complexes. However, it has already been established that the bidentate L(-) dithioimidodiphosphinato ligands, [R(2)P(S)NP(S)R'(2)](-), R, and R' = aryl or alkyl, can afford both tetrahedral and square planar, NiS(4)-containing, homoleptic Ni(R,R')L(2) complexes, owing to an apparent structural flexibility, which has not, so far, been probed. In this work, the literature tetrahedral Ni[R(2)P(S)NP(S)R(2)](2) complexes, R = Ph (Ni(Ph,Ph)L(2), 1(Td)) and R = (i)Pr (Ni(iPr,iPr)L(2), 2) as well as the newly synthesized Ni[(i)Pr(2)P(S)NP(S)Ph(2)](2) complex (Ni(iPr,Ph)L(2), 3), have been studied by UV-vis, IR, and (31)P NMR spectroscopy. Complex 3 was shown by X-ray crystallography to be square planar, and magnetic studies confirmed that it is diamagnetic in the solid state. However, it becomes paramagnetic in solution, as it shows a similar UV-vis spectrum to one of the tetrahedral 1(Td) and 2 complexes. The crystal structure of the potassium salt of the asymmetric ligand, [(i)Pr(2)P(S)NP(S)Ph(2)]K, has also been determined and compared to those of the protonated (i)Pr(2)P(S)NHP(S)Ph(2) ligand and complex 3. All three, 1(Td), 2, and 3, Ni(R,R')L(2) complexes show strong paramagnetic effects in their solution (31)P NMR spectra. The magnetic properties of paramagnetic complexes 1 and 2 in the solid state were investigated on oriented crystals, and their analysis afforded remarkably small values of the spin-orbit coupling constant (lambda) and orbital reduction factor (k) parameters, implying significant delocalization of unpaired electronic density toward the ligands. The above experimental findings are combined with data from standard density functional theory and correlated multiconfiguration ab initio theoretical methods, in an effort to investigate the interplay between the square planar and tetrahedral geometries of the NiS(4) core, the mechanistic pathway for the spin-state interconversion, the degree of covalency of the Ni-S bonds, and the distribution of the spin density in this type of system. The analysis provides justification for the structural flexibility of such ligands, affording Ni(R,R')L(2) complexes with variable metallacycle conformation and NiS(4) core geometries. Of particular importance are the large zero-field splitting values estimated by both experimental and theoretical means, which have not, as yet, been verified by direct methods, such as electron paramagnetic resonance spectroscopy. The findings of our work confirm earlier observations on the feasibility of synthesizing either tetrahedral or square planar NiS(4) complexes containing the same type of ligands. They can also form the basis of investigating structure-properties relationships in other NiS(4)-containing systems.

Metal–Organic Frameworks (MOFs) are porous crystalline materials that have emerged as promising hosts\ud for the heterogenization of homogeneous organometallic catalysts, forming hybrid materials which\ud combine the benefits of both classes of catalysts. Herein, we report the encapsulation of the\ud organometallic cationic Lewis acidic catalyst [CpFe(CO)2(L)]+ ([Fp–L]+, Cp ¼ h5\ud -C5H5, L ¼ weakly bound\ud solvent) inside the pores of the anionic [Et4N]3[In3(BTC)4] MOF (H3BTC ¼ benzenetricarboxylic acid) via\ud a direct one-step cation exchange process. To conclusively validate this methodology, initially [Cp2Co]+\ud was used as an inert spatial probe to (i) test the stability of the selected host; (ii) monitor the\ud stoichiometry of the cation exchange process and (iii) assess pore dimensions, spatial location of the\ud cationic species and guest-accessible space by single crystal X-ray crystallography. Subsequently,\ud the quasi-isosteric [Fp–L]+ was encapsulated inside the pores via partial cation exchange to form\ud [(Fp–L)0.6(Et4N)2.4][In3(BTC)4]. The latter was rigorously characterized and benchmarked as\ud a heterogeneous catalyst in a simple Diels–Alder reaction, thus verifying the integrity and reactivity of\ud the encapsulated molecular catalyst. These results provide a platform for the development of\ud heterogeneous catalysts with chemically and spatially well-defined catalytic sites by direct exchange\ud of cationic catalysts into anionic MOFs.

The complexes [Rh(CO)(PPh3){Ph2PNP(O)Ph2-P,O}] (3), [Rh(CO)2{Ph2P(Se)NP(Se)Ph2-Se,Se′}] (5), and [Rh(CO)(PPh3){Ph2P(Se)NP(Se)Ph2-Se,Se′}] (6), were synthesised by stepwise reactions of CO and PPh3 with [Rh(cod){Ph2PNP(O)Ph2-P,O}] (2) and [Rh(cod){Ph2P(Se)NP(Se)Ph2-Se,Se′}] (4), respectively. The complexes 3, 5 and 6 have been studied by IR, as well as 1H and 31P NMR spectroscopy. The ν(CO) bands of complexes 3 and 6 appear at approximately 1960 cm−1, indicating high electron density at the RhI centre. The structure of complexes 3 and 6 has been determined by X–ray crystallography, and the 31P NMR chemical shifts have been resolved via low temperature NMR experiments. Both complexes exhibit square planar geometry around the metal centre, with the five-membered ring of complex 3 being almost planar, and the six-membered ring of complex 6 adopting a slightly distorted boat conformation. The C–O bond of the carbonyl ligand is relatively weak in both complexes, due to strong π-back donation from the electron rich RhI centre. The catalytic activity of the complexes 2, 3 and 6 in the hydroformylation of styrene has been investigated. Complexes 2 and 3 showed satisfactory catalytic properties, whereas complex 6 had effectively no catalytic activity.

The S/Se-containing bidentate ligands LH of the type R2P(E)NHP(E)R'2, E = S, Se and R, R' = Ph or iPr have been employed to synthesize ML2 (M = Mn, Co) complexes which contain the biologically important MS4 core. Theoretical calculations on the LH and L- forms of the ligands probe the geometric and electronic changes induced by the deprotonation of the LH form, which are correlated with structural data from X-ray crystallography. These results reflect the flexibility of the ligands, which enables them to be rather versatile with respect to the formation of ML2 complexes with varied geometries and MEPNPE metallacycle conformations. A series of old and new ML2 complexes have been synthesized and their structural, spectroscopic and magnetic properties characterized in detail. The nephelauxetic ratio beta of the CoL2 complexes provides evidence of covalent interactions, whereas the EPR properties of the MnL2 complexes are interpreted on the basis of predominant ionic interactions, between the metal center and the ligands, respectively. Additional evidence for the existence of covalent interactions in the CoL2 complexes (R = Ph, iPr, or mixed Ph/iPr), is offered by comparisons between their 31P NMR. The aforementioned notations are supported by extensive theoretical calculations on the ML2 (E = S, R = Me) modelled structures, which probe the covalent and ionic character of the M-S bonds when M = Co or Mn. Wider implications of the findings of the present study on the M-S covalency and its importance in the active sites of various metalloenzymes are also discussed.

The reactivity of the bimetallic complex (Ph4P)2[W2(μ-Br)3Br6] ({W2.5W}7+, a'2e3) towards ring opening metathesis polymerization (ROMP) of norbornene (NBE) and some of its derivatives, as well as the mechanistically related metathesis polymerization of phenylacetylene (PA), is presented. Our results show that addition of a silver salt (AgBF4) is necessary for the activation of the ditungsten complex. Polymerization of PA proceeds smoothly in tetrahydrofuran (THF) producing polyphenylacetylene (PPA) in high yields. On the other hand, the ROMP of NBE and its derivatives is more efficient in CH2Cl2, providing high yields of polymers. 13C Cross Polarization Magic Angle Spinning (CPMAS) spectra of insoluble polynorbornadiene (PNBD) and polydicyclopentadiene (PDCPD) revealed the operation of two mechanisms (metathetic and radical) for cross-linking, with the metathesis pathway prevailing.

The magnetic properties of the mononuclear manganese(III) complex [Mn{(OPPh2)2N}3] are investigated by means of magnetometry and dual-mode X-band electron paramagnetic resonance spectroscopy. Slow relaxation of magnetization is induced in the presence of external magnetic fields.

Statistical copolymers of norbornene (NBE) with 5-vinyl-2-norbornene (VNBE) were prepared by ring-opening metathesis polymerization, employing the triply bonded ditungsten complex Na[W2(μ-Cl)3Cl4(THF)2].(THF)3. NMR measurements revealed that the side vinyl groups of the VNBE monomer remain intact during the copolymerization reaction. The reactivity ratios were estimated using the Finemann–Ross (FR), the inverted FR, and the Kelen–Tudos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by differential scanning calorimetry measurements and were examined in the frame of several theoretical equations allowing the prediction of these Tg values. The best fit was obtained using methods that take into account the monomer sequence distribution of the copolymers. Finally, the kinetics of the thermal decomposition of the copolymers was studied by thermogravimetric analysis in the frame of the Ozawa–Flynn–Wall and Kissinger methods.