0000000001238351
AUTHOR
Mikko M. Hänninen
Magneto-Structural Properties and Theoretical Studies of a Family of Simple Heterodinuclear Phenoxide/Alkoxide Bridged MnIIILnIII Complexes : On the Nature of the Magnetic Exchange and Magnetic Anisotropy
A family of MnIIILnIII strictly dinuclear complexes of general formula [MnIII(μ-L)(μ-OMe)(NO3)LnIII(NO3)2(MeOH)] (LnIII = Gd, Dy, Er, Ho) has been assembled in a one pot synthesis from a polydentate, multipocket aminobis(phenol)ligand [6,6'-{(2-(1-morpholyl)ethylazanediyl)bis(methylene)}bis(2-methoxy-4-methylphenol)], Mn(NO3)2·4H2O, Ln(NO3)3· nH2O, and NEt3 in MeOH. These compounds represent the first examples of fully structurally and magnetically characterized dinuclear MnIIILnIII complexes. Single X-ray diffraction studies reveal that all complexes are isostructural, consisting of neutral dinuclear molecules where the MnIII and LnIII metal ions, which exhibit distorted octahedral MnN2O4 …
Imidotungsten(VI) complexes with chelating amino and imino phenolates
The reaction of WOCl(4) with 2,4-di-tert-butyl-6-((isopropylamino)methyl)phenol followed by the reaction with phenyl isocyanate leads to the formation of imidotungsten(VI) complex [W(NPh)Cl(3)(OC(6)H(3)(CH(2)NH-i-Pr)-2-t-Bu(2)-4,6)] 4 with a chelating aminophenolate ligand. When the same procedure was applied using aminophenols with bulkier substituents in the amino group, the final product was an unexpected Schiff-base complex [W(NPh)Cl(3)(OC(6)H(3)(CH=NPh)-2-t-Bu(2)-4,6)] 5, where the ligand is derived from 2,4-di-tert-butyl-6-((phenylimino)methyl)phenol. Complex 5 is also formed in the thermal degradation of 4. On the whole, 5 appears to be formed by a disproportionation of intermediate …
Touching the upper limit for ferromagnetic interactions in hetero-bridged dinuclear [Cu-2(II)] complexes using a novel N-5-dinucleating ligand bearing an endogenous monoatomic amido(R-NH-)-bridging group
A novel N-5-dinucleating ligand 4-amino-3,5-bis(bipyridine-2-yl)-1,2,4-triazole allows the preparation for the first time, and under mild conditions, of single and mixed amido(R-NH-)-bridged copper(II) complexes, the latter exhibiting very strong ferromagnetic coupling.
Insights into the decomposition pathway of a lutetium alkylamido complex via intramolecular C–H bond activation
Synthesis, characterization and reaction chemistry of lutetium alkylamido LLu(CH2SiMe3)(NHCPh3) (2), L = 2,5-[Ph2P=N(4-iPrC6H4)]2N(C4H2)–, is reported. Complex 2 undergoes cyclometalation of the NHCPh3 ligand at elevated temperatures to produce the orthometalated complex LLu(κ2−N,C-(NHCPh2(C6H4))) (3) which converts to 0.5 equivalents of bis(amido) LLu(NHCPh3)2 (4) upon heating at 80 °C for 24 h. Reaction of complex 2 with 4-dimethylaminopyridine (DMAP) does not promote alkane elimination nor imido formation. A kinetic analysis of the thermal decomposition of complex 2, supported by deuterium labelling studies and computational analysis (PBE0/def2-TZVP/SDD(Lu)), indicate direct Csp2–H activ…
Structural and electronic elucidation of a N-heterocyclic silylene vanadocene adduct
The solid and solution state structure of the vanadium(II) N‐ heterocyclic silylene (NHSi) complex, [(SiIPr)V(Cp)2] (1) is reported ( SiIPr: 1,3‐bis(2,6‐diisopropylphenyl)‐1,3‐diaza‐2‐silacyclopent‐4‐ en‐2‐ylidene). The electronic structure of 1 is probed using combination of magnetic measurements, EPR spectroscopy and computational studies. The V–Si bond strength and complex forming mechanism between vanadocene and NHSi ligand is elucidated using computational methods. peerReviewed
Chelation of a proton by oxidized diphosphines
Abstract The chelation of a proton by oxidized diphosphines is studied for the first time both experimentally and theoretically. As a proof of concept the rare case where two different H-bond systems exist in one compound, H[7,8-(OP i Pr 2 ) 2 -7,8- nido -C 2 B 9 H 10 ] is reported. Based on NBO, QTAIM and ELF calculations, the P–O⋯H + ⋯O–P interactions were characterized as strong hydrogen bonds.
Synthesis, Structure and Catalytic Properties of Dinuclear Mo-VI Complexes with Ditopic Diaminotetraphenols
MoVI complexes with novel ditopic diaminotetraphenol ligands have been prepared by using a one-pot procedure in methanol or DMSO with [MoO2(acac)2] (acac = acetylacetonate) as the molybdenum source. The complexes were characterised with X-ray diffraction, NMR spectroscopic studies, elemental analysis and IR spectroscopy. In the solid state, the compounds represent either a rodlike molecular or oxido-bridged polymeric structure. The catalytic activity of the complexes was investigated by oxidising benzyl alcohol and 1-phenylethanol with hydrogen peroxide to the corresponding aldehyde and ketone, respectively. Furthermore, the catalytic activity was surveyed also in epoxidation of cyclooctene.
Synthesis of Highly Functionalized Fluorinated Cispentacin Derivatives
Fluorinated highly functionalized cispentacin derivatives were synthetised starting from an unsaturated bicyclic b-lactam through C¼C bond functionalization via the dipolar cycloaddition of a nitrile oxide, isoxazoline opening, and fluorination by OH/F exchange.
Pyrazolium- and 1,2-Cyclopentadiene-Based Ligands as σ-Donors: a Theoretical Study of Electronic Structure and Bonding
A high-level theoretical investigation of 1,2-cyclopentadiene (4) was performed using density functional theory and wave function methods. The results reveal that, in contrast to earlier assumptions, the ground state of this ephemeral “allene” is carbene-like with a small diradical component. Furthermore, the electronic structure and chemistry of 4 are found to parallel that of 1,2,4,6-cycloheptatetraene: both molecules possess a low-lying excited singlet state with a closed-shell carbenic structure, enabling rich coordination chemistry. Energy decomposition analyses conducted for currently unknown metal complexes of 4 as well as those involving stable carbenes based on the pyrazolium frame…
An experimental and theoretical study of a heptacoordinated tungsten(VI) complex of a noninnocent phenylenediamine bis(phenolate) ligand
[W(N2O2)(HN2O2)] (H4N2O2 = N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine) with a noninnocent ligand was formed by reaction of the alkoxide precursor [W(eg)3] (eg = the 1,2-ethanediolate dianion) with two equivalents of ligand. The phenol groups on one of the ligands are completely deprotonated and the ligand coordinates in a tetradentate fashion, whereas the other ligand is tridentate with one phenol having an intact OH group. The molecular structure, magnetic measurements, EPR spectroscopy, and density functional theory calculations indicate that the complex is a stable radical with the odd electron situated on the tridentate amidophenoxide ligand. The formal oxidation s…
Insights into the decomposition pathway of a lutetium alkylamido complex via intramolecular C–H bond activation
Abstract Synthesis, characterization and reaction chemistry of lutetium alkylamido LLu(CH2SiMe3)(NHCPh3) (2), L = 2,5-[Ph2P=N(4-iPrC6H4)]2N(C4H2)–, is reported. Complex 2 undergoes cyclometalation of the NHCPh3 ligand at elevated temperatures to produce the orthometalated complex LLu(κ2−N,C-(NHCPh2(C6H4))) (3) which converts to 0.5 equivalents of bis(amido) LLu(NHCPh3)2 (4) upon heating at 80 °C for 24 h. Reaction of complex 2 with 4-dimethylaminopyridine (DMAP) does not promote alkane elimination nor imido formation. A kinetic analysis of the thermal decomposition of complex 2, supported by deuterium labelling studies and computational analysis (PBE0/def2-TZVP/SDD(Lu)), indicate direct Csp…
Homoleptic Pnictogen-Chalcogen Coordination Complexes
The synthesis and structural characterization of dicationic selenium and tellurium analogues of the carbodiphosphorane and triphosphenium families of compounds are reported. These complexes, [Ch(dppe)][OTf](2) [Ch = Se, Te; dppe = 1,2-bis(diphenylphosphino)ethane; OTf = trifluoromethanesulfonate], are formed using [Ch](2+) reagents via a ligand-exchange protocol and represent extremely rare examples of homoleptic pnictogen → chalcogen coordination complexes. The corresponding arsenic compounds were also prepared, [Ch(dpAse)][OTf](2) [Ch = Se, Te; dpAse = 1,2-bis(diphenylarsino)ethane], exhibiting the first instance of an arsenic → chalcogen dative bond. The electronic structures of these un…
Diphenoxo-Bridged NiIILnIII Dinuclear Complexes as Platforms for Heterotrimetallic (LnIIINiII)2RuIII Systems with a High-Magnetic-Moment Ground State: Synthesis, Structure, and Magnetic Properties
The first examples of pentanuclear heterotrimetallic [(LnNi)(2)Ru] [Ln(3+) = Gd (1) and Dy (2)] complexes were prepared and magnetostructurally characterized. They exhibit ferromagnetic interactions, leading to a high-magnetic-moment ground state.
Vanadium complexes with multidentate amine bisphenols
The reaction of VO(acac)2 (acac(-) = acetyl acetonate) with tripodal glycine bisphenol H3L(1) under an ambient atmosphere yields a hexacoordinated vanadium(iv) complex [V(acac)(L(1))] (1). The corresponding reactions with tripodal 2-propanolamine bisphenol H3L(2) and potentially pentadentate ethoxyethanolamine bisphenol H3L(3) lead to the oxidation of the metal centre and formation of mononuclear oxovanadium(v) complexes [VO(L(2))] (2) and [VO(L(3))] (3), respectively. Alternatively, these latter two complexes can be prepared using VOSO4·5H2O or VO(OPr)3 as a precursor. The CV of 1 in an ACN solution shows a reversible one-electron process at E1/2 = +1.18 V, whereas 2 and 3 have an irrevers…
Experimental and Computational Study of Unique Tetranuclear µ 3 ‐Chloride and µ‐Phenoxo/Chloro‐Bridged Defective Dicubane Cobalt(II) Clusters
Two tetranuclear CoII clusters [Co4(L)2(µ3-Cl)2Cl2] have been prepared by using multidentate diaminobisphenolate ligands. The solid-state structures of the complexes were determined by single-crystal X-ray diffraction. The cores of the cluster compounds can be defined as a two-vertex-deficient dicubane geometry (pseudo-dicubane). In the central unit, the cobalt(II) cations are linked through phenoxide oxygen (outer bridges) and chloride anions (inner bridges), previously unprecedented in this type of cobalt cluster. The magnetic properties were studied by both experimental and computational methods. By using a combination of techniques, we were able to determine the nature and strength of t…
Experimental and Computational Study of Unique Tetranuclear µ3-Chloride and µ-Phenoxo/Chloro-Bridged Defective Dicubane Cobalt(II) Clusters
Two tetranuclear CoII clusters [Co4(L)2(µ3-Cl)2Cl2] have been prepared by using multidentate diaminobisphenolate ligands. The solid-state structures of the complexes were determined by single-crystal X-ray diffraction. The cores of the cluster compounds can be defined as a two-vertex-deficient dicubane geometry (pseudo-dicubane). In the central unit, the cobalt(II) cations are linked through phenoxide oxygen (outer bridges) and chloride anions (inner bridges), previously unprecedented in this type of cobalt cluster. The magnetic properties were studied by both experimental and computational methods. By using a combination of techniques, we were able to determine the nature and strength of t…
Aqueous self-assembly and cation selectivity of cobaltabisdicarbollide dianionic dumbbells.
The anion [3,3'-Co(C2B9H11)2](-) ([COSAN](-)) produces aggregates in water. These aggregates are interpreted to be the result of C-H⋅⋅⋅H-B interactions. It is possible to generate aggregates even after the incorporation of additional functional groups into the [COSAN](-) units. The approach is to join two [COSAN](-) anions by a linker that can adapt itself to act as a crown ether. The linker has been chosen to have six oxygen atoms, which is the ideal number for K(+) selectivity in crown ethers. The linker binds the alkaline metal ions with different affinities; thus showing a distinct degree of selectivity. The highest affinity is shown towards K(+) from a mixture containing Li(+), Na(+), …
Towards Multifunctional Materials Incorporating Elastomers and Reversible Redox-Active Fragments
This paper presents a novel and unique feature of metallacarboranes, consisting of the linkage of this redox electro-active site to a stretchable polymer. This is based on polyTHF, a known and applied material. This hybrid material has the two ends functionalized: one with the aforemen- tioned redox molecule and the other with a terminal OH group, both linked by a molecular spring. Moreover, the redox electro-active molecules can be synthesized with either cobalt (cobaltabisdicarbollide) or with iron (ferrabisdi- carbollide), species whose respective E1/2 value differs by almost 1 V. The polymerization mechanism, based on an in- termediate molecular crystal structure, is explained through a…
Synthesis of Sterically Hindered Chiral 1,4-Diols from Different Lignan-Based Backbones
Methods for synthetic modifications of the natural dibenzylbutyrolactone lignan hydroxymatairesinol into chiral 1,4-diols with different lignan-derived backbones have been developed. A stepwise procedure, involving alkylation and oxidation, was shown to be successful and several highly substituted 1,4-diols were prepared. Some substituted butyrolactones resisted alkylation and led to the formation unusually stable hemiketals (butyrolactols). The formation of stable hemiketals was investigated in detail, showing that different backbone structures influence the formation and reactivity of the hemiketals.
A cocrystal of two Mo(VI) complexes bearing different diastereomers of the 2,4-di-tert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]methyl}phenolate ligand derived from (+)-ephedrine
The title cocrystal contains two chiral conformational diastereomers,viz.(1S,2R,RN)- and (1S,2R,SN)-, of [2,4-di-tert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]methyl}phenolato](methanol)-cis-dioxidomolybdenum(VI), [Mo(C25H35NO2)O2(CH3OH)], representing the first example of a structurally characterized molybdenum complex with enantiomerically pure ephedrine derivative ligands. The MoVIcations exhibit differently distorted octahedral coordination environments, with two oxide ligands positionedcisto each other. The remainder of the coordination comprises phenoxide, alkoxide and methanol O atoms, with an amine N atom completing the octahedron. The distinct complexes are linked by st…
Syntheses of Four Enantiomers of 2,3-Diendo- and 3-Endo-aminobicyclo[2.2.2]oct-5-ene-2-exo-carboxylic Acid and Their Saturated Analogues
Abstract: Ethyl 2,3- diendo -3-aminobicyclo[2.2.2]oct- 5-ene-2-carboxylate ((±)- 1 ) was resolved with O , O '-dibenzoyltartaric acid via diastere omeric salt formation. The efficient synthesis of the enantiomers of 2,3- diendo -3-aminobicyclo[2.2.2]oct- 5-ene-2-carboxylic acid ((+)- 7 and (–)- 7 ), 3- endo -aminobicyclo[2.2.2]oct-5-ene-2- exo -carboxylic acid ((+)- 5 and (–)- 5 ), cis - and trans -3-aminobicyclo[2.2.2]octa ne-2-carboxylic acid ((+)- 6 , (–)- 6 , (+)- 8 and (–)- 8 ) was achieved via isomerization, hydrogenation and hydrolysis of the corresponding esters (–)- 1 and (+)- 1 . The stereochemistry and relative configurations of the synthesized compounds were determined by NMR sp…
Fabrication of Porous Hydrogenation Catalysts by a Selective Laser Sintering 3D Printing Technique
Open in a separate window Three-dimensional selective laser sintering printing was utilized to produce porous, solid objects, in which the catalytically active component, Pd/SiO2, is attached to an easily printable supporting polypropylene framework. Physical properties of the printed objects, such as porosity, were controlled by varying the printing parameters. Structural characterization of the objects was performed by helium ion microscopy, scanning electron microscopy, and X-ray tomography, and the catalytic performance of the objects was tested in the hydrogenation of styrene, cyclohexene, and phenylacetylene. The results show that the selective laser sintering process provides an alte…
CoIILnIII dinuclear complexes (LnIII = Gd, Tb, Dy, Ho and Er) as platforms for 1,5-dicyanamide-bridged tetranuclear CoII2LnIII2 complexes: A magneto-structural and theoretical study
Five acetate-diphenoxo triply-bridged Co-II-Ln(III) complexes (Ln(I) = Gd, Tb, Dy, Ho, Er) of formula [Co(mu-L)(mu-Ac)Ln(NO3)(2)] and two diphenoxo doubly-bridged Co-II-Ln(III) complexes (Ln(III) = Gd, Tb) of formula [Co(H2O)(mu-L)Ln(NO3)(3)]center dot S (S = H2O or MeOH), were prepared in one pot reaction from the compartmental ligand N,N',N ''-trimethyl-N,N ''-bis(2-hydroxy3-methoxy-5-methylbenzyl)diethylene triamine (H2L). The diphenoxo doubly-bridged Co-II-Ln(III) complexes were used as platforms to obtain 1,5-dicyanamide-bridged tetranuclear Co-II-Ln(III) complexes (Ln(III) = Gd, Tb, Dy, Ho, Er). All exhibit ferromagnetic interactions between the Co-II and Ln(III) ions and in the case …
Syntheses and Structural Study of Novel Tetranuclear Bis(phenoxido)‐Bridged Cu II Metal–Organic Macrocycles
Six new tetranuclear copper(II) complexes were prepared exploiting novel ditopic alkylenediamine-N,N,N′,N′-tetraphenolate ligands. The geometrical parameters of the compounds can be varied by introducing different solvents of crystallization into the lattice. The structures of all six complexes were determined from single-crystal X-ray diffraction analyses and the magnetic properties of the complexes were estimated by computational DFT calculations. The relationship between the magnetic exchange coupling constant (J) and the Cu–O–Cu angle (θ) in these bis(phenoxido)-bridged complexes was investigated and a magnetostructural correlation was established between J and the θ angle. All studied …
Do Extremely Bent Allenes Exist?
Bent allenes: Theoretical calculations show that extremely bent allenes, cyclic or acyclic, adopt a ground state that only bears a formal relationship to classical allenes. Consequently, five-membered ring allenes favor a carbene-like electronic structure and formally contain a trivalent carbon(II) center. peerReviewed
Icosahedral carboranes as scaffolds for congested regioselective polyaryl compounds : the distinct distance tuning of C-C and its antipodal B-B
Four-fold aryl substituted o-carborane derivatives with defined patterns of substitution at the antipodal region of the cluster carbon atoms have been achieved. It is proven that this region is congested but lacks steric hindrance. Also, the two antipodal sites Cc-Cc and B9-B12 are affected very distinctly by electron donor substituents. peerReviewed
A Combined Experimental and Theoretical Study on Bis(μ‐alkoxo)diiron(III) Complexes with Hydroxybenzylaminoethanol [O,N,O] Donor Ligands: Syntheses, Structures and Magnetic Properties
Three new neutral bis(μ-alkoxo)diiron(III) complexes were prepared from N(R),N-(2-methylene-4,6-di-tert-butylphenol)aminoethan-1-ol ligands (H2L1, R = Me and H2L2, R = H). In these complexes, the ligand wraps around the metal center exhibiting a tridentate facial coordination mode with alkoxo-bridging oxygen, amine nitrogen and phenoxo oxygen donor atoms. In the complex [Fe(acac)L1]2·MeCN (1) acetylacetonato coligand complete the distorted octahedral coordination spheres of the iron(III) ions, whereas in the five-coordinate iron(III) chloride complexes [FeClL1]2 (2) and [FeClL2]2 (3) the ligands induce a geometry that is intermediate between square pyramidal and trigonal bipyramidal. Magnet…
An insight into the synthesis of novel aryl-substituted alicyclic β-amino acid derivatives through substrate-directed palladium-catalysed regio- and stereoselective cross-coupling
Novel aryl-substituted alicyclic β-amino acid derivatives were synthesized through substrate-determined palladium-catalysed cross-coupling of aryl iodides with five- or six-membered cycloalkene β-amino esters. The arylations were investigated with different catalysts, solvents, bases and aryl halides, and with some cyclohexene 2-aminocarboxylate isomers. The stereochemistry and the position of the ring olefinic bond of the starting 2-aminocycloalkanecarboxylate influenced the coupling reaction, and predetermined the structure of the arylated product.
Retro-Diels-Alder Protocol for the Synthesis of Pyrrolo[1,2-a]pyrimidine and Pyrimido[2,1-a]isoindole Enantiomers
A simple protocol was introduced to prepare several enantiomerically pure heterocycles by using (–)-(1R,2R,3S,4S)-3-aminonorbornene-2-carboxylic acid as a chiral auxiliary. The protocol is based on a domino ring-closure reaction, in which the relative configuration of the new asymmetric center is controlled by the stereochemistry of the amino acid, followed by a microwave-induced retro-Diels–Alder reaction.
A three-coordinate iron–silylene complex stabilized by ligand–ligand dispersion forces
The structural and bonding properties of a three-coordinate N-heterocyclic silyene (NHSi) complex of the iron(II) amide [Fe{N(SiMe3)2}2] are reported. Computational studies reveal that dispersion forces between the amido SiMe3 substituents and the isopropyl substituents on the NHSi ligand significantly enhance the stability of the complex, along with Fe-to-Si π-backbonding.
Heptacoordinated Molybdenum(VI) Complexes of Phenylenediamine Bis(phenolate): A Stable Molybdenum Amidophenoxide Radical
The syntheses, crystallographic structures, magnetic properties, and theoretical studies of two heptacoordinated molybdenum complexes with N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (H4N2O2) are reported. A formally molybdenum(VI) complex [Mo(N2O2)Cl2(dmf)] (1) was synthesized by the reaction between [MoO2Cl2(dmf)2] and H4N2O2, whereas the other molybdenum(VI) complex [Mo(N2O2)(HN2O2)] (2) was formed when [MoO2(acac)2] was used as a molybdenum source. Both complexes represent a rare case of the MoVI ion without any multiply bonded terminal ligands. In addition, molecular structures, magnetic measurements, ESR spectroscopy, and density functional theory calculations ind…
Porous 3D Printed Scavenger Filters for Selective Recovery of Precious Metals from Electronic Waste
Selective laser sintering (SLS) 3D printing is used to fabricate highly macroporous ion scavenger filters for recovery of Pd and Pt from electronic waste. The scavengers are printed by using a mixture of polypropylene with 10 wt% of type‐1 anion exchange resin. Porosities and the flow‐through properties of the filters are controlled by adjusting the SLS printing parameters. The cylinder‐shaped filters are used in selective recovery of Pd and Pt from acidic leachate of electronic waste simply by passing the solution through the object. Under such conditions, the scavenger filters are able to capture Pd and Pt as anionic complexes with high efficiency from a solution containing mixture of dif…
An experimental and theoretical study of a heptacoordinated tungsten(VI) complex of a noninnocent phenylenediamine bis(phenolate) ligand
Abstract [W(N2O2)(HN2O2)] (H4N2O2 = N,N′-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine) with a noninnocent ligand was formed by reaction of the alkoxide precursor [W(eg)3] (eg = the 1,2-ethanediolate dianion) with two equivalents of ligand. The phenol groups on one of the ligands are completely deprotonated and the ligand coordinates in a tetradentate fashion, whereas the other ligand is tridentate with one phenol having an intact OH group. The molecular structure, magnetic measurements, EPR spectroscopy, and density functional theory calculations indicate that the complex is a stable radical with the odd electron situated on the tridentate amidophenoxide ligand. The formal ox…
Cytotoxicities of Polysubstituted Chlorodicarbonyl(cyclopentadienyl) and (Indenyl)ruthenium Complexes
Polysubstituted cyclopentadienyl and indenyl complexes of ruthenium were synthesized and investigated to elucidate their potential cytotoxic activities. In particular, substituted (indenyl)ruthenium complexes inhibited the proliferation of a panel of human adherent cancer cells with comparable activity to reference agent cisplatin. One of the active compounds exerted a concentration dependent inhibition of cell cycle at G1–S transiton as evidenced by flow cytometry.
Highly Syndiotactic or Isotactic Polyhydroxyalkanoates by Ligand-Controlled Yttrium-Catalyzed Stereoselective Ring-Opening Polymerization of Functional Racemic β-Lactones
International audience; Reported herein is the first stereoselective controlled ROP of a specific family of racemic functional β-lactones, namely 4-alkoxymethylene-β-propiolactones (BPL(OR) s). This process is catalyzed by an yttrium complex stabilized by a nonchiral tetradentate amino alkoxy bisphenolate ligand _ONOO(R'2) ₍2-) , which features both a good activity and a high degree of control over the molar masses of the resulting functional poly(3-hydroxyalkanoate)s. A simple modification of the R' substituents in ortho and para position on the ligand platform allows for a complete reversal from virtually pure syndioselectivity (Ps up to 0.91 with R'=cumyl) to very high isoselectivity (Pi…
Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands
Abstract Dioxomolybdenum(VI) complex [MoO 2 Cl 2 (dmso) 2 ] reacts with a series of tetradentate O 3 N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(L n )]. The reaction of H 3 L 1 produces [MoOCl(L 1 )] as two separable isomers, whereas the reaction of H 3 L 2 or H 3 L 3 yields a single product. The X-ray analyses of cis - and trans -[MoOCl(L 1 )] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.
Steric vs. electronic stereocontrol in syndio- or iso-selective ROP of functional chiral β-lactones mediated by achiral yttrium-bisphenolate complexes
International audience; Origins of stereoselectivity in ROP of racemic chiral cyclic esters promoted by achiral yttrium complexes, resulting in the formation of highly heterotactic polylactide, and highly syndiotactic or, more uniquely, highly isotactic poly(3-hydroxybutyrate)s, are discussed. A close interplay between the nature of the cyclic ester, most particularly of the exocyclic functional chain installed on the chiral center of β-lactones, and the ortho-substituents installed on the phenolate rings of the ligand, results in various determining secondary interactions of steric and also electronic nature.
QTAIM View of Metal-Metal Bonding in Di- and Trinuclear Disulfido Carbonyl Clusters
The experimental and theoretical charge densities in the sulfido-bridged cluster compounds Fe2(μ-S2)(CO)6 (1), Fe3(μ3-S)2(CO)9 (2), Mn2(μ-S2)(μ-CO)(CO)6 (3), and Fe2(μ-S2)(CO)5(PPh3) (4) have been studied using the quantum theory of atoms in molecules (QTAIM) methodology. High-resolution X-ray diffraction data have been measured for compounds 2–4 at 100 K. The topological analyses show that only in compounds 1 and 4 is there any evidence for metal–metal bonding in terms of the presence of a bond path. For compound 1, the topology of the Fe2S2 cage is highly dependent on the Fe–Fe separation, and the deformation along this vector is an extremely soft mode. The experimentally observed topolog…
Homoleptic Pnictogen-Chalcogen Coordination Complexes
The synthesis and structural characterization of dicationic selenium and tellurium analogues of the carbodiphosphorane and triphosphenium families of compounds are reported. These complexes, [Ch(dppe)][OTf]2 [Ch = Se, Te; dppe = 1,2-bis(diphenylphosphino)ethane; OTf = trifluoromethanesulfonate], are formed using [Ch]2+ reagents via a ligand-exchange protocol and represent extremely rare examples of homoleptic pnictogen → chalcogen coordination complexes. The corresponding arsenic compounds were also prepared, [Ch(dpAse)][OTf]2 [Ch = Se, Te; dpAse = 1,2-bis(diphenylarsino)ethane], exhibiting the first instance of an arsenic → chalcogen dative bond. The electronic structures of these unique c…
Synthesis of mono- and dihydroxy-substituted 2-aminocyclooctanecarboxylic acid enantiomers
Abstract (1R,2S,6R)-2-Amino-6-hydroxycyclooctanecarboxylic acid (−)-10 was synthesized from (1R,2S)-2-aminocyclooct-5-enecarboxylic acid (+)-2 via an iodolactone intermediate, while (1R,2S,3R,4S)-2-amino-5,6-dihydroxycyclooctanecarboxylic acid (−)-12 was prepared by using the OsO4-catalyzed oxidation of Boc-protected amino ester (−)-5. The stereochemistry and relative configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy (based on 2D NOE cross-peaks and 3J(H,H) coupling constants) and X-ray crystallography.
Alkyl and diether bridged N,N,N′,N′-tetra(2-hydroxybenzyl)diamines: effects of hydrogen bonding on structure and solubility
A solvent-free one-step method has been used to prepare two N,N,N′,N′-tetra(2-hydroxy-3,5-dimethylbenzyl)diaminoalkanes containing a long n-alkyl bridge (6 and 8 CH2 groups between N-atoms). In addition, three novel N,N,N′,N′-tetra(2-hydroxy-5-alkyl-3-alkylbenzyl)-diaminoalkane-ethers (alkyl = methyl or t-butyl) have been prepared using the same method. The compounds were studied in the solid state using single crystal X-ray diffraction and their solubility was studied using UV/Vis spectroscopy. In the solid state, hydrogen bonding plays a key role in controlling the crystal packing and conformations of the molecules, thus affecting the solubility and properties of the compounds.
A three-coordinate iron–silylene complex stabilized by ligand–ligand dispersion forces
The structural and bonding properties of a three-coordinate N-heterocyclic silyene (NHSi) complex of the iron(II) amide [Fe{N(SiMe3)2}2] are reported. Computational studies reveal that dispersion forces between the amido SiMe3 substituents and the isopropyl substituents on the NHSi ligand significantly enhance the stability of the complex, along with Fe-to-Si π-backbonding. peerReviewed
Synthesis, reactivity, and computational analysis of halophosphines supported by dianionic guanidinate ligands.
The reported chemistry and reactivity of guanidinate supported group 15 elements in the +3 oxidation state, particularly phosphorus, is limited when compared to their ubiquity in supporting metallic elements across the periodic table. We have synthesized a series of chlorophosphines utilizing homo- and heteroleptic (dianionic)guanidinates and have completed a comprehensive study of their reactivity. Most notable is the reluctancy of these four-membered rings to form the corresponding N-heterocyclic phosphenium cations, the tendency to chemically and thermally eliminate carbodiimide, and the scarcely observed ring expansion by insertion of a chloro(imino)phosphine into a P-N bond of the P-N-…
Synthesis, Reactivity, and Computational Analysis of Halophosphines Supported by Dianionic Guanidinate Ligands
The reported chemistry and reactivity of guanidinate supported group 15 elements in the +3 oxidation state, particularly phosphorus, is limited when compared to their ubiquity in supporting metallic elements across the periodic table. We have synthesized a series of chlorophosphines utilizing homo- and heteroleptic (dianionic)guanidinates and have completed a comprehensive study of their reactivity. Most notable is the reluctancy of these four-membered rings to form the corresponding N-heterocyclic phosphenium cations, the tendency to chemically and thermally eliminate carbodiimide, and the scarcely observed ring expansion by insertion of a chloro(imino)phosphine into a P–N bond of the P–N–…
Two C3-symmetric Dy3 III complexes with triple di-μ-methoxo-μ-phenoxo bridges, magnetic ground state, and single-molecule magnetic behavior
Two series of isostructural C3-symmetric Ln3 complexes Ln3·[BPh4] and Ln3·0. 33[Ln(NO3)6] (in which LnIII=Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that LnIII ions are connected by one μ2-phenoxo and two μ3-methoxo bridges, thus leading to a hexagonal bipyramidal Ln3O5 bridging core in which LnIII ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the DyIII ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To redu…
Icosahedral carboranes as scaffolds for congested regioselective polyaryl compounds: the distinct distance tuning of C–C and its antipodal B–B
Four-fold aryl substituted o-carborane derivatives with defined patterns of substitution at the antipodal region of the cluster carbon atoms have been achieved. It is proven that this region is congested but lacks steric hindrance. Also, the two antipodal sites Cc–Cc and B9–B12 are affected very distinctly by electron donor substituents.
Imidotungsten(VI) complexes with chelating phenols as ROMP catalysts
Abstract Tungsten(VI) complexes of the type [W(NPh)Cl3(L)] (L = chelating phenolate) were studied as catalyst precursors for ROMP of 2-norbornene, dicyclopentadiene and 5-vinyl-2-norbornene. These compounds form active catalysts when treated by ethyl magnesium bromide. Moreover, polymerisations can be run under ambient atmosphere without complicated inert atmosphere techniques. Synthesis and crystal structure of a new precursor complex [W(NPh)Cl3(LS)] (LS = 2,4-di-tert-butyl-6-(phenylthiomethyl)phenolate) are also described.
Experimental and computational studies of transition metal complexes with polydentate amino- and amidophenolate ligands : synthesis, structure, reactivity and magnetic properties
Chelating polydentate ligands play a key role in several areas of modern coordination chemistry. They can be exploited, for example, in catalysis, bioinorganic chemistry, heavy metal abstraction and molecular magnetism. Furthermore, compounds of this type can be found in natural chemicals, commercial products and industrial applications. In this dissertation, several 3d, 4d and 5d transition metal complexes with polydentate amino- and amidophenolate ligands were prepared and their structure, reactivity and magnetic properties were studied with experimental and computational techniques. In the first part of the dissertation, the solid-state structure, reactivity and magnetic properties of 12…
1‑Phenyl-3-(pyrid-2-yl)benzo[e][1,2,4]triazinyl: The First "Blatter Radical" for Coordination Chemistry
A neutral air- and moisture-stable N,N′-chelating radical ligand, 1-phenyl-3-(pyrid-2-yl)benzo[e][1,2,4]triazinyl (1) was synthesized and characterized by electron paramagnetic resonance spectroscopy, X-ray crystallography, and magnetic measurements. Subsequent reaction of 1 with Cu(hfac)2·2H2O (hfac = hexafluoroacetylacetonate) under ambient conditions afforded the coordination complex Cu(1)(hfac)2 in which the radical binds to the metal in a bidentate fashion. Magnetic susceptibility data collected from 1.8 to 300 K indicate a strong ferromagnetic metal-radical interaction in the complex and weak antiferromagnetic radical···radical interactions between the Cu(1)(hfac)2 units. Detailed com…
A cocrystal of two Mo(VI) complexes bearing different diastereomers of the 2,4-di-tert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]methyl}phenolate ligand derived from (+)-ephedrine
The title cocrystal contains two chiral conformational diastereomers, viz. (1S,2R,RN)- and (1S,2R,SN)-, of [2,4-ditert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]- methyl}phenolato](methanol)-cis-dioxidomolybdenum(VI), [Mo(C25H35NO2)O2(CH3OH)], representing the first example of a structurally characterized molybdenum complex with enantiomerically pure ephedrine derivative ligands. The MoVI cations exhibit differently distorted octahedral coordination environments, with two oxide ligands positioned cis to each other. The remainder of the coordination comprises phenoxide, alkoxide and methanol O atoms, with an amine N atom completing the octahedron. The distinct complexes are linked…
Single-molecule magnet behavior and magnetocaloric effect in ferromagnetically coupled LnIII-NiII-NiII-LnIII (LnIII = DyIII and GdIII) linear complexes
New types of linear tetranuclear LnIII-NiII-NiII-LnIII (LnIII = Dy (1), Gd (2)) complexes have been prepared using the multidentate ligand N,N′-bis(3-methoxysalicylidene)-1,3-diaminobenzene, which has two sets of NO and OO′ coordination pockets that are able to selectively accommodate NiII and LnIII ions, respectively. The X-ray structure analysis reveals that the NiII ions are bridged by phenylenediimine groups forming a 12-membered metallacycle in the central body of the complex, whereas the LnIII ions are located at both sides of the metallacycle and linked to the NiII ions by diphenoxo bridging groups. Phenylenediimine and diphenoxo bridging groups transmit ferromagnetic exchange intera…
Ferromagnetic dinuclear mixed-valence Mn(II)/Mn(III) complexes: building blocks for the higher nuclearity complexes. structure, magnetic properties, and density functional theory calculations.
A series of six mixed-valence Mn(II)/Mn(III) dinuclear complexes were synthesized and characterized by X-ray diffraction. The reactivity of the complexes was surveyed, and structures of three additional trinuclear mixed-valence Mn(III)/Mn(II)/Mn(III) species were resolved. The magnetic properties of the complexes were studied in detail both experimentally and theoretically. All dinuclear complexes show ferromagnetic intramolecular interactions, which were justified on the basis of the electronic structures of the Mn(II) and Mn(III) ions. The large Mn(II)-O-Mn(III) bond angle and small distortion of the Mn(II) cation from the ideal square pyramidal geometry were shown to enhance the ferromag…
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