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The synthesis, structural characterization, and catalytic application of two novel aluminum complexes, [κ3ENSe−{Ph2P(E)N−C6H4−SePh}AlMe2] [E=S (1) and Se (2)] supported by new pincer‐type phenylselenium‐phosphanamidinate chalcogenide ligands are described. The molecular structures of both complexes in their solid states reveal a distorted trigonal bipyramidal geometry around the Al(III) ion, involving monoanionic ligand {Ph2P(E)N−C6H4−SePh}− bonded to the AlMe2‐motif in a tridentate manner. Complex 1 was found to be an effective pre‐catalyst for the cyanosilyation of aldehydes and ketones with TMSCN under solvent‐free conditions. The reaction protocol is simple, efficient, and has a diverse substrate scope of aldehydes and ketones, showing superior functional group tolerance. The kinetic study revealed that ketone reduction proceeded with first‐order dependence on ketone concentrations, TMSCN, and catalyst 1. [ABSTRACT FROM AUTHOR]

The synthesis, reactivity, and complexation with Fe(0) precursor of a tight‐bite bis(N‐heterocyclic silylene) (bis(NHSi)) ligand 1 are reported. The reaction of 1 with p‐toluidine led to the activation of both N−H bonds across Si(II) atoms to afford a four‐membered heterocyclic cyclodisilazane 2, with hydride substituents attached to five‐coordinate Si atoms. A 1 : 2 reaction of 1 with Fe(CO)5 led to an intriguing dinuclear complex 3 featuring a five‐membered (N−Si−Fe−Fe−Si) ring with a Fe−Fe bond distance of 2.6892(13) Å. All compounds (1‐3) were thoroughly characterized by various spectroscopic methods and X‐ray diffraction studies conclusively established their molecular structures. DFT calculations were carried out to shed light on bonding and energetic aspects in 1–3. [ABSTRACT FROM AUTHOR]

In search for structural features that enable the control of the valence isomerization of the fluxional bullvalene, a bullvalene‐bis(harmane) conjugate is identified that acts as chelating ligand in complexes with metal ions. Spectrometric titrations show that this ligand forms 1 : 1 complexes with Ag+, Cu+, Cu2+, and Zn2+. Most importantly, detailed NMR‐spectroscopic analysis at different temperatures reveals that the complexation with Ag+ strongly affects the dynamic isomerization of the bullvalene unit of the ligand such that only one predominant valence isomer is formed, even at 5 °C. Detailed 1H‐NMR‐spectroscopic studies disclose an increased barrier (~11 kJ mol−1) of the Cope rearrangement. Furthermore, the addition of hexacyclene displaces the Ag+ from the complex, so that the valence isomerization is accelerated and an equilibrium with two predominant isomers is formed. In turn, repeated addition of Ag+ regains the complex with the restrained isomerization of the bullvalene unit. This method to control the valence isomerism by straightforward chemical stimuli may be used to simplify structural analysis at elevated temperatures, i. e. a feature not available so far with bullvalenes, and it may be employed as functional element in dynamic supramolecular assemblies. [ABSTRACT FROM AUTHOR]

In this study, we compared carbene and pyridine substituted ligands {3‐Me‐1‐[2‐(CH2CH2SPh)]‐C7H4N2} (L1) and {2‐[(2,6‐iPr2‐C6H3)N=CH]‐6‐(MeO)C5H3N}(L2) for synthesis of ionic C,S‐ and N,N‐coordinated Ru (II) complexes [(κ2‐L1)RuCl(η6‐p‐cymene)]+Cl− (1), [(κ2‐L1)RuI(η6‐p‐cymene)]+I− (2), and [(κ2‐L2)RuCl(η6‐p‐cymene)]+Cl− (3), respectively. Stannylene ligand [{2,6‐(Me2NCH2)2C6H3}SnCl] (L3), as heavy carbene analog, was also used in this study to prepare neutral Sn‐coordinated Ru (II) complex [(κ1‐L3)RuCl2(η6‐p‐cymene)] (4). Finally, reaction of SnCl2 with 1, 3, and 4 was also studied to yield [(κ2‐L1)RuCl(η6‐p‐cymene)]+[SnCl3]− (5), [(κ2‐L2)RuCl(η6‐p‐cymene)]+[SnCl3]− (6), and [(κ1‐L3)RuCl (SnCl3)(η6‐p‐cymene)] (7). The catalytic activity of 1–7 was tested on aerobic oxidation of benzylamine. The effect of different ligands L1–3 as well as the effect of the SnCl3− moiety is discussed. [ABSTRACT FROM AUTHOR]

Chelating phosphines have long been a mainstay as efficient directing ligands in transition‐metal catalysis. Low‐valent derivatives, namely chelating phosphinidenes, are to date unknown, and could lead to chelating complexes containing more than one metal centre due to the intrisic capacity of phosphinidenes to bind two metal fragments at one P‐centre. Here we describe the synthesis of the first such chelating bis‐phosphinidene ligand, XantP2 (2), generated by the reduction of a diphosphino xanthene derivative, Xant(PH2)2 (1) with iPrNHC (iPrNHC=[:C{N(iPr)C(H)}2]). Initial studies have shown that this novel chelating ligand can act as a bidentate ligand towards element dihalides (i.e. FeCl2, ZnI2, GeCl2, SnBr2), forming cationic complexes with the tetryl elements. In contrast, XantP2 demonstrates an ability to bind multiple metal centres in the reaction with CuCl, leading to a cationic Cu3P3 ring complex, with Cu centres bridged by phosphinidene arms. Density Functional Theory calculations show that 2 indeed holds 4 lone pairs of electrons, shedding further light on the coordination capacity for this novel ligand class through observation of directionality and hybridisation of these electron pairs. [ABSTRACT FROM AUTHOR]

Nucleophilic attack on complex [RuCl(η6‐C10H14){κ3(P,C,C)‐Ph2PCH2CH=CH2}][BPh4] (2) takes place, either to the metal or to the coordinated olefin depending on the nucleophile and the reaction conditions. The nucleophilic attack of phosphanes on the coordinated olefin leads diastereoselectively to complexes [RuCl(η6‐C10H14){ĸ2(P,C)‐Ph2PCH2CH(PR3)CH2}]+ bearing κ2(P,C)‐ligands obtained as a racemic mixture of the enantiomers RRuSc/SRuRC. These kinetically stable isomers, undergo an isomerization process leading to the thermodynamically stable products isolated as the diastereoisomer RRuRC/SRuSC. 31P{1H} NMR monitoring experiments on the isomerization processes have been carried out. New Ru complexes containing bidentate κ2(P,C)‐ligands [RuCl(η6‐C10H14){ĸ2(P,C)‐Ph2PCH2CH(PR3)CH2}][BPh4] have been diastereoselectively synthesized as the kinetically stable isomer (RRuSC/SRuRC). This diastereoisomer spontaneously evolves to the thermodynamically stable diastereoisomer (RRuRC/SRuSC). 31P{1H} NMR monitoring experiments shed light on the isomerization processes. [ABSTRACT FROM AUTHOR]

Substitution at a B-H unit of the heteroborate cluster stanna- closo-dodecaborate [SnB11H11]2- at the upper belt of the icosahedron by one of the triarylphosphine moieties of xantphos was carried out under the catalysis of palladium acetate. The resulting coupling product is a monoanion offering two coordination sites: a low-valent tin-cluster vertex and a triaryl phosphine moiety. The basicity and nucleophilicity of the anion were investigated in reactions with a strong acid or an alkylating agent. Transition-metal electrophiles like platinum halide PtCl2 or rhodium carbonyl [Rh(CO)2Cl]2 react with the bidentate ligand, with the formation of cis-coordination products. [ABSTRACT FROM AUTHOR]

Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡C tBu)(CH2 tBu)3 with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2−)(≡SiO−)W(≡CH tBu)(CH2 tBu)2] and [(≡SiNH2−)(≡SiO−)W(=CH tBu)2(CH2 tBu). Variable temperature, 1H-1H 2D double-quantum, 1H-13C HETCOR, and HETCOR with spin diffusion solid-state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(≡Si−OH)(≡Si−NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface-complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 °C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl-supported catalysts. [ABSTRACT FROM AUTHOR]

The syntheses of lithium and alkaline earth metal complexes with the bis(borane-diphenylphosphanyl)amido ligand ( 1- H) of molecular formulas [{ κ2-N(PPh2(BH3))2}Li(THF)2] ( 2) and [{κ3-N(PPh2(BH3))2}2 M(THF)2] [( M = Ca ( 3), Sr ( 4), Ba ( 5)] are reported. The lithium complex 2 was obtained by treatment of bis(borane-diphenylphosphanyl)amine ( 1- H) with lithium bis(trimethylsilyl)amide in a 1:1 molar ratio via the silylamine elimination method. The corresponding homoleptic alkaline earth metal complexes 3- 5 were prepared by two synthetic routes - first, the treatment of metal bis(trimethylsilyl)amide and protio ligand 1- H via the elimination of silylamine, and second, through salt metathesis reaction involving respective metal diiodides and lithium salt 2. The molecular structures of lithium complex 2 and barium complex 5 were established by single-crystal X-ray diffraction analysis. In the solid-state structure of 2, the lithium ion is ligated by amido nitrogen atoms and hydrogen atoms of the BH3 group in κ2-coordination of the ligand 1 resulting in a distorted tetrahedral geometry around the lithium ion. However, in complex 5, κ3-coordination of the ligand 1 was observed, and the barium ion adopted a distorted octahedral arrangement. The metal complex 5 was tested as catalyst for the ring opening polymerization of ϵ-caprolactone. High activity for the barium complex 5 towards ring opening polymerization (ROP) of ϵ-caprolactone with a narrow polydispersity index was observed. Additionally, first-principle calculations to investigate the structure and coordination properties of alkaline earth metal complexes 3- 5 as a comparative study between the experimental and theoretical findings were described. [ABSTRACT FROM AUTHOR]

The amino substituted bidentate chelating ligand 2-amino-5-(2-pyridyl)-1,3,4-thiadiazole (H2 L) was used to prepare 3:1-type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [FeII(H2 L)3](ClO4)2·0.6MeOH·0.9H2O a 1:1 mixture of mer and fac isomers is present whereas [FeII(H2 L)3](BF4)2·MeOH·H2O, [CoII(H2 L)3](ClO4)2·2H2O and [NiII(H2 L)3](ClO4)2·MeOH·H2O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [FeII(H2 L)3]2+ complex core to exist in the low-spin state, whereas the [CoII(H2 L)3]2+ complex core resides in its high-spin state, even at very low temperatures. [ABSTRACT FROM AUTHOR]

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole ( L1H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L1 2 SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L1 2 SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L1 2 SiCl2, L1 2 SiF2, L1 2 Si(OTf)2, L1 2 SiPhCl, and L1 2 SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L1 3 Si+ and L1 2 SiPh+ were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L1 2 SiCl2 with a third equivalent of L1H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated CC coupling of two ligands L1. [ABSTRACT FROM AUTHOR]

The reaction involving N-aryliminopyrrolyl ligand, 2-(( p-Me-C6H3N=CMe)-C4H3NH) ( 1a) (ImpMe-H), and Zr(O tBu)4 in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(ImpMe)2Zr(O tBu)2] ( 2a) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2-((2,6- iPr2C6H3N=CH)-C4H3NH) ( 1b) (ImpDipp-H) and Zr(O tBu)4 in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(ImpDipp)Zr(O tBu)3(THF)] ( 2b), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single-crystal X-ray diffraction analysis. The solid-state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert-butoxide ligands attached to the central metal atom. [ABSTRACT FROM AUTHOR]

We report on the first homoleptic tetrakis(silyl) complexes of zerovalent Group 10 metals. The compounds [MLi4{Si(3,5-Me2pz)3}4] (M=Pd and Pt; 3,5-Me2pz=3,5-dimethylpyrazolyl) exhibit very appealing metal-centred heterocubane structures with the central d10 metal atoms surrounded by four silicon and four lithium atoms. Both compounds were characterised in detail, including X-ray crystal-structure analysis and 2D NMR spectroscopic methods such as 7Li,29Si and 7Li,195Pt HMQC. Cyclic voltammetry studies, in combination with density functional theory (DFT) calculations, revealed that the corresponding mononuclear cationic d9-MI and dicationic d8-MII complexes are accessible by stepwise one-electron oxidation of the title compounds. Electron paramagnetic resonance (EPR) investigations provided evidence for the existence of the corresponding paramagnetic palladium(I) and platinum(I) complexes. [ABSTRACT FROM AUTHOR]

The dinuclear phenoxido-bridged nickel(II) complex [{Ni(Hsalhyph)Cl(H2O)}2] with the hydrazone ligand H2salhyph, derived from salicylaldehyde and benzoic acid hydrazide, has been synthesized and structurally characterized. The dinuclear Ni2O2 core unit of the complex facilitates the formation of intramolecular O-H ···Cl hydrogen bonds. The chlorido ligand is involved in additional N-H ···Cl hydrogen bonding leading to an aggregation of the dinuclear complexes forming one-dimensional staged chains. Within the chains the supramolecular structure is governed by hydrogen bonding and π-π-stacking interactions. In the crystal structure two additional DMF molecules of crystallization are present per dinuclear complex. The DMF molecules are located between the chains and involved in O-H ···O=C hydrogen bonding with the aqua ligands of the dinickel core. Magnetic susceptibility measurements show the presence of antiferromagnetic exchange interactions ( H = - JS1 S2) with J = -14.8 cm-1 between the nickel(II) ions and indicate a zero-field-splitting of D = 12.6 cm-1. [ABSTRACT FROM AUTHOR]

The aminophosphane ligand 1-amino-2-(diphenylphosphanyl)ethane [Ph2P(CH2)2NH2] reacts with dichloridotris(triphenylphosphane)ruthenium(II), [RuCl2(PPh3)3], to form chloridobis[2-(diphenylphosphanyl)ethanamine-κ2 P, N](triphenylphosphane-κ P)ruthenium(II) chloride toluene monosolvate, [RuCl(C18H15P)(C14H16NP)2]Cl·C7H8 or [RuCl(PPh3){Ph2P(CH2)2NH2}2]Cl·C7H8. The asymmetric unit of the monoclinic unit cell contains two molecules of the RuII cation, two chloride anions and two toluene molecules. The RuII cation is octahedrally coordinated by two chelating Ph2P(CH2)2NH2 ligands, a triphenylphosphane (PPh3) ligand and a chloride ligand. The three P atoms are meridionally coordinated, with the Ph2P- groups from the ligands being trans. The two -NH2 groups are cis, as are the chloride and PPh3 ligands. This chiral stereochemistry of the [RuCl(PPh3){Ph2P(CH2)2NH2}2]+ cation is unique in ruthenium-aminophosphane chemistry. [ABSTRACT FROM AUTHOR]

The coordination behaviour of 3,5-di(2-pyridyl)-1,2,4-oxadiazole ( L′) has been studied and compared with that of the 2,5-di(2-pyridyl)-1,3,4-chalcadiazoles LO, LS and LSe [ LO = 2,5-di(2-pyridyl)-1,3,4-oxadiazole, LS = 2,5-di(2-pyridyl)-1,3,4-thiadiazole, LSe = 2,5-di(2-pyridyl)-1,3,4-selenadiazole]. Ligand L′ and the new complexes [CuII( L′)3](ClO4)2 ·1.5MeOH ·H2O ( 1·1.5MeOH ·H2O), 1·MeCN, [CoII( L′)2(MeOH)2](ClO4)2 ( 2), [CoII( LO)2(MeOH)2](ClO4)2 ( 3), [CuII( L′)2Cl2] ( 4), [CuII( L′)2Br2] ( 5) and [CuII( LSe)2Cl2] ·MeOH ( 6·MeOH) have been structurally characterised by single-crystal X-ray diffraction analyses. With the help of DFT calculations and the analyses of metal-ligand bond lengths of similar complexes of L′, LO, LS and LSe the binding capacities have been determined as L′ << LO < LS < LSe. [ABSTRACT FROM AUTHOR]

The cobalt(II) complex [CoCl2(2, 6- iPrC6H3-BIAO)]2 ( 1) of rigid unsymmetrical imine, carbonyl mixed ligand [ N-(2, 6-diisopropylphenyl)-imino]acenapthenone] (2, 6- iPrC6H3-BIAO) ( L1) can be achieved by the reaction of CoCl2 and neutral [ N-(2, 6-diisopropylphenyl)-imino]acenapthenone] ligand. When ligand L1 reacted with CuCl in dichloromethane solution, only nitrogen coordinated copper complex [CuCl(2, 6- iPrC6H3-BIAO)] ( 2) was obtained. In the solid-state structure, compound 1 is dimeric through the chelating two μ2 chlorine atoms and each cobalt atom adopts either a distorted trigonal bipyramidal or a distorted square pyramidal arrangement. In contrast, the molecular structure of compound 2 reveals that copper is coordinated by imino nitrogen and adopts a linear arrangement around the central metal atom. The crystal structure of the rigid bidentate mixed nitrogen and oxygen ligand (2, 6- iPrC6H3-BIAO) ( L1) is also reported. [ABSTRACT FROM AUTHOR]

The article investigates the influence of chelating ligands on arsenic and iron absorption of hydroponically grown rice seedlings (Oryza sativa L.). Rice seeds were treated with chelating ligands, which were composed of chemicals such as ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS) and hydroxyiminodisuccinic acid (HIDS), and a solution of Arsenate. Studies showed that EDTA, EDDS and HIDS solubilized arsenic from ferrous oxide of the root surfaces of the plants, resulting to the increase in its uptake into the roots. The study concludes that, because of their biodegradability, EDDS and HIDS are a safer choice that the non-biodegradable EDTA.

Metal‐centred heterocubane structures characterise the homoleptic tetrakis(silyl) complexes of zerovalent palladium and platinum, [MLi4{Si(3,5‐Me2pz)3}4] (3,5‐Me2pz=3,5‐dimethylpyrazole; M=Pd or Pt), in which the central d10 metal atom is surrounded by four silicon and four lithium atoms. Cyclic voltammetry shows that the corresponding cationic d9 MI and dicationic d8 MII complexes are accessible through one‐electron oxidation processes. For more details, see the Full Paper by F. Breher et al. on page 17899 ff. [ABSTRACT FROM AUTHOR]