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Crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand
The crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [di-methylbis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ2O,O')titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido-[di-methyl-bis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.
Crystal structure of 1-hydroxy-2,2,6,6-tetramethylpiperidin-1-ium trifluoromethanesulfonate
In the cation of the title salt, C9H20NO+·CF3O3S-, the six-membered heterocyclic ring displays a chair conformation. In the crystal, centrosymmetric pairs of cations and anions are linked by N-H...O and O-H...O hydrogen bonds to form rings with a R44(14) graph-set motif.
The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptors
The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C5NF4)(PR3)2], R = Et 1a, Cy 1b, trans-[Pd(F)(4-C5NF4)(PCy3)2] 2, trans-[Pt(F){2-C5NF2H(CF3)}(PCy3)2] 3 and of group 4 difluorides (Cp2MF2, M = Ti 4a, Zr 5a, Hf 6a; Cp*2MF2, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability β (Hunter scale) for the group 10 metal fluorides is far greater (1a 12.1, 1b 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, 5a 4.7, 6a 4.7, 4b 6.9, 5b 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me3NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to 1a in carbon tetrachloride (−23.5 ± 0.3 kJ mol–1) interlocks our study with Laurence’s scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of pπ–dπ bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C5NF3(NH2)}(PEt3)2], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.
Crystal structure of 1,1,2,2-tetramethyl-1,2-bis(2,3,4,5-tetramethylcyclopenta-2,4-dien-1-yl)disilane
The molÂecular structure of the title compound, C22H38Si2, features a trans arrangement of the cycloÂpentaÂdienyl rings to avoid steric strain [C-Si-Si-C torsion angle = -179.0 (5)°]. The Si-Si bond length is 2.3444 (4) Ã…. The most notable interÂmolecular interÂactions in the molÂecular packing are C-H...[pi] contacts that lead to the formation of wave-like supraÂmolecular chains along the b axis.
Highly selective visible light-induced Ti–O bond splitting in an ansa-titanocene dihydroxido complex
Irradiation of a substituted ansa-titanocene(IV) dihydroxido complex with visible light induces Ti–O bond dissociation. In contrast to previous studies on structurally similar unbridged complexes, no side reactions are observed and formation of the Ti(III) species is highly selective. The formation of OH radicals was proved using a biradicaloid species.
1-Titanacyclobuta-2,3-diene-an elusive four-membered cyclic allene
The synthesis of an unusual 1-metalla-2,3-cyclobutadiene complex [rac-(ebthi)Ti(Me3SiC3SiMe3)] (rac-ebthi = rac-1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)), a formal metallacyclic analogue of a non-existent four-membered 1,2-cyclobutadiene, is described. By variation of the cyclopentadienyl ligand of the titanocene precursor it was possible to stabilise this highly exotic compound which selectively reacts with ketones and aldehydes to yield enynes by oxygen transfer to titanium. Analysis of the bonding and electronic structure of the metallacycle shows that the complex is best described as an unusual antiferromagnetically coupled biradicaloid system, possessing a formal Ti(iii) centre coordinated with a monoanionic radical ligand. © 2019 The Royal Society of Chemistry.
Synthesis and crystallographic characterization of [2,2-bisÂ(η5-pentaÂmethylÂcycloÂpentaÂdienÂyl)-3,4-bis(triÂmethylÂsilÂyl)-2-zirconaÂfuran-5-one-κO5]triisobutylÂaluminium
The crystal structure of the title zwitterionic zirconocene complex containing a furanÂone unit, [AlZr(C10H15)2(C4H9)3(C9H18O2Si2)], is reported. On reacting a zirconaÂfuranÂone with two equivalents of HAl(i-Bu)2, disproportionation of the Lewis acid results in the formation of a triisoÂbutylÂaluminium fragment, Al(i-Bu)3, which coordinates to the exocyclic carbonyl O atom of the zirconaÂfuranÂone ring. Single-crystal X-ray diffraction reveals that the zirconaÂfuranÂone ring remains intact with coordination of the aluminium to the exocyclic O atom. One of the i-butyl groups is disordered over two sets of sites, with an occupancy ratio of 0.731 (3):0.269 (3).
A Comparative Study on the Thermodynamics of Halogen Bonding of Group 10 Pincer Fluoride Complexes
The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R2-tBuPOCOPtBu)MF] (3,5-R2-tBuPOCOPtBu=κ3-C6HR2-2,6-(OPtBu2)2 with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
Room temperature synthesis of an amorphous MoS2 based composite stabilized by N-donor ligands and its light-driven photocatalytic hydrogen production
Herein an entirely new and simple room temperature synthesis of an amorphous molybdenum sulfide stabilized by complexing ammonia and hydrazine is reported. The resulting material exhibits an outstanding activity for the photocatalytic hydrogen evolution driven by visible light. It is chemically stable during the reaction conditions of the photocatalysis and shows unusual thermal stability up to 350 °C without crystallization. The new material is obtained by a reaction of solid ammonium tetrathiomolybdate and gaseous hydrazine. In the as-prepared state Mo atoms are surrounded by μ2-briding S2−, NH3 and hydrazine, the latter being coordinated to Mo(IV) in a bridging or side-on mode. Heating at 450 °C or irradiation with an electron beam generates nanosized crystalline MoS2 slabs. The two modes for crystallization are characterized by distinct mechanisms for crystal growth. The stacking of the slabs is low and the material exhibits a pronounced turbostratic disorder. Heat treatment at 900 °C yields more ordered MoS2 but structural disorder is still present. The visible-light driven hydrogen evolution experiments evidence an outstanding performance of the as-prepared sample. The materials were thoroughly characterized by optical spectroscopy, chemical analysis, in situ HRTEM, XRD, 1H and 15N solid-state NMR, XPS, and thermal analysis.