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

Crystal structure of 1,1,2,2-tetramethyl-1,2-bis(2,3,4,5-tetramethylcyclopenta-2,4-dien-1-yl)disilane

The mol­ecular structure of the title compound, C22H38Si2, features a trans arrangement of the cyclo­penta­dienyl rings to avoid steric strain [C-Si-Si-C torsion angle = -179.0 (5)°]. The Si-Si bond length is 2.3444 (4) Å. The most notable inter­molecular inter­actions in the mol­ecular packing are C-H...[pi] contacts that lead to the formation of wave-like supra­molecular chains along the b axis

Ungewöhnliche Hafnacyclen im Vergleich mit deren Titan- und Zirconiumanaloga

Die vorliegende Arbeit beschäftigt sich mit der Synthese und den Reaktionen neuartiger Hafnacyclen, beispielsweise Hafnocen-Alkinkomplexen oder Hafnacyclocumulenen. Dabei werden die spektroskopischen und strukturellen Parameter sowie Reaktivitätsbefunde zum Vergleich mit ähnlichen Titan- und Zirconiumverbindungen herangezogen. In einigen Reaktionen zeigen Hafnocenverbindungen eine unerwartete Reaktivität, so finden z. B. bei der Synthese von Hafnocen-Alkinkomplexen C-O-, C-H- und Si-C-Bindungsaktivierungen statt, die in diesem Ausmaß zuvor für die Verbindungen der leichteren Homologen nicht beobachtet wurden. Weiterhin konnte gezeigt werden, dass die neuartigen Hafnocen-Alkinkomplexe als Ausgangsmaterial für die Synthese von in Katalysen relevanten Metallacyclen dienen können. Darüber hinaus gelang im Rahmen dieser Arbeit die Darstellung der ersten fünfgliedrigen Hafnacyclocumulene sowie eine erste Untersuchung der Reaktivität dieser Verbindungen.This Ph.D. thesis focuses on the synthesis and reactions of novel hafnacycles, e. g. hafnocene alkyne complexes or hafnacyclocumulenes. Spectroscopic and structural parameters as well as reactivity studies are used for comparison of these complexes with similar titanium and zirconium compounds. In some cases hafnocene compounds show an unexpected reactivity; for example in the synthesis of hafnocene alkyne complexes C-O, C-H and Si-C bond activations occur, which have not been observed to this extent for the lighter homologues. Moreover the results of this work show that the novel hafnocene alkyne complexes can provide a basis for the synthesis of catalytically relevant metallacycles. In addition, the synthesis of the first five-membered hafnycyclocumulene was achieved in this work as well as a first investigation of the reactivity of these compounds

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; Cp2MF2, 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 p?-d? 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

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 molecular structure of the title compound, C22H38Si2, features a trans arrangement of the cyclopentadienyl rings to avoid steric strain [C—Si—Si—C torsion angle = −179.0 (5)°]. The Si—Si bond length is 2.3444 (4) Å. The most notable intermolecular interactions in the molecular packing are C—H...π contacts that lead to the formation of wave-like supramolecular chains along the b axis

Crystal structure of tricarbonyl(N-diphenylphosphanyl-N,N′-diisopropyl-P-phenylphosphonous diamide-κ2P,P′)cobalt(I) tetracarbonylcobaltate(−I) toluene 0.25-solvate

The asymmetric unit of the title compound, [Co(C24H30N2P2)(CO)3][Co(CO)4]·0.25C7H8, consists of two crystallographically independent cations with similar conformations, two anions, and one-half of a toluene molecule disordered about an inversion centre. In the cations, a Co/P/N/P four-membered slightly bent metallacycle is the key structural element. The pendant NH group is not coordinated to the CoI atom, which displays a distorted trigonal–bipyramidal coordination geometry. Weak interionic hydrogen bonds are observed between the NH groups and a carbonyl group of the tetrahedral [Co(CO)4]− anions

{N,N-Bis[bis(2,2,2-trifluoroethoxy)phosphanyl]methylamine-κ2P,P′}bis(η5-cyclopentadienyl)titanium(II)

The title compound, [Ti(C5H5)2(C9H11F12NO4P2)], is a four-membered titanacycle obtained from the reaction of Cp2Ti(η2-Me3SiC2SiMe3) and CH3N[P(OCH2CF3)2]2 {N,N-bis[bis(trifluoroethoxy)phosphanyl]methylamine, tfepma}. The TiII atom is coordinated by two cyclopentadienyl (Cp) ligands and the chelating tfepma ligand in a strongly distorted tetrahedral geometry. The molecule is located on a mirror plane

Crystal structures of two ansa-titanocene trifluoromethanesulfonate complexes bearing the Me2Si(C5Me4)2 ligand

The crystal structures of two ansa-titanocene trifluoromethanesulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [dimethylbis(η5-tetramethylcyclopentadienyl)silane](trifluoromethanesulfonato-κ2O,O′)titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido[dimethylbis(η5-tetramethylcyclopentadienyl)silane](trifluoromethanesulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetrahedral geometry, with the trifluoromethanesulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π–π stacking interactions involving the toluene solvent molecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed

Low-Field Flow ³¹P NMR Spectroscopy for Organometallic Chemistry: On-Line Analysis of Highly Air-Sensitive Rhodium Diphosphine Complexes

Low-field flow NMR spectroscopy is a promising on-line technique for reaction monitoring. In the field of organometallic chemistry, involving air- and moisture-sensitive complexes, its application is however still limited. In particular, low-field flow 31P NMR spectroscopy is an attractive technique that could allow for routine benchtop monitoring of stoichiometric and catalytic transformations involving sensitive organophosphorus species. Herein, we present the practical aspects of the development of a customized low-field flow NMR setup and demonstrate its utility for reactions of highly oxygen-sensitive rhodium bis(phosphine) complexes, e.g., [Rh((S,S)-DIPAMP)(MeOH)2]BF4 and [Rh((R)-BINAP)(μ-Cl)]2. The investigation is carried out in real time under preparative conditions, allowing the formation of the desired organometallic species without degradation