Unraveling the Stereoisomer Configurations of 1,1'-bis(tert-butylphosphino)Ferrocene in the Gas Phase.

The molecular structure of a ferrocene derivative with adjacent centers of chirality, 1,1'-bis(tert-butylphosphino)ferrocene, has been examined in the gas phase using broadband microwave spectroscopy under the isolated and cold conditions of a supersonic jet. The diastereomers of 1,1'-bis(tert-butylphosphino)ferrocene can adopt homo- and hetero-chiral configurations, owing to the P-chiral substituents on the cyclopentadienyl rings. Moreover, the internal ring rotation of each diastereomer gives rise to four conformers with eclipsed ring arrangements, where the two tert-butylphosphino groups were separated by dihedral angles of approximately 72°, 144°, 216°, and 288° with respect to the two ring centers.

At the limits of bisphosphonio-substituted stannylenes.

Donor stabilization of Sn(II) and Pb(II) halides with 1,1'-ferrocenylene bridged bisphosphanes has been explored for Fe(CHP(CH)) (dppf), and Fe(CHPH(CH)). These bisphosphanes are reacted with SnBr and PbCl with and without additional Lewis acid (AlCl) forming acyclic and cyclic donor adducts from which the latter represent bisphosphoniotetrylenes. Since dynamic exchange in solution is observed, characterization includes solution and solid-state NMR in addition to SC-XRD, amended by DFT calculations.

A localized view on molecular dissociation via electron-ion partial covariance.

Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy.

Photoelectron circular dichroism of O 1s-photoelectrons of uniaxially oriented trifluoromethyloxirane: energy dependence and sensitivity to molecular configuration.

The photoelectron circular dichroism (PECD) of the O 1s-photoelectrons of trifluoromethyloxirane (TFMOx) is studied experimentally and theoretically for different photoelectron kinetic energies. The experiments were performed employing circularly polarized synchrotron radiation and coincident electron and fragment ion detection using cold target recoil ion momentum spectroscopy. The corresponding calculations were performed by means of the single center method within the relaxed-core Hartree-Fock approximation.

Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

A series of bis-[3]ferrocenophanes of the general type Fe(CHE')E-E(E'CH)Fe (E=P, SiH and E'=PBu, NPentyl, NSi(CH)) with an isolobal molecular framework have been prepared and characterized by heteronuclear NMR spectroscopy and X-ray crystallography. The thermal dissociation behavior with respect to homolytic fission of the central bond generating phosphorus centered radicals was investigated using EPR spectroscopy and quantum chemical calculations.

Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

Invited for this month's cover picture are the groups of Professors Rudolf Pietschnig at the University of Kassel, Professor Dietrich Gudat at the University of Stuttgart and Professor László Nyulászi at the Budapest University of Technology and Economics. The cover picture shows the thermally induced homolytic cleavage of the central P-P bond in a phosphorus-rich bis-ferrocenophane furnishing P-centered radicals (as evidenced by the computed spin-density highlighted in blue). The central P unit in the title compound is a structural analog of the connecting unit in Hittorf's violet phosphorus, which links the orthogonally arranged tubular entities.

A Stabilized Bisphosphanylsilylene and Its Heavier Congeners.

A bisphosphanylsilylene with [3]ferrocenophane backbone and its heavier analogues are described in the form of donor adducts. These heterocarbenes can be formed by dehydrochlorination (Si) or cycloreversion (Sn, Pb) using NHC (N-heterocyclic carbene) tetramethylimidazol-2-ylidene. The structures of the bisphosphanyl-silylene, -stannylene and -plumbylene NHC adducts are presented, and the bonding and stability of these compounds were elucidated using DFT calculations.

PBP bridged [3]ferrocenophane: a bisphosphanylborane with a redox trigger.

Stereospecific access to the unprecedented P-B-P bridged [3]ferrocenophane Fe(CHPtBu)BMes is presented. In contrast to acyclic ferrocenylphosphanes, we find evidence for a shift of spin-density from Fe to P upon pyramidal inversion of the P centers in the mono-cation; the latter has a lifetime of τ = 0.31(4) s.

[3]Ferrocenophanes with the bisphosphanotetryl bridge: inorganic rings on the way to tetrylenes.

A series of [3]ferrocenophanes with functional P-E-P motifs (E = group 14 fragments) is reported. Out of these, the silicon compounds with the general formula Fe(C5H4PtBu)2SiXY (XY = Cl2, Br2, I2, H2, HCl) have been characterized by spectroscopic means and the bonding situation was analyzed using X-ray crystallography and quantum chemical calculations. Despite the two stereogenic phosphanyl centers, most of the [3]ferrocenophanes have been obtained as single isomers in the course of stereospecific reactions.