Emanuel Hupf

Peri-Substituted (Ace)Naphthylphosphinoboranes. (Frustrated) Lewis Pairs

The synthesis and molecular structures of 1-(diphenylphosphino)-8-naphthyldimesitylborane (1) and 5-(diphenylphosphino)-6-acenaphthyldimesitylborane (2) are reported. The experimentally determined P-B peri distances of 2.162(2) and 3.050(3) Å allow 1 and 2 to be classified as regular and frustrated Lewis pairs. The electronic characteristics of the (non)bonding P-B contacts are determined by analysis of a set of real-space bonding indicators (RSBIs) derived from the theoretically calculated electron and pair densities. These densities are analyzed utilizing the atoms-in-molecules (AIM), stockholder, and electron-localizability-indicator (ELI-D) space partitioning schemes. The recently introduced mapping of the electron localizability on the ELI-D basin surfaces is also applied. All RSBIs clearly discriminate the bonding P-B contact in 1 from the nonbonding P-B contact in 2, which is due to the fact that the acenaphthene framework is rather rigid, whereas the naphthyl framework shows sufficient conformational flexibility, allowing shorter peri interations. The results are compared to the previously known prototypical phosphinoborane Ph3PB(C6F5)3, which serves as a reference for a bonding P-B interaction. The most prominent features of the nonbonding P-B contact in 2 are the lack of an AIM bond critical point, the unaffected Hirshfeld surfaces of the P and B atomic fragments, and the negligible penetration of the electron population of the ELI-D lone pair basin of the P atom into the AIM B atomic basin.

6-Diphenylphosphinoacenaphth-5-yl-mercurials as Ligands for d10 Metals. Observation of Closed-Shell Interactions of the Type Hg(II)···M; M = Hg(II), Ag(I), Au(I)

The salt metathesis reaction of ArLi with HgCl2 produced Ar2Hg (1, Ar = 6-Ph2P-Ace-5), which underwent complex formation with d(10)-configurated transition metal chlorides and triflates to give the complexes 1·HgCl2, 1·Hg(O3SCF3)2, 1·AgCl, 1·Ag(O3SCF3), [1·Ag(NCMe)2](O3SCF3), 1·AuCl, and [1·Au](O3SCF3) comprising significant metallophilic interactions between Hg(II) and Hg(II), Ag(I), and Au(I), respectively. The transmetalation reaction of ArSnBu3 with HgCl2 afforded ArHgCl (2) that also forms a complex with additional HgCl2, namely, 2·HgCl2, which however lacks metallophilic interactions. Compounds 2 and 1·HgCl2 possess the same elemental composition and can be interconverted in solution by choice of the solvent. In the presence of tetrahydrothiophene (tht), the complexes 1·AuCl and [1·Au](O3SCF3) underwent rearrangement into the Au(III) cation [cis-Ar2Au](+) ([3](+), which was isolated as Cl(-) and (O3SCF3)(-) salts) and elemental Hg. The reaction of 1·Hg(O3SCF3)2 with ArH produced the complex ArHg(ArH)(O3SCF3) (4). The metallophilic interactions are theoretically analyzed by a set of real-space bonding indicators derived from the atoms-in-molecules (AIM) and electron localizability indicator (ELI) space-partitioning schemes.

Understanding the Origin of Phosphorescence in Bismoles: A Synthetic and Computational Study

A series of bismuth heterocycles, termed bismoles, were synthesized via the efficient metallacycle transfer (Bi/Zr exchange) involving readily accessible zirconacycles. The luminescence properties of three structurally distinct bismoles were explored in detail via time-integrated and time-resolved photoluminescence spectroscopy using ultrafast laser excitation. Moreover, time-dependent density functional theory computations were used to interpret the nature of fluorescence versus phosphorescence in these bismuth-containing heterocycles and to guide the future preparation of luminescent materials containing heavy inorganic elements. Specifically, orbital character at bismuth within excited states is an important factor for achieving enhanced spin-orbit coupling and to promote phosphorescence. The low aromaticity of the bismole rings was demonstrated by formation of a CuCl π-complex, and the nature of the alkene-CuCl interaction was probed by real-space bonding indicators derived from Atoms-In-Molecules, the Electron Localizability Indicator, and the Non-Covalent Interaction index; such tools are of great value in interpreting nonstandard bonding environments within inorganic compounds.

Synthesis of 7,7,14,14-tetrachlorodinaphtho[1,8bc:1′,8′-fg][1,5]distannocine. Molecular structure of the di-water tetra-THF adduct

Abstract The salt metathesis reaction of 1,8-dilithionaphthalene with tributyltin chloride provided 1,8-bis(tributyltin)naphthalene (1) in 41% yield. The transmetallation of 1 with tin tetrachloride gave rise to the formation of 7,7,14,14-tetrachlorodinaphtho[1,8bc:1′,8′-fg][1,5]distannocine (2) in 75% yield. The molecular structure of 2·2 H2O·4 THF was established by single crystal X-ray crystallography.

Mapping the Trajectory of Nucleophilic Substitution at Silicon Using a peri-Substituted Acenaphthyl Scaffold

The second-order nucleophilic substitution (SN 2) reaction at a silicon atom is scrutinized by means of snapshots along a pseudoreaction coordinate. Phosphine and fluoride represent both attacking and leaving groups in the modeled SN 2 reaction. In the experimentally obtained 5-diphenylphosphinoacenaphth-6-yl-dimethylfluorosilane, 1, the phosphine and fluorosilane moieties are forced into immediate proximity through an acenaphthyl scaffold, that is, they exhibit peri interactions that serve as the model of the reactant ion-molecule complex and starting point for a theoretical potential-energy surface (PES) scan. Upon dissociation of fluoride, the experimentally obtained silylphosphonium cation 2 serves as a model of the product and end point of the PES scan. The pseudoreaction pathway is studied using geometric, energetic, spectroscopic, molecular-orbital, and topological real-space bonding indicators. It becomes evident that it is crucial to combine such methods to understand the pseudoreaction because they reveal different aspects based on different sensitivity to dispersive, electrostatic, and polar-covalent contributions to bonding, as shown by the reduced density gradient analysis. For example, atoms-in-molecules theory describes a late topological catastrophe, whereas the electron localizability indicator describes an early concerted reaction and natural resonance theory describes a more gradual change of properties. This case study encourages the use of a well-balanced toolbox equipped with complementary methods to emphasize different aspects of bonding.

Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2

Anisotropic atomic displacement parameters obtained separately from highly accurate X-ray and neutron diffraction data are compared, and it is established that Hirshfeld atom refinement of X-ray data can provide structural parameters that are as accurate as those from neutron data.

Aerobic Solid State Red Phosphorescence from Benzobismole Monomers and Patternable Self‐Assembled Block Copolymers

The synthesis of the first bismuth-containing macromolecules that exhibit phosphorescence in the solid state and in the presence of oxygen is reported. These red emissive high molecular weight polymers (>300 kDa) feature benzobismoles appended to a hydrocarbon scaffold, and were built via an efficient ring-opening metathesis (ROMP) protocol. Moreover, our general procedure readily allows for the formation of cross-linked networks and block copolymers. Attaining stable red phosphorescence with non-toxic elements remains a challenge and, thus, our new class of soluble (processable) polymeric phosphor is of great interest. Furthermore, the formation of bismuth-rich cores within organic-inorganic block copolymer spherical micelles is possible, leading to patterned arrays of bismuth in the film state.

Introducing iterative X-ray wavefunction refinement

Hirshfeld atom refinement (HAR)[1] is a structural refinement method of single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities, in contrast to spherical scattering factor used in the Independent Atom Model (IAM). The original HAR has been extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural leastsquares refinements, repeated until convergence. X-ray constrained wavefunction (XCW)[2] fitting as a separate technique overcomes the shortcomings of the theoretical ansatz used by including experimental observations (such as electron correlation or the crystal effect) into the wavefunction. In X-ray wavefunction refinement (XWR)[3] HAR is followed by an adjustment of the electronic wave function through XCW fitting. Similar to the implementation of an iterative procedure within HAR itself, a natural forward step of sophistication for XWR would be to directly incorporate the fitted wavefunction into a new HAR, obtain an improved geometry and improved ADPs and use this as input for another XCW fitting, and so on, until convergence in both energy and geometry: iterative XWR = HAR + XCW + HAR + XCW + ...