Photochemistry with Chlorine Trifluoride: Syntheses and Characterization of Difluorooxychloronium(V) Hexafluorido(non)metallates(V), [ClOF2][MF6] (M=V,Nb, Ta,Ru, Os,Ir, P,Sb)

A photochemical route to salts consisting of difluorooxychloronium(V) cations, [ClOF₂]⁺, and hexafluorido(non)metallate(V) anions, [MF₆]⁻ (M=V, Nb, Ta, Ru, Os, Ir, P, Sb) is presented. As starting materials, either metals, oxygen and ClF₃ or oxides and ClF₃ are used. The prepared compounds were characterized by single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures of [ClOF₂][MF₆] (M=V, Ru, Os, Ir, P, Sb) are layer structures that are isotypic with the previously reported compound [ClOF₂][AsF₆], whereas for M=Nb and Ta, similar crystal structures with a different stacking variant of the layers are observed. Additionally, partial or full O/F disorder within the [ClOF₂]⁺ cations of the Nb and Ta compounds occurs. In all compounds reported here, a trigonal pyramidal [ClOF₂]⁺ cation with three additional Cl⋅⋅⋅F contacts to neighboring [MF₆]⁻ anions is observed, resulting in a pseudo-octahedral coordination sphere around the Cl atom. The Cl−F and Cl−O bond lengths of the [ClOF₂]⁺ cations seem to correlate with the effective ionic radii of the M^V ions. Quantum-chemical, solid-state calculations well reproduce the experimental Raman spectra and show, as do quantum-chemical gas phase calculations, that the secondary Cl⋅⋅⋅F interactions are ionic in nature. However, both solid-state and gas-phase quantum-chemical calculations fail to reproduce the increases in the Cl−O bond lengths with increasing effective ionic radius of M in [MF₆]⁻ and the Cl−O Raman shifts also do not generally follow this trend.     

Heterocumulene Sulfinyl Radical OCNSO

Neutral five‐atomic cumulenes formally consisting of two pseudohalogens (e.g., NCO, NNN, NSO) by sharing the central nitrogen atom are exotic species that have been barely studied. Through flash vacuum pyrolysis of CF₃S(O)NCO at ca. 1200 K, sulfinyl isocyanate, bearing resonance structures of O=C−N=S=O and O=C=N−S=O, has been generated in the gas phase and subsequently characterized in cryogenic matrices (Ar and N₂). Its reversible conformational (syn and anti) interconversion and photodecomposition were observed.     

Equilibrium conformation of dimethylaminodichlorophosphine molecule: the use of the results of quantum-chemical calculations and spectroscopic measurements in the analysis of gas-phase electron diffraction data

Geometric parameters and force fields of two stable isomers of dimethylaminodichlorophosphine molecule, a gauche-conformer with C₁ symmetry (A) and anti-conformer with C _s symmetry (D), resulting from internal rotation about the P—N bond, were calculated in the RHF/6-31G* approximation. Using the scaled quantum-chemical force field for the most stable conformer A, the first reliable interpretation of the vibrational spectra of the light and perdeuterated isotopomers of dimethylaminodichlorophosphine was obtained. The root-mean-square vibrational amplitudes, harmonic and anharmonic vibrational corrections, and centrifugal distortion corrections were also calculated. Structural analysis of electron diffraction data was performed with consideration of nonlinear kinematic effects at the first-order level of perturbation theory. The experimental values of the equilibrium geometric parameters were estimated. The results obtained suggest a nonplanar equilibrium configuration of the amino group in the dimethylaminodichlorophosphine molecule.     

Metal⋅⋅⋅F−C Bonding in Low-Coordinate Alkaline Earth Fluoroarylamides

A set of calcium and barium complexes containing the fluoroarylamide N(C₆F₅)₂⁻ is presented. These compounds illustrate the key role of stabilising M⋅⋅⋅F−C secondary interactions in the construction of low-coordinate alkaline earth complexes. The nature of Ca⋅⋅⋅F−C bonding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysis and DFT computations. The molecular structures of [Ca{N(C₆F₅)₂}₂(Et₂O)₂] ( 4 ′), [Ca{μ-N(SiMe₃)₂}{N(C₆F₅)₂}]₂ ( 5₂ ), [Ba{μ-N(C₆F₅)₂}{N(C₆F₅)₂}⋅toluene]₂ ( 6₂ ), [{BDI^DiPP}CaN(C₆F₅)₂]₂ ( 7₂ ), [{N^N^DiPP}CaN(C₆F₅)₂]₂ ( 8₂ ), and [Ca{μ-OB(CH(SiMe₃)₂)₂}{N(C₆F₅)₂}]₂ ( 9₂ ), where {BDI^DiPP}⁻ and {N^N^DiPP}⁻ are the bidentate ligands CH[C(CH₃)NDipp]₂⁻ and DippNC₆H₄CNDipp⁻ (Dipp=2,6-iPr₂-C₆H₃), are detailed. Complex 6₂ displays strong Ba⋅⋅⋅F−C contacts at around 2.85 Å. The calcium complexes feature also very short intramolecular Ca−F interatomic distances at around 2.50 Å. In addition, the three-coordinate complexes 7₂ and 8₂ form dinuclear structures due to intermolecular Ca⋅⋅⋅F−C contacts. BVS analysis shows that Ca⋅⋅⋅F−C interactions contribute to 15–20 % of the bonding pattern around calcium. Computations demonstrate that Ca⋅⋅⋅F−C bonding is mostly electrostatic, but also contains a non-negligible covalent contribution. They also suggest that Ca⋅⋅⋅F−C are the strongest amongst the range of weak Ca⋅⋅⋅X (X=F, H, C_π) secondary interactions, due to the high positive charge of Ca²⁺ which favours electrostatic interactions.     

Confinement inside a Crystalline Sponge Induces Pyrrole To Form N−H⋅⋅⋅π Bonded Tetramers

Based on the DFT-level-calculated molecular volume (V_mol) of pyrrole and its liquid density, pyrrole manifests the highest liquid density coefficient LD_c (defined as [V_mol×density ×0.6023]/FW) value of 0.7. Normal liquids have LD_c <0.63. This very high LD_c is due to the strong N−H⋅⋅⋅π interactions in solution, and hence pyrrole can be considered to be a pseudo-crystalline liquid. When trapped inside the confined space of a crystalline sponge, a reorientation of the N−H⋅⋅⋅π interaction is observed leading to specific cyclic N−H⋅⋅⋅π tetramers and N−H⋅⋅⋅π dimers, as verified by single-crystal X-ray crystallographic and computational methods. These tetramers are of the same size as four pyrrole molecules in the solid-state of pyrrole, yet the cyclic N−H⋅⋅⋅π intermolecular interactions are circularly oriented instead of being in the linear zigzag structure found in the X-ray structure of a solid pyrrole. The confinement thus acts as an external driving force for tetramer formation.     

Pressure‐Induced Enhancement of Magnetic‐Ordering Temperature in an Organic Radical to 70 K: A Magnetostructural Correlation

The structure of the canted antiferromagnet β‐p‐NCC₆F₄CNSSN ( 1 ) was determined from synchrotron powder‐diffraction studies in the pressure range 0–21.6 kbar. Radical 1 crystallizes in the orthorhombic space group Fdd2, but undergoes an asymmetric contraction of the unit‐cell size with increasing pressure. At the molecular level, this contraction of the unit cell is simultaneously accommodated by: 1) an increase in twist angle between aryl and heterocyclic rings; and 2) a shortening of the intermolecular S ??? N contacts, which propagate the magnetic‐exchange pathway. DFT calculations based on the structures in this pressure range revealed an increase in the magnetic‐exchange interaction (J) with increasing pressure, and an excellent correlation was observed between J and the magnetic‐ordering temperature, which increased from 36 K at ambient pressure up to 70 K at 16 kbar.     

Experimental Quantification of Halogen⋅⋅⋅Arene van der Waals Contacts

Crystallographic and computational studies suggest the occurrence of favourable interactions between polarizable arenes and halogen atoms. However, the systematic experimental quantification of halogen⋅⋅⋅arene interactions in solution has been hindered by the large variance in the steric demands of the halogens. Here we have synthesized molecular balances to quantify halogen⋅⋅⋅arene contacts in 17 solvents and solvent mixtures using ¹H NMR spectroscopy. Calculations indicate that favourable halogen⋅⋅⋅arene interactions arise from London dispersion in the gas phase. In contrast, comparison of our experimental measurements with partitioned SAPT0 energies indicate that dispersion is sufficiently attenuated by the solvent that the halogen⋅⋅⋅arene interaction trend was instead aligned with increasing exchange repulsion as the halogen increased in size (ΔG_X⋅⋅⋅_Ph=0 to +1.5 kJ mol⁻¹). Halogen⋅⋅⋅arene contacts were slightly less disfavoured in solvents with higher solvophobicities and lower polarizabilities, but strikingly, were always less favoured than CH₃⋅⋅⋅arene contacts (ΔG_Me⋅⋅⋅_Ph=0 to −1.4 kJ mol⁻¹).     

Hydrogen versus fluorine: effects on molecular structure and intermolecular interactions in a platinum isocyanate complex

At the molecular level, the enantiomerically pure square‐planar organoplatinum complex (SP‐4‐4)‐(R)‐[2‐(1‐aminoethyl)‐5‐fluorophenyl‐κ²C¹,N][(R)‐1‐(4‐fluorophenyl)ethylamine‐κN](isocyanato‐κN)platinum(II), [Pt(C₈H₉FN)(NCO)(C₈H₁₀FN)], and its congener without fluorine substituents on the aryl rings adopt the same structure within error. The similarities between the compounds extend to the most relevant intermolecular interactions, i.e. N—H…O and N—H…N hydrogen bonds link neighbouring molecules into chains along the shortest lattice parameter in each structure. Differences between the crystal structures of the fluoro‐substituted and parent complex become obvious with respect to secondary interactions perpendicular to the classical hydrogen bonds; the fluorinated compound features short C—H…F contacts with an F…H distance of ca 2.6 Å. The fluorine substitution is also reflected in reduced backbonding from the metal cation to the isocyanate ligand.     

Difluorophosphoryl Nitrene F2P(O)N: Matrix Isolation and Unexpected Rearrangement to F2PNO

Triplet difluorophosphoryl nitrene F₂P(O)N (X³A′′) was generated on ArF excimer laser irradiation (λ=193 nm) of F₂P(O)N₃ in solid argon matrix at 16 K, and characterized by its matrix IR, UV/Vis, and EPR spectra, in combination with DFT and CBS‐QB3 calculations. On visible light irradiation (λ>420 nm) at 16 K F₂P(O)N reacts with molecular nitrogen and some of the azide is regenerated. UV irradiation (λ=255 nm) of F₂P(O)N (X³A′′) induced a Curtius‐type rearrangement, but instead of a 1,3‐fluorine shift, nitrogen migration to give F₂PON is proposed to be the first step of the photoisomerization of F₂P(O)N into F₂PNO (difluoronitrosophosphine). Formation of novel F₂PNO was confirmed with ¹⁵N‐ and ¹⁸O‐enriched isotopomers by IR spectroscopy and DFT calculations. Theoretical calculations predict a rather long P? N bond of 1.922 Å [B3LYP/6‐311+G(3df)] and low bond‐dissociation energy of 76.3 kJ mol^?1 (CBS‐QB3) for F₂PNO.     

Interactions of Pyridine-Based Organic Cations as Structure-Determining Factors in Perovskite-Related Compounds AxPb(II)yBrz

We have synthesised and characterised 21 new ternary Pb(II) bromides with 16 different pyridine-based organic cations by single crystal XRD measurements. The dominating composition is APbBr₃ with 10 representatives, but also 6 examples for APb₂Br₅ were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N−H⋅⋅⋅Br hydrogen bridges on the connectivity and bonding situation of the Pb−Br polyhedra. Additionally, it turned out, that further weak ionic interactions can have an influence, if the formation of N−H⋅⋅⋅Br hydrogen bridges is hindered by steric effects. In general, the high versatility of the dominating PbBr₆ octahedra, and in some cases higher or lower coordination numbers, allows conclusions on the parameters that influence pattern and extent of the N−H⋅⋅⋅Br bridges as the strongest structure-determining factor. Type and extent of N−H⋅⋅⋅Br bridges have also an impact on the distortion of the PbBr₆ octahedra ranging from nearly regular PbBr₆ octahedra to 2+2+2 and 1+2+2+1 patterns with significant lone pair activity. Finally, the connectivity mode of the octahedra relates to formation and strength of hydrogen bonds.     

Reactions of a Ga/P‐Based Frustrated Lewis Pair with HX (X = F – I), Heterocumulenes R–NCY (Y = O,S) and Chalcogens–Adduct Formation and Surprising Stability towards Protolysis

Treatment of the geminal Ga/P‐based frustrated Lewis pair (FLP) Mes₂P–C(GatBu₂)=C(H)–Ph ( 1 ) with HX (X = F, Cl, Br, I) afforded the corresponding adducts 2 with the protons bound to the P and the halide anions coordinated to the Ga atoms. Short intramolecular contacts may indicate P–H ··· X hydrogen bonding interactions. The Br and I compounds ( 2c , 2d ) were accessible in moderate yields even when aqueous solutions of the acids were employed. These unexpected reactions confirm the surprising stability of FLP 1 towards protolysis. Heterocumulenes R–N=C=Y (Y = O, S) and 1 yielded adducts with two different structural motifs. The N=C=Y groups were coordinated to the FLP either via the C=Y (Y = S; Ph–N=C=O) or the C=N bonds (Ph–N=C=O, Et–N=C=O). For phenyl isocyanate the C=O bonded isomer was observed in the solid state, while both isomeric forms were detected in solution. Steric shielding and the hardness of the atoms may influence the formation of the respective isomer. Cleavage of the C=S bonds of isothiocyanates was observed for the first time and afforded a sulfur adduct 9a , in which an S atom (electron sextet) was bound to the lone pair of electrons at phosphorus and to the Lewis acidic Ga atom. Four‐membered PCGaY heterocycles resulted, which were also synthesized in high yields by the direct reaction of 1 with propylene sulfide or selenium.     

Hypervalent Organoselenium(II) Compounds with Organophosphorus Ligands. Crystal and Molecular Structure of [2‐(iPr2NCH2)C6H4]Se[S2PR′2] (R′ = Ph,OiPr)

Redistribution reactions between diorganodiselenides of type [2‐(R₂NCH₂)C₆H₄]₂Se₂ [R = Et, iPr] and bis(diorganophosphinothioyl disulfanes of type [R′₂P(S)S]₂ (R = Ph, OiPr) resulted in the hypervalent [2‐(R₂NCH₂)C₆H₄]SeSP(S)R′₂ [R = Et, R′ = Ph ( 1 ), OiPr ( 2 ); R = iPr, R′ = Ph ( 3 ), OiPr ( 4 )] species. All new compounds were characterized by solution multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P, ⁷⁷Se) and the solid compounds 1 , 3 , and 4 also by FT‐IR spectroscopy. The crystal and molecular structures of 3 and 4 were determined by single‐crystal X‐ray diffraction. In both compounds the N(1) atom is intramolecularly coordinated to the selenium atom, resulting in T‐shaped coordination arrangements of type (C,N)SeS. The dithio organophosphorus ligands act monodentate in both complexes, which can be described as essentially monomeric species. Weak intermolecular S ··· H contacts could be considered in the crystal of 3 , thus resulting in polymeric zig‐zag chains of R and S isomers, respectively.     

Crystal Structure and Dimorphism of Silicon Tetraisocyanate Si(NCO)4

Silicon tetraisocyanate Si(NCO)₄ was obtained by reacting SiCl₄ and AgNCO in boiling toluene. The colourless liquid was analyzed by Raman and NMR spectroscopy. Structural studies on solid Si(NCO)₄ (melting point: +26 °C) have revealed it to exist in two polymorphic modifications. According to the results of single‐crystal X‐ray diffraction, at T = –173 °C, α‐Si(NCO)₄ exhibits triclinic symmetry (P$\bar{1}$ ; a = 10.05(5), b = 10.50(2), c = 14.32(1) Å, α = 91.62(1)°, β = 92, 32(1)°, γ = 99.68(1)°; V = 1488.56(3) ų; Z = 8). Above T = –33 °C, a monoclinic phase evolves, β‐Si(NCO)₄ (P2₁/c; a = 10.78(3), b = 7.11(1), c = 10.27(5) Å, β = 99, 06(9)°; V = 777.39(1) ų; Z = 4). The charge distribution was studied for both polymorphs. In the solid state, Si(NCO)₄ is a tetrahedral molecule with the Si–N=C=O linkages bent at the nitrogen atoms.     

Modulation of Metallophilic and π–π Interactions in Platinum Cyclometalated Luminophores with Halogen Bonding

Luminescent cyclometalated complexes [M(C^N^N)CN] (M=Pt, Pd; HC^N^N=pyridinyl- (M=Pt 1 , Pd 5 ), benzyltriazolyl- (M=Pt 2 ), indazolyl- (M=Pt 3 , Pd 6 ), pyrazolyl-phenylpyridine (M=Pt 4 )) decorated with cyanide ligand, have been explored as nucleophilic building blocks for the construction of halogen-bonded (XB) adducts using IC₆F₅ as an XB donor. The negative electrostatic potential of the CN group afforded CN⋅⋅⋅I noncovalent interactions for platinum complexes 1 – 3 ; the energies of XB contacts are comparable to those of metallophilic bonding according to QTAIM analysis. Embedding the chromophore units into XB adducts 1 – 3 ⋅⋅⋅IC₆F₅ has little effect on the charge distribution, but strongly affects Pt⋅⋅⋅Pt bonding and π-stacking, which lead to excited states of MMLCT (metal–metal-to-ligand charge transfer) origin. The energies of these states and the photoemissive properties of the crystalline materials are primarily determined by the degree of aggregation of the luminophores via metal–metal interactions. The adduct formation depends on the nature of the metal and the structure of the metalated ligand, the variation of which can yield dynamic XB-supported systems, exemplified by thermally regulated transition 3 ↔ 3 ⋅⋅⋅IC₆F₅.     

Vibro-conformational behaviour and normal coordinate analysis of fluorocarbonyl isocyanate,FC(O)NCO

Vibrational data of vapour, liquid and matrix-isolated fluorocarbonyl isocyanate, FC(O)NCO, were investigated. A subsequent normal coordinate analysis was performed for the A′ species of the predominant planar cis conformer (CO double bond cis with respect to the vicinal NC double bond). The following internal force constants were derived: f_CO= 12.88 mdyn Å⁻¹, f_CF=6.20 mdyn Å⁻¹ and F_CN= 4.42 mdyn Å⁻¹.     

A Dinuclear Uranium Complex [{UO2F2(NH3)}2(μ-F)2]2− from Reaction of TlF and UO2F2 in Liquid Anhydrous Ammonia and Fluoride Ion Affinities for Some Uranyl(VI) Species [UO2Fx]2−x and [UO2Fx(NH3)5−x]2−x

UO₂F₂ abstracts F⁻ anions from TlF in liquid ammonia solution and the compound [Tl₂(NH₃)₆][{UO₂F₂(NH₃)}₂(μ-F)₂] is formed. The compound has been characterized by single crystal X-ray diffraction, Raman spectroscopy and quantum-chemical calculations for the solid state. Quantum-chemical investigation of the [{UO₂F₂(NH₃)}₂(μ-F)₂]²⁻ anion showed that the U−(μ-F)−U σ-3c-4e-bond is essentially ionic. The [Tl₂(NH₃)₆]²⁺ cation shows a thallophilic Tl⋅⋅⋅Tl interaction. Fluoride ion affinities (FIAs) were calculated for different UO₂²⁺ species [UO₂F_x]^2−x and [UO₂F_x(NH₃)_5−x]^2−x with x=0 to 4.     

Grafting onto carbon black by the reaction of reactive carbon black having masked isocyanate or acyl azide group with functional polymers

Although isocyanate group (NCO) introduced onto carbon black surface was inactivated rapidly upon storage, it could be stabilized by masking the NCO group with active hydrogen compounds such as acetylacetone, diethyl malonate, and sodium hydrogensulfite. Upon heating these carbon blacks having masked NCO group at 150°C, the NCO group was regenerated on carbon black by the decomposition of the masked NCO group. On the other hand, acyl azide (CON₃) group introduced onto carbon black was stable at below 20°C, but readily decomposed to NCO group by heating. By means of the reaction of NCO group on carbon black with functional polymers having hydroxyl, amino, and carboxyl group, these polymers were effectively grafted onto carbon black surface. When carbon black having CON₃ group was used as reactive carbon black, the grafting ratio of diol-type polyethylene glycol (M_n = 8.2 × 10³), polyethyleneimine (M_n = 2.0 × 10⁴), polyvinyl alcohol (M_n = 2.2 × 10⁴), and bifunctional carboxyl-terminated polystyrene (M_n = 1.1 × 10⁵) was determined to be 29.7, 81.7, 32.2, and 50.4%, respectively. The number of grafted polymer chain decreases with an increase in molecular weight of the polymers, because the shielding effect of NCO group by grafted polymer chain is enhanced with an increase in molecular weight of the polymer.     

Robust S4⋅⋅⋅O Supramolecular Synthons: Structures of Radical-Radical Cocrystals [p-XC6F4CNSSN]2[TEMPO] (X=F,Cl, Br,I, CN)

Cocrystallization of the dithiadiazolyl (DTDA) radicals p-XC₆F₄CNSSN (X=F, Cl, Br, I, CN) with TEMPO afforded the 2 : 1 cocrystals [p-XC₆F₄CNSSN]₂[TEMPO] ( 1 – 5 ) whose structures all reflect a common S₄⋅⋅⋅O supramolecular motif. The nature of this interaction was probed by DFT calculations (M06/aug-cc-pVDZ) on 1 which revealed that the enthalpy of formation of the [C₆F₅CNSSN]₂[TEMPO] supramolecular motif from [C₆F₅CNSSN]₂ and TEMPO is substantial (−54.0 kJ mol⁻¹). Electronic structure calculations revealed a TEMPO-based doublet S= configuration as the ground state with limited spin density on the DTDA rings (2.4 %). The corresponding spin quartet state is +78.9 kJ mol⁻¹ higher in energy. An atoms-in-molecules analysis reveals four bond critical points (BCPs) between the TEMPO O and the DTDA S atoms as well as additional BCPs between selected DTDA S atoms and methyl H atoms of the TEMPO molecule. Herein, the structures of 2 – 5 are considered within the context of a hierarchical view of competing and complementary intermolecular interactions; in particular, the established supramolecular CN⋅⋅⋅S−S synthon is sacrificed in order to form the new S₄⋅⋅⋅O interaction.     

Crystal Structure and Vibrational Spectra of ClSO2NHC(O)F

The reaction of chlorosulfonyl isocyanate (ClSO₂NCO) with anhydrous hydrogen fluoride (aHF) leads to the formation of ClSO₂NHC(O)F. The title compound with a melting point of –38 °C is characterized by vibrational spectroscopy and a single crystal structure analysis. It crystallizes in the tetragonal space group I4₁/a with 16 formula units per unit cell. a = 11.1115(2) Å, c = 16.5654(6) Å. The experimental data are supported by quantum‐chemical calculations on the PBE1PBE/6‐311G(3pd,3df) level of theory.