Double Bond Cleavage in Small Molecules Using a Geminal Sc/P Lewis Pair

Frustrated Lewis pairs (FLPs) have proven capable of cleaving the H-H σ-bond and binding a variety of unsaturated small molecules. In contrast, examples of FLP-mediated complete rupture of double-bonded substrates remain scarce. Herein, we present a geminal Sc/P Lewis pair, i.e., (ArO)2ScN(tBu)PPh2 (Ar = 2,6-tBu2-C6H3), that exhibits typical FLP-type 1,2-addition reactivity toward CO2. Notably, it enables the complete cleavage of a series of double bonds, such as the N═N bond in azobenzene or pyridazine, the N═O bond in nitrosobenzene, and the N═S and S═O bonds in N-sulfinylaniline, to yield the corresponding metallacyclic products. Moreover, the first rare-earth metal sulfur monoxide adduct could be obtained through the bond cleavage of PhNSO, demonstrating the capability of rare-earth metal complexes to capture reactive species.

A sulfur monoxide complex of platinum fluoride with a positively charged ligand

A sulfur monoxide complex of platinum fluoride in the form of PtF₂(η¹-SO) was generated via the isomerization of a molecular complex Pt(SOF₂) in cryogenic matrixes under UV-vis irradiation. The infrared absorptions observed at 1205.4, 619.8 and 594.9 cm^-1 are assigned to the S-O, antisymmetric and symmetric F-Pt-F stretching vibrations of the PtF₂(η¹-SO) complex, which possesses nonplanar C_s symmetry with a singlet ground state according to density functional theory calculations. The experimental vibrational frequency and computed distance (1.449 Å) of the SO ligand indicate that the SO ligand features a positively charged character, which is further confirmed by natural bond orbital analysis and Mayer bond order. Such character is completely different from that for early transition metal-SO complexes and dioxygen complexes of platinum. Formation of the PtF₂(η¹-SO) complex was found to occur via the consecutive transfer of the two fluorine atoms from SOF₂ to Pt in the sulfur bound Pt(SOF₂) complex, which involves a series of intermediates on the basis of the mechanism study at the B3LYP level. Although the whole process is hindered by the large energy barrier encountered during the transfer of the first fluorine atom, UV-vis irradiation can provide sufficient energy to surmount this barrier and facilitates the formation of the nonplanar PtF₂(η¹-SO) complex stabilized in matrix.

3-Methyl-1-phenyl-4-thioacetylpyrazol-5-one

The novel compound 3-methyl-1-phenyl-4-thioacetylpyrazol-5-one is obtained in excellent yield via a thionation of the corresponding oxygen analogue. The product is isolated in pure form using column chromatography and is characterised using 1D and 2D NMR experiments, ATR IR and HRMS spectra, and single-crystal XRD.

Thermochemistry and mechanisms of the Pt+ + SO2 reaction from guided ion beam tandem mass spectrometry and theory

The kinetic energy dependences of the reactions of Pt⁺ (²D_5/2) with SO₂ were studied using a guided ion beam tandem mass spectrometer and theory. The observed cationic products are PtO⁺ and PtSO⁺, with small amounts of PtS⁺, all formed in endothermic reactions. Modeling the kinetic energy dependent product cross sections allows determination of the product bond dissociation energies (BDEs): D₀(Pt⁺-O) = 3.14 ± 0.11 eV, D₀(Pt⁺-S) = 3.68 ± 0.31 eV, and D₀(Pt⁺-SO) = 3.03 ± 0.12 eV. The oxide BDE agrees well with more precise literature values, whereas the latter two results are the first such measurements. Quantum mechanical calculations were performed for PtO⁺, PtS⁺, PtO₂ ⁺, and PtSO⁺ at the B3LYP and coupled-cluster with single, double, and perturbative triple [CCSD(T)] levels of theory using the def2-XZVPPD (X = T, Q) and aug-cc-pVXZ (X = T, Q, 5) basis sets and complete basis set extrapolations. These theoretical BDEs agree well with the experimental values. After including empirical spin-orbit corrections, the product ground states are determined as PtO⁺ (⁴Σ_3/2), PtS⁺ (⁴Σ_3/2), PtO₂ ⁺ (²Σ_g ⁺), and PtSO⁺ (²A'). Potential energy profiles including intermediates and transition states for each reaction were also calculated at the B3LYP/def2-TZVPPD level. Periodic trends in the thermochemistry of the group 9 metal chalcogenide cations are compared, and the formation of PtO⁺ from the Pt⁺ + SO₂ reaction is compared with those from the Pt⁺ + O₂, CO₂, CO, and NO reactions.

Exploring the reactivity of homoleptic organozincs towards SO2: Synthesis and structure of a homologous series of organozinc sulfinates

Studies on the reactivity of zinc alkyl compounds towards SO2 are relatively less explored than either the oxygenation or hydrolysis reactions. We report on environmentally friendly and efficient syntheses of...

Experiment and Theory Clarify: Sc+ Receives One Oxygen Atom from SO2 to Form ScO+, which Proves to be a Catalyst for the Hidden Oxygen-Exchange with SO2

Using Fourier‐transform ion cyclotron resonance mass spectrometry, it was experimentally determined that Sc⁺ in the highly diluted gas phase reacts with SO₂ to form ScO⁺ and SO. By ¹⁸O labeling, ScO⁺ was shown to play the role of a catalyst when further reacting with SO₂ in a Mars‐van Krevelen‐like (MvK) oxygen exchange process, where a solid catalyst actively reacts with the substrate but emerges apparently unchanged at the end of the cycle. High‐level quantum chemical calculations confirmed that the multi‐step process to form ScO⁺ and SO is exoergic and that all intermediates and transition states in between are located energetically below the entrance level. The reaction starts from the triplet surface; although three spin‐crossing points with minimal energy have been identified by computational means, there is no evidence that a two‐state scenario is involved in the course of the reaction, by which the reactants could switch from the triplet to the singlet surface and back. Pivotal to the oxygen exchange reaction of ScO⁺ with SO₂ is the occurrence of a highly symmetric four‐membered cyclic intermediate by which two oxygen atoms become equivalent.

Functionalized NU-1000 with an Iridium Organometallic Fragment: SO2 Capture Enhancement

A new material, MOF-type [Ir]@NU-1000, was accessed from the incorporation of the iridium organometallic fragment [Ir{κ³(P,Si,Si)PhP(o-C₆H₄CH₂SiⁱPr₂)₂}] into NU-1000. The new material incorporates less than 1 wt % of Ir(III) (molar ratio Ir to NU-1000, 1:11), but the heat of adsorption for SO₂ is significantly enhanced with respect to that of NU-1000. Being a highly promising adsorbent for SO₂ capture, [Ir]@NU-1000 combines exceptional SO₂ uptake at room temperature and outstanding cyclability. Additionally, it is stable and can be regenerated after SO₂ desorption at low temperature.

Diferrocenyl Thioketone: Reactions with (Bisphosphane)Pt(0) Complexes-Electrochemical and Computational Studies

Diferrocenyl thioketone reacts smoothly with (bisphosphane)Pt(0) complexes in toluene solution at room temperature yielding 1:1 adducts identified as ferrocenyl (Fc) functionalized platinathiiranes. Their structures were unambiguously confirmed by means of spectroscopic methods as well as by X-ray diffraction analysis. A unique, ferrocene-rich platinathiirane, bearing three Fc-units, was prepared starting with [bis(diphenylphosphino)ferrocene] Pt(0(η²-norbornene). For comparison, a similar platinathiirane with one Fc-unit was obtained from the reaction of the latter complex with thiobenzophenone. Quantum-chemical calculations were carried out to describe the bonding pattern and frontier molecular orbitals of the ferrocene-rich platinathiirane complexes. These calculations confirmed that the C=S bond loses its formally double-bond character upon complexation (bisphosphane)Pt(0). Cyclic voltammetry measurements were performed to characterize the obtained platinathiiranes in CH₂Cl₂ solutions. For comparison, the cyclic voltammogram for diferrocenyl thioketoneas a mixed-valent (Fe^II-Fe^III) compound was also recorded and analyzed. The results point out to a diffusion controlled electrode process in case of differocenyl thioketone and mixed diffusion and adsorption controlled electrode process in the case of the studied platinathiiranes.

The non-covalently bound SOH2O system, including an interpretation of the differences between SOH2O and O2H2O

Despite the interest in sulfur monoxide (SO) among astrochemists, spectroscopists, inorganic chemists, and organic chemists, its interaction with water remains largely unexplored. We report the first high level theoretical geometries for the two minimum energy complexes formed by sulfur monoxide and water, and we report energies using basis sets as large as aug-cc-pV(Q+d)Z and correlation effects through perturbative quadruple excitations. One structure of SOH2O is hydrogen bonded and the other chalcogen bonded. The hydrogen bonded complex has an electronic energy of -2.71 kcal mol-1 and a zero kelvin enthalpy of -1.67 kcal mol-1, while the chalcogen bonded complex has an electronic energy of -2.64 kcal mol-1 and a zero kelvin enthalpy of -2.00 kcal mol-1. We also report the transition state between the two structures, which lies below the SOH2O dissociation limit, with an electronic energy of -1.26 kcal mol-1 and an enthalpy of -0.81 kcal mol-1. These features are much sharper than for the isovalent complex of O2 and H2O, which only possesses one weakly bound minimum, so we further analyze the structures with open-shell SAPT0. We find that the interactions between O2 and H2O are uniformly weak, but the SOH2O complex surface is governed by the superior polarity and polarizability of SO, as well as the diffuse electron density provided by sulfur's extra valence shell.

Sulfur monoxide thermal release from an anthracene-based precursor, spectroscopic identification, and transfer reactivity

Sulfur monoxide (SO) is a highly reactive molecule and thus, eludes bulk isolation. We report here on synthesis and reactivity of a molecular precursor for SO generation, namely 7-sulfinylamino-7-azadibenzonorbornadiene (1). This compound has been shown to fragment readily driven by dinitrogen expulsion and anthracene formation on heating in the solid state and in solution, releasing SO at mild temperatures (<100 °C). The generated SO was detected in the gas phase by MS and rotational spectroscopy. In solution, 1 allows for SO transfer to organic molecules as well as transition metal complexes.

Isolation and Characterization of a Non-Rigid Hexamethylbenzene-SO2+ Complex

During our studies towards the preparation of the pentagonal-pyramidal hexamethylbenzene dication C₆ (CH₃ )₆²⁺ , we isolated the unprecedented dicationic species C₆ (CH₃ )₆ SO²⁺  (AsF₆^- )₂ from the reaction of hexamethylbenzene with a mixture of anhydrous HF, AsF₅ , and liquid SO₂ . This compound can be understood as a complex of unknown SO²⁺ with hexamethylbenzene. Herein, we report on its synthesis, molecular structure, and spectroscopic characterization.

Rational Synthesis of the Carbonyl(perthiolato)diiron [Fe2(S3CPh2)(CO)6] and Related Complexes

The photochemical reaction of Fe2(S2)(CO)6 and Ph2CS affords the perthiolate Fe2(S3CPh2)(CO)6 (1) in good yield. As confirmed crystallographically, 1 contains a previously elusive perthiolate ligand. The related reaction of Fe2(S2)(CO)5-(PPh3) and Ph2CS gave Fe2(S3CPh2)(CO)5(PPh3). Although Fe3S2(CO)9 and Ph2CS failed to efficiently give Fe2(S2CPh2)(CO)6, this compound could be prepared by desulfurization of 1 using PPh3.

SO₂--yet another two-faced ligand

Experimentally known adducts of SO2 with transition metal complexes have distinct geometries. In the present paper, we demonstrate by a bonding analysis that this is a direct consequence of sulfur dioxide acting as an acceptor in one set, square-planar complexes of d(8) and linear two-coordinated complexes of d(10) transition metals, and as a donor with other compounds, well-known paddle-wheel [Rh2(O2CCF3)4] and square-pyramidal [M(CO)5] (M = Cr, W) complexes. Bonding energy computations were augmented by the natural bond orbital (NBO) analysis and energy decomposition analysis (EDA). When the SO2 molecule acts as an acceptor, bonding in the bent coordination mode to the axial position of the d(8) or the d(10) metal center, the dominant contributor to the bonding is LAO(S) (Lewis Acidic Orbital, mainly composed of the px-orbital of the S atom) as an acceptor, while a dz(2) orbital centered on the metal is the corresponding donor. In contrast, the distinct collinear (or linear) coordination of the SO2 bound at the axial position of [Rh2(O2CCF3)4] and/or [M(CO)5] is associated with a dominant donation from a lone pair localized on the sulfur atom, σ*(Rh-Rh) and/or empty LAO(M) (mainly composed of the dz(2) orbital of the metal), respectively, acting as an acceptor orbital. The donor/acceptor capabilities of the SO2 molecule were also checked in adducts with organic Lewis acids (BH3, B(CF3)3) and Lewis bases (NH3, N(CH3)3, N-heterocyclic carbene).

Dithionite and sulfinate complexes from the reaction of SO2 with decamethylsamarocene

The reaction of [(η⁵-C₅Me₅)₂Sm(THF)₂] with SO₂ resulted in dithionite, sulfinate and mixed dithionite–sulfinate complexes.

Bond and small-molecule activation with low-valent nickel complexes

The use of nickel compounds in low oxidation states allowed a variety of useful transformations of interest for academia, industry and in the solution of environmental issues.