Search Results (8)

Heavier element analogues of a ketone, a C=O double-bond compound, have been fascinating compounds from the viewpoint of main-group element chemistry because of their unique structural features and reactivity as compared with those of a ketone, which plays an important role in organic chemistry. We will report here the synthesis of diorgano-stannanethione and stannaneselone featuring tin–chalcogen double bonds, which are the heavy-element analogues of a ketone. The newly obtained stannaneselone has been structurally characterized by spectroscopic analyses and single-crystal X-ray diffraction (SC-XRD) analysis, showing the short Sn–Se bond length featuring π-bond character. The obtained bis(ferrocenyl)stannanechalcogenones were found to undergo [2+4]cycloaddition reactions with 2,3-dimethyl-1,3-butadiene, affording the corresponding six-membered ring compound. Notably, thermolysis of the [2+4]cycloadduct of the stannaneselone regenerated the stannaneselone via the retro[2+4]cycloaddition, whereas the sulfur analogue was thermally very stable. Full article

An unusual series of germylenes and stannylenes stabilized by new tetradentate bis(amidine) ligands RNC(R′)N-linker-NC(R′)NR with a rigid naphthalene backbone has been prepared by protonolysis reaction of Lappert’s metallylenes [M(HMDS)₂] (M = Ge or Sn). Germylenes and stannylenes were fully characterized by NMR spectroscopy and X-ray diffraction analysis. DFT calculations have been performed to clarify the structural and electronic properties associated with tetradentate bis(amidine) ligands. Stannylene L₁Sn shows reactivity through oxidation, oxidative addition, and transmetalation reactions, affording the corresponding gallium and aluminum derivatives. Full article

The reactivity of the racemic N-heterocyclic stannylene [{MeHCN(^tBu)}Sn] (1) with the chalcogenide elements O₂, S, Se, and Te has been investigated. In the case of the reaction of 1 with molecular oxygen, the cyclic tristannoxane complex [{MeHCN(^tBu)}₂Sn(μ-O)]₃ (3) was isolated and characterised. NMR studies (¹H, ¹³C, and ¹¹⁹Sn) show the formation of D₃- and C₂- symmetric assemblies. The reaction of 1 with S, Se, and Te, respectively, yielded the cyclo-distannachalcogenide complexes, [{MeHCN(^tBu)}₂Sn(μ-E)]₃ (4: E = S, 5: E = Se, 6: E = Te), again with multinuclear NMR studies proving the formation of C₂- and C_s-symmetric assemblies. Single crystal X-ray diffraction studies have been used to elucidate the molecular structures of the products of oxidative addition, 3, 4, 5, and 6. Full article

A new series of tin(II) complexes (1, 2, 4, and 5) were successfully synthesized by employing hydroxy functionalized pyridine ligands, specifically 2-hydroxypyridine (hpH), 8-hydroxyquinoline (hqH), and 10-hydroxybenzo[h]quinoline (hbqH) as stabilizing ligands. Complexes [Sn(μ-κ²ON-OC₅H₄N)(N{SiMe₃}₂)]₂ (1) and [Sn₄(μ-κ²ON-OC₅H₄N)₆(κ¹O-OC₅H₄N)₂] (2) are the first structurally characterized examples of tin(II) oxypyridinato complexes exhibiting {Sn₂(OCN)₂} heterocyclic cores. As part of our study, ¹H DOSY NMR experiments were undertaken using an external calibration curve (ECC) approach, with temperature-independent normalized diffusion coefficients, to determine the nature of oligomerisation of 2 in solution. An experimentally determined diffusion coefficient (298 K) of 6.87 × 10⁻¹⁰ m² s⁻¹ corresponds to a hydrodynamic radius of Ca. 4.95 Å. This is consistent with the observation of an averaged hydrodynamic radii and equilibria between dimeric [Sn{hp}₂]₂ and tetrameric [Sn{hp}₂]₄ species at 298 K. Testing this hypothesis, ¹H DOSY NMR experiments were undertaken at regular intervals between 298 K–348 K and show a clear change in the calculated hydrodynamic radii form 4.95 Å (298 K) to 4.35 Å (348 K) consistent with a tetramer ⇄ dimer equilibria which lies towards the dimeric species at higher temperatures. Using these data, thermodynamic parameters for the equilibrium (ΔH° = 70.4 (±9.22) kJ mol⁻¹, ΔS° = 259 (±29.5) J K⁻¹ mol⁻¹ and ΔG°₂₉₈ = −6.97 (±12.7) kJ mol⁻¹) were calculated. In the course of our studies, the Sn(II) oxo cluster, [Sn₆(m³-O)₆(OR)₄:{Sn^(II)(OR)₂}₂] (3) (R = C₅H₄N) was serendipitously isolated, and its molecular structure was determined by single-crystal X-ray diffraction analysis. However, attempts to characterise the complex by multinuclear NMR spectroscopy were thwarted by solubility issues, and attempts to synthesise 3 on a larger scale were unsuccessful. In contrast to the oligomeric structures observed for 1 and 2, single-crystal X-ray diffraction studies unambiguously establish the monomeric 4-coordinate solid-state structures of [Sn(κ²ON-OC₉H₆N)₂)] (4) and [Sn(κ²ON-OC₁₃H₈N)₂)] (5). Full article

Starting out from dipotassium 1,5-oligosiloxanylene diide 2, a 3,7,10-trioxa-octasilabicyclo[3.3.3]undecane was prepared, which represents the third known example of this cage structure type. Reaction of 1,3-dichlorotetramethyldisiloxane with 1,1’-bis[bis(trimethylsilyl)potassiosilyl]ferrocene gave a ferrocenophane with a disiloxane containg bridge. The compound can be further derivatized by conversion into a 1,5-oligosilanyl diide. Reacting 1,5-oligosiloxanylene diide 2 with SnCl₂ or GeCl₂·dioxane in the presence of PMe₃ gave cyclic disilylated tetrylene PMe₃ adducts. Release of the base-free stannylene led to a dimerization process which gave a bicyclic distannene as the final product. Abstraction of the PMe₃ from the cyclic disilylated germylene PMe₃ adduct with B(C₆F₅)₃ caused oxidative addition of the germylene into a para-C-F bond of Me₃P·B(C₆F₅)₃. Full article

Syntheses of heavier Group 14 analogues of “Arduengo-type” N-heterocyclic carbene majorly involved the use of conventional alkali metal-based reducing agents under harsh reaction conditions. The accompanied reductant-derived metal salts and chances of over-reduced impurities often led to isolation difficulties in this multi-step process. In order to overcome these shortcomings, we have used 1,4-bis-(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene as a milder reducing agent for the preparation of N-heterocyclic germylenes (NHGe) and stannylenes (NHSn). The reaction occurs in a single step with moderate yields from the mixture of N-substituted 1,4-diaza-1,3-butadiene, E(II) (E(II) = GeCl₂·dioxane, SnCl₂) and the organosilicon reductant. The volatile byproducts trimethylsilyl chloride and pyrazine could be removed readily under vacuum. No significant over reduction was observed in this process. However, N-heterocyclic silylene (NHSi) could not be synthesized using an even stronger organosilicon reductant under thermal and photochemical conditions. Full article

Molecules containing catenated heavy group 14 atoms are known to exhibit the interesting property of σ-bond electron delocalization. While this is well studied for oligo- and polysilanes the current paper addresses the UV-absorption properties of small tin containing oligosilanes in order to evaluate the effects of Sn–Si and Sn–Sn bonds as well as the results of substituent exchange from methyl to phenyl groups. The new stannasilanes were compared to previously investigated oligosilanes of equal chain lengths and substituent pattern. Replacing the central SiMe₂ group in a pentasilane by a SnMe₂ unit caused a bathochromic shift of the low-energy band (λ_max = 260 nm) of 14 nm in the UV spectrum. If, instead of a SnMe_2, a SnPh₂ unit is incorporated, the bathochromic shift of 33 nm is substantially larger. Keeping the SnMe₂ unit and replacing the two central silicon with tin atoms causes shift of the respective band (λ = 286 nm) some 26 nm to the red. A similar approach for hexasilanes where the model oligosilane [(Me₃Si)₃Si]₂(SiMe₂)₂ (λ_max = 253 nm) was modified in a way that the central tetramethyldisilanylene unit was exchanged for a tetraphenyldistannanylene caused a 50 nm bathochromic shift to a low-energy band with λ_max = 303 nm. Full article

The regioselective C-2-O-acrylation and metacrylation of methyl 4,6-O-benzylidene-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-galactopyranosidethrough their corresponding organotin intermediates have been studied. Regioselectivitywas achived through the formation of a tin chelate of the 2,3-diols. Thus, methyl 4,6-O-benzylidene-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-galactopyranosidewere reacted with dibutylstannylene to give the corresponding dibutylstannylene acetalintermediates that were then reacted in a regioselective manner with acryloyl chloride ormetacryloyl chloride in the presence of triethylamine (TEA) or pyridine to give thevinylic type monomeric compounds. The monomeric products containing glucose andgalactose units from each reaction were separated by column chromatography using agradient of n-hexane and ethyl acetate as eluant. The structure of the obtained compoundswere confirmed using ¹H-, ¹³C- and 2D NMR spectroscopy. Full article