Silyliumylidene Ion Stabilized by Two σ-Donating Ni(0)- and Pd(0)-Fragments.

A silyliumylidene ion 2 stabilized by two σ-donating Ni(0)- and Pd(0)-fragments was successfully synthesized. Due to the σ-donation of M→Si interactions, 2 presents a pyramidalized cationic silicon center with a localized lone pair. The additional coordination of basic Pd(0) fragment to the mono-Ni(0)-stabilized silyliumylidene 1 results in a higher HOMO level and an unchanged HOMO-LUMO gap and thus, 2 remains highly reactive. Interestingly, the coordination mode at the Si center is closely related to the nature of M-ligands. Indeed, the donor/donor-stabilized silyliumylidene ion 2 has been transformed into a donor/acceptor-stabilized ion 13, featuring a trigonal planar Si center with a vacant orbital, just via a ligand exchange reaction from PCy3/NHC toward PMe3.

Caffeine Intoxication, in Which the Theophylline Level Served as an Indicator of the Treatment Course and the Caffeine Level Could Be Measured.

A 51-year-old man presented with sudden-onset palpitations and dyspnea that had started 8 h earlier. The patient was restless and tachypneic and had persistent vomiting upon arrival. His sensorium and oxygen saturation levels rapidly declined three hours after arrival, and he was placed on a ventilator. On hospitalization day 2, he was removed from the ventilator and claimed that he had consumed a large amount of energy drinks (oral caffeine intake, approximately 1 g). The theophylline level on arrival had been elevated (9.0 µg/mL). Caffeine intoxication should be considered in patients presenting with restlessness, tachypnea, frequent vomiting, lactic acidosis, and electrolyte abnormalities.

Syntheses of Iminophosphomamido Chlorogermylenes and Their Complexation with a Rhodium(I) Complex.

Three-coordinated chlorogermylenes of the type [Ph2 P(RN)2 ]GeCl (3: R=t Bu; 4: R=Dip=2,6-i Pr2 C6 H3 ), which bear an N,N-substituted iminophosphonamide ligand, were synthesized. The coordination behavior of 3 and 4 toward rhodium(I) complex was investigated. When 3 was treated with 1/2 of an equivalent of [RhCl(cod)]2 (cod=1,5-cyclooctadiene), the corresponding chlorogermylene-Rh(I) complex 5 was obtained as orange crystals. In contrast, the reaction of 4 with a half equivalent of [RhCl(cod)]2 under a CO atmosphere resulted in the formation of a five-membered germarhodacycle 7. Compounds 3, 4, 5, and 7 were characterized using NMR spectroscopies and single-crystal X-ray diffraction. Complex 5 can be employed as a catalyst for the hydrosilylation and hydroboration reactions of diphenylacetylene, thus demonstrating the utility of germylene ligands comparable to those of NHCs in the major transition metal catalytic processes.

Base-Stabilized Cationic Silyne with a π-Accepting Phosphonio Substituent.

A base-stabilized C-phosphonio-Si-amino-silyne 3 was synthesized, using an original method, through a coupling reaction between two Lewis-base-stabilized low-valent species: a silyliumylidene ion 1 and a P,S-bis-ylide 2 [C(0)-complex]. This new isolable cationic silyne 3 displays remarkably high stability at room temperature [t1/2 = 7 days in tetrahydrofuran (THF)] and a unique silyne reactivity thanks to the effect of phosphonio substituent.

Reversible Isomerization Between Silacyclopropyl Cation and Cyclic (Alkyl)(Amino)Silylene.

A phosphine-stabilized silacyclopropyl cation 2 has been synthesized and fully characterized. Of particular interest, 2 reversibly isomerizes into the corresponding seven-membered cyclic (alkyl)(amino)silylene 3 at room temperature via a formal migratory ethylene insertion into the Si-P bond. Although silylene 3 has not been spectroscopically detected, its transient formation has been evidenced by the isolation of the corresponding disilene dimer 5 as well as by trapping reactions.

Labile Base-Stabilized Silyliumylidene Ions. Non-Metallic Species Capable of Activating Multiple Small Molecules.

Several base-stabilized silyliumylidene ions (2 and 3) with different ligands were synthesized. Their behaviour appeared strongly dependent on the nature of ligand. Indeed, in contrast to the poorly reactive silyliumylidene ions 3 c,d stabilized by strongly donating ligands (DMAP, NHC), the silylene- and sulfide-supported one (2-H and 3 a) exhibits higher reactivity toward various small molecules. Furthermore, their capability to successively activate multiple small molecules was clearly demonstrated by processes involving successive reactions with silane/formamide, CO2 and H2 . Moreover, HBPin adduct of 3 a (8-C) catalyzes the hydroboration of pyridine. Of particular interest, silylene-supported silyliumylidene complex 2-H is one of the rare species able to activate two H2 molecules.

Lewis Base Adducts of Phosphine-Stabilized Pb(II) Cations: Synthesis and Catalytic Hydroamination of Alkynes.

Phosphine-stabilized Pb(II) cations, generated by chloride abstraction from chloroplumbylene 1, readily react with Lewis bases (L) such as phosphines and amines to give the corresponding donor-acceptor complexes 3. These complexes 3 react with phenylacetlylene via alkyne insertion into the Pb-L bond to afford the corresponding vinylplumbylenes 4. Of particular interest, the stable complex 4-HNiPr2 (with a secondary amine) can be used as a hydroamination catalyst of phenylacetylene.

Iminophosphonamido-Supported Plumbylenes and Plumbyliumylidenes: Synthesis and Properties.

A series of low-valent lead(II) species, i.e., plumbylenes and plumbyliumylidenes supported by an N,N'-di-tert-butyliminophosphonamide ligand, have been synthesized. Chloroplumbylene [Ph2P(NtBu)2PbCl] (1) was readily prepared by the reaction of the corresponding lithium iminophosphonamide and PbCl2 in THF. The substitution reaction of 1 with KN(SiMe3)2 in THF afforded the corresponding aminoplumbylene [Ph2P(NtBu)2PbN(SiMe3)2] (2) in the form of colorless crystals. The structures of these plumbylenes in the solid state and in solution were exhaustively characterized using multinuclear NMR spectroscopy and X-ray diffraction analysis. In the crystalline state, 1 adopts a nearly linear polymeric structure in the direction of the c axis via Pb-Cl bonds, with alternating four-membered PbN2P rings. The chloride-abstraction reaction of 1 using Na[B(C6F5)4] in fluorobenzene proceeded efficiently at ambient temperature to furnish plumbyliumylidene [Ph2P(NtBu)2Pb:]+ (3+), which was isolated as the air-sensitive yellow borate salt 3[B(C6F5)4]. Plumbyliumylidene 3[B(C6F5)4] acts as a Lewis acid catalyst for the hydroboration of benzophenone and benzaldehyde at catalyst loadings of as low as 0.1 mol % under ambient conditions. Furthermore, the details of the reaction mechanism are discussed on the basis of the results of DFT calculations.

Synthesis, Characterization and Reactivity of a σ-Donating Ni0 -Stabilized Silyliumylidene Ion.

The synthesis of a silyliumylidene cation complex 2 stabilized by a Ni0 -based donating ligand is reported. Experimental and theoretical studies demonstrate that the highly electrophilic SiII center is stabilized by a dative Ni→Si σ-interaction and π-donations from the amino- and Ni-moieties. Due to the energetically close frontier orbitals localized on the Si and Ni atoms, complex 2 presents a competitive reactivity at Si and Ni sites.

Halogen-Exchange Reactions of Iminophosphonamido-Chlorosilylenes with Alkali Halides: Convenient Synthesis of Heavier Halosilylenes.

Halogen-substituted silylenes are an important building block for synthesizing silicon-based low-valent and multiple-bond species. However, the number of reports on heavier halosilylenes that contain bromine and iodine is still limited. Here, we present a convenient synthesis for bromo- and iodosilylenes supported by an iminophosphonamide ligand. The heavier halosilylenes [Ph2P(tBuN)2]SiX (2: X = Br, 3: X = I) were successfully synthesized via the halogen-exchange reaction of chlorosilylene 1 with alkali halides in THF. As a demonstration of the reactivity of 2 and 3, oxidative addition reactions of 2 and 3 with elemental selenium in C6D6 afforded the corresponding bromo- (5) or iodosilylene-selone (6) as colorless crystals. The molecular structures of 2, 3, 5, and 6 were fully characterized by spectroscopic means and single-crystal X-ray diffraction analysis. Furthermore, the effects of the halogen atom on the electronic state of halosilylenes 1-3 and halosilylene-selones 4-6 were investigated using density functional theory (DFT) calculations.

Hydroboration of carbonyls and imines by an iminophosphonamido tin(II) precatalyst.

A novel three-coordinated tin(II) chloride [Ph2P(NtBu)2]SnCl (1) supported by an N,N'-di-tert-butyliminophosphonamide having two phenyl groups on the phosphorus atom was synthesized by the reaction of the starting lithium iminophosphonamide [Ph2P(NtBu)2]Li with SnCl2·(dioxane) in toluene. The molecular structure of 1 was established by X-ray diffraction analysis. Tin(II) chloride 1 can act as an efficient precatalyst for the hydroboration of a wide variety of aldehydes, ketones, and imines at -10 °C. DFT calculations propose that hydroboration involves hydride transfer from the corresponding tin(II) hydride intermediate [Ph2P(NtBu)2]SnH (10) to the carbonyl substrates via four-membered transition states (TS-12), affording three-coordinated tin(II) alkoxide intermediates [Ph2P(NtBu)2]SnOR (13), followed by the stepwise reaction of 13 with HBpin (pin = pinacolate) to release the boronate esters and regenerate the tin(II) hydride 10. The stoichiometric reaction of the in site-generated 10 with benzophenone 2a at -10 °C led to the formation of 13. Moreover, 13 also stoichiometrically reacted with HBpin at -10 °C, forming the corresponding boronate ester 3a and 10 based on the 1H NMR spectrum of the reaction mixture.

Strained and Reactive Donor/Acceptor-Supported Metallasilanone.

A novel stable donor/acceptor-supported MnI -metallasilanone 3 was synthesized. The intramolecular silanone-MnI interaction induces a highly strained three-membered cyclic structure, leading to an exceptionally high reactivity of 3 as a donor/acceptor complex of silanone. Indeed, metallasilanone 3 readily reacts with various small molecules such as H2 or ethylene gas in mild conditions.

Formation of silaimines from a sterically demanding iminophosphonamido chlorosilylene via intramolecular N-P bond cleavage.

The sterically demanding iminophosphonamido chlorosilylene [Ph2P(DipN)2]SiCl (Dip = 2,6-diisopropylphenyl) was synthesized and fully characterized using NMR spectroscopy and X-ray crystallography. Substitution reactions of [Ph2P(DipN)2]SiCl with N- and Fe-nucleophiles led to the unexpected formation of the corresponding silaimine derivatives. This process involves the ring-opening rearrangement of three-coordinated silylene intermediates that proceeds via intramolecular N-P bond cleavage.

Interconversion between a silaimine and an aminosilylene supported by an iminophosphonamide ligand.

The reaction of a chlorosilylene, supported by an iminophosphonamide ligand, with KN(SiMe3)2 resulted in the formation of a silaimine instead of the expected aminosilylene. However, this silaimine exists in equilibrium with the corresponding aminosilylene, which was experimentally demonstrated using variable-temperature NMR spectroscopy and a trapping reaction with elemental selenium to give a silaselenourea.

An Iminophosphonamido-Chlorosilylene as a Strong σ-Donating NHSi Ligand: Synthesis and Coordination Chemistry.

The N-heterocyclic silylene (NHSi) [Ph2 P(t BuN)2 ]SiCl (1), supported by an iminophosphonamide ligand, was obtained from the dehydrochlorination of [Ph2 P(t BuN)2 ]SiHCl2 (2) with LiN(SiMe3 )2 . NHSi 1 contains an extremely high-energy HOMO level and consequently displays unique coordination behavior toward RhI complexes. When 1 was treated with 1/4 of an equivalent of [RhCl(cod)]2 (cod=1,5-cyclooctadiene), the 14-electron Y-shaped bis(chlorosilylene) RhI complex 5 was obtained as dark purple crystals. The reaction of 1 with 1/6 of an equivalent of [RhCl(cod)]2 yielded the cationic tris(silylene)-RhI complex [6]+ ⋅Cl- as red crystals, wherein a two-coordinated silylene ligand engages in a Si=Rh double bond. A structural analysis of 5 and [6]+ ⋅Cl- revealed that the central rhodium atoms adopt trigonal and square-planar coordination geometries, respectively, with considerably shortened Si-Rh bonds [5: 2.1605(5) Å; [6]+ : 2.133(1) Å].

Synthesis of a Stable N-Hetero-RhI -Metallacyclic Silanone.

A novel N-hetero-RhI -metallacyclic silanone 2 has been synthesized. The silanone 2, showing an extremely large dimerization energy (ΔG=+86.2 kcal mol-1 ), displays considerable stability and persists in solution up to 60 °C. Above 120 °C, an intramolecular Csp3 -H insertion occurs slowly over a period of two weeks leading to the bicyclic silanol 5. The exceptional stability of 2, related to the unusual electronic and steric effects of RhI -substituent, should allow for a more profound study and understanding of these new species. Furthermore, the metallacyclic silanone 2 presents two reactive centers (Si=O and Rh), which can be involved depending upon the nature of reagents. Of particular interest, the reaction with H2 starts with the hydrogenation of RhI center leading to the corresponding RhIII -dihydride complex 7 and it undergoes a cis/trans-isomerization via a particular mechanism, demonstrating that addition-elimination processes can also happen for silanones just like for their carbon analogues!

A Stable N-Hetero-Rh-Metallacyclic Silylene.

A cyclic (amino)metal-substituted dicoordinated silylene derivative has been synthesized and fully characterized. Of particular interest is that the N-hetero-RhI -metallacyclic silylene exhibits a distorted tetrahedral geometry around the rhodium atom and a considerably shortened Si-Rh bond (2.138 Å) compared to classical Si-Rh single bonds (ca. 2.30-2.35 Å). A theoretical investigation reveals that the geometrical deviation around the rhodium center from the classical square-planar to a tetrahedral geometry increases the π-donating and σ-accepting character of the rhodium atom, thereby efficiently stabilizing the silylene moiety.

[Hemobilia caused by hepatic artery pseudoaneurysm after endoscopic biliary stenting for malignant hilar biliary strictures:a case report].

A 78-year-old female presented at our hospital with hilar biliary strictures caused by gallbladder cancer. Metal stents with a dilated diameter of 8mm were placed in a side-by-side fashion in the left and right hepatic ducts. However, 3 months after stenting, the patient experienced a sudden onset of hematemesis. Emergent enhanced abdominal angiography revealed a right hepatic arterial pseudoaneurysm that had likely ruptured, thus causing the hemobilia. Probable association of biliary stents with pseudoaneurysm was also demonstrated. Selective angiography revealed bleeding from the pseudoaneurysm into the biliary stents, which was controlled by coil embolization. The patient was subsequently discharged on hospital day 15.

Mechano-synthesized orange TiO2 shows significant photocatalysis under visible light.

Nitrogen and carbon co-doped TiO2 particles with a brilliant yellow-orange color were produced mechanochemically by high-energy ball milling as one-pot synthesis. This facile synthesis required only grinding TiO2 with melamine at room temperature. Using monochoromatic lights with the same intensity in visible and UV, the photocatalytic activity of the TiO2 particles was accurately evaluated with respect to the degradation of an aqueous dye (methylene blue) solution. The activities under visible light (450 and 500 nm) were, respectively, 4 and 2 times higher than that of the unmilled TiO2 under UV light (377 nm), corresponding to 9 and 5 times higher than the UV under the solar light condition. The properties and structure of the co-doped TiO2 particles before and after milling were analyzed using eight experimental methods. As a result, it was found that the nitrogen replaced as an oxygen site in milled TiO2 has the highest concertation (2.3%) in the past studies and the structure of milled TiO2 is composed of a polymorphism of four different solid phases of TiO2, gives significant higher photocatalytic activity at visible light than that of UV light. A good repeatability of the photocatalyst was investigated by the number of cycles for the decomposition reaction of the aquesous dye solution.

Chlorogermylenes and -stannylenes stabilized by diimidosulfinate ligands: synthesis, structures, and reactivity.

The reaction of the lithium salt of N,N'-di-tert-butyldiimidosulfinate ([PhS(NtBu)2]Li) having a phenyl group on the sulphur atom with ECl2·(dioxane) (E = Ge, Sn) afforded the corresponding chlorogermylene [PhS(NtBu)2]GeCl 1 and -stannylene [PhS(NtBu)2]SnCl 2, respectively. In contrast, treatment of the N,N'-bis(trimethylsilyl)diimidosulfinate ion ([PhS(NSiMe3)2]-) with ECl2·(dioxane) resulted in the unexpected formations of six-membered 1,3-bis(chlorogermylene) [PhS(NSiMe3)2(η1-η1-GeCl)2[µ-NSPh(NHSiMe3)] 7 and -stannylene [PhS(NSiMe3)2(η1-η1-SnCl)2[µ-NSPh(NHSiMe3)] 8. The structures of these chlorometallylene derivatives were fully characterized on the basis of their NMR spectroscopic data and X-ray diffraction. In the crystalline states of 1 and 2, the diimidosulfinate ligands chelate to the metal centre to form slightly hinged four-membered EN2S rings. On the other hand, X-ray analyses of 7 and 8 revealed that the central six-membered E2N3S rings adopt a distorted boat-conformation, and one diimidosulfinate ligand coordinates to the metal centre in a bridging monodentate µ-η1-η1-fashion. As the reactivity of 1 and 2, the oxidation of 1 with elemental chalcogen (S8 or Se) afforded the corresponding tetra-coordinated germanium compounds [PhS(NtBu)2]Ge([double bond, length as m-dash]Ch)Cl 3 (Ch[double bond, length as m-dash]S) and 4 (Ch[double bond, length as m-dash]Se). In sharp contrast, the reactions of 2 with elemental chalcogen resulted in the formation of four-membered Sn2Ch2 ring compounds, 1,3,2,4-dichalcogenadistannetanes {(PhS(NtBu)2)SnCl(µ-Ch)}25 (Ch[double bond, length as m-dash]S) and 6 (Ch[double bond, length as m-dash]Se).