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The photo-reduction induced dissolution and single crystal formation of compound [PPh4]4[PMoVMoVI11O40]·2CH3(C6H5)NCHO (1) occur upon irradiation of sunlight on the suspension of an yellow polycrystalline compound [PPh4]3[MoVI12O40] in N-methylformanilide (NMF).

Phosphanyl-substituted tin(ii) half sandwich complexes are reported, which exhibit Lewis acidic tin atoms and Lewis basic phosphorous atoms and form head-to-tail dimers.

Elucidating the bonding situation in a titanium complex with an anionic N-heterocyclic olefin ligand.

The synthesis of persistent sila‐ and germacyclopentadienyl (silolyl‐ and germolyl‐) radicals by careful stoichiometric reduction of the corresponding halides with potassium is reported. The radicals were characterized by EPR spectroscopy and trapping reactions. The reduction of tris(trimethylsilyl)silyl‐substituted halides was successful while smaller substituents (i. e., t‐Butyl, Ph) gave the corresponding dimers. The EPR spectroscopic parameter of the synthesized tetrolyl radicals indicate only small spin delocalization to the butadiene unit due to cross‐hyperconjugation. Silolyl‐ and germolyl anions are unavoidable byproducts and are isolated in the form of their potassium salts and characterized by X‐ray crystallography. The comparison of the molecular structures of two closely related potassium silolides provided an example for different coordination of the potassium cation to the silolyl anion (η1 vs. η5 coordination) that triggers the switch between delocalized and localized states., Persistent silolyl and germolyl radicals were synthesized by reduction of sterically congested halide precursors. The radicals are pyramidalized and show only little spin delocalization.

The synthesis of 1-silolyl and 1-germolyl triflates from the corresponding chlorides by salt metathesis reaction is reported. These covalent triflates are ideal starting materials for the preparation of ionic silolyl- and germolyl-imidazolium triflates by their reaction with N-heterocyclic carbenes. Similarily, ionic silolyl- and germolyl-oxophosphonium triflates are obtained by substitution of the triflate group by triethylphosphane oxide Et

The stabilizing neighboring effect of halo substituents on silyl cations was tested for a series of peri‐halo substituted acenaphthyl‐based silyl cations 3. The chloro‐ (3 b), bromo‐ (3 c), and iodo‐ (3 d) stabilized cations were synthesized by the Corey protocol. Structural and NMR spectroscopic investigations for cations 3 b–d supported by the results of density functional calculations, which indicate their halonium ion nature. According to the fluorobenzonitrile (FBN) method, the silyl Lewis acidity decreases along the series of halonium ions 3, the fluoronium ion 3 a being a very strong and the iodonium ion 3 d a moderate Lewis acid. Halonium ions 3 b and 3 c react with starting silanes in a substituent redistribution reaction and form siliconium ions 4 b and 4 c. The structure of siliconium borate 4 c 2[B12Br12] reveals the trigonal bipyramidal coordination environment of the silicon atom with the two bromo substituents in the apical positions., Silyl cation or halonium ion? That′s the question: The Corey reaction of acenaphthyl‐ and naphthyl‐based silanes allows the synthesis of silyl halonium ions, the nature of which was confirmed by NMR spectroscopy, X‐ray diffraction analysis, and DFT calculations. Moreover, the chloro‐ and bromonium ion can react with the starting silane to form penta‐coordinated siliconium ions, which are intramolecularly stabilized by electron donation from both halogen atoms.

Treatment of potassium salts of silole dianions with donor stabilised germanium dichlorides gave the anticipated silagermafulvenylidenes R2Si = Ge(Do) (R2Si = 1-silacyclopentadiendiyl, Do = N-heterocyclic carbene (NHC)) only as transient intermediates in a side reaction. They were detected by NMR spectroscopy and, in one case, the formal dimer, 2,4-disila-1λ3,3λ3-digermetane, was isolated. The main products of these reactions are sila-bis-λ3-germiranes, i.e. directly interconnected digermylenes that are part of a three-membered ring. The structural data, supported by the results of density functional calculations confirm the digermylene nature of these products with a long inner cyclic Ge–Ge bond that decreases the inherent high ring strain in silagermiranes., The reaction of silole dianions with NHC stabilised germanium dichloride affords 3-sila-1l3,2l3-digermiranes, three-membered ring compounds that are directly interconnected digermylenes.

The reaction of the titanium imido complex 1b with 2-butyne leads to the formation of the titanium azadiene complex 2a at ambient temperature instead of yielding the archetypical [2 + 2] cycloaddition product (titanaazacyclobutene) which is usually obtained by combining titanium imido complexes and internal alkynes. The formation of 2a is presumably caused by an initial propargylic C(sp3)–H activation step and quantum chemical calculations suggest that the outcome of this unexpected reactivity is thermodynamically favored. The previously reported titanaazacyclobutene I (which is obtained by reacting 1b with 1-phenyl-1-propyne) undergoes a rearrangement reaction at elevated temperature to give the corresponding five-membered titanium azadiene complex 2b.

Cyclic silylated chalconium borates 13[B(C6F5)4] and 14[B(C6F5)4] with peri‐acenaphthyl and peri‐naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis‐ and trans‐isomers in the case of phenylmethylsilyl cations. With the bulkier tert‐butyl group at silicon, the configuration at the chalcogen atoms is predetermined to give almost exclusively the trans‐configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atoms of sulfonium ions 13 c and 14 a are substantial (72–74 kJ mol−1) as shown by variable temperature NMR spectroscopy. The neighboring group effect of the thiophenyl substituent is sufficiently strong to preserve chiral information at the silicon atom at low temperatures., The Corey reaction of acenaphthyl‐ and naphthyl‐based chiral silanes allows the synthesis of silylchalconium ions with control of the stereochemistry at the chalcogen atom (shown here for the sulfonium ion). The chalcogen neighboring group effect on the silyl cation is sufficiently strong to conserve the stereochemistry in a consecutive nucleophilic attack.

The titanocene imido complex 2 with a m-terphenyl moiety is synthesized by reacting Cp2Ti(η2-Me3SiC2SiMe3) (1) with m-terphenyl azide. Subsequent reactivity studies with tetrahydrofuran, pyridine, ...

By changing the dimethylamino to a nitro group, a novel synthetic access to the spirocyclic opioid analgesic cebranopadol was developed that is much more efficient compared with the established route. On the basis of the α-acidity of α-nitrotoluene, the two-fold Michael addition to acrylate gave an acyclic precursor compound, which was easily transformed by Dieckmann condensation and decarboxylation to the cyclohexanone derivative needed for the annulation of the indole ring by an oxa-Pictet-Spengler reaction. As an additional benefit, the reduction of the nitro group furnished an amine, which could be late-stage-diversified to carboxamides, sulfonamides, ureas, and N-alkyl congeners. The transformation of the nitro group at the spirocyclic scaffold to the dimethylamino function of the actual title compound was achieved in one step with zinc/formic acid/formaldehyde in 83% yield.

The first examples of titanium‐catalyzed hydroaminoalkylation reactions of ethylene with secondary amines are presented. The reactions can be achieved with various titanium catalysts and they do not require the use of high pressure equipment. In addition, the first solid‐state structure of a titanapyrrolidine that is formed by insertion of an alkene into the Ti−C bond of a titanaaziridine is reported., No high pressure equipment is required for achieving the hydroaminoalkylation of ethylene with secondary amines in the presence of titanium catalysts (see scheme). This finding is in good agreement with the observation that the insertion of ethylene into the Ti−C bond of titanaaziridines, which are regarded to be the catalytically active species of hydroaminoalkylation reactions, takes place easily to give titanapyrrolidines.

This contribution reports on the reactivity of isothiocyanates towards the boranes B(C6F5)3 and HB(C6F5)2. The reactions of alkyl-substituted isothiocyanates with B(C6F5)3 were found to result in rearrangement reactions to yield stable thiocyanate–B(C6F5)3 adducts. Treatment of isothiocyanates with HB(C6F5)2 leads to 1,2-hydroboration and thus, B,N,C,S heterocycles are formed, which react further under non-inert conditions. Hydrolysis of the hydroboration products leads to a new access to thioformamides.

The reactions of dipotassium germacyclopentadienediide with two Group 13 dichlorides, Cp*BCl2 and Cp*AlCl2, yield two structurally different products. In the case of boron a borole complex of germanium(ii) is obtained. The aluminium halide gives an unprecedented neutral germaaluminocene. Both compounds were fully characterised by multinuclear NMR spectroscopy supported by DFT computations. The molecular structure of the germaaluminocene was determined by XRD., Boron vs. aluminum: the synthesis of a borole complex of Ge(ii) is reported. Changing just the element from boron to aluminum unexpectedly yields an unprecedented neutral germaaluminocene.

The synthesis of the novel room temperature stable titanacyclopropane derivative Cp*Ti(η2-C2H4)(η5-C5H4AdH) (2) in a one-step-two-transformation protocol and first insights into its reactivity are presented, including the synthesis of the corresponding bis(trimethylsilyl)acetylene complex Cp*Ti(η2-Me3SiC2SiMe3)(η5-C5H4AdH) (4). Given these results, a novel one-pot procedure toward Cp2Ti(η2-Me3SiC2SiMe3) was subsequently developed.

The impact on chiral aggregation in solution processed and thermally annealed thin films of two indolenine and one anilino squaraines with chiral (S)-citronellyl functionalization at the nitrogen of the squaraine backbone is investigated. A pseudo polymorphic crystal structure is obtained for one of the indolenine squaraines, but thin films of both compounds are basically non-aggregated and truly isotropic as evidenced by spectroscopic ellipsometry. The anilino squaraine coalesces and readily aggregates to circular dichroic but discontinuous thin films. The extent of circular dichroism correlates with the morphology of the samples, which is quantified by Mueller matrix polarimetry in combination with atomic force microscopy. The shape of the CD spectra reinforces the hybrid Frenkel and charge-transfer excitonic nature of the characteristic double hump signatures within unpolarized absorbance spectra of previously investigated non-chiral anilino squaraines with linear alkyl chain functionalization. Such excitonic CD offers an additional design parameter for next-generation opto-electronic devices.

Intermolecular hydroaminoalkylation reactions of symmetrical and unsymmetrical alkynes with tertiary amines take place in the presence of catalytic amounts of TiBn

The reaction of the titanium imido complex 1b with 2-butyne leads to the formation of the titanium azadiene complex 2a at ambient temperature instead of yielding the archetypical [2 + 2] cycloaddition product (titanaazacyclobutene) which is usually obtained by combining titanium imido complexes and internal alkynes. The formation of 2a is presumably caused by an initial propargylic C(sp3)–H activation step and quantum chemical calculations suggest that the outcome of this unexpected reactivity is thermodynamically favored. The previously reported titanaazacyclobutene I (which is obtained by reacting 1b with 1-phenyl-1-propyne) undergoes a rearrangement reaction at elevated temperature to give the corresponding five-membered titanium azadiene complex 2b., An unexpected reactivity between a titanium imido complex and internal alkynes was unveiled yielding titanaazacyclobutenes instead of the expected [2 + 2] cycloaddition products.

The improved multigram synthesis of the bis(π-η5:σ-η1-benzofulvene)titanium complex 1 is reported. On the basis of this, the follow-up chemistry of complex 1 was investigated and selective mono or ...

The synthesis of the alkylated pentafulvene titanium complex Cp*Ti(CH2 SiMe3 )(π-η5 :σ-η1 -C5 H4 =CR2 ) (CR2 =adamantylidene) is described. The coordination mode of the pentafulvene ligand in this complex allowed for the subsequent synthesis of a series of nitrile-insertion products. By reacting these neutral compounds with the strong Lewis acid B(C6 F5 )3 , unprecedented selective methyl-group abstractions from the SiMe3 moieties under formation of novel cationic titanium complexes with the corresponding MeB(C6 F5 )3 - anion are demonstrated. The proposed silylium ion intermediates of these reactions are directly stabilized by either the exocyclic carbon atom of the pentafulvene ligand or by the lone pairs of the nitrogen atoms of the chelating Cp,N-ligands. In addition, a titanium enamine complex and its reaction with B(C6 F5 )3 is reported, which results in the formation of a betaine.

The first examples of early-transition-metal-catalyzed hydroaminoalkylation reactions of allenes are reported. Initial studies performed with secondary aminoallenes led to the identification of a suitable titanium catalyst and revealed that under the reaction conditions, the initially formed hydroaminoalkylation products undergo an unexpected titanium-catalyzed rearrangement to form the thermodynamically more stable allylamines. The assumption that this rearrangement involves a reactive allylic cation intermediate provides a simple explanation of the fact that no successful early-transition-metal-catalyzed hydroaminoalkylations of allenes have previously been reported. As a result of the generation of the corresponding cation, the titanium-catalyzed intermolecular hydroaminoalkylation of propa-1,2-diene unexpectedly gives an aminocyclopentane product formed by incorporation of two equivalents of propa-1,2-diene.

The reaction of penta- and benzofulvene complexes of group 4 (M = Ti, Zr) with different phosphorus ylides is reported. Employing the bis(η5:η1-pentafulvene)titanium complexes Ti1a and Ti1b, the reactions with the corresponding phosphorus ylides Y1–5 result in a spontaneous single C–H bond activation and metallocene ylide complexes Ti2a–e can be isolated in good yields. On the basis of these results, this reactivity pattern has been extended to the mono(η5:η1-pentafulvene) and -benzofulvene complexes Ti3, Zr1a,b, and Zr1a,b-benzo. Transferring this to the titanium complex Ti3, an additional equilibrium between the reaction product (η5-C5Me5)(η5-CpAd)Ti(Cl)CHPPh3 (Ti4a) and the corresponding “tuck-in” complex (η5:η1-C5Me4CH2)(η5-CpAd)TiCl (Ti4b) can be observed. In Ti4b, a methyl group of the Cp*-ligand is activated by the coordinated phosphorus ylide. Using this intramolecular C–H activation, Ti4b can be synthesized by catalytic amounts (3 mol %) of the phosphorus ylide Y1 in quantitative yield. Subsequen...