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Lithium was deposited onto lithium chloride powder in a ∼5% weight/weight ratio. This material serves as a source of elemental lithium with benefits over bulk lithium alternatives including increased mass to facilitate measurement for small scale reactions and increased surface area. The Li/LiCl material is applied in the synthesis of a dilithiobutadienide that is transformed into a stannole with a drastic decrease in reaction time and notable increase in yield over commercial lithium granules.

International audience; Polystannoles with thienyl co-monomers are in many ways similar to polythiophenes, but they display much reduced band gaps. However, their polymerization processes are not well researched. Thiophene can be oxidatively electropolymerized, but as stannoles are organometallic, the fundamental question arises whether their inclusion in a conjugated backbone can protect them sufficiently to be able to perform an oxidative electropolymerization. As well-defined oligothiophenes can be used as models to understand the optical and electronic properties of polythiophenes, we transposed this concept on stannole containing polymers; therefore we synthesized a monomeric 1 and dimeric thiophene-flanked stannole 2 and investigated their optoelectronic properties comparatively including polystannoles and the corresponding oligothiophenes in our analysis. With respect to monomer 1, a significantly redshifted absorption (max = 510 nm  = 93 nm) and a small optical band gap (Eg,opt(2) = 2.13 eV), close to the band gap of polymeric stannoles, was observed. In comparison to oligothiophenes, these thienyl-flanked stannoles exhibited a redshift in absorption and emission as well as a lower oxidation potential. Despite these differences, they showed an oligothiophene-like electrochemical behavior. Stannole 1 and the dimer 2 were subjected to an electropolymerization process. This process was investigated in detail by spectroelectrochemical methods which showed that radical cation species were formed in situ but readily decomposed. Nevertheless, under the milder multiscan cyclovoltammetric conditions, electropolymerization occurred as shown by cyclovoltammetry.

The synthesis of four well-defined conjugated polymers TStTT1–4 containing unusual heterocycle units in the main chain, namely stannole units as building blocks, is reported. The stannole–thiophenyl copolymers were generated by tin-selective Stille coupling reactions in nearly quantitative yields of 94% to 98%. NMR data show that the tin atoms in the rings remain unaffected. Weight-average molecular weights (Mw) were high (4900–10 900 Da and 9600–21 900 Da); and molecular weight distributions (Mw/Mn) were between 1.9 and 2.3. The new materials are strongly absorbing and appear blue-black to purple-black. All iodothiophenyl–stannole monomers St1–4 and the resulting bisthiophenyl–stannole copolymers TStTT1–4 were investigated with respect to their optoelectronic properties. The absorption maxima of the polymers are strongly bathochromically shifted compared to their monomers by about 76 nm to 126 nm in chloroform. Density functional theory calculations support our experimental results of the single stannoles St1–4 showing small HOMO–LUMO energy gaps of 3.17–3.24 eV. The optical band gaps of the polymers are much more decreased and were determined to be only 1.61–1.79 eV. Furthermore, both the molecular structures of stannoles St2 and St3 from single crystal X-ray analyses and the results of the geometry optimisation by DFT confirm the high planarity of the molecules backbone leading to efficient conjugation within the molecule., The synthesis of four well-defined conjugated polymers TStTT1–4 containing unusual heterocycle units in the main chain, namely stannole units as building blocks, is reported.

We succeeded in the synthesis of an anionic stannaferrocene by the reaction of a dilithiostannole with a Fe(III) reagent, which cannot be achieved by the use of cyclopentadienyl (Cp) and its relate...

Microwave-induced decomposition of the single-source precursors of a neutral triple-decker ruthenocene ( 1 ) and an anionic ruthenocene ( 2 ) both bearing a stannole ligand in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF 4 ]) gives bimetallic ruthenium-tin nanoparticles. Particles of approximate composition Ru 2 Sn (from 1 ) and Ru 3 Sn 7 (from 2 ) were obtained in this soft, wet-chemical synthesis. Transmission electron microscopy (TEM) showed the formation of 2–6 nm particles of Ru 2 Sn with its average elemental composition determined from energy dispersive X-ray spectroscopy (EDX). Crystalline Ru 3 Sn 7 nanoparticles together with α-Sn nanoparticles of 10–50 nm (from TEM) were elucidated by positive matching of the powder-X-ray diffractogram to the Ru 3 Sn 7 and α-Sn phase and the element composition from EDX.

Biaryls, such as bithiophene and bipyridyl, are intramolecularly bridged by group 14 heavy elements, silicon, germanium, and tin, to produce element blocks having condensed tricyclic systems with silole, germole, and stannole as the center ring. These bridged biaryls exhibit interesting properties arising from the characteristics of both the biaryl units and the bridging elements. In this chapter, recent development in functional organic materials containing the bridged biaryl systems as the core structure is described. The electronic states and properties of the bridged biaryls are discussed on the basis of the results of optical and electrochemical measurements and quantum chemical calculations, to explore how the element bridges contribute to the improvement of desired properties, such as photoluminescent, carrier transport, photovoltaic, and chromic properties.

Stannoles are organometallic rings in which the heteroatom is involved in a form of conjugation that is called σ*−π* conjugation. Only very little is known about how the substituents on the Sn atom or substituents on the stannole ring determine the optoelectronic properties of these heterocycles. In this work, this question has been studied experimentally and theoretically. Calculations of optimized equilibrium geometries, energy gaps between the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs), and of the absorption spectra of a wide range of compounds were performed. The computational data showed that the substituents on the Sn atom influence the optoelectronic properties to a lower extent than the substituents in the 2 and 5 positions of the ring. These substituents in the 2 and 5 positions of the stannole ring can also have a strong influence on the overall planarity of the structure, in which mesomeric effects can play a substantial role only if the structure is planar. Thus, only structures with a planar backbone are of interest in the context of tuning the optoelectronic properties. These were selected for the experimental studies. On the basis of this information, a series of six novel stannoles was synthesized by the formation of a zirconium intermediate and subsequent transmetalation to obtain the tin compound. The calculated electronic HOMO–LUMO energy gaps varied between 2.94 and 2.68 eV. The measured absorption maxima were located between 415 and 448 nm compared to theoretically calculated values ranging from 447 nm (2.77 eV) to 482 nm (2.57 eV). In addition to these optical measurements, cyclic voltammetry data could be obtained, which show two reversible oxidation processes for three of the six stannoles. With this study, it could be demonstrated how the judicious choice of the substituents can lead to large and predictable bathochromic shifts in the absorption spectra.

In this paper, a series of stable Sn-containing heteroaromatic conjugated oligomers, dialkyl dithieno[3,2-b:2′,3′-d]stannole (DTSn) and stannafluorene (SnF) derivatives, were designed and synthesized employing a new synthetic route. The distinctive feature of this route is that terminal groups are linked to the backbone before the stannole cycle closed, which can avoid the cleavage of stannole in the Stille reaction. Three Sn-heteroaromatic small molecules, DTSn-1, SnF-1 and SnF-3, have been obtained and characterized. The density functional theory (DFT) calculations show that the alkyl groups are further displaced from the conjugated backbone due to the larger atomic radius of Sn, which allows a stronger π-stacking interaction to occur. Interestingly, the fluorescence intensity of DTSn-1 is increased in the presence of Al3+ due to interaction between Al3+ and Sn. However, the emissions of the three Sn-containing oligomers can be quenched by Ru3+, which renders these compounds potential candidates as fluorescence detectors for Ru3+.

Reactions of an anionic heavy ruthenocene with CCl4, MeI, EtBr and Me3SiCl afforded the first stannole monoanion complexes. Surprisingly, coordination modes of the stannole rings are highly dependent on the substituents on the tin atom. The chloro derivative exhibits a η(4)-fashion-like coordination mode with a bent stannole ring, whereas the trimethylsilyl derivative adopts the conventional η(5)-coordination mode. Coordination modes of the alkyl derivatives are in between the two types. Cyclic voltammograms for these complexes reveal that the electron-donating character of the stannole ligand becomes stronger as the stannole ring becomes planar. Theoretical calculations elucidate that the different coordination modes originate from both electronegativity of an adjacent atom to the tin atom and bulkiness of a substituent on the tin atom.

Heterocycles that contain tin atoms can be aromatic in a similar sense to well-known aromatic compounds such as benzene or thiophene, but such examples are rare. However, due to the low-lying σ*-orbitals of the tin-substituent bond in stannoles, they are capable of σ*-π* conjugation in a way that is exclusive to heavier element containing heterocycles. This makes stannoles very interesting alternatives for purely organic heterocycles in material applications, in which optoelectronic properties are of interest. This Concept article will highlight the synthesis, reactivity and physical properties of stannoles and related fluorenostannoles. At first, a brief introduction to different types of tin-containing heterocycles is presented, followed by a discussion on different approaches to prepare stannoles, their reactivity and their physical properties. In addition, the first stannole-containing polymer will be reviewed.

The incorporation of heavier Group 14 element heteroles into semiconducting polymers leads to unusual optoelectronic properties. However, polymers containing stannoles have not been accessible to date. We report a synthetic route to a well-defined, stannole-containing polymer, the first example of this class of π-conjugated polymers. This route was made possible by developing difunctionalized stannole monomers and highly tin-selective Stille coupling reactions that leave the tin in the stannole untouched. Compared to poly(3-n-hexylthiophene), the resulting polymer displays a remarkable bathochromic shift in its absorption.

Dilithiostannoles, which are aromatic tin-containing ring compounds, were proposed to have stannylene character, as judged from their NMR analysis. We herein report on the synthesis of silyl-substituted dilithiostannoles, which were characterized by NMR spectroscopy and X-ray diffraction analysis. The silyl-substituted derivatives also exhibit features characteristic of aromatic dilithiostannoles such as 7Li NMR signals at high-field area and no C–C bond alternation in the stannole rings. Theoretical calculations and the 119Sn NMR chemical shifts revealed that the stannylene character in the silyl-substituted dilithiostannoles is enhanced due to greater interaction between 5p (Sn) and LUMO (butadiene) in comparison to those in alkyl and aryl derivatives. The 119Sn Mossbauer spectra of dilithiostannoles were measured for the first time, indicating that each of the tin atoms in dilithiostannoles can be characterized as having Sn(II) character.

The synthesis of stannole-2,5-diyl-containing π-conjugated polymers by the post-element transformation of a regioregular organotitanium polymer is described. For example, a 1,1-diphenylstannole-containing polymer is obtained in 83% yield by the reaction of a regioregular organotitanium polymer, which is prepared from 1,4-bis(2-ethylhexyloxy)-2,5-diethynylbenzene and a low-valent titanium complex with diphenyltin dichloride at -50 °C to ambient temperature. The number-average molecular weight and molecular weight distribution (Mn and Mw /Mn ) of the stannole-containing polymer are estimated as 4800 and 1.8, respectively. The obtained polymer is found to have the extended π-conjugated backbone and relatively low-lying lowest unoccupied molecular orbital (LUMO) energy level (-3.12 eV), which is supported by its UV-vis absorption spectrum and cyclic voltammetric (CV) analysis. In addition, the stannole-containing polymer is found to be applicable to a chemosensor for fluoride anion where the color and photoluminescence intensity of the polymer solution exhibits a distinct change in the presence of a fluoride anion.

Reaction of a dilithiostannole with Cp2HfCl2 (Cp = cyclopentadienyl anion, C5H5–) afforded a dinuclear hafnium complex bridged by a stannole dianion ligand, (Cp2ClHf)2[μ-η1;η1-{SnC4(SitBuMe2)2Ph2}]. The product was fully characterized by NMR, elemental analysis, and X-ray diffraction analysis. The product adopts a new coordination pattern in the coordination chemistry of metallole dianion ligands, μ-η1;η1-fashion. Unlike aromatic μ-η5;η5-stannole dianion ligands in triple-decker-type sandwich complexes we previously reported, the stannole ring of the product has 1,3-diene character, revealing its nonaromatic nature. Electronic structures of stannole dianion ligands are therefore strongly affected by their coordination modes.

An anionic ruthenocene with an η5-coordinating plumbole ligand was prepared and reacted with electrophiles to afford plumbole complexes., An anionic ruthenocene derived from a dilithioplumbole complex was prepared. In the complex, the plumbole ligand coordinates a ruthenium atom in an η5-fashion, similar to the cyclopentadienyl ligand in ferrocene. The ruthenocene that has the aromatic π-ligand with the heaviest group 14 element reacted with electrophiles to afford the plumbole complexes wherein the plumbole ligands show deviation from planarity, in contrast to the planar plumbole ring in the anionic ruthenocene. The bent angles of the plumbole ligands are dependent on the substituents on the lead atoms. Cyclic voltammetry measurements revealed that the plumbole complexes are oxidized more easily than the corresponding stannole complexes.

The aromatic compounds have for a long time played important roles in organic chemistry. The skeletons of most aromatic compounds consist mainly of carbon atoms and other second-row elements. However, a recent question is whether the concept of aromaticity can be applied when the carbon atoms of the π-frameworks are substituted by heavier group 14 atoms. In contrast to recent extensive works on the creation of silicon- and germanium-containing carbocyclic π-frameworks, which demonstrated novel heavier aromatic compounds, no one knew whether or not the concept of aromaticity could be applied to tin-containing carbocyclic compounds in 2001. We therefore targeted the synthesis of a dilithiostannole, which is a tin-analog of the cyclopentadienyl anion. Dilithiostannoles and its benzannulated derivatives were successfully synthesized by reduction of the corresponding 1,1-diphenyl derivatives. X-ray diffraction analysis of the dilithiostannoles revealed that each of the stannole rings is almost planar without bond alternation of the C–C bonds. Based on their structural features and very negative nucleus-independent chemical shift (NICS) values calculated at 1.0 A above the rings, the dilithiostannoles were concluded to be the first tin-containing carbocyclic aromatic compounds. In the benzannulated derivatives, each of the stannole rings is more aromatic than its adjacent benzene ring, as determined by theoretical calculations. The synthesis of dilithioplumbole was also accomplished and it was concluded to have considerable aromatic character, as supported by X-ray diffraction analysis and theoretical calculations. Therefore, the concept of aromaticity is now extended to lead-containing carbocyclic compounds. The reactivity of the dilithio-stannoles and -plumbole is also demonstrated.

Diethynyl(diphenyl)stannane was prepared, fully characterised in solution and in the solid state, and its reaction with triethylborane, BEt3, afforded 3-(diethylboryl)-4-ethyl-1,1-diphenyl-stannole in essentially quantitative yield. Treatment with isocyanates converted this stannole and the known analogous 1,1-dimethyl derivative into novel bicyclic compounds containing an aminoborane unit. These reactions were found to proceed diastereoselectively, again in essentially quantitative yield. The bicyclic compounds react with methanol through rearrangement and elimination of ethyl(dimethoxy)borane to give novel 1-stannacyclopent-3-ene derivatives, one of which could be structurally characterised by X-ray analysis. All final products and intermediates were studied in solution by multinuclear NMR spectroscopy (1H, 11B, 13C, 119Sn NMR).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Polymers having bis(cyclopentadienyl)titanacyclopentadiene units in the main chain were prepared by the polymerization of a low-valent bis(cyclopentadienyl)-titanium(II) complex, generated in situ from bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2) and n-butyllithium (2 equiv), with internal diynes such as 1,4-bis(1-hexynyl)-benzene and 4,4′-bis(1-hexynyl)biphenyl. The bis(cyclopentadienyl)titanacyclopentadiene-containing polymers were subjected to the reaction with tin(IV) chloride, followed by the treatment with methyllithium to give 1,1-dimethylstannole-containing organometallic polymers in moderate yields. The stannole containing polymers are soluble in organic solvents, whose number-average molecular weight was estimated to be 2,700–2,800 by GPC. Optical and electrochemical properties of the resulting stannole-containing polymers were studied by their UV-vis spectra and cyclic voltammetric analyses, from which they were supposed to have low LUMO energy levels.

The synthesis of stannole anions bearing various substituents on the tin atom is described. The reduction of hexaphenylstannole by the proper amount of lithium gave 1,2,3,4,5-pentaphenylstannole anion 1. The reaction of 1 with 1,n-dihaloalkanes (n = 1, 3, 4, 5, 6) gave the corresponding 1,n-bis(1-stannacyclopentadien-1-yl)alkanes. In contrast, the reaction of 1 with 1,2-dihaloalkanes gave the 1,1′-bistannole. The reactions of stannole dianion 3 with an equimolar amount of bulky alkyl, aryl, silyl, and stannyl halides gave the corresponding stannole anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The synthesis and structures of bi(1,1-stannole)s are described. Treatment of 1-bromo-4-(dibromophenylstannyl)-1,3-butadiene with tert-butyllithium gives the bi(1,1-stannole) having a phenyl group on each tin atom, whereas treatment of 1-bromo-4-(tribromostannyl)-1,3-butadiene with phenyl- or bulky alkyllithiums gives the bi(1,1-stannole) having a phenyl or an alkyl group on each tin atom. The X-ray analysis of the tert-butyl-substituted bi(1,1-stannole) is also described. All bi(1,1-stannole)s display two shoulder absorption bands due to π–π* and σ–π* transitions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The synthesis, structures, and physical and chemical properties of mono- and dianions of group 14 metalloles (1-metallacyclopentadiene), heavier congeners of the cyclopentadienyl anion, are described. Dianions of metalloles have a substantial aromatic character owing to strong participation of divalent resonance forms and the silole anion shows different degrees of aromaticity depending on the substituent, but there is no evidence for aromaticity in the germole anion. Dianions of benzannulated metalloles have more aromatic character in the metallole ring than in the benzene ring. The synthesis and characterization of η5-silolyl and η5-germolyl metal complexes, analogs of ferrocene, and their unique reactivity are also described.

Static and frequency-dependent electronic dipole polarisability, α, and second hyperpolarisability, γ, of the cyclopentadiene homologues C4H4XH2 (X=C, Si, Ge, Sn) were calculated by ab initio HF, MP2 and DFT-B3LYP methods using Sadlej POL basis sets, including vibrational and relativistic effects. The latter calculations were extended also to the furan homologues for comparison. The results show that both α and γ values increase monotonically as the heteroatom size increases. The energy values of the electronic transitions to the two lowest singlet 1 1 B 2 and 2 1 A 1 excited states decrease not uniformly as the heteroatom becomes heavier and the two-state model approximation is not adequate to explain the evolution of the (hyper)polarisability along the series, which indeed is essentially determined by the heteroatom property. Frequency dispersion correction on α increases down the group, by contrast γ dispersion is highest in cyclopentadiene and almost constant, at a lower value, in the heavier homologues. Electron correlation correction on the calculated properties is positive and rather large on γ. HF relativistic effects on 〈α〉 and 〈γ〉 are of little importance for both stannole and tellurophene and cannot account for the observed large discrepancy between the experimental and theoretical 〈γe〉(−ω;ω,ω,−ω) value in the latter compound. Vibrational contributions are calculated for the optically-heterodyned optical Kerr process (OHD-OKE). They are non negligible and show a clear heavy atom dependence. In the cyclopentadiene series they amount to 4–10% of 〈αe〉 and to 8–16% of 〈γe〉(−ω;ω,ω,−ω), while they are somewhat lower in the furan series. The transversal γxxxx value is higher in the cyclopentadiene than in the furan series by ca. 30–40%, suggesting that α-α′-linked cyclopentadiene homologues can be considered as valid alternatives to the corresponding furan homologues in projecting π-conjugated oligomers and polymers for NLO applications.

IR and Raman spectra and static electronic and vibrational first hyperpolarisabilities, β, of the cyclopentadiene homologues C4H4XH2 (X=C, Si, Ge, Sn) have been calculated by conventional ab initio and DFT-B3LYP methods using Sadlej POL and correlation consistent Dunning basis sets to investigate on the role of the heteroatom on the response property. The pure vibrational contribution to β has been evaluated within the double harmonic oscillator approximation. A clear heavy atom effect was found in the vibrational frequencies and intensities localised on the XH2 and C–X–C fragments, which decrease and increase, respectively, as the size of the heteroatom increases. Both βe and βv show an increase along the series, the vibrational contribution to β being modest in cyclopentadiene, but substantial in metalloles, especially for silole, where it is about two times greater than the electronic counterpart. The βv/βe ratio is strongly dependent on the basis set, decreasing as the quality of the basis set increases. Both βv and total βe+βv values of the cyclopentadiene homologues are higher than the corresponding ones in the furan series, except for stannole and tellurophene which have close total βe+βv values.

Bis(silylamino)tin dichlorides 1 [X2SnCl2 with X=N(Me3Si)2 (a), N(9-BBN)SiMe3 (b), N(tBu)SiMe3 (c), and N(SiMe2CH2)2 (d)] were prepared from the reaction of two equivalents of the respective lithium amides (Li-a–d) with tin tetrachloride, SnCl4, or from the 1:1 reaction of the respective bis(amino)stannylene with SnCl4. The compounds 1 react with two equivalents of lithium alkynides LiCCR1 to give the di(1-alkynyl)-bis(silylamino)tin compounds X2Sn(CCR1)2, 2 (R1=Me), 3 (R1=tBu), and 4 (R1=SiMe3). Problems were encountered, mainly with LiCCtBu as well as with 1b, since side reactions also led to the formation of 1-alkynyl-bis(silylamino)tin chlorides 5–7 and tri(1-alkynyl)(silylamino)tin compounds 8 and 9. 1,1-Ethylboration of compounds 2–4 led to stannoles 10, 11, and in the case of propynides, also to 1,4-stannabora-2,5-cyclohexadiene derivatives 12. The molecular structure of the stannole 11b (R1=SiMe3) was determined by X-ray analysis. The reaction of 2a and d with triallylborane afforded novel heterocycles, the 1,3-stannabora-2-ethylidene-4-cyclopentenes 14. These reactions proceed via intermolecular 1,1-allylboration, followed by an intramolecular 1,2-allylboration to give 14, and a second intramolecular 1,2-allylboration leads to the bicyclic compounds 15.

The concept of nucleophile selective cross-coupling reactions was developed for thiophene. Stannole containing semiconducting polymers were synthesized and analyzed. Das Konzept der Nucleophil-selektiven Kreuzkupplung wurde für Thiophen entwickelt. Stannolhaltige halbleitende Polymere wurden synthetisiert und analysiert.

The neutral triple-decker ruthenocenes and anionic ruthenocene bearing a stannole dianion were successfully synthesized by the reactions of dilithiostannoles with [Cp*RuCl]4. This is the first example of a transition-metal complex bearing a group 14 metallole dianion with μ-η(5):η(5) coordination mode. These complexes were fully characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. In the complexes, each of the ruthenium atoms is coordinated by the stannole ring in an η(5)-fashion. The aromaticity of the stannole dianion moieties is retained judging from no C-C bond alternation in the stannole rings. CH/π interaction was found in the packing structure of the SiMe3 derivative, which leads to a well-ordered column-like structure. The oxidation wave of the triple-decker complex was observed at -0.43 V (vs ferrocene), which reveals that the triple-decker type heavy ruthenocene is oxidized more easily than the ferrocene. Comparison of the oxidation potential between the triple-decker complex and decamethylruthenocene (Cp*2Ru, Cp* = η(5)-C5Me5) reveals that a stannole ligand functions as an electron-donating ligand much stronger than the conventional electron-rich Cp* ligand.

1-Boraadamantane (1) reacts with di(1-alkynyl)silicon and -tin compounds 2 (Me2M(C...CR)2: M=Si; R=Me (a), tBu (b), SiMe3 (c); M=Sn, R=SiMe3 (e)) in a 1:1 ratio by intermolecular 1,1-alkylboration, followed by intramolecular 1,1-vinylboration, to give siloles 5a-c and the stannole 5e, respectively, in which the tricyclic 1-boraadamantane system is enlarged by two carbon atoms. Owing to the high reactivity of 1, a second fast intermolecular 1,1-alkylboration competes with the intramolecular 1,1-vinylboration as the second major step in the reaction if the substituent R at the C...C bond is small (2a) and/or if the M-C... bond is also highly reactive, as in 2d (M=Sn, R= Me) and 2e (M=Sn, R=SiMe3). This leads finally to the novel octacyclic 7-metalla-2,5-diboranorbornane derivatives 8a, 8d, and 8e, of which 8e was characterized by X-ray analysis in the solid state. 1,1,2,2-Tetramethyldi(1-propynyl)disilane, MeC...C-SiMe2SiMe2-C...CMe (3), reacts with 1 to give mainly a 1,2-dihydro-1,2,5-disilaborepine derivative 9 and the octacyclic compound 11, which is analogous to 8a but with an Me4Si2 bridge. All new products were characterized in solution by 1H, 11B, 13C, 29Si, and 119Sn NMR spectroscopy. For 8 and 11, highly resolved 29Si and 119Sn NMR spectra revealed the first two-bond isotope-induced chemical shifts, 2delta10/11B(29Si) and 2delta10/11B(119Sn) respectively, to be reported.

Halogenation of 1,1,2,3,4,5-hexaphenylstannole was reinvestigated. Reaction of the stannole with 2 equiv. of bromine gave 1-bromo-4-dibromophenylstannyl-1,2,3,4-tetraphenyl-1,3-butadiene. Reaction of the stannole with iodine gave similar results. Reaction of the stannole with 1 equiv. of bromine or iodine afforded 1-halo-4-halodiphenylstannyl-1,2,3,4-tetraphenyl-1,3-butadiene, resulting from halogenation with the cleavage of the bond between tin and vinyl carbon. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:349–353, 2001

1-Lithio-1-phenyl- and 1-lithio-1-trimethylsilylstannoles were synthesized and the corresponding lithium salts of stannole anions were characterized by X-ray diffraction analysis. The five-membered...

The reaction mechanism of the [2 + 2 + 1] cycloaddition of two ethynes and one stannylene, SnR‘2 (R‘ = H, CH(SiMe3)2), to produce stannole catalyzed by the transition-metal complexes M(PR3)2 (1; M = Ni, Pd, Pt; R = H, Me, i-Pr, t-Bu) has been theoretically investigated by means of both density functional theory (DFT) and ONIOM methods. The DFT calculations of the model molecule with R and R‘ = H showed that the catalytic reaction proceeds via the 1,2-metallastannete intermediate 4, as experimentally proposed. The starting complex 1 first reacts with stannylene to from the stannylene complex 5, which is followed by ethyne addition to the M−Sn double bond with a small energy barrier of less than 10 kcal/mol for all three metals to form 4. The subsequent ethyne insertion into the M−Sn bond and the C−C bond formation, which require the larger energy barrier, take place to produce stannole. For Ni and Pd, the ethyne insertion needs the largest energy barrier of 11.3 and 16.4 kcal/mol, respectively. On the othe...

The compounds [SnR2(ImTSC)] (R = Me, nBu or Ph; H2ImTSC = imidazole-2-carbaldehyde thiosemicarbazone) were synthesized by treating the appropriate diorganotin(IV) oxide with the ligand in ethanol. The structures of H2ImTSC·0.5H2O and [SnMe2(ImTSC)]·EtOH were determined by X-ray diffractometry. The thiosemicarbazone chain of the former has E,E,E configuration and is almost coplanar with the imidazole ring. A rich network of hydrogen bonds involving all potential donor and acceptor groups of H2ImTSC and the water molecule stabilizes the crystal lattice. The crystal of the dimethyltin(IV) complex is composed of discrete molecules that are likewise linked by hydrogen bonds. The Sn is bound to the two methyl groups and to an N,N,S-tridentate thiosemicarbazonato dianion (ImTSC2−) in a highly distorted trigonal bipyramidal arrangement with the thioamide sulfur and the imidazole nitrogen apical. The Sn–N bond lengths [2.129(5) and 2.174(5) A] are close to the sum of the covalent radii and dominate the metal–ligand interaction. The Sn–S bond length [2.659(2) A] suggests a weak bond. The unusual co-ordination mode of the ImTSC2− anion creates four- and six-membered stannole rings. The EtOH is bound to the complex via hydrogen bonds involving the nitrogen of the imidazole that is not co-ordinated to the tin and the thiosemicarbazone NH2 group. The IR spectra of the nBu and Ph derivatives suggest that they are structurally similar to the methyl complex. 1H, 13C and 119Sn NMR spectroscopy indicates that the structure of the complexes in the solid state persists in CDCl3 solution. For H2ImTSC, 15N NMR data are presented in addition to IR and 1H and 13C NMR data.

With the exception of 1c , the 2,2-bis(1-alkynyl)-1,3-di-tert-butyl-1,3,2-diazastannacyclohexanes ( 1 ) [CCR 1 : R 1 =Me ( a ), Bu ( b ), t Bu ( c ), Ph ( d ), SiMe 3 ( e ), CH 2 NMe 2 ( f ), CH 2 OMe ( g )] react with triethylborane, Et 3 B ( 2 ), to give the spirocyclic stannole derivatives 4a , b , d , e , f , g by intermolecular 1,1-ethylboration, followed by intramolecular 1,1-vinylboration. In the cases of 1f and 1g , zwitterionic intermediates 7f , g , in which the tin atom is coordinated to an alkynylborate CC bond, were detected by NMR spectroscopy. In the case of the reaction of 1e with triphenylborane, Ph 3 B ( 3 ), exchange reactions involving the SnN bonds compete with 1,1-organoboration, and the spirocyclic stannole derivative 5e is only part of a complex reaction mixture. In the reaction of 1e with Et 3 B, an intermediate 8e with the wrong stereochemistry for ring closure was detected by NMR spectroscopy. Owing to the reversibility of 1,1-organoboration, the spirocyclic stannole 4e is finally formed. Products and intermediates were characterised by 1 H, 11 B, 13 C, 15 N, 29 Si and 119 Sn NMR spectroscopy. Several absolute signs of coupling constants in 4e were determined.

A series of group 14 metalloles, from silole to stannole, together with cyclopentadiene, having two thienyl groups at the 2,5-positions, have been prepared. Their crystal structures, UV−vis absorpt...

The title compound, [Sn(C 10 H 21 N 2 )(C 6 H 18 NSi 2 )], contains the Sn II centre in a trigonal-pyramidal geometry. The basal plane is formed by three N atoms and the fourth apical position is occupied by a stereoactive lone pair. The Sn atom is displaced from the plane of the three N atoms by 1.1968 (12) A. The Sn-N bonds are highly polarized toward the N atoms, as confirmed by natural bonding orbital analysis.

Various structural (C−C bond length equalization, D), energetic (isodesmic stabilization energies, ISE), and magnetic (diamagnetic susceptibility exaltations, Λ and nucleus-independent chemical shifts, NICS) criteria are employed (using B3LYP, CSGT, and GIAO ab initio methods) to assess the aromaticity and antiaromaticity of a variety of group 14 (E = C, Si, Ge, Sn, Pb) metalloles: C4H4EH2 (C2v), C4H4EH- (Cs and C2v; C, D5h), C4H4EH+ (singlet, C2v), C4H4EHLi (Cs; C, C5v), and C4H4ELi2 (C2v). In addition, structural trends are established for C4H4ELi- (Cs) and for C4H4E2- (C2v) as well as for the singlet and triplet C4H4E (C2v) sets. The increased pyramidality at E down group 14 results in strongly decreased aromaticity of metallolyl anions C4H4EH- (Cs). In contrast, all planar C4H4EH- (C2v) geometries are significantly more aromatic. Although all C4H4EH+ (C2v) structures are planar, the antiaromaticity in singlet C5H5+ is much higher than that of the heavier congeners (E = Si to Pb). The four-π-electron ...

Stannoles bearing dialkylboryl groups in 3-position react with 1-phospha-1-alkynes P≡CtBu (1) and P≡CCH2tBu (2) by [4 + 2] cycloaddition and elimination of stannylene to give phosphabenzenes in high yield. The stannylenes oligomerise to give [R12Sn]n with n ≥ 7 (R  Me, Et, -(CH2)5− or, in the case of R1 = tBu, react with the stannole itself. All phosphabenzenes are characterized by their consistent sets of NMR data. The absolute signs of the coupling constants nJ(31P, 1H), nJ(31P, 13C), 2J(31P, 29Si) and 2J(119Sn, 31P) were determined by appropriate ID and 2D NMR experiments.

1,1-Diethynyl-1-stannacyclohexane (5) was prepd., and its reaction with triethylborane or 9-isobutyl-9-borabicyclo[3.3.1]nonane gave the corresponding spiro-Sn compds. 6 and 7 (shown as I) with a stannole fragment. The mol. structure of 7 was detd. by x-ray anal. (triclinic, space group P.hivin.1; a 835.2(7), b 1117.5(2), c 1165.6(2) pm; a 72.05(3), b 74.32(3), g 50.61(3) Deg). Treatment of 6 with trimethyltin ethoxide gave at 1st quant. the spiro-Sn compd. 8 with a 2-stannolene unit which rearranges upon heating into the spiro-Sn compd. 9 with a 3-stannolene unit. The reaction of 7 with trimethyltin butoxide gave quant. another tetracyclic compd. 10, analogous to 8. All compds. were characterized by 1H, 11B, 13C and 119Sn NMR data. Numerous coupling signs nJ(119Sn1H) and nJ(119Sn13C) and 2J(119Sn117Sn) were detd. by 2-dimensional 13C/1H and 119Sn/1H heteronuclear shift correlations. 7 Was studied by solid-state 13C and 119Sn CPMAS NMR. This revealed a 2nd cryst. phase in the bulk of the solid material, as confirmed by powder x-ray diffraction data. 119Sn CPMAS NMR spectra of 7 show resolved scalar 119Sn-11B coupling (3J(119Sn11B) = 68 +- 5 and 65 +- 5 Hz).

A palladium-catalyzed (2 + 2 + 1) cycloaddition reaction of two C2H2 and one SnR2 to form C-unsubstituted stannoles (C4H4)SnR2 [R = CH(SiMe3)2 2a, R2 = {C(SiMe3)2CH2}2 2c] is described. Catalysts are (R‘2PC2H4PR‘2)Pd complexes (slow reaction) and (R‘3P)2Pd complexes (fast reaction). The mechanism of the catalysis has been elucidated in detail from stoichiometric reactions based on R = CH(SiMe3)2. For the [(R‘2PC2H4PR‘2)Pd]-catalyzed system, the starting Pd(0)−ethene complexes (R‘2PC2H4PR‘2)Pd(C2H4) (R‘ = iPr (3), tBu (4)) react both with ethyne to give the Pd(0)−ethyne derivatives (R‘2PC2H4PR‘2)Pd(C2H2) (R‘ = iPr (5), tBu (6)) and with SnR2 to yield the Pd(0)−Sn(II) adducts (R‘2PC2H4PR‘2)PdSnR2 (R‘ = iPr (7), tBu (8)). The Pd−Sn bond [2.481(2) A] of 7 is very short, indicative of partial multiple bonding. Subsequent reactions of the Pd(0)−ethyne complexes 5 and 6 with SnR2 or of the Pd(0)−Sn(II) complexes 7 and 8 with ethyne afford the 1,2-palladastannete complexes (R‘2PC2H4PR‘2)Pd(CHCH)SnR2 (Pd−Sn) (R‘ =...

Synthetic routes to the metallole species C4Me4E(H)R (9, E = Si, R = Si(SiMe3)3; 10, E = Si, R = Mes (mesityl); 11, E = Ge, R = Si(SiMe3)3; 12, E = Ge, R = Mes), C4R4E(SiMe3)2 (13, E = Si, R = Me; 14, E = Ge, R = Me; 19, E = Si, R = Et; 20, E = Ge, R = Et), and C4Me4E(R)E(R)Me4C4 (15, E = Si, R = SiMe3; 16, E = Si, R = Me; 17, E = Ge, R = SiMe3; 18, E = Ge, R = Me) are described. In the presence of 18-crown-6, dihalides 1 and 2 are reduced by potassium in tetrahydrofuran to give crystalline samples of the silole dianion [K(18-crown-6)+]2[C4Me4Si2-] (21) and the germole dianion [K4(18-crown-6)3][C4Me4Ge]2 (22). Compound 21 adopts an inverse-sandwich geometry, while 22 is a dimer with a bridging [K(18-crown-6)K]2+ group and η5-binding modes for all of the potassium atoms. The metallole dianions in these structures appear to possess delocalized π-systems, as evidenced by nearly equivalent C−C bond lengths in the five-membered rings. Silolyl and germolyl anions have been obtained by various methods involving ...

Reduction of 1-t-butyl-1,2,3,4,5-pentaphenylstannole by lithium gave the stannole dianion. Reduction of the bi(1,1-stannole) having a t-butyl group on the tin by lithium also gave the stannole dianion, the formation of which was evidenced by spectral analysis and chemical trapping reaction.

A new triorganotin chloride, (E)-2-Chloro(dimethyl)stannyl-3-diethylboryl-N,N-dimethyl-2-pentenylamine (4), was prepared via 1,1-ethyloboration. Compound 4 reacts with alkynyltin compounds of the type R1-CC-SnMe3 [R1 = Me (a) tBu (b), SiMe3 (c), SnMe3 (d), CH2OMe (f)] and Me3PbCCPbMe3 (e) via elimination of Me3SnCl or Me3PbCl (e) to give zwitterionic intermediates 5a,c–f in which a cationic triorganotin fragment is stabilized by side-on coordination to the CC bond of an alkynylborate group and by a coordinate NSn bond. The intermediates 5c-e are the first examples of (η2-alkyne)tin compounds where an organometallic substituent is linked to the bridging alkynyl group. These intermediates rearrange at room temperature to give the pure stannole derivatives 6c-f. The synthesis of 6b requires heating under reflux for several hours; no intermediate was detected. The analogous reaction of (E)-2-chloro(dimethyl)stannyl-3-diethylboryl-2-pentene (7) with R1-CC-SnMe3 (R1 = SiMe3, SnMe3) or Me3Pb-CC-PbMe3 afforded the analogous stannoles 8c-e, but the intermediates corresponding to 5 were too short-lived for NMR spectroscopic detection. All intermediates and the final products were characterized by extensive one- and two-dimensional multinuclear magnetic resonance studies (1H, 11B, 13C, 15N, 29Si, 119Sn and 207Pb NMR), including the determination of a negative sign for the coupling constant 1J(207Pb13C) in the intermediate 5e.

Reactions of Ph3SnCl and RSnCl3 (R = Me, n-Bu) with R4 N+Cl− and disodium maleonitriledithiolate, Na2(mnt), yield the monostannole [((CN)2C2S2)SnPh3][Me4N] (1) and the new distannoles [((CN)2C2S2)2,SnR][Et4N] [R = Me (2), n-Bu (3)]. X-ray analysis reveals the geometries of 1 as trigonal bipyramidal and 2 and 3 as square pyramidal. The tristannole [((CN)2C2S2)3Sn][Et4N][Na] (4) results from Sn-C bond cleavage of PhSnCl3 in a hydrolysis reaction with Na2(mnt) and Et4N+ Cl−. The geometrical data on organotin complexes containing ring unsaturation, 1-3, and related anionic five-coordinated tin compounds show that the distortion coordinate expressing solid-state nonrigidity is the Berry pseudorotational coordinate. As a result of this work, one is able for the first time to compare structural principles for five-coordinated compounds established for other main-group 14 and 15 elements. Their significance in reaction mechanisms is discussed. Stannole 1 crystallizes in the monoclinic space group Cc with...

Bis(trimethylstannylethynyl)phenylphosphane (1) reacts regio- and stereoselectively via 1,1-organo-boration with one equivalent of triethylborane (4a) or triisopropylborane (4b) to give the (Z)-alkene derivatives 5a and 5b, respectively, in quantitative yield. With an excess of 4a the bis(alkenyl)phosphane 6a is formed ((Z)-configuration of both alkenyl groups). The reaction between bis(dimethylphos-phanylethynyl)dimethyltin (2) and 4a leads to a complex reaction mixture, whereas bis(diphenylphos-phanylethynyl)dimethyltin (3) reacts with 4a to give selectively the organometallic substituted stannole derivative 8a. In this case, a zwitterionic intermediate (9a) was identified by 1H-, 11B-, 13C-, 31P and 119Sn NMR. In 9a a positively charged triorganotin fragment is stabilized by intramolecular π-coordination to the C[tbnd]C bond of an alkynylborate group. The reaction between 3 and 4b affords a mixture (12:1) of the stannole derivative 8b and the 1-stanna-4-bora-2,5-cyclohexadiene derivative 10b. ...

The 1,1-organoboration of 2,2-di-1-alkynyl-1,3-di-tertbutyl-1,3,2-diazastannacyclohexanes (1) has been studied. Treatment of 1 with triethylborane (2) gave first a zwitterionic intermediate 6 in which a diamino(organo)tin cation is stabilized by side-on π-coordination to the CC bond of an alkynylborate moiety. The final products proved to be the spirocyclic stannoles 7. In the reaction between 1 and triisopropylborane (3) the intermediate of type 6 could not be detected, but the final product 8 has the same spirocyclic structure as 7. Multinuclear 1H, 11B, 13C, 15N 119Sn NMR served for monitoring the reactions and characterization of intermediates and final products.

The 1,1-organoboration of 2,2-di-1-alkynyl-1,3-di-tertbutyl-1,3,2-diazastannacyclohexanes (1) has been studied. Treatment of 1 with triethylborane (2) gave first a zwitterionic intermediate 6 in which a diamino(organo)tin cation is stabilized by side-on π-coordination to the CC bond of an alkynylborate moiety. The final products proved to be the spirocyclic stannoles 7. In the reaction between 1 and triisopropylborane (3) the intermediate of type 6 could not be detected, but the final product 8 has the same spirocyclic structure as 7. Multinuclear 1H, 11B, 13C, 15N 119Sn NMR served for monitoring the reactions and characterization of intermediates and final products.