Tin-carbon Bond Research Articles

Carbostannolysis Mediated by Bis(pentamethylcyclopentadienyl)lanthanide Catalysts. Utility in Accessing Organotin Synthons

Facile carbon–tin bond activation in the reaction of 2-(trimethylstannyl)pyridine (1) with the organolanthanide complexes Cp*2LaCH(TMS)2 (2a) and [Cp*2LaH]2 (2b) yields Cp*2La(2-pyridyl) (3), as well as Me3SnCH(TMS)2 and Me3SnH, respectively. At room temperature, ethylene then undergoes insertion into the resulting La–C(pyridyl) bond followed by carbostannolysis to catalytically generate 2-(2-(Me3Sn)ethyl)pyridine (4) or, with extended reaction times, 6-ethyl-2-(2-(trimethylstannyl)ethyl)pyridine (5). In contrast to 1, 6-methyl-2-(trimethylstannyl)pyridine (6) is unreactive, likely reflecting steric constraints. With terminal alkynes, this catalytic heterocycle–SnMe3 activation/carbostannylation process affords tin-functionalized conjugated enynes. Thus, at 60 °C 2b catalyzes the conversion 1 + 1-hexyne to yield (E)-2-butyl-1-(Me3Sn)-oct-1-en-3-yne in a 60:1 ratio E:Z isomer ratio. This reaction is available to α-monosubstituted and α-disubstituted terminal alkynes, while α-trisubstituted alkynes are too hindered for reaction. The catalytic cycle is proposed to proceed via a spectroscopically detectable Me3Sn–alkynyl intermediate which undergoes insertion into a Cp*2La–alkynyl bond to produce the conjugated alkynyl product, which is subsequently protonolyzed from the Cp*2La center by a new terminal alkyne substrate molecule. NMR spectroscopic and kinetic data support the proposed pathway and indicate turnover-limiting alkyne insertion.

Biochemistry of TBT-Degrading Marine Pseudomonads Isolated from Indian Coastal Waters

Tributyltin (TBT) is a very effective biocide and an active ingredient in antifouling paints. Screening along the Indian coast yielded 49 bacterial isolates capable of TBT assimilation. The screening was done based on the ability of bacteria to grow in mineral salt medium (MSM) containing TBT as the sole source of carbon. All the isolates produced exopolysaccharides (biosurfactants) in the medium which aid in emulsification and thus ease bioavailability of TBT. Five isolates were identified as potent TBT degraders (namely, Pseudomonas pseudoalcaligenes, Pseudomonas stutzeri, Pseudomonas mendocina, Pseudomonas putida, and Pseudomonas balearica) based on their biomass production in MSM containing TBT as the sole source of carbon. In addition to evaluating the potential of individual bacterial strains, the study also focused on using a consortium of bacteria to explore their synergistic effect when grown on TBT. Further tests like growth profile, rhamnolipid secretion profile, extracellular protein secretion profile, and detection of siderophores were performed on these isolates when grown in MSM supplemented with 2 mM TBT concentration. Emulsification activity of the crude extracellular polysaccharides against kerosene was evaluated. It can be therefore inferred that TBT degradation by these marine pseudomonads is a two-step process: (a) dispersion of TBT in the aqueous phase and (b) tin–carbon bond cleavage by siderophores affecting debutylation of TBT. The consortium of bacteria may be effective in the treatment of TBT-contaminated waste water in dry docks.

ChemInform Abstract: Kinetics of the Reactions of Allylsilanes, Allylgermanes, and Allylstannanes with Carbenium Ions.

AbsbPct Second-order rate constants for the reactions of para-substituted diarylmrbenium ions (ArAr‘CH’ = 1) with allylsilanes 2, allylgermanes 3, and allylstannanes 4 have been determined in CH2C12 solution at -70 to -30 OC. Generally, the attack of ArAr’CH+ at the CC double bond of the allylelement compounds 2-4 is rate-determining and leads to the formation of the j3-element-stabilized carbenium ions 5, which subsequently react with the negative counterions to give the substitution products 6 or the addition products 7. For compounds H2C=CHCH2MPh3, the relative reactivities are 1 (M = Si), 5.6 (M = Ge), and 1600 (M = Sn). From the relative reactivities of compounds H2C==CHCH2X (X .= H, SiBu3, SnBu3), the activating effect of an allylic trialkylsilyl (5 X IOs) and trialkylstannyl group (3 X lo9) is derived. This effect is strongly reduced, when the alkyl groups at Si or Sn are replaced by inductively withdrawing substituents, and an allylic SiCI, group deactivates by a factor of 300 (comparison isobutene/2k). A close analogy between the reactions of alkenes and allylelement compounds with carbenium ions is manifested, and the different reaction series are connected by well-behaved linear free energy relationships. The relative reactivities of terminal alkenes and allylelement compounds are almost independent of the electrophilicities of the reference carbenium ions (constant selectivity relationship), thus allowing the construction of a general nucleophilicity scale for these compounds. Allylsilanesl and allylstannanes2 have extensively been used as allyl anion equivalents during the last two decades. Their regioselective reactions with electrophiles have been explained by the intermediate formation of carbenium ions, which are hyperconjugatively stabilized by the carbonsilicon or carbon-tin bond in the 8-position (Scheme I).3 Competition experiments have shown that allyltrimethylsilane is 5 orders of magnitude more reactive toward in situ generated diarylcarbenium ions than propene; Le., the allylic trimethylsilyl group reduces the activation energy for electrophilic attack at the CC double bond by 18 kJ m01-I.~ Analogous investigations on the effect of allylic germy1 or stannyl groups on the nucleophilicity of CC double bonds have, to our best knowledge, not been performed. Indirect evidence for the magnitude of these effects can be obtained from the solvolysis rates of 8-element-substituted alkyl halidesS or trifluoroacetates (Chart 1): rates of acid-catalyzed R3MOH eliminations from 8-metal-substituted alcohols,6 or the rates of hydride abstraction in alkyl-substituted silanes, germane, and stannanes (Scheme II),’

ChemInform Abstract: Photocleavage of Carbon-Tin Bond Activated by Neighboring Carbonyl Group.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, spectroscopy, semiempirical, phytotoxicity, antibacterial, antifungal, and cytotoxicity of diorganotin(IV) complex derived from Bu2Sn(Acac)2 and 4-methyl-1-piperidinecarbodithioic acid

New diorganotin(IV) derivative of 4-methyl-1-piperidinecarbodithioic acid (4-MePCDTA) have been synthesized by the reaction of dibutyltin(Acac)2 and ligand acid in a 1: 1 molar ratio in anhydrous chloroform at room temperature. The newly synthesized complex has been characterized by elemental, IR, and multinuclear NMR (1H and 13C). The diorganotin(IV) derivative is assessed to adopt distorted octahedral geometry in the solid state, while tetrahedral geometry is exhibited in a solution state. The modeled structure of the reported complex shows severely distorted octahedral geometry around tin. The axial tin carbon bond lengths are 2.15 A. The Sn-O bond lengths for coordinated Acac in the equatorial plane are 2.37 and 2.23 A, respectively. The complex was also tested for antimicrobial activity against different bacterial and fungal strains, artemia salina cytotoxicity, and plant phytotoxicity. The screening results show that the complex exhibits high antibacterial, antifungal, and artemia salina cytotoxicity and have a potential to be used as drug. Low phytotoxic activity shows that the reported compound can be used as agrochemical. The structure-activity relationship demonstrates that the compound having four-coordinated geometry in the solution state is more toxic.

Synthesis and Properties of a Stable 6‐Stannapentafulvene.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Chemical vapor deposition of tin oxide: Fundamentals and applications

Tin oxide thin layers have very beneficial properties such as a high transparency for visible light and electrical conductivity making these coatings suitable for a wide variety of applications, such as solar cells, and low-emissivity coatings for architectural glass windows. Each application requires different properties of the tin oxide layer. These properties can be tuned by adjusting the parameters of the chemical vapor deposition (CVD) process, the main technique used for applying the tin oxide layer to the substrate. This paper discusses the state of the art of the kinetic models for tin oxide CVD. In the case of organometallic precursors the gas-phase chemistry may be initiated by cleavage of the tin–carbon bond, followed by radical-driven chain reactions that enhance the overall decomposition rate. However, in commercial tin oxide CVD reactors the gas-phase temperature may be too low or the residence time too short for these reactions to occur, thereby favoring surface chemistry. Preliminary investigations of the MBTC–H 2O–O 2 chemistry indicate that a mechanism comprising the reaction between gaseous oxygen and an adsorbed MBTC–H 2O complex is a plausible model.

Thiostannylation of Arynes with Stannyl Sulfides: Synthesis and Reaction of 2‐(Arylthio)arylstannanes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and properties of a stable 6-stannapentafulvene

The first donor-free 6-stannapentafulvene stable at ambient temperature was synthesized and isolated, exhibiting the shortest tin-carbon bond length among those previously reported.

An Overview of Forty Years Organotin Chemistry Developed at the Free Universities of Brussels ULB and VUB

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nickel-catalyzed tandem carbostannylation of alkynes and 1,2-dienes with alkynylstannanes.

Alkynes and 1,2-dienes insert into the carbon–tin bond of alkynylstannanes to afford various stannyldienynes in the presence of a nickel catalyst (see scheme). This is the first example of a transition-metal-catalyzed tandem carbometalation of two different carbon–carbon unsaturated bonds.

Thiostannylation of arynes with stannyl sulfides: synthesis and reaction of 2-(arylthio)arylstannanes.

Arynes were found to insert into a sulfur-tin sigma-bond of stannyl sulfides to give a variety of 2-(arylthio)arylstannanes, whose carbon-tin bonds were applicable to further transformations.

An overview of forty years organotin chemistry developed at the Free Universities of Brussels ULB and VUB

This review covers the main axes of research developed at the Free Universities of Brussels between 1961 and 2001. This paper first introduces the concepts developed in the field of the cleavage reactions of carbon-tin bonds of RR'RR'Sn compounds by E-N reagents yielding R-E and R'RR'SnN in non-nucleophilic and nucleophilic solvents. The addition of a nucleophile at the metal atom is needed for allowing the electrophile to cleave the carbon-metal bond. The reaction can be characterized by retention of configuration at carbon when a cyclic constraint is imposed, or by inversion of configuration when such a constraint is not effective. The stereoselectivity at tin of bimolecular nucleophilic substitutions at tin is also discussed as well as the optical (in)stability of several classes of triorganotin derivatives. In the last part of this review, the promising in vitro antitumour activities of water-soluble di- and triorganotin compounds is covered.

The oxidative cleavage of carbontin bond catalyzed by heteropolyacids of molybdenum

Abstract Heteropolymolybdoacids, H3[PMo12O40] and H6[P2Mo18O62], catalyze the oxidative cleavage of CSn bond in the organotin derivatives of dibenzyldichlorotin (1) and tribenzylchlorotin (2) in the presence of dioxygen. Benzaldehyde is the major reaction product, accompanied by smaller amounts of benzyl alcohol, benzyl chloride and dibenzyl. The results show that H6[P2Mo18O62] as catalyst and ethanol (as solvent) produce the highest yield of benzaldehyde at 65 °C. Also, 1 produces a higher yield than 2. The effects of catalyst type, temperature and solvent on the reaction time have been examined. In every case, H6[P2Mo18O62] causes the CSn bond cleavage to be achieved in a shorter time than does H3[PMo12O40].

Propargyl Derivatives with Silicon Carbon and Tin Carbon Bonds

1-Dimethylamino-propyn-2-ylsilanes 3a [Me2Si(C≡C-CH2NMe2)2], 3b [Me(H)Si(C≡C-CH2N Me2)2], 4a [Me2(Cl)Si-C≡C-CH2NMe2], 4b [Me(H)(Cl)Si-C≡C-CH2NMe2], and 5 [Me2NCH2- C≡C-SiMe2SiMe2-C≡C- CH2NMe2] were prepared. Similarly, the 1-(pyrazol-1-yl)-propin-2-ylsilanes 6 and 7 (analogous to 3a and 5, respectively) and the tin compounds 8 [Me3Sn-C≡C-CH2-pz] (pz = pyrazol-1-yl) and 9 [Me2Sn(C≡C-CH2-pz)2] were synthesized, using the reaction of Li-C≡CCH2- pz (2-Li) with the respective chlorosilanes or tin chlorides. The compounds 3 to 9 were characterised in solution by a consistent set of 1H, 13C, 29Si and 119Sn NMR data.

Preparation and Applications of Functionalized Organozinc Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Carbohydrate Derivatives Containing the Carbon-Lithium and Carbon- Tin Bonds

The monosaccharide derivatives containing the C-Sn and C-Li bonds are reviewed. Both types of these organometallics are useful intermediates in the synthesis of variety of optically pure compounds such as higher carbon sugars, C-disaccharides, carbocyclic derivatives, etc. Organometallics containing the C-Sn bond are usually stable and can be isolated in the pure form, but their reactivity is low. The tin moiety in such compounds can be replaced by the lithium atom, leading to derivatives with the C-Li bond. The latter are highly reactive but unstable. However, the lithium atom in such unstable organometallics can be replaced with tin moiety, thus providing stable stannyl intermediates, which can be easily purified. Such a facile mutual exchangeability of the metal (Li→ ;Sn and vice versa) makes these sugar organometallics particularly attractive during stereocontrolled syntheses. In this review carbohydrate derivatives containing the metal atom (tin or lithium) placed at the sp³ carbon atom as well as at sp² and sp centers (at various positions of the sugar molecule) are reviewed. In addition, selected derivatives in which the metal is connected directly to the anomeric center are described. General methods of the synthesis of these important organometallic intermediates are evaluated. Application of lithiated or stannylated monosaccharide derivatives in the stereoselective syntheses is emphasized. The mechanistic aspects of these processes are discussed. Keywords: carbohydrate derivatrive, carbon-lithium bond, carbon-tin bond, c-sn bond, c-li bond, carbon-sugars, carbocyclic derivative

Transition Metal‐Catalyzed Carbostannylation of Alkynes and Dienes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Transition Metal-Catalyzed Carbostannylation of Alkynes and Dienes

Abstract Carbon–tin bonds in alkynyl-, allyl-, acyl-, alkenyl-, and arylstannanes were found to add to carbon–carbon unsaturated bonds of alkynes, 1,3-dienes and 1,2-dienes in the presence of a catalytic amount of palladium or nickel complexes to give alkenyl- or allylstannanes having various functional groups. Mechanisms are proposed that start with oxidative addition of a carbon–tin bond, or palladacycle formation followed by β-tin elimination or by the reaction with an organostannane.

An Unprecedented κ3-[N,C,N] Coordination Mode of the Bis(3,4,5-trimethylpyrazol-1-yl)methide Ligand

Treatment of triarylstannyl-bis(3,4,5-trimethylpyrazol-1-yl)methane, Ar3SnCH(3,4,5-Me 3 Pz) 2 (Ar = phenyl or p-tolyl), with W(CO) 5 THF results in the oxidative addition of the tin-carbon(sp 3 ) bond to the tungsten(0) center to yield the heterodinuclear complexes CH(3,4,5-Me3Pz) 2 (CO)3W-SnAr3, in which four-membered metallacycles are found and bis(3,4,5-trimethylpyrazol-1-yl)methide acts as a tridentate monoanionic κ 3 -[N,C,N] chelating ligand.