Stannyl compounds, metallated

Other methylphenyl(2-phenylpropyl)stannyl-transition metal complexes are oily compounds 18). Fractional recrystallization could therefore not be applied to separate those diastereomers. For the irondicarbonylcyelopentadienyl compound (77), the diastereomeric ratio (77)A/(77)B = 45/55 could be reached by the standard route (see Fig. 9) but could not be modified by column chromatography. 

There is a limited number of examples of preparations involving the reaction of stannyl-alkali metal compounds with a substituted heteroarene, for example, Equations (58)-(60).88,197,198 Some of these reactions (e g Equation (58)) occur only with photoirradiation, showing that they involve SRN1 processes, but others may be straightforward nucleophilic heteroaromatic substitutions. 

Although many alkali and alkaline earth stannate complexes have been structurally characterized, there are only a few reports of stannyl compounds containing true metal-Sn... 

Although silyl compounds have been thus employed in photochemical reactions as all l radical donors, sufficient levels of yields are attained only in quite limited cases. As the caibon-tin bond of cation radicals of stannyl compounds cleaves quite smoothly compared with the corresponding silyl derivatives in oxidation reactions with metallic reagents (see earlier section a-All lthioalkyl Cations from a-Stannyl Sulfides ), we examined the photochemical coupling reaction using organostannyl compounds. 

The first stannyl-alkali metal compound with a covalent Sn-M bond to be identified crystallographically was the pentamethyldiethylenetriamine (PMDETA) complex of Ph3SnLi (19-4), with rSnLi av. 281.7 pm, slightly greater than the sum of the two covalent radii (274 pm), and CSnC 96.1(2)°.30 This structure is preserved in solution, and, at -90 °C, the 7Li NMR spectrum shows (SnLi) = 412 Hz. Similarly the toluene complex... 

The reduction of the stannyl radical (t-Bu2MeSi)3Sn with alkali metals produces a variety of structural modifications depending on the solvent used (Scheme 2.55). Thus, in nonpolar heptane, a dimeric stannyllithium species [58c Li ]2 (E = Sn) was formed, whereas in more polar benzene, the monomeric pyramidal structure 58c [Ti -Li (C6H5)] was produced. In the latter compound the Li+ ion was covalently bonded to the anionic Sn atom being at the same time n -coordinated to the benzene ring. A similar monomeric pyramidal CIP 58c [Li (thf)2] was prepared by reduction in polar THE the addition of [2.2.2]cryptand to this compound resulted in the isolation of the free stannyl anion 58c K+([2.2.2]cryptand), in which the ion lacked its bonding to the Sn atom. ... 

Haloarenes have been found to undergo nucleopilic substitution when irradiated with the triphenyl stannyl anion46, reacting via a radical S l mechanism. In many cases the reaction will only occur under photochemical conditions. The reaction is found to proceed with chloro- and bromo-substituted arenes, but not iodo-compounds. The anion is produced either by treatment of triphenyltin chloride or hexaphenylditin with sodium metal in liquid ammonia, and will react with a wide variety of arenes (reaction 30). 

Stannyl diazo compounds are less reactive than their lithium analogues and, containing a bigger metal atom, strongly favor reaction at N to give nitrile imines (e.g., 155 from 154). The use of bis(trimethylstannyl)diazomethane (156) provides an easy one-step route to symmetrically substituted systems (e.g., 157). 

Depending upon the coordinated solvent around the metal, several interesting features have been described. The complex [Li(dioxane)4]+[Sn(furyl)3.Li(furyl)3Sn]. 2dioxane is an ion-pair consisting of lithium ion coordinated by four dioxanes and a complex anion. The latter consists of two pyramidal (furyl)3Sn ions linked by their furyl O-atoms to a central 6-coordinated Li center124. The stannyl potassium compound [K Sn(CH2Bu-f)3 (r/6-C6II5Me)3 is the first example of a complex in which the alkali metal ion is... 

The silyl and stannyl benzodithioles 87 have been evaluated as donors <01BCJ1717> and new dihydro-TTF compounds include 88 which forms conducting salts which remain metallic down to 2K <02CC1118> and 89 whose salts are superconducting <02JA730>. 

Hexamethylditin is a suitable reagent for Pd-catalyzed metallation of aryl-halides to furnish aryltin compounds that in turn can react in Stille couplings with aryl halides to form biaryl derivatives. Hitchcock and coworkers [ 126] have shown that 2-pyridyl triflate and (hetero)aryl bromides can be coupled to 2-(hetero)aryl pyridines 174 in moderate to good yields (Scheme 66). The underlying principle of this heterocoupling of two aryl (pseudo)hahdes is the selective stannylation of the triflate that is undergoing a faster oxidative addition to the Pd(0) complex than the bromide. 

For the fast ge/w-dialkylation of 1,3-dithiane dianion, tin-lithium transmetallation at the 2-position of dithiane is a much faster process than the corresponding deprotonation. 2,2-Bis[tri(n-butyl)stannyl]dithiane (175)223 can be alkylated sequentially it was trans-metallated with n-BuLi at —78 °C, after 5 minutes treated with the first alkyl halide and after 10 more minutes the process was repeated providing dialkylated products224. This strategy has been used in the total synthesis of (—)-perhydrohistrionicotoxin, namely preparing the key compound 178 employing successively iodides 176 and 177 as electrophiles (Scheme 50)224. 

First, the utility of organostannyl compounds for generating carbo-cations or carbon radicals is discussed. Oxidation of organostannyl compounds such as a-stannyl sulfides, amines, esters, and ethers with metallic oxidants or photochemical methods gives their cation radicals, from which carbocations and carbon radicals are generated by cleavage of the carbon-tin bond. These reactive intermediates are employed for carbon-carbon bond formation, particularly in intermo-lecular reactions. 

Recent Developments in Theoretical Organometallic Chemistry. 15, I Redistribution Equilibria of Organometallic Compounds, 6, 171 Redistribution Reactions of Transition Metal Organometallic Complexes, 23, 9S Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes, 19, 213 Remarkable Features of (7] -Conjugated Diene) zirconocene and -hafnocene Complexes, 24, I Selectivity Control in Nickel-Catalyzed Olefln Oligomerization, 17, lOS Silyl. Germyl, and Stannyl Derivatives of Azenes. N H Part I. Derivatives of Diazene, N,H2, 23, 131... 

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