Stannyl properties

Trialkyl (triaryl)stannyl methacrylates were copolymerized with ethylene and methyl methacrylate and it was shown that the resulting copolymer offers improved mechanical properties as compared to ethylene, and high fungicidal activity. It was suggested that homopolymers and copolymers of triethylstannyl methacrylate contain a covalent and an ionic bond between the carboxy group and the tin atom 63). 

The synthesis of organotin oligosteracrylate i.e. dimethylstannyl dimethacrylate, and the production of the cross-linked homopolymers on its basis have been reported. Morphology, mechanical and relaxation properties of poly(dimethyl-stannyl dimethacrylate) have been investigated 67). 

The heteroaromatic stannanes undergo the normal electrophilic substitution reactions of their protic precursors, and often to an enhanced degree. They are often prepared with the aim of a subsequent Stille cross-coupling reaction, and oligothiophenes with potentially useful optical and electron properties have been prepared by coupling between stannyl- and bromo-thiophenes, for example, Equation (63).204... 

Upon addition of cyclopropane 1 to one equivalent of SnCl in methylene chloride at 0 °C, an exothermic reaction occurs to give 3-stannyl propionate 11 in approx. 70% yield [9, 11]. Addition of a second equiv of the cyclopropane slowly converts 11 to the dialkylated tin compounds, 12 Eq. (15). No further alkylation was observed. Chelate structures of such homoenolates implied by their spectral properties are supported by single crystal X-ray analysis [30]. 

The purpose of this article is to summarize the preparation and properties of silyl, germyl, and stannyl derivatives of azenes N H (n = 2-5). This part II of the review deals with known Group IV derivatives of triazene, tetrazene, and pentazene (n = 3-5 excluding purely organic substituted triazenes and tetrazenes, cf. refs 2,3). Group IV derivatives of diazene were discussed in Part I of the review (1). 

Some physical properties of silyl, germyl, and stannyl derivatives of triazene or organyltriazenes that have been isolated to date, along with their methods of preparation, are listed in Table I. In general, triazenes can be categorized into five types (18a-18e) of triazenes or organyl-... 

Chemical properties of silyl-, germyl-, and stannyl triazenes have not been studied very systematically so far. Most of the known compounds are air stable and sensitive to hydrolysis. Thermostability of triazenes of type 18a (R = organyl) is strikingly high, and these can often be heated above 150°C without decomposition. On the other hand, the known triazenes of type 18c (R = aryl) decompose slowly at room temperature. Triazenes of type 18b, 18d, and 18e are even more thermolabile and can be prepared only if triazene substituents are quite bulky [e.g., f-Bu3 SiN3H(Sir-Bu3) is stable above 150°C]. For more details of triazene thermolysis, which occurs mainly with N2 elimination, see Section II,C. 

From photophysical measurements, the recommended best values for the o+ values of stannyl methyl groups are Ph3SnCH2 -0.73(2), Me3SnCH2 -0.81, and (Me3Sn)2CH -1.06.44 However, no systematic studies of chemical reactions or physical properties of organotin compounds appear to have been carried out with the aim of determining elec-... 

Little work has been carried out on the properties of these stannyl hydroperoxides and distannyl peroxides. Their thermal instability might suggest homolysis of the 0-0 bond, but the cleavage of the R-Sn bond which is observed might equally be regarded as re-... 

Quantum mechanical methods have been used to calculate Sn NMR properties such as chemical shifts and coupling constants, for stannane, tetramethylstannane, methyltin halides, tin halides, and some stannyl cations. Relativistic effects were included by using the ZORA method. Each method allows the possibility of including only scalar effects or spin orbit coupling as well. " Sn chemical shifts and spin-spin couplings were calculated and compared to experimental values. A favorable correlation was shown for the chemical shifts, except for organotin species where heavy atoms are bound to tin, in which case a good correlation was obtained only at the spin-orbital level. Therefore, it is clear that relativistic effects must be considered for these heavy-element tin systems. 

The hydrostannation of alkenes, which has been known for nearly 30 years, follows a polar or a free radical way depending on substituents and conditions ". Under free-radical conditions, the stannyl radical generally adds reversibly either to double or triple bonds and this property has been used to control the vinyltin configuration depending on experimental conditions (equation 18). Therefore, with an excess either of acetylenic compound or of tin hydride, it is possible to obtain mainly the (Z)-isomer (kinetic control) or the (F)-isomer (thermodynamic control). ... 

---