Tetraalkylstannanes

A comparative analysis of the IR spectra of monomers under study and known model compounds (tetraalkylstannanes and unsaturated oxiranes) indicates corresponding shifts of absorption bands for the oxirane ring and the Sn—C bond. 

The chemical behavior of tetraalkylstannanes is radically different from that of the far more reactive aluminum alkyls. The tin compounds are stable in air, they do not react with water, and they do not... 

Tetraalkylstannanes with an a-halo substituent undergo a, fi-elimination in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 90), yielding vinylstannanes with predominant -configuration, as shown in reaction 17273. 

Tetraalkylstannanes with double bonds at allylic or more remote positions undergo cross-coupling with allylsilanes to yield dienes, as illustrated in reaction 47299. 

Tetraalkylstannanes with a /i-acyloxy group undergo highly stereospecific elimination to yield Z - or E -unsaturated products, depending on whether the organotin compound has erythro- or threo-configuration, as depicted in reactions 72 and 73, respectively324. 

Tetraalkylstannanes undergo transmetallation reactions leading to reactive intermediates that may be combined with electrophilic substrates, as shown, for example, in reaction 74325. 

No unreacted tetraalkylstannane is observed when a full equivalent of bromine is employed. 

This result dictated that any alkene-generating elimination process has to proceed via conditions not basic enough to enolize the tertiary amide. Using a procedure developed by Ochiai, the tetraalkylstannane unit of 119 was converted into the chlorotrialkylstannane of 121 in excellent yield. The formation of a halotin species enabled the use of the Tamao-Fleming oxidation36 for formation of the primary alcohol within 122. 

Whereas aliphatic and aromatic thiols cleaved the C—Sn bond in tetraalkylstannanes to give trialkylorganylthiostannanes768,855, the analogous reaction in organosilicon chemistry is absolutely unusual. According to Seyferth789,818 (1957), the vinyl group was especially easy to cleave from tin atom by mercaptans. 

The complexes of tetraalkylstannanes SnR4 with tetracyanoethylene (TCNE)85 are more stable than those with oxygen. The Sn—C bond serves as a a -donor in this case. The Kq values of such complexes are also defined predominantly by the degree of shielding of the donor centre. With change of R these constants diminish in the series Me >> Et > i- Pr > i-Bu > f-Bu. The steric hindrance to the complexation of Me4- PbEt with TCNE is smaller in comparison with the isostructural tin compounds as expected on the basis of the larger Pb interatomic Pb-C distance85. 

Second-order rate constants for the reaction of mercury(II) chloride with tetraalkylstannanes according to equation 28 ... 

Tetraalkylstannanes and phosphorus pentafluoride are commercially available. Commercial phosphorus pentafluoride contains a small amount of phosphoryl fluoride, but its presence does not hinder the exchange reaction or cause any subsequent difficulties in workup of the products. It may be removed if desired, however, by carefully fractionating the commercial sample through —112° (CS2 slush) and —196° traps. The former trap will retain the phosphoryl fluoride, whereas the pentafluoride will pass this trap and collect at —196°. The vapor pressure of phosphorus pentafluoride at —96° (toluene slush) is 335 mm. Hg the purity of the sample may be checked by comparison of its vapor pressure against this value. 

A slight modification of the above description is necessary if this reaction is to be used for the synthesis of other alkylfluoro-phosphoranes (CH3CH2PF4, CH2=CHPF4, n-CH3CH2CH2PF4). Because all other tetraalkylstannanes are not transferable in a vacuum system at 25°, they can be syringed into the reaction bulb before attachment to the vacuum lines. Care to use dry samples and equipment must be observed, however, since the presence of even small amounts of water will lead to formation of phosphoryl fluoride and silicon tetrafluoride. 

For the first time tetraiodostannane was used in the reaction with tetraalkylstannanes by Pope and Peachey in 1903. They demonstrated that heating Me4Sn with Snl4 at >100°C led to MesSnl and MeSnD. Pii4Sn did not react with SnD even at 240°C. 

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