Three-coordinated tin

In 1951, Solerio reported that compounds with the R2SnO formula could be monomeric as well, when the tin atom carries bulky substituents, such as diorganylstannanones R2Sn=0, R = C12H25. When the substituents R are less bulky, the substrates are still polymers. Thus, Solerio can be considered as the founder of the chemistry of diorganylstannanones R2Sn=0, the first organotin compounds of three-coordinated tin, bonded to one of its substiments by a double bond. 

Despite its bulky ligands, [(Me3Si)3Si]2(Sn(/u,-Cl)Li (THF)3] (1), obtained from SnCl2 and LiSi(SiMe3)3, has a three-coordinate tin atom with a bridging chloride ion. ... 

Tin(IV) compounds are known with tin coordination numbers of 3,4, 5, 6, and in some cases >6. The search for free triorganotin cations (stannylium ions) continues, and a few examples (e.g. 25 and have been reported where three-coordinate tin atoms are likely to be present both in the solid state and in solution (Scheme 2.1.6). The extreme " Sn nuclear deshielding in the tris(silyl)stannylium ion 26 is caused by Bo-induced currents involving a -tt magnetic dipole-allowed transitions, for which the energy difference is much smaller when compared with the triarylstannylium ion 25. Examples of another new class of organotin compounds are also shown in Scheme 2.1.6. The positively charged tin centers in these zwitterionic species 27 and 28 are stabilized by coordination with C C bonds. ... 

See References 4 and 8 for more data see Reference 233 for three-coordinate tin-nitrogen compounds -diketiminatotin(ll) halides, amides, chalcogenides. 

Stannenes, doubly-bonded tin-carbon compounds, are viewed as bridge compounds to elucidate the similarities and differences between olefins (>C=C<) and distannenes (>Sn=Sn<). The bonding situations of stannenes are considered to be different from those of distannenes. In this section, the previously reported stannenes are classified into three types (i) typical examples, bearing three-coordinate tin and carbon atoms (except class 3), (ii) compounds bearing an Sn—C bond in a cumulative double-bond system, and (iii) compounds bearing a Sn—C bond in an aromatic ring. 

In the Sn(ii) complex [K(/Li3-OBu )2(/r-OBu )Sn] both metals are in distorted five-coordinated configurations in a polymeric structure of alternating potassium and tin atoms linked by bridging alkoxo groups in a structure different from the Fi and Na analogues." The binuclear potassium tin(ii) triphenylsiloxide exists in two forms both containing the K(/Lt-OSiPh3)3Sn unit with three-coordinated tin. In... 

Several reviews appeared on the heavier congeners of the carbenium ions. Clearly, the silylium ion problem has received the most attention, and both theoretical as well as experimental aspects have been reviewed. The chemistry of cationic germanium, tin and lead is covered by a recent review by Zharov and Michl. We will concentrate in this review on the description of the progress made during the last 4 years and will try to give an account on the synthesis, the properties and the structure of organosubstituted three-coordinated, tiivalent group 14 element cations and closely related species in the condensed phase. 

Considering the stoichiometry of the salt, the only feasible arrangement is with C.N.qj- 3, C.N4n-. = 6 tin dioxide assumes theTiOz or rutile structure of Fig. 4.4. Note that the radius ratio would allow three more tin(IV) ions in the coordination sphere of the oxide ion, but the stoichiometry forbids it One final example is K20 ... 

The tricyclic atrane framework is preserved under hydrolysis conditions and the hydrolysis product 449 is formally an adduct of 445, R = Me with HF and HBF4 (equation 75). According to X-ray data, the ionic 449 contains a six-coordinate tin atom, with the cation stabilized by three coordinating amino groups877. 

Until now, there was only one example of a cyclotristannene—tetrakis(tri-fert-butyl-silyl)cyclotristannene 20 reported by Wiberg and coworkers in 1999 . The tide compound 20 was prepared by the reaction of t-Bu3SiNa with stable stannylenes Sn[N(SiMe3)2]2 or Sn(OBu-f)2 in pentane at room temperature (Scheme 7). It was isolated as dark, red-brown crystals in 27% yield. In agreement with the symmetrical structure of the molecule, 20 exhibits only two sets of signals in the H, and Si NMR spectra. The most important and informative was the Sn NMR spectrum, which showed both up-field (—694 ppm) and down-field (412 ppm) resonances. The last one is typical for the three-coordinated doubly-bonded tin atoms , whereas the first one can be assigned to an endocyclic Sn atom in a three-membered ring system . ... 

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