Heterocycles Containing Tin-Transition Element Bonds

In contrast to rings containing all p-block elements in addition to tin, the metallacycles under discussion readily form small rings, predominantly of three or four atoms in total, which in turn can fuse together to form more complex aggregates. Large rings, even of modest six-atom proportions, are scarce. 

Heterocycles containing tin bonded to one of the group 8 triad are by far the most widely studied. Early work in the field has been reviewed (261). 

The smallest heterocycle is that containing three atoms, SnM2. Despite its widespread occurrence in many compounds, the isolated triangular heterocycle has been rarely observed, one example arising when a hindered stannylene, R2Sm [R = CH(SiMe3)2], displaces CO from Fe2(CO)9 (262) or Fe3(CO),2 [Eq. (68)] (263). Characterization of the product has been on 

Intermediate between these two forms of heterocycles is [n-R2Sn]2Fe2(CO)6 [R = CH(SiMe3)2] (83). Synthesized by reaction of R2Sn and Fe3(CO)u(MeCN), 83 is related to 82 by loss of CO. The short 

The corresponding osmium compound is isostructural. (Reproduced from Ref. 263 with permission from Elsevier Sequoia.) 

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