Organotin chemistry
The area remains rich with many applications in industry and continuing activity in the research laboratory.
Di- and especially tri-organotin halides, e.g. tributyltin chloride, exhibit toxicities approaching that of hydrogen cyanide.
The distannoxanes exist as dimers with the formula [R2SnX]2O2 wherein the X groups (e.g., chloride –Cl, hydroxide –OH, carboxylate RCO2−) can be terminal or bridging (see Table).
Numerous examples of hypercoordinated compounds are provided by the organotin oxides and associated carboxylates and related pseudohalide derivatives.
The all-organic penta- and hexaorganostannates(IV) have even been characterized,[7] while in the subsequent year a six-coordinated tetraorganotin compound was reported.
For example, tributyltin hydride (tris(n-butyl)stannane) serves as a useful source of "hydrogen atoms" because of the stability of the tributytin radical.
Indeed, compounds with the formula R2Sn=SnR2, called distannenes or distannylenes, which are tin analogues of ethylenes R2C=CR2, are known for certain organic substituents.
Such species reversibly dimerize to the distannylene upon crystallization:[12] Stannenes, compounds with tin-carbon double bonds, are exemplified by derivatives of stannabenzene.
One prominent family of cages is accessed by pyrolysis of the 2,6-diethylphenyl-substituted tristannylene [Sn(C6H3-2,6-Et2)2]3, which affords the cubane-type cluster and a prismane.
However, such reactions are temperamental, typically requiring a very weak carbon-halogen bond (e.g. an alkyl iodide or an allyl halide) or crown-complexed alkali metal salt catalyst.
For example, treatment of dibutyltin dichloride with lithium aluminium hydride gives the dibutyltin dihydride, a colourless distillable oil:[18] The Wurtz-like coupling of alkyl sodium compounds with tin halides yields tetraorganotin compounds.
[19] Alternatively, stannides attack organic electrophiles to give organostannanes, e.g.:[2]: 49 Important reactions, discussed above, usually focus on organotin halides and pseudohalides with nucleophiles.
[21] Organotin hydrides are unstable to strong base, disproportionating to hydrogen gas and distannanes.
[2]: 299, 334–335 Conversely, mineral acids cleave distannanes to the organotin halide and more hydrogen gas.
[2]: 300 In "pure" organic synthesis, the Stille reaction is considered is a key coupling technique.
Diorganotin carboxylates, e.g., dibutyltin dilaurate, are used as catalysts for the formation of polyurethanes, for vulcanization of silicones, and transesterification.
[2] n-Butyltin trichloride is used in the production of tin dioxide layers on glass bottles by chemical vapor deposition.
[2] Tributyltin compounds were once widely used as marine anti-biofouling agents to improve the efficiency of ocean-going ships.
Concerns over toxicity[22] of these compounds (some reports describe biological effects to marine life at a concentration of 1 nanogram per liter) led to a worldwide ban by the International Maritime Organization.
