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Alwyn G. Davies Organotin Chemistry Organotin Chemistry, Second Edition. Alwyn G. Davies Copyright2004 Wiley-VCH Verlag GmbH the iodide became gradually replaced by a yellowish oily fluid, which solidified to a crystalline mass on cooling: no gas was evolved either on opening the tube or subsequently treating the residue with water . It would be interesting to ascertain what combination the radical ethyl enters in the last . decomposition”. This paper is often held to mark the first systematic study in organometallic chemistry.2, 3 Et2SnI2 2 EtI +Sn(1-1) Frankland subsequently showed that the crystals were diethyltin diiodide (equation 1-1).46 In independent work,7 Lwig established that ethyl iodide reacted with a tin/sodium alloy to give what is now recognised to be oligomeric diethyltin, which re- acted with air to give diethyltin oxide, and with halogens to give diethyltin dihalides (though through using incorrect atomic weights, the compositions that he ascribed to these compounds are wrong). As an alternative to this so-called direct method, an indirect route was devised by Buckton in 1859,8 who obtained tetraethyltin by treating tin tetrachloride with Frank- lands diethylzinc. +ZnI2Et2Zn2EtZnI 2EtI +2Zn(1-2) Et4Sn +2ZnCl2+SnCl42Et2Zn(1-3) This direct route was developed by Letts and Collie,9 who were attempting to prepare diethylzinc by reaction 12, and instead isolated tetraethyltin which was formed from tin which was present as an impurity in the zinc. They then showed that tetraethyltin could be prepared by heating ethyl iodide with a mixture of zinc and tin powder. EtI +Zn/SnEt4Sn +ZnI2(1-4) The indirect route was improved by Frankland who showed that the tin(IV) tetrachlo- ride could be replaced by tin(II) dichloride which is easier to handle and reacts in a more controllable fashion. Et4Sn +ZnCl2Et2Zn + SnCl2 (1-5) Up to 1900, some 37 papers were published on organotin compounds, making use of these two basic (direct and indirect) reactions. Organotin Chemistry, Second Edition. Alwyn G. Davies Copyright2004 Wiley-VCH Verlag GmbH see Chapter 23), in wood preservatives and as agricultural fungicides and insecticides, and in medicine they are showing promise in cancer therapy and in the treatment of fungal infections.16 1.2Nomenclature Attempts to reconcile the practices of organic and inorganic chemists in the meeting ground of organometallic chemistry have led to IUPAC sanctioning a number of alterna- tive systems of nomenclature. (1) Under the extended coordination principle, the names of the attached ligands are given, in alphabetical order, in front of the name of the central metal; anionic ligands are given the -o suffix. Thus Me2SnCl2 would be dichlorodimethyltin, and Me3SnSnMe3 would be hexamethylditin. (2) More commonly, the organic groups plus the metal are cited as one word, and the anionic component(s) as another. Thus Me2SnCl2 is usually called dimethyltin dichloride, and the common (Bu3Sn)2O (tributyltin oxide or TBTO) is bis(tributyltin) oxide. (3) Under the substitutive scheme, monotin compounds can be named by citing re- placement of hydrogen in the appropriate tin hydride. Stannane is SnH4, and Me2SnCl2 would be called dichlorodimethylstannane. The compounds Bu3SnSnBu3 can similarly be called hexabutyldistannane as a derivative of distannane, H3SnSnH3, and (Bu3Sn)2O is hexabutyl distannoxane. (4) The organotin group can itself be treated as a substituent, the H3Sn group being stannyl, and the H2Sn= group being stannio. This is useful in compounds with more complicated structures, e.g. Me3SnCH2CH2CO2H is 3-(trimethylstannyl)propanoic acid, and Et2Sn(C6H4OH-p)2 is 4,4-diethylstanniodiphenol. (5) The suffix a can be added to the stem of the substituent (giving stanna) and used to indicate replacement of carbon. This is most useful with cyclic compounds, thus cyclo-(CH2)5SnMe2 is 1,1-dimethylstannacyclohexane. Doubly bonded compounds are similarly named as alkenes with one or two of the doubly-bonded atoms replaced by tin: the compound R2Sn=CR2 is a stannene, and R2Sn=SnR2 is a distannene. (6) By analogy with alkyl radicals and carbenes (methylenes), the species R3Sn are stannyl radicals, and the species R2Sn: are stannylenes or stannyldiyls. 41Introduction Chemical Abstracts indexing practice is summarised in the 1992 Index Guide, page 199, and is as follows. (1) Acyclic compounds are named as derivatives of the acyclic hydrocarbon parents (see item 3 above), with an “ane” modification to indicate the presence of a chalcogen, for example H4Sn, stannane; H3Sn(SnH2)11SnH3, tridecastannane; (H3SnO)2SnH2, tristannoxane. (2) Heterocyclic compounds are named as stanna replacement of carbon (see item 5 above). (3) As substituent prefixes, H3Sn- is indicated by stannyl, H2Sn= by stannylene, and HSn by stannylidyne. Some illustrative examples are as follows. Bu2SnO stannane, dibutyloxo Bu2Sn2+ stannanediylium, dibutyl Me3SnCN stannacarbonitrile, trimethyltin cyanide ClSnMe2OSnMe2Cl distannoxa