137 



ORGANOMETALLIC BODIES. 



ORGANOMETALLIC BODIES. 



139 



liquids of most unbearable odour. They readily oxidise in contact 

 with air, forming the respective oxides. Telluriumamyl has not yet 

 been obtained in a state of purity. 



The oxides of these bodies are powerful bases, expelling ammonia 

 from its Baits and attracting carbonic acid from the air. They form 

 salts of considerable stability, which, together with the oxides them- 

 selves, yield the original organo-tellurium compounds when treated 

 with sulphurous acid ; thus, 



Te 



Tellurous cthoxide. 



Telluriumetbyl. 



COSSTITUTIOX OF ORGANOMETALLIC BODIES. 



The organometallic bodies are supposed to be constructed upon the 

 types of tie inorganic chlorides, sulphides, oxides, &c., of the respective 

 metals which they contain, the chlorine, oxygen, sulphur, &c., being 

 replaced in equivalent proportion, and step by step by the alcohol 

 radicals. A reference to the formulae of orgiino-potar-sium, sodium, 

 magnesium, zinc, and cadmium compounds given above, shows that 

 they are all formed upon the models of the protochlorides of these 

 metals : 



(Cl 

 M \Cl 



The organo-aluminium compounds are formed upon the model of 

 the sesquichloridu of that metal : 



(Cl 

 Al, Cl 



(ci 



Organo-tin compounds are in like manner represented by the three 

 chlorides of tin : 



So. 



- 



The bismuth series are modelled upon the terchloride of bismuth 

 and bismuthic acid : 



(Cl 



Bi{ Cl 



Cl 



Bi 



( 







o 

 V o 



The lead compounds are constructed upon two of the oxides of this 

 metal : 



( 



MS 



\ O 

 The mercury series have for their mould the bichloride of mercury : 



Pb, {O 

 



The antimony series are formed upon the following inorganic com- 

 pounds of that metal. 



a 

 Cl 

 Cl 



In like manner organo-arscnical compounds are constructed after the 

 following types : 



( O 

 (Cl 



tola 



(Cl 



Finally, organic compounds containing tellurium are derived from 



T 

 Te 



Cl 



Te, 



Occasionally an abnormal compound has made its appearance, 

 such as ethostibylic acid (Sb(C,H,,)0,), or iodide of triethylstibine 

 (Sb(C,Hj)jI), but further research has invariably demonstrated the 

 incorrectness of such formula; and the conformity of the bodies with 

 the normal inorganic types. Indeed this law may now be regarded as 

 no firmly established, as to be applicable to the control of the formulas 

 of new organometallic bodies. From this point of view it is in- 

 teresting to watch the effect of the substitution of chlorous or negative 

 by basylous or positive radicals in metallic compounds. Such a sub- 

 stitution affords striking evidence of the dependence of the chemical 

 character of a compound upon that of its individual constituents; a 



phenomenon which is strikingly seen in the case of highly polyatomic 

 metals, such as arsenic and antimony. Thus tribasic arsenic acid, by 

 the substitution of an equivalent of methyl for oxygen, yields the 

 bibasic monomethyl-arseuic acid, a well denned acid of considerable 

 energy, though inferior in chlorous power to arsenic acid. The like 

 substitution of a second equivalent of methyl for oxygen reduces the 

 chlorous character of the body to the comparatively feeble condition in 

 which we find it in cacodylic acid, which is incapable of forming an 

 ammonia salt. A similar substitution for the third time overpowers 

 the chlorous character of the compound altogether, and we now have a 

 feeble biacid base the arsenic dioxymethide ; which again, by the 

 exchange of a fourth atom of oxygen for methyl, is transformed into 

 the oxide of tetramethylarsonium, a base of such energy as to be 

 comparable with the caustic alkalies themselves. 



The history of the orgauometalh'c bodies teaches forcibly a doctrine 

 which affects all chemical compounds, and which may be called the 

 doctrine of atomic saturation ; each element is capable of combining 

 with a certain limited number of atoms, and this number can never be 

 exceeded, although the energy of its affinities may have been increased 

 by combination up to this point. Thus zinc attains its atomic satura- 

 tion by uniting with only one atom of another body, in other words, 

 it is uniatomic ; consequently, the zinc compounds of the alcohol 

 radicals, notwithstanding their intense affinities, are incapable of com- 

 bination. The action of chlorous elements upon them is one of 

 substitution, not of combination. Polyatomic metals exhibit the same 

 phenomenon : a double atom of tin cannot combine with more than 4 

 atoms ; a single atom of arsenic or antimony with more than 5 atoms 

 of other bodies. But in the combinations of polyatomic metals, we 

 frequently notice from the lowest to the saturated compound one or 

 more intermediate points of exalted stability ; thus, antimony has a 

 teratomic stage of comparative stability ; nitrogen, phosphorus, and 

 arsenic, whilst exhibiting a similar teratomic stage, have also a biatomic 

 one, though of greatly inferior stability ; whilst the existence of pro- 

 toxide of nitrogen, and especially the recent researches of Mr. Griess 

 render it more than probable that nitrogen has a third and uniatomic 

 stage. In bodies possessing at least one stage of stability below 

 saturation, and in which all the atoms united with the polyatomic 

 element are of the same kind, the stage of maximum stability is very 

 rarely that of saturation. Thus in nitrogen, arsenic, and bismuth 

 compounds of the kind just mentioned, the stage of maximum stability 

 is decidedly the teratomic one ; in antimonial compounds of a similar 

 nature, the teratomic is also, though less decidedly, the stage of 

 maximum stability ; whilst in phosphorous compounds, the points of 

 maximum stability and saturation generally coincide. When, however, 

 the atoms united with the polyatomic element are not of the same kind, 

 then the stage of maximum stability usually coincides with that of 

 saturation. Thus the binoxide or bichloride of triethylarsine, or 

 triethylstibine, are more stable than triethylarsine or triethylstibine 

 themselves ; but this pentatomic stability reaches its climax in arsonium, 

 stibonium, and phosphouium compounds, as it does also in the corres- 

 ponding compounds of nitrogen, although the latter element exhibits a 

 much stronger tendency towards universal teratomio stability than its 

 chemical associates. 



In polyatomic organometallic bodies it is remarkable that, with few 

 exceptions, the positive hydrocarbons hold their position much more 

 tenaciously than the associated negative constituents ; and wo thus 

 frequently find the former accompanying the metal through a vast 

 number of compounds ; hence the group formed by the metal and 

 positive hydrocarbons has come to be regarded as a compound radical : 

 thus cacodyl is conceived to be the radical of the whole series of 

 cacodyl compounds : but however great may be the convenience of 

 this mode of viewing organometallic compounds, and the same mode 

 has notoriously been extended to nearly all organic bodies, it must not 

 be forgotten that it is a purely artificial distinction which has no real 

 existence, either in the case of organometallic bodies, or in that of 

 organic bodies in general. A close examination of the habits of the 

 so-called organometallic radicals clearly shows that their atomic power 

 depends upon their position with regard to the stages of stability and 

 maximum saturation ; thus they are uniatomic when the number of 

 positive groups is one less than that required to reach either the 

 maximum saturation of the metal, or a lower stage of stability. 

 Cacodyl and tetramethylarsonium, for instance, are uniatomic radicals, 

 because they are respectively one atom short of the stage of stability 

 and of maximum saturation : 



Uniatomic Stage of maximum 

 saturation. 



Cacodyl 



Chloride of 

 cacodyl. 



Tcirnmethyl- 



iirsoiiium. 



Chloride of 



tetrauiethylarsonium. 



It is obvious, that under favourable circumstances, a compound 

 radical, the number of whose positive atoms is below that of a stage of 

 stability, can have a double atomic character. Thus cacodyl is some- 



