B.— CHEMISTRY 41 



As far as the work on the chemistry of gold in which my colleagues 

 and I have been concerned the chief advances have been achieved by 

 studying in the first place the organic derivatives of the metal and, more 

 recently, the gold derivatives of certain types of organic sulphur com- 

 pounds. 



(a) Dialkyl halogeno compounds. 



It is almost exactly thirty-one years ago since Sir William Pope and 

 I (1907) prepared the first organic gold compound, then styled diethyl- 

 auric bromide, just after he and Peachey (1909) had prepared the first 

 organic platinum compound, trimethylplatinic iodide. But it was not 

 until 1930 that the work could be resumed (Gibson and Simonsen 1930, 

 Gibson and Colles 193 1). In the earlier investigations the poor yield 

 of the product of the interaction of the Grignard reagents and the ether 

 soluble hydrochloro- or hydrobromoauric acids, HAUX4.3H2O, rendered 

 the detailed study of these new organic gold compounds somewhat 

 difficult. As starting material, the easily prepared pyridinotrichlorogold 

 — -less frequently, the corresponding bromine derivative — is now used 

 and the following reaction is carried out in an ether-pyridine mixture 

 using the relative quantities indicated : 



2C5H5N.AUCI3 + 4MgRBr -> aCjHsN.AuRaBr + z^gCU_ + MgBrj 



The pyridine co-ordination compound is decomposed later by the action 

 of hydrobromic acid and the compound isolated through its water 

 soluble co-ordination compound with ethylenediamine which, again, 

 may be decomposed by a suitable acid. It takes some three to four hours 

 to obtain the pure material and the average yield is rather more than 

 25% of the theoretical quantity and yields as high as 38% have been 

 obtained. 



The isolation of homologues of the first prepared compound was easily 

 accomplished. The experimental proof that these are non-electrolytes, 

 that they have molecular weights corresponding to those of twice their 

 empirical formulae and that they and their co-ordination compounds all 

 contain 4-covalent auric gold led to the realisation that the 4-covalency 

 is an essential feature of all auric compounds. The existence of gold 

 compounds having the general empirical formula, AuRg (R = univalent 

 hydrocarbon radical), is therefore impossible since such compounds 

 could not contain 4-covalent gold. Taking the ethyl compounds as 

 typical, the following are examples of some of the non-electrolytes which 

 have been prepared : 



C^Hs Br C,H5 



\ / ^ / 

 Au Au 



C2H5 Br C.,H, 



Diethylmonobromogold. 

 Col. anorthic needles, m.p. 58° (decomp.). 

 mol. wt. = 670. [jl = 1.41 D in CCI4 or CgHg. 



c 2 



