The Trimethylplatinic Group

Abstract

Pope and Peachey¹ prepared diamminotrimethyl platinic iodide, (CH₃)₃PtI(NH₃)₂, readily soluble in alcohol, but sparingly soluble in water. We now find that pyridine added to trimethylplatinic iodide in benzene gives after concentration dipyridinotrimethyl-platinic iodide, (CH₃)₃PtI(C₅H₅N)₂, m.p. 168°, without previous decomposition, and that similarly from all proportions of dipyridyl and trimethylplatinic iodide, dipyridyltrimethylplatinic iodide, (CH₃)₃PtI, dipy, is obtained, insoluble in water, but soluble in chloroform and acetone, m.p. 268–273°. It is apparently unchanged by boiling with dilute acetic acid, hydrochloric acid, ammonia or twice normal sodium hydroxide. It is, however, decomposed by ethylene diamine with formation of sesquiethylene-diaminetrimethylplatinic iodide, 2(CH₃)₃PtI.3en which may be recrystallized from water. The latter compound can also be prepared from excess of ethylene diamine and trimethylplatinic iodide in benzene. Its structure is probably : recalling that of iron enneacarbonyl². On refluxing ethylenediamine with excess of trimethylplatinic iodide in benzene, trimethylplatinicmonoethylene-diamine iodide, m.p. 204° with decomposition, is obtained. Both ethylenediamine compounds are soluble in water. All four compounds, as also the stable association of trimethylplatinic acetylacetone into double molecules^3,4, are examples of the familiar stability of 6-covalent compounds of quadrivalent platinum.