REDUCTION OF ETHYLENE PLATINOUS CHLORIDIZ
July 5, 1054
[CONTRIBUTION OF THE DEPARTMENT OF CHEMISTRY OF
THE
3393
CATHOLIC UNIVERSITY OP AMERICA]
The Reduction of Ethylene Platinous Chloride1 BY
JOSEPH
H. F L Y NAND N ~ HUGHM. HULBURT3 RECEIVED FEBRUARY 12, 1954
The reduction of ethylene platinous chloride with hydrogen and deuterium was investigated. The reaction in tolueue solution took place a t an appreciable rate at -40°, was auLacatalyzed by platinum and inhibited by olefins. Evidence was found for the homogeneous reduction of diethylene platinous chloride in the presence of ethylene below -10” in acetone solution, The reaction had a low activation energy of approximately two kcal. The parallelism of these reactions to the heterogeneous catalytic reduction of olefins by metals suggests that the catalytic activity of metals may be due to the properties of small groups of metal atoms rather than to macroscopic properties peculiar to crystal lattice structure. A mixed ethylene-propylene platinous chloride complex was prepared.
I. Introduction
11. Experimental
Solubilities of Ethylene Platinous Chloride in Organic The first platinum olefin compound was prepared Solvents.-Dried, distilled solvents were kept in contact by Zeise4 in 1827, who found that when platinic with an excess of ethylene platinous chloride for several chloride was boiled with ethyl alcohol, an acid solu- hours a t an elevated temperature and then for several hours tion resulted, which, upon treating with potassium a t the temperature a t which the solubility was t o be deterchloride, formed “Zeise’s Salt,’ ’ K(PtC12CZH4)Cl. mined. Five-ml. samples were pipetted into weighing the solutions slowly evaporated to dryness a t reMany other platinum-olefin complexes were later bottles, duced pressure and the bottles reweighed. discovered, but not until 1934 was the basic comPreparation of Ethylene Platinous Chloride.-The ethylpound of this series of substances-(PtC12C~.H4)~, ene platinous chloride used in these experiments was prebis (ethylene) - dichloro-p - dichlorodiplatinum(II), pared according t o the method of Kharasch and Ashford.l0 chloride powder was suspended in dried, distilled “ethylene platinous chloride”-characterized by Platinic benzene, and Dethylene (Matheson Co. C.P.) was bubbled Anderson.6 The ethylene platinous chloride obtained through a t 70 A comprehensive review by Keller6 of the litera- was recrystallized four times from hot benzene. Ethylene ture before 1940 on the platinum olefin compounds platinous chloride was also purified in a different manner. Crude ( PtC12C2H4)2was dissolved in dry aSetone and ethylhas been supplemented by reviews by Chatt.7*s ene bubbled through the solution a t -78 . Yellow PtClsThe compound (PtC12C2H4)2forms light orange ( C Z H ~ ) bis-( ~ , ethylene )-dichloroplafjnum( a),precipitated crystals that decompose when heated above 130”, out and the acetone was decanted. The precipitate was dissolve in many organic solvents, and decompose washed with cold solvent and heated to room temperature in water.5 Molecular weight determinations indi- whereupon it reverted to the monoolefin complex and ethylene. cate that the compound exists as a monomer in aceReduction of Ethylene Platinous Chloride.-A weighed tone and methyl ethyl ketoneQand as dimer in ben- sample of ethylene platinous chloride was dissolved in 50 ml. of analytical reagent grade toluene or acetone that had ~ene.~ Anderson5 found that solid ethylene platinous been dried and distilled and placed in the reaction vessel. vessel was cooled to -78” and flushed with nitrogen. chloride is quantitatively reduced by hydrogen a t The It was then warmed and maintained a t the experimental room temperature according to the equation temperature by means of a constant temperature bath consisting of a large Pyrex tube immersed in a Dry Ice-acetone (PtClsCzH,)2 f 4Hz +2Pt f 4HC1 f 2CzH6 (1) solution. This tube was partially lilled with acetone by bubbling nitrogen gas through it, and in it was The investigation of this reaction was undertaken stirred placed the reaction vessel with gas cooling coil, a Cu-conin an attempt to elucidate the role of metal catalysts stantan thermocouple with a type S Fisher potentiometer, and an immersion heater with a Cenco bimetallic regulator in the heterogeneous reduction of olefins. A preliminary investigation- of. reaction 1. in- and a tipping mercury relay. The system was flushed with nitrogen and then with solution indicated that it occurs a t an appreciable ethylene or propylene in experiments in which they were rate a t about -40” in solvents such as chloroform, used. Hydrogen and the dilutant gas were then passed acetone and toluene. The platinum formed a through drying towers and calibrated flowmeters and bubbled mirror on the sides of the glass vessel that was ca- through the reaction vessel. The olefin was removed from gas stream by two bromine traps, bromine vapor by a p& of reducing acetone to isopropyl alcohol a t the sodium bisulfite solution trap, water vapor by a dry ice room temperature. A kinetic study could not be trap, and HCl gas and the sulfur dioxide given off by the made in a static system since the ethane formed bisulfite solution by an Ascarite tube. The bromine and was soluble in the organic solvents used to dissolve bisulfite traps were removed from the system during runs in which no dilutant gas was used with the hydrogen or the ethylene platinous chloride. deuterium. The ethane was flushed into a liquid nitrogen (1) Based on a Dissertation submitted by Joseph H. Flynn to the trap by a stream of nitrogen gas and transferred to gas sampling bulbs by means of a Topler pump. The nonFaculty of the Catholic University of America in partial fulfillment deuterated hydrocarbons were analyzed in a Fisher Unitof the requirements for the degree of Doctor of Philosophy. ized Gas Analysis Apparatus (Orsat type). The deuterated (2) National Bureau of Standards, Washington, D. C. samples were analyzed by the Mass Spectrometry Section (3) Chemical Construction Corporation, New York, N. Y. (4) Zeise, Pogg. A n n . , 9 , 632 (1827); Magae. Pharm., 86, 105 of the National Bureau of Standards. (1830). Determination of Unsaturates in Platinum Olefin Com( 5 ) J. S. Anderson, J . C h e m . SOC.,971 (1934). plexes.-Potassium cyanide solution reacts with platinum (6) R. N. Keller, Chem. Reus., 28, 229 (1941). olefin complexes by replacing the unsaturate with the cy(7) J. Chatt, A n n . Repts. on Progr. Chem. (Chem. Sac. London), 4 8 , anide ion. A sample of platinum complex was placed in a 120 (1946). reaction vessel connected to a high vacuum system. The (8) J. Chatt in “Cationic Polymerization and Related Complexes,” KCN solution was contained in a bent tube connected to the
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Ed. P. H. Plesch, W. Heffer and Sons, L t d . , Cambridge, 1953. PP. 4056. (9) J . Chatt, Naluvc. 166, 839 (1950).
(10) M. S. Kharasch and T. A . Ashford, THISJ O U R N A L , 68, 1733 (1936).
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JOSEPH
H. FLY"
AND
HUGHAT. HULBURT
Vol. 76
reaction vessel by a standard taper joint. The solution was frozen and pumped out several times t o remove any occluded gases. The KCN tube was then inverted t o allow the solution t o react with the sample. The gases that were not frozen out a t Dry Ice temperatures were frozen out in the liquid nitrclgen trap, transferred to a gas sampling bulb, and analyzed in the Fisher Gas Analysis Apparatus. Propylene was removed from the mixture with 82.
