OH- as a Reducing Agent for Ru Trimers Table zyxwvutsrqpo 111. Mutual Atom Polarizabilities? nr.1 zyxwvutsrqp = aqr/aQ1 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Inorganic zyxwv Chemistty, Val. zyx 12, No. 2,1973 zy 323 MeN4P4F7, 371 10-97-7; 1,1-Me2N4P4F6, 29021-59-8; trans-1,5-Me2N4P4F6 , 371 10-98-8;Me2N4P4F6, 37164- 25-3; 1,1,3-Me3N4P4FS, 371 10-93-3;1,l ,5-Me3N4P4F5, 371 10-94-4; 1,l ,5,5-Me4N4P4F4, 29 144-50-1 ; Me8N4P4, 4299-49-4. Acknowledgments. We thank the National Research Coun- cil of Canada for financial support, the University of British Columbia for a University Graduate Fellowship (to T. N. zy R.), and Dr. L. D. Hall and Mr. R. Burton for the heteronuclear decoupling experiments. Chem., 49, 164 (1971). (19) N. L. Paddock, T. N. Rpnganathan, and S. M. Todd, Can. J. (20) T. Chivers and N. L. Paddock, Inorg. Chem., 11, 848 (1972). Atom (r) 1 2 3 4 5 p = 1 +0.273 -0.096 -0.023 -0.006 -0.023 P =2 +0.166 -0.068 -0.010 -0.003 -0.004 a HMO calculations; CYN = ap + pp; homomorphic. by an addition reaction, which can be understood similarly, and a preliminary account of this work has appeared.lg Con- jugative,” solvent, and reagent effects are also important and will be considered later. Registry No. MeLi, 917-54-4; N4P4F8,14700-00-6; Contribution from the Department of Chemistry, Georgetown University, Washington, D. C. 20007 Hydroxide Ion as a Reducing Agent for Cations Containing Three Ruthenium Atoms in Nonintegral Oxidation States JOSEPH E. EARLEY* and TERENCE FEALEY Received June 9, 1972 Hydroxide ion is oxidized by Ru(NH,),ORu(NH,),ORu(NH,),7c in a second-order reaction for which k is 1.9 X lo4 sec-’ M-’ (at 25“ in buffered media of ionic strength 0.25 zyxwvut M) and zyxwvut AH* is 19 kcal/mol. An isosbestic point exists throughout the reaction but chemical evidence shows than an intermediate is involved. The corresponding oxidant which has two ethylenediamine ligands replacing the four ammonias on the central ruthenium atom is reduced faster but with a similar A*. The spectra of the four ruthenium trimers involved in these reactions are consistent with a molecular orbital scheme. All the data are consistent with a mechanism involving rate-determining attack of OH- on the central ruthenium atom. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA I There have been reports’,’ of a curious reaction by which OH- is rapidly oxidized by (NH3)5RuORu(NH3)40Ru- (NH3)5 7+ (“ruthenium brown,” hereafter I) with the produc- tion of the corresponding 6f cation (“ruthenium red,” here- after 11). Previous workers’ suggested that the OH radical was the oxidation product of OH-, but this seems unlikely since the I + I1 potential is only 0.75 V zyxwvuts us. the normal hy- drogen electrode, which appears insufficient3 to produce OH. Strong oxidants such as MnO, normally react with OH- only quite slowly,4 but the ruthenium trimer I reacts rapidly with OH-. We have investigated this system to de- termine why such a mild oxidant oxidizes OH- so readily. We recently described5 the synthesis of an analog of the 6+ ion with two ethylenediamine (en) groups replacing the NH3 groups on the central ruthenium atom and also an X-ray structure determination of this ion. We now re- port spectra of four interrelated compounds (en and NH3, 6+ and 7f). The remarkable reactivity of I with OH- can be rationalized on the basis of a molecular orbital scheme based on these spectra. Experimental Section LiClO, was prepared from Li,CO, and HClO,, digested in so- (1) J. M. Fletcher, B. F. Greenfield, C. J. Hardy, D. Scargill, (2) J. E. Earley and T. Fealey, Chem. Commun., 331 (1971). (3) P. George and J. S. Griffith, Enzymes, 1, 347 (1959). (4) R. Veprek-Siska, V. Ettle, and A. Regner, Collect. Czech. (5) P. M. Smith, T. Fealey, J. E. Earley, and J. V. Silverton, and J. L. Moorhead, J. Chem. Soc., 2000 (1960). Chem. Commun., 31, 1237 (1966). Inorg. Chem., 10, 1943 (1971). lution overnight at 40-50” to remove SO,, and recrystallized three times from triply distilled water. The chloride salt of “ruthenium red” (11) was prepared as fol- lows. RuCl, .3H,O (5 g) was dissolved ip 25 ml of 0.25 M HCI. Absolute alcohol (5 ml) and ascorbic acid (0.1 g) were added and the brown solution was refluxed at 85’ for 3 hr and then concentrated to 5 ml under reduced pressure. Concentrated NH, (20 ml) was added a few milliliters at a time and the mixture was held at 85-90’ for 1 hr while streams of air and ammonia gas were passed through the solution. Concentrated ammonia solution was added as neces- sary to maintain the volume of the reacting solution at approximately 20 ml. The reaction mixture was centrifuged while hot, and the supernatant liquid was then cooled in an ice bath. A brown powder was collected by filtration, recrystallized from 0.1 M ammonia, and washed with ethanol and ether (yield 2 n). Anal. Calcd for Ru-0,- (NH,),C16.3H,0: Ru, 36.10; N, 23.33; C1, 25.31. Found:6 Ru,- 36.12; N, 23.10; C1, 27.58. In order to prepare the chloride salt of ruthenium brown (I), the chloride of I1 (1.0 g) was dissolved in water at 40” and 2 M HC1 was added until the pH of a cooled aliquot was 1 .O. A stream of air was then passed through the warm solution for several hours. The mix- ture was cooled and a brown powder was collected by filtration and washed with 0.1 M HC1 and ether (yield 0.8 g). Anal. Calcd for RU,O,(NH,)~,C~,~~H,O~HC~: Found: Ru, 33.48; N, 21.90; C1, 31.18. Needle-shaped crystals were grown by rapid evaporation of solutions of the chloride of I. The ethylenediamine (en) analog of 11, namely, Ru,O,(NH,),,- (en),C16 .H,O (hereafter II’), was prepared as previously described. In order tQ prepare the oxidized analog (hereafter I’), 50 mg of I1 chloride was dissolved in a minimum quantity of water. The solu- tion was acidified and 2 drops of chlorine water (-10 mM) were added. The color of the solution rapidly changed from red to brown. A few drops of a saturated solution of NaCl in 0.01 M HC1 Ru, 33.82; N, 21.90; C1, 31.69. (6) P. M. Smith, Thesis, Georgetown University, 1971.