5595
Ruthenium Complexes Containing Molecular Nitrogen A. D. Allen, F. Bottomley, R. 0. Harris, V. P. Reinsalu, and C. V. Senoff Contribution f r o m the Lash Miller Chemical Laboratories, University of Toronto, Toronto 5 , Canada. Received April 3, 1967 Abstract: T h e first transition metal complexes containing molecular nitrogen, [Ru(NH&N2lzi, were prepared by the action of hydrazine hydrate on ruthenium(II1) or ruthenium(1V) salts, or by the action of azide ion o n a q u o pentaammineruthenium(II1). A variety of Ru(I1) a n d Ru(II1) ammine complexes were obtained from these salts. + are reported and discussed. T h e characterization, spectral properties, a n d reactions of [ R u ( N H & N ~ ] ~salts
anion (saturated aqueous solution) was added to the filtrate to precipitate the desired salt. The iodide, bromide, tetrafluoroborate, and hexafluorophosphate salts precipitated immediately; the chloride salt was obtained by allowing the solution to evaporate at room temperature. The product (0.5 g) was collected by filtration, washed with water, alcohol, and ether, and air dried. Method 2. Similarly, when hydrazine hydrate (10 ml) was added to ammonium hexachlororuthenium(1V) (1 .O g), potassium pentachloroaquoruthenium(I11) (1 .O g), or aquopentaammineruthenium(II1) methanesulfonate (1 .O g) dissolved in the minimum yields of nitrogenpentaquantity of water approximately 40 ammineruthenium(I1) salts were obtained. Reaction times were 1 hr for [ R U ( N H ~ ) ~ H(CH3S0& ~O] and 12 hr for K2[RuCI,H,0] and (NH4)dRuClsl. Method 3. Aquopentaammineruthenium(I1I) methanesulfonate (1.0 g) was dissolved in water (15 ml), and sodium azide (1.0 g) was added. The solution was adjusted to approximately pH 7 with methanesulfonic acid and gently warmed for 20 min. The mixture was filtered and cooled, and the product precipitated as in method 1 , yield 0.80 g (83%). Caution: under certain circumstances it is possible to obtain explosive products from this reaction (see text). Analyses ofthe products are given in Table I. Experimental Section The amount of nitrogen (N2)obtained as a gas on heating of the compounds varied between 75 and 95% of the theoretical amount Ruthenium trichloride was purchased from Englehard Industries. present. Conventional microanalytical techniques for total The infrared spectrum of the material was routinely checked nitrogen frequently gave low values presumably due to loss of N2, for the presence of bands due to ruthenium nitrosyl complexes. Preparation of Other Complexes from NitrogenpentaammineN o attempt was made to purify the material further, and hence ruthenium(I1) Salts. The preparations of some of these complexes all references to ruthenium trichloride refer to this material, which have been reported elsewhere,14but are given here for completeness. contains both Ru(II1) and Ru(1V) species.11s12 Ammonium In some cases [Ru(NH3):N212+was not isolated from the reaction hexachlororuthenium(1V) and potassium pentachloroaquomixture. ruthenium(II1) were purchased from Englehard Industries and Hexaammineruthenium(I1) Iodide, [Ru(NH3)& T o nitrogenused as received. Aquopentaammineruthenium(II1) methanepentaammineruthenium iodide (0.54 g) in water (3 ml) was added sulfonate was prepared as described in the 1 i t e r a t ~ r e . l ~ concentrated aqueous ammonia (10 ml), and the resultant slurry All other materials were reagent grade. Solutions of sodium heated until a clear yellow solution was formed. This, on cooling, tetrafluoroborate and ammonium hexafluorophosphate were deposited yellow crystals. These were collected by filtration, refiltered before use. Solutions of N2DI were prepared by recrystallized from concentrated aqueous ammonia, and washed with peated distillation of N2H4 in DzO. ~itrogenpentaammineruthenium(I1) Complexes, [Ru(NH&JN~]~+. water, alcohol, and ether. The complex was dried in cacuo at 78" over P20j, yield 0.2 g (37%). Anal. Calcd for H1812N6Ru: H, Method 1. Ruthenium trichloride (1.0 g) was dissolved in water 3.94; N, 18.38; I, 55.58. Found: H, 4.40; N, 18.57; I, 55.40. (12 ml), and hydrazine hydrate (10 ml) was added carefully over a By a similar method starting from nitrogenpentaammineperiod of 5 min. The initial vigorous, exothermic reaction was ruthenium(I1) tetrafluoroborate (0.73 g) the analogous hexaammineallowed to subside; the mixture was stirred overnight and filtered ruthenium(I1) tetrafluoroborate salt was obtained, yield 0.55 g several times by gravity leaving a black residue. The appropriate (77%). Anal. Calcd for B2F8HlaN6Ru: H, 4.77; N, 22.28. Found: H, 4.77; N, 22.10. Chloropentaammineruthenium(II1)Chloride, [RU(NH~)~CI]CI~. To (1) M. E. Vol'pin and V. B. Shur, Nature, 209, 1236 (1966). (2) H. Brintzinger, J . A m . Chem. SOC.,88, 4305 (1966). the filtered reaction solution described in method I for the prepara(3) H . Brintzinger, ibid., 88, 4307 (1966). acid (10 ml) was added tion of [ R U ( N H ~ ) ~ N 6~ ]N~ hydrochloric +, (4) This compound was incorrectly named in earlier reports?s6 and the resultant solution refluxed for 1 hr. The yellow product (5) A. D. Allen and C. V. Senoff, Chem. Commun., 621 (1965); which separated was collected by filtration'and recrystallized from a 9th International Conference on Coordination Chemistry, St. Moritz, small quantity of water to which a few drops of concentrated 1966. hydrochlcric acid was added. The hot solution was filtered into (6) C.I.C., 49th Canadian Chemical Conference, Saskatoon, Canada, concentrated hydrochloric acid (5 ml), and the crystals obtained 1966. were collected by filtration, washed with water, alcohol, and ether, ( 7 ) F. Bottomley and S . C. Nyburg, Chem. Commun., 897 (1966). ( 8 ) J. P. Collman and J. W. Kang, J . Am. Chem. SOC.,88, 3459 (1966). and dried, in cacuo, at 78" over P20j. Anal. Calcd for C13H,,N5(9) J. P. Collman, M. Kubota, J. Y.Sun, and F. Vastine, ibid., 89, R u : N , 23.98; H , 5.19; C1, 36.39. Found: N, 23.12; H, 169 (1967). 5.44; CI, 36.10. ( I O ) A. Yamamoto, S. Kitazurne, L. S . Pu, and S. Ikeda, Chem. By exactly similar methods using hydrobromic or hydriodic acid, Commun., 79 (1967). the complexes [Ru(NH3):Br]Br2 and [Ru(NH3)J]12were obtained. (11) D. T. SaMyer, R. S. George, and J. B. Baggar, J . Am. Chem. Anal. Calcd for Br3HljNjRu: N , 16.44; H, 3.88; Br, 56.33. SOC.,81, 5893 (1959). (12) J. F . Harrod, S . Ciccone, and J. Halpern, Can. J . Chem., 39, 1372
T
ransition metals, either in the form of complexes or in the metallic form, are known to play an important part in the fixation of molecular nitrogen. Several systems have been reported in which it was deduced that a complex containing molecular nitrogen was present 1--3 although none of these intermediates was isolated. We report here, in d e t a i l , the preparation and properties of n i t r o g e n p e n t a a m m i n e r ~ t h e n i u n ~ ( I I salts, ) ~ - ~ [Ru(NH3)6N2]Xz(X = C1, Br, I, BF4, PF,). This formulation has been confirmed by single-crystal X-ray difraction analysis.' Preliminary reports of this work have been presented elsewhere.jI6 Since the completion of most of this work the p r e p a r a t i o n of two other complexes containing niolecular nitrogen has been reported, (Ph8P)zIr(Nz)C18$9 and (Ph3P)&oN2.lo
(1961). (13) R . 0. Harris, submitted for publication.
(14) A. D. Allen and C. V. Senoff, Can. J . Chem., in press.
Allen, Bottomley, Harris, Reinsalu, Senoff / Ru Complexes Containing N2
5596 Table I
-“I-
Formula
Calcd
Found
-NzCalcd
Found
H -Calcd
Other----Found
Calcd ~~
[Ru(NH3)jN2]Cly [Ru(NH3);N2]Br2 [Ru(NH~)~N~IIz [RU(”~)&I(BF~S [RU(NHJPW”dz
30.07 22.76 18.19 21.95 16.89
29,89 22,67 18.04 . . .b
9.89 7.49 5.98 7.22 5.56
. . .b
8.68 7.01 5.35 6.43 4.19
5.30 4.05 3.24 3.90 3.00
5.69 4.29 3.92 4.10 3.17
~
Found
Method of prepna
~~
CI, 24.90 Br, 42.72 I, 54.27
CI, 24.80 Br, 42.09 I, 54.05
Ru, 20.04
Ru, 18.63
1 3 3 3 3
a See text. * Repeated analyses of [ R u ( N H ~ ) ~ N ~ ] ( for B Fammonia ~)~ gave a value of 19.32x. Similarly [ R U ( N H & N ~ ] ( P Fgave ~ ) ~ 14.86%. Analyses of [ R U ( N H ~ ) ~ C ~ ] ( Pand F & [Ru(NH&](PF& by the same Kjeldahl method gave values of only 88 % of the theoretical ammonia value though microanalyses of the same compounds yielded the correct value. No explanation of this behavior can be offered.
Found: N, 16.92; H , 3.50; Br, 56.10. Calcd for H1513N5Ru: By a similar method tetrakis(pyridine)diammineruthenium(II) I, 67.19. Found: I, 67.60. hexafluorophosphate was obtained from nitrogenpentaammineBromopentaammineruthenium(III) bromide, [ R U ( N H ~ ) ~ B ~ ] B Truthenium(I1) ~, hexafluorophosphate (0.84 g), yield 0.70 g (59 7,). was also obtained from a slurry of nitrogenpentaammineruthenAnal. Calcd for CZ0FI2HZ6N6P2Ru: C, 32.39; H, 3.51. Found: iuni(I1) bromide, [Ru(NH&NZ]Brz(0.3 g), in water (3 ml) by addiC, 32.33: H, 3.63. tion of fuming hydrobromic acid (4 ml). The solution was reBoth the above complexes are very soluble in ether, benzene, fluxed for 3 hr, then cooled to room temperature, and the crude and chloroform. product was recrystallized and dried as before, yield 0.2 g (5973. Other methods of preparation for some of the above compounds A i d Calcd for Br3HIjNjRu: Br, 56.33. Found: Br, 56.20. have appeared in the literature.15-1’ Samples of these compounds (Dimethyl sulfoxide)pentaammineruthenium(II) Iodide, [Ru(NH&were prepared and proved identical with those prepared from (CH3)zSO]Iz. To nitrogenpentaammineruthenium(I1) iodide (0.55 [Ru(NH,),Nz] I+. g) in water (3 ml) was added dimethyl sulfoxide (1 ml). The reAnalyses. Carbon, hydrogen, and nitrogen analyses were persultant slurry was warmed until a yellow-brown solution formed, formed by Dr. A. Bernhardt, Mulheim, West Germany, and by which was then cooled to room temperature. On addition of excess Schwarzkopf Microanalytical Laboratories, Woodside, N. Y. potassium iodide pale yellow crystals formed, which were collected Ammonia analyses were by conventional Kjeldahl methods and by filtration and recrystallized quickly from a small quantity of halide analyses by potentiometric titration. water, washed with alcohol and ether, and dried B z vacuo at 78” over Determination of Nitrogen Gas. A known weight of [Ru(NH&PzOj, yield 0.3 g (57%). Anal. Calcd for C2H2112N50R~S: C, Nz]z+salt was introduced into bulb A (Figure 1). This was attached 5.75; H, 5.03; I, 49.70. Found: C, 5.02; H, 5.44; I, 49.20. to the vacuum line, cooled in liquid nitrogen, and evacuated. The By a similar method nitrogenpentaammineruthenium(I1) hexabulb was removed and heated over a Bunsen burner until no fluorophosphate gave (dimethyl su1foxide)pentaammineruthenfurther change was observed. Bulb A was cooled and reattached ium(I1) hexafluorophosphate, yield 0.3 g (49 %) Afial. Calcd for to the vacuum line, and it and trap B were cooled i n liquid nitroCzHZ1FlZNiOPzRuS:C, 4.33; H , 3.89. Found: C, 4.89; H, gen. Tap C was closed, and bulb A was opened to the line and the 4.32. pressure noted. By repeatedly raising and lowering the mercury column the noncondensable gas was transferred to bulb D, of known volume, until no further pressure change could be observed. Bulb D was removed and attached to a second small vacuum line of known volume, where the pressure of the gas was measured. The bulb was then removed for insertion in a mass spectrometer. By this method both the volume and composition of the noncondensable gas could be measured. Dimethyl sulfoxide solutions, 1 to 10 X M in [Ru(NH:J,N2]12,were used for the conductivity determination. These were prepared by diluting a M stock solution. Similar procedures were used to prepare solutions of [ R U ~ ~ ~ ( N H ~ )[RuIII(NHI)GIJ]IP, Is, and ( ~ - B u ) ~ N IFisher . Scientific Co. “certified reagent” dimethyl sulfoxide was used. All measurements were made at 25” on an Industrial Instruments Inc. conductivity bridge, Model RC-16B2. Infrared spectra in the KBr region were measured on a PerkinFigure 1. Apparatus for determination of nitrogen gas. Elmer “521” grating spectrophotometer as Nujol or hexachlorobutadiene mulls. The instrument was calibrated with polystyrene film between 4000 and 600 cm-1 and with water vapor between 600 and 250 cm-1. Electronic spectra were measured on a Bausch Bis(pyridine)tetraammineruthenium(II) Iodide, [Ru(NH& and Lomb “505” spectrophotometer using I-cm fused silica cells. (CJ15N)z]1z. To nitrogenpentaammineruthenium(l1) iodide (0.65 g) Mass spectral measurements were made on an Associated Electrical in water (4 ml) was added pyridine (1 ml), and the mixture was Industries MS-2 mass spectrograph using an ionization potential warmed until a dark red solution was formed (about 45 min). The of 75 ev. Proton magnetic resonance spectra were measured on a solution was cooled i n an ice bath and the bright yellow crystals Varian A-60 instrument. Magnetic moments were measured by that formed were collected by filtration and recrystallized from the Gouy method. water. The product was dried in cacuo at 78” over Pz05, yield 0 2 5 g (31%) Anal. Calcd for C10HZ212N6Ru:C, 20.65; H , 3.79; I, 43.73. Found: C, 20.36; H, 3.83; I, 43.70. Results Tetrakis(pyridine)diammineruthenium(II) Tetrafluoroborate, The complexes of [ R U ( N H ~ ) ~ N ~ion ] * +are stable, in [RU(NH~)~(C~H~N)P](BF~)~. Nitrogenpentaammineruthenium(I1) tetrafluoroborate (0.8 g) in water (8 mi) was added to pyridine (1 ml) the absence of water, for some weeks. Solutions in dry and the mixture refluxed for 2 hr forming an orange solution. This was cooled and filtered, and an excess of sodium tetrafluorobordte (15) H. Hartman and C. Bushbeck, Z . Physik. Cheni. (Frankfurt), 11, was added to the filtrate. The bright yellow precipitate was col120 (1957). lected by filtration, recrystallized from methanol-ether, and dried (16) I
