J. Am. Chem. SOC.1980, 102,7461-7467 S, 20.27. Found: C, 45.85; H , 3.72; S, 20.23. [C5H5Mo(S)SC2H51Z. A procedure analogous to that described above was followed. The solution was stirred at 60 OC for 48 h. The product was recrystallized from chloroform/hexane. Yield: 14%. Anal. Calcd: C, 33.08; H, 3.94; S, 25.23. Found: C, 32.81; H , 3.86; S, 25.02. Reactions with Unsaturated Molecules. [CH3C5H4Mo(S)SHI2(0.20 g, 0.4 mmol) was dissolved in 25 mL of CHCI3 in a 60-mL reaction vessel, the solution was degassed in two freeze-pumpthaw cycles, and the unsaturated species was added (2 atm of C=C, 1 atm of C=C, or 2 mL of C6H5CH2NC). The solution was stirred at room temperature for 1-2 days. In the reaction with ethylene, vapors from the reaction vessel were sampled and analyzed by GC to identify hydrogen. The product molybdenum complexes were crystallized by partial evaporation of the solvent and characterized by NMR and elemental analyses. For [ C H ~ C ~ H ~ M O S CNMR ~ H ~ (CDCIS): S]~ 6 1.69 (s, 8, C2H4), 2.04 (s, 6, CH,), 4.98 (s, 8, C5H4). Anal. Calcd: C, 35.96; H, 4.12; S, 23.97. Found: C, 36.02; H, 4.08; S, 23.78. For [CH3C5H4MoSC2H2SI2 NMR (CDCI,): 6 2.06 (s, 6, CH,), 5.82 (br s, 8, C5H4),6.49 (s, 4, C2H2). Anal. Calcd: C, 36.23; H , 3.42; S, 24.18. Found: C, 36.43; H, 3.37; S, 24.30. For [CH3C5H4MoS2CNCH2C6H5I2 NMR (CDCI,): 6 1.88 (s, 6, CH,), 4.41 (s, 4, CH2-), 5.21 (br s, 8, C5H4),7.28 (s, 10, C6H5). Anal. Calcd: C, 47.18; H, 3.97; S, 17.99. Found: C, 46.93; H, 3.90; S, 17.89. The reaction of [(CH3)5C5Mo(S)SH]2with ethylene was carried out in dry T H F in an analogous manner. NMR of [(CH,)SC5MoSC2H4SI2(CDCI,): 6 1.68 (s, 8, C2H4), 1.80 (s, 30, CHI). Anal. Calcd: C, 44.57; H, 5.92; S, 19.83. Found: C, 44.53; H, 5.89; S, 19.76. Reactions of the unsubstituted cyclopentadienyl derivative were analogous. Products were identified by comparison of NMR spectra with those of known s a m ~ l e s . ~ * ~ ~ H2/D2 Exchange.' [CH3CSH4Mo(S)SHl2(0.2 g) was dissolved in dry benzene (10 mL) in a 50-mL flask, and the solution was degassed in two freeze-pumpthaw cycles. Approximately 0.75 atm of H, and 0.25 atm of D2 were added, and the soluhon was stirred at 25 "C fo; 3 days. Mass
746 1
spectrum analysis showed that approximately 12% of the gas was HD. A blank with no complex present was run simultaneously. No HD was detected. H2/D20Exchange. [CH,C5H4Mo(S)SHl2(0.17 g) was dissolved in 10 mL of THF and 2 mL of D 2 0 . The solution was degassed in two freeze-pumpthaw cycles, and 1 atm of H2 was added at -196 OC. The solution was stirred at room temperature for 5 days. Mass spectrum analysis showed 37% H2, 16% HD, and 47% D2. The mass spectrum of the blank, run simultaneously, showed only H2. The molybdenum complex was recovered by evaporation of the solvent and identified by NMR. The S H ligands were partially substituted by deuterium. Catalytic Hydrogenation of Sulfur. Sublimed sulfur (1.2 g) and [Me,CpMo(S)SH], (0.03-0.05 g) were accurately weighed and were slurried in 50 mL of CHCl, in a 500-mL flask. The solution was degassed in freeze-pumpthaw cycles and l atm H2 was added at -196 OC. The solution was stirred for 24 h at room temperature or in an oil bath. The solvent was evaporated, and the remaining solid was weighed to determine the amount of sulfur consumed. In some cases the product H2S was distilled on a vacuum line and weighed.
Acknowledgment. Support for this work from the donors of the Petroleum Research Fund, administered by the American Chemical Society, from the National Institutes of Health (Grant No. GM-25122), from the National Science Foundation (Grant No. CHE-7922250), and from the University of Colorado Computing Center is gratefully acknowledged. W e thank Professor Robert S e v e r s and M a r k Wizner for assistance in t h e gas chromatographic detection of hydrogen. Supplementary Material Available: Table of observed and calculated structure amplitudes (4 pages). Ordering information is given on any current masthead page.
Protonation Reactions of Molybdenum and Tungsten Dinitrogen Complexes with Halogen Acids. Hydride Hydrazide( 2-) and Diazenido Complexes as Intermediate Stages of Reduction' Tamotsu Takahashi, Yasushi Mizobe, Maki Sato, Yasuzo Uchida, and Masanobu Hidai* Contribution from the Department of Industrial Chemistry, University of Tokyo, Hongo, Tokyo 113, Japan. Received February 12, 1980
Abstract: Reactions of dinitrogen complexes c i ~ - [ M ( N ~ ) ~ ( p M e ~ (PM h )= ~ ]Mo or W) with an excess of HCI in 1,2-dimethoxyethane give hydrazine in moderate yields. This stands in sharp contrast to the formation of ammonia on treatment with H 3 0 4 in methanol. The hydrazido(2-) complex [WBr2(NNH2)(PM@Ph),],which is obtained from ~ i s - [ w ( N ~ ) ~ ( P M q P h ) ~ ] and HBr, reacts with 1 molar equiv of HC1 to afford a hydride hydrazido(2-) complex [WHCIBr(NNH2)(PMe2Ph),]Br. The structure has been definitely determined by infrared and N M R spectra and X-ray analysis. Anion exchange with NaBPh4 in a low yield, in addition to gives a novel diazenido complex [WHCIBr(cN=N(-+BPh3)H)(PMe2Ph)3].CH2C12 [WHC1Br(NNH2)(PMe2Ph)J [BPh4], whose molecular structure has been determined by X-ray analysis. A mechanism for reduction of coordinated dinitrogen is proposed on the basis of these results.
Several systems a r e now known with which the ligating dinitrogen in well-defined complexes is converted into ammonia and However, the detailed hydrazine under mild conditions.2 mechanism for the reduction of dinitrogen in the above systems is not well understood. Its clarification may shed some light on (1) Preparation and Properties of Molybdenum and Tungsten Dinitrogen Complexes. 13. For the previous paper (part 12) in this series, see: Mizobe, Y.; Uchida, Y.; Hidai, M. Bull. Chem. SOC.Jpn. 1980, 53, 1781. (2) Chatt, J.; Dilworth, J. R.; Richards, R.L. Chem. Rev. 1978, 78, 589 and references therein.
the mechanism of nitrogen fixation in biological systems. Recently we have briefly reported that hydrazine is formed in moderate yield on treatment of dinitrogen complexes [M(N2)2(PMe2Ph)4] or hydrazide( 2-) complexes [MBr2(N N H 2 ) (PMe2Ph),] ( M = Mo or W ) with HC1 in 1,2-dimethoxyethane ( D M E ) . j This is in sharp contrast t o the protonation reactions with H2S04in methanol, where ammonia is mainly p r o d ~ c e d . ~ (3) Hidai, M.; Mizobe, Y.; Takahashi, T.;'Uchida, Y. Chem. Lert. 1978, 1187.
0002-7863/80/ 1502-7461 $01 .OO/O 0 1980 American Chemical Society
Takahashi et al.
1462 J . Am. Chem. SOC.,Vol. 102, No. 25, 1980 Table I. Yields of N,H, and NH, complex
[Wcl, (NNH,)(PMe,Ph),
1
[WBr,(NNH,)(PMe,Ph),
1
[WHClBr(NNH,)(PMe,Ph),1 Br
[WHClBr(NNH,)(PMe,Ph),j [ BPh,] [Mo(N,),(PMe,Ph), 1
mmol
solvent
mL
acid
0.318 0.261 0.191 0.194 0.196 0.197 O.18gb 0.188 0.192 0.207
DME MeOH DG THF DME DME MeOH DME DG THF MeOHC DME DG THF MeOHC DME DME MeOH DME DME DME DG THF DME DME MeOH DME DME DME DME
5 4 4 4 4 4 30 4 4 4
HC1 HC1 HC1 HC1 HBr HI %SO, HC1 HC1 HCl H,SO, HCl HC1 HC1
0.232 0.192 0.189 0.186 0.169 0.155 0.156 0.113 0.172 0.258 0.265 0.213 0.214 0.213b 0.267 0.256 0.236 0.211
[MoCl,(NNH,)(PMe,Ph), 1 [MoBr,(NNH,)(PMe,Ph), 1 [W(N,),(dpe), 1 [Mo(N,),(dpe), 1 a Mole oer M atom (M = W or Moh Reference 4. mol/W atbm. e Less than 0.005 mOl/Mo atom
4 4 4
tlh
192 192 116 116 114 116 20 116 116 116 214 116 116
H2S04
4 4 4 4 4 3 5 5 4 4 40 5 5 5 5
HC1 HBr H,SO,d H,SO,d HC1 HCl HC1 HC1 HBr HI H, SO, HC1 HC1 HC1 HC1
24 110 24 24 22 23 20 20 116 116 0.25 24 21 20.5 21
N,H,a
NH,'
0.49 0.33 0.34 0.16 0.16 0.26 0.03 0.50 0.30 0.32 0.12 0.50 0.45 0.34 0.05 0.55 0.29 0.34 0.30 0.53 0.32 0.06 0.04 0.15 0.01 e 0.52 0.48 tr 0.00
0.26 0.64 0.42 0.15 0.34 0.92 1.98 0.47 0.31 0.16 1.26 0.65 0.26 0.29 1.58 0.50 0.34 0.63 0.45 0.32 0.31 0.35 0.33 0.25 0.53 0.64 0.24 0.31 0.00 tr
Chatt. J.: Fakley, M. E.; Richards, R. L. J. Organomet. Chem. 1979,170, C6.
12
In the course of our studies on these protonation reactions, a new trace for M = Mo, as already reported by Chatt and his cocomplex was isolated as an intermediate stage of reduction from w o r k e r ~ . ~They proposed a disproportionation step as in the M '/3N2 2/3NH3for M = Mo since equation M=N-NH2 the reaction of [WBr2(NNH2)(PMe2Ph)3] with 1 molar equiv of the yield of ammonia is essentially 2 mol of ammonia/metal atom HC1 in DME. In a previous comm~nication,~ the complex was for M = W but only ca. 0.66 mol of ammonia/metal atom for tentatively formulated as a hydrazide( I-) complex [WClBrM = Mo. Among halogen acids tested here, HCl is the best for (NHNHz)(PMe2Ph)3]Br. Very recently Chatt and his co-workers6 converting the ligating dinitrogen into hydrazine. Use of HBr also prepared similar tungsten complexes and concluded from the I5NN M R spectra that the hydrogen atom is not bonded to the or H I decreases the yield of hydrazine, while the yield of ammonia nitrogen atom adjacent to the metal. We have now obtained direct is highest in the case of HI. When tetrahydrofuran, diglyme (DG), evidence from 'H N M R spectra that the above complex is coror methanol is used as solvent instead of DME, the yield of rectly formulated as a hydride hydrazido(2-) complex containing hydrazine is lower than that in DME. the MH(NNH2) group. Furthermore, a novel diazenido complex H SO /MeOH was derived from the hydride hydrazido(2-) complex, and its molecular structure has been determined by X-ray structural [M(Nz)z(PMe2Ph),l NH3 NzH, + NH3 analysis. This paper is concerned with the protonation reactions of molybdenum and tungsten dinitrogen complexes with halogen The hydrazido(2-) complexes [MC12(NNH2)(PMe2Ph)3]( M acids, where the mechanism for reduction of dinitrogen will be = Mo or W),' which are isolated from c i ~ - [ M ( N ~ ) ~ ( P M e 2 P h ) ~ l discussed on the basis of structures and chemical properties of and 3 molar equiv of HCl in DME, are treated with an excess several intermediate complexes mentioned above. of HC1 to produce hydrazine and ammonia in similar yields to Reactions of Dinitrogen Complexes with Halogen Acids. Rethose obtained from the parent dinitrogen complexes. Moderate actions of dinitrogen complexes C ~ S - [ M ( N ~ ) ~ ( P M( ~M~ = P ~ ) ~ ]yields of hydrazine (0.52 mol of hydrazine/Mo atom) and amMo or W) with halogen acids HX (X = C1, Br, or I) were carried monia (0.24 mol of ammonia/Mo atom) are given by reaction out in various kinds of solvents, and the yields of ammonia and of [ M O C ~ ~ ( N N H ~ ) ( P Mwith ~ ~ an P ~excess ) ~ ] of HC1 in DME, hydrazine were determined by color tests as shown in Table I. although treatment of the above hydrazido(2-) complex with The tungsten dinitrogen complex reacts more slowly with halogen sulfuric acid in methanol yields only 0.67 mol of ammonia/Mo acids compared with the molybdenum dinitrogen complex. It is atom.2 This finding is incompatible with the view of the disof great interest to note that treatment of the molybdenum and proportionation of the N2H2ligand at the hydrazido(2-) stage tungsten dinitrogen complexes with an excess of HCI gas in DME of the reduction proposed by Chatt et al.4 in the case of molybyields hydrazine in moderate yields. In contrast, when the above denum (vide supra). The results presented here strongly suggest dinitrogen complexes or t r a n ~ - [ M ( N ~ ) ~ ( P M e P(M h ~ )=~Mo ] or that the N N H 2 ligands in both molybdenum and tungsten comW) is treated with H2SO4 in methanol, ammonia is obtained in plexes are, on treatment with halogen acids, further protonated good yields, together with a little hydrazine for M = W and a essentially in a similar way to give hydrazine and ammonia. Hydride Hydrazido(2-) Complexes. An orange-yellow crystalline complex [WHC1Br(NNH2)(PMe2Ph)JBris isolated in (4) Chatt, J.; Pearman, A. J.; Richards, R. L. J . Chem. SOC., Dalton Trans. a good yield when the hydrazido(2-) complex [WBr2(NNH2)1977, 1852.
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+
+
