Organometallics 1983, 2, 562-563
562
atom to form a double bond to carbon. Thus the first-row elements 0 and N can exist in the open form, while the second- and third-row elements S and Se cannot. We suggest that the initial effect of the iron carbonyl is to cause a ring opening by cleavage of the S(Se)-N bond, thus forming the diazoketo form of the ligand possibly stabilized by a metal carbonyl fragment. Given the greater capacity of the second-row S to form a C=S grouping compared to the C=Se group, a longer lifetime might be expected for the ring-opened a-diazo thioketone. This would permit the thioketone to exhibit chemistry more reminiscent of the a-diazo ketones as observed by Herrmann, i.e., imine formation. The selenium analogue would immediately exhibit loss of N2 with resulting carbene formation. The inability to observe thioketoketene complexes is probably related to the more facile decarbonylation of such complexes or, conversely, the inability of thioketocarbenes to insert carbon monoxide. The complete reaction mechanism leading to the formation of 3, and the imine complexes of Herrmann, is unclear. A possibility is the intermediacy of dimerized diazo ketones, i.e. tetrazenes, which are known to eliminate N2 with concurrent formation of amines.14 Acknowledgment. We wish to thank the Robert A. Welch Foundation, Houston, TX, for generous support of this research. Registry No. la, 56382-72-0; lb, 56382-70-8; IC, 38010-76-3; Id, 18212-62-9;le, 40753-16-0;2a, 84642-31-9;2b, 84624-06-6;2d, 84642-32-0; 2e, 84624-07-7; 3a, 84624-08-8; 3b, 84624-09-9; 3c, 84624-10-2;3d, 84624-11-3;3e, 84624-12-4;Fe2(C0)9,15321-51-4; Fe, 7439-89-6. Supplementary Material Available: Tables of interatomic distances and angles, fractional coordinates and thermal parameters, and crystal data and a listing of structure factor amplitudes for 3 (10 pages). Ordering information is given on any current masthead page. (14)Hube, J.; Shine, H. J. A m . Chem. SOC. 1973,95,2501.
Alkane Carbon-Hydrogen Bond Activatlon by Homogeneous Rhodium(I ) Compounds William D. Jones' and Frank J. Feher Department of Chemistty, University of Rochester Rochester, New York 14627 Received November 24, 1982
Summary: The complex [C,(CH,),]Rh[P(CH3),](CH3)CI was prepared by reaction of methyllithium with the corresponding dichloride. Removal of the chloride ligand with Ag' followed by addition of Na+[H2AI(OCH,CH,0CH,)2]at -40 OC produces thermally unstable [C,(CH,),]Rh[P(CH3),](CH3)(H), which undergoes first-order reductive elimination at -17 OC (k = 6.5 X s-'), Irradiation of [C,(CH,),]Rh[P(CH,),] H, in liquid propane at -55 O C produces [C,(CH3),]Rh[P(CH3)3](H)(n-propyl), which can be converted into [C,(CH,)] Rh[P(CH,),] (n -propyl)Br by reaction with CHBr,. 0276-7333/83/2302-0562$01.50/0
I
2
1
t imeihrsl
3
' I
Figure 1. First-order plot of the disappearance of the methyl 'H NMR resonance of 4 at -17 "C in 25% C6D,/75% THF-d,. Scheme I CH,Li
4
3
The activation of carbon-hydrogen bonds for catalysis by transition-metal complexes is an area of rapidly increasing interest.'V2 Recent observations of alkane C-H bond activation have brought into reach even more attractive possibilities for potential substrates.2 We have recently reported the activation of arene C-H bonds by a (permethylcyclopentadieny1)rhodiumcomplex3and now report the activation of alkane C-H bonds by this molecule. Most known transition-metal alkyl hydrides have been reported to be unstable toward facile elimination of R-H.4 The stability of alkyl hydrides of the formula [C5(CH3)5]Rh[P(CH3)3] (R)(H) was initially determined by preparing the methyl derivative 4. A solution of 76 mg of [C5(CH3)5]Rh[P(CH3)3]C12: 1, in 5 mL of THF was treated with 1.1equiv of methyllithium at -40 "C under a nitrogen atmosphere. After the mixture was slowly warmed to 25 "C over a period of 25 min, the solvent was removed (0.01 (1) (a)Green, M. L. H. Pure Appl. Chem. 1978,50,27-35.(b) Rausch, M. D.;Gastinger, R. G.; Gardner, S. A.; Brown, R. K.; Wood, J. S.J.Am. Chem. SOC.1977,99,7870-7876.(c) Grebenik, P.D.; Green, M. L. H.; Izquierdo, A. J . Chem. SOC.,Chem. Commun. 1981,186-187. (d) Gell, K. I.; Schwartz, J. J . Am. Chem. SOC.1981,103,2687-2695.(e) Bradley, M. G.; Roberts, D. A.; Geoffrey, G. L. Ibid. 1981, 103, 379-384. (0 Gustavson, W.A.; Epstein, P. S.; Curtis, M.D.Organometallics 1982,1, 884-885. (g) Diamond, S.E.; Szalkiewicz, A.; Mares, F. J. Am. Chem. SOC. 1979,101,490-491. (h) Horino, H.; Inoue, N. Tetrahedron Lett. 1979, 26, 2403-2406. (i) Fujiwara, Y.;Kawauchi, T.; Taniguchi, H. J. Chem. SOC.,Chem. Commun. 1980,220-221. (2)(a) Janowicz, A. H.; Bergman, R. G. J.Am. Chem. SOC.1982,104, 352. (b) Hoyano, J. K.; Graham, W. A. G. J.Am. Chem. SOC.1982,104, 3723-3725. (c) Crabtree, R. H.; Mellea, M. F.; Mihelcic, J. M.; Quirk, J. M. Ibid. 1982,104,107-113. (d) Baudry, D.;Ephritikhine, M.; Felkin, H. J. Chem. SOC.,Chem. Commun. 1980,1243-1244. (3)Jones, W. D.;Feher, F. J. J.Am. Chem. SOC.1982,104,4240-4242. (4)See, for recent examples: Abis, L.; Sen, A.; Halpern, J. J. Am. Chem. SOC.1978,100,2915-2916.Suggs, J. W. Ibid. 1978,100,640-641. Okrasinski, S. J.; Norton, J. R. Ibid. 1977,99,295-297. Muetterties, E. L.;Watson, P. L.Ibid. 1976,98,4665-4667.Gell, K.I.; Schwartz, J. Ibid. 1978,100, 3246-3248. (5) Isobe, K.; Bailey, P. M.; Maitlis, P. M. J. Chem. SOC.,Dalton Trans. 1981,2003-2008.
0 1983 American Chemical Society
Organometallics 1983,2, 563-565
mm at 25 "C) and the products were chromatographed on silica gel by using 4% THF/CH2C12as eluent. An orange band (R 0.5) was collected and evaporated to yield [C,(CH,),]l$h[P(CH,),](CH,)Cl,2, in 71% isolated yield! Addition of 1 equiv of AgPF6 to a 0.05 M THF-ds/C6D6 solution (73:27) of 2 produces a solution whose lH NMR spectrum (-70 "C)' can be assigned to the complex ([C,(CH,),IRh[P(CH,),I(CH,)(THF-d,)J+(PF,)-, 3. One equivalent of Na+[HzAl(OCH2CH20CH3)z](70% solution in toluene) was then introduced by syringe at -70 "C. When the mixture was warmed to -40 "C, a new species was observed in 80% (NMR) yield. The 'H NMR spectrum of this new compound displays resonances consistent with the formula [C,(CH,),]Rh[P(CH,),] (CH3)(H),84. When the solution was warmed to -17 "C in the probe of the NMR spectrometer, a slow first-order disappearance of the resonances attributable to 4 is observed (k = 6.5 X lo-, 8,Figure 1) with a concomitant increase in resonances attributable to methane (6 0.171) and [C,(CH,),]Rh[P(CH3)3](D)(C6D,),35 (Scheme I). If the same reaction sequence is performed in pure THF-ds, no identifiable products are observed upon warming above -20 "C. The reverse of this reaction, the oxidative addition of alkane to the coordinatively unsaturated rhodium center in [Cs(CH3)5]Rh[P(CH3)3] can therefore only be expected to be observed below -20 "C. Generation of this 16-electron species in an alkane with a boiling point below -20 "C would permit removal of the excess alkane without decomposition of the oxidative-addition product. Accordingly, we chose to irradiate [Cs(CH&]Rh[P(CH3)3]H2,6 6, in liquid propane (bp -40 "C) at -55 OC in an NMR tube attached to a vacuum line. Warming to -40 OC under vacuum (lo4 mm) removed unreacted propane. THF-d8 was then condensed into the tube at -78 OC, the tube sealed, and a 'H NMR spectrum recorded at -40 OC. h i d e from unreacted 6, new resonances appeared at 6 -14.963 (dd, J = 50, 32 Hz, 1 H), 0.840 (t,J = 7 Hz, 3 H), 1.278 (d, J = 9 Hz, 9 H), and 1.820 (d, J = 1.8 Hz, 15 H). The complex is assigned as [C5(CH3)5]Rh[P(CH3)3] (H)(npropyl), 7, on the basis of this spectral datae and from the fact that propane (6 0.892 (t,J = 7 Hz),1.317 (sept, J = 7 Hz)) is produced as a decomposition product when the sample is warmed to -15 OC (eq 1).
563
instantaneous reaction producing a red solution. Removal of solvent (25 "C (10 mm)) followed by addition of CDC1, allows identification of [C,(CH,),]Rh[P(CH,),](npropyl)(Br), 8, by lH NMR and 13CNMR spectroscopy.1° These results demonstrate the oxidative addition and reductive elimination of alkane C-H bonds at a reactive rhodium center. Alkane reductive elimination from 4 occurs at about the same temperature (-17 "C) as reductive elimination of arene from 5 (-10 "C)., The difference in overall stability between 4 and 5 can be attributed to the capability for q2-arene coordination following reductive elimination in 5, whereas reductive elimination of alkane from 4 results in the formation of two distinct species, free to separate in solution. These rhodium complexes are much less stable than the iridium analogues reported by Janowicz and Bergman,2asuggesting that stable oxidative-addition products with alkanes will be found predominantly in the third row. The kinetic and thermodynamic factors influencing alkane vs. arene C-H bond activation are under further investigation. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, and to the Camille and Henry Dreyfus Foundation for support of this research. We also wish to thank Johnson Matthey, Inc., for a generous loan of rhodium trichloride. Note Added in Proof. Prof. Robert G. Bergman and Roy A. Periana-Pillai of the University of California at Berkeley have recently informed us of the isolation of alkyl derivatives similar to 8 in analytically pure form and of similar results with alkane activation. Redotry No. 1,80298-79-9; 2, 84623-98-3; 3, 84624-00-0; 4, 84624-01-1;5, 84624-02-2;6, 84624-03-3;7, 84624-04-4;8, 84624-04-4; Na+[H2Al(OCH2CH20CHa)21-,22722-98-1; CHBrS, 75-25-2. (10)An authentic 6ample of [C,(CHa),JRh[P(CHa)a](n.propyl)(Br) waa prepared by addition of 1 equiv of n-propyllithium to [C&CH&]Rh[P(CH&]Brz at -40 OC in THF. Removal of solvent (26 OC (IO mm)) followed by extraction of the renidue with hexane separates the n-propyl derivative from unreacted starting material and LiBr. Removal of hexane (26OC (IO-' mm)) provider pure 8. For 8: 'H NMR (CDC18)6 1.601 (d, J = 2.6 Hz, 16 H), 1.472 (d, J = 10.1 Hz, 9 H), 0.968 (t, J 7.2Hz, 3 H), 1.20,m, 2 H), 1.86 (m, 2 H); lacNMR (CDCla)6 98.016 (d, J 4.6 Hz, Cb(CHa)b),29.061 (t of d, J 122.6,6.7Hz, CH2CHzCHa),23.183 (t of d of d, J 136.0,22.7,13.6 Hz, CHZCH~CH~), 19.764 (q, J 124.3 Hz, C5(CH&, 16.844 (q Of d, J 126.6,30.2Hz, P(CH&), 9.360(q,J = 127.0 Hz, CH2CHgCH 1. (11) Gill, D. Maitlis, P. M. J. Orgonomet. Chem. 1975,87,369.
--
4.;
Controlled Carbometalatlon,' 15, Zlrconlum-Promoted Carbozlncatlon of Alkynes
H C-C'H
5
7
Additional support for the formulation of 7 as the npropyl derivative arises from its derivatization with a halocarbon. Addition of a five fold excess of CHBr, in THF to the solution containing 7 at -78 OC results in an (6)2 waa further purified by recryetalhtion from CHzC12/hexane:'H NMR (CDCla) 6 1,632(d, J 2.8 Hz, 16 H), 1.413 (d, J 10.2Hz, 9 H), 0.674 (dd, J 7.1,2.2Hz, S H); lacNMR (CDCla) 6 97.322 (8, Cb(CH )a), 14.829 (q of d, J = 129.2,30.6 Hz, P(CH&s), 9.120 (9, J = 127.3 C5(c!&)5),-1.693 (q of d of d, J = 133.4,24.2,16.8 Hz, RhCHJ; mass spectrum (7 eV), (M 16)*. Anal. Calcd for C1,HnClPRh C, 46.11;H, 7.46. Found: C, 46.98;H, 7.49. (7)For 3 'H NMR (-70 "C) 6 1.437 (d, J = 2.7 Hz, 16 H), 1.333 (d, J = 10.2 Hz, 9 H), 0.618 (d, J = 7.6 Hz, 3 H). (8) For 4: 'H NMR (-60 'C) 6 1.790 (d, J = 2.1 Hz, 16 H), 1.178 (d, J 9.6Hz, 9 H), -0.130 (dd, J 6.1,2.6 Hz, 3 H), -14.424 (dd, J 48.3, 30.3 Hz, 1 H). A 10% (NMR) yield of [C,(CH,),]Rh[P(CH,),]Hz is also observed. (9)The methylene groups, being both diasteriotopic and coupled to several nuclei, were not observed directly but are believed to fall partially under the PMea resonances. Irradiation of the 6 1.20-1.46 region causes the triplet at 6 0.840to collapse to a singlet.
kz,
-
El-lchi Neglshl,*t David E. Van Horn, Tadao Yorhlda, and Cynthia L. Rand Departments of Chemlstty, Syracuse Unlverslty Syracuse, New York 13210 and Purdue Unlverslty West Lafayette, Indlana 47907 Recelved September 9, 1982
Summary; The reactlon of alkynes wlth an alkylzlnc derlvatlve and X,ZrCp, (X = I, Br, or CI)can produce the corresponding alkenylzlnc derlvatives 2 in hlgh yields, the stereoseiectivlty and regloselectivity being 198 % and 70-95 % , respectively. The reaction appears to Involve Purdue University. (1) Selective Carbon-Carbon Bond Formation via Transition Metal Catalysis. 31. Part 30 Negishi, E.; Boardman, L. D. Tetrahedron Lett. 1982,23, 3327.
0 1983 American Chemical Society
