Reaction of 1, 3-Butadiene and Allene with a Diosmacyclobutane

Tetsuro Murahashi, Toshiaki Otani, Eiko Mochizuki, Yasushi Kai, and Hideo Kurosawa , Shigeyoshi Sakaki. Journal of the American Chemical Society 1998 ...
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Organometallics 1995, 14, 603-611

603

Reaction of 1,3=Butadieneand Allene with a Diosmacyclobutanet Nikolaos Spetseris, Jack R. Norton,* and Christopher D. Rithner Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523 Received July 14, 1994@

The reaction of the diosmacyclobutane 3 with butadiene gives as a kinetic product the 1,2 adduct Os2(CO)sb-CHzCH(CH=CH2)1 (4); the thermodynamic product is an allyl acyl dinuclear complex O ~ Z ( C O ) ~ ~ ~ - C ( O ) C H ~ - ~ ~ - C (61, H~C derived HCHC from H ~ 4) by CO insertion. Photolysis of Os3(CO)12 in the presence of butadiene gives 6, Os2(C0)701-CH2-r3-CH2CHCH2) (7), and (butadiene)Os(CO)s (8). The structure of 7 has been confirmed by X-ray crystallography: orthorhombic, space group P2121.21, a = 6.928(2) A, b = 9.473(2) A, c = 20.683(4) A, V = 1357.4(6)As, and 2 = 4. The reaction of Na2[Os2(CO)slwith 3,4-dichloro-l-butene or cis-1,4-dichloro-2-butene gave 7 as the principal product. Neither 4 nor 6 rearranged to 7 under thermal conditions, and attempts to carbonylate 7 to 4 or 6 failed at pressures of up to 120 psig. The reaction of 3 with allene gives as a kinetic product the 1,2 adduct Os2(CO)s[u-CH&(=CH2)] (9);the thermodynamic product is O S ~ ( C O ) ~ ~ ~ - ~ ~ - C(10). H~CCH~) Photolysis of Os3(CO)12 in the presence of allene gives 9,10,and (allene)Os(CO)r(11). N e n e is bound more tightly than butadiene to the Osz(C0)s unit. The exclusive formation of 1,2 adducts from both butadiene and allene is explained by the fact that substitution in the diosmacyclobutane system occurs via an intermediate 12 with the olefin coordinated to only one osmium atom.

Introduction Matrix isolation1S2 and transient2 IR spectroscopy studies have shown that Osz(C0)s is formed from the photolysis of the diosmacyclobutane 1 (eq 1).Further-

n

(CO)*Os- Os(CO),

1

COzMe

-

rf -

(2)

[=rCOzMe

(3)

(CO),OS

hv

OS(CO),

co co

"..,,;-Os

o'c

I

,,,...co

I - Ic' o

+

H?C=CHz

(1)

co co

more, the matrix studies have proven that Osz(C0)s does not have the threefold axis that would make it paramagnetic, suggesting that it instead has the Os/ Os double bond shown.' The ethylene is readily displaced from 1by free olefins or acetylenes, particularly those with electron-withdrawing substituents (eqs 2 and 3).394aThe extent to which stereochemistryis retained in these reactions (see eq 414 is surprising when we consider that Os(C0)d is isolobal with CH2: stereochemistry is lost-via a diradical mechanism-when two olefins are formed from cy~lobutane.~ The retention of stereochemistryin eq 4 + Dedicated to Professor Helmut Werner on the occasion of his 60th birthday. Abstract published in Advance ACS Abstracts, December 1,1994. (1) Haynes, A.; Poliakoff, M.; Turner, J. J.; Bender, B. R.; Norton, J. R. J . Organomet. Chem. 1990,383,497. (2)Grevels, F.-W.; Klotzbiicher, W. E.; Seils, F.; SchafFner, K.; Takata, J. J. Am. Chem. SOC. 1990,112,1995. (3)(a) Burke, M. R.; Takats, J. J.Organomet. Chem. 1986,302,C25. (b) Takats, J.Polyhedron 1988,931.(c) Burke, M. R.; Seils, F.; Takats, J. Organometallics 1994,13,1445. (d) Hembre, R.T. Ph.D. Dissertation, Colorado State University, Fort Collins, CO, 1987. (4)(a) Hembre, R. T.; Scott, C. P.; Norton, J. R. J.Am. Chem. SOC. 1987,109,3468.(b) Hembre, R.T.; Ramage, D. L.; Scott, C. P.; Norton, J. R. Organometallics 1994,13,2995. @

(CO),&-

&(CO),

H

trans-1-3,4-d2

Exchange with retention of stereochemistry (4) (stereochemicalexcess > 99.1 "10)

is reminiscent of that found in concerted reactions such as Diels-Alder and 1,3-dipolar cycloaddition^.^,^ Evidence for a dimetalla-Diels-Alder reaction involving a metal-metal double bond has been reported by Hersh and Bergman.s The benzodicobaltacyclohexene ( 5 ) (a) Chickos, J. S.;Annamalai,A.; Keiderling, T. A. J.Am. Chem. SOC. 1986,108,4398. (b) Chickos, J. S. J. Org. Chem. 1979,44,780. (6)For Diels-Alder reactions, see: Houk, K. N.; Lin, Y.; Brown, F. K.J. Am. Chem. SOC.1986,108,554. (7)For 1,3 dipolar cycloaddition reactions, see: (a) Bihlmaier, W.; Geittner, J.; Huisgen, R.; Reissig, H. U. Heterocycles 1978,10, 147. (b) Houk,K. N.; Firestone, R. A.; Munchausen, L. L.; Mueller, P. H.; 1985,107,7227. h i s o n , B. H.; Garcia, L. A. J. Am. Chem. SOC. (8)(a) Theopold, K. H.; Hersh, W. H.; Bergman, R. G. Isr. J. Chem. 1982,22, 27. (b) Hersh, W.H.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc. 1983,105,5834.(c) Hersh, W. H.; Bergman, R. G. J. Am. Chem. SOC. 1983,105,5846.

0276-733319512314-0603$09.00/00 1995 American Chemical Society

604 Organometallics, Vol. 14, No. 2, 1995

2 reversibly forms o-xylylene and a dinuclear complex that contains a cobaltkobalt double bond (eq 5).

We have therefore examined the reaction of diosmacyclobutanes with various dienes. A convenient diosmacyclobutane has been the propylene adduct 3,l knowng t o be more reactive than 1. In particular, we wanted to see whether butadiene would give 4 (the formal product of [2 21 addition to the double bond of Osz(C0)8) or 5 (the formal product of [4 21 addition) (eq 6).

+

+

I *+"

(CO),d

-4

OS(CO),

(co),Os-

dS(CO),

5

A 1,2 adduct has already been reported by Takats and co-workers from the reaction between 1 and an activated diene (eq 7).3bJ0

Experimental Section Reactions and manipulations were performed using standard Schlenk techniques, under an atmosphere of nitrogen purified by passa e through BTS catalyst (BASF) and molecular sieves (3 Linde). Chromatography was performed on a Chromatotron (Harrison Research Inc.) with silica gel as the adsorbent. lH NMR spectra were recorded at 300 MHz and 13Cspectra at 75.5 MHz on a Bruker AC-300P spectrometer. NMR simulations were performed with the Bruker-supplied program PANIC (Parameter Adjustment in NMR by Iterative Calculation) on an Aspect 3000 computer. Phase-sensitive homonuclear double quantum filtered COSY spectra were acquired (256 increments of 512 points each) with the standard Bruker software COSWHDQ. The sweep widths were 1800 Hz in t z and 900 Hz in t l . Cosine weighting and zero filling were applied to both domains prior to Fourier transformation. The final resolution was about 3.5 Hidpoint in FZ and 7 Hdpoint in F1. Carbon-hydrogen correlated spectra were acquired (64 increments of 1024 points each) with the standard Bruker

1

(9)(a) Bender, B. R.; Ramage, D. L.; Norton, J. R.; Wiser, D. C.; Rapp6, A. K., manuscript in preparation. (b) Ramage, D. L.; Wiser, D. C.; Norton, J. R., manuscript in preparation. (10)X-ray crystallography has established a different structure (the result of nucleophilic attack on a carbonyl ligand) for the 1,2 adduct previously reported3bas the product of the reaction between 1 and a diazadiene: Takats, J., personal communication.

Spetseris et al. software XHDEPTW. The sweep widths were 10 416 Hz in t z and 900 Hz in tl. Cosine weighting and zero filling were applied to both domains prior to Fourier transformation. The final resolution was about 10 Hdpoint in Fz (I3C)and 7 H d point in F1 (lH). Phase-sensitive proton-detected ("inverse-mode")hydrogencarbon correlated spectra were acquired (128 increments of 1024 points each) with the standard Bruker software BIRDDP9. The sweep widths were 16 000 Hz in t z and 2000 Hz in t l . A BIRD pulse was used t o suppress IH-W magnetization. Garp-64 broad-band decoupling was applied to 13Cduring 'H detection. Cosine weighting and zero filling were applied to both domains prior to Fourier transformation. The final resolution was about 125 Hdpoint in FZ(13C)and 2 Hdpoint in F1 (lH). Difference nuclear Overhauser enhancement (NOE) experiments were acquired by using the standard Bruker pulse program, NOEMULT. This experiment rapidly hops the irradiation frequency across the multiplet being saturated and thus requires less power and produces fewer anomalies." IR spectra were recorded on a Perkin-Elmer 983 spectrophotometer. Mass spectra were obtained on a VG 7070 EQHF mass spectrometer. Elemental analyses were performed by Midwest Microlab. Pentane was purchased from Aldrich and was purified by stirring over concentrated HzS04, passage through a 20 x 3 cm column of alumina, and distillation from Na/benzophenone/ tetraglyme. Dichloromethane and THF were distilled from P4010and Nahenzophenone, respectively. Dichloromethanedz and W O were purchased from Cambridge Isotopes. CDZClz was dried by vacuum distillation from P4010. O S ~ ( C O 13C-enriched ) ~ ~ , ~ ~ O S ~ ( C O (CzH4)0sz(CO)s )~~,~~ (l),I4 (CH~CHCHZ)OS~(CO)B (3),lN a ~ O s ( C 0 ) 4and , ~ ~Naz0sz(C0)8l6 were prepared by literature procedures. Photolyses were performed by a modification of the proceThe dures used for the preparation of diosmacy~lobutanes.~~~-~ output of a high pressure 450-W Hanovia lamp was passed through a saturated aqueous solution of NaNOz so that only light with 1 > 435 nm remained. Preparation of (C4H6)Os2(CO)8(4) and (C(O)C&)(6)from (CI&CHCHZ)OS~(CO)~ (3)and ButadiOSZ(CO), ene. In a Fischer-Porter pressure vessel was dissolved 100 mg (0.15 mmol) of 3 in 20 mL of pentane. The vessel was initially charged with 30 psig butadiene, then vented, and charged three times with butadiene t o displace the dissolved air; it was wrapped in aluminum foil to preclude photochemical reactions. The reaction mixture was stirred at room temperature under 30 psig of butadiene; every h it was vented and recharged with butadiene in order t o remove the propylene released. IR showed the reaction t o be complete after 8-10 h. The colorless homogeneous solution was transferred by cannula under pressure of butadiene into a Schlenk flask (11)Neuhaus, D. J . Magn. Reson. 1983,53, 109. (12)Johnson, B. F. G.; Lewis, J.; Kilty, P. A. J . Chem. SOC. A 1968, 2859. (13)Cetini, G.; Gambino, 0.;Sappa, E.; Vaglio, E. G . A. Atti Accad. Sci. Torino 1967,101,855. (14)(a)Motyl, K.M.; Norton, J. R.; Schauer, C. K.; Anderson, 0. P. J.Am. Chem. SOC. 1982,104,7325. (b) Anderson, 0.P.; Bender, B. R.; Norton, J. R.; Vergamini, P. J.;Larson, A.C. Organometallics 1991, 10,3145. (c) Burke, M.R.; Takats, J.; Grevels, F.-W.; Reuvers, J. G. A. J . Am. Chem. SOC.1983,105,4092. (d) Poe, A.J.; Sekhar, C. V. J . Am. Chem. SOC.1986,108,3673. (15)(a)Fischer, W.; Hembre, R. T.; Sidler, D. R.; Norton, J. R. Inorg. Chim. Acta 1992,198-200, 57. (b) Carter, W. J.; Kelland, W. J.; Okrasinski, S. J.; Warner, K. E.; Norton, J . R. Znorg. Chem. 1982,21, 3955,and references therein. (16)(a)Hembre, R. T. Ph.D. Dissertation, Colorado State University, Fort Collins, CO, 1985. (b) Bhattacharyya, N. K.; Coffy, T. J.; Quintana, W.; Salupo, T. A,; Bricker, J. C.; Shay, T. B.; Payne, M.; Shore, S. Organometallics 1990,9, 2368. (c) Bender, B. R. Ph.D. Dissertation, Colorado State University, Fort Collins, CO, 1990. (d) Anson, C. E.; Sheppard, N.; Powell, D. B.; Norton, J. R.; Fischer, W.; Keiter, R. L.; Johnson, B. F. G.; Lewis, J.; B h a t t a c h q a , A. K.; Knox, S. A. R.; Turner, M. L. J . Am. Chem. SOC. 1994,116, 3058.

Diosmacyclobutane Reaction with Butadiene and Allene precooled to -80 "C. Solvent removal under vacuum at -80 "C gave a white-yellow solid. After vacuum transfer of CDzClz and warming to -40 "C, the resulting solution was added to an N M R tube precooled t o -40 "C; the tube was then sealed in vacuo. Both lH and 13CNMR suggested that two compounds were present in a 2:l ratio. The 'H and 13C peaks due to each compound were identified by lH-'H decoupling, COSY, and W-lH correlated spectra. The attribution of one set of peaks to 6 was confirmed after its independent photochemical synthesis (next section). For c4H6osZ(co)S(41, 'H NMR (CDzClZ): 6 1.54 (dd, lH, 'Jgem= -10.4 Hz, 3Jtrma= 12.8 Hz), 1.83 (dd, lH, 'Jgem= 10.4 Hz, 3Jcia = 6.7 Hz), 2.62 (m, lH, 3Jtrma = 12.8 Hz, 3Jcia = 6.7 Hz, 3 J = 6.8 Hz, 4 J = 1.6 Hz, 4 J = 1.6 Hz), 4.23 (ddd, lH, 3Jda = 10.2 Hz, 'Jgem= -1.6 Hz, 4 J = 1.6 Hz), 4.47 (ddd, lH, 3Jt,ma = 17.0 Hz, 'Jgem= -1.6 Hz, 4J = 1.6 Hz), 5.87 (ddd, lH, 3Jtrma = 17.0 Hz, 3Jda= 10.2 Hz, 3J = 6.8 Hz). "C N M R (CDzClz): 6 -21.0 (CHz, JCH= 134 Hz, 'JCH= 5.5 Hz), 1.0 (CH, JCH= 140 Hz), 102.0 (CHz, JCH= 155 Hz, 'JCH= 5.7 Hz), 155.0 (CH, JCH= 150 Hz), 168.8(CO), 169.4 (CO),172.0 (CO), 172.5(CO), 179.9 (2CO), 181.4(CO), 181.5 (CO). IR (pentane): 2120.0 (w), 2080.0 (vs), 2040.0 (s), 2031.0 (s), 2010.0 (s), 1993.0 (m) cm-l. For (c(o)c~~)os2(co)~ (61,IH NMR (CDzC12): 6 2.41 (m, 3H, COCHH, CH=CHH), 3.58 (ddd, lH, CH=CHH, J m = 7.7 Hz, J m = 6.9 Hz, J m = 3.5 Hz), 4.18 (m, 2H, COCHHCHCH). NMR (CDzClz): 6 25.9 (CHz, JCH= 161 Hz), 49.0 (CH, JCH = 161 Hz), 70.0 (CHz, JCH= 128 Hz), 93.0 (CH, JCH= 159 Hz), 164.9 (CO), 172.4 (CO), 183.9 (CO), 186.2 (CO), 186.7 (CO), 187.2 (CO), 187.7 (CO), 218.0 (COC.&). IR (CHzClz): 2115.5 (m), 2097.5 (w), 2072.5 (w), 2068.0 (m), 2055.5 (s), 2025.0 (vs), 1980.0 (s), 1625.1 (w) cm-l. Its mass spectrum showed a parent ion peak at mle 662 (lg20s) with the appropriate isotopic distribution.

Preparation of C&Osa(CO)8 (4), (C(O)C&)OSZ(CO)~ (6), C&OSZ(CO)~ (7), and (C&)Os(CO)s (8) by the Photochemical Fragmentation of Os&O)12. Os3(CO)12 (300 mg, 0.33 mmol) was suspended in 300 mL of CHzClz in a Fischer-Porter pressure vessel. The vessel was then charged and vented three times with 30 psig of butadiene in order to displace the dissolved air. The yellow heterogeneous solution became colorless and homogeneous after photolysis under 30 psig of butadiene for 10 h with visible light (A > 435 nm). All but 1mL of the solvent was removed under vacuum at 0 "C, and the mixture was applied to a Chromatotron plate. Elution with pentane, under a flow of Nz cooled by passage through copper tubing immersed in liquid Nz, gave the new compound 7 (62 mg, 30% yield) and the known (65 mg, 60% yield); solvent was removed under vacuum at 0 "C to avoid decomposition. Further elution under the same conditions with a 1:l mixture of diethyl ether and pentane gave 6 and a small quantity of 4 (combined Rf 0.20) in a combined yield of 25% (54 mg); again, solvent was removed under vacuum at 0 "C to avoid decomposition. For c ~ ~ o ~ ~ (71, ( c 'Ho )NMR 7 (CDzC12): 6 0.39 (dd, lH, 'Jgem= -7.9 Hz, 3 J = 8.4 Hz), 1.65 (dd, lH, 3 J = 8.7 Hz, 'Jgem = -7.9 Hz), 1.75 (dd, lH, 'Jgem= -4.1 Hz, 3Jtrw = 10.3 Hz), 2.52 (m, lH, = -4.1 Hz, 3J"a= 6.6 Hz), 4.37 (m,lH, 3Jci, = 6.6 Hz, 3Jda= 7.0 Hz, 3Jtr, = 10.3 Hz), 5.43 (m, lH, 3Jda= 7.0 Hz, 3 J m = 8.7 Hz, ' J m = 8.4 Hz). lacNMR (CD2Clz): 6 -11.5 (CHz, JCH= 139 Hz), 18.0 (CHz, JCH= 155 Hz), 73.6 (CH, JCH= 163 Hz),78.7 (CH, JCH= 171 Hz). IR (pentane): 2106.0 (w), 2048.0 (vs), 2029.0 (s), 2020.0 (vs), 2003.0 (81, 1980.5 (m), 1973.0 (m) cm-l. Its mass spectrum showed a parent ion peak at mle 634 (1g20s) with the appropriate isotopic distribution. Anal. Calcd for C1&07082: C, 20.96; H, 0.96. Found: C, 21.03; H, 1.06. W-Enriched 6 (6.) was synthesizedfrom lac-enriched0 8 3 (CO)12;13 the laccontent of the latter was 16.5% (analysis, by (17)Zobl-Ruh, S.; von Philipsborn, W. Helu. Chim. Acta 1980, 63, 773.

Organometallics, Vol. 14,No. 2, 1995 605 overdetermined-least-squaresmethods, of the observed parent ion multiplet vs the isotopic distribution calculated for Osa-program MASSPEC). Photochemical fragmentation in the presence of butadiene according to the previous procedure gave 6*, with lacNMR (CDzCld 6 69.9 (CHZ,JCC= 24.8 Hz). Preparation of C&Ost(CO)7 (7) from the Reaction of NazOsa(CO)e with Dichlorobutenes. In a typical experiment, NazOsz(C0)s was prepared in situ by titrating (Cz&)Os~(C0)s (1; 200 mg, 0.32 mmol) with a standard solution of Na/PhzC=O in THF [2.0 g (87 mmol) of Na, and 1.0 g (5.6 mmol) of Ph&=O, in 40 mL of THF] until a purple color persisted.lecVdSubsequentlycis-1,4-dichloro-2-butene (0.33mL, 3.2 mmo1,lO equiv) was added dropwise. The solution turned orange, and a white precipitate formed. After filtration through silica, the homogeneous solution was chromatographed with pentane as the eluant. The most intense band (Rf0.60)contained (after solvent removal at 0 "C) 50 mg (0.08 mmol, 25% yield) of 7. Low yields of several other bands were observed but not identified. Treatment of NazOsz(C0)S with 3,4-dichloro-l-butenein the same fashion gave 7 in 20% yield; trans-1,4-dichloro-2-butene gave 7 in 22% yield. Preparation of CJ&Osa(CO)s (9) and CJ&Os2(CO)7 (10) from (CH.~CHCH~)OS~(CO)~ (3) and Allene. As in the butadiene reaction above, 3 (100 mg, 0.15 mmol) was dissolved in 20 mL of pentane. The vessel was initially charged with 40 psig of allene, then vented, and charged three times with allene to displace the dissolved air, it was wrapped in aluminum foil to preclude photochemical reactions. The reaction mixture was stirred at room temperature under 40 psig of allene; every h it was vented and recharged with allene in order to remove the propylene released. After 8-10 h the reaction contained a 9:l mixture of 9 and 10. 9 is thermally unstable and was characterized in solution. lH NMR (CDzClz): 6 2.09 (dd, 2H, 4 J m = 1.7 Hz, 4 J m = 1.6 Hz) 4.62 (dt, lH, 4 J m = 1.6 Hz, 'Jgem= -2.4 Hz), 5.73 (dt, lH, 4 J m = 1.7 Hz, 'Jgem= -2.4 Hz). lacNMR (CDzClZ): 6 -11.90 (CHz, JCH = 136 Hz, 3 J c = ~ 8.5 Hz, 3 J c = ~ 14.5 Hz), 115.6 (CHz, JCH= 154 Hz, 3 J c ~ 5.7 Hz), 124.1 (=C=), 167.6 (CO), 168.9 (CO), 172.4 (CO), 173.6 (2CO), 180.4 (CO), 180.7 (2CO's). IR (pentane): 2126.5 (w), 2084.0 (s), 2044.0 (s), 2039.0 (s), 2027.5 (m), 2014.5 (m), 1999.0 (m), 1987.5 (w) cm-l. Its mass spectrum showed a parent ion peak at mle 648 (lg20s)with the appropriate isotopic distribution. When the reaction was allowed to proceed for an additional 10 h, only 10-a white crystalline material that is air and temperature stable-was isolated. 10 was first synthesized by Deeming and co-workers, and characterized by IH NMR, IR, and mass spectrometry.ls NMR (CDzClz): 6 52.9 (CHZ, JCH= 157 Hz, 3 J c = ~ 7.2 Hz, 3 J c = ~ 12.8 Hz), 146.4 (=c=), 167.3 (CO), 175.4 (CO), 176.7 (CO), 179.3 (~CO'S), 180.8 (2CO). Equilibrium Constant Measurements for 3 Butadiene and 3 Allene. A sample of 3 (20 mg, 0.031 mmol) was placed in an NMR tube, and 181 Torr (0.046 mmol) of butadiene and 0.5 mL of dry CDzClz were condensed onto it. The mixture was warmed t o 0 "C, and the reaction followed by lH NMR for 72 h. The reaction between 3 and allene was monitored in the same way. Preparationof C S I ~ O S ~ ( C (10) O ) ~and q2-CJ&0s(C0)4 (11)by the Photochemical Fragmentation of OSS(CO)IZ in the Presence of Nene. By the procedure described above for the butadiene case, Os3(CO)12 (300 mg, 0.33 mmol) was photolyzed under 40 psig of allene. Compounds 10 (Rf 0.6) and 11(Rf0.7) were separated by elution with pentane on a chromatotron. Solvent-free 10 (69 mg, 0.13 mmol, 40% yield) was obtained as a white solid by solvent removal at 0 "C. Solvent-free11was obtained by high-vacuum fractionation. After freeze-pump-thaw degassing, the pentane solution (0 "C) containing 11 was fractionated under dynamic vacuum (10-4 mmHg) by slowly passing it through two U-traps in

+

+

(18)Bates, P. A.; Hursthouse, M. B.; h c e , A. J.; Sanctis, Y. D.; Deeming, A. J. J . Chem. Soc., Dalton Trans. 1987,2935.

Spetseris et al.

606 Organometallics, Vol. 14, No. 2, 1995

Table 1. Summap of Cwstal Data for 7 formula temperature ("C) crystal size (mm) space group a (A)

b (A) c

(A)

diffractometer radiation wavelength (A) index ranges 28 range no. of reflcns collected no. of obsd reflcns no. of parameters p

("-1)

absorption correction RF (%I R ~ (%IF

CllH6070S2 - 105 0.40 x 0.30 x 0.15 p212121 6.928(2) 9.473(2) 20.683(4) Siemens P3 Mo Ka,graphite monochromator 0.710 73 0 5 h 5 10,O 5 k 5 14,O 5 15 31 4.0-65" 2819 2274 (F > 6.0u(F)) 92 18.7 semiempirical 6.22 7.43

series, the first at -40 "C (CH3CNAiquid Nz slush) and the second at -196 "C. Pure 11 was obtained after 12 h as clear, colorless crystals (62 mg, 0.18 mmol, 55%yield) in the -40 "C trap. The colorless oily 11 yellows upon standing at room temperature, but is stable indefinitely when stored at -20 "C. 'H NMR (CD2CL2): 6 1.79 (t,2H, 4 J =~3.00 Hz), 5.56 (t, lH, 4 J= ~ 3.13 Hz), 6.76 (t, lH, 4 J =~2.91 Hz). I3C NMR (CD2c12): 6 -10.9 (C&, JCH= 160 Hz, 3 J c = ~ 3.1 Hz, 3 J c = ~ 9.9 = 160 Hz, 3 J C H = 3.7 Hz), 143.2 (=C=). Hz), 109.5 (CH2, JCH 13C NMR (CDZC12, -40 "C): -11.6 (CHz), 109.1 (CHz), 142.9 (=C=), 175.8 (2CO), 176.7 (CO), 177.9 (CO). IR (pentane): 2119.5 (m), 2036.5 (vs), 2000.5 (s), 1697.0 (w) cm-'. Its mass spectrum showed a parent ion peak at mle 344 (lg20s)with the appropriate isotopic distribution. X-ray Determination of the Structure of 7. Complex 7 crystallized from pentane by slow cooling to -80 "C. Single crystal X-ray data were collected at -105 "C using a pale yellow crystal of dimensions 0.40 x 0.30 x 0.15 mm on a Siemens R3mN dieactometer equipped with a molybdenum tube [I(Kal) = 0.709 26 A; I(Ka2 = 0.713 54AI and a graphite monochromator. The compound crystallized in the chiral orthorhombic space group P212121 with four molecules in a cell of dimensions a = 6.928(2)A, b = 9.473(2)A, c = 20.683(4)A, and V = 1357.4(6)A3. A total of 2819 independent reflections were gathered, the octants collected being +h,+k,+Z, using the Wyckoff scan method. Three standard reflections were measured after every 100 reflections collected. The structure was solved by direct methods and refined by full-matrix leastsquares techniques using structure solution programs from the SHELXTL system.l9 The two osmium atoms were refined anisotropically, while other nonhydrogen atoms were refined isotropically due to large residual electron densities near the heavy atoms. Hydrogen atoms were placed in fured calculated positions (C-H = 0.96 A). The structure has been refined to conventional R factor values of R = 0.0622 and R, = 0.0743 on the basis of 2274 observed reflections with I > 3dI) in the 20 range 4-65" ( R = 0.0761, R, = 0.0782 for all data), giving a data to parameter ratio of 25:l. Despite the use of both semiempirical and empirical2O absorption correction techniques, several large peaks in the Fourier remained near the osmium atoms, the maximum and minimum residual densities being 8.55and -3.57 e A-3, respectively, withp = 18.7 mm-l. The results of absolute configuration tests were inconclusive. The details of the crystal data as well as the atomic coordinates for 7 are given in Tables 1 and 2.

Results and Discussion Reaction of (CH&HCH~)OS~(CO)~ (3) with 1,3Butadiene. A solution of 3 was stirred under butadi(19) Sheldrick, G. M. SHELXTL Crystallographic System, Version 4.Mris; Siemens Analytical X-ray Insts. Inc., Madison, WI, 1991. (20) Hope, H.; Moezzi, B. W S ;Chemistry Department, University of California, Davis, CA, 1987.

Table 2. Atomic Coordinates ( x 104) and Equivalent Isotropic Displacement Coefficients x 103) for 7 ~

X

1115(1) 2193(1) 3488(33) 4 101(35) 4307(32) 4836(34) -384(31) - 1312(27) 437(35) -1 ll(32) -624(37) - 1724(25) 1979(35) 1935(30) 2489(31) 2608(29) 3531(33) 4323(26) -355(30) -1843(25)

~~

~~

~

~

Y

Z

Ueq)

6437(1) 3484(1) 7 170(23) 7267(24) 6028(21) 4623(24) 5809(21) 5413(20) 8335(24) 9489(24) 6010(23) 5782(18) 327 l(26) 3204(22) 3957(20) 4180( 18) 1724(22) 671(17) 2773(20) 2342(18)

8779(1) 8681(1) 8122(10) 8782(10) 9170(10) 8917(11) 9500(9) 9927(8) 8918(10) 9038(10) 8118(11) 7699(8) 9625( 11) 10164(9) 7758(9) 7225(8) 8613(10) 8555(8) 8514(9) 838 l(8)

W) 14U) 20(4) 25(4) 17(4) 24(4) 30(4) 24(4) 47(5) 23(4) 26(4) 26(5) 380) W4) 29(4) 21(4) 26(3) W3) 26(4)

ene at room temperature, with repeated venting in order to remove the propylene released. Two products were formed in an initial ratio of 2:l (eq 8). The major product

(CO)40s-Os(CO)4

4

+

+

(CO)40s-Os(CO)3

6

+

2

(8)

was the [2 21 adduct 4 (see below), with no evidence of the Diels-Alder product 5; the minor product proved to be a dinuclear allyl acyl complex (6). IR and lH NMR showed no intermediates. 4 is unstable above -40 "C in the absence of butadiene but has been characterized by low-temperature NMR techniques as part of a mixture with 6. The inverse detected (BIRDDPS)13C-lH correlated 2D NMR spectra of 4 and 6 shown in Figure 1 permitted the assignment of lH and 13C NMR resonances t o both 4 and 6. The lH NMR spectrum of 4 displays the six different chemical shifts-three in the olefinic region-expected for its unsymmetrical structure. (The diosmacyclohexene 5, with CzVsymmetry, would show only two proton chemical shifts.) The 13CN M R spectrum of 4 shows four signals due to the butadiene ligand: two come from carbons a-bonded t o osmium and have JCH values characteristic of sp3carbons in a diosmacyclobutanering (JCHin 1 is 135 H z ~ ~two ~ ) ;plainly arise from sp2 carbons in an uncoordinated double bond. The number of 13C NMR carbonyl signals (eight) and the IR of 4 plainly establish that it is dinuclear. 6 is unstable above 0 "C in the absence of butadiene but can be obtained pure from the photolysis of Os3(CO)12 and butadiene (see below). Its 13C NMR spectrum shows evidence for an allyl ligand (three signals belong-

Organometallics, Vol.14,No. 2, 1995 607

Diosmacyclobutane Reaction uith Butadiene and Allene

I ~ " ' " ~ ' " " ' " ' ~ " I ~ ~

71.0

70.0

69.0

PPM

I

160.0

r2b.O

8d.O

40.0

02

(ppm)

0.0

-40.0

Figure 1. Inverse detected (BIRDDPS)13C-lH correlated 2D NMR spectrum of 4 and 6. *tl noise. ing to sp2 carbons),21as well as a signal belonging to an sp3 methylene that, a t 6 70,is too far downfield to be a-bonded to an osmium. Another 13CNMR peak, at 6 218,can be assigned to an acyl carbon; the IR shows a peak at 1628 cm-l. (Carbonyl stretches at 1634 and 1648 cm-l have been observed22in other diosmium acyl complexes.) The possibility that 6 was an acyl isomer of 4 has been tested by determining lJcc between the acyl and methylene carbons. When a sample of Os3(CO)12with 16.5% 13C0 is converted into 6* by photolysis with butadiene (see below), its 13C NMR signal at 6 70.0 (C2)shows satellites with a JCC of 24.8Hz (Figure 2). The methylene must thus be bonded to the acyl carb0n,2~and 6 must have the structure Interconversion of 4 and 6. When a 2:l mixture of 4 and 6 (as initially formed from 3 and butadiene) was kept a t 0 "C for 10 h in the presence of excess butadiene, much of 4 isomerized t o 6. The composition (21) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic Compounds; Academic: New York, 1981; pp 200-210. (22) Bullock, R. M.; Hembre, R. T.; Norton, J. R. J.Am. Chem. SOC. 1988,110, 7868. (23) 'JCCbetween a n organic carbonyl carbon and the carbon of an sp3 substituent is about 40 Hz: Kalinowski, H. 0.; Berger, S.; Braun, S. '3C-NMR-Spectroskopi;Georg Thieme Verlag: Stuttgart, Germany, 1984; p 501. (24) The sp3 CH2 of 6 is shifted downfield (6 70) by the carbonyl ~ o u u Comuare . the effect of CO and Os on su3 carbons in the followine

Figure 2. sp3methylene region of the 13CNMR spectrum (75.5 MHz, CDzC12) of 6*. The singlet is due to the 83.5% of the molecules that are unlabeled, while the doublet (JCC = 24.8 Hz) is due to the 16.5% of the molecules that are labeled.

of the equilibrium mixture implied Keq = 8.9 a t 0 "C (eq 9). The kinetic product of the reaction of 3 with butadiene is thus 4, while the thermodynamic one is 6.

K,, = 8.9 (CO),Os-

4

OS(CO),

0

OOC, CD2C12

*

-

(co)40s OS(CO):, 6

(9)

-

The facile conversion of 4 6 finds precedent in the recently reported rearrangement of CpRe(CO)2(q1-allyl)The lat(CHMe2)to CpRe(CO)(g3-allyl)(C(0)CHMe2).25 ter involves "isopropyl migration to CO concerted with ql- to q3-allyl rearrangement". We know of no precedent for the structure of 4 or the structure of 6 in the dinuclear coordination chemistry (25) Casey, C. P.; Vosejpka, P. C.; Underiner, T. L.; Slough, G. A.; Gamey, J. A,, Jr. J . Am. Chem. SOC.1993,115, 6680. (26) (a) Kriiger, C.; Miiller, G.; Erker, G. Mu.Organomet. Chem. 1985,24, 1. (b) Kreiter, C. G. Mu.Organomet. Chem. l986,25, 297. (c) Ziegler, M. 2.Anorg. Allg. Chem. 1967,355, 12. (d) Adams, V. C.; Jarvis, J. A. J.;Kilbourne, B. T.; Owston, P. G. J. Chem. Soc. D 1971, 467. (e) Tachikawa, M.; Shapley, J. R.; Haltiwanger, R. C.; Pierpont, C. G. J.Am. Chem. SOC.1976,98,4651. (0Franzreb, IC-H.; Kreiter, C. G. 2.Naturforsch. 1982,37B, 1058. (g) Kreiter, C. G.; Lipps, W. Chem. Ber. 1982, 115, 973. (h) Franzreb, K-H.; Kreiter, C. G. J . Organomet. Chem. 1983, 246, 189. (i) Vollhardt, K P.; King, J. A., Jr. Organometallics 1983,2,684. (i) Fryzuk, M. D.; Jones, T.; Einstein, F. W. B. J. Chem. SOC.,Chem. Commun. 1984, 1556. (k) Fryzuk, M. D.; Piers, W. E.; Rettig, S. J. J. Am. Chem. Soc. 1986, 107, 8259. (1) Lewandos, G. S.; %ox, S. A. R.; Orpen, G. A. J. Chem. SOC.,Dalton Trans. 1987, 2703. (m) Wedt, G.; Kaub, J.; Kreiter, C. G. Chem. Ber. 1989, 122, 215. (n) Meszaros, M. W.; Gohdes, M. A.; Casey, C. P. Organometallics 1988,7,2103. (0)Fryzuk,M. D.; Piers, W. E.; Rettig, S. J.; Einstein, F. W. B.; Jones, T.; Albright, T. A. J.Am. Chem. SOC. 1989, 111, 5709. (p) Erker, G.; Noe, R.; Kriiger, C.; Werner, S. Organometallics 1992, 11, 4174.

Spetseris et al.

608 Organometallics, Vol. 14, No. 2, 1995

N

M M

M-M

M-M

b

a

C

M

hi-M

Figure 4. Molecular structure of Osz(C0),(u-CH2-r3-CH2CHCH2) (7).

\H/ g

Figure 3. Most common bridging geometries for butadiene: a,24a,b,i b,24a,b,e,f ,.,24a,b-d d 24a,b,g e,24a,b,k f,24a,bj and g.24a,b,h,l1o

of butadiene itself. (Earlier results from Takats and coworkers, eq 7, gave a [2 21 adduct, but involved an activated diene.3b) Figure 3 shows the most common bridging geometries for butadiene.26 It can have either the seis or s-trans conformation while bridging a metal-metal bond (a, b); it can bridge two noninteracting metals (c-e); it can bridge after C-H activation (f, g). Photochemical Reaction of OSS(CO)IZwith Butadiene. The photolysis of Os3(CO)12 with long-wavelength light (A > 370 nm) in the presence of olefins has proven to be an efficient way of making mono- and diosmium olefin c o m p l e ~ e s . l ~We ~ - ~thus photolyzed Os3(CO)12 in the presence of butadiene in order to compare the resulting dinuclear complexes (eq 10)with those from the thermal reaction (eq 8).

+

m oS(CO)3 + (CQ4&8

bs(C0)3 +

7

0

with a similar structure, W2(0CH2-tBu)s(py)(C4Hs) reported by Chisholm and c o - w o r k e r ~ .The ~ ~ butadiene ligands in 7 and in the tungsten compound differ in only one way: C4 in 7 is a-bonded to only one osmium, whereas the corresponding methylene carbon in the tungsten analog bridges both metals. Perhaps as a result, JCHof C4 in 7 is 139 Hz to both protons, whereas JCH is different for the two C-H bonds within the methylene in the tungsten compound (149 Hz t o one proton and 124 to the other).

fw=w i Reaction of Na2Os2(CO)swith Dichlorobutenes. In an attempt to independently synthesize 4 and perhaps 5 (eq 111, NazOsa(C0)s was treated with 3,4respecdichloro-1-buteneand cis-1,4-dichloro-2-butene, tively.

-,* K

r f = (co)40s- Os(CO), 4

€3

(co)40s-OS(CO):, (10) 6

The principal product (60%) was the knownl7 monoosmium butadiene complex 8. However, substantial amounts of both 6 (20%) and a new dinuclear complex, 7 (30%),were also formed. 7 is not a secondary photoproduct: irradiation of an equilibrium mixture of 4 and 6 (from the thermal reaction) with butadiene gave no 7. The new butadiene adduct 7 is stable at room temperature even in the presence of air. Its lH and 13C NMR spectra have been assigned with the help of lH'H homonuclear COSY (COSYPHDQ)and lH-13C heteronuclear correlation (XHDEPTW).Its 'H NMR spectrum displays six different resonances, implying an asymmetric binding mode for the butadiene ligand; its 13CNMR spectrum shows evidence for an allyl ligand21 and for an sp3 carbon that is a-bonded to an osmium. Its mass spectrum and analysis show that it has one carbonyl less than 4 and 6. The structure of 7 has been confirmed by X-ray diffraction. This bonding mode is rare for butadiene. We are aware of only one dinuclear butadiene complex

In both cases, and with trans-l,4-dichloro-2-butene, the product of the reaction was 7 (eq 12) in about 2025% yield.

(-)

(CO),OS

-(-1Os(CO),

C

I

A

C

Or r - C I

CI

7

I

- Os(CO),

(C0)lOS

7

(12)

We have been unable to interconvert 7 and the 4/6 equilibrium mixture. Attempts to carbonylate 7 at pressures of up to 120 psig gave neither 4 nor 6 (eq 13). (27) Chisholm, M. H.; Huffman, J. C.; Lucas, E. A.; Lubkovsky, E. B. Organometallics 1991, 10, 3424. (28)As 7 is not formed from 4 or 6, the formation of 7 in eq 12 probably occurs by an electron transfer mechanism. (Note the similar yields from cis- and trans-l,4-dichloro-2-butene.) Electron transfer to a 1,3-diiodide from a dinuclear radical monoanion has been suggested: Yang, G . K.; Bergman, R. G. J . Am. Chem. SOC.1983,105, 6045.

Diosmacyclobutane Reaction with Butadiene and Allene

Organometallics, Vol. 14, No. 2, 1995 609

T

" 5.8 5.1 4.1

-0.78%

PPH

PPY

Figure 5. (Left) lH NMR of 9 in the region of H1 and Hz. (Right) Observed NOE.

M-M

M-M

b

a

A 4/6 mixture gave no 7 in the presence of a flow of butadiene (eq 14), just as it had not given any 7 photochemically (recall the discussion after eq 10 above).28 When 7 was heated under a pressure of butadiene it rearranged to the knownl7 8 (eq 15). Reaction of (CH&HCH~)OS~(CO)E (3) with Allene. A solution of 3 was stirred under allene at room temperature, with repeated venting in order t o remove the propylene released. After 10 h, IR showed that the reaction was complete; lH NMR showed that two products had been formed in a 9:l ratio (eq 16).

rf

(c0),0s-0s(c0), 3

+

-

M-M C

--. I I

M-

M-M

d

e

with the "three-spin The allene complex 9 does not show any fluxional behavior up to 25 0C.33 The allene ligand in 9 is the first example of this bonding mode for allene in a homobimetallic system; a known heterobimetallic example is [(CO)3Fe@-dppm)-$-C(CH~)CHZ)P~(PP~~)I.~~ The coordination chemistry of allene with mono- and dinuclear centers has been reviewed,35 the most common ways in which allene serves as a bridging ligand are shown in Figure 6.36 When a 9:1mixture of 9 and 10 was kept under 2 atm of allene at 25 "C for 48 h, all of the 9 rearranged to 10 (eq 17). 9 is thus the kinetic product of reaction 16, while 10 is the thermodynamic one. 25 T, 45 h

(16) (CO),Os-

OS(CO),

9

+ (Co),Os- OS(CO),

+ 2

(CO),Os-

9

Os(CO),

CH2C12

=

*

(CO),Os- OS(CO)~ 10

(17)

10

The minor product proved to be 10, first synthesized by Deeming and co-workers.18 The major product (9) was plainly that expected from a formal [2 21 addition reaction. Three signals in the 13C N M R of 9 (one quaternary carbon and two methylenes) arise from allenic carbons. The six carbonyl peaks in its 13CNMR, intensity ratio 2:2:1:1:1:1, require a plane of symmetry containing the allene ligand and the two osmiums. In the lH N M R of 9 there are three different resonances, two for the olefinic protons and one for the ring protons. Protons HI and H2 couple to H3 identically so they are indistinguishable by lH NMR (Figure 5). In order to differentiate between HI and H2 of 9, a difference NOE experiment was performed (Figure 5). When H3 was irradiated, HI showed a positive effect of 2%, while Ha showed a negative effect of -1%. Molecular modeling s t ~ d i e s ~predict ~ - ~ l that d(H3-Hl) should be 2.84 A, d(H1-Hz) should be 1.70 A, and the &-HIH2 angle should be 111". The geometry of the molecule is such that the observed negative effect is in agreement

+

Photochemical Reaction of Oss(C0)12 with Allene. When Os3(CO)12 was photolyzed in the presence of allene (eq 181, 10 was obtained in 40% yield along with a 55%yield of the mononuclear osmium complex 11. (29) Coordinates for the parent diosmacyclobutane 1were obtained .~~ were done from ab initio calculations by A. K. R a p ~ 6 Minimizations using the Dreiding force fieldS0with the Biograf molecular simulation program, Version 2.ZS1 The structure was minimized by use of a conjugate gradient technique with the carbon, osmium, and oxygen atoms of the OSZ(CO)~ fragment constrained to the ab initio geometry. The Os van der Waals parameters used were R = 3.00 A and E = 0.055 kcdmol. (30) Mayo, S. L.;Olafson, B. D.; Goddard, W. A. J.Phys. Chem. 1990,

94, 8897. (31) Biografwas obtained from the BioDesign subsidiary of Molecular Simulations Inc., 199 S. Los Robles Ave., Suite 540, Pasadena, CA 91101. (32) Derome, A. E. Modern NMR Techniquesfor Chemistry Research; Pergamon Press: New York, 1987; Chapter 5. (33) Mononuclear allene complexes are frequently fluxional. See: Shoshan, R. B.; Pettit, R. J.Am. Chem. Soc. 1967, 89, 2231. (34) (a) Fontaine, X. L. R.; Jacobsen, G. B.; Shaw, B. L.;ThorntonPett, M. J.Chem. Soc., Dalton Trans. 1988,1185. (b) Fontaine, X. L.

R.; Jacobsen, G. B.; Shaw, B. L.; Thornton-Pett, M. J . Chem. Soc., Chem. Commun. 1987,662. (35) Bowden, F. L.;Giles, R. Coord. Chem. Reu. 1976,20, 81.

Spetseris et al.

610 Organometallics, Vol. 14, No. 2, 1995

Scheme 1 CH2C12

0

10

11

12

11 is an air- and temperature-stable liquid. Its 13C NMR consists of the expected three signals from the allyl ligand and (below -40 "C) carbonyls in a 2:l:l ratio. Another difference NOE experiment was performed t o distinguish between the olefinic protons and showed a positive effect of 1%for HI and no effect for H2. (The fact that the effect at H2 is no longer negative for 11 implies that the geometry of HI, Ha, and H3 differs in detail from that of 9.) As with 9, the allene ligand of 11 showed no fluxional behavior up to 60 "C. Relative Equilibrium Constantsfor the Binding of Butadiene vs Allene to the O S ~ ( C OFragment. )~ After 72 h a t 0 "C, equilibrium was established among 3, butadiene, 4, 6, and propene (eq 8). lH NMR measurement of the relative intensities of the peaks of 3, butadiene, 4, and propene implied an equilibrium constant of 1.4 for eq 19. Similarly, after 72 h at 0 "C,

K,, > 100 +

=

(co),os-os(co), +

3

0 12

Dissociative Exchange

2

+

+

H2

82 "C

____)

co co

oc

I

--

.

..I..

'c'

A ,,,,,.,"co + P

co co

C

4

O

0

12

co co

a f

co co

C 0

12'

-

=/ (20)

9

c

equilibrium was established among 3,allene, 9 (without the formation of a significant amount of lo), and propene (eq 20). The equilibrium constant was too large to measure, implying that allene is bound much more tightly than butadiene. The heat of hydrogenation of one double bond of allene (AHfor eq 21) is 41.2 kcal mol-l at 82 "C, while that for one double bond of butadiene (AHfor eq 22) is 27.0 kcal mol-l at 82 0C.37The difference, 14.2 kcal mol-l,

=I=

c 0 12'

c

L (co),os-os(co),

Associative Exchange

I

AH=-41.2kcal/mol

(21)

predicts a much larger binding constant for the coordination of one double bond of allene than of butadiene. This difference in double bond stability must be at least partly responsible for the fact that K20 is much larger than K ~ s .

Conclusion It is becoming clearg that the exchange reactions of diosmacyclobutanes proceed via bridge-opened intermediates such as 12. Detailed kinetic studiesg of the reaction of 1 with olefins with electron-withdrawing substituents have established an associative mechanism (Scheme 1)for the exchange of 12 with incoming olefins; a dissociative mechanism, involving Osz(CO)safter all, is possible with relatively unreactive olefins. Matrix isolation1 and transient2 IR studies have shown that

0 12'

species like 12 are formed by the reaction of O S ~ ( C O ) ~ with incoming olefins. With either associative or dissociative exchange, Scheme 1 explains why we have obtained formal [2 21 addition products with butadiene and allene. Associative exchange gives 12' with only one C-C double bond coordinated, and isomerization gives a product like 4 or 9. Dissociative exchange would also lead to 12' and thus to 4 or 9. As we have been unable to prepare the butadiene

+

(36)(a) Nakamura, A. Bull. Chem. SOC.Jpn. 1966,39, 543. (b) Shoshan, R. B.; Pettit, R. Chem. Commun. 1968,247. (c) Davis, R. E. Chem. Commun. 1968,248. (d) Gervasio, G.; Osella, D.; Valle, M. Inorg. Chem. 1976,15, 1221. (e) Bailey, W. I., Jr.; Chisholm, M. H.; Cotton, F. A.; Murillo, C. A.; Rankel, L. A. J . Am. Chem. SOC.1978, 100, 802. (0 Lewis, L. N.; Huffmann, J. C.; Caulton, K. G. J . Am. Chem. SOC.1980,102,403. (9) Al-Obaidi, Y.N.; Baker, P. K.; Green, M.; White, N. D.; Taylor, G. E. J. Chem. SOC.,Dalton Trans. 1981, 2321. (h) Johnson, B. F. G.; Lewis, J.; Ftaithby, P. R.; Sankey, S. W. J . Organomet. Chem. 1982,232,C65. (i) Aime, S.; Gobetto, R.; Osella, D. Organometallics 1982,I , 640. (i) Hoel, E.L.; Ansell, G. B.; Leta, S. Organometallics 1986, 5 , 585. (k) Casey, C. P.; Austin, E. A. Organometallics 1986,5 , 584. (1) Casey, C. P.; Austin, E. A. J . Am. Chem. SOC.1988, 110, 7106. (m) Cayton, R. H.; Chisholm, M. H.; Hampden-Smith, M. J. J . Am. Chem. SIX.1986,110,4438.(n) Cayton, R. H.; Chacon, S. T.; Chisholm, M. H.; Hampden-Smith, M. J.; Huffman, J. C.; Folting, K.; Ellis, P. D.; Huggins, B. A. Angew . Chem., Int. Ed. Engl. 1989,28,1523. (0)Arce, A.J.; DeSantis, Y.; Deeming, A. J.; Hardcastle, K. I.; Lee, R. J . Organomet. Chem. 1991,406,209. (p) Chacon, S. T.; Chisholm, M. H.; Folting, K.; Huffman, J. C.; Hampden-Smith, M. J. Organometallics 1991,10,3722.(9)Seyferth, D.; Anderson, L. L.; Davis, W. B.; Cowie, M. Organometallics 1992, 11, 3736. (r) W u ,I. Y.; Tseng, T. W.; Chen, C. T.; Cheng, M. C.; Lin, Y. C.; Wang, Y.Inorg. Chem. 1993,32,1539. (37)Jensen, J. L.Prog. Phys. Org. Chem. 1976,12,189.

Diosmacyclobutane Reaction with Butadiene and Allene

Organometallics, Vol. 14, No. 2, 1995 611

Diels-Alder product 5,38 we remain uncertain of its energetics; we cannot be sure we would have seen it if it had been formed in any of the reactions in this paper. We have found no evidence that the diosmacyclobutane system is capable of the kind of cycloaddition reaction (reversible dissociation into o-xylylene and Co-Co, eq 5) that Hersh and Bergman have established for the benzodicobaltacyclohexene 2. Of course the thermodynamic driving force for the formation of 5 from butadiene is surely far less than that for the formation of 2 from o-xylylene.

DE-FG02-84ER132991, for funding this project, and Colonial Metals and Degussa Chemical Co. for the generous loan of 0 ~ 0 4 .We also thank Dr. Robert Barkley (University of Colorado, Boulder, CO) for mass spectrometry, Dr. Patricia Godson (University of Wyoming) for X-ray crystallography, and Dawn C.Wiser and Prof. Anthony K. Rapp6 for the modeling studies. We are grateful to Dr. Bruce Bender and Dr. Rick Sidler for valuable discussions, and to Karen Hennessey for preliminary work with 1,3,and butadiene.

Acknowledgment. We thank the Department of

Supplementary Material Available: Crystal structure data for 7, including tables of atomic parameters, anisotropic thermal parameters, bond distances, and bond angles (2 pages). Ordering information is given on any current masthead page.

Energy, Office of Basic Energy Research (DOE Award (38)The diosmacyclohexane analogous to 5, (pCH2CH2CH2CH2)OSZ(CO)S,is stable. It has been prepared from Naz[Osz(C0)81 and TfOCH2CH2CH2CH20Tf: Birdwhistell, K. R.; Norton, J. R., unpublished work.

OM940558D