J . Am. Chem. SOC.1992, 114, 6580-6582
6580
Figure 1. ORTEP plot of 2a. IO5
-
2(v5-C5H4CH3)2Nb(CO)R + 0 2 1 2($-C5H4CH,)2Nb(q2-C02)R (1) 2 treatment of a toluene solution of (q5-C5H4CH3)2Nb(CO)R (1W; R = CH2Si(CH3)3,CH2C(CH3),, CH3) with O2(1 atm, 20 "C) generated the corresponding C 0 2 complexes ( Q ~ - C ~ H ~ C H ~ ) ~ N ~ (q2-C02)R( 2 b 1 i ~ 3 ~in~ high ) yield (80-95%). Similarly, when a T H F solution of (T&H~)~MO(CO)'~was expased to O2(1 atm) at 0 OC, the carbonyl absorption at 1914 cm-l disappeared within minutes and about 10% ($-CSH5)2Mo(~2-C02)13 and 18% ($C5H5)2Mo(s2-C03)16 were generated along with ($-C5H5),Mo0. Since (~5-C5Hs)2Mo(q2-C02) undergoes thermal disproportionation only slowly under these conditions,16 the carbonate complex formed may be derived from oxygen oxidation of ($C5H5)2M0(q2-C02). These findings not only afford new insight into the possible role of metal-CO, complexes in catalytic CO oxidation but also offer a new, convenient synthetic route to such complexes." Studies are underway to establish the scope and mechanistic details of these reactions.
1
Acknowledmnent. We are grateful for suDwrt Drovided bv the
US.DepartGent of Energy: Office of Baiic Eiergy Scidnces (89ER13997).
1
l"
2000
1450
19bo
is's0
isbo
17'50
17bo
1650
Supplementary Material Available: Preparative and spectroscopic data for compounds l a 4 and Za-d, tables of positional and thermal parameters, and tables of interatomic distances and angles (8 pages); table of observed and calculated structure factors for 2a (10 pages). Ordering information is given on any current masthead page.
Wavcnumbcrs ( cm.' )
-
Figure 2. IR spectra: (a) (-) la (0.36 mmol) in PhCH3 under N,; (b) (- -) la + 0.090 mmol of O2 l a + 2a; (c) (- - -) la + 0.180 mmol of O2 2a. The absorption a t 1710 cm-' in a - c is from incomplete solvent subtraction or an impurity in la.
-
That the additional oxygen atom in 2a was derived from dioxygen was clearly established by isotopic labeling. Thus, reaction of l a with I8O2 (99%) produced >90% (q5-C5H4CH3)2Nb(CI80l60)CH2Ph(2a*) as determined by MS analysis.'* Interestingly, the IR spectrum of 2a* indicated that the lSOlabel was almost equally distributed between the coordinated and uncoordinated oxygen atoms of the q2-C02ligandst2 Scrambling of the label is not the result of postoxidation ligand exchange since no incorporation of C i 6 0 2occurred when a toluene solution of 2a* was stirred under 1 atm of CI6O2for 20 h. These results are consistent either with an oxidation pathway involving a symmetrically bound C 0 2 intermediate of a fluxional process for product 2a* causing interchange of the oxygen atoms. The stoichiometry of the reaction was determined by titrating a toluene solution of l a (0.36 mmol) with oxygen. IR analysis (Figure 2) showed that addition of 2.0 mL (0.090 mmol) of O2 (by gas syringe) caused ca. 50% conversion of l a to 2a; addition of another 2.0 mL of oxygen resulted in total disappearance of the remaining la within 5 min. Thus, the reaction of 1 with oxygen proceeds according to eq 1 with incorporation of both oxygen atoms of O2 into the product 2 . In a preliminary assessment of the generality of the metalmediated carbon monoxide oxidation process, a number of related carbonyl complexes were screened for oxygen reactivity. Thus,
(15) Geoffroy, G. L.; Bradley, M. G.Inorg. Chem. 1978, 17, 2410. (16) Belmore, K. A,; Vanderpool, R. A.; Tsai, J.-C.; Khan, M. A.; Nicholas, K. M. J . Am. Chem. SOC.1988, 110, 2004. (17) Reviews: (a) Behr, A. Carbon Dioxide Acfiuation by Metal Complexes; VCH: W. Germany, 1988. (b) Ito, T.; Yamamoto, A. In Organic and Bioorganic Chemistry of Carbon Dioxide; Inoue, S.,Yamazaki, N., Eds.; Halstead Press: New York, 1982; Chapter 3, pp 79-151. (c) Darensbourg, D.; Kudaroski, R. A. Adu. Organomet. Chem. 1983, 22, 129.
Silylcarbocyclization Reactions Catalyzed by Rh and Rh-Co Complexes Iwao Ojima,* Robert J. Donovan, and William R. Shay Department of Chemistry State University of New York at Stony Brook Stony Brook, New York I 1794-3400 Received March 18, I992
In the course of our study on the mechanism, scope, and limitation of "silylformylation", which was discovered independently by Matsuda et al.' and by US,^ we isolated a small amount of 2,5-dibutyl-3-(dimethylphenylsilyl)-2-cyclopenten-l-one(la) as a side product in the reaction of 1-hexyne with dimethylphenylsilane catalyzed by C O ~ R ~ ~ ( or C Rh,(CO) O ) ~ ~ 12.3 Under more optimized conditions, e.g., triethylsilanel (t-BuNC),RhCo(CO)? at 60 OC, cyclopentenone lb (R3Si = Et3Si) was obtained as the major product in 54% yield (eq 1). In order to accommodate this unique cyclization, it was reasonable to assume that the
( I I ) Bristow, G. S.; Hitchcock, P. B.; Lappert, M. F. J . Chem. Soc., Chem. Commun. 1981, 1145. ( I ) (a) Matsuda, 1.; Ogiso, A,; Sato, S.; Izumi, Y. J . Am. Chem. Soc. 1989, 1 1 1 , 2332. (b) Matsuda, I.; Ogiso, A,; Sato, S. J . Am. Chem. SOC.1990,112, (12) MS (12 eV, EI, m / e ) of 2a*: 358 (25) I(C5H4CH3)2Nb('60)the IR of 2a* had nearly 6120. CH*Ph'), 360 (25) ((C5H4CH3)2Nb('*O)CH2Ph+J; equal intensity absorptions at 1732 (C=I6O) and 1713 cm-' (C='*O) in (2) {a) Ojima, I. 22nd Organosilicon Symposium, April 7-8, 1989, Philtoluene (1704 and 1675 cm-' in KBr). A comparable solution/KBr IR shift adelphia, PA, Abstracts, Plenary 7. (b) Ojima, I.; Ingallina, P. 23rd Orgaalso has been noted for Cp,Mo(v2-C02)." Most v2-C02complexes, like 2, nosilicon Symposium, April 2C-21, 1990, Midland, MI, Abstracts G2. exhibit a strong v(CO),,,, and a very weak or nonobservable Y ( C O ) ~ ~ ~ . ~ (3) ~ ~Ojima, ~ ~ 1.; - ~Ingallina, ~ P.; Donovan, R. J.; Clos, N. Organometallics 1991, (13) Gambarotta, S.;Floriani, C.; Chiesi-Villa, A,; Guastini, C. J . Am. IO, 38. Chem. Soc. 1985, 107, 2985. (4)Ojima, 1.; Clos, N.; Donovan, R. J.; Ingallina, P. Organometallics 1991, (14) Jegat, C.; Fouassier, M.; Mascetti, J. Inorg. Chem. 1991,30, 1521. 10, 321 I .
0002-7863192115 14-6580$03.00/0 0 1992 American Chemical Society
-
J . Am. Chem. SOC.,Vol. 114, No. 16, 1992 6581
Communications to the Editor 8-silylacryloyl[M] intermediate 3 (M = RhCo), which was generated via &silylethenyl[M] complex 2, was trapped by an olefinic species such as 2-silyl- l - h e ~ e n e . ~
Scheme I PhMe2SIH cat (CO or N?)
os \
SIMe,Ph
7
RsSHtCO,
*
y
s
I
R
CHo SF
3
-SIR,
R,SI t a l iRh.(COir2 (I B u N C I ~ ~ C O I C O ) ~ RISi = (a1 PhMe2Si lb) Etas?
HS
R'hs,R, [MI
$.-S .R ,$
[MI
3
2
If this is the case, we should be able to trap 3 with externally added alkenes, and such a reaction would be potentially very useful as a new synthetic method. However, attempted trapping of 3 with a variety of alkenes was unsuccessful. Accordingly, we investigated an intramolecular trapping of a j3-silylacryloyl[M] species or &silylethenyl[M] species by using allyl propargyl ether (4) diallylpropargylamine (5), and allyldipropargylamine (6)as substrates, which led to the discovery of novel silylcarbocyclization (SiCAC) reactions. We communicate here our preliminary study on two types of such SiCAC reactions. The reaction of allyl propargyl ether (4,4.0mmol) with dimethylphenylsilane (4.0mmol) catalyzed by Rh4(C0)12(0.04 mmol, 1.O mol %) was carried out in toluene (1 5 mL) at 70 OC and ambient pressure of C O for 18 h to give 3-(silylmethylene)-4methyltetrahydrofuran (7)in 6 1% yield as the sole product through a novel silylcarbocyclization (SiCAC).S It is apparent that 7 is formed via the intramolecular trapping of 8-silylethenyl[M] intermediate 4A with the ethenyl moiety, followed by hydride shift (Scheme I). Since this SiCAC reaction (type 1-SiCAC) should not require carbon monoxide, we carried out the reaction under nitrogen. In fact, when Rh(acac)(CO)z was used as a catalyst under nitrogen, 7 was obtained in 85% yield accompanied by a small amount of hydrosilylation product, (E)-l-(dimethylphenylsilyl)-4-oxa-1,bheptadiene (8) (< The type 1-SiCAC reaction was further applied to diallylpropargylamine (5) by using Rh(acac)(CO)* a t 70 OC and ambient pressure of carbon monoxide to give the corresponding pyrrolidine 9 exclusively in nearly quantitative yield (eq 2).5
10A
11A
10
11
(
