Communications to the Editor
6473 3300 G
I
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as well as reactivity patterns consistent with a RhI'TPP dimer (RhTPP)2. W e are presently attempting to grow crystals of RhTPP(02) and (RhTPP)2 suitable for X-ray structure determinations. Although no monomeric rhodium( I I ) porphyrin species has been directly observed, the Rh-Rh bonding in (RhOEP)2 and its reactivity with N O and 0 2 are indicative of a half-occupied d,2 i n Rh"0EP. The free-radical-like reactivity of the rhodium(l1) porphyrin unit is similar to that recognized for other low spin d7 complexes such as [Co(CN)5I3- l 6 and Rh(NH3)42+.6 The reactivity patterns for cobalt(I1) and rhodium( 11) porphyrins are closely related; however, increased thermal stability of the rhodium( 11)-dioxygen complexes and the unique metal-metal bonding are manifestations of the enhanced covalent bonding ability of the second transition series metal. Acknowledgment. This paper is based on work supported by the National Science Foundation M R L Program, under Grant No. DMR76-80994. A loan of rhodium trichloride from Matthey-Bishop is gratefully acknowledged. References and Notes (1) B. R. James and D. V. Stynes, J. Am. Chem. SOC.,94, 6225 (1972). (2) B. B.Wayland, J. V. Minikiewicz, and M. E. Abd-Elmageed. J. Am. Chem. Soc.. 96. 2795 11974). (3) F. A. Waiker, J.'Am. Chem. SOC.,95, 1150 (1973). (4) F. Basolo, B. M. Hoffman, and J. A. Ibers, Acc. Chem. Res., 8, 384 (1975). (5) R. J. Drago, T. Bevgelsdijk,J. A. Breese, and J. P. Cannady, J. Am. Chem. SOC., 100, 5374 (1978). (6) J. F. Endicott, C. L. Wong, T. Inoue, and P. Natarajan. tnorg. Chem., 18, 450 (1979). (7) H. Ogoshi, J. Setsune, and 2. Yoshida, J. Am. Chem. SOC.,99, 3869 (1977). (8) W. R. Scheidt and J. L. Hoard, J. Am. Chem. SOC.,95, 8281 (1973). (9) B. B. Wayland and M. E. Abd-Elmageed, J. Am. Chem. SOC.,96, 4809 (1974). (10) T. Szymanski. T. W. Cafe, R. P. Van Doyne. and F. Basolo, J. Chem. SOC., Chem. Commun., 5 (1979). (11) R. D. Giilard, B.T. Heaton, and D. H. Vaughn, J. Chem. SOC.A, 3126 (1970). (12) A. W. Addison and R. D. Gillard. J. Chem. SOC.A, 2523 (1970). (13) K. Nakamoto, "Infrared and Raman Spectra of Inorganic and Coordination Compounds", 3rd ed., Wiley. New York. (14) R. P. A . Muniz, N. V. Vugman. and J. Danon, J. Chem. Phys.,54, 1284 (1971). (15) E. Billig, S.I. Shupack, J. H. Waters, R. Williams, and H. B. Gray, J. Am. 86, 926 (1964). Chem. SOC., (16) J. Halpern, Acc. Chem. Res., 3, 386 (1970).
Bradford B. Wayland,* Alan R. Newman Department of Chemistry and Laboratory f o r Research on the Structure of Matter Unicersity of Pennsylcania, Philadelphia. Pennsylcania I91 04 Receiced March 30, I979
Figure 2. E P R spectra for dioxygen complexes of R h O E P in toluene glass (-160 " C ) : (a) R h O E P ( 0 2 ) , (b) R h O E P ( 0 2 ) (piperidine), (c) RhOEP(O1) [P(OBu)3],
with those reported for the complex previously formulated as Rh"TPP (Table I), suggesting that this species is actually the dioxygen complex, RhTPP(02). Authentic Rh(I1) species with effective D 4 h symmetry have substantially larger g values (gl 2.0, gl 2.3: (g) 2.2) associated with the (dx,2d,, ,:4)dzZ' electron c ~ n f i g u r a t i o n . ' ~Heating .'~ a solid sample of the compound that we formulate as RhTPP(02) a t 150 "C in high vacuum results in sublimation of a diamagnetic RhTPP compound. This species readily reacts with NO to form R h T P P ( N 0 ) ( U N O 1658 cm-') and reacts with 0 2 in the presence of donors to regenerate the EPR spectrum that we associate with RhTPP(02) complexes. The diamagnetic RhTPP species has N M R and electronic spectral properties
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0002-78631791 I501 -6473$01 .00/0
Cyclopropanation of Olefins with a Stable, Iron-Containing Methylene Transfer Reagent' Sir: A common synthetic transformation is the conversion of olefins into cyclopropanes. The importance of this conversion stems from the occurrence of cyclopropane rings in many natural products and from the utility of cyclopropanes as synthetic intermediates leading to other systems.2 A disadvantage of many of the previously reported methods for the cyclopropanation of olefins is that the species required for methylene transfer are often quite unstable and cannot be isolated easily if a t all. During the past decade, transition metal-carbene complexes have been studied e ~ t e n s i v e l y . ~ Although these species have structures that suggest that they may behave as carbene sources of possible use i n cyclopropa-
0 1979 American Chemical Society
Journal of the American Chemical Society
6414
n a t i ~ n they , ~ frequently exhibit quite different patterns of chemical behavior. However, several years ago, Jolly and Pettit reported the apparent generation of the iron-containing species (1) which was considered to be a cationic iron-carbene com-
r
Olefin
7
1) 1% Na(H9
>- -
2) c1cH2scH3
101.21
/
October 10, 1979
Table I. Cyclopropanation of Olefins with 3"
plex and which was reported to react with a few olefins to give cyclopropane^.^ More recently, 1 and related species (including complexes of other metals) have been subjects of various experimental and theoretical studies.6 These reports suggested to us that a useful cyclopropanation reagent may be available if a stable precursor of 1 could be prepared. In this communication we are pleased to report our development of a new reagent which fulfills this requirement. We have found that the sulfide 2 may be obtained in 93% yield (after crystallization) by the procedure of King and Bisnette (eq l ) , although these workers had reported a yield 1/2 [CpFe(CO) 2]
/
Cyclopropane
Conversion of
Olefin
Yield
(%lb
96
92
63
66
62
64
I00
96
Go 1
CpFe-CH2SCH3
do
(1)
(3)
of only 25%.' Methylation of 2 ( 1 equiv of (CH3)30+BF4-,8 CH?CI,, -20 to +25 "C) gives the sulfonium salt 3 (eq 2) in 82% yield as a yellow, crystalline solid: ' H N M R (CDCI,) 6 5.22 (s, 5 H), 2.74 (s, 6 H), 2.45 (s, 2 H). The salt 3 is quite stable in that it undergoes no noticeable change upon storage in the air for several months a t room temperature. Although not necessary for use in the reactions reported here, 3 may be purified conveniently by preparing a solution (-0.5 M) in D M F at 25 "C under an inert atmosphere, adding anhydrous diethyl ether (-3 vol.) until the solution just becomes cloudy, cooling the mixture slowly to -20 "C to induce crystallization, and removing the supernatant liquid with a syringe. The recovery is 70-80%. Vast satisfying is that, when 3 is heated at reflux in dioxane ( I -2 M solutions, 4-12 h) with olefins under a nitrogen atmosphere, cyclopropanes are produced directly (eq 3). Our results to date are summarized in Table I . The salt 3 appears to meet the goal of being a stable, isolable cyclopropanation reagent that may be used as a routine laboratory item. The isolation of products is generally quite simple: the reaction mixtures are diluted with pentane to precipitate the ironcontaining byproducts, and the cyclopropanes are obtained from the pentane solution by distillation or chromatographic procedures. The stereospecificity of the reaction is indicated by the last two entries in Table I; in each case, none of the opposite stereoisomeric cyclopropane9 could be detected within the limits of sensitivity (
