Znorg. Chem. 1980, 19, 1543-1551 (PPh,)X does not generate radical intermediates. On the basis of these results, we conclude that photoinduced geometric isomerization reactions of cis- and trans-CpM(CO),(PPh,)X occur via intramolecular rearrangements of the excited-state complexes. There a r e apparently three chemically distinct excited-state deactivation pathways available to these complexes, i.e., intramolecular isomerization, dissociation of carbon monoxide, and dissociation of PPh3. However, knowledge concerning the electronic structures of the ground-state complexes and the character of the low-lying excited states and their conversion pathways to other electronic states is severely lacking. Hopefully, relationships between electronic structure and photochemical reactivity patterns for these complexes will be elucidated in the near future. Acknowledgment. Portions of this work were carried out
1543
during the term of a University of Missouri Graduate Research Fellowship (to D.G.A.). We a r e indebted to Professor T. L. Brown for valuable discussions. Registry No. CpMo(CO),CI, 12128-23-3; ~ i s - C p M o ( C 0 ) ~ (PPh,)CI, 3201 1-69- 1; CpMo(CO)(PPh3)2CI, 33 152- 14-6; CpMo(CO),Br, 12079-79-7; cis-CpMo(CO)2(PPh,)Br, 31851-05-5; tr~ns-CpMo(CO)~(PPh~)Br, 3 1851-06-6; CpMo(CO),I, 12287-61-5; cis-CpMo(C0)2(PPh3)I, 57606-00-5; tr~ns-CpMo(CO)~(PPh~)1, 3201 1-70-4; CpMo(CO)(PPh3)21, 73104-92-4; CpW(CO)3Cl, 12128-24-4; CpW(CO),Br, 3713 1-50-3; CpW(CO),I, 31870-69-6; CpMo(CO)(PPh3)zBr, 73208-29-4; [ C ~ M O ( C O ) ~12091-64-4; ]~, c ~ s - C ~ W ( C O ) ~ ( P P ~ , )71425-48-4; CI, cis-CpW(C0),(PPh3)Br, 73173-84-9; cis-CpW(CO),(PPh,)I, 531 10-41-1; trans-CpW(CO)Z(PPh,)I, 531 10-40-0; [CpW(CO)3]2, 12566-66-4; [CpW(CO)4]BF4, 68868-84-8; c ~ ~ - C ~ M O ( C O ) ~ ( ” C O73104-93-5; )B~, tran~-CpMo(CO)~( ‘,CO)Br, 73 175-01-6.
Contribution from the Department of Chemistry, University of California, Los Angeles, California 90024
Chemistry via Metal Atom Cocondensation: Isomerization and Complexation Reactions of Organocyclopropanes and Spirocycles A. J. LEE HANLAN, R. C. UGOLICK, J. G. FULCHER, S. TOGASHI, A. B. BOCARSLY, and J. A. GLADYSZ* Received August 30, I979 Reactions of metal atoms with structurally diverse organocyclopropaneshave been studied. Quadricyclane (4) is isomerized to norbornadiene (5) upon cocondensation with a variety of metals, but control experiments suggest this reaction is heterogeneously catalyzed by metal aggregates which form upon warming the matrix. Norcarane (6), 2-norcarene (7), 3-carene (8), and 3-norcarene (9) give no reaction when cocondensed with a broad spectrum of metal atoms, despite the presence of an olefinic group in the latter three. When cyclopropylbenzene (11) is cocondensed with chromium, only bis(cyclopropylbenzene)chromium(O) (12) is formed. However, reaction of iron atoms with spiro[2.4] hepta-4,6-diene (14) yields a 14:64:6:17 ratio of 1,l’-diethylferrocene (15), 1-ethyl-1’-vinylferrocene (16), 1,l’-divinylferrocene (17), and [4]ferrocenophane (18) in 44% yield based upon iron. Cocondensations of iron with spiro[2.4]heptane (20; no reaction) and spiro[4.4] nona- 1,3-diene (23; formation of bis(tetrahydroindeny1)iron (24) and 1,2-tetramethylene- 1’-butylferrocene (25)) are also reported. Possible mechanisms of spirocycle (14, 23) ring opening and product formation are discussed. No volatile bis(arene)chromium(O) complexes are formed when benzocyclopropene (27) and dispiro[2.2.2.2]deca-4,9-diene (28) are cocondensed with chromium, although the former is polymerized. The preparation of 18 from 1,l’-dilithioferrocene (19) and 1,4-dibromobutane is also described.
Introduction The catalytic and stoichiometric interaction of inorganic and organometallic compounds with organocyclopropanes has been of substantial recent interest.’,* Strained cyclopropanes such as bicyclobutanes have been isomerized to more stable valence isomers with a variety of catalyst^.^^^ Numerous stoichiometric ring opening reactions have been observed. T h e involvement of metallocyclobutanes such as 1 has been suggested in many of these transformations. Metallocyclobutanes are also believed to be pivotal olefin metathesis intermediates: and their involvement in Ziegler-Natta olefin polymerization has recently been p r o p o ~ e d . ~ General preparative routes to metallocyclobutanes have not yet been developed. A few metallocyclobutanes have been ( 1 ) Recent leading references: (a) Sarel, S. Acc. Chem. Res. 1978, 11,204; (b) Tulip, T. H.; Ibers, J. A. J . Am. Chem. SOC.1979,101, 4201; (c) Hogeveen, H.; Nusse, B. J. Zbid. 1978, 100, 3110; (d) Rajaram, J.; Ibers, J. A. Ibid. 1978, 100, 829; (e) Salomon, R. G.; Salomon, M. F.; Kachinski, J. L. C. Zbid. 1977, 99, 1043. (2) Bishop, K. C. Chem. Reu. 1976, 76, 461. (3) (a) Gassman, P. G.; Reitz, R. R. J . Am. Chem. SOC.1973, 95, 3057. (b) Dauben, W. G . ;Kielbania, A. J.; Raymond, K. N. Zbid. 1973, 95, 7166. (c) Paquette, L. A.; Zon, G . Ibid. 1974, 96, 203, 215, 224. (4) (a) Katz, T. J. Adu. Organomet. Chem. 1977,16, 283. (b) Grubbs, R. H. Prog. Znorg. Chem. 1978, 24, 1 . (c) Calderon, N.; Lawrence, J. P.; Ofstead, E. A. Adu. Organomet. Chem. 1979, 17, 449.
(5) Ivin, K. J.; Rooney, J. J.; Stewart, C. D.; Green, M. L. H.; Mahtab, R. J. Chem. SOC., Chem. Commun. 1978, 604.
0020-1669/80/ 13 19- 1543$01 .OO/O
obtained by the oxidative addition of cyclopropanes to platinum complexes,6 and the tungsten metallocyclobutane 2 has been prepared from a cationic a-allyl precursor.’ Since improved accessibility of metallocyclobutanes would facilitate the study of their properties, we considered the possibility that the parent ring system 3 might result from the insertion of a transitionmetal atom into a cyclopropane carbon-carbon bond.
Transition-metal atoms are highly reactive species by virtue
of the 70-200 kcal/mol required for their formation.8a Hence they can be utilized for the preparation of organometallic compounds whose synthesis would be difficult or impossible (6) (a) McQuillin, F. J.; Powell, K. G . J. Chem. SOC.,Dalton Trans. 1972, 2123. (b) Lenarda, M.; Ros, R.; Graziani, M.; Belluco, U. J. Organomet. Chem. 1974, 65, 407. (c) Binns, S. E.; Cragg, R. H.; Gillard, R. D.; Heaton, B. T.; Pilbrow, M. F. J . Chem. SOC.A 1969, 1227. (d) AI-Essa, R. J.; Puddephatt, R. J.; Quyser, M. A,; Tipper, C. F. H. J. Organomet. Chem. 1978, 150, 295. (7) (a) Ephritikhine, M.; Green, M. L. H.; MacKenzie, R. E. J . Chem. SOC., Chem. Commun. 1976, 619. (b) Ephritikhine, M.; Green, M. L. H. Ibid. 1976, 926. (8) (a) Timms, P. L. Ado. Znorg. Chem. Radiochem. 1972, 14, 121. (b) Timms, P. L.; Turney, T. W. Adu. Organomet. Chem. 1977, 15, 53.
0 1980 American Chemical Society
1544 Inorganic Chemistry, Vol. 19, No. 6,1980
Hanlan et al.
Table I. Quadricyclane (4) Reactions %
mmol of 4: recovered yield of dimer t turnover metal, conditionsu mmol of metdb 40 5C po1ymer”d per metale 1 Ti, cocondensation 185 88 8 1 16 2 Ti, cocondensation 13 82 15 1 2 3 Cr, cocondensation 41 25 70 1 29 4 Cr, surface 15 97 3 0 0.4 5 Cr, cocondensationf 13 98 2 1 0.4 6 Fe, cocondensation 7.4 0 61 1 5 7 Fe, surface 4.7 0 79 1 4 8 Fe, cocondensationf 5.9 77 18 2 1 9 V, cocondensation 17 18 71 4 13 10 Mo, cocondensation 56 96 2 1 2 11 Co, cocondensation 4.2 0 47 21 3 12 Ni, cocondensation 22 20 44 25 15 See also Experimental Section. A correction factor, determined as described in the Experimental Section, was used to calculate the amount of evaporated metal reaching the reaction zone. Reaction scales: 11-22 mmol of 4. Yields are based upon 4 and represent isolated materials. Material of the formula (C,H,), (n > 2) obtained by extraction of the reactor residue after pumping off 4 and 5 . e mmol of 2 reacted:mmol of metal. One-hour warm-up omitted; volatiles (4, 5) pumped directly into trap as matrix warmed. entry
~
by conventional Reaction types observed between organic molecules and metal atoms include direct a complexation,’O oxidative a d d i t i ~ n ,and ~ oxygen abstraction.“ Experimentally, metal vapor and excess (tenfold or greater) organic compound are cocondensed on a 77 K surface.’* The concentration of metal atoms must be kept low because metal atom reaggregation is a low activation energy process which can compete with complex formation. Klabunde has generalized that unless the organic reactant has nonbonding or K electrons, metal atom repolymerization will be rapid at 77 K.9 However, we felt that cyclopropanes would be sufficiently reactive due to their strain energy and high lying Walsh orbitals to afford metallocyclobutanes such as 3. While such highly coordinatively unsaturated products would undoubtedly react further upon warming, trapping via the introduction of additional ligands (CO, PPh3, etc.) to the matrix might afford complexes with some stability at room temperature. Hence we initiated an extensive study of the chemistry observed when metal atoms are cocondensed with organocyclopropanes, the results of which are reported in this paper.I3
Results Quadricyclane (4)14was cocondensed with a variety of metal metal atoms
4
+
dimer and polymer
~~~
terial was presumed to be polymeric. The volatile components of the reactor extract were shown to be C l 4 H I 6dimers by G C / M S ; G C retention times were identical with those of dimers obtained from the cocondensation of chromium and molybdenum atoms with norbornadiene. T h e combined yield of dimers and polymer is given in Table I. Several control experiments were conducted. Condensation of 4 onto the walls of the reactor with hot, nonevaporating tungsten filaments in place of the normal metal atom sources did not result in any reactions. When chromium alone was evaporated onto the reactor walls (77 K), followed by deposition of 4 (Table I, entry 4), little isomerization was observed. However, when a cocondensation was conducted as usual but the volatile products pumped directly into a trap as the matrix warmed (entry 5), virtually no isomerization was observed. T h e important implications of these observations will be discussed below. In experiments conducted with iron, a preformed iron surface (entry 7) was as active as d e p o s i t e d iron (entry 6 ) . Again, when the 1 h matrix warm-up was eliminated (entry 8), less isomerization was observed. Reactions of norcarane (6) and the structurally related vinylic and allylic cyclopropanes 7-9 were investigated next.
(1)
5
atoms at 77 K over a 0.5-1.0 h period in the reactor described in the Experimental Section. The matrix was allowed to warm for 1 h under static vacuum (unless noted) before workup. Volatiles (C7Hs material) were then pumped into a cold trap, weighed, and analyzed by N M R and GC. In all cases, some norbornadiene (5) was present, as summarized in Table I. Less volatile products were isolated by extracting the residue remaining in the reactor after pump-off of 4 and 5. A portion of this extract was nonvolatile, formed a cream-colored precipitate, and analyzed approximately for (C,H8)n. This ma-
When cocondensed with metal atoms (see formulas) as described for 4,6-9 were recovered in nearly quantitative yields; no isomers could be detected by GC or ‘H N M R , even in the reactor residue. N o distinctive colors (other than pale yellow) were observed in the cocondensation matrices. T h e cocondensation of cyclopropylbenzene (11) with chromium atoms afforded a 45% yield (based upon chromium) of bis(cyclopropylbenzene)chromium(O) (12), which was characterized by mass, ‘H N M R , and I3CN M R spectroscopy. Air oxidation produced the bis(cyc1opropylbenzene)chromium(1) cation, which was isolated as its tetraphenylborate salt (13) (eq 2).
Klabunde, K. J. Acc. Chem. Res. 1975, 8, 393. Skell, P. S.; McGlinchey, M. J. Angew. Chem., Int. Ed. Engl. 1975, 14, 195.
Gladysz, J. A.; Fulcher, J. G.; Togashi, S . J. Org. Chem. 1976,41,3647; Tetrahedron Lett. 1977, 521. For excellent summaries of the techniques involved, see: (a) Moskovits, M., Ozin, G. A,, Eds. “Cryochemistry”; Wiley: New York, 1976; (b) Inorg. Synth. 1979, 19, Chapter 2. Portions of this work have been communicated: Gladysz, J. A,; Fulcher, J. G.; Ugolick, R. C.; Hanlan, A. J. L.; Bocarsly, A. B. J . Am. Chem. SOC.1979, 101, 3388.
Smith, C. D. Org. Synth. 1971, 51, 133.
iI
n
12
N
-
13
When nickel was cocondensed with cyclopropylbenzene, a yellow-orange matrix was formed, which when warmed afforded only starting material. Cocondensation of 11 with vanadium yielded a small amount of an air-sensitive, unstable oily red product, which upon decomposition gave cyclo-
Inorganic Chemistry, Vol. 19, No. 6,I980 1545
Metal Atom Cocondensations Table 11. NMR Data on C,, Ferrocenes compd
Fib---
butyl chain ‘H NMR”
NMR~
cyclohexyl methylene
2.24 (t, J = 8 Hz,4 H) 1.33 (m, 8 H) 0.84 (t, J = 7 Hz, 6 H) 33.3, 29.1, 22.7, 14.0
3.90 (s, 8 H) 68.7,67.7‘
‘H NMR
2.61 (m, 4 H) 2.27 (m, 4 H) 1.89 (m, 4 H) 1.60 (m, 4 H) 24.2, 23.7
Fe
I3C NMR
e
cyclopentadienyl ring
‘ H NMR
2.29 (m, 4 H, overlapped)d 1.47 (m, 6 H, overlapped)d 0.90 (t, J = 7 -Hz, 3 H)
13C NMR
33.5, 28.7, 22.7, 14.0
3.82(d,J=2Hz,2H) 3.71 (t, J = 2 Hz, 4 H) 84.7, 68.5, 67.7
2.58 (m, 2 H) 2.29 (overlapped)d 1.85 (m,2 H) 1.47 (overlapped)d 24.5, 23.7
3.91, 3.88 (br s, 7 H to tal) 69.8 (br), 66.4 (br)‘
25
a
in CDCl, relative (CH,),Si. Ppm, at 5 0 MHz in CDCl, relative (CH,),Si. Butyl-chain protons not resolved from cyclohexyl methylene protons.
6 , at 200 MHz
not observed.
propylbenzene. N o allylbenzene, methylstyrene, or styrene were detected in any of these reactions. The cocondensation of spiro[2.4]hepta-4,6-diene(14)15with iron atoms resulted in a dark orange syrup after matrix thawing. Recovered ligand was found by G C and ‘ H N M R to be devoid of isomerized material. The reactor residue was extracted with benzene and chromatographed on silica gel. A fast moving orange band was collected and shown by G C to contain four major products in a 14:64:6:17 ratio (in order of elution). Samples of each were purified by preparative GC. Spectroscopic properties suggested the structures 1,l’-diethylferrocene (15), 1-ethyl- 1’-vinylferrocene (16),1,l’-divinylferrocene (17),and [4]ferrocenophane (18),respectively (see Scheme I below). T h e total isolated yield of ferrocenes (based upon iron and an average product formula of Cl4HI6Fe) was 44%. Chemical evidence was obtained for the proposed structures 15-18. When a portion of the reaction mixture was hydrogenated, 16 and 17 were converted to 15. Pure 15 was identical with an authentic sample. An independent synthesis of 18 was achieved (33% yield) by the reaction of 1,l’-dilithioferrocene (19)16with 1,4-dibromobutane (eq 3).
9
w ie
N o volatile products formed when spiro[2.4]heptane (20) was cocondensed with iron atoms. When mixtures of 14 and P(OCH,), were cocondensed with iron atoms (ratios as high as 1:4), only ferrocenes 15-18 were produced. When 14 was cocondensed with chromium atoms and nickel atoms, brightly colored volatile products formed. Because of their sensitivity, these complexes were not characterized. When 14 was cocondensed with cobalt atoms, a brownish matrix was obtained. While the matrix was warmed to room temperature, 1 atm of C O was introduced into the reactor. Excess 14 was then fractionated from a volatile orange oil. (15) Kosman, D.; Stock, L. M. J . Org. Chern. 1975, 40, 2255. (16) (a) Rausch, M. D.; Ciappenelli, D. J. J. Orgunornet. Chem. 1967,10, 127. (b) Bishop, J. J.; Davison, A.; Katcher, M. L.; Lichtenberg, D. W.; Merrill, R. E.; Smart, J. C. Ibid. 1971, 27, 241.
Alkyl-substituted ferrocene carbon(s)
Subsequently isolated was a ca. 1:l mixture of the known compounds 21 and 22 (eq 4).” However, in multiple runs, yields of 21 and 22 never exceeded 1% (based on cobalt).
u 14 z ?? The cocondensation of spiro[4.4]nona-l,3-diene(23)15with iron atoms also resulted in the formation of ferrocene products but in lower (5-20%) yields. The two major products obtained (in 1:5 to 1:9 ratios) were purified by preparative GC and spectroscopically characterized. T h e product with the longer retention time (major product) was shown to be bis(tetrahydroindeny1)iron (24)’*by comparison to an authentic sample. The other product was a new compound. Its mass spectrum indicated a molecular weight 2 greater than that of 24. Its 200-MHz ‘H N M R spectrum and 50.32-MHz I3C N M R spectrum were virtually identical with the superimposed spectra of 24 and 1,l’-dibutylferrocene, as summarized in Table 11. Hence the structure 25 was assigned. No 1,l’dibutylferrocene was detected in the reaction mixture by GC. A reaction mixture was exposed to P t 0 2 / H 2 , but the G C trace was unaffected. These conditions would have hydrogenated any 1-butyl- 1’-butenylferrocenes to 1,l’-dibutylferrocene. An attempt was made to synthesize an authentic sample of [8]ferrocenophane (26)by the reaction of 1,l’-dilithioferrocene (19) with 1,8-dibromooctane. However, the major nonpolymeric products obtained were octylferrocene and 1,l’dioctylferrocene (eq 5).
Two other organocyclopropanes were cocondensed with chromium atoms. Benzocyclopropane (27,contaminated with (17) Eilbracht, P. Habilitationsschrift, Darmstadt, West Germany, 1978. Eilbracht, P.; Dahler, P.; Tiedtke, G. J . Orgunornet. Chem. 1980,185, C25. (18) Osiecki, J. H.; Hoffman, C. J.; Hollis, D. P. J. Orgunornet.Chem. 1965, 3, 107. e .-
1546 Inorganic Chemistry, Vol. 19, No. 6,1980
a trace of toluene and a small (
