4842
J. Am. Chem. SOC.1982, 104, 4842-4846
2-Cyclopropene- 1-carbonyl Compounds of Rhenium, Manganese, and Iron. A Facile Route to Nonfluxional 3-ql-Cyclopropenyl Compounds of Rhenium D. Michael DeSimone, Peter J. Desrosiers, and Russell P. Hughes*' Contribution from the Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755. Received November 30, 1981
Abstract: 2,3-Diphenyl-2-cyclopropene-l-carbonyl chloride reacts with [Re(CO)J, [Mn(CO)J, and [Fe(~-CSH5)(CO),]1-carbonyl chloride and 2to give the acyl compounds 2, 10, and 11, respectively. Similarly 2-tert-butyl-2-cyclopropenetert-butyl-3-deuterio-2-cyclopropene-l-carbonyl chloride react with [Re(CO)J to give the rhenium acyls 5 and 7, respectively. The rhenium acyls 2, 5, and 7 undergo a mild thermal decarbonylation reaction which proceeds with allylic rearrangement of the migrating cyclopropenyl group to give the (3-$-cyclopropenyI)rhenium compounds 3,6,and 8, respectively. Compound 8 is inert to ring-whizzing of the Re(CO)Smoiety at 63 OC, allowing a minimum activation energy of 32 kcal.mol-' to be calculated for such a process. The manganese acyl 10 also undergoes decarbonylation, but only [Mn2(CO)lo]and a tetraphenylbenzene can be isolated. The iron acyl 11 could not be decarbonylated thermally.
Allyl and substituted allyl ligands are ubiquitous in organoThis paper describes a new synthesis of (3-~'-cyclopropenyl)metallic chemistry; examples of v3-, V I - , and p-allylic ligands rhenium compounds, and the synthesis of 2-cyclopropene- 1 abound and their chemistry have been well established. Examples carbonyl compounds of rhenium, manganese, and iron. The of cyclopropenyl transition-metal compounds, containing the cyclic principal motivation for this study was to develop a synthetic analogue of the allyl ligand, are relatively rare. The only commethod for selectively generating deuterium-labeled 2-cyclopounds characterized to date in the which a symmetrical +COpropenyl compounds, in order to examine the facility with which ordination mode for a cyclopropenyl ligand has been reported are they might undergo the fluxional reaction commonly referred to [NiBr(C0)(7-C3R3)] (R = Ph,233t-Bu3), [NiBr(q3-C,-t-Bu3)]2,3 as ring-whizzing.15 A preliminary account of some of these has appeared.16 [ N ~ B ~ L ~ ( V - C(L~ P= ~CO, ~ ) IP Y ) , ' ~[ N ~ ( ~ ~ - C S H , ) ( ? ~ ~(R - C ~ R ~findings )I = Ph,4 t-Bu3), [ C O ( C O ) ~ ( ~ - C ~ P[MoBr(CO),L2(v-C3Ph3)] ~,)],~ Results (L = MeCN,6p7L2 = 2,2'-bipyridyl,' 1, I 0-phenanthroline'), and The reaction of 2,3-diphenyl-2-cyclopropene1-carbonyl chloride .6 Unsymmetrically bound cyclo[Mo(CO),(&H5)(q-C3Ph3)] with Na+[Re(CO)S]- in T H F solution at -78 "C yielded the propenyl ligands have been characterized in the cations [Mrhenium acyl compound 2; this compound proved to be surprisingly (PPh3)2($-C3Ph3)]+ ( M = Ni, Pd, Pt).8-'0 A number of compounds derived from C-C bond cleavage reactions have also been prepared. This latter topic is discussed in the following paper" and has also been the subject of a theoretical investigation.I2 In all cases, the synthetic approach to the cyclopropenyl compound Ph Ph has involved reactions of cyclopropenium cations with nucleophilic 3. 4 2. metal centers. 3-~'-Cyclopropenylligands are even rarer, and only one class labile in THF solution at temperatures exceeding -20 O C and could of compound containing such ligands had been characterized prior only be isolated in pure form by evaporation of the T H F at -20 to our work. The reaction of the [Fe(CO),(&H,)]anion with OC followed by extraction of 2 at 20 OC into a nonpolar solvent. various cyclopropenium cations was reported to yield compounds The IR and mass spectrum of 2 clearly established it as an l,I3J4 and the structure of la was confirmed ~rystallographically.~~ acylpentacarbonylrhenium compound. The I3C N M R spectrum of 2 showed the presence of a single type of phenyl group and a single resonance for the two olefinic carbon atoms, unambiguously defining the structure of 2 as shown, with a plane of symmetry c-. .Fe l o . R=R'=Ph. bisecting the cyclopropene ring. The ' H N M R spectrum of 2 R 1 b. R=Ph, R'=H. 0 showed a singlet resonance at 6 2.98 together with phenyl resot ~ R .= ~ B U R'= , ~e R nances. When 2 was left standing in THF or CDCI3 solution at 20-25 "C, it underwent a clean, quantitative thermal decarbonylation (1)Alfred P. Sloan Research Fellow 1980-1984. reaction to afford a single product, characterized by its IR and Kettle, S. F. A. Inorg. Chem. 1964, 3, 604-605. (2)Gowling, E. W.; mass spectrum as a pentacarbonylrhenium compound. In contrast (3)Olander, W.K.; Brown, T.L. J. Am. Chem. SOC.1972,942139-2140. (4)Rausch, M. D.;Tuggle, R. M.; Weaver, D. L. J. Am. Chem. Soc. 1970, to its immediate precursor 2, this compound exhibited no 'H NMR 92,4981-4982. resonances at high field, characteristic of protons attached to the ( 5 ) Chiang, T.;Kerber, R. C.; Kimball, S. D.; Lauher, J. W. Inorg. Chem. saturated carbon of a cyclopropene, but instead showed a singlet 1979,18, 1687-1691. resonance at 6 6.43, characteristic of a vinylic cyclopropene proton, ( 6 ) Hayter, R. G. J. Organomet. Chem. 1968,13, Pl-P3. (7)Drew, M. G. E.;Brisdon, B. J.; Day, A. J. Chem. SOC.,Dalton Trans.
Ga ;-f
1981,1310-1316. (8)McClure, M. D.; Weaver, D. L. J. Organomet. Chem. 1973, 54, C59C61. (9)Mealli, C.; Midollini, S.; Moneti, S.;Sacconi, L. Angew. Chem., Int. Ed. Engl. 1980,11, 931. (10)Mealli, C.; Midollini, S.; Monetti, S.; Sacconi, L.; Silvestre, J.; Albright, T. A. J. A m . Chem. SOC.1982, 104, 95-107. (11)Donaldson, W. A.; Hughes, R. P.,following paper in this issue. (12)Jemmis, E. D.;Hoffmann, R. J. A m . Chem. SOC.1980, 102, 257C-2575.
(13)Gompper, R.; Bartmann, E. Angew. Chem., Int. E d . Engl. 1978,17, 456-457. (14)Gompper, R.; Bartmann, E.; Noth, H. Chem. Ber. 1979, 112, 21 8-233. (15)For a review, see: Cotton, F. A. In "Dynamic Nuclear Magnetic Resonance Spectroscopy"; Jackman, L. M.; Cotton, F. A. Eds.; Academic Press: New York, 1975;Chapter 10. (16) Desrosiers, P. J.; Hughes, R. P. J. A m . Chem. SOC.1981, 103, 5593-5594.
0002-7863/82/l504-4842$01.25/00 1982 American Chemical Society
J . Am. Chem. SOC.,Vol. 104, No. 18. 1982 4843
3-7'- Cyclopropenyl Compounds of Rhenium together with phenyl resonances. The 13CN M R spectrum clearly indicated that the two phenyl rings were nonequivalent, as were the two olefinic carbon atoms of the cyclopropene. These data can only be reconciled with structure 3 and not with the expected product 4. Attempts to induce migration of the cyclopropenyl ligand back on to CO, by prolonged refluxing of solutions of 3 with PPh,, effected no such conversion, and 3 could be recovered unchanged. The acyl complex 5 was synthesized from the appropriate acyl chloride precursor at low temperatures, as described above. The 'H N M R spectrum of 5 exhibited a singlet t-Bu resonance at 6 1.15, a saturated cyclopropene proton resonance at 6 2.92 (d, J = 1.2 Hz), and a vinylic resonance at 6 6.18 (d, J = 1.2 Hz), clearly consistent with the illustrated structure. This molecule was even more labile than 2 toward decarbonylation and rapidly afforded a single product 6, whose structure was unambiguously
5. R = H
6. R = H .
7. R = D
8. R = O .
recovered unchanged from refluxing THF or benzene solutions. No thermal decarbonylation of 11 to give analogues of 1 was observed. I3C N M R data for 10 and 11 were also entirely compatible with those obtained for 2.
Ph 11
Discussion The migration of alkyl ligands to and from an adjacent C O ligand is a reaction of fundamental importance in organometallic chemistry and in many homogeneously catalyzed organic reactions.z1*22In every reaction of this type which has been reported to date, the migration involves a 1,2 shift of the alkyl group. In a particularly relevant example the migration of the 2-alkenyl ligand from Mo to C O in the conversion of 12 to 13 has been
9
characterized by its 'H N M R spectrum. A singlet t-Bu resonance (6 1.20) together with two doublets ( J = 1.2Hz) at 6 2.20 and 6.20 can only be interpreted in terms of structure 6. An analogous procedure yielded first the specifically deuterium-labeled acyl 7, whose 'H NMR spectrum exhibited only a singlet t-Bu resonance (6 1.15) and a singlet at 6 2.92 (cf. 5). This compound decarbonylated smoothly at 20 "C to give 8 as the sole product; 8 exhibited singlet 'H N M R peaks at 6 1.15 (t-Bu) and 6.20 (vinylic cyclopropene proton), but no resonance at 6 2.20 (cf. 6). The absence of this latter resonance was taken as conclusive evidence that a negligible amount of the isomeric compound 9 was produced during the decarbonylation of 7. The 3-v1-cyclopropenylcompounds 3,6, and 8 were moderately stable in chlorinated solvents under N2 but did decompose slowly at 20-25 "C to give [Re(CO)SCl] and unidentified organic products. Compound 8 could be recovered unchanged after 6 h in C6D6solution at 63 "C but decomposed slowly in refluxing C6D6 to give [Re2(CO)lo].Under the former set of conditions, assuming
