6489
Reaction of Diiron Nonacarbonyl with Benzvalene. Fragmentation, Rearrangement, and Hydrogen Transfer
1
+ Fe(CO),
Sir: Recent work has demonstrated strikingly the manifold reactions of the vinylcyclopropyl group in polycyclics with metal carbonyls. Benzvalene (1) offers an interesting substrate for this reaction because it possesses the structural prerequisites for either u-a allyl complexation as with semibullvalene la+ or ferretane formation as with dibenzosemibullvalene.2 These processes correspond to cleavage of one of the four equivalent cr bonds (a) or insertion into the one unique u bond (b), respectively. Reaction of benzvalene (1)3 in Etz0-C6H6 at 50" (OQ3Fe I
-
,
Fe( CO)
CbH,-Et?O
io',
4
hr
2
0 Fe -Fe
Fe -Fe 0 3
4
OC\
KC
H \
/
0 C \
,co
J@Fc\2FeQ+ CH
5 c o n f i g u r a t i o n u n k now n
mixed cyclopentadienyl complex di-p-carbonyl-dicarbonyl- ?r-methylcyclopentadienyl- a - cyclopentadienyldiiron was indicated by mass spectral analysis.* Formation of 3 and 4 involves an unprecedented loss of CH from the C6H6starting material. Formation of 5 requires a reduction step and this accounts for the C). overall stoichiometry (2CsH6 + CsH6 C6H7 under nitrogen with a twofold excess of diiron nona2 results from a 1,2-hydrogen migration for Complex carbonyl for 4 hr followed by chromatographic separawhich ample precedent exists. l 1 The following mechtion on alumina yielded hexacarbonylfulvenediiron (2),6 trans-di-p-carbonyl-dicarbonyldi-a-cyclopentadi- anistic pathway represents a working hypothesis for enyldiiron (3), cis-di-p-carbonyl-dicarbonyldi-a-cyclo- rationalization of this complex series of reactions. The salient feature of this mechanism is that the pentadienyldiiron (4),8 and di-p-carbonyl-dicarbonyldiC6H6,C6H7,and C j H j products may derive from two a-methylcyclopentadienyldiiron ( 5 ) of unknown condifferent initial intermediates. Sequence 1 + 6 + 7 4, and 5 is 2 : 1 :1 figuration. The yield ratio of 2, 3 with 20 % total yield. Also a very small amount of the
+
+
+
(1) (a) R. M. Moriarty, C.-L. Yeh, and R. C. Ramey, J. Amer. Chem. Soc., 93,6709 (1971); (b) R. M. Moriarty, C.-L. Yeh, K.-N. Chen, and R. Srinivasan, Tetrahedron Lett., 5325 (1972); (c) R. Aumann, Angew. Chem., 84,583 (1972). (2) R. M. Moriarty, I
