1744
COMMUNICATIONS TO THE EDITOR
Vol. 81
for [CsHs(CsHs)sCO]Fe(CO)3 shown in Fig. 1. The three CO's and the midpoints of the two double The present reliability index, X I , is 9.47,for 970 bonds of the diene group then would form a disindependent, observed reflections. torted tetragonal pyramidal configuration about a In agreement with the chemical evidence, the five-coordinated iron. Another formal representaintramolecular distances clearly indicate bonding tion proposed by Wilkinson and co-workers16-18 of the Fe(C0)3 fragment with only two of the from n.m.r. studies (but found by them to be in three double bonds of the ring. This organo- conflict with the infrared data) involves a Dielsmetallic interaction results in a bending of the Alder type addition of the diene system to the iron tropone ring (Fig. 1) at atoms C4 and C, into two atom with the central two carbon atoms, Cgand cg, approximate planes-one plane comprising the forming a coordinate double bond. This latter diene-type carbon atoms C4, C5, C6 and Ci; and structural representation based on a three-point the other plane containing the remaining ring attachment of the butadiene residue to the iron atoms. A similar molecular configuration has atom via the two u-alkyl bonds and the bond to the been found by Dodge and Schomakerg in tropone- central olefinic group would lead to an approxiiron tricarbonyl; the (~yn-butadiene)-Fe(CO)~mately octahedrally coordinated iron atom. residue also is embodied in C4H6Fe(CO)3,10FezWe strongly favor the latter description of bonding primarily on the basis of distortion of the (cO)s(COH),(CH3C,CH,)," Fea(CO)s(Ct"CZC6H5)2,12 (OC)3Fe(COT)Fe(C0)3,1a and (COT)- terminal C4 (and presumably C7) atoms toward sp3 Fe(C0)3.14 hybridization. Of course, the actual electronThe molecular geometry of the triphenyl- density distribution will involve contributions from tropone-Fe(C0)3 complex provides an explanation both formal structures. A number of other closely for the non-planarity of the tropone ring. The related conjugated diene-transition metal comphenyl groups attached to ring atoms C2 and C6 p l e x e ~ ' ~should ~ ' ~ possess similarly deformed conare twisted out of the mean planes of the ring figurations. carbon atoms; the phenyl bonded to the terminal We gratefully thank Dr. Hiibel and co-workers diene atom, Cd, however, is not only twisted but for supplying us with a sample of the compound. bent out of the mean diene plane such that the We wish to acknowledge the use of the computing bonding orbital of C4 is directed more nearly toward facilities of XAL and M U R h and the financial the iron resulting in better metal-ligand overlap. support of this research by both the National Presumably, the local environment a t the other Science Foundation (Grant KO. 86.3474) and the terminal C7 atom to which a hydrogen is bonded Atomic Energy Commission (Contract N o . ATin place of a phenyl group is analogous to that of (11-1)-1121). C4. T o the extent that each of the terminal carbon (16) M. L. H. Green, L. P r a t t , a n d G. Wilkinson, i b i d . , 3753 atoms and its three attached neighbors are planar, (1959); 989 (1960). (17) R. Burton, L. P r a t t , a n d G. Wilkinson, 4290 (1960). the bending of the phenyl group (and the hydrogen) (18) G. Wilkinson, "Advances i n t h e Chemistry of t h e Coordination from the mean diene plane represent rotations Compounds," edited b y S. Kirschner, T h e blacmillan Co., Kew York, about the C4C5 and C&7 axes, respectively. X . Y . , 1961, p p . 50-64. Further analysis, however, shows that the Cd (19) See f o r example R. Burton, L. P r a t t , and G. Wilkinson, J . atom does not lie in the localized plane of its three Chem. Soc., 594 (1961); H . H . Hoehn, L. P r a t t , K. F. Watterson, and Wilkinson, J . Chem. Soc., 2738 (1961). bonded carbons; C4 is located approximately 0.22 G .(20) S a t i o n a l Science Foundation Fellow. A. above this plane (almost one-half of the disDEPARTMENT OF CHEMISTRY tance for a normal tetrahedral configuration). UNIVERSITY DOUGLAS L. SMITH~O OF WISCONSIN The central diene atoms, Cg (and presumably ( 2 5 ) ) are MADISON6, WISCONSIN LAWRESCE F. DAHL planar with their immediate neighbors. The RECEIVED MARCH15, 1962 combination of these rotations and deformations produces the dihedral angle a t C4 and Ci. This dihedral angle also has been observed in the unINSERTION OF DICHLOROCARBENE INTO substituted tr0pone-Fe(C0)3~and in both COTAROMATIC HYDROCARBONS Fe(C0)313,14 complexes for which the stereochemical Sir : disposition of the Fe(C0)3 fragment is similar. Although methylene, CH?, is sufficiently reactive The detailed representation of the bonding of the to insert in hydrocarbons, 1 dichlorocarbene has not syn-butadiene group as a four-electron donor system to the metal has been the subject of much previously been known to react in this manner. speculation. Hallam and Pauson'j first formulated A recent review2 states that halogen-substituted the widely-held view that the basic structure carbenes do not attack C-H bonds. 2H-1is a n-complex in which the conjugated diene system Benzothiopyrone reacts with dichl~rocarbene~to remains essentially unaltered and in which the give isomeric products t h a t apparently were formed four n-electrons utilized in bonding are delocalized. by insertion; here the sulfur atom probably acted as an electron donor to the electrophilic carbene (Y) R. P. Dodge and V. Sehomaker, private communication, 1961. and played an important role in the formation of (10) 0. S. Mills and G. Robinson, PYOC. Chem. Soc., 421 (1960); the final products. 0. S. Mills, private communication, 1961. (11) A. A. Hock and 0. S. Mills, ibid, 233 (1958); Acta Cryst., 14, 139 (1961). (12) R. P. Dodge a n d V. Schomaker, private communication, 1960. (13) B. Dickens and W N.Lipscomb, J . A m . Chem. Soc., 83, 489 (1961). (14) B. Dickens and W. N. Lipscomb, i b i d . , 83, 4862 (1961). (15) B. F. Hallam and P. L. Pauson, J . Chein. Soc., 642 (1958).
( 1 ) W. von E. Doering, R. G. Buttery, R . G . Laughlin, and N. Chandhuri, J . A m . Chem. Soc., 78, 3224 (1956); W . von E. Doering and H. Prinzbach, Telvahedi,on, 6, 24 (1959); D B. Richardson, M . C. Simmons, and 1. Dvoretzky, J . Anz. Chem. S o c . , 82, 5001 (1960). (2) W . Kirmse, Anrem. Chein , 73, 161 (1961). (3) W.E . Parham and Robert Kuncos, J . A m . Chem. Soc., 83, 1084 (1961).
COMMUNICATIONS TO THE EDITOR
May 5 , 19G2
REACTION PRODUCTS O F Hydrocarbon
Product
1715
TABLE I HYDROCARBONS WITH DICHLOROCARBEKE
AROMATIC Yield,
B.p.
%
OC.
mm .
17
57
24
,--Analyses,
70 (Calcd.) (Found)-
?$SOD
C
H
0.4
1.5351
57.1 56.8
5.3 4.9
3T.6 38.0
189 189
81
0.2
1.5279
63.6 63.4
7.3 7.0
29.0 29.3
245 245
39
110-111
0.9
1.5648
61.4 61.1
5.6 6.3
33.0 33.3
215 215
17
120-125*
0 5
CI
Mol. w t . a
H
HBC-C-CHCI~
Ethylbenzene
b
CHClz I HBC-C-CHJ
6
p-Diisopropylbenzene
H IC-C-CH, H
CHCil
Tetralin Hi
@-A@
Diphenylmethane
CHC12
66.9 4.8 28.3 251 66.7 4.6 28.5 251 Solidified; m.p. 78-79'; M. Delacre, Bull. SOC. a By mass spectrometry-weighted average of four isotope peaks. chim., (3) 13, 858 (1895), gives m.p. 80" for this compound made from dichloroacetaldehyde, benzene, and aluminum chloride.
Dichlorocarbene has now been found to react with alkyl-substituted aromatic hydrocarbons to give insertion products that have been identified by elemental analysis and infrared, nuclear magnetic resonance, and mass spectrometry. The reaction with cumene to give p,p-dichloro-t-butylbenzene is typical 7H3
7H3
CH3
A mixture of 1131.2 ml. (8 moles) of cumene, 556.7 g. (3 moles) of sodium trichloroacetate, and 75 ml. of 1,2-dimethoxyethane was stirred and refluxed until no more COZ evolved (12 hours). The mixture was filtered, the sodium chloride was washed with hexane, and the combined filtrate and hexane washings were distilled. Cumene, 750.8 g. (6.3 moles), was recovered, then p,pdichloro-t-butylbenzene was distilled at 68-70' and 3 mm. A total of 199 g. (0.98 mole) was obtained, %?OD 1.5400. This was a 33y0 yield based on sodium trichloroacetate. Anal. Calcd. for CloHlzCl?: C, 59.0; H , 5.9; C1, 35.0. Found: C, 58.8; H , 5.7; C1, 35.3. Nuclear magnetic resonance proved the structure H&?H3
c-c-c1 H
H H
AH3 C1
I
isotope masses; the major fragment on decomposition was formed by loss of CHClZ. The infrared absorption spectrum was similar to that of tbutylbenzene; i t had strong bands a t 10.5, 11.7, 12.9, and 13.8 p that were not present in t-butylbenzene. Reduction with sodium and alcohol gave t-butylbenzene boiling a t 16s-1 i o o , nzoD 1.4920, whose infrared spectrum was identical with that of an authentic sample. Under the same conditions, other hydrocarbons gave the products shown in Table I. Best yields resulted when the dichlorocarbene was generated by thermal decomposition of sodium trichl~roacetate~ ; by comparison, reaction of cumene with chloroform and potassium t-butoxide' or sodium methylate and ethyl trichloroacetate5 gave only 0.5 and 5yc yields of dichloro-tbutylbenzene, respectively. The additional thermal energy is evidently needed for the insertion reaction: the mechanism may not be identical with the normal carbene insertion mechanism. All of the dichloromethyl compounds, except that from diphenylmethane, are new; synthesis by any other route would be difficult. (4) W. M . Wagner, Pvoc. Chem. Soc., 229 (1959).
( 5 ) W. E . P a r h a m and E. E. Schweizer, J . O Y R . C h e m . , 34, 1733 (1959).
RESEARCH DEPARTMENT ELLISK. FIELDS AMOCOCHEMICALS CORPORATION WHITING,IKDIASA RECEIVED MARCH15, 1962
The sample was run neat, with hexamethylsiloxane A NEW SYNTHESIS OF 1,l-DIBROMOOLEFINS via PHOSPHINE-DIBROMOMETHYLENES. THE as 0. The 6-methyl hydrogens gave a sharp peak REACTION OF TRIPHENYLPHOSPHINE WITH a t 8.64 r , the peak for the lone hydrogen of the CARBON TETRABROMIDE dichloromethyl group was a t 4.38 T , and that for Sir: the five hydrogens on the benzene ring a t 2.87 r . The relative areas were 6 : 1:5 . Mass-spectroWhen triphenylphosphine (11) (0.1 mole) was metric analysis was wholly consistent with the added to a well stirred solution of carbon tetraproposed structure, p,P-dichloro-t-butylbenzene. bromide (I) (0.05 mole) in dry methylene chloride There was a strong parent peak a t 202 and a t the (250 ml. distilled from P205) an orange solution
