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MO Calculations on the Insertion Reactions of Vinyl Cations.

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phenylacetylene with aniline and phenylisocyanate, respectively. In the former case, N-phenyl-2,3-diphenylsuccinimide (20-30%) is obtained as major product apart from
a trace amount of (1a ) ,while from the latter conversion the
only product thus far isolated consists of a high melting
(> 300°C)crystalline compound, which has not yet been
identified.
MO Calculations on the Insertion Reactions of
Vinvl Cations[**]
By Herbert Kollmar and Harry 0.Smith"]
The chemistry of vinyl cations and related species"] is
characterized by rearrangements and additions to unsatu-
Table 1. Compounds prepared by the reaction of diphenylacetylene with aromatic nitro compounds and carbon
monoxide in the presence of carbonyl rhodium.
R
'H-NMR Chemical Shift
S(ppm) [d]
aromatic
methyl
IR ('CO)
( P) Tcl
(la)
H
75
175 [el
5.67
5.85
6.85-7.7
(Ibl
P-CH,
77
192- 194 [q
5.68
5.85
7.0 -7.7
2.38
(Icl
m-CH,
77
160-161
5.70
5.88
6.9 7.7
2.37
75
145- 146
5.68
5.83
7.0 -7.7
50
188- 189
5.68
5.85
6.85-7.7
244-246
5.70
5.81
7.2 -7.9
(lei
p-OCH,
(1 fl
P-C,H,
[a]
[b]
[c]
[d]
[el
[fl
80-85
3.78
Crude yield, based on diphenylacetylene.
Melting points are uncorrected.
KBr disc.
Measured in CDCI,.
174-175°C after Ref. [8].
192-C after Ref. 161.
In view of these findings we tend to rule out intermediacy
of amine or isocyanate in the direct formation of (1) from
diphenylacetylene and nitro compounds. In analogy to
related cases['* 3. we believe in intervention of some sort
of a nitrenoid species originating from the nitro component.
rated systemsr2*
'I. M O calculations, however, predict that
such ions should also be able to participate in insertion
reactions, in analogy to the well-known insertions of carbenes. The simplest example of such a reaction is the addition of the vinyl cation to the hydrogen molecule to form
the ethyl cation :
N-(p-Biphenytyl)-2,3-diphenylmaleimide
( 1 f):
A solution of diphenylacetylene (0.005 mol), p-nitrobiphenyl (0.0055mol) and hexadecacarbonylhexarhodium[7~
(lo-' mol) in anhydrous pyridine (6ml) was allowed to
react with carbon monoxide (150atm) in a stainless steel
autoclave (30ml capacity) at 165-170°C (external temperature) for 3 hours. After cooling to room temperature,
the autoclave was discharged and pyridine removed in
U~CUO
at 50 "C. The residue was swirled with 10-1 5 rnl of
(If) in 80-85 % yield, m. p. 24-246 "C.
Received: February 1,1972 [Z 647 IE]
German version : Angew. Chem. 84, 641 (1972)
[I] Part 4 of Catalytic Deoxygenation of Organic Compounds by
Carbon Monoxide.-Part 3: [2].
[2] A . F. M . Iqbal, Helv. Chim. Acta 55, 798 (1972).
[3] A . F. M . Iqbal, J. Org. Chemistry, in press.
[4] I: Kajimoto and J. Tsuji, Bull. Chem. SOC.Japan 42, 827 (1969).
[5] A . F. M . Iqbal, Tetrahedron Lett. 1971,3385.
[ 6 ] G. Gysae, Ber. dtsch. chem. Ges. 26, 2478 (1893), cf. also [S].
[7] B. L. Booth, M . J. Else, R. Fields, H. Goldwhite, and R. N . Haszeldine, J. Organometal. Chem. 14, 417 (1968).
[8] R . Anschiitz and P . Bendix, Liebigs Ann. Chem. 259, 65 (1890).
Angew. Chem. internat. Edit./ Vo1. I 1 (1972) / No. 7
The reverse of (1) is observed in mass spectrometry as a
fragmentation reaction[41.We have studied this example
in some detail.
A
CNDOL6]
method was used which allows the
complete minimization of the energy of a molecule with
respect to its geometry and thus is particularly well suited
to the calculation of reaction coordinate^[^].
The vinyl cation has an almost empty p orbital (p, in Fig.
la) perpendicular to the x bond orbital. The x orbital is
strongly polarized ;hence the vinyl cation can be described
as a methylene with CH; as a substituent. Various modes
of H, addition are conceivable in reaction (1). For instance,
the H, molecule could approach the occupied x orbital
of the C,Hl ion from the side (Fig. Ic). This is a very
[*] Dr. H. Kollmar
Battelle-Institut e. V.
6 Frankfurt 90, Postfach 900160 (Germany)
Dr. H. 0. Smith
Max-Planck-Institut fur Medizinische Forschung
69 Heidelberg, Jahnstrasse 29 (Germany)
First commhnication of MO calculations on electrophilic reactions.
[**I
635
unfavorable reaction path because two occupied orbitals
are forced to interact with each other. (Assuming C,
symmetry, this path is forbidden according to the Woodward Hoffmann rules”4J). On the other hand, the approach
of H, along the empty px orbital (Fig. 1b), leading initially
to a three-center bond, should be energetically more favorable[**91.
m
al
bl
of 1.3 A. The decrease at smaller distances is due to rehybridization. Similarly, the bond order between the two H
atoms of the approaching H, molecu!e sinks continuously
from 1at infinitedistance to0.6at 1.3A.At this point it then
drops sharply to almost 0 due to the admixture of the
antibonding H, orbital to an occupied orbital in the second
phase of the addition.
CI
Fig. 1. Addition of H, to the vinyl cation.
The ethyl cation formed, of course, normal C-H bonds
and not three-center bonds. As demonstrated in Fig. 2,
however, two uicinal C-H bonds can be described by a
linear combination of two three-center bonds. The calculations show that these three-center bonds are formed
consecutively during the course of the reaction.
1 .o
1 .5
RC-” [dl
Ill H;p
1.21 H-H
2 .a
I
2.5
ma
Fig. 3. Changes in the electronic structure during reaction (I).
Lzsfio.zI
Fig. 2 Representatlon of C-H
of three-center bonds.
bond orbitals as a linear combination
The detailed results of the calculations of the reaction
path for reaction (1) are as follows: The reaction proceeds
with relatively little Fctivation energy (9 kcal/mol at a
C-H distance of 2.3 A). A H , for the addition is calculated
to be 46 kcal/mol (experimental value 60 kcal/mol[lO1).An
interesting result is that the reaction proceeds in two easily
discernable steps :
The reaction coordinate is also affected by the two-phase
mechanis? (Fig. 4).The H-H distance remain: relatively
small (0.9 A) down to a C-H distance of 1.3 A and then
increases rapidly with further sh:rtening of the new C-H
bond to the final value of 1.85 A. At intermediate C-H
distances (1.25-1.4 A) there exist two local energy minima
at different H-H distances. Above 1.3A the minimum
with a short H-H bond is energetically more favorab!e.
This order is reversed at shorter C-H distances ( I 1.25 A).
1. In the first step a three-center bond is formed between
the H atoms and the empty px orbital (“electrophilic phase
of the reaction”). This step is analogous to the electrophilic
addition of carbenium ions to saturated C-H and C-C
bonds, which can be observed in highly acidic solutions1g1.
The prototype reaction is the addition of H, to CH; to
form the CH: cation, which, according to MO calculations,
should proceed without activation energy[”].
2. In the :econd step, beginning at a C-H distance of
about 1.3 A, the antibonding orbital of H, combines with
the occupied n orbital of the vinyl cation to form the second
three-center bond. The H-H distance becomes larger
and the geometric structure of the product is obtained.
This phase of the reaction corresponds to the characteristic
breaking of the bond of the substrate during an insertion
process (the “nucleophilic phase”, involving the occupied
n orbital of the vinyl cation).
The two-phase mechanism is reflected in the changes of the
parameters describing the electronic structure along the
reaction coordinate. Figure 2 shows the change in the
bond order between the originally empty px orbital of the
vinyl cation and the I s orbital of an approaching H atom
as a function of the C-H distance. During the formation
of the first three-center bond, this bond order increases
from 0 at infinite distance to about 0.5 at a C-H distance
636
Fig. 4. The energy as a function of the H-H
distances.
distance at constant C-H
The two-phase mechanism does not entail any steric
consequences (and thus chemical repercussions) in this
case. Such effects become important in the analogous
insertion reactions of carbenest’2*13!
Received: February 18,1972 [Z 650 IE]
revised : March 17, 1972
German version: Angew. Chem. 84,680 (1972)
[l] G. Modena and U . Tonellato, Advan. Phys. Org. Chem. 9, 185
(1971).
Angew. Chem. internat. Edit. Val. 11 (1972) 1 No. 7
[2] A . E . Lodder, H.M . Buck, and L. J . OosterhofL Recl. Trav. Chim.
Pays-Bas 89,1229 (1970); H.Hogewen and C. F . Roobeek, Tetrahedron
Lett. 1971, 3343.
[3] H.-U. Wagner and R. Gompper, Tetrahedron Lett. 1971,4061,4065.
[4] M . Vestal and J . H.Futrell, J. Chem. Phys. 52,978 (1970).
[5] H . Fischer and H . Kollmar, Theoret. Chim. Acta 13,213 (1969).
[6] J . A . Pople, D. P. Santry, and G . A . Segal, J. Chem. Phys. 43, S 129
(1965).
[7] H . Kollmar, Battelle Inform. 1971, No. 10, 10.
[8] H. Kollmar and H.0. Smith, Theoret. Chim. Acta 20, 65 (1971).
191 G. A . Olah, I! Halpern, J . Shen, and I!K. Mo, J. Amer. Chem. SOC.
93, 1251 (1971).
[lo] J . L. Franklin et al.: Ionization Potentials, Appearance Potentials
and Heats of Formation of Gaseous Positive Ions. National Bureau of
Standards, Nat. Stand. Ref. Data Svcs., No. 26, Washington 1969.
[11] H. Kollmar and H . 0. Smith, Chem. Phys. Lett. 5,7 (1970).
[12] R . C. Dobson, D. M . Hayes, and R . Hoffmann, J, Amer. Chem. Sac.
93, 6188 (1971).
I131 H. Kollmnr, Tetrahedron, in press.
[14] R . B. Woodward and R . Hoffmann, Angew. Chem. 81, 797 (1969);
Angew. Chem. internat. Edit. 8, 781 (1969).
Dimethylene(2-propenylidene)methanetricarbonyliron"]
By U!Edward Billups, Lee-Phone Lin, and Otto A. Gunsow"]
Reactions of carbonyliron complexes with compounds
whose structural features incorporate the vinylcyclopropane or methylenecyclopropane grouping are of current
interest.
Thus the reaction of Fe,(CO), with cyclopropylstyrenecza.b1 or spir0[2.4]hepta-4,6-diene[~'] gives substituted
1,3-diene-Fe(CO), complexes, whereas bullvalene[2e1and
semibullvalene[2f1give complexes resulting from cleavage
of the cyclopropane ring with formation of both a.n-ally1
and a CT component bound to the Fe(CO), unit. Methylenecjclopropane[2d1also gives a low yield of butadienetricarbonyliron upon reaction with Fe2(C0)9; however,
methylenecyclopropanes bearing a phenyl or methyl substituent on C-2 give trimethylenemethane-coordinated
products[2d1.
Methylene(viny1)cyclopropane ( I ) 13] is a molecule that
incorporates both these functionalities and the present
communication reports on a stable iron complex dimethylene(2-propeny1idene)methanetricarbonyliron(2) derived
from ( I ) and Fe,(CO),.
Table 1. 'H-NMR parameters of (2) determined at 60 MHz and relative
to TMS.
H-1
H-2
H-3
H-4
H-5
H-6 to H-8
3.67 (d, d)
1.80 (d)
1.79 ( s )
2.18 (m)
2.66 (d)
4.83-6.03 (m)
J l , 6= 9.7; J1,.,= 2.1
= 4.3
J 2 , 5 = 4.3
ing evidence for the proposed structure. In addition, the decoupled 13C-NMR spectrum of (2) at ambient probe
temperature shows seven distinct signals (Fig. 1). Two 13C
resonances may be immediately identified as due to the
carbonyl carbon and the central carbon of the trimethylene-51.9
-52.5
-118.7
-105*2+)0
-137.6
-51.9 T - 8 0 . 2
-52.5
Fe(CO),-214.8
Fig. 1. Chemical shifts are in pprn relative to TMS = 0.
methane ligand by simple chemical shift[41and signal
intensity considerations. The two methylene resonances
at -51.9 and -52.5 ppm are quite near those observed
for trimethylenemethanetri~arbonyliron[~~,
while those at
- 137.6 and - 118.7 ppm are near the resonances of the
vinyl group of compound ( I ) .
Received: May 8, 1972 [Z 653 IE]
German version: Angew. Chem. 84,684 (1972)
[1] This work was supported by the Robert A. Welch Foundation and
the Petroleum Research Fund administered by the American Chemical
Society.
[2] a) S.Sarel, R . Ben-Shoshan, and 8. Kirson, J. Amer. Chem. SOC.87,
2517 (1965); b) R . Ben-Shoshan and S . Sarel, Chem. Commun. 1969,883;
c) C. H . Depuy, !J M . Kobal, and D. H.Gibson, 3. Organometal. Chem.
13,266 (1968); d) R . Noyori, 7: Nishimura, and H. Takya, Chem. Commun. 1969, 89; e) R . Aumann, Angew. Chem. 83, 175, 176, 177 (1971);
Angew. Chem. internat. Edit. 10,188,189,190 (1971); f) R . M . Moriarty,
C. L. Yeh, and K. C. Ramey, J. Amer. Chem. SOC.93,6709 (1971).
[3] 7: C. Shields, W E. Billups, and A . R. Lepley, J. Amer. Chem. SOC.
90,4749 (1968).
[4] G. F . Emerson, K . Ehrlich, W P. Giering, and P . C. Lauterbur, J.
Amer. Chem. SOC.88,3172 (1966).
Three Isomerization Routes Originating from
Different Electronic States of a LinearlyConjugated Cyclohexadienonerll["'l
By Gerhard Quinkert, Bernd Bronstert,
and Klaus R. Schmieder"'
Complex (2) is prepared (43% yield) by stirring a 1 : l
mixture of ( I ) and Fe,(CO), in benzene at 35-40°C for
2 h. After removal of benzene, bulb to bulb distillation at
92"C/2.5 torr gives ( 2 ) as a deep green oil whose composition was shown to be C,H,Fe(CO), by its mass
spectrum (parent molecular ion m/e 220). The infrared
spectrum shows CEO absorptions at 2048 and 1984cm- l.
The 'H-NMR spectrum (Table 1)of (2) provides convinc-
[*I Dr. W. E. Billups, Lee-Phone Lin, and Dr. 0. A. Gansow
Department of Chemistry
Rice University
Houston, Texas 77001 (USA)
Angew. Chem. internat. Edit. 1 Vol. I1 (1972)
1 No. 7
Comparative chemistry is directed towards the elucidation
of the reaction paths starting from different electronic
states of a compound"]. The chiral but racemic 6-acetoxy-
["I, and
Dip1.-Chem. K. R. Schmieder
Institut fur Organische Chemie der Universitat
6 Frankfurt, Robert-Mayer-Str. 7-9 (Germany)
[**I Now: Badische Anilin- & Soda-Fabrik AG, 67 Ludwigshafen
(Germany)
[***I The work was supported by Farbwerke Hoechst AG, the Deutsche
Forschungsgemeinschaft, and the Fonds der Chemischen Industrie.
K. R. Sch. thanks Schering AG for a grant.
[*] Prof. Dr. G. Quinkert, Dr. B. Bronstert
637
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