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Interaction between the Nonbonding Orbitals of -Dicarbonyl Systems and or Walsh Orbitals.

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Si(CH3)3 substituent (ca. 40)“) and a strain factor due to
the four membered ring (ca.
The high selectivity observed in electrophilic substitutions
lends itself to synthetic exploitation. Thus bromination of
(3) with bromine/pyridine (mol. ratio 2: 1) leads quantitatively
to 4-bromo-3-(trimethylsilyl)benzocyclobutene~51,
which on
reaction with iodine monochloride affords the compound
(9)[’1. Cyclobuta[l,2-c]benzyne ( 4 ) can be generated from
( 9 ) with n-butyl lithium and trapped with furan in 59%
yield as the colorless adduct (IO)[’l (m.p. 80--S1°C). So
far we have not been able to detect dimers derived from
(4).
Received: February 1, 1977 [ Z 690 IE]
German version: Angew. Chem. 89,413 (1977)
CAS Registry numbers:
( 3 ) , 62107-89-5; ( 4 ) , 62107-90-8; (S), 1578-34-3; ( 6 ) , 1066-54-2; (9), 6210791-9; ( l o ) , 62107-92-0; furan. 110-00-9
It is surprising, however, that the energy difference A(n)
is strongly influenced by double bonds or three-membered
rings separated by two CT bonds from the C 2 0 2 fragment.
This is shown by the PE spectra of the bicyclic a-diketones
(I )-(8)[31.
The experimental first PE bands of the compounds (1 )-(a)
are compiled in Table 1. A common feature is the almost
constant first ionization potential (8.7-9.2 eV) and a large
energy difference between the first and the second band. The
assignment is based on the validity of Koopmans’ theorem
( - B J = Iv,J)[~].
Both methods of calculation used predict the
same orbital sequence (MIND0/3[’] and EHc6’).
Table 1 . Comparison of measured vertical ionization potentials (Iv.,) and
orbital energies (a)of ( I ) t o ( 8 ) ; all values in eV.
-
Cpd.
I”.,
Band
An
Assignment
MIND013
An
- 9.12 (al)
- 10.40 (b,)
1.3
-
[I] W G. L. Aalbersberg, A . J . Barkouich, R. L. Funk, R. L. Hillard I I I ,
K . P. C. Volfhardt, J. Am. Chem. Sac. 97, 5600 (1975); R. L. Hillard
I I I , K . P . C . Volfhardr,in press.
[2] R. L. Hillard I l I , K . P . C . Vollhurdf,J. Am. Chem. Soc. 98, 3579 (1976);
R. L. Funk, K . P . C . I‘ull/m&, Angew. Chem. 88, 63 (1976); Angew.
Chem. Int. Ed. Engl. 15. 53 (1976).
[3] Prepared from the reaction of 1,s-hexadiynylmagnesium bromide with
trimethylsilyl chloride (29 %; b.p. 38-42”C/0.5 torr).
[4] L. Brandsma: Preparative Acetylene Chemistry, Elsevier, New York 1971.
[5] All new compounds gave satisfactory analytical and/or spectral data.
[6] A . R. Bassindale, C . Euborn, D. R. M . Walton. J. Chem. Soc. 81969,
12; C . Eaborn, D. R. M . Walfon, D. J . Young, ibid. B1969, 15.
Interaction between the Nonbonding Orbitals of
a-Dicarbonyl Systems and n or Walsh Orbitals[**]
By Rolf Gleiter, Richard Bartetzko, Peter Hofmann, and HansDieter Scharf“]
The interaction between the nonbonding orbitals nl and
n2 in 1,2-dicarbonyl systems is explained by a through-bond
mechanism[’]. On the basis of the photoelectron spectra (PE)
of glyoxal, biacetyl, and camphor quinone it could be shown
that the energy difference A(n)= je(n + ) - c(n -)I between the
linear combinations n, =(nl +n2)&‘5 and n- =(n, - n 2 ) f i
is almost independent of the alkyl substituents and of the
dihedral angle between the carbonyl groups; values of A(n)
are found between 1.6 and 2.0 eV.
I
2
3
9.0
10.5
11.2
1
2
3
4
8.9
10.5
10.8
11.55
1
2
3
4
8.9
10.3
10.7
11.5
1
2
3
4
5
8.7
10.3
10.5
10.9
11.8
1
2
3
9.0
10.5
11.2
1
2
3
4
8.7
10.6
11.1
12.1
1
2
3
9.2
11.5
11.7
1
2
3
4
8.9
10.8
11.7
12.0
1.5
- 10.84 (a2)
- 8.82 (a‘)
- 10.12 (a‘)
- 10.48 (a”)
- 1 1.00 (a”)
1.9
1.6
2.6
- 8.82 (a‘)
- 10.06 (a”)
- 10.22 (a’)
- 11.75 (a”)
2.93
3.1
- 8.69 (a’)
- 9.82 (a’)
- 1 0.12 (a“)
- 10.68 (a‘)
- 11.76 (a”)
3.07
- 8.99 (a’)
1.5
- 10.55 (a”)
- 11.29 (a”)
- 8.67 (a’)
- 10.28 (a’)
- 10.78 (a”)
- 1 1.52 (a”)
2.4
- 9.57 (a’)
- 10.73 (a”)
- 1 1.29 (a’)
2.3
- 8.69 (a’)
- 10.65 (a‘)
- 10.95 (a”)
- 11.57 (a’)
2.8
1.5
2.1
1.1
2.2
n+- n
- c
.*
[*I
Prof. Dr. R. Gleiter, Dipl.-lng. R. Bartetzko
Institut fur Organische Chemie der Technischen Hochschule
Petersenstrasse 22, D-6100 Darmstadt (Germany)
Dr. P. Hofmann
lnstitut fur Organische Chemie der Universitat Erlangen-Nurnberg
Henkestrasse 42. D-8520 Erlangen (Germany)
Prof. Dr. H.-D. Scharf
Institut fur Organ~scheChemie der Technischen Hochschule
Prof.-Pirlet-Strasse 1 , D-5100 Aachen (Germany)
I**] This work was supported by the Fonds der Chemischen Industrie.
400
Inductive
effect
*O
Fig. 1. Qualitative interaction diagram for the n + and n - orbitals of the
group and the x orbital in (2).
C202
Angew. Chrm. Iut. Ed. Engl. 16 (1977) No. 6
These results can readily be interpreted by assuming n +
to be above n - for the orbital sequence in the CzOz moiety
and a strong interaction between K - or Walsh orbitals and
n, and/or n-. In Figure 1 the orbital sequence in (2) is
explained as the result of an inductive effect of the double
bond on n, and n- and a homoconjugative interaction
between the TI and the Cz02 part.
Received: March I , 1977 [Z 687 IE]
German version: Angew. Chem. 89,414 (1977)
CAS Registry numbers:
(1),4216-89-1:(2).1754-68-1;(3),59952-76-8; ( 4 ) , 59896-73-0; (5), 6236-71I ; (6), 17994-26-2: (7), 59896-74-1 ; (81, 55058-68-9
2003 s, 1926 vs, respectively).-The 'H-NMR spectrum ([D6]acetone, - 30°C) diplays a multiplet for (2) at 6 = 7.55 ppm
which is assigned to the triphenylsilyl group; the corresponding
signal of (3) appears at 6=7.53ppm and is accompanied
by a singlet due to the cyclopentadienyl protons at 6 = 5.89 ppm
(intensity ratio 15:5).-The 13C-NMR spectrum of the two
complexes (Table 1) evidences the relatively strong deshielding
of the carbyne carbon atom, whose signal exhibits a considerable paramagnetic shift relative to arylcarbyne and alkylcarbyne complexes of tungsten['!
Table 1. l3C:'H]-NMR spectra of the cdrbyne complexes ( 2 ) and (31
in CD2CI2; 6 values in pprn, LS CD2C12=54.16ppm.
___-
['I
J . R . Swenson, R . Hoffinann, Helv. Chim. Acta 53, 2331 (1970); R . H o f manu, Acc. Chem. Res. 4, I (1971); R . Gleirer, Angew. Chem. 86, 770
(1974): Angew. Chem. Int. Ed. Engl. 13, 696 (1974).
P I D. 0.Cowan, R . Gleiter, J . A. Hashmull, E. Hrilhronner, V Hornung.
Angew. Chem. 83, 405 (1971); Angew. Chem. Int. Ed. Engl. 10, 401
(1971)
Dl H . D. Scharf, P. Friedrich, A . Linckens, Synthesis 1976, 256.
~ 4 17: Koopmuns, Physica (Utrecht) I , 104 (1934).
[51 R . Binyhuni, M . J . S. D w a r , D. H . Lo. J. Am. Chem. Soc. 97, 1285
(1975).
161 R . Hoffmunn, J . Chem. Phys.39,1397(1963); R . Hoffinann, W. N. Lipscomb,
ihtd. 36. 2179 (1962); 37, 2872 (1962).
Triphenylsilylcarbyne Complexes of Tungsten' '1
By Ernst Otto Fischer, Helmut Hollfelder, Peter Friedrick,
Fritz Rolund Kreissl, and Gottfried Huttner[*]
Having already prepared trans-bromotetracarbonyldiethylaminocarbynetungsten[*] with an electron-repelling substituent on the carbyne C atom, we now,describe the synthesis
of
trur?s-bromotetracarbonyltriphenylsilylcarbynetungsten
(2) and dicarbonylcyclopentadienyltriphenylsilylcarbynetungsten (3) as the first carbyne complexes containing an
electron-withdrawing hetero atomf3].
Reaction of pentacarbonylmethoxy(triphenylsi1yl)carbenetungsten ( 1 )I4]with aluminum bromide under mild conditions
affords (2) as ivory-colored diamagnetic crystals which dissolve readily in dichloromethane but only moderately well
in n-pentane.
(2)
(3)
w-c
co
ChHs
337.14
(146.5) [a]
354.29
(178.2) [a]
192.57
(131.8) [a]
222.24
(202.6) [a]
135.72
130.75
135.93
130.00
CsHS
131.73
128.60
134.32
128.27
Measuring
temp. r C ]
- 40
92.56
-20
[a] ' J ( 1 R 3 W - 1 3 Cin) Hz for satellites.
Although the spectroscopic data prove that (3) has basically
the same structure as already confirmed by X-ray studies
for other cyclopentadienyldicarbonyltungsten-carbynecomplexesl6I, X-ray analysisf71of (3) was undertaken in order to
establish whether the triphenylsilyl substituent has a recognizable influence on the W-Ccarbyne bond length (Fig. 1).
The pseudooctahedral structure expected for (3) was confirmed. The W-Ccarbyne distance of 181(2)pm is just as long
as that in C5H5(CO)2WC-C6H4CH3 ( 4 ) (182(2)pm16a1);
exchange of the p-tolyl group in ( 4 ) for the triphenylsilyl
group in (3) apparently causes no change in the W-Ccsrbyne
bond length. As in ( 4 ) , the central group W=C-R
is
almost linear (l76(1)"). Within the limits of experimental
accuracy all the S i c bonds in (3) are of equal length. Compared with a CSp-Si single bond (181 pmLE1)
the Ccarbyne-Si
bond length of 187(2rpm appears somewhat elongated; however, the effect is by no means so pronounced as in ( C 0 ) K r [C(0Et)(SiPh3)]I4], for which a Cq,2-Si distance of 200(2)pm
was found.
rrans-Br(CO)IW-C-Si(C6H5j3+ C o +. . .
(2)
The complex (2) reacts with sodium cyclopentadienide in
tetrahydrofuran (evolution of CO, deepening of color) to give
(3) as orange diamagnetic crystals which are readily soluble
in ether and dichloromethane.
(2) + NaC,H,
TH F
- 78 "C
rr-CSH,(C0)2W=C-Si(C6H5), + N a B r + 2 C O
(31
The IR spectra of (2) and (3) (CH2Cl2;cm-') show the
expected vibrations in the vCO region (2132w, 2052vs and
[*] Prof. Dr. E. 0. Fischer. DipLChem. H. Hollfelder, Dipl.-Chem. P. Friedrich, Dr. F. R. Kreissl, Doz. Dr. G . Huttner
Anorganisch-chemisches lnstitut der Technischen Universitdt
Arcisstrasse 21, D-X000 Miinchen 2 (Germany)
A n g e n . Chem. I f i f . Ed. Enql. 16 (1977) N o . 6
Fig. 1. Molecular structure of a-CsHs(CO)zW~C-Si(CsHs), (3).
Procedure
All operations should be performed under N2 and with
dried (Na, P ~ O I O
and
) N2-saturated solvents.
(2): An excess of &Br6 is added to a stirred solution
of ( I ) (1.57g, 2.5mmol) in toluene (30ml) at -78°C. On
401
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