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Metallacyclic Four-Membered Ring Systems Two Independent Routes to Bis(cyclopentadienyl)titanacyclobutabenzene.

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1121 We estimate, based o n M-M distances in similar clusters of d-transition
elements [Ib, 21, a U-U distance of 3.5 to be an upper limit for a bonding interaction. I n a dinuclear uranium alkoxide with a U-U separation
of 3.63 8, the interaction I S clearly repulsive (F. A. Cotton, D. 0. Marler,
W. Schwotzer, Inorg. Chem. 23 (1984) 4211).
[I31 F. A. Cotton, W. Schwotzer, J. Am. Chern. SOC..in press.
[I41 J. G Brennan, R. A. Andersen, J. L. Robbins, J . Am. Chem. SOC. 108
(1986) 335.
[IS] G. M. Smith, H. Suzuki, D. C. Sonnenberger, V. W. Day, T. J. Marks,
Organornefallics 5 (1986) 549.
1161 a) J. M. Ritchey, A. J. Zozulin, D. A. Wrobleski, R. R. Ryan, H. J. Wasserman, D. C. Moody, R. T. Paine, J . Am. Chem. SOC.107 (1985) 501; b)
P. J. Hay, R. R. Ryan, K. V. Salazar, D. A. Wrobleski, A. L. Sattelberger,
ibid. 108 (1986) 313; c) R. S. Sternal, C. P. Brock, T. J. Marks, h i d . 107
(1985) 8270.
A
Metallacyclic Four-Membered Ring Systems:
Two Independent Routes to
Bis(cyclopentadienyl)titanacyclobutabenzene* *
By Henricus J . R . de Boer, Otto S. Akkermann,
Friedrich Bickelhaupt,* Gerhard Erker, * Peter Czisch,
Richard Mynott, Julian M . Wallis, and Carl Kriiger
Metallacyclobutanes of the early transition metals['] are
accessible via two routes (Scheme 1): by reaction of metal
halides with suitably substituted 1,3-propanediyl dianionequivalents [route (a)]''] or by the electrocyclic ring closure
of carbene(o1efin)metal complexes. The latter are usually
obtained by reaction of carbene-metal complexes with olefins [route (b)]J'cl but more recently they have been prepared from organic alkylidene donors and reactive olefinmetal complexes [route (c)].I3] We have now found that
otherwise difficultly and rarely accessible metallacyclobutabenzene compounds[41 can be prepared by variants of
routes (a) and (c). We have been able to demonstrate this,
for example, in the case of bis(cyclopentadieny1)titanacyclobutabenzene 13a.
10
R
A
+Ph-R
2
R
<R
= CMe,
,
3
13a
The novel, double Grignard reagent 11 was obtained by
reaction of o-bromobenzyl chloride with magnesium in tetrahydrofuran (THF). Reaction of a T H F suspension of l l
with Cp2TiCI2(12, equimolar amount) at -20°C afforded
13a can, however, also
the titanacyclobutabenzene 13a.L51
be prepared via the cycloaddition route (c) (Scheme I).
(Aryne)ZrCp, 15b, generated thermally from diphenylzirconocene, reacts with CH2=PPh3 to give the metallocenesubstituted ylide 17b.i61In the analogous titanocene system, transfer of the entire methylene group of the reagent
with formation of 13a and PPh, competes with H-transfer
(17a : 13a = 2 :I)."] A labeling experiment showed that
both of the products are formed by an aryne mechanism[*]
(Scheme 2).
14
1
11
II
17
17'
7OoC
- Ph - R
4
SIMQ
.-
I
/-PPh3
\L
1
CP2M&
/
a,M=TI, b , M = Z r ,
R = H I CH,
R
6
13
13'
Scheme 2. The (non-systematical) numbering merely serves for assignment of
the NMR signals.
8
9
Scheme I
[*I
[ '1
I**]
Prof. Dr. F. Bickelhaupt, Dr. H. J. R. d e Boer, Dr. 0. S. Akkerman
Scheikundig Laboratorium, Vrije Universiteit Amsterdam
De Boelelaan 1083, NL-I081 HV Amsterdam (The Netherlands)
Prof. Dr. G. Erker [+I, DipLChem. P. Czisch, Dr. R. Mynott,
Dr. 1. M. Wallis, Prof. Dr. C. Kriiger
Max-Planck-Institut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim a. d. Ruhr (FRG)
Present address:
lnstitut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wiirzburg (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chernischen Industrie ( C . E.), and by the Netherlands
Foundation for Research (SON) and the Netherlands Organization for
the Advancement of Pure Research (ZWO) ( H . J . R . de B.).
Angew. Chem. Inr. Ed. Engl. 25 (1986) No.
7
17a was characterized by an X-ray structure analysis
(Fig.
Like 17b, in the crystal it exhibits a preferred
conformation that allows for maxima1 n-interaction of the
formally coordinatively unsaturated metal center"" with
the trigonal-planar ylide carbon atom. The TiLC7 bond
length (2.033(6) A) is remarkably short.["] The metalC(y1ide) n-interaction in the titanium compound 17a
(Ad(M)=d[M-Cll-d[M-C7]; Ad(Ti)=0.22 A) is stronGer
than in the zirconium compound 17b (Ad(Zr)=0.18 A).
17a and 17b show dynamic N M R spectra in solution: In
17a the activation barrier for rotation about the M-C7
bond (AG ?34.c = 12.0f 0.2 kcal/mol) is considerably
higher than in the case of 17b (AG? , 0 2 - c = 8.6 k 0.3 kcall
mo1),i61suggesting a stronger n-interaction in 17a. The methylene transfer to give 13 would be favored by a similarly
enhanced M-C n-interaction in the intermediate 16.
0 VCH Verlagsgesellschaft mbH. 0-6940 Weinheim. 1986
0570-0833/86/0707-0639 $ 02.50i0
639
I51 13a: MS (70 ev): m/z 268 (M'), 178 (Cp2Ti): 'H-NMR (for numbering
,
(s, 2 H ; C H 2 ) ,
see Scheme I ) : 6 (CD2C12)=5.85 (s, 1OH: C 5 H S ) 3.17
+E+&
cz
CP5
Fig. I Crystal structure of 17a. R = H
Experimental
A suspension of dovbly sublimed magnesium (576 mg, 24 mmol, particle size
1-2 mm) in T H F (4 mL) was treated with dibromoethane (21 mg, 0.1 mmol),
and the mixture stirred for 15 min. A solution of 10 (492 mg, 2.4 mmol)'I2' in
T H F (30 mL) was then added dropwise to the mixture within 2 h, and stirring
continued for a further 1 h. To remove excess magnesium, the mixture was
filtered through glass wool. This furnished a suspension of a green precipitate in a greenish-yellow solution, with the precipitate containing the greater
part of the organomagnesium compound. The yield of 11 was almost quantitative. This was ascertained by hydrolysis and titration of the base and the
magnesium ions with HCI and ethylenediamine tetraacetate (EDTA), respectively, and by determination of the a,o-dideuteriotoluene (99%) after deuteriolysis (GC/MS). Derivatization with C 0 2 , Me,GeCI, and Me,SnCI also afforded the expected disubstitution products in 92-94% yield.
For the synthesis of 13a, 12 (198 mg, 0.795 mmol) was added to a THFsuspension of a molar equivalent of 11 (0.0199 M) at -20°C in a sealed glass
system and stirred for 2 h. The grey precipitate dissolved and a deep red
solution resulted. After removal of the T H F by distillation at 4°C the solution was treated with dioxane (10 mL): after 15 minutes' stirring and removal
of a white precipitate (magnesium salts), the filtrate was evaporated to dryness. The residue was virtually pure 13a (red powder; 93% yield, determined
by 'H-NMR spectroscopy with cyclopentane as standard).
Received: March 4. 1986;
revised: May 15, 1986 [ Z 1690 IE]
German version: Angew. Chem. 98 (1986) 641
[ I ] a) J. B. Lee, G. L. Gajda, W. P. Schaefer, T. R. Howard, T. Ikariya, D. A.
Straus, R. H. Grubbs, J . Am. Chem. Soc. 103 (1981) 7358; A. K. Rappe,
W A. Goddard 111, ibid. 104 (1982) 297; W. R. Tikkanen, J. W. Egan, Jr.,
J. L. Petersen, Organometallics 3 (1984) 1646; b) F. N. Tebbe, G. W.
Parshall, D. W. Ovenall, J . Am. Chem. SOC.I01 (1979) 5074; T. R. Howard, J. B. Lee, R. H. Grubbs ,;bid. 102 (1980) 6876: D. A. Straus, R. H.
Grubbs, J . Mol. Cutal. 28 (1985) 9; c) K. A. Brown-Wensley, S. L. Buchwald, L. Cannizzo, L. Clawson, S. Ho, D. Meinhardt, J. R. Stille, D.
Straus, R. H. Grubbs, Pure Appl. Chem. 58 (1983) 1733, and references
cited therein.
[2] a) J. W. F. L. Seetz, B. J. J. van de Heisteeg, G. Schat, 0. S. Akkerman,
F. Bickelhaupt, J . Mol. Catul. 28 (1985) 71, and references cited therein:
B. 1. J. van d e Heisteeg, G. Schat, 0. S. Akkerman, F. Bickelhaupt, Tetrahedron Lett. 25 (1984) 5191; Orgonometallics4 (1985) 1141; b) W. R.
Tikkanen, J. Z . Liu, J. W. Egan, Jr., J. L. Petersen, ibid. 3 (1984) 825: c)
for other modes of formation of metallacyclobutanes see, e.g., P. Foley,
G. M. Whitesides, J. Am. Chem. Soc. 101 (1979) 2732: M. Ephritikhine,
M. L. H. Green, R. E. MacKenzie, J . Chem. SOC.Chem. Commun. 1976.
619.
[3] G. Erker, P. Czisch, C. Kriiger, J. M. Wallis, Organometallics 4 (1985)
2059.
[4] T. H. Tulip, D. L. Thorn, J . Am. Chem. SOC.103 (1981) 2448; L. Dahlenburg, V. Sinnwell, D. Thoennes, Chem. Ber. 111 (1978) 3367; V. F. Traven, M. Yu. Eismont, V. V. Redchenko, B. 1. Stepanov, Zh. Obshch. Khim.
50 (1980) 2007; Chem. Abstr. 94 (1981) 29681 2: T. Behling, G. S. Girolami, G. Wilkinson, R. G. Somerville, M. B. Hursthouse, J. Chem. SOC.
Dolron Trans. 1984, 877; J. A. Stotler, G. Wilkinson, M. Thornton-Pett,
M 8. Hursthouse, ibid. 1731; R. Neidlein, A. Rufinska, H. Schwager, G.
Wilke, Angew. Chem. 98 (1986) 643; Angew. Chem. Int Ed. Engl 25
(1986) 640.
640
0 VCH Verlagsgesellschafr mbH. 0-6940 Wernherm, 1986
7.06, 7.28 (d, in each case 'Jblc,=7 Hz, each I H: H3. H6), 6.90 (m, 2 H ;
H4, H 5 ) : 6 (ChD6)=5.50 (CSH,), 3.30 (CH2); "C-NMR (CD2C12):
6 - I 11.8 (d, 'Jcli= 174 Hz; CSHS),63.4 (t. ' J ~ H = 140 Hz: CHZ), 105.1 ( s ;
CI), 208.9 (s; a),
128.9 (d; C6). 132.6 (d, 'JcBt= 157 Hz: C3), 125.5,
125.2 (d, 'Jcli= 158 Hz; C4, C5).
161 a) G. Erker, P. Czisch, R. Mynott, Y:H. Tsay, C. Kruger, Organometallics 4 (1985) 13 10: b) for further examples of this type of compound see:
G. Erker, P. Czisch, R. Mynott, Z . Naturforsch. B 4 0 (1985) 1177; H.
Schmidbaur, R. Pichl, ibid. 352; R. E. Cramer, R. B. Maynard, J. W.
Gilje, Inorg. Chem. 20 (1981) 2466: K. 1. Cell, J. Schwartz, ibid. 19
(1980) 3207; c) J. C. Baldwin, N. L. Keder, C. F. Strouse, W. C. Kaska,
Z . Naturforsch. 835 (1980) 1289.
171 A mixture of 3.6g (10.9 mmol) of Cp2TiPh2 and 3 3 g (12 mmol) of
H2C=PPh, in 250 mL of heptane after heating at 70°C for 7 h and subsequent crystallization afforded 3.6g (95%) of pure 17a. The solution
contained u p to 80-90% of pure 13a together with PPh, ( 1 : 1). 17a: M.p.
163°C; correct elemental analysis: MS (70 ev): m / z 530 (Ma), 453
(M' - Ph), 275 (CHPPh?): IR (KBr): 5=3040, 1430, 1100, 800 (C,H,),
920 (C-P) c m - ' ; 'H-NMR (C,D,, for numbering see Scheme I ) :
6=5.71 (5, IOH: CsHs), 8.78 (d, ' J H P =Hz,
~ 1 H; CH=P), 6.85-7.20 and
7.40-7.85 (m. 20H; 4C6H,); "C-NMR (CD2C12): 6=108.8 (d,
' J c H = 173 Hz; CSH,), 165.2 (dd, 'JcH= 122 Hz, 'Jcp=20 Hz; CH=P),
187.7 (S; CI), 144.0 (d, ' J c H = 156 Hz; C2), 125.5 (d, ' J , - H = 153 Hz; C3),
121.5 (d, 'JCH=
157 Hz; C4). signals of the PPh, group: 6 = 133.7 (d,
'Jcp=80.5 Hz; i-C), 133.7 (dd, ' J C - H = 163 Hz, *Jcp=9 2 Hz; 0-c), 128.8
(dd, ' J c H = l 6 3 Hz, ' J c ~ , = I l . l Hz; m-C), 131.4 (dd, IJrH=160 Hz,
4Jrp=2.6 Hz; p-C).
181 Starting from bis@-tolyl)titanocene, the aryltitanocene ylides 17a (methyl at C3) and 17a' (methyl at C4) were obtained in a 60:40 ratio together with a mixture of the substituted titanacyclobutabenzenes 13a
(methyl at C5) and 13a' (methyl at C4). I n this particular case, H-transfer is favored over CH,-transfer to the extent of 3 : I .
[9] crystal structure analysis of 17a : a = l0.872( I), b = 17.928(3),
c=28.643(4)A: V=5583.1 A3;p,,,,,=1.26 g cm-'.p=3.79 c m - ' , Z = 8 ;
space group Pbca, 2151 of 6290 independent reflections observed, 458
parameters refined, R = 0.049, R , =0.042. Selected bond lengths [A] and
angles ["I: Ti-CI 2.254(5), Ti-C7 2.033(6), P-C7 1709(6); CI-Ti-C7
95.5(2), Ti-C7-P 138.5(3): C6-CI-Ti-C7 31.5, CI-Ti-C7-P 99.5. Further
details of the crystal structure investigation are available on request
from the Fachinformationszentrum Energie, Physik, Mathematik
GmbH, D-75 14 Eggenstein-Leopoldshafen2, on quoting the depository
number CSD-51937, the names of the authors, and the full citation of
the journal.
[lo] For the special stereoelectronic properties of the bent metallocene
moiety see J. W. Lauher, R. Hoffmann, J. Am. Chem SOC.98 (1976)
1729; C Erker, F. Rosenfeldt, Angew. Chem. 90 (1978) 640; Angew.
Chem. I n / . Ed. Engl. 17 (1978) 605.
[l I] Almost identical with d(Ti-C) in dicdrbonyltitanocene (2.030(1 1)
J.
L. Atwood, K. E. Stone, H. G. Alt, D. C. Hrncir, M. D Rausch, J. Organomef. Chem. 132 (1977) 367; Ti-C bond lengths: W. E. Hunter, J. L.
Atwood, G. Fachinetti, C. Floriani, ibid. 204 (1981) 67: I. W. Bassi, G.
Allegra, R. Scordamaglia, G. Chiccola, J. Am. Chem. Sot. 93 (1971)
3787: J. L. Calderon, F. A. Cotton, B. G. De Boer, J. Takats, ibid. 3592;
G. P. Pez, ibid. 98 (1976) 8072.
[I21 Prepared from o-bromobenzyl alcohol according to the method described by D. Landin, F. Monetari, F. Rolla, Synthestr 1974, 37.
A):
Nickelacyclobutabenzene Compounds by
Oxidative Addition of Cyclopropabenzene to
Nickel(o) Compounds**
By Richard Neidlein,* Anna Rufitiska, Harald Schwager,
and Gunther Wilke*
Dedicated to Professor Hans-Herloff Inhoffen on the
occasion of his 80th birthday
Metallacyclobutanes, which are so far known for only a
few transition metals,['' have developed into an important
~
[*I Prof. Dr. G. Wilke, Dr. A. Rufinska, DiplLChem. H. Schwagel
Max-Planck-Institut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim a.d. Ruhr (FRG)
Prof. Dr. R. Neidlein
Pharmazeutisch-chemisches Institut der Universitat
Im Neuenheimer Feld 364, D-6900 Heidelberg (FRG)
[**I
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0570-0833/86/0707-0640 $ 02 SO/O
Angew. Chem. Int. Ed. Engl. 28 (1986) No. 7
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