Synthesis and crystal structure of novel 1,3-heterobinuclear complexes with an unusual cyclic C4R3 bridging ligand

Article abstract of DOI:10.1021/om960278t

Pentacarbonyl(dimethylvinylidene)chromium, [(CO)₅Cr=C=CMe₂] (1), reacts with the alkynyl complexes [Cp(CO)₂FeC≡CR] (4a-e; R = ⁿBu (a), Me (b), Ph (c), C₆H₄NO_2-P (d), COOMe (e)), [Cp(CO){P(OMe)₃}FeC≡CⁿBu] (6), [Cp(CO){PPh³}FeC≡CⁿBu] (8), and [Cp-(PEt₃)NiC=CⁿBu] (19) by cycloaddition of the C≡C bond of the alkynyl complexes to the C=C bond of 1 to give [(CO)₅Cr-C-CR-C(CMe₂)-Fe(CO)₂Cp] (5a-e), [(CO)₅Cr-C-C-(ⁿBu)-C(CMe₂)-Fe(CO){P(OMe) ₃}Cp] (7), [(CO)₅Cr-C-C(ⁿBu)-C(CMe₂)-Fe(CO)-{PPh ₃}Cp] (9), and [(CO)₅Cr-C-C(ⁿBu)-C(CMe₂)-Ni(PEt ₃)Cp] (20), respectively. The analogous reaction of [(CO)₅Cr=C=C(CH₂)₅] (2) with 4a and 6 affords complexes with a spirocyclic bridging ligand: [(CO)₅Cr-C-C(ⁿBu)-C{C(CH₂) ₅}-Fe(CO)₂Cp] (10) and [(CO)₅Cr-C-C(ⁿBu)-C{C(CH₂) ₅}-Fe(CO){P(OMe)₃}Cp] (11). Cycloaddition of 4a to [(CO)₅Cr=C=CPh₂] (3) yields [(CO)₅Cr-C-C(ⁿBu)-C(CPh₂)-Fe(CO)₂Cp] (12). The spectroscopic data of these novel 1,3-heterobinuclear complexes indicate the delocalized π-system Cr-C-C-C-M (M = Fe, Ni). X-ray structural analyses of the compounds 5e, 10, and 11 reveal a butterfly conformation. The puckering angle of the four-membered ring is 160.0° (5e), 143.9° (10), and 144.9° (11). Both C(sp²)-C(sp²) bonds are almost equal in length. All complexes exhibit negative solvatochromic behavior. The extent of the solvatochromic effect is strongly influenced by the substituents at C-2 and C-4 of the ring.

Full text of DOI:10.1021/om960278t

Organometallics 1996, 15, 3723-3731
3723
Syn th esis a n d Cr ysta l Str u ctu r e of Novel
1,3-Heter obin u clea r Com p lexes w ith a n Un u su a l Cyclic
C4R3 Br id gin g Liga n d
Helmut Fischer,* Fre´de´ric Leroux, Gerhard Roth, and Ru¨diger Stumpf
Fakulta¨t fu¨r Chemie, Universita¨t Konstanz, Postfach 5560 M727, D-78434 Konstanz, Germany
Received April 11, 1996X
Pentacarbonyl(dimethylvinylidene)chromium, [(CO)5CrdCdCMe2] (1), reacts with the
n
alkynyl complexes [Cp(CO)2FeCtCR] (4a -e; R ) Bu (a ), Me (b), Ph (c), C6H4NO2-p (d ),
COOMe (e)), [Cp(CO){P(OMe)3}FeCtCnBu] (6), [Cp(CO){PPh3}FeCtCnBu] (8), and [Cp-
(PEt3)NiCtCnBu] (19) by cycloaddition of the CtC bond of the alkynyl complexes to the
CdC bond of 1 to give [(CO) Cr
C
CR C(CMe ) Fe(CO) Cp] (5a -e), [(CO) Cr
C C-
- - - -
- - - - - -
- -
5
2
2
5
(nBu) C(CMe ) Fe(CO){P(OMe) }Cp]
(7),
[(CO) Cr
C
- - - -
C(nBu) C(CMe ) Fe(CO)-
- - - -
- - - -
2
3
5
2
{PPh }Cp] (9), and [(CO) Cr
analogous reaction of [(CO)5CrdCdC(CH2)5] (2) with 4a and 6 affords complexes with a
C
C(nBu) C(CMe ) Ni(PEt )Cp] (20), respectively. The
- - - - - - - -
3
5
2
3
spirocyclic bridging ligand: [(CO) Cr
C
C(nBu) C{C(CH ) } Fe(CO) Cp] (10) and
- - - - - - - -
5
2
5
2
[(CO) Cr
C
- - - -
C(nBu) C{C(CH ) } Fe(CO){P(OMe) }Cp] (11). Cycloaddition of 4a to
- -
- -
5
2
5
3
[(CO) CrdCdCPh ] (3) yields [(CO) Cr
C
- - - -
C(nBu) C(CPh ) Fe(CO) Cp] (12). The spec-
- -
- -
5
2
5
2
2
troscopic data of these novel 1,3-heterobinuclear complexes indicate the delocalized π-system
Cr M (M ) Fe, Ni). X-ray structural analyses of the compounds 5e, 10, and 11
C
C C
- - - - - - - -
reveal a “butterfly” conformation. The puckering angle of the four-membered ring is 160.0°
(5e), 143.9° (10), and 144.9° (11). Both C(sp2)-C(sp2) bonds are almost equal in length. All
complexes exhibit negative solvatochromic behavior. The extent of the solvatochromic effect
is strongly influenced by the substituents at C-2 and C-4 of the ring.
In tr od u ction
Therefore, such binuclear species are attractive syn-
thetic goals.
Bi- and polynuclear transition-metal complexes with
unsaturated carbon bridges recently attracted consider-
able interest due to their physical and chemical proper-
ties.1 Bimetallic complexes with π-conjugated carbon
chains, LnMCmM′(L′)n, have been proposed as a new
class of one-dimensional molecular wires.2 Binuclear
complexes with different LnM end groups at a conju-
gated π-system should exhibit second-order nonlinear
optical (NLO) properties.3 The magnetic, electronic, and
spectroscopic properties of such binuclear species could
easily be influenced due to the large variety of transi-
tion-metal-ligand fragments available (variation of the
metal, the ligand sphere, and the oxidation state).
Related to linear Cm bridges are rigid cyclic bridges
with a delocalized π-system connecting the metals.
Such compounds offer an advantage. Varying the
substituents at the bridging ligand should allow a fine-
tuning of the electronic communication between the
metal centers.
Recently we observed that pentacarbonyl(vinylidene)-
chromium and -tungsten complexes react with π-donor-
substituted alkynes such as ynamines and alkoxy-
alkynes by cycloaddition of the CtC bond of the alkyne
to the CdC bond of the vinylidene ligand to form
3-amino- and 3-alkoxy-substituted cyclobutenylidene
complexes (Scheme 1).4 These compounds may be
regarded as push-pull π-systems in which the [(CO)5M]
fragment acts as the acceptor and the amino or alkoxy
substituent as the donor group. Some of these com-
plexes exhibit significant second-order nonlinear optical
properties.5
X Abstract published in Advance ACS Abstracts, J uly 15, 1996.
(1) For example: (a) Maatta, E. A.; Devore, D. D. Angew. Chem.
1988, 100, 583; Angew. Chem., Int. Ed. Engl. 1988, 27, 569. (b)
Chisholm, M. H. Angew. Chem. 1991, 103, 690; Angew. Chem., Int.
Ed. Engl. 1991, 30, 673. (c) Diederich, F.; Rubin, Y. Angew. Chem.
1992, 104, 1123; Angew. Chem., Int. Ed. Engl. 1992, 31, 1101. (d) Beck,
W.; Niemer, B.; Wieser, M. Angew. Chem. 1993, 105, 969; Angew.
Chem., Int. Ed. Engl. 1993, 32, 923. (e) Lang, H. Angew. Chem. 1994,
106, 569; Angew. Chem., Int. Ed. Engl. 1994, 33, 547. (f) Irwin, M. J .;
J ia, G.; Payne, N. C.; Puddephatt, R. J . Organometallics 1996, 15, 51
and literature cited therein.
(2) See, for example: (a) Schumm, J . S.; Pearson, D. L.; Tour, J . M.
Angew. Chem. 1994, 106, 1445; Angew. Chem., Int. Ed. Engl. 1994,
33, 1360. (b) Bartik, T.; Bartik, B.; Brady, M.; Dembinski, R.; Gladysz,
J . A. Angew. Chem. 1996, 108, 467; Angew. Chem., Int. Ed. Engl. 1996,
35, 414.
The formation of cyclobutenylidene complexes not
stabilized by π-donor substituents has also been ob-
served or proposed in a few cases. Cationic cyclobuten-
ylidene complexes have been obtained from the cycload-
dition of phenylpropyne to [Cp(CO)LFedCdCH2]+ (L )
PPh3, P(OMe)3).6 The reaction of HCtCCOOMe with
photogenerated [(CO)5Cr{OEt2}] also produced a cy-
(3) See, for example: (a) Inorganic Materials; Bruce, D. W., O’Hare,
D., Eds.; Wiley: Chichester, U.K., 1992. (b) Inorganic and Organome-
tallic Polymers II: Advanced Materials and Intermediates; ACS
Symposium Series 572; Wisian-Neilson, P., Allcock, H. R., Wynne, K.
J ., Eds.; American Chemical Society: Washington, D.C., 1994.
(4) Fischer, H.; Podschadly, O.; Fru¨h, A.; Troll, C.; Stumpf, R.;
Schlageter, A. Chem. Ber. 1992, 125, 2667.
(5) Fischer, H.; Podschadly, O.; Herminghaus, S., unpublished
results.
S0276-7333(96)00278-6 CCC: $12.00 © 1996 American Chemical Society

3724 Organometallics, Vol. 15, No. 17, 1996
Fischer et al.
Sch em e 1
clobutenylidene complex in addition to a vinylvin-
ylidene complex and the alkyne complex [(CO)5Cr-
(HCtCCOOMe)].7 Both the cyclobutenylidene complex
and the vinylvinylidene complex were proposed to arise
via intermediacy of the vinylidene complex
[(CO)5CrdCdC(H)COOMe]. A cyclobutenylidene com-
plex was suggested as a key intermediate in the inser-
tion of the CtC bond of MeOOCCtCCOOMe into the
CRdCâ bond of [dppe(CO)3WdCdC(H)Ph] to form a
vinylvinylidene complex.8 The vinylvinylidene complex
was proposed to result from the ring opening of the
cyclobutenylidene intermediate.
potassium-graphite (C8K) laminate in THF at 0 °C gave
K2[Cr(CO)5] (eq 1).14 Reaction of K2[Cr(CO)5] with the
corresponding acyl chlorides (isobutyryl chloride, cyclo-
hexane carbonyl chloride, or diphenylacetyl chloride)
afforded potassium acyl(pentacarbonyl)chromates analo-
gously to a method described by Semmelhack et al.15
Reaction of these acyl(pentacarbonyl)chromates with
trifluoroacetic anhydride in CH2Cl2 at -78 °C finally
yielded the vinylidene complexes 1-3 (eq 2).16 By an
analogous procedure, cationic vinylidene complexes of
iron have been prepared from acyl complexes by Hughes
et al.17 The vinylidene complexes are very unstable and
readily decompose in solution at room temperature.
Therefore, they were usually not isolated but only
characterized by their ν(CO) spectra. The solutions
were then immediately employed in subsequent reac-
tions with alkynyl complexes.
Transition metal alkynyl complexes, LnMCtCR, are
related to the π-donor-substituted alkynes XCRtCâR (X
) NR2, OR). In both cases, the HOMO is mainly
localized at the terminal C atom (Câ).9 Hence, electro-
philes have been observed to add at the Câ atom of
alkynyl complexes to give vinylidene complexes.10
A
suitable combination of vinylidene and alkynyl com-
plexes should afford 1,3-bimetalated cyclic C4R3 com-
pounds.
A few cationic 1,3-homobimetallic complexes of iron,11
ruthenium,12 and rhenium13 have been prepared from
alkynyl complexes and electrophiles. The formation of
a cationic vinylidene complex as an intermediate was
proposed which then adds the alkynyl complex to form
the bimetallic species.
R ea ct ion s of t h e P en t a ca r b on yl(vin ylid en e)-
ch r om iu m Com p lexes 1-3 w ith Alk yn ylir on Com -
p lexes. When solutions of the alkynyldicarbonylcyclo-
pentadienyliron complexes 4a -e and of the vinylidene
complex 1 in dichloromethane were combined at -60
°C and then warmed to room temperature, the color of
the solutions changed within ca. 15 min from green to
yellow or red. Chromatographic workup of the reaction
mixture afforded the novel heterobimetallic cyclo-
butenylidene complexes 5a -e (eq 3) in moderate yields.
We now report on the synthesis of the first heterobi-
metallic cyclobutenylidene complexes and their spec-
troscopic and unusual structural properties.
Resu lts a n d Discu ssion
Gen er a t ion of t h e Vin ylid en e Com p lexes
(CO)5Cr dCdCR2 (1-3). The starting vinylidene com-
plexes 1-3 were generated by the reaction sequence
shown in eqs 1 and 2. Reduction of Cr(CO)6 with
(6) Bauer, D.; Ha¨rter, P.; Herdtweck, E. J . Chem. Soc., Chem.
Commun. 1991, 829.
(7) Berke, H.; Ha¨rter, P.; Huttner, G.; Zsolnai, L. Z. Naturforsch.
1981, 36B, 929.
(8) Gamble, A. S.; Birdwhistell, K. R.; Templeton, J . L. Organome-
tallics 1988, 7, 1046.
(9) (a) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.
(b) Lichtenberger, D. L.; Renshaw, S. K.; Wong, A.; Tagge, C. D.
Organometallics 1993, 12, 3522. (c) Lichtenberger, D. L.; Renshaw, S.
K.; Bullock, R. M. J . Am. Chem. Soc. 1993, 115, 3276.
(10) Reviews: (a) Bruce, M. I.; Swincer, A. G. Adv. Organomet.
Chem. 1983, 22, 59. (b) Bruce, M. I. Pure Appl. Chem. 1986, 58, 553.
(c) Antonova, A. B.; Ioganson, A. A. Russ. Chem. Rev. (Engl. Transl.)
1989, 58, 693. (d) Pombeiro, A. J . L., Richards, R. L. Coord. Chem.
Rev. 1990, 104, 13. (e) Davies, S. G.; McNally, J . P.; Smallridge, A. J .
Adv. Organomet. Chem. 1990, 30, 1. (f) Bruce, M. I. Chem. Rev. 1991,
91, 197. (g) Werner, H. Angew. Chem. 1990, 102, 1109; Angew. Chem.,
Int. Ed. Engl. 1990, 29, 1077.
(11) (a) Davison, A.; Solar, J . P. J . Organomet. Chem. 1978, 155,
C8. (b) Kolobova, N. Y.; Skripkin, V. V.; Alexandrov, G. G.; Struchkov,
Yu. T. J . Organomet. Chem. 1979, 169, 293. (c) Boland-Lussier, B. E.;
Hughes, R. P. Organometallics 1982, 1, 635.
(12) Bullock, R. M. J . Am. Chem. Soc. 1987, 109, 8087.
(13) Weng, W.; Bartik, T.; J ohnson, M. T.; Arif, A. M.; Gladysz, J .
A. Organometallics 1995, 14, 889.
Analogously, the trimethyl phosphite and triphen-
ylphosphine substituted complexes 7 and 9 were ob-
tained from 1 and [Cp(CO){P(OMe)3}FeCtCnBu] (6)
and [Cp(CO){PPh3}FeCtCnBu] (8), respectively (eq 4).
(14) Schwindt, M. A.; Lejon, T.; Hegedus, L. S. Organometallics
1990, 9, 2814.
(15) Semmelhack, M. F.; Lee, G. R. Organometallics 1987, 6, 1839.
(16) Fischer, H.; Podschadly, O., unpublished results. (b) Fischer,
H.; Karl, C. C.; Roth, G. Chem. Ber. 1996, 129, 615.
(17) Boland, B. E.; Fam, S. A.; Hughes R. P. J . Organomet. Chem.
1979, 172, C29.

Binuclear Complexes with a Cyclic C4R3 Ligand
Organometallics, Vol. 15, No. 17, 1996 3725
Sch em e 2
The reaction of the pentamethylenevinylidene com-
plex 2 with the alkynyliron complexes 4a and 6 afforded
complexes with a spirocyclic bridging ligand (10 and 11;
eq 5), and the reaction of the diphenylvinylidene com-
plex 3 with the alkynyl complex 4a gave the corre-
sponding diphenyl-substituted compound 12 (eq 6).
atom of [Cp(CO)2FeCtCPh] affords the cationic vin-
ylidene complexes [Cp(CO)2FedCdC(E)Ph]+. Subse-
quent reaction with a second molecule of [Cp(CO)2-
FeCtCPh] finally gives, via an adduct analogous to A
in Scheme 2, the binuclear complexes.
Similar [2 + 2] cycloaddition of imines to the CdC
bond of vinylidene complexes of iron,18,19 rhenium,20
manganese,20 chromium,19,21 and tungsten22 have been
reported. A stepwise mechanism was suggested. Two
complexes related to the proposed intermediate A
(Scheme 2) have been isolated.19b,22
The cyclobutenylidene complexes 5, 10, and 11 exhibit
some unusual spectroscopic and structural features.
From the ν(CO) absorptions of the [(CO)5Cr] fragment
at low wavenumbers a considerable transfer of electron
density from [C4R3sFeL2Cp] to the [(CO)5Cr] fragment
can be deduced. The ν(CO) spectra are similar to those
of aminocarbene complexes (e.g. [(CO)5CrdC(NHMe)-
Me]23 ) and 3-amino-substituted cyclobutenylidene com-
plexes4,5 such as 13.4
The new complexes which are formed by cycloaddition
of the CtC bond of the alkynyl complexes to the CdC
bond of the vinylidene complexes constitute the first
examples of heterobimetallic cyclobutenylidene com-
plexes. They are stable at room temperature and can
easily be handled in air. They were characterized by
microanalysis and NMR (1H, 13C, 31P) and IR spectros-
copy; additionally, the structures of the complexes 5e,
10, and 11 were determined by X-ray analyses (see
below).
The cycloaddition is highly regioselective. The forma-
tion of isomeric, 1,2-bimetalated cyclobutenylidenes has
not been observed. Vinylvinylidene complexes resulting
from an opening of the four-membered ring have
likewise not been detected.
The reaction presumably takes place in a stepwise
fashion, although it was not possible to either isolate
intermediates or detect them spectroscopically. Nucleo-
philic addition of the â-carbon atom of the alkynyl
complex to the vinylidene CR atom is followed by ring
closure to form the four-membered ring (Scheme 2). The
formation of the first 1,3-homobinuclear cyclobuten-
Obviously, the [C4R3sFeL2Cp] group is a very strong
donor ligand and the donor properties of the [FeL2Cp]
fragment are similar to those of NR2. In turn, the ν(CO)
absorptions of the [Fe(CO)2Cp] moiety in 5a -e, 10, and
12 are similar to those of the cyclobut-1-en-3-one iron
complex 14, indicating the electronic similarities of
[(CO)5Cr] and substituents as ligands in these binuclear
complexes.
As expected, all ν(CO) absorptions shift toward smaller
wavenumbers when the ability of the substituent at C-2
of the ring to donate electron density (COOMe, C6H4-
n
NO2-p, Ph, Me, Bu) increases.
(18) (a) Barrett, A. G. M.; Sturgess, M. A. Tetrahedron Lett. 1986,
27, 3811. (b) Barrett, A. G. M.; Sturgess, M. A. J . Org. Chem. 1987,
52, 3940.
(19) (a) Barrett, A. G. M.; Brock, C. P.; Sturgess, M. A. Organome-
tallics 1985, 4, 1903. (b) Barrett, A. G. M.; Mortier, J .; Sabat, M.;
Sturgess, M. A. Organometallics 1988, 7, 2553.
(20) Terry, M. R.; Mercando, L. A.; Kelley, C.; Geoffroy, G. L.;
Nombel, P.; Lugan, N.; Mathieu, R.; Ostrander, R. L.; Owens-
Waltermire, B. E.; Rheingold, A. L. Organometallics 1994, 13, 843.
(21) Weiss, K.; Fischer, E. O.; Mu¨ller, J . Chem. Ber. 1974, 107, 3548.
(22) Fischer, H.; Schlageter, A.; Bidell, W.; Fru¨h, A. Organometallics
1991, 10, 389.
ylidene complexes [Cp(CO) Fe
C
CPh C[C(E)Ph]
- - - - - -
2
Fe(CO) Cp]+ from [Cp(CO)2FeCtCPh] and electro-
- -
2
philes E+ (E ) H, Me) also was suggested to proceed by
a stepwise cycloaddition.11a Addition of E+ to the Câ
(23) Moser, E.; Fischer, E. O. J . Organomet. Chem. 1969, 16, 275.

3726 Organometallics, Vol. 15, No. 17, 1996
Fischer et al.
Ta ble 1. Selected Bon d Len gth s (Å), Bon d An gles
(d eg), a n d Tor sion An gles (d eg) for 5e, 10, a n d 11
Sch em e 3
5e
10
11
Bond Lengths
1.886(3)
2.010(3)
1.558(4)
1.541(4)
1.419(4)
1.385(4)
1.923(3)
1.772(3)
1.483(4)
Cr(1)-C(5)
Cr(1)-C(6)
C(6)-C(7)
C(7)-C(8)
C(6)-C(9)
C(8)-C(9)
C(8)-Fe(1)
Fe(1)-C(36)
C(9)-C(91)
1.887(5)
2.093(4)
1.569(5)
1.531(5)
1.409(5)
1.384(5)
1.937(4)
1.775(5)
1.493(5)
1.864(4)
2.109(3)
1.560(4)
1.539(5)
1.402(5)
1.388(4)
1.944(3)
1.739(3)
1.496(5)
Bond Angles
132.9(2)
82.7(2)
Cr(1)-C(6)-C(7)
C(6)-C(7)-C(8)
Cr(1)-C(6)-C(9)
C(7)-C(6)-C(9)
C(7)-C(8)-C(9)
C(7)-C(8)-Fe(1)
C(9)-C(8)-Fe(1)
C(6)-C(9)-C(8)
C(8)-Fe(1)-C(36)
137.0(3)
77.0(3)
130.0(3)
91.2(3)
93.8(3)
132.5(3)
132.0(3)
87.4(3)
93.2(2)
137.4(3)
77.0(2)
129.0(2)
92.0(3)
93.4(2)
130.8(2)
133.2(2)
87.6(3)
93.7(1)
137.7(2)
89.0(2)
91.0(2)
131.7(2)
137.1(2)
93.8(2)
ditionally established by X-ray structural analyses
(Tables 1 and 2). All compounds show structural
peculiarities. The structure of 5e dimethyl-substituted
at C-4 (Figure 1), on the one hand, and those of the
spirocyclic complexes 10 (Figures 2 and 3) and 11
(Figure 4), on the other hand, differ slightly; the core
structures of 10 and 11, however, are identical within
error limits. Obviously, the structural consequences of
substitution of P(OMe)3 for CO are negligible.
92.7(1)
Torsion Angles
-137.4(3)
10.6(5)
C(1)-Cr(1)-C(6)-C(7)
Fe(1)-C(8)-C(9)-C(91)
C(7)-C(8)-Fe(1)-C(36)
-34.3(4)
-22.5(7)
-36.5(4)
-33.9(3)
-28.5(5)
-42.5(3)
-142.8(2)
Until now, only two homobinuclear cyclobutenylidene
complexes (1513 and 1624 ) have been characterized by
X-ray crystallography. The structures of two cyclobut-
1
In the H NMR spectra both Me groups in 5 give rise
to only one singlet at room temperature as well as at
low temperature (-80 °C). Therefore, rotation around
the Fe-C bond and ring inversion is rapid on the NMR
time scale (see below).
The 13C resonances of both the chromium- (C-1) and
iron-bound (C-3) ring carbon atoms appear at low field.
The signals of the C-1 atom in the aryl- and carbo-
methoxy-substituted complexes 5c-e and 12 are in the
region characteristic for alkoxycarbene complexes (δ
290-320). The C-1 resonances in the alkyl-substituted
complexes (δ 217.6 (11) to 254.1 (5b)) lie in the range
usually observed for aminocarbene complexes. How-
ever, they are at a significantly higher field than those
of 3-amino-substituted cyclobutenylidene complexes
such as 13 (δ 286.3). The resonances of the C-3 atoms
are in the region characteristic for alkenyliron com-
plexes. Increasing the donor ability of the substituent
at C-2 causes a considerable high-field shift of both the
C-1 and the C-3 resonances. However, the influence on
C-1 is more pronounced than that on C-3. Increasing
the back-bonding properties of the [FeCO(L)Cp] frag-
ment by variation of L (CO, P(OMe)3, PPh3) causes a
slight upfield shift of the C-3, a downfield shift of the
C-2, and an upfield shift of the C-1 resonances. Again,
the C-1 signal is the most strongly affected. Surpris-
ingly, the C-1 and C-3 resonances are also considerably
influenced by the substituents at the sp3 ring atom C-4.
These spectroscopic results indicate that for a descrip-
tion of the overall bonding situation in these heterobi-
nuclear cyclobutenylidene complexes several resonance
structures have to be taken into account (Scheme 3).
Molecu la r Str u ctu r es of 5e, 10 a n d 11. The
structures of the complexes 5e, 10, and 11 were ad-
1-en-3-one iron complexes (complex 1425 and its dppe
derivative26 ) have also been determined as well as those
of a 3-diethylamino-substituted (17)4 and a 3-ethoxy-
substituted pentacarbonyl(cyclobutenylidene)tungsten
complex (18).4
In these complexes the four-membered ring is nearly
planar. The angle between the planes formed by the
atoms C(7), C(6), C(9) and C(7), C(8), C(9) (for the
numbering scheme, see Figure 1) ranges from 172.7°
(in 14)25 to 179.5° (in [Cp(dppe)FeCdCMeC(dO)CPh2]).26
Free cyclobut-1-en-3-ones are also almost planar. The
(24) Slovokhotov, Yu. L.; Yanovskyi, A. I.; Andrianov, V. G.; Struch-
kov, Yu. T. J . Organomet. Chem. 1980, 184, C57.
(25) Alexandrov, G. G.; Skripkin, V. V.; Kolobova, N. E.; Struchkov,
Yu. T. Koord. Khim. 1979, 5, 453.
(26) Barrett, A. G. M.; Carpenter, N. E.; Mortier, J .; Sabat, M.
Organometallics 1990, 9, 151.

Binuclear Complexes with a Cyclic C4R3 Ligand
Organometallics, Vol. 15, No. 17, 1996 3727
Ta ble 2. Cr ysta llogr a p h ic Da ta for 5e, 10, a n d 11
5e
10
11
empirical formula
C20H14CrFeO9
506.2
0.35 × 0.35 × 0.35
monoclinic
P21/c
11.011(2)
11.479(3)
16.509(4)
C25H24CrFeO7
544.3
0.5 × 0.5 × 0.5
monoclinic
P21/n
9.380(3)
14.912(4)
18.153(4)
C27H33CrFeO9P
640.4
0.3 × 0.3 × 0.3
triclinic
P1h
9.824(4)
12.743(4)
13.135(5)
93.08(3)
108.44(3)
106.87(3)
1473.4(9)
2
1.443
233
0.952
6450
4887
352
fw
cryst size, mm3
cryst system
space group
a, Å
b, Å
c, Å
R, deg
â, deg
96.61(2)
93.44(2)
γ, deg
V, Å3
2072.7(9)
4
1.622
243
1.259
4525
3415
280
2534.5(11)
4
1.426
250
1.029
5506
4323
307
Z
d
calcd, g cm-3
temp, K
µ, mm-1
no. of indep rflns
no. of obsd rflns (F > 4σ(F))
no. of params refined
R
Rw
0.037
0.036
0.34
0.058
0.070
1.12
0.045
0.048
0.70
resid electron density, e Å-3
F igu r e 3. Partial view of complex 10 (hydrogen atoms and
parts of ring substituents omitted).
F igu r e 1. Structure of complex 5e (hydrogen atoms
omitted).
F igu r e 4. Structure of complex 11 (hydrogen atoms
omitted).
11 are strongly puckered. In 5e the angle is 160.0°. In
10 (see Figure 3) and 11 the angle is even smaller:
143.9° (10) and 144.9° (11). As a consequence of the
puckering the transannular distance C(6)-C(8) is small
in 5e (2.048(5) Å) and even smaller in 10 (1.929(5) Å)
and 11 (1.930(5) Å). These distances are well below the
sum of the van der Waals distances. Therefore, direct
electronic interaction seems possible.
F igu r e 2. Structure of complex 10 (hydrogen atoms
omitted).
27
puckering angle is 178.1° in OdCCMedC(OEt)CPh2
and 177.7° in OdCC[C(O)tBu]dC(NHMe)C(Tol)H.28 In
contrast to these compounds, the rings in 5e, 10, and
(27) Trifonov, L. S.; Orahovats, A. S.; Prewo, R.; Bieri, J . H.;
Heimgartner, H. J . Chem. Soc., Chem. Commun. 1986, 708.
(28) Hirokami, S.-I.; Takahashi, T.; Nagata, M.; Yamazaki, T. J . Org.
Chem. 1987, 52, 2455.

3728 Organometallics, Vol. 15, No. 17, 1996
Fischer et al.
Both C(sp2)-C(sp2) bond lengths are similar, C(6)-
C(9) being slightly longer than C(8)-C(9). The differ-
ence in bond lengths increases in the series 11 f 10 f
5e. The distances are between the characteristic bond
lengths of a C(sp2)sC(sp2) single bond (1.46 Å) and a
C(sp2)dC(sp2) double bond (1.32 Å).29 The bond alter-
nation is more pronounced in 18 (1.419(6) versus
1.387(7) Å)4 and cyclobutenones and is reversed in 17
(1.371(8) versus 1.436(9) Å).4
Sch em e 4
The Cr(1)-C(6) distance in 5e (2.010(3) Å) is signifi-
cantly shorter than the bond lengths in 10 (2.093(4) Å)
and 11 (2.109(3) Å). This indicates a more pronounced
π-back-donation from the [(CO)5Cr] fragment into the
ring in 5e, probably due to the strong acceptor proper-
ties of the COOMe substituent at the 2-position. How-
ever, all distances are in the typical range of aminocar-
bene(pentacarbonyl) complexes.30 As is usually observed
with carbene complexes, the “carbene” plane C(6), C(7),
C(9) is staggered with respect to the cis-CO ligands, thus
avoiding unfavorable steric interactions.
As expected, the Fe(1)-C(8) distances in the [Cp-
(CO)2Fe] complexes 5e and 10 are identical, whereas
Fe(1)-C(8) in the (MeO)3P-substituted complex 11 is
slightly shorter. The distances are comparable to those
in the cyclobut-1-en-3-one complex 1425 and its dppe
derivative.26
The C(9)-C(91) distance in 5e is short and compares
well with the CsC single-bond distance in
R2CdCRsCOOR.29 The plane of the COOMe substitu-
ent at C-2 almost coincides with the “carbene” plane
C(6), C(7), C(9) (torsion angle C(6)-C(9)-C(91)-O(91)
) 2.7(5)°), indicating π-interaction between CdO and
the ring (see the mesomeric structure C in Scheme 3).
The structural results of 5e, 10, and 11 confirm the
conclusions from the spectroscopic data that the bonding
situation in these heterobinuclear cyclobutenylidene
complexes is best represented by the mesomeric struc-
tures B-D in Scheme 3, with B and C dominating. The
relative importance of B-D can be influenced by the
substituents at C-1, C-2, and C-3.
20 shows at room temperature only one singlet for the
Me groups. However, below -40 °C two resonances of
equal intensity (δ 1.28 and 1.32 in CD2Cl2 at 233 K)
are observed. These signals coalesced at 275 K; ∆Gq-
(Tc) was calculated to be 60.4 ( 0.5 kJ /mol.
For electronic reasons the plane formed by P, Ni, and
Cp(centroid) in 20 should be orthogonal to the C(7), C(8),
C(9) plane. A related conformation has been observed
for the alkenylnickel complex [Cp(PPh3)NiC(-CPhdC-
{CN}2)dC(CN)2].31 Therefore, there are four distinct
conformations for 20 which interconvert either by ring
inversion or by rotation about the NisC bond (Scheme
4).
Only rapid (on the NMR time scale) ring inversion
and rotation render both Me groups equivalent. If both
dynamic processes are slow, four resonances are to be
expected. Therefore, one of the two dynamic processes
is still fast at -40 °C. Since no broadening of the Me
resonance is observed when solutions of 5 are cooled to
-80 °C, the activation barrier ∆Gq very likely applies
to the rotation around the Ni-C bond.
Solven t Dep en d en ce of th e UV/Vis Absor p tion .
Within a group of related polar compounds the solva-
tochromic effect gives important hints on the relative
extent of the second-order nonlinear optical properties.32
As expected from the polar resonance structures B and
C, all heterobinuclear cyclobutenylidene complexes
exhibit a negative solvatochromic effect. The UV/vis
absorption at lowest energy shifts toward shorter wave-
length when nonpolar or weakly polar solvents are
replaced by more polar ones. The extent of the solvent
shift ∆ν˜(pentane-DMF) is influenced by the different
substituents at C-2, C-3, and C-4 of the ring. With
increasing donor properties of the substituent at C-2,
the solvent effect increases. The solvent shift ∆ν˜-
(pentane-DMF) of 5a -e correlates well (correlation
coefficient r2 ) 0.91) with the 13C NMR resonances of
C-2 (Figure 5).
R ea ct ion of 1 w it h [Cp (P E t3)NiCtCn Bu ]. Cy-
cloaddition of alkynyl complexes to the CdC bond of
vinylidenechromium complexes is not confined to iron
alkynyl complexes. The reaction of 1 with, for example,
[Cp(PEt3)NiCtCnBu] (19) gave, after chromatographic
workup, the cyclobutenylidene complex 20 in 27% yield
(eq 7).
There is no straightforward dependence of ∆ν˜ on the
back-bonding abilities of the LnM substituent at C-3,
although within the Fe complex series 5a , 7, 9 increas-
ing electron density at the metal tends to decrease the
solvent effect: ∆ν˜(pentane-DMF) ) 1240 (5a ), 530 (7),
Complex 20 exhibits fluxional behavior. Similar to
the case for the complexes 5, the H NMR spectrum of
1
(31) Bruce, M. I.; Duffy, D. N.; Liddell, M. J .; Snow, M. R., Tiekink,
E. R. T. J . Organomet. Chem. 1987, 335, 365.
(32) (a) Kno¨pfle, G.; Bosshard, C.; Preˆtre, P.; Gu¨nter, P. Organic
Materials for Non-Linear Optics III; Ashwell, G. J ., Bloor, D., Eds.;
Royal Society of Chemistry: London, 1993; p 100. (b) Bosshard, C.;
Kno¨pfle, G.; Preˆtre, P.; Gu¨nter, P. J . Appl. Phys. 1992, 71, 1594.
(29) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(30) Schubert, U. In Transition Metal Carbene Complexes; Do¨tz, K.
H., Fischer, H., Hofmann, P., Kreissl, F. R., Schubert, U., Weiss, K.,
Eds.; Verlag Chemie: Weinheim, 1983, 73.

Binuclear Complexes with a Cyclic C4R3 Ligand
Organometallics, Vol. 15, No. 17, 1996 3729
19,35 diphenylacetyl chloride,36 and C8K37 were prepared
according to literature procedures. Complex 4d was prepared
by following the procedure described in ref 34 for 4e. Cyclo-
hexanecarbonyl chloride and isobutyryl chloride were obtained
from Aldrich Chemical Co. and Fluka, respectively.
Gen er a tion of th e Vin ylid en e Com p lexes 1-3. At -80
°C 5.0 mmol (1.1 g) of Cr(CO)6 was added to a suspension of
10.0 mmol of C8K (1.34 g) in 50 mL of THF. The mixture was
warmed to 0 °C, stirred for 1 h at that temperature, and then
cooled to -80 °C. A 5 mmol amount of the acyl chloride was
added. The mixture was again warmed to 0 °C and stirred
for 30 min. The solvent was removed in vacuo at -20 °C, and
the residue was suspended at -80 °C in 50 mL of CH2Cl2. A
5.0 mmol (0.7 mL) amount of trifluoroacetic anhydride was
added and the mixture stirred for 30 min. The deep green
suspension was transferred to the top of a frit filled with a 3
cm layer of silica and cooled to -60 °C. Elution with ca. 100
mL of CH2Cl2 and concentration of the eluate to a volume of
ca. 30 mL gave deep green solutions of the vinylidene
complexes. These vinylidene complexes are thermally very
unstable. Therefore, they were only identified by their ν(CO)
spectra and not isolated. The solutions were immediately used
for the subsequent reactions.
F igu r e 5. Correlation between 13C NMR resonances of C-2
of 5a -e and the solvatochromic effect ∆ν˜(pentane-DMF)
in cm-1
.
670 cm-1 (9). When both Me substituents at C-4 are
replaced by C5H10 (5a f 10), ∆ν˜(pentane-DMF) almost
doubles (∆ν˜ ) 1240 (5a ), 2400 cm-1 (10)), presumably
due to the reduction of the puckering angle of the ring
and thus increased transannular interaction of C-1 and
C-3.
P en ta ca r bon yl(d im eth ylvin ylid en e)ch r om iu m (1). IR
(CH2Cl2): ν(CO) 2080 m, 1979 vs, 1960 sh cm-1
.
1H NMR (CD2-
Cl2, 198 K): δ 1.83 (s, br, Me). 13C{1H} NMR (CD2Cl2, 198
K): δ 25.3 (Me), 172.7 (Câ), 216.3 (cis-CO), 223.8 (trans-CO),
365.8 (CR).
P e n t a c a r b o n y l ( p e n t a m e t h y l e n e v i n y l i d e n e ) -
Con clu d in g Rem a r k s
ch r om iu m (2).13 IR (CH2Cl2): ν(CO) 2082 s, 2011 sh, 1994
vs, 1973 vs cm-1 1H NMR (CD2Cl2, 193 K): δ 1.54 (m, 6 H),
.
These results demonstrate that 1,3-heterobinuclear
cyclobutenylidene complexes are readily available by [2
+ 2] cycloaddition of alkynyl complexes to vinylidene
complexes. In contrast to homobinuclear cyclobuten-
ylidene complexes the ring in heterobinuclear cyclo-
butenylidene complexes adopt a “butterfly” conformation
in the solid state. On the basis of the NMR spectra the
complexes are fluxional in solution. These complexes
are thermally stable. The spectroscopic data as well as
the X-ray structural analyses of 5e, 10, and 11 indicate
strong electronic communication between the metal
centers. All 1,3-heterobinuclear cyclobutenylidene com-
plexes exhibit a pronounced negative solvatochromic
effect, the extent of which is influenced by the nature
of the substituents at the “bridging” carbon atoms C-2
and C-4 of the C4R3 moiety. Investigations to determine
the second-order nonlinear optical properties (NLO) of
this class of compounds are presently in progress.
2.14 (m, 4 H). 13C{1H} NMR (CD2Cl2, 193 K): δ 21.7, 25.1,
25.7 (CH2), 121.3 (Câ), 213.1 (cis-CO), 225.9, (trans-CO), 399.3
(CR).
P en tacar bon yl(diph en ylvin yliden e)ch r om iu m (3).13 IR
(CH2Cl2): ν(CO) 2088 s, 2027 sh, 2002 vs, 1977 vs cm-1 1H
.
NMR (CD2Cl2, 228 K): δ 7.15-7.45 (m, Ph). 13C{1H} NMR
(CDCl3, 223 K): δ 127.1, 128.1, 129.0, 130.6 (Ph), 133.7 (Câ),
211.9 (cis-CO), 222.8 (trans-CO), 405.9 (CR).
P r ep a r a tion of th e Com p lexes 5, 7, 9-12 a n d 20. At
-60 °C a solution of 5.0 mmol of the alkynyl complexes in 50
mL of CH2Cl2 was added to a solution of the vinylidene
complexes 1-3 in CH2Cl2. The mixture was stirred for 20 min
at -60 °C and then for 30 min at room temperature. The
solvent was removed in vacuo, and the residue was chromato-
graphed on silica gel at -30 °C. The complexes were eluted
with pentane/CH2Cl2 (ratio decreasing from 1/0 to 1/1) as
orange or red solutions. The solvent was removed in vacuo,
and the complexes were crystallized from 20 mL of pentane/
CH2Cl2 as described below.
P en ta ca r bon yl[2-n -bu tyl-3-{d ica r bon yl(η5-cyclop en ta -
d ien yl)fer r io}-4,4-d im eth ylcyclobu t-2-en -1-ylid en e]ch r o-
m iu m (5a ). Yield: 1.00 g (40% based on Cr(CO)6) of yellow
crystals from pentane/CH2Cl2 (1:1). Mp: 64 °C. IR (CH2Cl2):
Exp er im en ta l Section
Gen er a l Com m en ts. All operations were performed under
an inert atmosphere (nitrogen or argon) by using standard
Schlenk techniques. Solvents were dried by refluxing over
CaH2 (CH2Cl2) or sodium/benzophenone ketyl (pentane, Et2O,
THF) and were freshly distilled prior to use. The silica gel
used for chromatography (Baker, silica gel for flash chroma-
tography) was nitrogen-saturated. The yields refer to analyti-
cally pure compounds and were not optimized. Instrumenta-
tion: 1H NMR and 13C NMR spectra were recorded with a
Bruker AC 250 or a Bruker WM 250 spectrometer; 31P NMR
spectra were recorded with a J EOL J NX 400 spectrometer.
1H and 13C NMR resonances are reported relative to TMS and
31P NMR resonances relative to external H3PO4. Other
instruments used are as follows: IR, Biorad FTS 60 spectro-
photometer; MS, Finnigan MAT 312; UV/vis, Hewlett-Packard
diode array spectrophotometer 8452A; elemental analyses,
Heraeus CHN-O-RAPID.
ν(CO) 2049 m, 2028 s, 1982 s, 1923 vs cm-1
.
1H NMR (CDCl3,
3
298 K): δ 0.93 (t, J HH ) 6.91 Hz, 3H, Me), 1.41 (s, br, 10H,
3
CH2 and Me), 2.62 (t, J HH ) 7.45 Hz, 2H, CH2), 4.93 (s, 5H,
C5H5). 13C{1H} NMR (CD2Cl2, 298 K): δ 13.8 (Me), 22.7 (CH2),
28.3 (Me), 28.6, 29.8 (CH2), 76.0 (4-C), 86.0 (C5H5), 208.3 (2-
C), 208.8 (3-C), 212.2 (Fe-CO), 218.9 (cis-CO), 225.9 (trans-
CO), 242.6 (1-C). UV/vis (λmax, nm (log ꢀ)): 452 (3.974)
[pentane]; 428 (3.901) [DMF]. Anal. Calcd for C22H20CrFeO7
(504.2): C, 52.40; H, 4.00. Found: C, 52.49; H, 3.87.
(34) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Lanfranchi, M.; Tirip-
icchio, A. J . Organomet. Chem. 1991, 405, 333.
(35) Sonogashira, K.; Yatake, T.; Tohda, Y.; Takahashi, S.; Hagihara,
N. J . Chem. Soc., Chem. Commun. 1977, 291.
(36) Organikum, 16 ed.; VEB Deutscher Verlag der Wissen-
schaften: Berlin, 1986.
(37) (a) Handbuch der Pra¨parativen Anorganischen Chemie; Brauer,
G., Ed.; Ferdinand Enke Verlag: Stuttgart, Germany, 1978; Vol. 2.
(b) Savoia, D.; Trombini, C.; Umani-Ronchi, A. Pure Appl. Chem. 1985,
57, 1887.
The alkynyl complexes 4a ,33 4b,33 4c,33 4e,34 6,18, 8,33 and
(33) Green, M. L. H.; Mole, T. J . Organomet. Chem. 1968, 12, 404.

3730 Organometallics, Vol. 15, No. 17, 1996
Fischer et al.
P en ta ca r bon yl[3-{d ica r bon yl(η5-cyclop en ta d ien yl)fer -
r io}-2,4,4-tr im eth ylcyclobu t-2-en -1-yliden e]ch r om iu m (5b).
Yield: 0.67 g (29% based on Cr(CO)6) of red crystals from
pentane/CH2Cl2 (7:3). Mp: 88 °C. IR (CH2Cl2): ν(CO) 2049
2-en -1-ylid en e]ch r om iu m (9). Yield: 0.74 g (20% based on
Cr(CO)6) of orange crystals from pentane/CH2Cl2 (3:2). Mp:
148 °C. IR (CH2Cl2): ν(CO) 2042 m, 1948 m, 1919 vs cm-1
.
1H NMR (CDCl3, 298 K): δ 0.76 (t, J HH ) 7.0 Hz, 3H, Me),
1.02-1.35 (m, br, 10H, 4 × CH2 and 2 × Me), 2.15-2.26 (m,
br, 1H, CH2), 2.49-2.56 (m, br, 1H, CH2), 4.56 (d, J PH ) 1.29
Hz, 5H, C5H5), 7.21-7.52 (m, br, 15H, Ph). 13C{1H} NMR
(CDCl3, 298 K): δ 13.9 (Me), 22.3 (CH2), 22.9 (Me), 29.7, 34.1
(CH2), 78.4 (4-C), 85.2 (C5H5), 128.5, 128.7, 130.6, 133.0, 133.1,
3
m, 2029 s, 1984 s, 1923 vs cm-1 1H NMR (CD2Cl2, 273 K): δ
.
1.37 (s, 6H, Me), 2.22 (s, 3H, Me), 4.98 (s, 5H, C5H5). 13C{1H}
NMR (CD2Cl2, 223 K): δ 14.6, 27.6 (Me), 75.4 (4-C), 85.8
(C5H5), 202.3 (2-C), 212.0 (3-C), 216.1 (Fe-CO), 218.6 (cis-CO),
226.3 (trans-CO), 254.1 (1-C). UV/vis (λmax, nm (log ꢀ)): 462
(4.051) [pentane]; 442 (3.987) [DMF]. MS (70 eV; m/ z (%)):
462 (35) [M+], 434 (8) [(M - CO)+], 406 (19) [(M - 2CO)+],
378 (7) [(M - 3CO)+], 350 (48) [(M - 4CO)+], 322 (66) [(M -
5CO)+], 294 (28) [(M - 6CO)+], 266 (100) [(M - 7CO)+]. Anal.
Calcd for C19H14CrFeO7 (462.12): C, 49.36; H, 3.05. Found:
C, 49.26; H, 3.10.
2
135.0, 135.7 (Ph), 210.2 (2-C), 218.8 (d, J CP ) 30.8 Hz, Fe-
CO), 219.9 (cis-CO), 224.9 (d, 2J CP ) 16.8 Hz, 3-C), 225.3 (trans-
CO), 227.9 (1-C). 31P{1H} NMR (CDCl3, 298 K): δ 70.8 (s).
UV/vis (λmax, nm (log ꢀ)): 428 (3.967) [pentane]; 416 (3.928)
[DMF]. Anal. Calcd for C39H35CrFeO6P (738.49): C, 63.43;
H, 4.78. Found: C, 63.71; H, 5.30.
P en ta ca r bon yl[3-{d ica r bon yl(η5-cyclop en ta d ien yl)fer -
r io}-4,4-dim eth yl-2-ph en yl-2-cyclobu t-2-en -1-yliden e]ch r o-
m iu m (5c). Yield: 0.92 g (35% based on Cr(CO)6) of dark red
crystals from pentane/CH2Cl2 (3:1). Mp: 82 °C. IR (pen-
P en ta ca r bon yl[2-n -bu tyl-3-{d ica r bon yl(η5-cyclop en ta -
dien yl)fer r io}-spir o[5.3]n on -2-en -1-yliden e]ch r om iu m (10).
Yield: 0.82 g (30% based on Cr(CO)6) of orange crystals from
pentane/CH2Cl2 (1:1). Mp: 74 °C. IR (pentane): ν(CO) 2047
tane): ν(CO) 2051 m, 2028 s, 1986 m, 1948 vs, 1933 s cm-1
.
m, 2027 m, 1980 m, 1920 vs cm-1 1H NMR (CDCl3, 298 K):
.
1H NMR (CDCl3, 298 K): δ 1.46 (s, 6H, Me), 4.83 (s, 5H, C5H5),
7.33-7.45 (m, 5H, Ph). 13C{1H} NMR (CDCl3, 298 K): δ 26.6
(Me), 76.5 (4-C), 86.0 (C5H5), 128.3, 128.5, 130.7, 136.9 (Ph),
199.2 (2-C), 211.9 (Fe-CO), 217.9 (cis-CO), 228.3 (trans-CO),
241.2 (3-C), 304.9 (1-C). UV/vis (λmax, nm (log ꢀ)): 490 (4.148)
[pentane]; 476 (4.159) [DMF]. Anal. Calcd for C24H16CrFeO7
(524.23): C, 54.99; H, 3.08. Found: C, 54.59; H, 3.22.
δ 0.92 (t, br, 3H, Me), 1.34-1.93 (m, 14H, 7 × CH2), 2.75 (t,
br, 2H, CH2), 4.88 (s, 5H, C5H5). 13C{1H} NMR (CDCl3, 298
K): δ 13.8 (Me), 22.8, 24.1, 25.5, 29.5, 29.9, 39.8, (CH2), 82.1
(4-C), 85.9 (C5H5), 190.5 (2-C), 212.4 (Fe-CO), 214.1 (3-C),
219.1 (cis-CO), 224.0 (trans-CO), 224.2 (1-C). UV/vis (λmax, nm
(log ꢀ)): 440 (3.834) [pentane]; 398 (3.888) [DMF]. Anal. Calcd
for C25H24CrFeO7 (544.3): C, 55.17; H, 4.44. Found: C, 55.14;
H, 4.43.
P en ta ca r bon yl[2-n -bu tyl-3-{ca r bon yl(η5-cyclop en ta d i-
en yl)(tr im eth yl p h osp h ite)fer r io}sp ir o[5.3]n on -2-en -1-
ylid en e]ch r om iu m (11). Yield: 1.18 g (37% based on
Cr(CO)6) of orange crystals from pentane/CH2Cl2 (2:3). Mp:
P en ta ca r bon yl[3-{d ica r bon yl(η5-cyclop en ta d ien yl)fer -
r io }-2-(p -n it r o p h e n y l)-4,4-d im e t h y lc y c lo b u t -2-e n -1-
ylid en e]ch r om iu m (5d ). Yield: 1.14 g (40% based on
Cr(CO)6) of dark red crystals from pentane/CH2Cl2 (3:2). Mp:
85 °C dec. IR (CH2Cl2): ν(CO) 2051 s, 2030 s, 1988 m, 1936
vs, 1925 sh cm-1 1H NMR (CDCl3, 298 K): δ 1.46 (s, 6H, Me),
.
4.90 (s, 5H, C5H5), 7.53 and 7.57 (m, 2H, C6H4), 8.31 and 8.34
(m, 2H, C6H4). 13C{1H} NMR (CDCl3, 298 K): δ 26.4 (Me),
72.6 (4-C), 86.0 (C5H5), 123.8, 129.8, 144.3, 147.7 (C6H4), 196.2
(2-C), 211.5 (Fe-CO), 217.4 (cis-CO), 227.9 (trans-CO), 244.3
(3-C), 312.6 (1-C). UV/vis (λmax, nm (log ꢀ)): 490 (4.087)
[pentane]; 480 (4.176) [DMF]. Anal. Calcd for C24H15CrFeNO9
(569.0): C, 50.62; H, 2.66; N, 2.46. Found: C, 50.64; H, 2.80;
N, 2.71.
140 °C. IR (CH2Cl2): ν(CO) 2042 m, 1947 m, 1916 vs, 1889
3
sh cm-1
.
1H NMR (CDCl3, 298 K): δ 0.92 (t, J HH ) 7.1 Hz,
3H, Me), 1.26-2.00 (m, 14H, CH2), 2.73 (t, br, 2H, CH2), 3.62
(d, 3J PH ) 11.2 Hz, 9H, OMe), 4.61 (s, 5H, C5H5). 13C{1H} NMR
(CDCl3, 298 K): δ 14.1 (Me), 23.2, 23.7, 24.6, 25.8, 29.6, 29.7,
36.2, 43.6 (CH2), 52.7 (d, 3J CP ) 7.5 Hz, OMe), 81.6 (4-C), 83.9
3
2
(C5H5), 205.0 (d, J CP ) 31.2 Hz, 2-C), 213.7 (d, J CP ) 5.4 Hz,
3-C), 217.0 (d, 2J CP ) 47.1 Hz, Fe-CO), 217.6 (1-C), 219.8 (cis-
CO), 224.5 (trans-CO). 31P{1H} NMR (CDCl3, 298 K): δ 180.8
(s). UV/vis (λmax, nm (log ꢀ)): 416 (3.457) [pentane]; 392 (3.875)
[DMF]. Anal. Calcd for C27H33CrFeO9P (640.3): C, 50.64; H,
5.19. Found: C, 50.61; H, 5.21.
P en ta ca r bon yl[2-(ca r bom eth oxy)-3-{d ica r bon yl(η5-cy-
clop e n t a d ie n yl)fe r r io }-4,4-d im e t h ylcyclob u t -2-e n -1-
ylid en e]ch r om iu m (5e). Yield: 0.76 g (30% based on
Cr(CO)6) of brown crystals from pentane/CH2Cl2 (2:3). Mp: 76
°C. IR (CH2Cl2): ν(CO) 2056 m, 2035 s, 1981 s, 1941 vs, 1936
P en ta ca r bon yl[2-n -bu tyl-3-{d ica r bon yl(η5-cyclop en ta -
d ien yl)fer r io}-4,4-d ip h en ylcyclobu t-2-en -1-ylid en e]ch r o-
m iu m (12). Yield: 0.47 g (15% based on Cr(CO)6) of black
crystals from pentane/CH2Cl2 (3:2). Mp: 170 °C dec. IR
sh, 1751 m cm-1 1H NMR (CDCl3, 298 K): δ 1.41 (s, 6H, Me),
.
3.89 (s, 3H, OMe), 5.07 (s, 5H, C5H5). 13C{1H} NMR (CDCl3,
298 K): δ 26.5 (Me), 50.8 (OMe), 74.7 (4-C), 86.7 (C5H5), 163.7
(COOMe), 185.9 (2-C), 211.0 (Fe-CO), 217.6 (cis-CO), 228.6
(trans-CO), 257.0 (3-C), 314.8 (1-C). UV/vis (λmax, nm (log ꢀ)):
482 (4.101) [pentane]; 478 (4.181) [DMF]. Anal. Calcd for
(pentane): ν(CO) 2050 m, 2030 m, 1989 m, 1945 vs, 1931 sh
3
cm-1
.
1H NMR (CDCl3, 298 K): δ 0.94 (t, J HH ) 7.2 Hz, 3H,
Me), 1.37-1.61 (m, 4H, CH2), 2.58-2.64 (m, 2H, CH2), 4.58
(s, 5H, C5H5), 7.26-7.42 (m, 10H, Ph). 13C{1H} NMR (CDCl3,
298 K): δ 13.7 (Me), 22.9, 29.7, 30.3 (CH2), 84.3 (4-C), 86.3
(C5H5), 126.9, 128.0, 130.1, 142.9 (Ph), 203.0 (2-C), 212.1 (Fe-
CO), 217.5 (cis-CO), 227.1 (trans-CO), 231.8 (3-C), 296.0 (1-
C). UV/vis (λmax, nm (log ꢀ)): 504 (3.915) [pentane]; 484 (3.856)
[DMF]. Anal. Calcd for C32H24CrFeO7 (628.34): C, 61.17; H,
3.85. Found: C, 61.12; H, 4.26.
P en t a ca r b on yl[2-n -b u t yl-3-{η5-cyclop en t a d ien yl(t r i-
et h ylp h osp h in e)n ick elio}-4,4-d im et h ylcyclob u t -2-en -1-
ylid en e]ch r om iu m (20). Yield: 0.77 g (27% based on
Cr(CO)6) of brown crystals from pentane/CH2Cl2 (1:1). Mp: 65
C
20H14CrFeO9 (506.2): C, 47.46; H, 2.79. Found: C, 47.83;
H, 2.98.
P en t a ca r b on yl[2-n -b u t yl{ca r b on yl(η5-cyclop en t a d i-
en yl)(tr im eth yl p h osp h ite)fer r io}-4,4-d im eth ylcyclobu t-
2-en -1-ylid en e]ch r om iu m (7). Yield: 1.38 g (46% based on
Cr(CO)6) of orange crystals from pentane/CH2Cl2 (2:3). Mp:
83 °C. IR (CH2Cl2): ν(CO) 2041 m, 1952 s, 1916 vs cm-1
.
1H
3
NMR (CDCl3, 298 K): δ 0.93 (t, J HH ) 6.3 Hz, 3H, Me), 1.31
(s, 3H, Me), 1.37-1.48 (m, br, 4H, 4 × CH2), 1.48 (s, 3H, Me),
2.59-2.64 (m, br, 2H, CH2), 3.64 (d, 3J PH ) 11.3 Hz, 9H, OMe),
4.70 (s, 5H, C5H5). 13C{1H} NMR (CDCl3, 298 K): δ 14.0 (Me),
3
23.1 (CH2), 25.9, 29.1 (Me), 29.9, 32.1 (CH2), 52.8 (d, J CP
)
°C. IR (pentane): ν(CO) 2044 m, 1923 vs cm-1
.
1H NMR (CD2-
7.2 Hz, OMe), 76.3 (4-C), 84.2 (C5H5), 208.7 (2-C), 216.5 (d,
3
2
2J CP ) 45.9 Hz, Fe-CO), 219.9 (cis-CO), 225.1 (d, J CP ) 33.3
Cl2, 233 K): δ 0.89 (t, J HH ) 6.9 Hz, 3H, Me), 0.99-1.11 (m,
9H, CH2CH3), 1.28 (s, 3H, Me), 1.32 (s, 3H, Me), 1.35-1.49
(m, 10H, 2 × CH2 and 3 × PCH2), 2.56-2.64 (m, 2H, CH2),
5.23 (s, 5H, C5H5). 13C{1H} NMR (CD2Cl2, 233 K): δ 7.6
Hz, 3-C), 225.9 (trans-CO), 234.5 (1-C). 31P{1H} NMR (CDCl3,
298 K): δ 179.3 (s). UV/vis (λmax, nm (log ꢀ)): 440 (3.989)
[pentane]; 430 (3.938) [DMF]. Anal. Calcd for C24H29CrFeO9P
(600.26): C, 48.02; H, 4.87. Found: C, 47.70; H, 4.85.
P en ta ca r bon yl[2-n -bu tyl-3-{ca r bon yl(η5-cyclop en ta d i-
en yl)(tr ip h en ylp h osp h in e)fer r io}-4,4-d im eth ylcyclobu t-
2
(CH2CH3), 13.9 (Me), 18.3 (d, J PH ) 28.5 Hz, PCH2), 22.7
(CH2), 28.2 (Me), 29.5 (CH2), 29.6 (Me), 30.4 (CH2), 74.8 (4-C),
3
90.9 (C5H5), 204.5 (d, J CP ) 23.9 Hz, 2-C), 208.6 (3-C), 219.3

Binuclear Complexes with a Cyclic C4R3 Ligand
Organometallics, Vol. 15, No. 17, 1996 3731
(cis-CO), 224.1 (trans-CO), 225.6 (1-C). 31P{1H} NMR (CDCl3,
298 K): δ 31.2 (s). UV/vis (λmax, nm (log ꢀ)): 448 (2.031)
[pentane]; 420 (3.929) [DMF]. MS (FAB, 2-nitrophenyl octyl
ether; m/ z (%)): 568 (12) [M+], 540 (4) [(M - CO)+], 512 (10)
[(M - 2CO)+], 456 (32) [(M - 4CO)+], 450 (100) [(M - PEt3)+],
428 (24) [(M - 5CO)+], 422 (48) [(M - PEt3 - CO)+], 394 (26)
[(M - PEt3 - 2CO)+], 376 (60) [(M - Cr(CO)5)+], 366 (18) [(M
- PEt3 - 3CO)+], 338 (22) [(M - PEt3 - 4CO)+]. Anal. Calcd
for C26H35CrNiO5P (568.1): C, 54.92; H, 6.21. Found: C, 55.13;
H, 6.31.
X-r a y Str u ctu r a l An a lyses of 5e, 10, a n d 11. Single
crystals were grown from pentane/CH2Cl2 (2:3 (5e), 1:1 (10),
2:3 (11)) and mounted in a glass capillary. All crystal data
were collected on a Siemens R3m/V diffractometer (Wyckoff
scan, 4° < 2θ < 54°) with a graphite monochromator (Mo KR,
λ ) 0.710 73 Å). Semiempirical absorption corrections were
carried out (ψ scans with 10 reflections). The structures were
solved with Patterson methods and refined by full-matrix least-
squares techniques (Siemens SHELXTL PLUS).
sites did not result in reasonable bond angles and lengths and
did not lead to lower thermal parameters or R values. In the
present model, the ultimate refinement was performed with
bond length restraints for C(92)-C(93) and C(93)-C(94),
resulting in reasonable bond angles. Similar problems oc-
curred for C(72), C(73), and C(74) of the cyclohexane ring, but
in this case no restraint was applied.
Ack n ow led gm en t. Support of this work by the
Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie is gratefully acknowledged. We
thank B. Weibert for collecting the data sets for the
X-ray analyses.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement details, complete positional and thermal
parameters, bond distances, bond angles, and torsion angles
for compounds 5e, 10, and 11 and figures giving additional
views of 10 (42 pages). Ordering information is given on any
current masthead page.
The butyl group of 10 is disordered. This leads to high
thermal parameters for C(93) and C(94). Many efforts to
model the disorder by varying the occupancy factors and atom
OM960278T