Reactions of cyclopropenone derivatives with a cyclopentadienylcobalt(I) chelate: Formation of a cobaltacyclobutenone and a transformation of 2,2-dimethoxycyclopropenone to methyl acrylate at cobalt

Article abstract of DOI:10.1021/om0000818

Reactions of cyclopropenone derivatives with the [2-(di-tert-butylphosphanyl)ethyl]cyclopentadienylcobalt(I) chelate system were investigated. Ethene complex 2 reacts with diphenylcyclopropenone under cobalt insertion to give cobaltacyclobutenone chelate complex 6 in 91% yield. 6 was characterized crystallographically and shows a structure similar to that of a known platinacyclobutenone. Thermoanalysis of 6 indicated a reaction at elevated temperature, which was shown to be a cycloreversion at 60°C leading to known diphenylethyne and carbonyl complexes 7 and 9. Attempts to reduce the metallacyclobutenone with lithium tetrahydridoaluminate resulted in the cycloreversion reaction at a temperature as low as -100 to -90°C, the lithium cation acting as a Lewis acid. The reaction of dimethoxycyclopropene complex 4 with zinc triflate unexpectedly resulted in the formation of methyl acrylate complex 13, which was characterized crystallographically.

Full text of DOI:10.1021/om0000818

2108
Organometallics 2000, 19, 2108-2113
Rea ction s of Cyclop r op en on e Der iva tives w ith a
Cyclop en ta d ien ylcoba lt(I) Ch ela te: F or m a tion of a
Coba lta cyclobu ten on e a n d a Tr a n sfor m a tion of
2,2-Dim eth oxycyclop r op en on e to Meth yl Acr yla te a t
Coba lt
J an Foerstner,† Alf Kakoschke,† Rudolf Wartchow,‡ and Holger Butenscho¨n*,†
Institut fu¨r Organische Chemie, Universita¨t Hannover, Schneiderberg 1B, D-30167 Hannover,
Germany, and Institut fu¨r Anorganische Chemie, Universita¨t Hannover, Callinstrasse 9,
D-30167 Hannover, Germany
Received February 1, 2000
Reactions of cyclopropenone derivatives with the [2-(di-tert-butylphosphanyl)ethyl]cyclo-
pentadienylcobalt(I) chelate system were investigated. Ethene complex 2 reacts with
diphenylcyclopropenone under cobalt insertion to give cobaltacyclobutenone chelate complex
6 in 91% yield. 6 was characterized crystallographically and shows a structure similar to
that of a known platinacyclobutenone. Thermoanalysis of 6 indicated a reaction at elevated
temperature, which was shown to be a cycloreversion at 60 °C leading to known diphenyl-
ethyne and carbonyl complexes 7 and 9. Attempts to reduce the metallacyclobutenone with
lithium tetrahydridoaluminate resulted in the cycloreversion reaction at a temperature as
low as -100 to -90 °C, the lithium cation acting as a Lewis acid. The reaction of dimeth-
oxycyclopropene complex 4 with zinc triflate unexpectedly resulted in the formation of methyl
acrylate complex 13, which was characterized crystallographically.
In tr od u ction
ation of methylcyclopropenone to platinum at -65 °C;
upon warming to -30 °C an insertion of the metal into
the strained ring occurred.10 Baddley observed the
formation of a platinacyclobutenone, which was struc-
turally characterized, upon treatment of Pt(PPh3)4 with
5.11
Transition metal complexes with cyclopropene ligands
are rare due to frequent ring-opening reactions of the
strained three-membered rings, usually leading to the
formation of oligomers or vinylcarbene complexes.1-5
Recently we reported reactions of cyclopentadienyl
chelates 1 and 2 with 3,3-diphenylcyclopropene, 3,3-
dimethylcyclopropene, and 3,3-dimethoxycyclopropene.6
Whereas the reaction with 3,3-diphenylcyclopropene
gave the corresponding 3,3-diphenylvinylcarbene com-
plex in high yield, it was possible to isolate cyclopropene
complexes 3 and 4 as stable complexes in 71% and 93%
yield, respectively.6 In continuation of this research we
were interested to use the strained, readily accessible
diphenylcyclopropenone (5) as a possible ligand.7 Cy-
clopropenones, mostly 5, have been used in reactions
with some metal complexes.8,9 Visser observed complex-
Resu lts a n d Discu ssion
Treatment of ethene complex 2 with diphenylcyclo-
propenone (5) in THF at 20 °C for 3 days gave a 91%
yield of cobaltacyclobutenone 6, which was characterized
spectroscopically. In the IR spectrum the carbonyl
absorption was observed at 1660 cm-1 and compares
well with a value of 1652 cm-1, which had been observed
for a platinacyclobutenone.11 In the 13C NMR spectrum
the signal assigned to the carbonyl carbon atom is found
at δ ) 205.3 (2J C,P ) 18.5 Hz).11 It was possible to obtain
crystals of 6, which were suitable for an X-ray crystal
structure analysis (Figure 1).
The structure of cobaltacyclobutenone 6 is rather
similar to that of the known platinacyclobutenone. The
metallacyclobutene ring is almost planar, and the bond
lengths and angles do not deviate much in both struc-
tures. As a consequence of the different atomic radii,
the bonds involving cobalt in 6 are somewhat shorter
than the corresponding ones in the platinacyclobuten-
* Corresponding author. Fax: +49/(0)511/762-4616. E-mail:
holger.butenschoen@mbox.oci.uni-hannover.de.
† Institut fu¨r Organische Chemie.
‡ Institut fu¨r Anorganische Chemie.
(1) Binger, P.; Schroth, G.; McMeeking, J . Angew. Chem. 1974, 86,
518; Angew. Chem., Int. Ed. Engl. 1974, 13, 465.
(2) Binger, P.; McMeeking, J . Angew. Chem. 1974, 86, 518-519;
Angew. Chem., Int. Ed. Engl. 1974, 13, 466.
(3) Binger, P.; Bu¨ch, H. M. Top. Curr. Chem. 1987, 135, 77-151.
(4) Fischer, H.; Hofmann, J .; Mauz, E. Angew. Chem. 1991, 103,
1013-1015; Angew. Chem., Int. Ed. Engl. 1991, 30, 998.
(5) Binger, P.; Mu¨ller, P.; Benn, R.; Mynott, R. Angew. Chem. 1989,
101, 647-648; Angew. Chem., Int. Ed. Engl. 1989, 28, 610-611.
(6) Foerstner, J .; Kakoschke, A.; Stellfeldt, D.; Butenscho¨n, H.;
Wartchow, R. Organometallics 1998, 17, 893-896.
(7) Breslow, R.; Eicher, T.; Krebs, A.; Peterson, R. A.; Posner, J . J .
Am. Chem. Soc. 1965, 87, 1320-1325.
(9) Butenscho¨n, H. In Houben-Weyl; de Meijere, A., Ed.; Thieme:
Stuttgart, 1997; Vol. E 17d, pp 3075-3078.
(10) Visser, J . P.; Ramakers-Blom, J . E. J . Organomet. Chem. 1972,
44, C63-C65.
(8) Bird, C. W.; Briggs, E. M.; Hudec, J . J . Chem. Soc. C 1967, 1862-
1864.
(11) Wong, W.; Singer, S. J .; Pitts, W. D.; Watkins, S. F.; Baddley,
W. H. J . Chem. Soc., Chem. Commun. 1972, 672-673.
10.1021/om0000818 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 04/28/2000

Reactions of Cyclopropenone Derivatives
Organometallics, Vol. 19, No. 11, 2000 2109
F igu r e 2. DTA/TG plot of 6.
Sch em e 3
F igu r e 1. Structure of 6 in the crystal. Selected bond
lengths (Å), bond and dihedral angles (deg): Co1-C1 2.112-
(2), Co1-C2 2.089(2), Co1-C3 2.089(2), Co1-C4 2.123(2),
Co1-C5 2.153(2), Co1-C16 1.936(2), Co1-C24 1.966(2),
Co1-P1 2.246(1), C16-C17 1.459(3), C17-C24 1.364(3),
C16-O1 1.214(2), C1-C2 1.413(3), C1-C5 1.426(3), C1-
C6 1.494(3), C2-C3 1.403(3), C3-C4 1.409(3), C4-C5
1.400(3), C6-C7 1.521(3), C7-P1 1.849(2); C24-Co1-C16
67.3(1), Co1-C16-C17 95.2(1), C17-C16-O1 131.0(2),
O1-C16-Co1 133.4(2), C16-C17-C24 100.0(2), C17-
C24-Co1 97.2(1), C24-Co1-P1 103.0(1), C16-Co1-P1
100.8(1), C1-C6-C7 111.4(2), C6-C7-P1 111.9(1); Co1-
C24-C17-C16 3.6(2), C1-C6-C7-P1 36.9(2).
Sch em e 1
Sch em e 4
between the cyclopentadienyl and the phosphane ligands
shows some torsion.12-15
Stang reported the reaction of (PPh3)3RhCl with 5 at
80 °C in benzene to give (PPh3)2RhCl(CO) and diphen-
ylethyne. The intermediate rhodacyclobutenone, which
was not isolated, was supposed to decompose with
formation of diphenylethyne and the observed carbonyl
complex.
Sch em e 2
A DTA/TG measurement of 6 indicates a reaction with
less than 1% loss of mass above 116 °C (Figure 2). It
was found that this reaction corresponds to the cyclo-
reversion of 6 to the known carbonyl complex 713,16 and
diphenylethyne (8). When thermolysis of 6 was carried
out in THF at 65 °C, a 60% yield of a mixture of carbonyl
and diphenylethyne complexes 7 and 913,14,16 in addition
(12) Kettenbach, R. T.; Kru¨ger, C.; Butenscho¨n, H. Angew. Chem.
1992, 104, 1052-1054; Angew. Chem., Int. Ed. Engl. 1992, 31, 1066-
1068.
one: Co1-C16 is 1.936(2) Å, as compared to 2.08(6) Å
in the platinum compound, and Co1-C24 is 1.966(2) Å,
as compared to 2.09(4) Å in the platinum complex.
Consequently the intracyclic angle at Co is somewhat
larger in 6 than in the platinacyclobutenone [67.3(1)°
vs 62°]. The bond length of the carbonyl group and the
intracyclic angle at C17 are almost equal in both cases.
As usual in chelate complexes like 6, the ethylene bridge
(13) Kettenbach, R. T.; Bonrath, W.; Butenscho¨n, H. Chem. Ber.
1993, 126, 1657-1669.
(14) Foerstner, J .; Kettenbach, R.; Goddard, R.; Butenscho¨n, H.
Chem. Ber. 1996, 129, 319-325.
(15) Foerstner, J .; Kozhushkov, S.; Binger, P.; Wedemann, P.;
Noltemeyer, M.; de Meijere, A.; Butenscho¨n, H. Chem. Commun. 1998,
239-240.
(16) Kettenbach, R. T.; Butenscho¨n, H. New J . Chem. 1990, 14, 599-
601.

2110 Organometallics, Vol. 19, No. 11, 2000
Foerstner et al.
Sch em e 5
Sch em e 6
F igu r e 3. Structure of 13 in the crystal. Selected bond
lengths (Å), bond and dihedral angles (deg): Co1-C1 2.033-
(4), Co1-C2 2.098(4), Co1-C3 2.100(4), Co1-C4 2.063(4),
Co1-C5 2.064(4), Co1-C16 1.965(6), Co1-C17 2.000(5),
Co1-P1 2.217(1), C1-C2 1.406(6), C1-C5 1.414(6), C1-
C6 1.477(6), C2-C3 1.400(5), C3-C4 1.398(6), C4-C5
1.422(6), C6-C7 1.546(5), C7-P1 1.855(4), C16-C17 1.393-
(7), C17-C18 1.446(6); Co1-C16-C17 70.8(3), Co1-C17-
C16 68.1(3), C16-C17-C18 120.6(5); C1-C6-C7-P1 40.3-
(5), C16-C17-C18-O1 8.4(9), C16-C17-C18-O2 173.1(5).
to some diphenylethyne (8) was obtained. The ratio of
7 and 9 varied within a number of experiments. The
formation of diphenylethyne complex 9 is remarkable
because it is known that carbonyl complex 7 does not
undergo a thermal ligand exchange process with diphen-
ylethyne (8) to give 9.13,16 Therefore the formation of 9
has to be regarded as a direct result of the cycloreversion
of 6. An intermediate to be considered in this reaction
is 10, with a decoordinated phosphane sidearm. 10 could
be the direct product of the cycloreversion process.
Recomplexation of the sidearm would liberate either CO
or diphenylethyne (8), possibly depending on the degree
of bond rotation around the cyclopentadienyl-cobalt
bond, which results in different directions for the
phosphorus atom to approach the metal. This line of
thought implies an associative intramolecular ligand
exchange reaction at cobalt. In a first attempt to
investigate its chemical behavior 6 was treated with
lithium tetrahydridoaluminate in THF at -78 f 20 °C.
Surprisingly, instead of a reduction of the carbonyl
group the cycloreversion to a mixture of 7 and 9
occurred. In another experiment 6 was treated with
LiAlH4 at -100 f -90 °C with a similar result. This is
remarkable because of the low reaction temperature and
the unclear role of the LiAlH4. Could it be that the
lithium cation was active instead of the tetrahydri-
doaluminate anion? This would imply LiAlH4 unusually
acting as a Lewis acid. To test this, solid lithium acetate
was added to a solution of 6 in THF at -78 to -25 °C,
followed by quenching with ethanol. Again 7 and 9 were
obtained as the only isolated products. A possible route
from 6 to 7 and 9 involves an attack of Li+ at the
carbonyl oxygen atom to give 11, whose carbonyl carbon
atom apparently is sterically shielded to such an extent,
-
that the cycloreversion is faster than an AlH4 attack,
which would induce the reduction in the case of LiAlH4.
Whereas the role of the cation as a Lewis acid assisting
the reduction process has been investigated to some
extent for borohydride reductions,17-21 this is much less
the case for aluminohydride reductions.18,19
(17) Brown, H. C.; Mead, E. J .; Rao, B. C. S. J . Am. Chem. Soc. 1955,
77, 6209-6213.
(18) Loupy, A.; Seyden-Penne, J . Tetrahedron 1980, 36, 1937-1942.
(19) Handel, H.; Pierre, J . L. Tetrahedron 1975, 31, 2799-2802.
(20) Brown, H. C.; Krishnamurthy, S. Tetrahedron 1979, 35, 567-607.
(21) Seyden-Penne, J . Reductions by the Alumino and Borohydrides
in Organic Synthesis; VCH Publishers/Lavoisier-Tec & Doc: New
York, 1991.

Reactions of Cyclopropenone Derivatives
Organometallics, Vol. 19, No. 11, 2000 2111
Sch em e 7
As it was not possible to obtain a cyclopropenone
complex by treatment of 2 with 5, we tried to prepare
such a complex starting from acetal complex 4. So far,
attempts to hydrolyze the acetal moiety with formation
of the cyclopropenone ligand failed. However, when 4
was treated with zinc triflate at low temperature, a new
product was obtained in 63% yield, which was identified
as methyl acrylate complex 13. 13 was completely
characterized, including an X-ray structure analysis
depicted in Figure 3. The structure shows only a slight
distortion of the conjugated olefinic ligand out of the
planarity of the π system.22 The orientation of the
alkene moiety is almost perpendicular as compared to
that in a cationic molybdenum acrylate complex.23
Similar to the structures of similar chelate complexes,
13 shows some torsion around the ethylene bridge
between the cyclopentadienyl and the phosphane parts
of the ligand system.
There is some evidence that in 4 cobalt inserts into
one of the strained cyclopropene single bonds with
formation of cobaltacyclobutene 14. In some expriments
this intermediate was observed and shown to react
forming the corresponding vinylcarbene complex. How-
ever, because these were only incompletely character-
ized, and because the reactions lacked reproducibility,
we refrained from publishing these results so far. We
think that in the following step the Lewis acid zinc
triflate causes partial acetal hydrolysis with formation
of hemiacetal 15, presumably by an onium cation
intermediate with a small amount of water present.24,25
In the next step a hydride shift in combination with
a ring opening would give vinyl hydride 16. This step
could also be formulated with reversed arrows, then
being a proton shift along with a ring opening. A final
reductive elimination leads to the methyl acrylate
complex 13. This mechanism is similar to the one
proposed for the rerrangement of 3,3-dimethylcyclopro-
pene to isoprene, which we reported earlier.6 In this
context a recent communication by Nakamura deserves
interest, in which the reaction of a cyclopropenone acetal
to an R,â-unsaturated ester is described to take place
in the presence of copper or silver triflate, presumably
also via a vinylmetal intermediate.26 Both cases contrast
with the known reaction of diphenylcyclopropene to cis-
1,2-diphenylacrylic acid, which takes place under basic
reaction conditions.7
Exp er im en ta l Section
Gen er a l P r oced u r es. All operations were performed in
flame-dried reaction vessels in an argon atmosphere using the
Schlenk technique. Diethyl ether and THF were distilled from
sodium-potassium alloy/benzophenone. Pentane was distilled
from calcium hydride. 1H NMR: Bruker WP 200 SY (200.1
MHz), AM 400 (400.1 MHz). 13C NMR: Bruker WP 200 SY
(50.3 MHz), AM 400 (100.1 MHz). Signal multiplicities were
determined with APT and DEPT techniques. The phase of the
signals is marked by (+) or (-), where the (+) indicates a
positive phase for C and CH2 and a (-) a negative phase for
CH and CH3. Chemical shifts refer to δTMS ) 0 or to residual
solvent signals.27,28 31P NMR: Bruker AM 400 (162 MHz), 85%
aqueous H3PO4 as external standard. IR: Perkin-Elmer FT-
IR 580 and 1710. MS: Finnigan MAT 112, 312 at 70 eV.
HRMS: Finnigan MAT 312, VG Autospec, peak matching with
PFK. Combustion analyses: Heraeus CHN Rapid. DTA/TG:
Linseis Thermobalance L 81, inert gas argon. Melting points
(uncorrected) were determined in sealed glass tubes with an
apparatus according to Dr. Tottoli. Column chromatography:
silica gel (J . T. Baker, 40 µm) was degassed by heating it with
a heat gun at reduced pressure followed by setting it under
normal pressure with argon. This sequence was repeated five
times. Separations were performed using flash chromatogra-
phy.29
Coba lta cyclobu ten on e 6. A solution of 142 mg (0.44
mmol) of ethene complex 214 and 90 mg (0.44 mmol) of
diphenylcyclopropenone (5) in 15 mL of THF was stirred for 3
days at 20 °C. After solvent removal at reduced pressure
crystallization from diethyl ether at 7, -20, and -78 °C gave
202 mg (0.4 mmol, 91%) of 6 as red-brown crystals [mp 117
°C (DTA/TG)]. Suitable crystals for structure analysis were
obtained from diethyl ether at -28 °C over 3 days.
IR (KBr): ν˜ ) 3076 cm-1 (w), 3052 (w), 3004 (w), 2960 (w,
-CH2-, CH3), 2900 (m, -CH2-, CH3), 2864 (m, -CH2-, CH3),
1660 (s, CdO), 1592 (m), 1572 (w), 1544 (m), 1476 (m), 1440
(m), 1388 (w, t-Bu), 1368 (w, t-Bu), 1256 (w), 1176 (m), 1056
(m, Cp-R), 1056 (m, Cp-R), 812 (m, Cp), 780 (m), 748 (m),
692 (m), 668 (w), 560 (m), 504 (w), 464 (w). 1H NMR (200 MHz,
[D6]-benzene): δ ) 1.05 (d, 9H, 9(10,11)-H or 13(14,15)-H, 3J P,H
) 12.4 Hz), 1.38 (d, 9H, 9(10,11)-H or 13(14,15)-H, 3J P,H ) 12.5
(22) Grevels, F.-W.; Lindemann, M.; Benn, R.; Goddard, R.; Kru¨ger,
C. Z. Naturforsch. B 1980, 35b, 1298-1309.
(26) Yu, Y.; Yamanaka, M.; Nakamura, E. Org. Lett. 1999, 1, 407-
409.
(23) Kegley, S. E.; Walter, K. A.; Bergstrom, D. T.; MacFarland, D.
K.; Young, B. G.; Rheingold, A. L. Organometallics 1993, 12, 2339-
2353.
(27) Gu¨nther, H. NMR-Spektroskopie, 2nd ed.; Georg Thieme
Verlag: Stuttgart, 1983.
(28) Kalinowski, H.-O.; Berger, S.; Braun, S. 13C NMR-Spektrosko-
pie; Georg Thieme Verlag: Stuttgart, 1984.
(29) Still, W. C.; Kahn, M.; Mitra, A. J . Org. Chem. 1978, 43, 2923-
2925.
(24) Kozikowski, A. P.; Stein, P. D. J . Am. Chem. Soc. 1985, 107,
2569-2571.
(25) Kozikowski, A. P.; Li, C.-S. J . Org. Chem. 1985, 50, 778-785.

2112 Organometallics, Vol. 19, No. 11, 2000
Foerstner et al.
Hz), 1.58-1.81 (m, 2H, 6-H), 2.00-2.19 (m, 2H, 7-H), 4.48 (m,
1H, 2-H or 3-H or 4-H or 5-H), 4.63 (m, 1H, 2-H or 3-H or 4-H
or 5-H), 4.63 (m, 1H, 2-H or 3-H or 4-H or 5-H), 6.95-7.06 [m,
2H, 21-H, 28-H], 7.12-7.24 [m, 4H, 19(23)-H or 26(30)-H],
7.67-7.58 [m, 4H, 20(22)-H or 27(29)-H]. 13C NMR (100 MHz,
portion of ethanol was added, and the mixture was warmed
to 25 °C. After removal of the volatiles at reduced pressure,
the residue was taken up with 20 mL of diethyl ether and then
filtered through a P4 frit covered with a 1 cm thick layer of
Celite. After solvent removal at reduced pressure 11 mg of a
red-brown powder was obtained, which was identified as a 1:1
mixture of 7 and 9 by comparison of the spectroscopic data
(IR, NMR).13,14,16
2
[D6]-benzene): δ ) 24.4 (d, C-6, J P,C ) 4.0 Hz), 29.5 (d,
2
C-9(10,11) or C-13(14,15), J P,C ) 2.8 Hz), 30.1 (d, C-9(10,11)
or C-13(14,15), 2J P,C) 4,0 Hz), 35.6 (d, C-8 or C-10, 1J P,C ) 10.0
Hz), 37.4 (d, C-8 or C-10, 1J P,C ) 12.5 Hz), 39.3 (d, C-7, 1J P,C
)
Rea ction of 6 w ith Lith iu m Aceta te. At -78 °C 50 mg
(0.08 mmol) of lithium acetate was added to 41 mg (0.08 mmol)
of 6 in 10 mL of THF. Over 3 h the temperature rose to -25
°C. After cooling the soution again to -78 °C 0.2 mL of ethanol
was added. After warming to 25 °C and removal of all volatiles
in vacuo, a brownish powder was obtained, which was taken
up with 20 mL of diethyl ether and filtered through a P4 frit
covered with a 1 cm thick layer of Celite. After solvent removal
at reduced pressure 18 mg of a red-brown powder was
obtained, which was identified as a 1:1 mixture of 7 and 9 by
comparison of the spectroscopic data (IR, NMR).13,14,16
20.5 Hz), 79.0 (C-2 or C-3 or C-4 or C-5), 82.6 (d, C-2, or C-3
or C-4 or C-5, 2J P,C ) 1.2 Hz), 86.1 (d, C-2 or C-3 or C-4 or C-5,
2
2J P,C ) 6.0 Hz), 88.4 (d, C-2 or C-3 or C-4 or C-5, J P,C ) 5.6
3
Hz), 120.8 (d, C-1, J P,C ) 9.3 Hz), 125.9 [C-19(23), C-26(30)
or C-20(22), C-27(29) or C-21, C-28], 128.4 [C-19(23), C-26(30)
or C-20(22), C-27(29) or C-21, C-28], 128.53 [C-19(23), C-26(30)
4
or C-20(22), C-27(29) or C-21, C-28], 131.7 (d, C-25, J C,P
)
0.8 Hz), 156.9 (d, C-17, 3J P,C ) 2.81 Hz), 170.3 (br.d, C-24, 2J P,C
) 20.1 Hz), 205.3 (d, C-16, 2J P,C ) 18.5 Hz). 31P{1H} NMR (162
MHz, [D6]-benzene): δ ) 94.8. MS (70 eV, 80 °C) m/z (%): 324
(8) [M+ - C14H10], 296 (14) [M+ - C15H10O], 240 (9) [M+
-
Rea ction of 4 w ith Zin c Tr ifla te. A 100 mg (0.25 mmol)
sample of 4 and 92 mg (0.25 mmol) of zinc triflate in 50 mL of
THF were stirred at -50 °C for 30 min. Then the solution was
allowed to warm to 25 °C over 12 h. After removal of volatiles
at reduced pressure, the residue was taken up with 50 mL of
a 1:1 mixture of pentane and diethyl ether. After filtration
through a P4 frit covered with a 3 cm thick layer of Celite
and washing with 10 mL of pentane, all solvents were
evaporated to dryness at reduced pressure to give 61 mg (0.16
mmol; 63%) of 13 as a red-brown powder (mp 54 °C). Suitable
crystals were obtained from a 1:1 mixture of diethyl ether and
pentane at -28 °C over 14 days.
C
15H10O - C4H8], 185 (18) [M+ - C15H10O - C4H8 - C4H7],
178 (100) [C14H10+], 152 (9), 137 (9), 89 (9), 76 (8). Anal. Calcd
for C30H36OPCo (502.5): C, 71.71; H, 7.71. Found: C, 71.76;
H, 7.50.
Cr ysta l Str u ctu r e An a lysis of 6: C30H36OPCo, fw 502.49
g mol-1, color red-brown, crystal size 1.04 × 0.78 × 1.85 mm,
crystal system monoclinic, space group P21/c (no. 14), a )
11.445(2) Å, b ) 13.275(2) Å, c ) 17.294(2) Å, R ) 90°, â )
99.50(2)°, γ ) 90°, V ) 2591.5(7) Å3, Z ) 4, Fcalc ) 1.288 g cm-3
,
2θmin ) 3.6°, 2θmax ) 48.1°, Mo KR, λ ) 0.71073 Å, T ) 300(2)
K, µ ) 7.4 cm-1, F(000) ) 1064 e, Stoe IPDS (imaging plate),
18 166 measured reflections ((13; (15; -18-19), 3894 unique
[R(I)int ) 0.044] and 3194 observed reflections [I > 2σ(I)], 298
refined parameters, transmission factors min, max 0.4618,
0.4687, spherical absorption correction (µR ) 0.53), no extinc-
tion correction, structure solution with direct methods with
SHELX-86, refinement with SHELXL-93, hydrogen atoms in
geometrically calculated positions, R ) 0.0265, Rw ) 0.0656
IR (CHCl3): ν˜ ) 2963 cm-1 (s, -CH2-, CH3), 2904 (m,
-CH2-, CH3), 1725 (s, ester CdO), 1454 (s), 1412 (m), 1024-
(s, Cp-R), 866 (s, Cp), 819 (s). 1H NMR (400 MHz, [D6]-
3
benzene): δ ) 0.87 (d, 9H, 9(10,11)-H or 13(14,15)-H, J P,H
)
3
11.3 Hz), 1.11 (d, 9H, 9(10,11)-H or 13(14,15)-H, J P,H ) 11.5
Hz), 1.26 (m, 2H, 6-H or 7-H), 1.75 (m, 2H, 6-H or 7-H), 2.24
(dd, 1H, 16-H, 3J H,H (cis) ) 6.0 Hz, 2J H,H ) 1.5 Hz), 2.87 (m, 1H,
16-H), 3.17 (dt, 1H, 17-H, 3J H,H (trans) ) 9.0 Hz, 3J H,H ) 2.0 Hz),
3.59 (s, 3H, 19-H), 3.91 (m, 1H, 3-H or 4-H, J P,H ) 2.4 Hz),
4.00 (m, 1H, 3-H or 4-H, J P,H ) 2.6 Hz), 5.13 (m, 1H, 2-H or
[w ) 1/σ2Fo + (0.03P)2], P ) [max (Fo + 2Fo2)]/3, minimal
and maximal residual eletron density -0.19, 0.24 e Å-3. The
crystallographic data (without structure factors) of the struc-
ture were deposited at the Cambridge Crystallographic Data
Centre (CCDC-137406). Copies of the data can be obtained
from the following address in Great Britain: CCDC, 12 Union
Road, Cambrige CB2 1EZ, UK (fax: int. code + 44-1223/336-
033, e-mail: deposit@ccdc.cam.ac.uk).
2
2
4
4
4
4
5-H, J P,H ) 1.5 Hz), 5.31 (m, 1H, 2-H or 5-H, J P,H ) 1.0 Hz).
13C NMR (100 MHz, [D6]-benzene, APT): δ ) 24.8 (+, d, C-6
2
2
or C-7, J P,C ) 6.1 Hz), 25.1 (+, d, C-16, J P,C ) 7.7 Hz), 29.5
(-, d, C-17, J P,C ) 1.1 Hz), 29.9 (-, d, C-9(10,11), J P,C ) 3.9
2
2
2
Hz), 30.7 (-, d, C-13(14,15), J P,C ) 3.9 Hz), 35.0 (+, d, C-8,
Th er m olysis of 6. A 1360 mg (2.76 mmol) sample of 6 was
heated in 50 mL of THF for 90 min at 65 °C. The color of the
solution changed from brown-red to green-brown. The solvent
was removed at reduced pressure into a cold trap, and the
residue was taken up with 40 mL of diethyl ether and filtered
through a P4 frit covered with a 1 cm thick layer of Celite.
After solvent removal 816 mg (60%) of a green-brown oil was
obtained, which was identified as a mixture of 7 and 9 (ca.
1:1) by comparison of the spectroscopic data (IR, NMR).13
Rea ction of 6 w ith Lith iu m Tetr a h yd r id oa lu m in a te.
(a) A 87 mg (0.17 mmol) sample of 6 and 1.6 mg (0.043 mmol)
of lithium tetrahydridoaluminate in 10 mL of THF were stirred
at -78 °C for 30 min. The mixture was allowed to warm to 25
°C over 3 h, was again cooled to -78 °C, and was quenched by
addition of 0.2 mL of methanol. After solvent removal at
reduced pressure the residue was taken up with 20 mL of
diethyl ether and filtered through a P4 frit covered with a 2
cm thick layer of Celite. After solvent removal 37 mg of a red-
brown powder was obtained, which was identified as a 1:1
mixture of 7 and 9 by comparison of the spectroscopic data
(IR, NMR).13,14,16
1J P,C ) 6.6 Hz), 35.3 (+, d, C-12, J P,C ) 9.1 Hz), 36.6 (+, d,
1
C-6 or C-7, 2J P,C ) 5.0 Hz), 50.3 (-, s, C-19), 79.9 (-, d, C-2 or
C-3 or C-4 or C-5, 3J P,C ) 6.6 Hz), 80.8 (-, d, C-2 or C-3 or C-4
3
or C-5, J P,C ) 1.0 Hz), 80.9 (-, d, C-2 or C-3 or C-4 or C-5,
3J P,C ) 1.4 Hz), 89.0 (-, d, C-2 or C-3 or C-4 or C-5, 3J P,C ) 5.0
3
3
Hz), 109.8 (+, d, C-1, J P,C ) 7.5 Hz), 180.3 (+, d, C-18, J P,C
) 1.4 Hz). 31P{1H} NMR (162 MHz, [D6]-benzene): δ ) 93.5
(s). MS (70 eV, 100 °C): m/z (%) 382 (3) [M+], 381 (14) [M+
-
H], 324 (1) [M+ - C4H6O2], 296 (100) [M+ - C4H6O2 - C2H3],
240 (33) [M+ - C4H6O2 - C2H3 - tBu], 184 (62) [M+ - C4H6O2
t
t
- C2H3 - Bu - Bu], 137 (23), 106 (5), 85 (3). HRMS: calcd
for (C19H32O2PCo) 382.147034; found 382.147192.
Cr ysta l Str u ctu r e An a lysis of 13: C19H32CoO2P, fw 382.35
g mol-1, red-brown plate II (001) size 0.44 × 0.31 × 0.03 mm,
crystal system monoclinic, space group P21/a (no. 14), a )
17.748(2) Å, b ) 13.011(2) Å, c ) 17.979(2) Å, R ) 90°, â )
108.66(1)°, γ ) 90°, V ) 3933.5(9) Å3, Z ) 8, Fcalc ) 1.291 g
cm-3, 2θmin ) 3.9°, 2θmax ) 48.3°, Mo KR, λ ) 0.71073 Å, T )
300(2) K, µ ) 9.6 cm-1, F(000) ) 1632 e, Stoe IPDS (imaging
plate), 24 070 measured reflections ((18; (14; (20), 5871
unique [R(I)int ) 0.100] and 2520 observed reflections [I > 2σ-
(I)], 439 refined parameters, transmission factors min, max
0.7081, 0.9714, numerical absorption correction, no extinction
correction, structure solution with direct methods with SHELX-
(b) A 5 mg (0.001 mmol) sample of lithium tetrahydridoalu-
minate was added to a solution of 25 mg (0.05 mmol) of 6 in
10 mL of THF at -100 °C. Over 3 h the cooling bath
temperature was allowed to increase to -90 °C. A 0.2 mL

Reactions of Cyclopropenone Derivatives
Organometallics, Vol. 19, No. 11, 2000 2113
86, refinement with SHELXL-93, hydrogen atoms in geo-
metrically calculated positions, but H27, H28, H29, H27′, H28′,
and H29′ free, R ) 0.0331, Rw ) 0.0529 [w ) 1/σ2(Fo2)], R is
based on F of 2520 reflections with Fo > 4σ(Fo), Rw is based on
F2 of all 5871 independent reflections, S ) 0.63, minimal and
maximal residual eletron density -0.29, 0.26 e Å-3. The
crystallographic data (without structure factors) of the struc-
ture were deposited at the Cambridge Crystallographic Data
Centre (CCDC-137405). Copies of the data can be obtained
from the following address in Great Britain: CCDC, 12 Union
Road, Cambrige CB2 1EZ, UK (fax: int. code + 44-1223/336-
033, e-mail: deposit@ccdc.cam.ac.uk).
Ack n ow led gm en t. This work was kindly supported
by the Deutsche Forschungsgemeinschaft and the Fonds
der Chemischen Industrie.
Su p p or tin g In for m a tion Ava ila ble: Tables showing
details of crystal structure determinations, atom coordinates,
equivalent isotropic thermal parameters, hydrogen atom posi-
tions, anisotropic thermal parameters, bond distances, bond
angles, and torsional angles for 6 and 13. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM0000818