Oxidation of metal carbynes in the presence of alkynes. Alkyne addition vs H-shift in the carbene intermediate

Article abstract of DOI:10.1021/om980534x

One-electron oxidation of the carbyne complex (η⁵-C₅H₅)(CO){P(OPh) ₃}Mo≡CCH₂CH₂CH₂-CH₃ (1a) in the presence of phenylacetylene results in H-abstraction and addition of

Full text of DOI:10.1021/om980534x

Organometallics 1998, 17, 4413-4416
4413
Oxid a tion of Meta l Ca r byn es in th e P r esen ce of Alk yn es.
Alk yn e Ad d ition vs H-Sh ift in th e Ca r ben e In ter m ed ia te
Karen E. Torraca, Khalil A. Abboud, and Lisa McElwee-White*
Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200
Received J une 24, 1998
One-electron oxidation of the carbyne complex (η5-C5H5)(CO){P(OPh)3}MotCCH2CH2CH2-
CH3 (1a ) in the presence of phenylacetylene results in H-abstraction and addition of the
alkyne to the resulting metal carbene. The final product of the addition is the η1η2-allyl
complex (η5-C5H5)(CO){P(OPh)3}Mo[η1:η2-CH{P(OPh)3}C(Ph)dCH(CH2CH2CH2CH3)] (2a ),
the structure of which was confirmed by X-ray crystallography.
Sch em e 1
In tr od u ction
We have previously reported that oxidation of the
carbyne complexes (η5-C5H5)(CO){P(OR′)3}MtCR [M )
Mo, W; R ) alkyl; R′ ) Me, Ph]1 results in formation of
17-electron complexes that abstract hydrogen at the
carbyne carbon to form cationic metal carbenes.2,3
When R is a primary alkyl group, hydride shift in the
carbene complex yields an alkene as the final organic
product. We now report that when (η5-C5H5)(CO){P-
(OPh)3}MotCCH2CH2CH2CH3 (1a ) undergoes one-
electron chemical oxidation in the presence of phenyl-
acetylene, the H-shift pathway of the metal carbene
intermediate is suppressed. Instead, addition of the
alkyne and nucleophilic trapping with phosphite yield
the η1η2-allyl complex (η5-C5H5)(CO){P(OPh)3}Mo[η1:η2-
CH{P(OPh)3}C(Ph)dCH(CH2CH2CH2CH3)] (2a ).
is known to result in the formation of 1-pentene (Scheme
1) in a process involving H-abstraction by the oxidized
carbyne followed by a facile 1,2-hydride shift in the
resulting carbene complex (3a ).3 Observation of 1-pen-
tene after oxidation of 1a is thus a marker for the
H-abstraction/H-shift sequence that is typical of these
17-electron alkyl carbynes. In the test reaction, a
solution of 1a in CD2Cl2 at -95 °C was slowly mixed
Resu lts a n d Discu ssion
In prior studies, the oxidations were carried out by
photochemical electron transfer from the carbyne com-
plexes to CHCl3. However, there are aspects of this
method that make it difficult to obtain products in high
yield. Upon reduction, CHCl3 fragments to Cl- and
•CHCl2.4 Evidence for side reactions involving the
•CHCl2 radical can be found in the formation of CH3Cl5
by Arbuzov reaction of P(OMe)3 ligands.6 The use of
outer sphere chemical oxidants7 at low temperatures
provides an alternative approach in which side reactions
with a dilute solution of AcFc+BF4 in CD2Cl2 to yield
-
a dark purple reaction mixture. Warming to ambient
temperature produced an orange-brown solution whose
color is characteristic of acetylferrocene. Analysis of the
1
volatile components by H NMR spectroscopy revealed
the presence of 1-pentene, as also seen following pho-
tooxidation.
•
from CHCl2 can be avoided.
Once it had been established that oxidation of 1a with
To confirm that chemical oxidation generates the
same intermediates as photooxidation, butyl carbyne 1a
was reacted with acetylferrocenium tetrafluoroborate
(AcFc+BF4-). Photolysis of 1a in the presence of CDCl3
AcFc+BF4 yields the same product as photooxidation,
-
the reaction was carried out in the presence of phenyl-
acetylene. A mixture of butyl carbyne 1a plus 10 equiv
of phenylacetylene was dissolved in CD2Cl2. A dilute
solution of acetylferrocenium tetrafluoroborate was then
added at -95 °C to yield a dark purple solution. Upon
slow warming to ambient temperature, the reaction
mixture became an orange-brown color similar to that
observed in the absence of alkyne. Examination of the
volatile components by 1H NMR confirmed that no
1-pentene had been formed and thus, in the presence
of the alkyne, the expected H-abstraction/H-shift se-
quence had been suppressed. Instead, compound 2a
was isolated in 25% yield (Scheme 2). In subsequent
(1) McElwee-White, L. Synlett 1996, 806-814.
(2) Main, A. D.; McElwee-White, L. J . Am. Chem. Soc. 1997, 119,
4551-4552.
(3) (a) Schoch, T. K.; Orth, S. D.; Zerner, M. C.; J ørgensen, K. A.;
McElwee-White, L. J . Am. Chem. Soc. 1995, 117, 6475-6482. (b)
Torraca, K. E.; Storhoff, D. A.; McElwee-White, L. J . Organomet. Chem.
1998, 554, 13-18.
(4) Buehler, R. E. In The Chemistry of the Carbon-Halogen Bond;
Patai, S., Ed.; Wiley: London, 1973; pp 795-864.
(5) Kingsbury, K. B.; Carter, J . D.; Wilde, A.; Park, H.; Takusagawa,
F.; McElwee-White, L. J . Am. Chem. Soc. 1993, 115, 10056-10065.
(6) Brill, T. B.; Landon, S. J . Chem. Rev. 1984, 84, 577-85.
(7) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877-910.
S0276-7333(98)00534-2 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/04/1998

4414 Organometallics, Vol. 17, No. 20, 1998
Torraca et al.
of free P(OPh)3 to produce 2b in 39% isolated yield
(Scheme 2). In addition, 1a reacted with 1-hexyne
under similar conditions to furnish 2c in 28% yield. The
structures of these compounds were assigned by com-
parison of their spectral data to that of 2a .
Since control experiments have established that the
carbynes 1a ,b do not react with alkynes in the absence
of an oxidant, the first step in formation of 2a -c must
be generation of the 17-electron carbyne. The structures
of the adducts require hydrogen abstraction, addition
of the alkyne, and addition of the phosphite. Given the
previously observed chemistry, it is reasonable to pos-
tulate initial H-abstraction, then subsequent chemistry
derived from the 16-electron cationic carbenes 3a ,b.
Insertion of the alkyne into the ModC double bond9
would produce vinylcarbene complexes 5a -c, which
could undergo nucleophilic attack by the phosphite10 to
yield 2a -c.
An adduct similar to 2a was previously observed by
Geoffroy following protonation of (η5-C5H5)(CO)2Wt
CTol with HBF4 in the presence of diphenylacetylene
and PBu3.11 Although the intermediate derived from
the initial protonation could not be directly observed,
it was postulated to be the cationic carbene [(η5-C5H5)-
(CO)2WdCHTol]+ (6). Given the analogy between in-
termediates 6 and 3a ,b, we attempted to independently
generate 3a by protonation of 1a with HBF4. However,
this control experiment did not produce 1-pentene, as
expected if cationic carbene 3a were formed (Scheme
1). As a result of this discrepancy, the product of the
F igu r e 1. Thermal ellipsoid diagram of 2a showing the
crystallographic numbering scheme. Thermal ellipsoids are
drawn at the 40% probability level. The majority of the
hydrogens are removed for clarity.
Sch em e 2
1
protonation was characterized by low-temperature H
NMR. This experiment revealed that protonation of 1a
results in the face-protonated carbyne complex [(η5-
C5H5)(CO){P(OPh)3}(H)MotCBu]+ (4) as evidenced by
the proton signal at -2.96 ppm and a C-H coupling
constant of 73 Hz at the carbyne carbon.12 At no time
during the warming of the sample from -85 °C to room
temperature could signals corresponding to 3a be
detected. Interestingly, reaction of the carbyne 1a with
HBF4 in the presence of phenylacetylene at low tem-
perature does result in formation of 2a . However, since
protonation of 1a yields the face-protonated complex
instead of 3a ,13,14 it is not yet clear what relationship
this pathway bears to either the oxidation chemistry of
1a or the Geoffroy results.15
experiments where 1 equiv of P(OPh)3 was added to the
reaction mixtures, the isolated yield of 2a rose to 51%.
Slow recrystallization of 2a in CH2Cl2/toluene (1:2)
resulted in golden-orange crystals that were suitable for
X-ray crystallography.8 A thermal ellipsoid diagram
appears in Figure 1. The crystal structure shows clearly
that the C2-C3 bond of the allyl ligand resulted from
carbon-carbon bond formation between the carbyne
carbon and phenylacetylene. The allyl ligand also bears
a P(OPh)3 moiety derived from addition of a second
phosphite to C1. Because the C1-C2 [1.476(5) Å] and
C2-C3 [1.427(5) Å] bond lengths differ as do the Mo-
C1 [2.297(3) Å] and Mo-C3 [2.363(4) Å] distances, the
coordination of the allyl ligand is best described as η1:
η2. In solution, complex 2a exists as a mixture of exo
and endo isomers in an 87:13 ratio, as determined by
1H NMR spectroscopy. NOE enhancement between the
protons on the C2 phenyl substituent and the Cp ring
allows assignment of the major isomer as exo.
(9) (a) Barluenga, J .; Aznar, F.; Mart´ın, A.; Garc´ıa-Granda, S.; Pe´rez-
Carren˜o, E. J . Am. Chem. Soc. 1994, 116, 11191-11192. (b) Fischer,
H.; Hofmann, J .; Mauz, E. Angew. Chem., Int. Ed. Engl. 1991, 30, 998-
999. (c) Schneider, K. J .; Neubrand, A.; van Eldik, R.; Fischer, H.
Organometallics 1992, 11, 267-269. (d) Fischer, H.; Do¨tz, K. H. Chem.
Ber. 1980, 113, 193-202. (e) Do¨tz, K. H. Chem. Ber. 1977, 110, 78-
85. (f) Do¨tz, K. H.; Pruskil, I. J . Organomet. Chem. 1977, 213, 115-
120. (g) Do¨tz, K. H.; Kreiter, C. G. J . Organomet. Chem. 1975, 99, 309-
314.
(10) (a) Do¨tz, K. H.; Fischer, H.; Hofmann, P.; Kreissl, F. R.;
Schubert, U.; Weiss, K. Transition Metal Carbene Complexes; Verlag
Chemie: Weinheim, 1983; pp 156-159. (b) Casey, C. P.; Polichnowski,
S. W. J . Am. Chem. Soc. 1977, 99, 6097-6098. (c) Casey, C. P.;
Polichnowski, S. W.; Shusterman, A. J .; J ones, C. R. J . Am. Chem.
Soc. 1979, 101, 7282-7292. (d) Bodnar, T.; Cutler, A. J . Organomet.
Chem. 1981, 213, C31-C36. (e) Fischer, H.; Reindl, D. J . Organomet.
Chem. 1990, 385, 351-361.
A similar reaction occurred between the phenyl car-
byne 1b and phenylacetylene in the presence of 1 equiv
(11) Garrett, K. E.; Sheridan, J . B.; Pourreau, D. B.; Feng, W. C.;
Geoffroy, G. L.; Staley, D. L.; Rheingold, A. L. J . Am. Chem. Soc. 1989,
111, 8383-8391.
(8) Crystal data for 2a : Orthorhombic, space group P212121, golden-
orange, a ) 13.4673(1) Å, b ) 19.1788(2) Å, c ) 20.3437(2) Å, R ) 90°,
â ) 90°, γ ) 90°, volume ) 5254.51(8) Å3, Z ) 4. A total of 695
parameters were refined in the final cycle of refinement using 11 064
reflections with I > 2σ(I) to yield R1 and wR2 of 4.07% and 9.60%,
respectively. GOF on F2 ) 1.108.
(12) (a) Holmes, S. J .; Schrock, R. R.; Churchill, M. R.; Wasserman,
H. J . Organometallics 1984, 3, 476-84. (b) Wengrovius, J . H.; Schrock,
R. R.; Churchill, M. R.; Wasserman, H. J . J . Am. Chem. Soc. 1982,
104, 1739-40. (c) Holmes, S. J .; Clark, D. N.; Turner, H. W.; Schrock,
R. R. J . Am. Chem. Soc. 1982, 104, 6322-6329. (d) J effrey, J . C.;
Weller, A. S. J . Organomet. Chem. 1997, 548, 195-203.

Oxidation of Metal Carbynes
Organometallics, Vol. 17, No. 20, 1998 4415
the carbyne solution keeping the temperature below -90 °C.
A dark violet-purple solution resulted. After 10 min triphenyl
phosphite (64.3 µL, 0.245 mmol) was added. After 15 min,
the solution was warmed to -78 °C for 35 min. The bath was
removed and the solution was allowed to warm to ambient
temperature, upon which the solution changed color to orange-
brown. Following removal of solvent in vacuo, acetylferrocene
was extracted with ether (3 × 8 mL). Addition of 2 mL of CH2-
Cl2 followed by 10 mL of ether resulted in the formation of a
brown powder. Removal of the filtrate afforded crude product
(193 mg, 73.7%). Analytically pure product could be obtained
after three successive recrystallizations from CH2Cl2/ether (134
mg, 51.0%). For 2a (exo:endo 87:13): 1H NMR (CDCl3) δ 6.59-
7.02 (m, 35H, Ph), 5.12 (s, 5H, C5H5, endo), 4.32 (s, 5H, C5H5,
exo), 3.72 (dd, 1H, CHP(OPh)3, J PH ) 3, 7.5 Hz), 2.83 (m, 1H,
CHCH2CH2CH2CH3), 2.21 (m, 1H, CHCH2CH2CH2CH3), 1.69
(m, 1H, CHCH2CH2CH2CH3) 1.58 (m, 2H, CH2), 1.39 (m, 2H,
CH2), 0.95 (t, 3H, CH3) ppm; 13C{1H} NMR (CD2Cl2) δ 237.1
(d, CO, J PC ) 30 Hz), 151.2 (d, Ph, J PC ) 9 Hz), 149.6 (d, Ph,
J PC ) 12 Hz), 140.7 (d, Ph, J PC ) 8 Hz), 131.3, 131.0, 130.5,
129.8, 128.7, 128.2, 128.1, 127.7, 126.5, 126.2, 125.2, 121.4 (d,
Ph, J PC ) 4 Hz), 120.7, 120.0 (d, Ph, J PC ) 4 Hz), 95.5 (C5H5,
exo), 91.4 (C5H5, endo), 84.0 (d, CPh, J PC ) 6 Hz), 62.3 (d,
CHCH2CH2CH2CH3, J PC ) 6 Hz), 34.4 (CHCH2CH2CH2CH3),
34.2 (dd, CHP(OPh)3, J PC ) 161, 20 Hz), 33.1, 22.9, 14.0 ppm;
31P{1H} NMR (CDCl3) δ 178.4 (d, J PP ) 13 Hz, exo), 162.5 (d,
In previous cases where we have generated interme-
diates of the type (η5-C5H5)(CO){P(OR)3}MdCHR+ via
oxidation of carbyne complexes, intramolecular rear-
rangement of the carbene ligand has been the dominant
process.1 These examples are the first where the
carbene could be intercepted in a bimolecular reaction.
Competition between H-shift and intermolecular trap-
ping has also been observed for the related electrophilic
carbenes Cp(CO)LFedCHCH2CH3+, in which cyclopro-
panation of olefins is slower than the H-shift to yield
propene,16 but insertion into Si-H bonds is faster than
the H-shift.17 Such competition between H-shift and
bimolecular reactivity is rare in highly electrophilic
carbenes with alkyl groups larger than methyl because
the H-shift is accelerated by increasing electron density
at the migration origin.16-18
Su m m a r y. We have demonstrated that one-electron
oxidation of molybdenum carbynes in the presence of
terminal alkynes results in H-abstraction and addition
of the alkyne to produce η1η2-allyl complexes as the final
products. Under these conditions, the expected H-shift
in the cationic carbene intermediate is not observed.
Exp er im en ta l Section
J PP ) 22 Hz, endo), 52.5 (d, J PP ) 21 Hz, endo), 49.8 (d, J PP
)
13 Hz, exo) ppm; IR (CH2Cl2) 1881 cm-1 (νCO); HRMS (FAB)
m/z calcd for M+ (C55H5198MoO7P2) 983.2179, found 983.2163.
Gen er a l. Standard inert atmosphere techniques were
used throughout. Hexane, petroleum ether, chloroform, and
methylene chloride were distilled from CaH2. Diethyl ether
and THF were distilled from Na/Ph2CO. All NMR solvents
were degassed by three freeze-pump-thaw cycles. Benzene-
d6 was vacuum transferred from Na/Ph2CO. CDCl3 was stored
over 3 Å molecular sieves. (η5-C5H5)(CO){P(OPh)3}MotCCH2-
CH2CH2CH3 (1a ) and (η5-C5H5)(CO){P(OPh)3}MotCC6H5 (1b)
were synthesized by adaptations of previously reported meth-
ods.5 Phenyl acetylene and 1-hexyne were vacuum distilled
from NaBH4. Triphenyl phosphite was purified by rinsing an
ethereal solution with 10% KOH and then brine. After drying
over Na2SO4 and removal of solvent, pure triphenyl phosphite
was obtained by vacuum distillation. All other starting
materials were purchased in reagent grade and used without
further purification.
[(η5-C5H5)(CO){P (OP h )3}Mo[η1:η2-CH{P (OP h )3}C(C6H5)d
CH(C6H5)](BF 4) (2b). Phenyl carbyne 1b (122 mg, 0.207
mmol) was mixed with phenyl acetylene (228 µL, 2.07 mmol)
in 30 mL of CH2Cl2. The solution was cooled to -95 °C. A
solution of acetylferrocenium tetrafluoroborate (62.0 mg, 0.197
mmol) in 20 mL of CH2Cl2 was slowly cannulated into the
carbyne solution keeping the temperature below -90 °C. A
dark brown violet-purple solution resulted. After 10 min
triphenyl phosphite (54.3 µL, 0.207 mmol) was added. After
reacting for 10 min, the solution was warmed to -78 °C for 2
h. The bath was removed and the solution was allowed to
warm to ambient temperature, upon which the solution
changed color to orange-brown. Following removal of solvent
in vacuo, acetylferrocene was extracted with ether (3 × 8 mL).
Addition of 2 mL of CH2Cl2 followed by 10 mL of hexane
resulted in the formation of a brown powder of the crude
product (165 mg, 73.2%). Analytically pure product could be
obtained after two successive recrystallizations from CH2Cl2/
ether (88.0 mg, 39.0%). For 2b (exo:endo 90:10): 1H NMR (CD2-
Cl2) δ 6.59-7.47 (m, 40H, Ph), 5.03 (s, 5H, C5H5, endo), 4.45
(s, 5H, C5H5, exo), 3.61 (s, 1H, CHPh), 3.45 (dd, 1H, CHP-
(OPh)3, J PH ) 4, 9 Hz) ppm; 13C{1H} NMR (CD2Cl2) δ 237.7
(d, CO, J PC ) 31 Hz), 151.1 (d, Ph, J PC ) 9 Hz), 149.6 (d, Ph,
J PC ) 12 Hz), 140.3 (d, Ph, J PC ) 6 Hz), 137.9, 131.1, 130.6,
130.5, 130.2, 130.0, 128.9, 128.4, 127.9, 127.7, 126.3, 121.5 (d,
Ph, J PC ) 5 Hz), 119.7 (d, Ph, J PC ) 5 Hz), 96.9 (C5H5, exo),
92.0 (C5H5, endo), 82.1 (CC6H5), 59.4 (CHC6H5), 35.0 (dd, CHP-
(OPh)3, J PC ) 159, 20 Hz) ppm; 31P{1H} NMR (CDCl3) δ 177.1
(d, J PP ) 23 Hz), 49.9 (d, J PP ) 23 Hz) ppm; IR (CH2Cl2) 1885
cm-1 (νCO); HRMS (FAB) m/z calcd for M+ (C57H4798MoO7P2)
1003.187, found 1003.195.
1
1H, 31P, and H NMR spectra were recorded on Gemini-300,
VXR-300, and UNITY 500 NMR spectrometers. IR spectra
were recorded on a Perkin-Elmer 1600 spectrometer. High-
resolution mass spectrometry was performed by the University
of Florida analytical service.
[(η5-C5H5)(CO){P (OP h )3}Mo[η1:η2-CH{P (OP h )3}C(P h )d
CH(CH2CH2CH2CH3)](BF 4) (2a ). Butyl carbyne 1a (140 mg,
0.245 mmol) was mixed with phenylacetylene (270 µL, 2.45
mmol) in 20 mL of CH2Cl2. The solution was cooled to -95
°C. A solution of acetylferrocenium tetrafluoroborate (73.4 mg,
0.233 mmol) in 25 mL of CH2Cl2 was slowly cannulated into
(13) Protonation experiments using the related carbyne complex (η5-
C5H5){P(OPh)3}2MotC-CH2tBu have been interpreted in terms of
initial protonation at the carbyne carbon followed by irreversible
conversion to the metal hydride.14 If 1a were to initially protonate at
the carbyne carbon to yield 3a , rearrangment of 3a to 4 would have to
be faster than formation of 1-pentene from 3a under these conditions.
This is highly unlikely since 4 has never been observed following
generation of 3a under oxidative conditions.
[(η5-C5H5)(CO){P (OP h )3}Mo[η1:η2-CH{P (OP h )3}C(CH2-
CH2CH2CH3)dCH(CH2CH2CH2CH3)](BF 4) (2c). Butyl car-
byne 1a (101 mg, 0.177 mmol) was mixed with 1-hexyne (204
µL, 1.77 mmol) in 20 mL of CH2Cl2. The solution was cooled
to -95 °C. A solution of acetylferrocenium tetrafluoroborate
(53.0 mg, 0.168 mmol) in 25 mL of CH2Cl2 was slowly
cannulated into the carbyne solution keeping the temperature
below -90 °C. A dark violet-purple solution resulted. After
20 min triphenyl phosphite (46.5 µL, 0.177 mmol) was added.
The solution was warmed to -78 °C for 20 min. The bath was
removed and the solution was allowed to warm to ambient
(14) Bottrill, M.; Green, M.; Orpen, A. G.; Saunders: D. R.; Williams,
I. D. J . Chem. Soc., Dalton Trans. 1989, 511-518.
(15) Protonations of metal complexes with unsaturated ligands can
involve highly complex scenarios. See: Henderson, R. A. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 946-967.
(16) Brookhart, M.; Tucker, J . R.; Husk, G. R. J . Am. Chem. Soc.
1983, 105, 258-264.
(17) Scharrer, E.; Brookhart, M. J . Organomet. Chem. 1995, 497,
61-71.
(18) Roger, C.; Bodner, G. S.; Hatton, W. G.; Gladysz, J . A.
Organometallics 1991, 10, 3266-3274.

4416 Organometallics, Vol. 17, No. 20, 1998
Torraca et al.
temperature, upon which the solution changed color to orange-
brown. Following removal of solvent in vacuo, acetylferrocene
was extracted with ether (3 × 8 mL). Addition of 2 mL of CH2-
Cl2 followed by 10 mL of hexane resulted in the formation of
a brown powder. Dissolving the solid in 2 mL of CH2Cl2
followed by 15 mL of ether yielded the crude product (117 mg,
62.8%). Analytically pure product could be obtained after two
successive recrystallizations from CH2Cl2/hexanes (52.3 mg,
28.1%). For 2c (exo:endo 60:40): 1H NMR (CD2Cl2) δ 6.98-
7.52 (m, 30H, Ph), 5.08 (s, 5H, C5H5, endo), 4.62 (d, 5H, C5H5,
J PH ) 1.5 Hz, exo), 4.22 (m, 1H, CHCH2CH2CH2CH3, endo),
3.26 (dd, 1H, CHP(OPh)3, J PH ) 4, 14 Hz, exo), 3.17 (m, 1H,
CHCH2CH2CH2CH3, exo), 2.73 (d, 1H, CHP(OPh)3, J PH ) 12
Hz, endo) 2.21-2.51 (m), 2.10 (m), 1.94 (m), 1.77 (m), 1.60 (m),
1.34-1.49 (m), 0.98 (m), 0.63 (t, 3H) ppm; 13C{1H} NMR (CD2-
Cl2) δ 245.0 (d, CO, J PC ) 33 Hz, endo), 238.9 (d, CO, J PC ) 33
[(η5-C5H5)(CO){P (OP h )3}(H)MotCBu ](BF 4) (4). Butyl
carbyne 1a (201 mg, 0.353 mmol) was mixed with a 54%
solution of HBF4 in ether (48.7 µL, 0.353 mmol) in 10 mL of
CH2Cl2 at -95 °C. After 10 min, 30 mL of hexane at -95 °C
was added and an orange oil precipitated from solution. The
oil was rinsed with hexanes at -78 °C, and some of the
remaining solvent was removed in vacuo at -78 °C. Keeping
the temperature below -78 °C, 1 mL of CD2Cl2 was added.
The resulting solution was cannulated into an NMR tube for
spectral characterization at -40 °C. For 4: 1H NMR (CD2-
Cl2) δ 7.20-7.50 (m, 15H, Ph), 5.40 (s, 5H, C5H5), 2.33 (m, 1H),
2.07 (m, 1H), 1.52 (m, 1H), 1.44 (m, 1H), 1.21 (m, 2H), 0.79
(m, 3H), -2.82 (d, 1H, J PH ) 10 Hz) ppm; 13C{1H} NMR (CD2-
Cl2) δ 276.8 (d, J PC ) 12 Hz, MoC, J CH ) 73 Hz), 226.8 (d, J PC
) 22 Hz, CO), 149.9 (d, J PC ) 6 Hz), 130.8, 126.7, 121.2 (d,
J PC ) 4 Hz), 96.9 (Cp), 47.2, 30.4, 22.0, 13.5 ppm
Hz, exo), 152.1 (d, Ph, J PC ) 14 Hz, endo), 151.6 (d, Ph, J PC
9 Hz, exo), 150.4 (d, Ph, J PC ) 12 Hz, exo), 149.8 (d, Ph, J PC
)
)
Ack n ow led gm en t. We thank the National Science
Foundation (Grant CHE-9424134) for support of this
work. K.A.A. wishes to acknowledge the National Sci-
ence Foundation and the University of Florida for
funding the purchase of the X-ray equipment.
11 Hz, endo), 131.8, 131.3, 130.7, 130.5, 128.6, 127.9, 126.2,
125.9, 121.6 (d, Ph, J PC ) 4 Hz), 121.4, 120.1 (d, Ph, J PC ) 5
Hz), 103.2 (CH{P(OPh)3}CCH2CH2CH2CH3, endo), 93.8 (C5H5,
exo), 91.3 (C5H5, endo), 89.4 (CH{P(OPh)3}CCH2CH2CH2CH3,
exo), 66.1 (CHCH2CH2CH2CH3), 38.4, 34.6, 34.3, 33.7, 32.6,
31.7, 31.1, 28.1 (dd, CHP(OPh)3, J PC ) 166, 18 Hz, exo), 23.2,
23.0, 21.4 (d, CHP(OPh)3, J PC ) 145 Hz, endo), 14.0, 13.7 ppm;
31P{1H} NMR (CD2Cl2) δ 181.1 (s, exo), 168.3 (d, J PP ) 18 Hz,
endo), 49.4 (d, J PP ) 18 Hz, endo), 46.2 (s, exo) ppm; IR (CH2-
Su p p or tin g In for m a tion Ava ila ble: Tables of bond
distances, bond angles, positional parameters, and anisotropic
displacement parameters for 2a (16 pages). See any current
masthead page for ordering information and Web access
instructions.
Cl2) 1876 cm-1 (νCO); HRMS (FAB) m/z calcd for M+ (C53
-
H5598MoO7P2) 963.2492, found 963.2503.
OM980534X