Addition of a phenyl phosphinidene complex to conjugated diynes

Article abstract of DOI:10.1021/om9806040

Alkynyl-substituted phosphirenes are formed from the addition of PhPW(CO)₅ to 2,4-hexadiyne, 5,7-dodecadiyne, and 2,2,7,7-tetramethylocta-3,5-diyne. No bisphosphirenes are formed. Instead, but only for the 2,4-hexadiyne derivative, a second PhPW(CO)₅ inserts into the phosphirene ring to give a 2:1 mixture of cis- and trans-1,2-dihydro-1,2-diphosphetes. An X-ray structure determination, ab initio computed geometries, and NMR data are presented.

Full text of DOI:10.1021/om9806040

796
Organometallics 1999, 18, 796-799
Ad d ition of a P h en yl P h osp h in id en e Com p lex to
Con ju ga ted Diyn es
Bing Wang,† Kiet A. Nguyen,† G. Naga Srinivas,† Charles L. Watkins,†
Stephan Menzer,‡ Anthony L. Spek,‡ and Koop Lammertsma*,†,§
Department of Chemistry, University of Alabama at Birmingham, UAB Station,
Birmingham, Alabama 35294-1240, Bijvoet Center for Biomolecular Research, Crystal and
Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands,
and Department of Chemistry, Faculty of Science, Vrije Universiteit, De Boelelaan 1083,
1081 HV Amsterdam, The Netherlands
Received J uly 15, 1998
Summary: Alkynyl-substituted phosphirenes are formed
from the addition of PhPW(CO)5 to 2,4-hexadiyne, 5,7-
dodecadiyne, and 2,2,7,7-tetramethylocta-3,5-diyne. No
bisphosphirenes are formed. Instead, but only for the 2,4-
hexadiyne derivative, a second PhPW(CO)5 inserts into
the phosphirene ring to give a 2:1 mixture of cis- and
trans-1,2-dihydro-1,2-diphosphetes. An X-ray structure
determination, ab initio computed geometries, and NMR
data are presented.
to 1,3-diynes.8 Here we report our results for the
addition of PhPW(CO)5 to a set of different 1,3-diynes.
While these results are in line with Mathey’s experi-
mental observations, they do show important differ-
ences. In addition, we present an evaluation of the
electronic properties of the products using ab initio MO
theory.
Resu lts a n d Discu ssion
1,3-Diynes have become versatile building blocks with
broad appeal in organic, organometallic, and materials
chemistry.1 Not only is the conjugated diyne unit an
ideal “inert” rodlike spacer with conducting properties
but its reactivity toward carbenes2 and transition metals
is equally multifaceted.3 Our interest concerns the
susceptibility toward the transition metal-complexed
phosphinidenes, of which PhPW(CO)5 has carbene-like
properties.4 This species is generated in situ from the
7-phosphanorbornadiene precursor 15 and reacts with
double and triple bonds to give W(CO)5-complexed
phosphiranes and phosphirenes, respectively.5,6 Conju-
gated olefins give 1,2-cycloadditions and subsequent
epimerizations and rearrangements to products such as
phospholenes.6,7 During the course of this study Mathey
and co-workers reported on the addition of RPW(CO)5
Reaction of the diynes 2 (R ) Me, n-Bu, t-Bu) with 1
equiv of 1 in toluene at 55-60 °C using CuCl as catalyst
affords in all cases the expected alkynyl-substituted
phosphirenes in reasonable isolated yields, i.e., 66% for
3a , 55% for 3b, and 52% for 3c. The differentiation in
yields illustrates the effect of steric hindrance that the
alkyne substituents have on the cycloaddition efficiency.
For comparison, 2-butyne reacts with 1 to give phos-
phirene 4 in 85% yield.9 Mathey reported a 55% yield
for the reaction of 1 with diyne 2d (R ) Ph).8
Our next step was to add a second PhPW(CO)5 to the
remaining and presumed readily accessible triple bond
of 3 in the anticipation of forming bisphosphirenes 5.
However, none of the diynes 2a -c underwent such an
addition. Mathey made the same observation and found
instead that with the diynes 3e (R ) Ph) and 3f (R )
CH2OPh) the second R′PW(CO)5 group (R′ ) Me, allyl,
Bz, Ph) inserts into the phosphirene ring to give 1,2-
dihydro-1,2-diphosphetes with exclusive formation of
the cis isomer.8 Our results differ in two important
aspects. First, whereas reaction of 1 with 3a gives
indeed a C-P insertion, the resulting 1,2-dihydro-1,2-
diphosphete (6a ) is formed under the reaction conditions
(55 °C) in a 2:1 mixture of cis and trans isomers.
Heating the mixture increases this ratio to 4:1, which
suggests that the thermodynamically favored cis isomer
is formed (in part) by epimerization of one of the
P-centers. Apparently the insertion reaction leading to
the cis isomer does not go with the high regio- and
stereoselectivity as has been suggested.8 Second, the
alkynes 3b and 3c give neither a C-P insertion (like
3a ) nor a 1,2-addition in detectable yields. This lack of
† University of Alabama at Birmingham.
‡ Utrecht University.
§ Vrije University. Correspond to the author at this address.
(1) For reviews, see: (a) Modern Acetylene Chemistry; Stang, P. J .,
Diederich, F., Eds.; VCH Verlagsgesellschaft mbH: Weinheim, 1995.
(b) Polydiacetylenes, in Advances in Polymer Science Vol. 63; Cantow,
H.-J ., Ed.; Springer-Verlag: Berlin, 1984.
(2) Bao, J .; Wulff, W. D.; Fumo, M. J .; Grant, E. B.; Heller, D. P.;
Whitcomb, M. C.; Yeung, S.-M. J . Am. Chem. Soc. 1996, 118, 2166.
See also: Stephan, E.: Vo-Quang, L.; Vo-Quang, Y. C. R. Acad. Sci.,
Ser. C. 1971, 272, 1731. D’yakonov, I. A.; Kornilova, T. A.; Nizovkina,
T. V. Zh. Org. Khim. 1967, 3, 272.
(3) (a) Beckhaus, R.; Sang, J .; Englert, U.; Bohme, U. Organome-
tallics 1996, 15, 4731. (b) Rosenthal, U.; Pulst, S.; Arndt, P.; Ohff, A.;
Tillack, A.; Baumann, W.; Kempe, R.; Burlarkov, V. V. Organometallics
1995, 14, 2961. (c) Takahashi, T.; Xi, Z.; Obora, Y.; Suzuki, N. J . Am.
Chem. Soc. 1995, 117, 2665.
(4) Cowley, A. H. Acc. Chem. Res. 1997, 30, 445.
(5) Marinetti, A.; Mathey, F.; Fischer, J .; Mitschler, A. J . Am. Chem.
Soc. 1982, 104, 4484. Marinetti, A.; Mathey, F. Organometallics 1982,
1, 1488. 6. Lammertsma, K., Chand, P., Yang, S.-W., Hung, J .-T.
Organometallics 1988, 7, 1875. Hung, J .-T., Yang, S.-W., Chand, P.,
Gray, G. M., Lammertsma, K. J . Am. Chem. Soc. 1994, 116, 10966.
(6) Mathey, F. Angew. Chem., Int. Ed. Engl. 1987, 26, 275. Mari-
netti, A.; Mathey, F. Organometallics 1984, 3, 456.
(8) Tran Huy, N. H.; Ricard, L.; Mathey, F. Organometallics 1997,
16, 4501.
(7) Lammertsma, K.; Hung, J .-T. J . Org. Chem. 1992, 57, 6557.
Lammertsma, K.; Hung, J .-T. J . Org. Chem. 1993, 58, 1800. Wang,
B.; Lake, C. H.; Lammertsma, K. J . Am. Chem. Soc. 1996, 118, 1690.
(9) An X-ray structure of the 1,2-diphenyl-substituted phosphirene
has been reported; see: Marinetti, A, Mathey, F. J . Am. Chem. Soc.
1982, 104, 4484.
10.1021/om9806040 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/22/1999

Notes
Organometallics, Vol. 18, No. 4, 1999 797
F igu r e 1. ORTEP drawing of the molecular structure of
6a . Selected bond lengths (in Å) and bond angles (in deg):
W1-P1 2.482(2), W2-P2 2.482(2), P1-P2 2.271(3), P1-C2
1.824(9), P2-C3 1.833(8), C1-C2 1.492(13), C2-C3
1.340(12), C3-C4 1.407(12), C4-C5 1.200(13), C5-C6
1.465(15), P1-C2-C3 104.9(6), P2-C3-C2 104.6(6), P1-P2-
C3 75.1(3), P2-P1-C2 75.4(3), C1-C2-C3 128.8(8), C2-C3-
C4 129.7(8), C3-C4-C5 173.2(10), C4-C5-C6 177.0(10).
reactivity of both the alkynyl and the phosphirene group
is most surprising.
F igu r e 2. B3LYP/6-31G* optimized structures for 7 and
8. Upper values are bond lengths (in Å) for the methyl
derivatives (as shown), while the lower italic values are
for the structures without methyl groups.
the phosphirene ring and its alkynyl substituent. This
is evident from the 1.392 Å short C(2)-C(3) bond, which
connects the alkynyl group (d(CtC) ) 1.215 Å) with the
phosphirene ring (d(CdC) ) 1.307 Å), and from the
0.040 Å large difference in the two ring P-C bond
lengths, of which the PC(2) bond is the longest (1.880
Å). Methyl substitution has little effect, although the
P-Me group does reduce the longer PC(2) bond slightly
(i.e., by 0.013 Å). The reported X-ray structure for 3d
(R ) Ph; >PPhW(CO)5)8 gives a difference in PC bond
lengths of 0.017 Å and thus compares well with the
computed structure 7Me (R ) Me; >PH). This suggests
that indeed the alkynyl-induced conjugative weakening
of the proximal PC(2) bond underlies the ability of
PhPW(CO)5 to insert into the phosphirene ring of 3a .
As an aside we note, however, that this P-C insertion
to form phosphetes is by no means common. For
example, the related conjugative weakening of the distal
PC bond in alkylidenephosphiranes does not lead to
insertion of a phosphinidene.10 This may suggest that
the closeness of the weakened proximal PC bond with
the conjugated alkynyl group underlies the insertion
reaction of 3a . However, it is remarkable that neither
the n-butyl (3b) nor tert-butyl (3c) derivatives give
phosphinidene insertion into the phosphirene ring nor
We resorted to computations, using density functional
theory, and an X-ray structure determination of 6a
(Figure 1) for investigation of the structural and elec-
tronic properties. To bring the scope of the calculations
within manageable proportions, we eliminated the
W(CO)5 groups, replaced the P-Ph group for P-H or
P-Me, and used tC-CH3 or tC-H substituents to
compute 7 and 8 at the B3LYP/6-31G* level of theory
(Figure 2). These changes do not affect the analyses of
the electronic properties in these systems; the absence
of the transition metal complex merely elongates both
P-C bonds. Structure 7H shows delocalization between
(10) Krill, S.; Wang, B.; Hung, J .-T.; Horan, C. J .; Gray, G. M.;
Lammertsma, K. J . Am. Chem. Soc. 1997, 119, 8432.

798 Organometallics, Vol. 18, No. 4, 1999
Notes
Ta ble 1. Su m m a r y of Obser ved 31P a n d 13C NMR
Ch em ica l Sh ifts (in p p m ) for 3, 4, a n d 6, a n d GIAO
(B3LYP /6-31G*) Com p u ted 13C NMR Ch em ica l
Sh ifts (in p p m , Refer en ced a ga in st SiMe4) for 6
a n d 7a
phosphirene ring with the alkynyl group playing an
important supportive role. The formation of both the cis
and trans isomers of the 1,2-dihydro-1,2-diphosphete
illustrates this insertion reaction to occur with little
regio- and stereoselectivity. In fact, the trans form
isomerizes to the thermodynamically more stable cis
form. Ab initio calculations of structural parameters and
NMR chemical shifts in conjunction with an X-ray
structure determination illustrate the special electronic
effects in these systems.
compdb
P
C1
C2
C3
C4 CH3 (1) CH3 (4)
4
-157.4
-135.3
128.3
11.2
11.9
3a , Me
3b, n-Bu -136.5
3c, t-Bu -135.9
6a , Me
7H
7Me
8H
134.0 115.4 65.0 105.2
139.2 115.2 67.7 110.7 (29.6)
146.7 117.6 65.9 11.7 (35.3)
4.5
(22.3)
(29.5)
5.0
49.0, 43.0 157.2 133.5 75.0 99.8
19.7
110
128
147
158
104
107
132
126
64
64
72
72
94
99
76
85
16
6
6
Com p u ta tion a l Section
8Me
23
Electronic structure calculations were carried out
using the GAUSSIAN 94 suite of programs (G94).11 For
the density functional theory calculations we used
Becke’s three-parameter hybrid exchange functional
combined with the Lee-Yang-Parr correlation func-
tional, referred to as B3LYP. The structures were
calculated using the 6-31G* basis set and were verified
to be minima. Their NMR shielding tensors were
computed with the gauge-independent atomic orbital
method (GIAO), which is incorporated in G94, and these
are referenced against that of tetramethylsilane.
a
The carbon labels refer to those shown in structures 7 and 8.
b
Substituents on the alkynyl and phosphirene/phophete groups
are given.
addition to the remaining triple bond. Because, a priori,
there is no difference in electronic properties between
3b,c and 3a , we assume the n-butyl and tert-butyl
groups to sterically inhibit the approach of PhPW(CO)5
to the reactive center.
The X-ray structure of the major isomer of 6a has its
two W(CO)5 in a cis orientation. The 0.009 Å difference
between the two P-C bond lengths of its fully planar
four-membered ring is well within the error limits. The
1.407(12) Å short C(3)-C(4) bond, which connects the
alkynyl group (d(CtC) ) 1.200(13) Å) with the 1,2-
diphosphete ring (d(CdC) ) 1.340(12) Å), suggests some
resonance stabilization which is not reflected in the P-C
bond lengths. This resonance stabilization between the
double and triple bonds of cis-6a is supported on
comparison with the 1.44(1) Å long C(3)-C(4) bond in
the reported X-ray structure of cis-6d .8 This lengthening
of the C(3)-C(4) bond of 6d is undoubtedly caused by
the C-phenyl substituents, which provide more extended
resonance stabilization. The ab initio computed struc-
tures 8H and 8Me compare well with the X-ray struc-
ture of cis-6a .
Exp er im en ta l Section
NMR spectra were recorded on Bruker ARX 300 and
DRY400 FT-NMR spectrometers. Chemical shifts are refer-
enced in ppm to internal Me4Si for the 1H and 13C NMR spectra
and to external 85% H3PO4 for the 31P NMR spectra. Downfield
shifts are reported as positive. Mass spectra were recorded on
a HP 5985 at 70 eV. Melting points were determined on an
electrothermal melting point apparatus and are uncorrected.
Elemental analyses were performed by Atlantic Microlab, Inc.,
Norcross, GA. All materials were handled under an atmo-
sphere of dry, high-purity nitrogen. Reagents and solvents
were used as purchased, except for toluene, which was dried
over molecular sieves. Chromatographic separations were
performed on silica gel columns (230-400 mesh). The synthe-
sis of [5,6-dimethyl-2,3-bis(methoxycarbonyl)-7-phenyl-7-phos-
phanorbornadiene]pentacarbonyltungsten (1) and the general
procedure for the phosphinidene addition to olefins and
alkynes have been described in ref 5.
The 13C NMR spectrum of 3a contains four quater-
nary carbons with very different chemical shifts. These
were assigned by long-range HETCOR experiments and
confirmed by ab initio computed 13C NMR chemical
shifts, referenced against SiMe4. The GIAO chemical
shifts for methyl derivative 7Me (see Table 1), computed
at B3LYP/6-31G*, are in excellent agreement with the
experimental values of 3a . This validation of assign-
ments confirms the alkynyl carbons to have rather
different chemical shifts (∆δ ) 23-35 ppm). Also the
phosphirane carbons have markedly different chemical
shifts (∆δ ) 21-32 ppm). The calculated values show
the influence of methyl substitution (cf., 7Me vs 7H and
8Me vs 8H) to be modest and in the expected range.
The comparison between the observed and GIAO carbon
chemical shifts of the 1,2-dihydro-1,2-diphosphetes 6a
and 8Me is very reasonable, with the terminal alkyne
carbon having the most prominent difference in δ
values, i.e., δobs ) 100 vs δcalc ) 85 ppm. The influence
of methyl substitution in the computed chemical shifts
of this alkyne carbon is modest in both 7 and 8.
This study confirms that 1,3-diynes undergo only a
single phosphinidene addition. No other reactions are
found for the di-n-butyl and di-tert-butyl derivatives. In
contrast, the dimethyl derivative shows an insertion of
a second PhPW(CO)5 into the proximal C-P bond of the
3a : 66% isolated yield; mp 113-4 °C, light yellow. 31P
1
5
NMR: δ -135.3 (1J PW ) 271 Hz). H NMR: δ 2.02 (d, J PH
)
3
3.15 Hz, 3H, CH3), 2.32 (d, J PH ) 9.6 Hz, 3H, CH3), 7.27 (m,
5H, Ph). 13C NMR: δ 4.50 (s, CH3), 11.9 (d, J PC ) 6.1 Hz,
2
2
3
CH3), 65.0 (m, J PC ) 6.4 Hz, Ct), 105.3 (m, J PC ) 3.6 Hz,
Ct), 115.4 (s, 1J PC ≈ 0 Hz, Cd), 127.4 (d, 2J PC ) 10.4 Hz, o-Ph),
129.7 (d, 4J PC ) 2.2 Hz, p-Ph), 130.3 (d, 3J PC ) 15.9 Hz, m-Ph).
1
1
133.9 (d, J PC ) 13.0 Hz, i-Ph), 136.8 (s, J PC ≈ 0 Hz, Cd),
2
2
194.7 (d, cis CO, J PC ) 8.6 Hz), 196.3 (d, trans CO, J PC
)
31.7 Hz). Anal. Calcd for C17H11PWO5: C, 40.00; H, 2.16.
Found: C, 39.33; H, 2.26.
3b: 55% isolated yield, oil. 31P NMR: δ -136.5 (1J PW ) 268.5
Hz). 1H NMR: δ 0.89 (t, 3J HH ) 7.4 Hz, 3H, CH3), 0.90 (t, 3J HH
3
) 7.2 Hz, 3H, CH3), 1.41 (m, 4H, 2CH2), 1.56 (dp, J HH ) 6.9
5
3
4
Hz, J PH ) 0.98 Hz, 2H, CH2), 1.71 (dp, J HH ) 6.9 Hz, J PH
)
3
3
1.8 Hz, 2H, CH2), 2.49 (dt, J HH ) 6.6 Hz, J PH ) 3.0 Hz, 2H,
CH2), 2.75 (q, J HH ) 7.5 Hz, 2H, CH2), 7.21 (m, 5H, Ph). 13C
3
(11) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.; Petersson,
G. A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.;
Zakrzewski, V. G.; J . V. Ortiz, J . B. F.; Cioslowski, J .; Stefanov, B. B.;
Nanayakkara, A.; Challacombe, M.; Peng, C. Y.; Ayala, P. Y.; Chen,
W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts, R.; Martin,
R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .; Stewart, J .
P.; Head-Gordon, M.; Gonzalez, C.; Pople, J . A. GAUSSIAN94, Revision
B.1; Gaussian, Inc.: Pittsburgh, PA, 1994.

Notes
NMR: δ 13.9 (s, CH3), 14.1(s, CH3), 22.3 (d, J PC 2.0, CH2),
Organometallics, Vol. 18, No. 4, 1999 799
4
2
) 26.0 Hz), 198.2 (d, trans CO, J PC ) 27.2 Hz). Anal. Calcd
3
2
22.9 (s, CH2), 28.1 (d, J PC 5.6, CH2), 29.6 (d, J PC 4.0, CH2),
for C28H16P2W2O10: C, 35.67; H, 1.70. Found: C, 35.80; H, 1.74.
2
30.7 (s, CH2), 30.8 (s, CH2). 13C NMR δ 67.7 (d, J PC ) 6.1 Hz,
trans-6a : 31P NMR: δ 50.8 (1J PP ) 32.2 Hz, 1J PW ) 222.6 Hz),
3
1
1
Ct), 110.7 (d, J PC ) 3.8 Hz, Ct), 115.2 (d, J PC ) 2.8 Hz,
45.5 (1J PP 32.2, J PW ) 227.2 Hz).
2
4
Cd), 128.9 (d, J PC ) 10.5 Hz, o-Ph), 131.0 (d, J PC ) 2.5 Hz,
Cr ysta l d a ta for 6a : C28H16P2W2O10, Mr ) 942.06, yellow-
ish block-shaped crystals (0.20 × 0.30 × 0.50 mm), monoclinic,
space P21/c (no. 14), with a ) 15.5821(9) Å, b ) 11.0693(10)
Å, c ) 17.6238(13) Å, â ) 91.491(6)°, V )3038.8(4) A3, Z ) 4,
Fc ) 2.059 g/cm3, F(000) )1768, µ(Mo KR) ) 77.2 cm-1, 7202
measured reflections, 6970 independent, R(int) ) 0.055, θmax
) 27.5°, ω scan, T ) 150 K, Mo KR-radiation, graphite
monochromator, λ ) 0.710 73 Å, Enraf-Nonius CAD4T dif-
fractometer on rotation anode. Reflection data were corrected
for absorption using ψ-scan data (transmission range 0.56-
0.98). The structure was solved by Patterson techniques
(DIRDIF96) and refined on F2 using SHELXL97. Convergence
was reached at R1 ) 0.0449 for 5329 reflections with I > 2σ-
(I) (wR2 ) 0.129). A final difference map did not show
significant features other than residual absorption artifacts
near W.
3
1
p-Ph), 131.7 (d, J PC ) 15.7 Hz, m-Ph), 138.6 (d, J PC ) 3.1
Hz, Cd), 139.2 (d, 2J PC ) 16.5 Hz, i-Ph), 196.2 (d, cis CO, J PC
2
2
) 9.4 Hz), 198.4 (d, trans CO, J PC ) 31.7 Hz).
3c: 52% isolated yield, mp 68-9 °C, light yellow. 31P NMR:
δ -136.7 (1J PW ) 270 Hz). H NMR: δ 1.16 (s, 3CH3), 1.19 (s,
1
CH3), 1.24 (s, 2CH3), 7.35 (m, 5H, Ph). 13C NMR: δ 28.3 (s,
CH3), 29.0 (d, 3J PC ) 2.7, CH3), 29.5 (s, C-CH3), 30.7 (s, CH2),
2
30.9 (s, CH3), 31.0 (s, CH3), 35.3 (d, J PC ) 5.0, C-CH3), 65.9
2
1
(d, J PC ) 5.9 Hz, Ct), 111.4 (s, Ct), 117.6 (d, J PC ) 3.8 Hz,
2
2
Cd), 128.8 (d, J PC ) 10.5 Hz, o-Ph), 131.0 (d, J PC ) 2.3 Hz,
3
1
p-Ph), 131.5 (d, J PC ) 15.8 Hz, m-Ph), 139.2 (d, J PC ) 3.4
Hz, Cd), 146.8 (d, 1J PC ) 20.2 Hz, i-Ph), 196.4 (d, cis CO, J PC
2
) 8.6 Hz), 198.3 (d, trans CO, 2J PC ) 32.0 Hz). Anal. Calcd for
C
23H23PWO5: C, 46.46; H, 3.87. Found: C, 45.82; H, 3.88.
4: 85% isolated yield, mp 69-71 °C, light yellow. 31P NMR:
δ -157.4 (1J PW ) 266 Hz). 1H NMR: δ 2.20 (d, J PH ) 39.6
5
Atom coordinates, bond lengths and angles, and thermal
parameters have been deposited at the Cambridge Crystal-
lographic Data Center (CCDC). Any request to the CCDC for
this material should quote the full literature citation and the
reference number.
Hz, 6H, CH3), 7.20 (m, 5H, Ph). 13C NMR: δ 11.2 (d, J PC
)
)
)
2
1
2
27.9 Hz, CH3), 128.3 (d, J PC ) 9.7 Hz, i-Ph), 128.9 (d, J PC
10.3 Hz, o-Ph), 130.7 (d, J PC ) 3.2 Hz, p-Ph), 131.6 (d, J PC
2
3
15.9 Hz, m-Ph), 139.0 (d, 2J PC ) 3.4 Hz, Cd), 196.8 (d, cis CO,
2J PC ) 8.8 Hz), 198.8 (d, trans CO, 2J PC ) 29.8 Hz). Anal. Calcd
for C15H11PWO5: C, 37.04; H, 2.26. Found: C, 37.00; H, 2.35.
cis/tr a n s-6a . Reaction of 1 with isolated 3a in a 1:1 ratio
in toluene for 2 h at 55-60 °C, following the same procedure
as the alkyne additions, afforded a 2:1 mixture of cis- and
trans-6a in 75% isolated yield. cis-6a : mp 168-70 °C, yellow.
Ack n ow led gm en t. This work was supported by the
National Science Foundation under Grant CHE-9500344
and in part (A.L.S., S.M.) by The Netherlands Founda-
tion for Chemical Research (CW) with financial aid from
The Netherlands Organization for Scientific Research
(NWO).
31P NMR: δ 49.0 (1J PP ) 34.3 Hz, J PW ) 240 Hz), 43.0 (1J PP
1
1
1
3
) 34.3 Hz, J PW ) 237 Hz). H NMR: δ 2.37 (d, J PH ) 11.0
3
Hz, 3H, CH3), 2.07 (d, J PH ) 3.7 Hz, 3H, CH3), 7.61 (m, 10H,
Ph). 13C NMR: δ 4.96 (d, J PC ) 1.31 Hz, CH3), 19.7 (dd,2J PC
4
Su p p or tin g In for m a tion Ava ila ble: Crystal data, bond
lengths and angles, hydrogen atom positions, and isotropic and
anisotropic displacement parameters (25 pages). Ordering
information is given on any current masthead page.
3
2
3
) 2.86 Hz, J PC ) 5.28 Hz, CH3), 75.0 (dd, J PC ) 8.2 Hz, J PC
) 10.1 Hz, Ct), 99.8 (d, 3J PC ) 5.3 Hz, Ct), 128-131 (m, CPh),
133.5 (dd, 1J PC ) 33.7 Hz, 2J PC ) 19.9 Hz, Cd), 157.2 (dd, 1J PC
2
2
) 41.9 Hz, J PC ) 24.4 Hz, Cd), 196.1(d, cis CO, J PC ) 6.9
2
2
Hz), 196.2 (d, cis CO, J PC ) 7.5 Hz), 197.7(d, trans CO, J PC
OM9806040