X-ray structure and electrophilic reactivity of a cationic, chiral tungsten(II) methylene complex

Article abstract of DOI:10.1016/S0022-328X(00)00708-7

The structure of a tungsten(II) methylene complex, [Tp′(CO)(PhCCMe)W=CH₂][BAr′₄] (2a), was obtained by taking advantage of the stabilizing, weakly coordinating counterion, BAr′₄^-, to form X-ray quality single crystals. The electrophilic reactivity of [Tp′(CO)(PhCCMe)W=CH₂][PF₆] (2b) was surveyed with both neutral nucleophiles (triphenylphosphine and pyridine) and anionic nucleophiles (formed by deprotonation of phthalimide, diethyl malonate, t-butyl acetoacetate, and acetophenone) to give derivatives of the form [Tp′(CO)(PhCCMe)W-CH₂-Nu]^+,0. Crystal structures obtained for the phthalimide (5) and diethyl malonate (6) adducts are compatible with attack of the nucleophile from along the metal CO axis. The stereochemistry of the t-butyl acetoacetate adduct was determined by 2-D NOESY-NMR. Reaction of methylene carbene 2b with cyclohexene sulfide results in sulfur atom transfer to form a rare π-bound thioformaldehyde complex (9).

Full text of DOI:10.1016/S0022-328X(00)00708-7

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 617–618 (2001) 520–529
X-ray structure and electrophilic reactivity of a cationic, chiral
tungsten(II) methylene complex
Aase S. Jepsen, Neil J. Vogeley, Peter S. White, Joseph L. Templeton *
W.R. Kenan, Jr., Laboratory, Department of Chemistry, The Uni6ersity of North Carolina, Chapel Hill, NC 27599-3290, USA
Received 7 August 2000; accepted 27 September 2000
Abstract
The structure of a tungsten(II) methylene complex, [Tp%(CO)(PhCCMe)WꢀCH2][BAr4%] (2a), was obtained by taking advantage
of the stabilizing, weakly coordinating counterion, BAr´4−, to form X-ray quality single crystals. The electrophilic reactivity of
[Tp%(CO)(PhCCMe)WꢀCH2][PF6] (2b) was surveyed with both neutral nucleophiles (triphenylphosphine and pyridine) and anionic
nucleophiles (formed by deprotonation of phthalimide, diethyl malonate, t-butyl acetoacetate, and acetophenone) to give
derivatives of the form [Tp%(CO)(PhCCMe)WꢁCH2ꢁNu]+,0. Crystal structures obtained for the phthalimide (5) and diethyl
malonate (6) adducts are compatible with attack of the nucleophile from along the metal CO axis. The stereochemistry of the
t-butyl acetoacetate adduct was determined by 2-D NOESY-NMR. Reaction of methylene carbene 2b with cyclohexene sulfide
results in sulfur atom transfer to form a rare p-bound thioformaldehyde complex (9). © 2001 Elsevier Science B.V. All rights
reserved.
Keywords: Hydridotris(3,5-dimethylpyrazolyl)borate; Tungsten; Methylene; Electrophilic; Carbene; Thioformaldehyde
1. Introduction
gated by Gladysz et al. display extensive chemistry at
the carbene carbon [28,41,42]. This cationic rhenium
carbene complex serves as a paradigm for Fischer reac-
tivity patterns. Nucleophiles attack the benzylidene car-
bene stereospecifically to give one set of diastereomers
[43]. Diazo compounds add stereoselectively to form
olefin complexes [44].
We have reported the chiral methylene complex,
[Tp%(CO)(PhCCMe)WꢀCH2][PF6] (2b) (Tp%=hydrido-
tris(3,5-dimethylpyrazolyl)borate) [45]. The [Tp%(CO)-
(PhCCMe)WꢀCH2]+ cation was shown to transfer the
methylene fragment to olefins, and it also catalyzed the
formation of aziridines from N-arylimines and ethyl
diazoacetate [46]. Reaction of carbene 2b with excess
base forms a C3H5 bridged dimer [47]. Here we report
the X-ray crystal structure of the parent, cationic meth-
ylene carbene complex with the bulky BAr´4− (tetrakis-
(bis (3,5-trifluoromethyl)phenyl)borate) counterion [48,
49]. In addition, we have surveyed the reactivity of the
electrophilic carbene, [Tp%(CO)(PhCCMe)WꢀCH2][PF6]
(2b), with neutral nucleophiles, anionic nucleophiles,
and the sulfur atom transfer reagent, cyclohexene
sulfide.
Discovery of the heteroatom stabilized, electrophilic
carbene complex, (CO)5WꢀC(OCH3)Ph, in 1964 [1] has
been followed by utilization of carbene complexes [2] as
carbene transfer reagents [3–6], as catalysts in both
olefin metathesis [7–12] and ROMP [13–16], and as
proposed intermediates in the Fischer–Tropsch synthe-
sis [17,18]. Pettit and Jolly suggested the presence of an
electrophilic methylene carbene, [CpFe(CO)2ꢀCH2]+, in
the reaction of CpFe(CO)2(CH2OCH3) with acid in the
presence of cyclohexene to produce norcarane [19]. In
1975, Schrock reported the first isolable methylene
complex, Cp2(CH3)TaꢀCH2 [20]. Unlike the elec-
trophilic Fisher carbenes, this complex exhibited nucle-
ophilic behavior. Although methylene complexes
remain relatively rare [21–40], both nucleophilic [37–
40] and electrophilic [28–36] methylene complexes have
been reported.
The chiral carbene complexes [(h5-C5H5)Re(NO)-
(PPh3)(ꢀCHR)][PF6] (R=H, alkyl, or phenyl) investi-
* Corresponding author. Tel.: +1-919-9664575; fax: +1-919-
9664575.
E-mail address: joetemp@unc.edu (J.L. Templeton).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00708-7

A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
521
Table 1
Crystallographic data and collection parameters for [Tp%(CO)(PhCCMe)WꢀCH2][BAr4% ] (2a), Tp%(CO)(PhCCMe)WCH2-phthalimide (5), and
Tp%(CO)(PhCCMe)WCH2CH(COOEt)2 (6)
2a
5
6
Formula
C58H44N6OB2F24
1502.44
Triclinic
0.30×0.20×0.20
P1
W
C34H36N7O3BW
785.35
Monoclinic
0.40×0.20×0.05
P21/n
C33H43N6O5BW
798.39
Monoclinic
0.35×0.20×0.10
P21/c
Molecular weight (g mol−1
Crystal system
)
Crystal dimensions (mm)
Space group
,
a (A)
12.7471(6)
13.2602(6)
18.6748(9)
87.294(1)
80.273(1)
76.125(1)
3020.35(25)
2
14.4533(7)
14.7039(7)
15.2072(7)
15.3286(7)
17.7713(8)
12.6318(6)
,
b (A)
,
c (A)
a (°)
b (°)
k (°)
95.5050(10)
93.496(1)
3
,
V (A )
3216.9(3)
4
1.622
1566.64
3634.6(3)
4
1.544
1606.69
Z
Dcalc (g cm−3
F(000)
)
1.652
1484.25
Temperature (°C)
−100
−100
−100
,
Radiation (u, A)
Mo–Ka (0.71073)
3.00BqB55
2.03
Mo–Ka (0.71073)
3.00BqB60.00
3.64
Mo–Ka (0.71073)
3.00BqB60.00
3.42
2q range (°)
v (mm−1
)
h, k, l ranges
−15, 16; 0, 17; −24, 24
−19, 19; 0, 20; 0, 20
−21, 21; 0, 23; 0, 16
Scan mode
ꢀ
ꢀ
ꢀ
Total no. of data
Total no. of unique data
No. of observed data (I\3.0|(I))
RF
Rw
Goodness-of-fit
Parameters
Max. shift (s)
37196
13902
9312
0.059
0.071
1.85
41519
8677
6044
0.041
0.031
1.07
415
43993
9131
6584
0.051
0.051
1.66
416
829
0.020
0.000
0.002
2. Results and discussion
2.1. Carbene structure
Replacement of the PF−6 counterion with BAr4´ − in
the preparation of the methylene complex was accom-
plished by reaction of the carbene precursor tungsten
methyl complex (1) with [Ph3C][BAr%] [50] (Eq. (1)).
4
The large BAr´4− anion has been reported to stabilize
electrophilic cations [51], and indeed, this anion af-
forded X-ray quality crystals of the complex cation
from slow diffusion of hexanes into a CH2Cl2 solution
(1)
of [Tp%(CO)(PhCCMe)WꢀCH2][BAr%] (2a) (Table 1). A
2.2. Reactions with neutral nucleophiles
4
labeled ORTEP of 2a is shown in Fig. 1, and selected
bond distances and angles are shown in Table 2. The
Carbene 2b has been shown to add PMe3 at the
electrophilic carbene carbon [46]. To extend the range
of neutral nucleophiles that form cationic adducts, the
bulkier triphenylphosphine phosphorus donor and the
nitrogen donor, pyridine, were allowed to react with
carbene 2b (Eq. (2)). Triphenylphosphine reacts with
,
WꢁC(1) bond distance is 2.018(8) A, which is in the
middle of the range for a tungsten carbene bond [52–
55]. The alkyne is oriented parallel to the CO as is seen
in other complexes of this type [56]. Due to the comple-
mentary p bonding interactions of the alkyne and car-
bonyl ligand, the methylene protons will strongly prefer
to be perpendicular to the WꢁCO axis [46].
carbene 2b (wCO=2066 cm−1
,
KBr) to give
[Tp%(CO)(PhCCMe)WꢁCH2PPh3][PF6] (3) which has a

522
A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
(2)
Fig. 2. ORTEP diagram of Tp%(CO)(PhCCMe)WꢁCH2-phthalimide (5).
carbonyl stretch of 1895 cm−1 in the IR spectrum,
slightly higher than in [Tp%(CO)(PhCCMe)W-
CH2PMe3][PF6] (wCO=1888 cm−1, KBr). The 1H-
NMR spectrum of the triphenylphosphine adduct 3
shows the diastereotopic methylene hydrogens as a
coincidental triplet at 2.55 ppm (2JHH=2JPH=14,
2JWH=10 Hz, 183W, 14% abundance) and a doublet of
2
doublets at 1.38 ppm (2JHH=14, JPH=22 Hz). Reac-
tion of carbene 2b with excess pyridine forms
[Tp%(CO)(PhCCMe)WꢁCH2ꢁNC5H5][PF6] (4). The car-
bonyl stretching frequency of the pyridine adduct is at
1881 cm−1, slightly lower than in the phosphine ad-
ducts, and the diastereotopic hydrogens resonate as
doublets at 4.47 (2JHH=14, 2JWH=11 Hz) and 4.06
Fig. 1. ORTEP diagram of [Tp%(CO)(PhCCMe)WꢀCH2][BAr%4] (2a).
Table 2
Selected
,
bond
distances
(A)
and
angles
(°)
for
ppm (2JHH=14, JWH=7 Hz) in the H-NMR spec-
trum. The directions of the terminal metal carbonyl
shifts are in accord with expectations, but the CH2
spacer between the metal and the Lewis base buffers the
influence of the donor group dramatically compared to
the effect of direct metal ligation by either phosphorus
or nitrogen donors on metal carbonyl frequencies.
2
1
[Tp%(CO)(PhCCMe)WꢀCH2][BAr4% ] (2a)
Bond distances
W(1)ꢁC(1)
W(1)ꢁC(2)
W(1)ꢁC(5)
W(1)ꢁC(6)
W(1)ꢁN(21)
W(1)ꢁN(31)
2.018(8)
2.048(8)
2.089(9)
2.040(8)
2.182(6)
2.247(6)
W(1)ꢁN(41)
2.232(6)
C(2)ꢁO(3)
C(4)ꢁC(5)
C(5)ꢁC(6)
C(6)ꢁC(11)
1.131(11)
1.461(13)
1.302(13)
1.455(13)
Bond angles
2.3. Reactions with anionic nucleophiles
C(1)ꢁW(1)ꢁC(2)
C(1)ꢁW(1)ꢁC(5)
C(1)ꢁW(1)ꢁC(6)
C(1)–W(1)ꢁN(21) 89.8(3)
C(1)ꢁW(1)ꢁN(31) 86.6(3)
C(1)ꢁW(1)ꢁN(41) 164.7(3)
C(2)ꢁW(1)ꢁC(5)
C(2)ꢁW(1)ꢁC(6)
C(2)ꢁW(1)ꢁN(21) 168.7(3)
C(2)ꢁW(1)ꢁN(31) 85.4(3)
C(2)ꢁW(1)ꢁN(41) 92.9(3)
89.6(3)
93.2(3)
105.4(3)
C(5)ꢁW(1)ꢁN(41) 101.8(3)
C(6)ꢁW(1)ꢁN(21) 85.8(3)
C(6)ꢁW(1)ꢁN(31) 163.8(3)
C(6)ꢁW(1)ꢁN(41) 88.5(3)
N(21)ꢁW(1)ꢁN(31) 83.33(23)
N(21)ꢁW(1)ꢁN(41) 84.75(21)
N(31)ꢁW(1)ꢁN(41) 78.59(21)
Carbene 2b reacts with anionic nucleophiles to form
neutral adducts by addition of the nucleophile to the
carbene carbon. Deprotonation of phthalimide with
n-butyl lithium in THF provides an anionic nitrogen
donor, and subsequent reaction with carbene 2b leads
to the formation of Tp%(CO)(PhCCMe)WꢁCH2ꢁ
phthalimide (5) (Eq. (3)). The terminal metal carbonyl
stretch in the IR spectrum is at 1883 cm−1, nearly
identical to the frequency of the cationic pyridine ad-
duct. The phthalimide CꢀO infrared absorption is at
1692 cm−1. Crystals of 5 suitable for X-ray analysis
70.5(4)
105.2(4)
W(1)ꢁC(2)ꢁO(3)
W(1)ꢁC(5)ꢁC(4)
W(1)ꢁC(5)ꢁC(6)
C(4)ꢁC(5)ꢁC(6)
W(1)ꢁC(6)ꢁC(5)
W(1)ꢁC(6)ꢁC(11)
C(5)ꢁC(6)ꢁC(11)
176.1(8)
149.7(7)
69.6(5)
140.6(9)
73.7(6)
C(5)ꢁW(1)ꢁC(6)
C(5)ꢁW(1)ꢁN(21) 120.8(3)
C(5)ꢁW(1)ꢁN(31) 155.9(3)
36.7(4)
146.3(7)
139.8(9)

A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
523
(3)
Table 3
Selected
were obtained by slowly cooling a saturated solution of
,
bond
distances
(A)
and
angles
(°)
for
the phthalimide adduct (5) in acetone. The crystal
structure of Tp%(CO)(PhCCMe)WꢁCH2-phthalimide (5)
is shown in Fig. 2, and selected bond distances and
angles are listed in Table 3. The WꢁC(6) bond length of
Tp%(CO)(PhCCMe)WCH2-phthalimide (5)
Bond distances
W(1)ꢁC(1)
W(1)ꢁC(4)
W(1)ꢁC(5)
W(1)ꢁC(6)
W(1)ꢁN(31)
W(1)ꢁN(41)
1.945(4)
2.055(4)
2.031(4)
2.223(4)
2.221(3)
2.272(3)
W(1)–N(51)
C(1)–O(2)
C(3)–C(4)
C(4)–C(5)
C(5)–C(11)
C(6)–N(21)
2.278(3)
1.174(5)
1.493(6)
1.310(6)
1.462(6)
1.467(5)
,
2.223(4) A, is significantly longer than the tungsten
,
carbon double bond distance of 2.018(8) A in carbene
reagent 2b and is typical of WꢁC single bonds [57–59].
The C(6)ꢁN(21) bond length is 1.467(5) A and the
,
WꢁC(6)ꢁN(21) angle is 124.7(3)°. This large bond angle
indicates a distorted tetrahedral geometry at C(6) to
accommodate the large W and N substituents along
with the two hydrogens. The location of the added
nucleophile in the solid state positions the large phthal-
imide substituent on the metal bound carbon near the
CO rather than near the sterically bulky Tp%. This
geometry is compatible with the incoming nucleophile
attacking the carbene carbon from along the CO axis,
since attack from the opposite carbene face would be
hindered by the projecting 3-methyl substituents on
Tp%. Although the solid state structure need not reflect
the site of nucleophilic attack, the preference for locat-
ing the bulky substituents away from the pendant Tp%
methyl groups is clear.
Bond angles
C(1)ꢁW(1)ꢁC(4)
C(1)ꢁW(1)ꢁC(5)
C(1)ꢁW(1)ꢁC(6)
C(1)ꢁW(1)ꢁN(31)
70.16(17)
106.87(16)
95.97(15)
95.42(14)
C(6)–W(1)–N(31) 160.09(13)
C(6)–W(1)–N(41)
C(6)–W(1)–N(51)
81.63(13)
86.37(13)
N(31)–W(1)–N(41) 83.82(12)
N(31)–W(1)–N(51) 78.35(11)
N(41)–W(1)–N(51) 82.75(11)
C(1)ꢁW(1)ꢁN(41) 167.88(14)
C(1)ꢁW(1)ꢁN(51)
C(4)ꢁW(1)ꢁC(5)
C(4)ꢁW(1)ꢁC(6)
C(4)ꢁW(1)ꢁN(31)
C(4)ꢁW(1)ꢁN(41) 121.92(14)
C(4)ꢁW(1)ꢁN(51) 155.15(14)
C(5)ꢁW(1)ꢁC(6)
C(5)ꢁW(1)ꢁN(31)
C(5)ꢁW(1)ꢁN(41)
85.25(14)
37.39(16)
99.32(15)
99.89(13)
W(1)–C(1)–O(2)
W(1)–C(4)–C(3)
W(1)–C(4)–C(5)
C(3)–C(4)–C(5)
W(1)–C(5)–C(4)
176.3(3)
149.7(3)
70.32(23)
139.9(4)
72.29(24)
102.52(15)
89.70(13)
85.24(14)
W(1)–C(5)–C(11) 146.5(3)
C(4)–C(5)–C(11) 141.1(4)
W(1)–C(6)–N(21) 124.7(3)
C(5)ꢁW(1)ꢁN(51) 163.87(14)
hydrogens of the WꢁCH2ꢁC linkage as doublets of
doublets at 0.95 and 1.84 ppm. Likewise, the ethyl
groups of the malonate moiety are inequivalent with
the two distinct CH3 groups appearing as triplets at
1.14 and 1.25 ppm. One of the CH2 groups is a
coincidental quartet, but the other diastereotopic ethyl
CH2 group is a multiplet. A selective decoupling exper-
iment was performed by saturating the methyl signal at
1.25 ppm. This revealed an AB spin system for the
adjacent methylene with resonances at 4.150 and 4.146
ppm. The geminal coupling between these protons is 17
Hz, while coupling to the adjacent methyl group is 7 Hz
in this ABX3 spin system.
Deprotonation of t-butyl acetoacetate with n-butyl
lithium and subsequent reaction of the stabilized carb-
anion with carbene 2b yields adduct 7 (Eq. (5)). The
metal carbonyl stretch appears at 1877 cm−1 in the IR
spectrum, slightly higher than the metal carbonyl fre-
quency in the malonate adduct. The ketone and ester
CꢀO infrared stretches of the t-butyl acetoacetate ap-
pear at 1715 and 1696 cm−1. The diastereotopic meth-
ylene protons in the 1H-NMR spectrum of 7 are
doublets of doublets at 1.68 and 1.07 ppm (2JHH=14
(4)
Reaction of carbene 2b with deprotonated diethyl
malonate yields a carbon–carbon bond in adduct 6
(Eq. 4), and the metal carbonyl infrared stretch drops
to 1866 cm−1, well below other adducts. The malonate
ester CꢀO infrared absorption is observed at 1725
cm−1. Crystals for X-ray analysis were obtained from
slow diffusion of hexanes into a methylene chloride
solution of the malonate adduct (6). The ORTEP dia-
gram is shown in Fig. 3 and selected bond distances
and angles are listed in Table 4. The WꢁC(21) bond
,
length is 2.197(7) A and the WꢁC(21)ꢁC(22) bond angle
is 121.9(4)°, similar to the parameters observed for the
phthalimide product. The H-NMR spectrum of mal-
onate adduct 6 shows the diastereotopic methylene
1

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A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
(5)
Table 4
,
Selected bond distances (A) and angles (°) for Tp%(CO)(PhCCMe)-
WCH2CH(COOEt)2 (6)
Bond distances
W(1)–C(2)
W(1)–C(3)
W(1)–C(4)
W(1)–C(21)
W(1)–N(41)
W(1)–N(51)
W(1)–N(61)
2.052(6)
2.014(6)
1.934(6)
2.197(7)
2.232(5)
2.267(5)
2.280(5)
C(1)–C(2)
C(2)–C(3)
1.488(10)
1.310(9)
1.473(8)
1.175(8)
1.542(9)
1.504(10)
1.530(10)
C(3)–C(11)
C(4)–O(5)
C(21)–C(22)
C(22)–C(23)
C(22)–C(28)
Bond angles
C(2)–W(1)–C(3)
C(2)–W(1)–C(4)
C(2)–W(1)–C(21)
C(2)–W(1)–N(41)
C(2)–W(1)–N(51) 121.02(21)
C(2)–W(1)–N(61) 157.12(21)
C(3)–W(1)–C(4)
C(3)–W(1)–C(21)
C(3)–W(1)–N(41)
C(3)–W(1)–N(51)
C(3)–W(1)–N(61) 160.21(21)
C(4)–W(1)–C(21)
C(4)–W(1)–N(41)
C(4)–W(1)–N(51) 168.06(22)
C(4)–W(1)–N(61) 88.45(21)
C(21)–W(1)–N(41) 159.72(20)
C(21)–W(1)–N(51) 82.98(20)
37.6(3)
69.7(3)
100.96(24)
99.27(22)
C(21)–W(1)–N(61)
N(41)–W(1)–N(51)
N(41)–W(1)–N(61)
N(51)–W(1)–N(61)
W(1)–C(2)–C(1)
W(1)–C(2)–C(3)
C(1)–C(2)–C(3)
W(1)–C(3)–C(2)
W(1)–C(3)–C(11)
C(2)–C(3)–C(11)
W(1)–C(4)–O(5)
C(3)–C(11)–C(12)
W(1)–C(21)–C(22)
C(21)–C(22)–C(23)
C(21)–C(22)–C(28)
C(23)–C(22)–C(28)
85.19(20)
85.34(19)
76.70(17)
81.43(17)
150.4(5)
69.6(4)
106.8(3)
139.9(6)
72.8(4)
106.82(24)
88.43(21)
84.46(22)
147.4(5)
138.8(6)
177.2(5)
120.9(6)
121.9(4)
116.0(5)
109.3(5)
109.3(6)
Fig. 3. ORTEP of Tp%(CO)(PhCCMe)WCH2CH(COOEt)2 (6).
3
89.9(3)
98.53(24)
Hz, JHH=7 Hz) and the methyne proton is a triplet at
3.50 ppm (3JHH=7 Hz). Although adduct 7 has two
stereogenic centers, the metal and the b carbon, only
1
one diastereomer is evident by H-NMR in the crude
reaction mixture.
The structure of adduct 7 was assigned by 2-D
NOESY and comparison with the crystal structure of
the malonate adduct 6. NOESY has been shown to be
quite useful for determination of orientation and stere-
ochemistry in complexes involving Tp%. This is due to
the close proximity of three of the Tp% methyl groups to
the ancillary ligands. These methyl groups act as re-
porters that help determine the location of the other
ligands [60,61].
with the Tp% methyl signals at 2.95 and 1.35 allow for
complete assignment of the orientation and stereochem-
istry of the single diastereomer of adduct 7. Fig. 4
shows a Newman projection along the CaꢁCb bond
with the Tp% methyl groups shown as small circles and
the NOE correlations indicated by arrows.
In the crystal structure of 6, one ester group is
between the Tp% methyl groups and the other is near the
alkyne, not the metal carbonyl. This gave a good first
approximation of the structure of the major
diastereomer of 7. The t-butyl ester should prefer to be
between the Tp% methyl groups because of its size and
the acyl group should then be near the alkyne by
analogy to the malonate adduct. This structure was
confirmed by NOESY. The phenyl and methyl signals
from the alkyne give strong correlations to the Tp%
methyl groups at 1.67 and 1.35 ppm. The acyl protons
give strong correlations to the Tp% methyl group at 1.35
ppm and to the alkyne. Correlations of the t-butyl ester
Fig. 4. Newman projection of 7 showing NOE correlations.

A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
525
Reaction of carbene 2b with deprotonated acetophe-
none gives product 8 (Eq. (6)). The metal carbonyl
stretch in the IR spectrum is at 1847, and the acetophe-
none ketone infrared absorption is at 1671 cm−1. Both
methylene groups have diastereotopic hydrogens, and
each hydrogen could appear as a doublet of doublets of
doublets if all of the coupling constants differ signifi-
cantly. A typical pattern for one hydrogen of these four
tris(pyrazolyl)borate) ligand gave both s and p-bound
1
aldehydes [67,68]. The H-NMR spectrum of the thio-
formaldehyde complex 9 shows the two diastereotopic
methylene protons as singlets at 6.09 and 4.83 ppm. The
absence of geminal JHH coupling is not surprising;
[CpRe(NO)(PPh3)(h2-SꢀCH2)][PF6] shows a coupling
between the methylene protons of only 0.9 Hz [62]. The
proton coupled 13C-NMR spectrum of the thio-
formaldehyde complex 9 shows the methylene carbon as
a triplet at 60.3 ppm (1JCH=166 Hz). The magnitude of
1JCH indicates that p character at the methylene carbon
is used for the strained ring bonds, leaving more s
character for the CꢁH bonds. The lack of geminal
coupling between the protons is also indicative of uti-
lization of carbon p character in the cyclopropane-like
ring structure of a p-bound thioformaldehyde.
3
3
is seen at 3.64 ppm (2JHH=14, JHH=12, JHH=4 Hz)
and shown in Fig. 5. The other protons appear at 2.10
(ddd), 1.71 (ddd), and 0.90 (m) ppm.
(6)
2.4. Reaction with cyclohexene sulfide
Thioformaldehyde complexes are rare [29,39,62–65].
Reaction of carbene 2b with cyclohexene sulfide (Eq.
(7)) gives the thioformaldehyde complex, [Tp%(CO)-
(PhCCMe)W(h2-SꢀCH2)][PF6] (9), and is accompanied
by only a slight shift of the CO frequency from the
cationic carbene value of 2078 to 2057 cm−1 in the IR
spectrum of the product. This frequency is comparable
to that found for the p-bound acetaldehyde complex,
(7)
3. Summary
Utilization of the BAr´4− counterion produced a
stable, crystalline sample of the cationic carbene com-
plex 2a. The structure of the prototype methylene tung-
sten carbene was determined. The electrophilic nature of
carbene 2b has been shown in reactions with phospho-
rus and nitrogen based neutral nucleophiles as well as
[Tp(CO)(PhCCMe)W(OꢀCHMe)][BAr%], at 2042 cm−1
4
[66]. It is significant to note that only s bound aldehyde
and ketone adducts have been reported previously for
alkyne complexes with the bulky Tp% in the coordination
sphere; complexes of the smaller parent Tp (hydrido-
Fig. 5. 1H-NMR signal at 3.64 ppm for one diastereotopic hydrogen in adduct 8.

526
A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
nitrogen and carbon based anionic nucleophiles. The
methylene group buffers the shifts in the metal carbonyl
frequencies to a small range of about 30 wavenumbers
as a function of the added nucleophile. Crystal struc-
tures of the phthalimide (5) and diethyl malonate (6)
derivatives may reflect attack by nucleophiles along a
path parallel to the carbonyl axis which avoids ap-
proach from between the bulky Tp% methyl groups. The
utility of the Tp% methyl groups as reporter ligands for
NOESY-NMR was shown in the determination of the
stereochemistry of the t-butyl acetoacetate adduct (7).
Neutral sulfur atom transfer from cyclohexene sulfide
to the methylene carbene forms the h2-thioformalde-
hyde complex (9).
brown solid. Recrystallization was performed at
−40°C with CH2Cl2–hexanes (90% yield). IR (neat
solid): wCO=2078 cm−1.1H-NMR (CD2Cl2, l): 12.24
(d, 1H, 2JHH=12 Hz, [W]=CHH), 11.96 (d, 1H,
2
2JHH=12, JWH=7 Hz due to 183W (14% abundance,
I=12), [W]ꢀCHH), 7.44, 7.33, 6.80 (each a m, 5H,
phenyl Hs), 6.21, 6.00, 5.74 (each a s, 3H, 1:1:1, Tp%
CH), 4.08 (s, 3H, PhCCCH3), 2.75, 2.60, 2.48, 2.45,
1.29, 1.20 (each a s, 18H, 3:3:3:3:3:3, Tp% CH3). 13C-
NMR (CD2Cl2, l): 307.3 (t, 1JCH=137, 1JWC=109
Hz, [W]ꢀCH2), 213.6, 211.8 (PhCCCH3), 205.1 (CO),
154.9, 154.1, 151.4, 148.9, 148.0, 147.5 (Tp% CCH3),
134.1, 133.1, 131.0, 129.8 (phenyl Cs), 110.4, 109.4,
108.7 (Tp% CH), 17.5, 17.0, 14.9, 14.2, 13.2, 13.0, 12.6
(Tp% CCH3 and alkyne CH3).
4. Experimental
4.4. [Tp%(CO)(PhCCMe)WꢁCH2ꢁPPh3][PF6] (3)
4.1. General considerations
A solution of methyl complex 1 (0.19 mmol) in
methylene chloride was cooled to −70°C and added to
[Ph3C][PF6] (0.19 mmol). The solution was stirred at
−70°C for 30 min. Excess triphenylphosphine (0.22
mmol) in methylene chloride was cannulated to the
carbene. The solution was stirred and warmed to r.t.
and solvent was removed under reduced pressure leav-
ing a blue solid. The crude product was purified by
column chromatography on alumina with 2:1 ether–
hexanes. Recrystallization was performed at −40°C
Reactions (2–9) were carried out under a purified
nitrogen atmosphere using standard Schlenk tech-
niques. Solvents were purified as follows: hexanes, di-
ethyl ether (Et2O), methylene chloride, and pentane
were degassed and passed through activated alumina
[69]; tetrahydrofuran (THF) was distilled from Na–
benzophenone. Methylene-d2 chloride was degassed and
,
stored over 4 A molecular sieves. Tp%(CO)(PhCCMe)-
WMe [67], [Tp%(CO)(PhCCMe)WꢀCH2][PF6] [46], and
with CH2Cl2–Et2O (15% yield). IR (neat solid): wCO
=
[Ph3C][BAr%] [50] were synthesized according to the
1895 cm−1 1H-NMR (CD2Cl2, l): 7.32−7.85 (m,
.
4
literature.
PPh3 Hs), 7.02, 6.85, 6.66 (each a m, phenyl Hs), 6.03,
5.89, 5.64 (each a s, 3H, 1:1:1, Tp% CH), 2.55 (t, 1H,
2JWH=2JPH=14, 2JWH=10 Hz, [W]ꢁCHHꢁPPh3),
1.38 (dd, 1H, 2JHH=14 Hz, 2JPH=22 Hz,
[W]ꢁCHHꢁPPh3), 2.88, 2.62, 2.44, 2.40, 1.99, 1.54, 1.20
(each a s, 21H, 3:3:3:3:3:3:3, Tp% CH3 and alkyne CH3).
13C-NMR (CD2Cl2, l): 237.4 (1JWC=142 Hz, CO),
216.5, 214.5 (PhCCCH3) 153.1, 152.3, 150.3, 146.7,
145.8, 145.7 (Tp% CCH3), 136.7, 134.3, 134.0, 133.9,
130.3, 130.2, 129.2, 125.0, 124.2 (phenyl Hs), 109.4,
1H-NMR and 13C-NMR spectra were recorded on a
Bruker AC 200, a Bruker AC 250, a Bruker AMX 300,
or a Bruker DRX 400 spectrometer. Infrared spectra
for solutions were recorded on a Mattson Polaris FT-
IR and solid state infrared spectra were recorded on an
ASI ReactIR 1000 FT-IR. Elemental analyses were
performed by Atlantic Microlab, Norcross, GA.
4.2. Representati6e [BAr%]−
4
1
108.7, 107.7 (Tp% CH), 22.5 (q, JCH=130 Hz, alkyne
1H-NMR and 13C-NMR data for the [BAr%]− coun-
terion are reported separately for simplicity. H-NMR
CH3), 14.9 (1JPC=31 Hz, [W]ꢁCH2PPh3), 15.9, 15.5,
15.4, 13.1, 13.0, 12.8 (Tp% CCH3). Anal. Calc. for
C43H49N6OBF6P2W: C, 49.93; H, 4.58; N, 8.12. Found:
C, 49.99; H, 4.54; N, 7.72%.
4
1
(CD2Cl2, l): 7.72 (br, 8H, o-Ar%), 7.55 (br, 4H, p-Ar%).
13C{H}-NMR (CD2Cl2, l): 162.1 (q, 1JBC=50 Hz,
2
ipso), 135.2 (o-C), 129.3 (q, JCF=30 Hz, m-C), 125.0
1
(q, JCF=273 Hz, CF3), 117.8 (m, p-C).
4.5. [Tp%(CO)(PhCCMe)WꢁCH2ꢁNC5H5][PF6] (4)
4.3. [Tp%(CO)(PhCCMe)WꢀCH2][BAr%] (2a)
A solution of methyl complex 1 (64 mg, 0.1 mmol) in
methylene chloride (8 ml) was cooled to −70°C and
added to a solution of [Ph3C][PF6] (39 mg, 0.1 mmol) in
methylene chloride (7 ml). The solution was stirred at
−70°C for 30 min. Excess pyridine (14.4 ml, 0.2 mmol)
was added by syringe. The solution was warmed to r.t.
and solvent was removed under reduced pressure. Re-
crystallization at ambient temperature with CH2Cl2–
4
A solution of methyl complex 1 (38 mg, 0.06 mmol)
in methylene chloride (10 ml) was cooled to −70°C
and added to [Ph3C][BAr%] (66 mg, 0.06 mmol). The
4
resulting brown solution was stirred for 30 min at
−70°C and then warmed to room temperature r.t.
Solvent was removed under reduced pressure leaving a

A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
527
Et2O yielded a green solid (81% yield). IR (neat solid):
wCO=1881cm−1 1H-NMR (CD2Cl2, l): 8.24, 7.86
4.7. Tp%(CO)(PhCCMe)WꢁCH2ꢁCH(COOEt)2 (6)
.
(each a m, pyridine Hs), 7.27, 6.69 (each a m, phenyl
Hs), 5.97, 5.95, 5.69 (each a s, 3H, 1:1:1, Tp% CH), 4.47
A solution of methyl complex 1 (128 mg, 0.2 mmol)
in methylene chloride was cooled to −70°C and added
to a solution of [Ph3C][PF6] (78 mg, 0.2 mmol) in
methylene chloride. The solution was stirred at −70°C
while the malonate was deprotonated. Malonate (45.6
ml, 0.3 mmol) was dissolved in a small amount of THF
and cooled to −70°C. Then a hexane solution of
n-BuLi (0.3 mmol) was added by syringe. The solution
was stirred for 20 min at −70°C and then added to the
tungsten carbene complex. The solution was then stirred
for 30 min and then warmed to r.t. and the solvent was
removed under reduced pressure. The crude product was
purified by column chromatography on alumina using
CH2Cl2. Purple crystals suitable for X-ray crystallo-
graphic investigation were obtained by recrystallization
at −40°C with CH2Cl2–hexanes (43% yield). IR (neat
2
2
(d, 1H, JHH=14, JWH=11 Hz, [W]ꢁCHHꢁNC5H5),
4.06 (d, 1H, Hz,
2JHH=14, 2JWH=7
[W]ꢁCHHꢁNC5H5), 3.33, 2.61, 2.45, 2.42, 2.29, 1.59,
1.30 (each a s, 21H, 3:3:3:3:3:3:3, Tp% CH3 and alkyne
CH3). 13C-NMR (CD2Cl2, l): 237.0 (1JWC=145 Hz,
CO), 212.9, 207.4 (PhCCCH3) 153.3, 152.9, 150.1,
146.9, 146.1, 145.3 (Tp% CCH3), 143.2, 141.7, 136.9,
129.7, 129.0, 127.8 (phenyl and pyridine Cs), 109.3,
1
1
109.0, 107.3 (Tp% CH), 75.6 (t, JCH=134 Hz, JWC
=
94 Hz, [W]ꢁCH2ꢁNC5H5), 21.7 (q, 1JCH=129 Hz,
alkyne CH3), 16.0, 15.8, 15.5, 13.1, 12.9, 12.8 (Tp%
CCH3). Anal. Calc. for C31H37N7BF6OPW: C, 43.13;
H, 4.32; N, 11.36. Found: C, 42.94; H, 4.24; N, 11.12%.
1
4.6. Tp%(CO)(PhCCMe)WꢁCH2-phthalimide (5)
solid): wCO=1866, 1725 cm−1. H-NMR (CD2Cl2, l):
7.21, 6.66 (each a m, phenyl Hs), 5.92, 5.89, 5.63 (each
a s, 3H, 1:1:1, Tp% CH), 4.15 (2H, ABX3 spin system,
A solution of methyl complex 1 (256 mg, 0.4 mmol)
in methylene chloride was cooled to −70°C and added
to a solution of [Ph3C][PF6] (155 mg, 0.4 mmol) in
methylene chloride. The solution was stirred at −70°C
while a solution of the deprotonated phthalimide was
prepared. Phthalimide (70.6 mg, 0.48 mmol) was dis-
solved in a minimum amount of THF and cooled to
−70°C. Then a hexane solution of n-BuLi (0.48 mmol)
was added by syringe. The solution was stirred for 20
min at −70°C and then added to the tungsten carbene
complex. The solution was then stirred for 30 min, then
warmed to r.t. and the solvent was removed under
reduced pressure. The crude product was purified by
column chromatography on alumina using CH2Cl2–
hexanes. Recrystallization at −40°C with CH2Cl2–pen-
tane yielded purple needles (40% yield). Crystals for
X-ray crystallographic investigation were obtained by
making a saturated solution of the solid in acetone and
cooling it to −40°C. IR (neat solid): wCO=1883, 1692
3
2JHH=17, JHH=7 Hz, one malonate CH2), 3.96 (q,
3
2H, JHH=7 Hz, one malonate CH2), 3.76 (dd, 1H,
3
3JHH=6.3, JHH=8.5 Hz, [W]ꢁCHꢁCH), 1.84 (dd, 1H,
2JHH=14.4, 3JHH=8.5 Hz [W]ꢁCHH), 2.88, 2.55,
2.41,2.34, 1.71, 1.34 (each a s, 21H, 3:3:3:3:3:3:3, Tp%
CH3 and alkyne CH3), 1.25, 1.14 (each a t, 6H, 3JHH=7
Hz, malonate CH3s), 0.95 (dd, 1H, 2JHH=14.4 Hz,
3JHH=6.3 [W]ꢁCHH). 13C-NMR (CD2Cl2, l): 243.4
(CO), 213.0, 209.1 (PhCCCH3) 173.9, 172.2 (malonate
COO) 153.7, 153.6, 149.7, 145.1, 144.8, 144.4 (Tp%
CCH3), 138.7, 128.5, 128.4, 128.1 (phenyl Cs), 108.5,
108.1, 106.7 (Tp% CH), 61.0, 60.7 (malonate CH2), 60.5
1
1
(d, JCH=134 Hz, [W]ꢁCH2ꢁCH) 39.8 (t, JCH=122,
1JWC=96 Hz, [W]ꢁCH2ꢁmalonate), 21.4 (alkyne CH3),
14.2, 14.1 (malonate CH3), 16.2, 15.8, 15.4, 13.0, 12.9,
12.7 (Tp% CCH3). Anal. Calc. for C33H43N6BO5W: C,
49.64; H, 5.43; N, 10.53. Found: C, 49.62; H, 5.53; N,
10.48%.
cm−1 1H-NMR (CD2Cl2, l): 7.73, 7.64 (each a m,
.
phthalimide Hs), 7.24, 6.72 (each a m, phenyl Hs), 5.90,
5.62 (each a s, 3H, 2:1, Tp% CH), 3.47 (d, 1H, 2JHH=14,
2JWH=6 Hz, [W]ꢁCHH-phthalimide), 3.07 (d, 1H,
2JHH=14, 2JWH=13 Hz, [W]ꢁCHH-phthalimide), 3.18,
2.86, 2.58, 2.42, 2.37, 1.81, 1.31 (each a s, 21H,
3:3:3:3:3:3:3, Tp% CH3 and alkyne CH3). 13C-NMR
(CD2Cl2, l): 239.9 (1JWC=147 Hz, CO), 211.0, 207.6
(PhCCCH3), 168.9 (phthalimide CO), 154.6, 154.0,
149.6, 145.6, 144.9, 144.5 (Tp% CCH3), 138.6, 133.3,
128.7, 128.5, 128.1, 122.2 (phenyl and phthalimide Cs),
4.8. Tp%(CO)(PhCCMe)WꢁCH2ꢁCH(COCH3)-
(COOt-Bu) (7)
A solution of methyl complex 1 (128 mg, 0.2 mmol)
in methylene chloride was cooled to −70°C and added
to a solution of [Ph3C][PF6] (78 mg, 0.2 mmol) in
methylene chloride. The solution was stirred at −70°C
while the tert-butyl acetoacetate was deprotonated.
tert-Butyl acetoacetate (50.0 ml, 0.3 mmol) was dis-
solved in a small amount of THF and cooled to
−70°C. Then a hexane solution of n-BuLi (0.3 mmol)
was added by syringe. The solution was stirred for 20
min at −70°C and then added to the tungsten carbene
complex. The solution was then stirred for 30 min,
warmed to r.t. and the solvent was removed under
reduced pressure. The crude product was purified by
108.9, 108.0, 106.6 (Tp% CH), 50.7 (t, 1JCH=130,
1
1JWC=101 Hz, [W]ꢁCH2-phthalimide), 21.4 (q, JCH
=
130 Hz, alkyne CH3), 16.6, 15.9, 15.2, 13.2, 13.0, 12.7
(Tp% CCH3). Anal. Calc. for C34H36N7O3BW·CH2Cl2
(CH2Cl2 present by NMR): C, 48.30; H, 4.40; N, 11.27.
Found: C, 48.03; H, 4.39; N, 10.99%.

528
A.S. Jepsen et al. / Journal of Organometallic Chemistry 617–618 (2001) 520–529
column chromatography on alumina using CH2Cl2
(42% yield). Crystals were obtained by slow evapora-
tion of a solution of the t-butyl acetoacetate adduct 7
in acetone. IR (neat solid): wCO=1877, 1715, 1696
[W]ꢁCH2), 21.2 (alkyne CH3), 16.4, 15.9, 15.3, 12.9,
12.7 (1:1:1:1:2:1, Tp% CCH3). Anal. Calc. for
C34H39N6BO2W: C, 53.85; H, 5.18; N, 11.08. Found: C,
53.57; H, 5.32; N, 11.04%.
cm−1 1H-NMR (CD2Cl2, l): 7.22, 6.66 (each a m,
.
4.10. [Tp%(CO)(PhCCMe)W(p2ꢁSꢀCH2)][PF6] (9)
phenyl Hs), 5.93, 5.91, 5.64 (each a s, 3H, 1:1:1, Tp%
3
CH), 3.50 (t, 1H, JHH=7 Hz, [W]ꢁCH2ꢁCH), 3.31 (s,
A solution of methyl complex 1 (133 mg, 0.21 mmol)
in methylene chloride (10 ml) was cooled to −70°C
and added to [Ph3C][PF6] (80 mg, 0.21 mmol). The
solution was stirred for 15 min. Then cyclohexene
sulfide (50 ml, 0.4 mmol) was added by syringe and the
yellow–brown solution was stirred for 30 min. Solvent
was removed in vacuo and the brown solid was washed
with hexanes and ether to give a mustard yellow pow-
3H, alkyne CH3), 2.95, 2.57, 2.42, 2.36, 1.67, 1.35 (each
a s, 18H, 3:3:3:3:3:3, Tp% CH3), 1.91 (s, 3H, COCH3),
2
3
1.68 (dd, 1H, JHH=14, JHH=7 Hz, [W]ꢁCHH), 1.49
2
3
(s, 9H, t-Bu Hs) 1.07 (dd, 1H, JHH=14, JHH=7 Hz,
[W]ꢁCHH). 13C-NMR (CD2Cl2, l): 243.0 (1JWC=145
Hz, CO), 212.5, 209.1 (PhCCCH3), 206.2 (COCH3),
173.4 (COOt-Bu), 153.8, 153.4, 149.7, 145.1, 144.8,
144.4 (Tp% CCH3), 138.7, 128.6, 128.4, 128.1 (phenyl
Cs), 108.5, 108.2, 106.8 (Tp% CH), 80.8 (t-Bu C(CH3)3),
1
der (81% yield). IR (KBr): wCO=2057 cm−1. H-NMR
1
1
(CD2Cl2, l): 7.37 (t, 1H, phenyl p-H), 7.27 (t, 2H,
phenyl m-Hs), 6.44 (d, 2H, phenyl o-Hs), 6.09 (s, 1H,
SꢀCHH), 6.12, 5.99, 5.83 (each a s, 1:1:1, Tp% CH), 4.83
(s, 1H, SꢀCHH), 3.60 (s, 3H, alkyne CH3), 2.67, 2.47,
2.41, 1.58, 1.56 (each a s, 3:6:3:3:3, Tp% CH3). 13C-NMR
(CD2Cl2, l): 205.5 (CO), 192.3, 179.74 (PhCCMe),
156.65, 155.1, 151.9, 147.8, 147.1, 146.9 (Tp% CCH3),
134.0, 131.7, 129.6, 129.4, 128.6 (phenyl Cs), 111.2,
70.5 (d, JCH=136 Hz, [W]ꢁCH2ꢁCH), 40.6 (t, JCH
=
1
121, JWC=94 Hz, [W]ꢁCH2ꢁ), 28.2 (t-Bu CH3), 26.6,
21.6, 16.4, 15.8, 15.6, 13.1, 13.0, 12.8 (Tp% CCH3,
alkyne CH3, and COCH3). Anal. Calc. for
C34H46N6O4BW: C, 51.25; H, 5.69; N, 10.55. Found: C,
51.17; H, 5.84; N, 10.49%.
4.9. Tp%(CO)(PhCCMe)WꢁCH2ꢁCH2C(O)Ph (8)
1
111.0, 110.0 (Tp% CH), 60.3 (t, SꢀCH2, JCH=166 Hz),
20.5 (alkyne CH3), 17.2, 16.2, 15.6, 13.2, 13.1, 13.0 (Tp%
CH3).
A solution of methyl complex 1 (161.0 mg, 0.25
mmol) in methylene chloride (10 ml) was cooled to
−70°C and added to a solution of [Ph3C][PF6] (97 mg,
0.25 mmol) in methylene chloride (10 ml). The solution
was stirred at −70°C while acetophenone was deproto-
nated in the following way: Acetophenone (43.8 ml,
0.375 mmol) was dissolved in a small amount of THF
(3 ml) and cooled to −70°C. Then a hexane solution of
n-BuLi (0.375 mmol) was added by syringe. The solu-
tion was stirred for 20 min at −70°C and then added
to the tungsten carbene complex. The solution was
stirred for 30 min, warmed to r.t. and the solvent was
removed under reduced pressure. The crude product
was collected as a blue band by column chromatogra-
phy on alumina using CH2Cl2–hexanes (27% yield). IR
5. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 148457 for complex 6, 148458
for complex 5, and 148459 for complex 2a. Copies of
this information may be obtained free of charge from:
The Director, CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (Fax: +44-1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
(neat solid): wCO=1847, 1671 cm−1
.
1H-NMR
(CD2Cl2, l): 7.82, 7.42 (each a m, 5 H, 2:3, acetophe-
none phenyl Hs), 7.22, 6.70 (each a m, 5H, 3:2, phenyl
Hs), 5.89, 5.84, 5.65 (each a s, 3H, 1:1:1, Tp% CH), 3.64
(ddd, 1H, 2JHH=14, 3JHH=12, 3JHH=4 Hz,
Acknowledgements
We gratefully acknowledge the National Science
Foundation (Grant No. CHE-9727500) for support of
this research. Aase Jepsen would also like to thank the
Faculty of Natural Science at Aarhus University for
financial support.
2
3
[W]ꢁCH2ꢁCHH), 2.10 (ddd, 1H, JHH=14, JHH=5,
3JHH=13 Hz, [W]ꢁCH2ꢁCHH), 3.36, 2.81, 2.53, 2.42,
2.32, 1.59, 1.38 (each a s, 21H, 3:3:3:3:3:3:3, Tp% CH3,
2
alkyne CH3 and COCH3), 1.71 (ddd, 1H, JHH=14,
3
3JHH=5 Hz, JHH=12, [W]ꢁCHHꢁCH2), 0.90 (m, 1H,
[W]ꢁCHHꢁCH2). 13C-NMR (CD2Cl2, l): 245.0
(1JWC=145 Hz, CO), 210.2, 207.3 (PhCCCH3), 205.0
(COPh), 153.2, 149.5, 145.0, 144.9, 144.3 (Tp% CCH3),
138.5, 137.8, 132.2, 128.7, 128.6, 128.5, 128.1 (phenyl
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