Strikingly different reactivity patterns of fischer alkoxycarbene and thiocarbene complexes in experimental and theoretical studies

Article abstract of DOI:10.1021/om700391t

Striking differences in the reactions of alkoxycarbene and thiocarbene complexes of chromium and tungsten are observed. Thus, (β-imino) ethoxycarbene complexes 10a-e, generated in situ from [(OC)₅W= C(OEt)CH₂R] (7a-c; R = n-Pr, Me, c-C₇H₇) and imidoyl chlorides R¹ClC=NCHR²R³ (9a-f; R ¹ = t-Bu, Ph, 2-furyl; R² = H, Me; R3 = Me, Et, Ph), undergo a metalla(di-π-methane) rearrangement to (N-enamino)ethoxycarbene complexes 12a-e, while the corresponding (β--imino)thiocarbene complexes 11a-1, derived from [(OC)₅M=C(SEt)CH₂R] (8a-e; M = W, Cr; R = n-Pr, Me, c-C₇H₇, c-C₆H₇Fe-(CO) ₃) and imidoyl chlorides under similar conditions, form pyrroles 16a-h and 17k,l by α-cyclization. On the basis of the calculated DFT/BP86 potential energy surfaces of the particular reaction channels it is shown that (β-imino)alkoxycarbene compounds 10 prefer a metalla(di-α-methane) rearrangement due to the kinetic stability of the (N-enamino)ethoxycarbene products, while formation of pyrroles is not favored due to the presence of high energetic stationary structures in the α-cyclization pathway. For (β-imino)thiocarbene compounds 11, on the other hand, rearranged products are kinetically unstable, and α-cyclization reactions are strongly favored on thermodynamic grounds.

Full text of DOI:10.1021/om700391t

Organometallics 2007, 26, 4983-4996
4983
Strikingly Different Reactivity Patterns of Fischer
Alkoxycarbene and Thiocarbene Complexes in
Experimental and Theoretical Studies†
Betu¨l Karatas, Isabella Hyla-Kryspin,‡ and Rudolf Aumann*
Organisch-Chemisches Institut der UniVersita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany
ReceiVed April 23, 2007
Striking differences in the reactions of alkoxycarbene and thiocarbene complexes of chromium and
tungsten are observed. Thus, (â-imino)ethoxycarbene complexes 10a-e, generated in situ from [(OC)5Wd
C(OEt)CH2R] (7a-c; R ) n-Pr, Me, c-C7H7) and imidoyl chlorides R1ClCdNCHR2R3 (9a-f; R1 )
t-Bu, Ph, 2-furyl; R2 ) H, Me; R3 ) Me, Et, Ph), undergo a metalla(di-π-methane) rearrangement to
(N-enamino)ethoxycarbene complexes 12a-e, while the corresponding (â-imino)thiocarbene complexes
11a-l, derived from [(OC)5MdC(SEt)CH2R] (8a-e; M ) W, Cr; R ) n-Pr, Me, c-C7H7, c-C6H7Fe-
(CO)3) and imidoyl chlorides under similar conditions, form pyrroles 16a-h and 17k,l by R-cyclization.
On the basis of the calculated DFT/BP86 potential energy surfaces of the particular reaction channels it
is shown that (â-imino)alkoxycarbene compounds 10 prefer a metalla(di-π-methane) rearrangement due
to the kinetic stability of the (N-enamino)ethoxycarbene products, while formation of pyrroles is not
favored due to the presence of high energetic stationary structures in the R-cyclization pathway. For
(â-imino)thiocarbene compounds 11, on the other hand, rearranged products are kinetically unstable,
and R-cyclization reactions are strongly favored on thermodynamic grounds.
efficient way to (aryl)thiocarbene complexes involves acetylation
and thiolysis of the corresponding carbonylmetalates, e.g.,
[(OC)5M(COC6H5)][NMe4] (M ) Cr, W, Mn).6a,7 Thiolysis of
(aryl)aminocarbene complexes is unfavorable on thermodynamic
grounds, but is achieved after N-acylation.5c
Introduction
Fischer alkoxycarbene and aminocarbene complexes1 are
widely applied in organic synthesis,2 whereas the isostructural
thiocarbene complexes have found little attention in this respect.3
(Alkyl)thiocarbene complexes [(OC)5MdC(SR)alkyl] (M )
Cr, W; R ) Me, Et, Ph) are readily available by thiolysis of
the corresponding (alkyl)alkoxycarbene complexes.4,5a,b,6b An
Reactions of (alkyl)thiocarbene complexes studied so far,
include addition of phosphines,8 isocyanides,6b,c alkynes,6d,7 and
hydrogen bromide,9 condensation with aromatic aldehydes,6b
and insertion into carbon-hydrogen and metal-carbene bonds.10
Reactions of dithiocarbene complexes11 and η2-thiocarbene
complexes12,13 with amines, alkyl phosphines, and azides have
also been reported, as well as the addition of hydrides and
thiolates,14 alkyl- and arylsulfonium salts,13 trifluoroacetic acid,15
and thiocyanate salts.16
* Corresponding author. E-mail: aumannr@uni-muenster.de.
† Organic Synthesis via Transition Metal Complexes, Part 122. For Part
121 see ref 17.
‡ Theoretical calculations.
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10.1021/om700391t CCC: $37.00 © 2007 American Chemical Society
Publication on Web 08/24/2007

4984 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
Scheme 2. Formation of (N-Enamino)ethoxycarbene
Complexes 12a-e by a Metalla(di-π-methane)
Rearrangement of (â-Imino)ethoxycarbene Complexes 10,
and 2H-Pyrrole Complexes 13a-l by r-Cyclization of
(â-Imino)thiocarbene Complexes 11
Scheme 1. Competition of Condensation and Insertion on
Reactions of (Methyl)ethoxycarbene Complexes 1a,b with
Secondary Amides 2 and Tertiary Amides 4, Respectively, in
18
the Presence of POCl3/NEt3
unraveled for isostructural alkoxycarbene complexes. Funda-
mental differences in reactivities of thiocarbene and alkoxy-
carbene complexes were found only recently in condensation
reactions of (alkyl)ethoxycarbene and (alkyl)thiocarbene com-
plexes with acid amides.17
Reactions of (alkyl)ethoxycarbene complexes with imidoyl
chlorides, generated in situ from acid amides and POCl3/NEt3,
were shown to form condensation,18a,b insertion,18c and rear-
rangement products,18b depending on the alkyl substituent of
the (alkyl)ethoxycarbene complexes and the type of acid amide
involved. Thus, for example â-(NH-amino)alkenylcarbene com-
plexes [(OC)5MdC(OEt)CHdC(NHMe)R1], (Z)-3, were ob-
tained as the only products from condensation of (methyl)-
ethoxycarbene complexes [(OC)5MdC(OEt)CH3] (1a,b; M )
Cr, W) with secondary amides R1C(dO)NHMe (2; R1 ) alkyl,
aryl) in the presence of POCl3/NEt3 (Scheme 1),18a,b whereas
only small amounts of condensation products [(OC)5MdC(OEt)-
CHdC(CH2R1)NMe2], (E)-6,18c but mainly insertion products
[(OC)5MdC(NMe2)R1CdC(OEt)CH3], (E/Z)-5, were generated
on condensation of (methyl)ethoxycarbene complexes with
tertiary amides R1CH2C(dO)NMe2 (4; R1 ) alkyl, aryl). On
the other hand, reactions of (alkyl)ethoxycarbene complexes
other than (methyl)ethoxycarbene compounds 1, e.g., the (n-
butyl)ethoxycarbene complex [(OC)5WdC(OEt)n-Bu] (7a), and
secondary amides 2 in the presence of POCl3/NEt3 gave (N-
enamino)ethoxycarbene complexes 12 by a metalla(di-π-
methane) rearrangement (Scheme 2, path 1).18b,19
aIsolated chemical yields in [%] of compounds 12. bsyn/anti ratio of
1
c
isomers 12 according to H NMR measurements. For the structures
of compounds 15-17 see Scheme 3. dIsolated chemical yields of
pyrroles 16 obtained by spontaneous transformation of pyrrole com-
plexes 13. Note that compounds 16c, 16i, 16e, and 16j are identical,
although they were generated from different starting compounds. e1H-
pyrroles 16 were not obtained in this case, but 2H-pyrroles 13k,l and
17k,l (Scheme 3) were identified by NMR measurements.
(12) (a) Kim, H. P.; Kim, S.; Jacobson, R. A.; Angelici, R. J.
Organometallics 1986, 5, 2481-2488. (b) Kim, H. P.; Angelici, R. J.
Organometallics 1986, 5, 2489-2496. (c) Ullrich, N.; Keller, H.; Stegmair,
C.; Kreissl, F. R. J. Organomet. Chem. 1989, 378, C19-C22. (d) Schu¨tt,
W.; Herdtweck, E.; Kreissl, F. R. J. Organomet. Chem. 1993, 456, C15-
C17. (e) Ogric, C.; Schu¨tt, W.; Lehotkay, T.; Herdtweck, E.; Kreissl, F. R.
Z. Naturforsch., B: Chem. Sci. 1995, 50, 1839-1844. (f) Ogric, C.;
Lehotkay, T.; Wurst, K.; Jaitner, P.; Kreissl, F. R. J. Organomet. Chem.
1997, 541, 71-75. (g) Ullrich, N.; Stegmair, C.; Keller, H.; Herdtweck,
E.; Kreissl, F. R. Z. Naturforsch. B: Chem. Sci. 1990, 45, 921-925.
(13) Ostermeier, J.; Schu¨tt, W.; Stegmair, C. M.; Ullrich, N.; Kreissl, F.
R. J. Organomet. Chem. 1994, 464, 77-81.
We now report on a quite unexpected strong influence of
the heteroatoms oxygen and sulfur on the reactions of (alkyl)-
heterocarbene complexes [(OC)5MdCXCH2R] 7a-c (M ) W;
X ) OEt) and 8a-e (M ) W, Cr; X ) SEt), respectively, with
imidoyl chlorides R1ClCdNCHR2R3 9a-f, generated from
secondary amides R1C(dO)NHCHR2R3 20 (Scheme 2).
(14) (a) Doyle, R. A.; Angelici, R. J. Organometallics 1989, 8, 2207-
2214. (b) Doyle, R. A.; Angelici, R. J. J. Organomet. Chem. 1989, 375,
73-84.
(15) Kreissl, F. R.; Mu¨ller, F. X.; Wilkinson, D. L.; Mu¨ller, G. Chem.
Ber. 1989, 122, 289-290.
Results and Discussion
(16) Ogric, C.; Ostermeier, J.; Heckel, M.; Hiller, W.; Kreissl, F. R. Inorg.
Chim. Acta 1994, 222, 77-84.
Even though on first sight it might be expected that
isostructural alkoxycarbene and thiocarbene complexes would
react similarly, we found completely different reaction patterns
for these compounds under certain circumstances. For example,
(17) Nitsche, F.; Aumann, R.; Fro¨hlich, R. J. Organomet. Chem. 2007,
692, 2971-2989.
(18) (a) Aumann, R.; Hinterding, P. Chem. Ber. 1990, 123, 2047-2051.
(b) Aumann, R.; Fu, X.; Vogt, D.; Fro¨hlich, R.; Kataeva, O. Organometallics
2002, 21, 2736-2742. (c) Aumann, R.; Hinterding, P. Chem. Ber. 1990,
123, 611-620.
(19) U¨ naldi, S.; Aumann, R.; Fro¨hlich, R. Chem.-Eur. J. 2003, 9, 3300-
3309.
(20) Nerdel, F.; Weyerstahl, P.; Dahl, R. Liebigs Ann. Chem. 1968, 716,
127-134.

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4985
Scheme 3. Formation of 1H-Pyrroles 16, 2H-Pyrroles 17,
and 2H-Pyrrole Complexes 13 from (â-Imino)thiocarbene
Complexes 11 (for the numerical designation of compounds
15-17 see table of Scheme 2)
Scheme 5. Formation of 2H-Pyrrole Complex 21 and
1H-Pyrrole 22 by π-Cyclization of the
5-Aza-1-tungsta-1,3,5-hexatriene 2021b
2, paths 1 and 2) are explained on the basis of multistep
processes following the intial formation of (â-imino)heterocar-
bene complexes 10a-e (X ) O) and 11a-l (X ) S). On the
basis of calculations presented below, it appears that an
associative reaction step involving the addition of the â-imino
nitrogen atom to the carbene carbon atom is favored for the
(â-imino)ethoxycarbene complexes 10a-e over that of the
corresponding (â-imino)thiocarbene complexes 11a-l, whereas
a dissociative process leading to vinylidenes 15 is energetically
favored in the case of (â-imino)thiocarbene complexes 11a-l.
Formation of vinylidenes 15 by elimination of thiol from a (â-
imino)thiocarbene complex was shown to be energetically more
favorable than the elimination of an alcohol from a (â-imino)-
alkoxycarbene complex. Transfer of an R-hydrogen atom from
the dN-CH group to the vinylidene unit of compounds 15 gives
5-aza-1-metalla-1,3,5-hexatrienes 19, which subsequently un-
dergo a π-cylization to pyrrole complexes 13 (Scheme 4). The
regiochemistry of the hydride transfer has been clarified by a
labeling experiment, in which the 1H-pyrrole (4D)-16e was
generated from the (n-butyl)thiocarbene complex [(OC)5Wd
C(SEt)n-Bu] (8a) and the deuterated imidoyl chloride PhClCd
NCD2Ph (D2-9e) (Scheme 4).
The assumption that the 5-aza-1-metallatriene 19 would
undergo a π-cyclization is in agreement with the reported
stepwise transformation of the 5-aza-1-tungsta-1,3,5-hexatriene
[(OC)5WdC(NEt)2-CMedC(Ph)NdCHPh] (20) to the 2H-
pyrrole complex 21 and finally the 1H-pyrrole 22 (Scheme 5).21b
DFT Calculations. In order to gain deeper insight into the
reaction mechanisms depicted in Scheme 2 as well as to obtain
an answer on the question of why the alkoxycarbene complexes
7 and the thiocarbene complexes 8 prefer different reaction
paths, the metalla (di-π-methane) rearrangements, abbreviated
below as MDPM rearrangement, and the R-cyclization reactions
were investigated for both types of complexes with the help of
DFT calculations. The calculations were carried out on model
tungsten complexes, in which the ethyl group bound to the O/S
atoms in the experimental molecules as well as the substituents
R, R1, R2, and R3 were replaced by methyl groups. We started
our investigations by searching the stationary structures of the
postulated reactants 10 (X ) O) and 11 (X ) S) (see Scheme
(alkyl)ethoxycarbene complexes 7a-c afforded (N-enamino)-
ethoxycarbene complexes 12a-e on reaction with imidoyl
chlorides 9 and triethylamine in 61-82% isolated yields,
whereas the isostructural (alkyl)thiocarbene complexes 8a-e
did not give (N-enamino)thiocarbene complexes under these
conditions, but formed 2H-pyrrole complexes 13a-l instead
(Scheme 2).
Common to both reaction paths (Scheme 2, paths 1 and 2) is
the initial formation of (â-imino)heterocarbene complexes
10a-e (X ) O) and 11a-l (X ) S), respectively, which play
a key role, since their reactions are strongly directed by the
heteroatom. Thus (â-imino)ethoxycarbene complexes were
found to undergo a spontaneous rearrangement to (N-enamino)-
ethoxycarbene complexes 12a-e,19 whereas (â-imino)thiocar-
bene complexes 11a-l derived from (alkyl)thiocarbene com-
plexes 8a-e underwent an R-cyclization to pyrroles 16a-h,
via initial formation of thermolabile 2H-pyrrole complexes
13a-h and 2H-pyrroles 17a-h (Scheme 3).21 Other than the
2H-pyrrole complexes 13a-h and 2H-pyrroles 17a-h, the 2H-
pyrrole complexes 13k,l are reasonably stable due to the absence
of an R-proton and, therefore, could be identified by NMR
measurements in product mixtures with its demetalation com-
pounds 17k,l. The thiols, which are eliminated in this reaction,
are captured by imidoyl chlorides 9a-f to give thioesters R1-
(EtS)CdNCHR2R3 14.
A variety of 1H- and 2H-pyrroles were thus obtained from
(alkyl)thiocarbene complexes 8a-e and imidoyl chlorides 9a-f
in 51-82% isolated yields (Scheme 2).
The different reaction paths observed for ethoxycarbene
compounds 7a-c and thiocarbene compounds 8a-e (Scheme
Scheme 4. Deuterium Labeling Experiment Leading to Selectively Labeled Pyrrole (4-D)-16e

4986 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
Figure 1. Optimized structures and relative electronic energies of the methoxy (10f-10i) and (methyl)thio (11m-11p) reactants.
2). Both types of reactants are characterized by large structural
flexibility of the coordinated carbene ligand, and several
stationary points were detected on their potential energy surfaces
(Figure 1). From Figure 1 it is evident that the â-imino group
of 10f, 10g, 11m, and 11n should be capable of approaching
the carbene carbon atom easily and initiate the MDPM rear-
rangement, while 10h, 10i, 11o, and 11p may be regarded as
starting structures for the R-cyclization reactions. The calculated
reaction channels of the MDPM rearrangements and the
R-cyclization reactions are discussed in the next sections in more
detail.
MDPM Rearrangement of the Methoxy (10f, 10g) and the
(Methyl)thio (11m, 11n) Carbene Complexes. The MDPM
rearrangements proceed through four-membered cyclic structures
of the carbene ligand, which independently of the basis set used
for calculations were located as transition states (TS) of the
reactions. For the sake of clarity they are labeled below as TS-
(10ff12f), TS(10gf12g), TS(11mf12m), and TS(11nf12n).
The molecular shapes of the optimized structures of transition
states and products are shown in Figure 2. The corresponding
potential energy profiles are depicted in Figures 3 and 4.
Selected BP86/TZVP-optimized parameters of the relevant
stationary structures as well as the analogous data from BP86/
LANL2DZ calculations together with the number of imaginary
frequencies are provided in the Supporting Information (Table
S1, Table S2, Figure S1, and Figure S2).
Compared to the reactants 10f/11m and 10g/11n, the struc-
tural changes in the transition states TS(10ff12f)/TS(11mf12m)
and TS(10gf12g)/TS(11nf12n) are clearly indicative of the
C1-N bond formation and breakage of the C1-C2 bond. Thus,
upon going from 10f/11m to the transition states TS(10ff12f)/
TS(11mf12m) the C1-C2 bond stretches by 0.078 Å/0.061
Å, the C2-C3-N bond angle diminishes by 21.6°/15.5°, and
the C1-N distance shortens significantly by 1.155 Å/1.048 Å.
All these changes are accompanied by elongation of the W-C1
and C1-O/S bonds by 0.204 Å/0.099 Å and 0.084 Å/0.073 Å,
respectively. Compared to the TS(10ff12f)/TS(11mf12m) the
C1-N bond formation and breakage of the C1-C2 bond are
Figure 2. Molecular shapes of the optimized structures of transition
states and products for the MDPM rearrangements of 10f/11m f
syn-12f/syn-12m and 10g/11n f anti-12g/anti-12n.
less pronounced in the TS(10gf12g)/TS(11nf12n). With
respect to the reactants 10g/11n, the C1-N bond distance of
the TS(10gf12g)/TS(11nf12n) is 0.902 Å/0.978 Å shorter and
that of the C1-C2 bond 0.059 Å/0.056 Å longer; that is, these
changes are smaller than in the case of 10f/11m f 12f/12m
reactions.
The MDPM rearrangement 10f f syn-12f is an exothermic
process with a moderate reaction barrier. The product syn-12f
is 5.7 kcal mol-1 more stable than the reactant 10f, and the
reaction barrier amounts to 14.9 kcal mol-1 (Figure 3, right side).
The analogous reaction of the (methyl)thio complex, 11m f
syn-12m, is characterized by lower exothermicity and lower
reaction barrier. The calculations predict a reaction barrier of
10.7 kcal mol-1 and an exothermicity of only 1.7 kcal mol-1
(Figure 4, right side). Thus, with respect to the reaction of the
methoxy species, 10f f syn-12f, the MDPM rearrangement of
the (methyl)thio species, 11m f syn-12m, is a thermodynami-
(21) (a) Aumann, R.; Heinen, H.; Kru¨ger, C.; Betz, P. Chem. Ber. 1990,
123, 599-604. (b) Aumann, R.; Heinen, H.; Goddard, R.; Kru¨ger, C. Chem.
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Organometallics 1997, 16, 2571-2580.

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4987
Figure 3. BP86/TZVP potential energy profiles for the MDPM rearrangement of the methoxy complexes 10f and 10g. The depicted
energy levels refer to ∆Eelec, values in parentheses are relative enthalpies at 298 K (∆∆H298), and those in square brackets are relative
Gibbs free energies at 298 K (∆∆G298).
Figure 4. BP86/TZVP potential energy profiles for the MDPM rearrangement of the (methyl)thio complexes 11m and 11n. The depicted
energy levels refer to ∆Eelec, values in parentheses are relative enthalpies at 298 K (∆∆H298), and those in square brackets are relative
Gibbs free energies at 298 K (∆∆G298).
cally less favored reaction. Furthermore, due to the low-energy
barrier of the reverse process syn-12m f 11m (12.4 kcal mol-1
compared to that of the reverse syn-12f f 10f reaction (20.6
kcal mol-1), the (methyl)thio product syn-12m is kinetically less
stable than the methoxy syn-12f one.
Adding zero-point vibrational energy (ZPVE) and thermal
corrections to the electronic energies ∆Eelec, that is, considering
the relative enthalpies ∆∆H298, does not change these conclu-
sions (Figures 3 and 4). Adding further entropy contributions,
that is, considering the relative Gibbs free energies (∆∆G298),
increases the energy barriers, diminishes the exothermicity of
the MDPM reactions, and destabilizes 10g and 11n compared
to the global minimum reactants 10f and 11m (Figures 3 and
4). The MDPM rearrangement of the (methyl)thio complex, 11m
f syn-12m, with a ∆∆G298(syn-12m) of 1.2 kcal mol-1 is now
a slightly endothermic reaction, and that of the methoxy
complex, 10f f syn-12f, with a ∆∆G298(syn-12f) of -1.8 kcal
mol-1 is still an exothermic process. However, the complexes
syn-12f and syn-12m are not the lowest energy structure among
the N-enamino products.
)
Lower energy products, that is, anti-12g and anti-12n, are
found when the MDPM rearrangement begins with the reactants

4988 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
Figure 5. Molecular shapes of the optimized stationary structures of the (methyl)thio and methoxy species for R-cyclization reactions
according to path 1.
Figure 6. Molecular shapes of the optimized stationary structures for the R-cyclization reactions according to path 2.
10g and 11n (Figures 3 and 4, left side). In terms of ∆Eelec
anti-12g and anti-12n are 2.8 and 6.5 kcal mol-1 more stable
than syn-12f and syn-12m, respectively. The energy profiles for
the formation of N-enamino products anti-12g and anti-12n from
the reactants 10g and 11n are very similar (Figure 3 and 4, left
side). The calculated reaction barriers (∆E#elec) amount to 8.1
kcal mol-1 for TS(10gf12g) and to 7.1 kcal mol-1 for TS-
(11nf12n). The exothermicity (∆Eelec) of the reaction 10g f
anti-12g (13.8 kcal mol-1) is almost the same as that of the
reaction 11n f anti-12n (12.8 kcal mol-1). These energetic
differences are too small to account for the different behavior
of the alkoxy and (alkyl)thio species. Moreover, 10g and 11n,
with ∆Eelec of 5.3 and 4.6 kcal mol-1 above 10f and 11m, are
the less stable reactants. Thus, it is very likely that both species
will not be involved in the reactions. Note that the anti-forms
should also be attainable from the syn-products by rotation of
the N-enamino part of the carbene ligand. These findings are
in accord with the experimental evidence that (i) at the beginning
of the MDPM rearrangement the formation of the alkoxy syn-
products 12a-d dominates the formation of the anti-12a-d
ones, and (ii) as time passes, the syn-isomers slowly convert
into the anti-forms.
processes the elimination of ethanethiol and the formation of
thioesters may occur either prior or after the ring closure, we
decided to explore the potential energy surfaces (PES) of the
corresponding reaction paths of these R-cyclization reactions.
In path 1 we assume that the reactions begin with the model
reactants 11o and 10h (Figure 5). The hydride migration and
ring closure yield the adducts 23o and 23h, which rearrange to
complexes 24o and 24h. The elimination of methanethiol/
methanol from 24o/24h takes place in the last step of the
reactions, and the 2H-pyrrole complex 13 is produced.
In path 2, we begin the reactions with the global minimum
reactants 11m and 10f. The elimination of methanethiol/
methanol takes place at the early stage of the reactions, giving
the vinylidene 15m (Figure 6). The hydride migration in 15m
yields the hexatriene 19m and is followed by the ring closure.
The resulting π-complex 25 rearranges then to the 2H-pyrrole
complex 13 (Figure 6).
The TS(11of23o) and TS(10hf23h) of path 1 calculated
with the TZVP basis set correspond to transition states for a
simultaneous hydrogen transfer and ring closure (Figure 5). Both
transition states are characterized by one strong imaginary mode
reflecting the ring closure process {499.7i cm-1 [TS(11of23o)],
538.9i cm-1 [TS(10hf23h)]}. All attempts to locate the
stationary points for hydrogen transfer that is followed by the
ring closure failed. The energy barrier (∆E#elec) for the reaction
step 10h f 23h of the oxo species is 6.2 kcal mol-1 higher
Formation of Pyrrole Complexes 13 from the Methoxy
(10h, 10f) and (Methyl)thio (11o, 11m) Carbene Complexes.
In this section we focus on the comparison of possible reaction
paths for the formation of pyrrole complexes 13. Since in these

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4989
Figure 7. Potential energy profiles for R-cyclization reactions of the oxo (10f, 10h) and the thio (11m, 11o) carbene complexes according
to path 1 (left) and path 2 (right). The depicted energy levels refer to relative electronic energies (∆Eelec), which are given in bold. Values
in parentheses are relative enthalpies at 298 K (∆∆H298), and those in square brackets are relative Gibbs free energies at 298 K (∆∆G298).
The stationary points of the oxo complexes are connected by the dashed lines and those of the thio species by the solid lines.
than for the analogous reaction of the thio species, 11o f 23o
(Figure 7, left side). Including entropic effects (∆∆G#298) slightly
7.7 kcal mol-1 less endothermic than that of methanol, for which
the ∆Eelec(10ff15m) amounts to 20.7 kcal mol-1. On the PES
of Gibbs free energies the elimination of methanethiol, with a
∆∆G298(11mf15m) of -2.9 kcal mol-1, is now an exothermic
reaction, while that of methanol, with a ∆∆G298(10ff15m) of
6.2 kcal mol-1, is still an endothermic process.
It is clear that, with respect to the PES of the thio species,
all subsequent reaction steps of the oxo species will be shifted
uphill by the same amount of energy, that is, 7.7 kcal mol-1 in
terms of ∆Eelec and 9.1 kcal mol-1 in terms of ∆∆G298. Thus,
at this point we can conclude that with respect to the thio
reactant 11m the R-cyclization reaction of the oxoreactant 10f
is not favored on thermodynamical grounds.
increases this value to 8.5 kcal mol-1
.
In accordance with the saturated nature of the C1 and C2
carbon atoms of the cyclic ligand, the W-C1 and W-C2
distances of the adducts 23o and 23h are long [3.406, 3.926 Å
(23o), 3.391, 3.967 Å (23h)] and the interaction energies with
the W(CO)5 fragment are very weak (below 2 kcal mol-1). Thus,
23o and 23h should easily rearrange to the intermediates 24o
and 24h. The ring closure and the complexation of the cyclic
ligand are exothermic processes (Figure 7). In terms of ∆Eelec
,
the ring closure of the thio species, 11o f 23o, is 5.2 kcal mol-1
more exothermic than that of the oxo species 10h f 23h.
Compared with 23o and 23h, the formation of the W-N bond
stabilizes 24o and 24h by a comparable amount of energy [26.7
kcal mol-1 (24o), 24.2 kcal mol-1 (24h)]. The last elementary
step, that is, the elimination of methanethiol/methanol and
formation of the pyrrole complex 13 (24o/24h f 13), procceeds
uphill on the PES of ∆Eelec (Figure 7). With respect to 24o/24h
it is slightly endothermic by approximately the same amount
of energy, that is, 3.4 kcal mol-1 for 24o f 13 and 2.2 kcal
mol-1 for 24h f 13. The elimination of methanethiol/methanol
is almost thermoneutral on the PES of ∆∆H298, but due to the
large entropic contributions it is exogenic on the PES of Gibbs
free energies (-12.0 kcal mol-1 for 24o f 13, -12.2 kcal mol-1
for 24h f 13). The entropic contributions for the elimination
processes 24o/24h f 13 are on the order of 8 kcal mol-1. As
should be expected for processes with a constant number of
particles, the entropic contributions are less significant for the
preceding reaction steps (2-5 kcal mol-1).
In the second step of path 2 a barrierless hydrogen transfer
in 15m occurs and the hexatriene complex 19m is produced.
The corresponding potential energy profile is provided in the
Supporting Information. The hydrogen transfer is a slightly
exothermic process, -2.7 kcal mol-1 in terms of ∆Eelec, -3.2
kcal mol-1 in terms of ∆∆G298. The optimized parameters of
15m and 19m exhibit the expected features of the complexed
vinylidene and hexatriene ligands. The TS(19mf25) exhibits
one strong imaginary frequency (604.3i cm-1), which reflects
the ring-closing process. In terms of ∆E# the TS(19mf25)
elec
is 12.6 kcal mol-1 above 19m. Including entropic effects
increases the reaction barrier (∆∆G#298) to 14.4 kcal mol-1
.
The ring closure process in the TS(19mf25) is more
advanced than in the TS(11of23o) or the TS(10hf23h) of
path 1. Compared with the TS(11of12o)/TS(10hf23h), the
newly formed C1-C bond in the TS(19mf25) is 0.529 Å/0.496
Å shorter. The formation of the π-complex 25 and the
subsequent rearrangement to the pyrrole 13 are exothermic
processes. In terms of ∆Eelec the π-complex 25 lies 32.8 kcal
mol-1 below the hexatriene 19m and pyrrole 13 is 16.2 kcal
mol-1 more stable than 25 (Figure 7).
If we now consider the energetics calculated for the paricular
steps of path 1 and path 2, we can conclude that the R-cycliza-
tion reactions of the thio species are kinetically and thermody-
namically favored over the analogous reactions of the oxo
species (Figure 7). From comparison of the relative energies
From Figure 6 it is evident that the possible different behavior
of the oxo and thio species reacting according to path 2 must
be determined by the first elementary reaction step, that is, by
the formation of the vinylidene complexes 15. An examination
of the PES calculated for path 2 of the R-cyclization reactions
(Figure 6 and Figure 7, right side) shows that formation of the
vinylidene 15m is an endothermic process in terms of ∆Eelec
and ∆∆H298. However, in this case here the elimination of
methanethiol with a ∆Eelec(11mf15m) of 13.0 kcal mol-1 is

4990 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
with respect to the most accessible reactants 11m and 10f it
follows that for both reaction pathways the highest stationary
points on the particular PESs correspond to the transition states
for the ring-closing processes. On the PES of ∆Eelec and ∆∆H288
path 1 is favored over path 2, for both thio and oxo species. In
terms of ∆Eelec the TS(19mf25) of path 2 are 7.6 and 7.9 kcal
mol-1 above TS(11of23o) and TS(10hf23h) of path 1 of the
thio and oxo species, respectively. However, considering
entropic contributions changes this situation in favor of path 2.
On the PES of ∆∆G298 TS(19mf25) are now 8.0 and 7.7 kcal
mol-1 below TS(11of23o) and TS(10hf23h), respectively.
Furthermore, 11o and 10h, with a ∆∆G298 of 5.5 and 6.5 kcal
mol-1 above 11m and 10f, respectively, are quite unfavorable
for the begining of R-cyclization reactions, and therefore we
believe that path 1 is not relevant for the mechanism under study.
Further support for path 2 comes also from the experimentally
detected formation of the 1H-pyrrole 22 from the closely related
5-aza-1-tungsta-1,3,5-hexatriene complex 20 (Scheme 5).21b
Summary and Conclusions
Remarkable reactivity differences of isostructural (alkyl)-
ethoxycarbene [(OC)5WdC(OEt)CH2R] (7a-c; R ) n-Pr, Me,
c-C7H7) and (alkyl)thiocarbene complexes [(OC)5MdC(SEt)-
CH2R] (8a-e; M ) W, Cr; R ) n-Pr, Me, c-C7H7, c-C6H7Fe-
(CO)3) toward imidoyl chlorides R1ClCdNCHR2R3 (9a-f; R1
) t-Bu, Ph, 2-furyl; R2 ) H, Me; R3 ) Me, Et, Ph) were found.
The reaction of (alkyl)ethoxycarbene complexes 7a-c with
imidoyl chlorides in the presence of triethylamine afforded (N-
enamino)ethoxycarbene complexes 12, whereas (alkyl)thiocar-
bene complexes 8a-e gave pyrroles 17 and 16, respectively.
The formation of compounds 12 was shown to involve a
metalla(di-π-methane) skeletal rearrangement of the (â-imino)-
ethoxycarbene complexes 10a-e, by which the C-C bond
between the R-carbon atom and the carbene carbon atom is
broken under the influence of the â-imino functionality. On the
other hand, 1H- and 2H-pyrroles 16 and 17 were obtained by
R-cyclization of the (â-imino)thiocarbene complexes 11a-l.
The comparison of the calculated PESs for the preferred
reaction pathways is depicted in Figure 8. As discussed in the
previous sections, the first elementary step of both reaction
channels begins with the lowest energy oxo (10f) and thio (11m)
reactants. The MDPM rearrangements are facile one-step
reactions that are due to an intramolecular associative process.
The R-cyclization reactions proceed stepwise following the
dissociative mechanism of the methanethiol/methanol elimina-
tion. From Figure 8 it is evident that the R-cyclization reaction
of both the thio complex 11m and the oxo complex 10f is
thermodynamically favored over the corresponding MDPM
rearrangement. The overall exothermicity of the R-cyclization
reactions with a ∆Eelec(13) of -31.0 kcal mol-1 (X ) O) and
-38.7 kcal mol-1 (X ) S) is much larger than that of the
MDPM rearrangements, for which ∆Eelec amounts to -5.7 kcal
mol-1 for syn-12f (X ) O) and -1.7 kcal mol-1 for syn-12m
(X ) S) (Figure 8, top). Thus, the different reactivity of the
oxo and thio species should be due either to the kinetic factors
or to the relative ease of the particular elementary steps.
The activation barriers of the MDPM rearrangements with a
∆E#elec of 14.9 kcal mol-1 for TS(10ff12f) (X ) O) and 10.7
kcal mol-1 for TS(11mf12m) (X ) S) do not differ much
from the activation barrier of the ring-closing process of 12.6
kcal mol-1 calculated for TS(19mf25) of the R-cyclization
reaction. Considering entropic contributions slightly raises the
activation barriers, but the differences between ∆∆G#298 of TS-
(10ff12f)/TS(11mf12m) and TS(19mf25) are still in the
Figure 8. Potential energy surfaces of ∆Eelec (top) and ∆∆G298
(bottom) for the preferred reaction paths of the MDPM rearrange-
ments and the R-cyclization reactions of the oxo (10f) and thio
(11m) reactants. The stationary points of the oxo complexes are
connected by the dashed lines and those of the thio species by the
solid lines.
range of 2 kcal mol-1 (Figure 8, bottom). These findings suggest
comparable kinetic forces for the MDPM rearrangements 10f
f syn-12f/11m f syn-12m and the elementary ring-closing
step 19m f 25 of the R-cyclization reaction. However, taking
into account the reaction barrier of the reverse processes syn-
12m f 11m (∆∆G#298 ) 11.9 kcal mol-1) and syn-12f f 10f
(∆∆G#298 ) 18.0 kcal mol-1) we can conclude that in addition
to the above-discussed thermodynamical grounds the R-cycliza-
tion reaction of the thio complex 11m is also favored because
of the kinetic instability of the thio product syn-12m of the
MDPM rearrangement. Furthermore, in terms of ∆∆G298, TS-
(19mf25) lies 8.3 kcal mol-1 above the reactant 11m and
should be more easily accessible than that of the MDPM
rearrangement [TS(11mf12m)], which is 13.1 kcal mol-1
above 11m. For the oxo complex 10f the elimination of
methanol requires more energy [∆Eelec(15) ) 20.7 kcal mol-1
]
than the activation barrier for TS(10ff12f) of the MDPM
rearrangement (∆E# ) 14.9 kcal mol-1) and TS(19mf25) of
the R-cyclization reaction is 30.6 kcal mol-1 above the reactant
10f (Figure 8, top). Although entropic contributions stabilizes
15 with respect to TS(10ff12f), the elimination of methanol
is still endothermic and the transition state of the R-cyclization

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4991
reaction is 1.2 kcal mol-1 above that of the MDPM rearrange-
ment (Figure 8 bottom). Thus, the MDPM rearrangement of
the oxo reactant 10f is a preferred reaction due to the kinetic
stability of the syn-12f product, while the R-cyclization reaction
is unfavorable due to the presence of high-energetic stationary
states.
sodium carbonate (254 mg, 2.40 mmol), and ethanethiol (248 mg,
4.00 mmol) were reacted for 1 h at -40 °C as described above to
give compound 8b (815 mg, 96%, Rf ) 0.5 in n-pentane, red oil).
1
3
8b. H NMR (400 MHz, CDCl3, 25 °C): δ 3.81 (q, J ) 7.7
Hz, 2H; 2-H2), 3.01 (q, 3J ) 7.6 Hz, 2H; SCH2), 1.36 (t, 3J ) 7.6
3
Hz, 3H; SCH2CH3), 1.30 (t, J ) 7.7 Hz, 3H; 3-H3). 13C NMR
(CDCl3, 25 °C): δ 339.7 (Cq, C1), 206.8 and 197.6 [Cq, 1:4 C;
trans- and cis-CO of W(CO)5], 52.4 (WdCCH2), 36.8 (SCH2), 14.2
(CH2CH3), 11.6 (SCH2CH3). IR (n-pentane): ν˜ 2066.5 (50), 1957.9
(80), 1951.7 (100), 1938.8 (60) cm-1 (CtO). MS (70 eV, EI): m/z
(%) 426 (28) [M]+, 370 [M - 2CO]+, 369 (18), 342 (38) [M -
3CO]+, 314 [M - 4CO]+, 313 (100). Anal. Calcd (%) for C10H10O5-
SW (426.1): C 28.17, H 2.37. Found: C 28.45, H 2.39.
Pentacarbonyl[2-(cyclohepta-2,4,6-trien-1-yl)-1-(ethylthio)et-
hylidene]tungsten (8c). Pentacarbonyl[2-(cyclohepta-2,4,6-trien-
1-yl)-1-ethoxythylidene]tungsten (7c) (972 mg, 2.00 mmol), sodium
carbonate (254 mg, 2.40 mmol), and ethanethiol (248 mg, 4.00
mmol) were reacted for 6 h at -40 °C as described above to give
a 3:1 mixture of 8c/8c′ and crystallized from n-pentane at -20 °C
(950 mg, 95%, Rf ) 0.8 in n-pentane/dichloromethane, 4:1, red
crystals, mp 49 °C).
Experimental Section
All operations were carried out under an atmosphere of argon.
1H and 13C NMR spectra were routinely recorded on Bruker ARX
300 and Bruker AMX 400 instruments. COSY, HMQC, HMBC,
TOCSY, and NOE experiments were performed on Bruker AMX
400, Inova 500, and Varian Unity Plus 600 instruments. Chemical
shifts δ were recorded against TMS as internal standards. IR spectra
were recorded on a Biorad Digilab Division FTS-45 FT-IR
spectrophotometer. Mass spectra were measured on a Finnigan
Mat8200. Elemental analyses were determined on a Vario EL III
elemental analyzer. All melting points reported are uncorrected.
Analytical TLC plates (Merck DC-Alufolien Kieselgel 60F240) were
viewed by UV light (254 nm) and stained using iodine. Rf values
refer to TLC tests. Chromatographic purification was performed
on Merck Kieselgel 60. All reactions were performed under argon.
The solvents were used as purchased and were not dried further.
7c,22a 7d,22b 9,20 and N-benzyl-R,R-d2-benzamide23 were prepared
according to literature methods, and syntheses of the compounds
7a,b,e22c were achieved analogous to the synthesis of pentacarbonyl-
(1-methoxyethylidene)chromium.
8c [8c′]. 1H NMR (400 MHz, CDCl3, 25 °C): δ 6.65, 6.25, and
5.33 [6.67, 6.25, and 5.24] (m each, 2:2:2 H; from H-2′ to H-7′ of
C7H7), 3.94 [4.04] (q, 3J ) 7.8 [7.4] Hz, 2H; 2-H2), 2.99 [3.64] (q,
3J ) 7.7 [7.5] Hz, 2H; SCH2), 2.82 [2.56] (m, 1H; 1′-H of C7H7),
1.34 [1.56] (t, 3J ) 7.7 [7.5] Hz, 3H; SCH2CH3). 13C NMR (CDCl3,
25 °C): δ 334.9 (Cq, C1), 206.3 and 197.6 [Cq, 1:4 C; trans- and
cis-CO of W(CO)5], 131.1, 126.2, and 124.2 [131.1, 125.5, and
124.3] (CH, 2:2:2 C, from C-2′ to C-7′ of C7H7), 59.7 [67.0] (CH2,
C2), 41.7 [40.5] (CH, C1′), 38.3 [43.0] (SCH2), 11.6 [12.4] (SCH2-
CH3). IR (n-pentane): ν˜ 2066.1 (50), 1961.3 (60), 1949.9 (100),
1943.0 (90), 1935.6 (80) cm-1 (CtO). MS (70 eV, EI): m/z (%)
502 [M]+, 446 [M - 2CO]+, 418 [M - 3CO]+, 390 [M - 4CO]+.
Anal. Calcd (%) for C16H14O5SW (502.0): C 38.25, H 2.81.
Found: C 38.25, H 2.62.
Pentacarbonyl[1-(ethylthio)pentylidene]tungsten (8a). Pen-
tacarbonyl(1-ethoxypentylidene)tungsten (7a) (876 mg, 2.00 mmol)
in methanol (5 mL) was added to a stirred suspension of sodium
carbonate (254 mg, 2.40 mmol) in methanol (20 mL) at -40 °C.
After ca. 5 min, ethanethiol (248 mg, 4.00 mmol) in methanol (1
mL) was added dropwise to the yellow suspension. The reaction
mixture was stirred for 1 h at -40 °C and then quenched by addition
of a few drops of 85% phosphoric acid to give a red solution. Water
(10 mL) was added and the product was extracted with n-pentane
(3 × 50 mL). The combined organic layers were dried over MgSO4
and then concentrated under reduced pressure to give a 13:2 mixture
of 8a/8a′ (880 mg, 97%, Rf ) 0.6 in n-pentane, red oil).
Pentacarbonyl[1-(ethylthio)-2-{tricarbonyl(2,4-cyclohexadien-
1-yl)iron}ethylidene]tungsten (8d). To pentacarbonyl[1-ethoxy-
2-{tricarbonyl(2,4-cyclohexadien-1-yl)iron}ethylidene]tungsten (7d)
(200 mg, 0.33 mmol) in dichloromethane/ether, 1:3 (2 mL), was
added a mixture of ethanethiol (40 mg, 0.65 mmol) and triethy-
lamine (66 mg, 0.65 mmol) in ether (0.5 mL) at -40 °C. Stirring
was continued for 2-2.5 h at this temperature. After the consump-
tion of the starting carbene complex, controlled by IR measure-
ments, the reaction was quenched with phosphoric acid (2-3 drops).
The afforded red solution was diluted with ether (30 mL) and then
extracted with water (3 × 15 mL). Finally the organic phase was
dried over magnesium sulfate, and the solvent was removed at
reduced pressure to give 8d (195 mg, 95%, Rf ) 0.7 in n-pentane/
dichloromethane, 4:1, red oil).
1
8a [8a′]. H NMR (400 MHz, CDCl3, 25 °C): δ 3.80 [3.78]
3
3
(dd, J ) 8.4 and 7.5 Hz, 2H; 2-H2), 2.99 [3.62] (q, J ) 7.7 Hz,
2H; SCH2), 1.66 [1.73] (m, 2H; 3-H2), 1.55 [1.55] (m, 2H; 4-H2),
1.36 [1.47] (t, 3J ) 7.7 Hz, 3H; SCH2CH3), 1.01 [1.01] (t, 3J ) 7.3
Hz, 3H; 5-H3). 13C NMR (CDCl3, 25 °C): δ 337.6 [345.2] (Cq,
WdC), 206.7 and 197.7 [206.4 and 197.6] [Cq, 1:4 C; trans- and
cis-CO of W(CO)5], 59.4 [64.7] (CH2, C2), 37.0 [42.4] (SCH2),
32.3 [34.7] (CH2, C3), 22.9 [22.6] (CH2, C4), 13.7 [13.7] (CH3,
C5), 11.6 [12.5] (SCH2CH3). IR (n-pentane): ν˜ 2065.9 (60), 1957.6
(90), 1950.4 (100), 1935.5 (80) cm-1 (CtO). MS (70 eV, EI): m/z
(%) 454 (29) [M]+, 398 [M - 2CO]+, 397 (22), 370 (54) [M -
3CO]+, 342 [M - 4CO]+, 341 (94), 281 (100). Anal. Calcd (%)
for C12H14O5SW (454.2): C 31.72, H 3.11. Found: C 32.01, H
3.13.
Pentacarbonyl[1-(ethylthio)propylidene]tungsten (8b). Pen-
tacarbonyl(1-ethoxypropylidene)tungsten (7b) (820 mg, 2.00 mmol),
1
8d. H NMR (400 MHz, C6D6, 25 °C): δ 4.76 (m, 1H; H-4′),
4.64 (m, 1H; 3′-H), 3.12 and 3.01 (m each, 1H each; 2-H2), 2.87
(m, 1H; 1′-H), 2.71 (m, 1H; 2′-H), 2.57 (m, 1H; 5′-H), 2.09 (q, 3J
(22) (a) Aumann, R.; Runge, M. Chem. Ber. 1992, 125, 259-264. (b)
Aumann, R.; La¨ge, M.; Krebs, B. Chem. Ber. 1994, 127, 731-738. (c)
Aumann, R.; Fischer, E. O. Angew. Chem. 1967, 79, 900-901; Angew.
Chem., Int. Ed. Engl. 1967, 6, 879-880.
) 7.7 Hz, 2H; SCH2), 1.84 (ddd, 1H; 6′endo-H), 0.89 (m, 1H; 6′exo
-
H), 0.62 (t, 3J ) 7.7 Hz, 3H; SCH2CH3). 13C NMR (C6D6, 25 °C):
δ 333.7 (Cq, C1), 211.6 [Cq, CO of Fe(CO)3], 206.2 and 198.1
(23) Axenrod, T.; Milne, G. W. A. Tetrahedron 1968, 24, 5775-5783.

4992 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
[Cq, 1:4 C; trans- and cis-CO of W(CO)5], 86.1 (CH, C-4′), 84.4
(CH, C-3′), 67.2 (CH2, C2), 64.6 (CH, C2′), 59.2 (CH, C-5′), 41.3
(CH, C-1′), 38.0 (SCH2), 29.7 (CH2, C-6′), 11.2 (SCH2CH3). IR
(n-pentane): ν˜ 2066.6 (60), 2052.0 (70), 1992.6 (40), 1957.6 (95),
1952.2 (100), 1941.7 (90), 1933.5 (90) cm-1 (CtO). MS (70 eV,
EI): m/z (%) 630 [M]+, 574 [M - 2CO]+, 490 [M - 5CO]+, 192
(100). HRMS (ESI-): m/z calcd for C18H13O8SFeW 628.9200,
found 628.9202.
1:4 C; trans- and cis-CO of W(CO)5], 145.9 (Cq, C4), 130.2 (CH,
C5), 72.5 (OCH2), 52.3 (NCH2), 34.4 [Cq, C(CH3)3], 30.3 (CH2,
C6), 30.2 [C(CH3)3], 22.9 (CH2, C7), 15.5 (OCH2CH3), 14.1 (NCH2-
CH3); 13.8 (CH3, C8). IR (cyclohexane): ν˜ 2064.3 (10), 1927.9
(100) cm-1 (CtO). MS (70 eV, EI): m/z (%): 549 (45) [M]+,
521 (27) [M - CO]+, 493 (34) [M - 2CO]+, 465 [M - 3CO]+,
463 (66), 437 [M - 4CO]+, 435 (75), 409 [M - 5CO]+, 407 (100).
Anal. Calcd (%) for C19H27O6NW (549.3): C 41.52, H 4.96, N
2.55. Found: C 41.83, H 4.97, N 2.89.
(4E)-[2-Ethoxy-3-ethylamino-4-tert-butyl]-3-aza-1-pentacar-
bonyltungstahexa-1,4-diene (syn-12b and anti-12b). Pentacar-
bonyl[1-ethoxypropylidene]tungsten (7b) (205 mg, 0.50 mmol),
N-ethyl-2,2-dimethylpropionimidoyl chloride (9a) (148 mg, 1.00
mmol), N,N-dimethylaminopyridine (6 mg, 0.05 mmol), and
triethylamine (51 mg, 0.50 mmol) were reacted for 1 day as
described above. Chromatography at 25 °C on silica gel (column
2 × 20 cm, n-pentane/dichloromethane, 95:5) afforded a pale yellow
fraction with a 3:1 mixture of syn-12b and anti-12b (176 mg, 68%,
Rf ) 0.5 (syn-12b) and Rf ) 0.6 (anti-12b) in n-pentane, pale yellow
oil).
Pentacarbonyl[1-(ethylthio)pentylidene]chromium (8e). Pen-
tacarbonyl(1-ethoxypentylidene)chromium (7e) (612 mg, 2.00
mmol), sodium carbonate (254 mg, 2.40 mmol), and ethanethiol
(248 mg, 4.00 mmol) were reacted for 1 h at -40 °C as described
above to give compound 8e (603 mg, 94%, Rf ) 0.6 in n-pentane,
red oil).
8e. 1H NMR (400 MHz, C6D6, 25 °C): δ 3.46 (dd, 3J ) 8.2 and
7.8 Hz, 2H; 2-H2), 2.17 (q, 3J ) 7.5 Hz, 2H; SCH2), 1.36 (m, 2H;
3
3-H2), 1.22 (m, 2H; 4-H2), 0.80 (t, J ) 7.5 Hz, 3H; SCH2CH3),
0.59 (t, 3J ) 7.6 Hz, 3H; 5-H3). 13C NMR (CDCl3, 25 °C): δ 370.4
(Cq, CrdC), 227.0 and 216.9 [Cq, 1:4 C; trans- and cis-CO of
W(CO)5], 58.0 (CH2, C2), 36.2 (SCH2), 32.3 (CH2, C3), 23.0 (CH2,
C4), 13.7 (CH3, C5), 11.2 (SCH2CH3). IR (n-pentane): ν˜ 2058.0
(40), 1960.5 (100), 1939.4 (60) cm-1 (CtO). MS (70 eV, EI): m/z
(%): 322 (13) [M]+, 294 (7) [M - CO]+, 266 (4) [M - 2CO]+,
238 (13), [M - 3CO]+, 210 (33) [M - 4CO]+, 182 (100) [M -
5CO]+. HRMS (ESI-): m/z calcd for C12H13O5SCr 320.9883, found
320.9894.
1
3
syn-12b. H NMR (500 MHz, CDCl3, 25 °C): δ 5.38 (q, J )
7.6 Hz, 1H; 5-H), 4.55 (m, 2H; OCH2), 4.17 and 2.84 (each m,
each 1H; NCH2), 1.92 (d, 3J ) 7.6 Hz, 3H; 6-H3), 1.44 (t, 3J ) 6.9
3
Hz, 3H; OCH2CH3), 1.32 [s, 9H; C(CH3)3], 1.11 (t, J ) 6.9 Hz,
3H; NCH2CH3). 13C NMR (CDCl3, 25 °C): δ 230.0 (Cq, WdC),
200.5 and 199.0 [Cq, 1:4 C; trans- and cis-CO of W(CO)5], 149.5
(Cq, C4), 129.8 (CH, C5), 73.2 (OCH2), 47.2 (NCH2), 34.8 [Cq,
C(CH3)3], 30.2 [C(CH3)3], 15.4 (OCH2CH3), 14.3 (CH3, C6), 11.8
(NCH2CH3). anti-12b. 1H NMR (500 MHz, CDCl3, 25 °C): δ 5.02
(q, 3J ) 7.6 Hz, 1H; 5-H), 4.52 (q, 2H; OCH2), 4.65 and 3.28 (each
m, each 1H; NCH2), 1.86 (d, 3J ) 7.6 Hz, 3H; 6-H3), 1.34 (t, 3J )
7.1 Hz, 3H; OCH2CH3), 1.25 (t, 3J ) 7.2 Hz, 3H; NCH2CH3), 1.16
[s, 9H; C(CH3)3]. 13C NMR (CDCl3, 25 °C): δ 228.2 (Cq, WdC),
200.7 and 197.8 [Cq, 1:4 C; trans- and cis-CO of W(CO)5], 146.8
(Cq, C4), 123.9 (CH, C5), 72.5 (OCH2), 52.3 (NCH2), 34.3 [Cq,
C(CH3)3], 29.7 [C(CH3)3], 15.5 (OCH2CH3), 14.1 (NCH2CH3), 13.9
(CH3, C6). IR (cyclohexane): ν˜ 2064.2 (10), 1927.5 (100) cm-1
(CtO). MS (70 eV, EI): m/z (%) 521 (37) [M]+, 493 (22) [M -
CO]+, 465 (35) [M - 2CO]+, 437 (14) [M - 3CO]+, 406 (40),
381 (100) [M - 5CO]+. HRMS (ESI+): m/z calcd for C17H23NO6-
WNa 544.0930, found 544.0917 [M + Na]+.
(4E)-[2-Ethoxy-3-ethylamino-4-tert-butyl]-3-aza-1-pentacar-
bonyltungsta-1,4-diene (syn-12a and anti-12a). To pentacarbonyl-
[1-ethoxypentylidene]tungsten (7a) (219 mg, 0.50 mmol) in dichlo-
romethane (1 mL) in a 5 mL screw-top vessel was first added a
mixture of N-ethyl-2,2-dimethylpropionimidoyl chloride (9a) (148
mg, 1.00 mmol) and N,N-dimethylamino pyridine (6 mg, 0.05
mmol) in dichloromethane (2 mL) at room temperature. Then to
this reaction mixture was dropped triethylamine (51 mg, 0.50 mmol)
in dichloromethane (0.5 mL) with stirring. The reaction was
controlled by TLC and continued for 1 day at this temperature.
After the consumption of compound 7a, diethyl ether (10-15 mL)
was added to the reaction mixture and the precipitate was removed
by centrifugation. The solvent was evaporated at reduced pressure.
Chromatography at 25 °C on silica gel (column 2 × 20 cm,
n-pentane/dichloromethane, 95:5) afforded a pale yellow fraction
with a 5:2 mixture of syn-12a and anti-12a (224 mg, 82%, Rf )
0.6 (syn-12a) and Rf ) 0.7 (anti-12a) in n-pentane, pale yellow
oil).
(4E)-[(5-Cyclohepta-2,4,6-trien-1-yl)-2-ethoxy-3-ethylamino-
4-phenyl]-3-aza-1-pentacarbonyltungstapenta-1,4-diene (syn-12c
and anti-12c). Pentacarbonyl[2-(cyclohepta-2,4,6-trien-1-yl)-1-
ethoxythylidene]tungsten (7c) (243 mg, 0.50 mmol), N-ethylben-
zimidoyl chloride (9b) (168 mg, 1.00 mmol), N,N-dimethylami-
nopyridine (6 mg, 0.05 mmol), and triethylamine (51 mg, 0.50
mmol) were reacted for 1 day as described above. Chromatography
at 25 °C on silica gel (column 2 × 20 cm, n-pentane/dichlo-
romethane, 95:5) afforded a pale yellow fraction with a 10:9 mixture
of syn-12c and anti-12c (215 mg, 70%, Rf ) 0.8 (for both isomers)
in n-pentane/dichloromethane, 4:1, pale yellow oil).
syn-12a. 1H NMR (600 MHz, CDCl3, 25 °C): δ 5.24 (dd, 3J )
10.4 and 4.4 Hz, 1H; 5-H), 4.57 (m, 2H; OCH2), 4.19 and 2.85
(each m, each 1H; NCH2), 2.42 and 2.28 (each m, each 1H; 6-H2),
3
1.53 and 1.44 (each m, each 1H; 7-H2), 1.44 (t, J ) 7.0 Hz, 3H;
OCH2CH3), 1.33 [s, 9H; C(CH3)3], 1.12 (t, 3J ) 7.0 Hz, 3H; NCH2-
3
CH3), 0.98 (t, J ) 7.3 Hz, 3H; 8-H3). 13C NMR (CDCl3, 25 °C):
δ 229.9 (Cq, WdC), 200.5 and 199.0 [Cq, 1:4 C; trans- and cis-
CO of W(CO)5], 148.5 (Cq, C4), 135.8 (CH, C5), 73.2 (OCH2),
47.1 (NCH2), 34.9 [Cq, C(CH3)3], 30.5 [C(CH3)3], 30.3 (CH2, C6),
22.8 (CH2, C7), 15.4 (OCH2CH3), 13.9 (CH3, C8), 11.7 (NCH2-
CH3). anti-12a. 1H NMR (600 MHz, CDCl3, 25 °C): δ 4.90 (t, 3J
) 8.0 Hz, 1H; 5-H), 4.53 (m, 2H; OCH2), 4.66 and 3.27 (each m,
each 1H; NCH2), 2.27 (m, 2H; 6-H2), 1.46 (m, 2H; 7-H2), 1.34 (t,
syn-12c. 1H NMR (500 MHz, CDCl3, 25 °C): δ 7.33-7.29 and
7.11 (each m, 8:2 H, o-, m-, p-H Ph of both syn- and anti-isomers),
6.68 (m, 2H; 4′-H and 5′-H), 6.36 and 6.26 (each m, each 1H;
3′-H and 6′-H), 6.18 (d, J ) 10.4 Hz, 1H; 5-H), 5.41 and 5.27
(four-line pattern, each 1H; 2′-H and 7′-H), 4.67 and 4.61 (q, AB
3
3J ) 7.0 Hz, 3H; OCH2CH3), 1.26 (t, J ) 7.1 Hz, 3H; NCH2-
3
3
CH3), 1.15 [s, 9H; C(CH3)3], 0.98 (t, J ) 7.4 Hz, 3H; 8-H3). 13C
NMR (CDCl3, 25 °C): δ 228.1 (Cq, WdC), 200.7 and 197.8 [Cq,

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4993
3
3
system, J ) 7.0 Hz, 2H; OCH2), 4.02 and 2.84 (each q, J ) 7.2
n-pentane/dichloromethane, 95:5) afforded a pale yellow fraction
of anti-12e (162 mg, 61%, Rf ) 0.5 in n-pentane, pale yellow oil).
3
Hz, 2H; NCH2), 2.68 (m, 1H; 1′-H), 1.51 (t, J ) 7.0 Hz, 3H;
OCH2CH3), 1.13 (t, 3J ) 7.2 Hz, 3H; NCH2CH3). 13C NMR (CDCl3,
25 °C): δ 232.1 (Cq, WdC), 200.6 and 199.0 [Cq, 1:4 C; trans-
and cis-CO of W(CO)5], 143.6 (Cq, C4), 134.4 (CH, C5), 133.7
(Cq, i-C Ph), 131.6 and 130.3 (each CH, C4′ and C5′), 129.1, 129.0,
128.6, 128.5, 128.4, 128.0 (each CH, o-, m-, and p-C Ph of both
syn- and anti-isomers), 125.1 (2 signals, each CH, C3′ and C6′),
121.2 and 120.0 (each CH, C2′ and C7′), 74.1 (OCH2), 45.8
(NCH2), 38.6 (CH, C1′); 15.4 (OCH2CH3), 13.1 (NCH2CH3). anti-
12c. 1H NMR (500 MHz, CDCl3, 25 °C): δ 6.66 (m, 2H; 4′-H and
1
3
anti-12e. H NMR (400 MHz, CDCl3, 25 °C): δ 5.31 (sep, J
3
) 6.7 Hz, 1H; NCH), 5.15 (q, J ) 7.6 Hz 1H; 5-H), 4.67 and
3
3
4.52 (q, AB system, J ) 7.1 Hz, 2H; OCH2), 1.87 (d, J ) 7.6
Hz, 3H; 6-H3), 1.36 (t, 3J ) 7.1 Hz, 3H; OCH2CH3), 1.29 and 1.28
[each d, 3J ) 6.7 Hz, each 3H; NCH(CH3)2], 1.18 [s, 9H; C(CH3)3].
13C NMR (CDCl3, 25 °C): δ 230.6 (Cq, WdC), 201.0 and 197.8
[Cq, 1:4 C; trans- and cis-CO of W(CO)5], 146.6 (Cq, C4), 123.3
(CH, C5), 72.8 (OCH2), 59.0 (NCH), 34.5 [Cq, C(CH3)3], 29.8
[C(CH3)3], 25.2 and 20.2 [NCH(CH3)2], 15.7 (OCH2CH3), 14.3
(CH3, C6). IR (cyclohexane): ν˜ 2064.0 (10), 1927.8 (100) cm-1
(CtO). MS (70 eV, EI): m/z (%): 535 (40) [M]+, 507 (34) [M -
CO]+, 479 (28) [M - 2CO]+, 451 (15) [M - 3CO]+, 420 (36),
395 [M - 5CO]+, 393 (100). HRMS (ESI+): m/z calcd for C18H25-
NO6WNa 558.1086, found 558.1076 [M + Na]+.
3
5′-H), 6.24 (m, 2H; 3′-H and 6′-H), 5.79 (d, J ) 10.4 Hz, 1H;
5-H), 5.23 (four-line pattern, 2H; 2′-H and 7′-H), 4.58 (q, 3J ) 7.0
Hz, 2H; OCH2), 4.02 (s, br, 2H; NCH2), 2.63 (m, 1H; 1′-H), 1.31
3
3
(t, J ) 7.2 Hz, 3H; NCH2CH3) 1.26 (t, J ) 7.0 Hz, 3H; OCH2-
CH3). 13C NMR (CDCl3, 25 °C): δ 231.0 (Cq, WdC), 200.9 and
197.7 [Cq, 1:4 C; trans- and cis-CO of W(CO)5], 139.2 (Cq, C4),
134.0 (Cq, i-C Ph), 131.7 (CH, C5), 131.2 (CH, C4′ and C5′), 124.9
(CH, C3′ and C6′), 123.5 (CH, C2′ and C7′), 73.1 (OCH2), 51.3
(NCH2), 38.6 (CH, C1′), 15.2 (OCH2CH3), 14.2 (NCH2CH3). IR
(cyclohexane): ν˜ 2064.8 (10), 1929.4 (100), 1916.5 (30) cm-1 (Ct
O). MS (70 eV, EI): m/z (%) 617 (2) [M]+, 589 (3) [M - CO]+,
533 (5) [M - 3CO]+, 483 (12). HRMS (ESI+): m/z calcd for
C25H23NO6WNa 640.0931, found 640.0940 [M + Na]+.
(4E)-[2-Ethoxy-3-ethylamino-4-phenyl]-3-aza-1-pentacarbo-
nyltungstaocta-1,4-diene (syn-12d and anti-12d). Pentacarbonyl-
[1-ethoxypentylidene]tungsten (7a) (219 mg, 0.50 mmol), N-
ethylbenzimidoyl chloride (9b) (168 mg, 1.00 mmol), N,N-
dimethylaminopyridine (6 mg, 0.05 mmol), and triethylamine (51
mg, 0.50 mmol) were reacted for 1 day as described above.
Chromatography at 25 °C on silica gel (column 2 × 20 cm,
n-pentane/dichloromethane, 95:5) afforded a pale yellow fraction
with a 2:1 mixture of syn-12d and anti-12d (202 mg, 71%, Rf )
0.5 (syn-12d) and Rf ) 0.6 (anti-12d) in n-pentane, pale yellow
oil).
5-Ethyl-2-phenyl-3-propyl-1H-pyrrole (16a) and N-Propy-
lthiobenzimidic acid Ethyl Ester (14d and 14d′). To a mixture
of pentacarbonyl[1-(ethylthio)pentylidene]tungsten (8a) (454 mg,
1.00 mmol) and N-propylbenzimidoyl chloride (9d) (363 mg, 2.00
mmol) in diethyl ether (3 mL) in a 5 mL flask was added
triethylamine (101 mg, 1.00 mmol) in diethyl ether (0.5 mL) with
stirring at -40 °C. The stirring was continued for 10-15 min at
this temperature. After the consumption of 8a (controlled by TLC),
the reaction mixture was centrifuged, the precipitate was removed,
and the solvent was evaporated at reduced pressure. The 1H NMR
spectrum indicated the formation of 16a, 14d, and 14d′ in a ratio
of 3:2:1, respectively. Chromatography at 25 °C on silica gel
(column 2 × 20 cm, n-pentane/dichloromethane, 4:1) afforded
compound 16a (166 mg, 78%, Rf ) 0.4 in n-pentane/dichlo-
romethane, 4:1, yellowish oil). Isomers 14d and 14d′ were not
isolated and characterized from the 1H NMR spectrum of the
reaction mixture.
syn-12d. 1H NMR (400 MHz, CDCl3, 25 °C): δ 7.39-7.32 and
7.18 (each m, 8:2 H, o-, m-, p-H Ph of both syn- and anti-isomers),
3
5.86 (dd, J ) 7.1 and 8.0 Hz, 1H; 5-H), 4.65 and 4.63 (q, AB
3
system, J ) 7.0 Hz, 2H; OCH2), 4.0 and 2.82 (each m, each 1H;
NCH2), 2.50 and 2.38 (each m, each 1H; 6-H2), 1.65 (m, 2H; 7-H2),
3
3
1.48 (t, J ) 7.0 Hz, 3H; OCH2CH3), 1.10 (t, J ) 7.1 Hz, 3H;
NCH2CH3), 1.04 (t, 3J ) 7.2 Hz, 3H, 8-H3). 13C NMR (CDCl3, 25
°C): δ 232.0 (Cq, WdC), 200.8 and 198.8 [Cq, 1:4 C; trans- and
cis-CO of W(CO)5], 142.3 (Cq, C4), 134.8 (CH, C5), 134.3 (Cq,
i-C Ph), 129.1, 128.7, 128.4, 128.3, 128.1 (each CH, o-, m-, and
p-C Ph of both syn- and anti-isomers), 73.7 (OCH2), 45.7 (NCH2),
31.1 (CH2, C6), 22.5 (CH2, C7), 15.4 (OCH2CH3), 14.1 (CH3, C8),
1
16a. H NMR (400 MHz, CDCl3, 25 °C): δ 7.74 (s, br, 1H;
NH), 7.36-7.35 (m, 4H; o-, and m-H Ph), 7.22-7.17 (m, 1H; p-H
4
4
3
Ph), 5.89 (d, br, 1H; J ) 3.0 Hz, 4-H), 2.63 (dq, J ) 0.8 and J
3
) 7.6 Hz, 2H; 6-H2), 2.57 (dd, J ) 7.7 and 7.9 Hz, 2H; 8-H2),
3
1.64 (m, 2H; 9-H2), 1.26 (t, 3H; 7-H3), 0.96 (t, J ) 7.4 Hz, 3H;
10-H3). 13C NMR (CDCl3, 25 °C): 134.1 and 134.0 (each Cq, i-C
Ph and/or C5), 128.6, 126.4 and 125.6 (each CH, o-, m-, and p-C
Ph), 126.4 (Cq, C2), 121.7 (Cq, C3), 106.8 (CH, C4), 28.8 (CH2,
C8), 24.3 (CH2, C9), 20.9 (CH2, C6), 14.3 (CH3, C10), 13.4 (CH3,
C7). IR (film): ν˜ 3468.7, br, 3426.6, 3392.1 br cm-1 (N-H). MS
(70 eV, EI): m/z (%) 213 (38) [M]+, 198 (25), 184 (100), 168
(52), 155 (22), 77 (12). Anal. Calcd (%) for C15H19N (213.3): C
84.46, H 8.98, N 6.57. Found: C 84.42, H 8.87, N 6.50.
1
13.1 (NCH2CH3). anti-12d. H NMR (400 MHz, CDCl3, 25 °C):
δ 5.43 (t, 3J ) 7.7 Hz, 1H; 5-H), 4.56 (q, 3J ) 7.0 Hz, 2H; OCH2),
4.0 (q, 2H; NCH2), 2.29 (q, 3J ) 7.5 Hz, 1H; 6-H2), 1.48 (m, 2H;
3
3
7-H2), 1.25 (t, J ) 7.1 Hz, 3H; NCH2CH3), 1.23 (t, J ) 7.0 Hz,
3H; OCH2CH3), 0.93 (t, 3J ) 7.4 Hz, 3H, 8-H3). 13C NMR (CDCl3,
25 °C): δ 230.4 (Cq, WdC), 200.6 and 197.8 [Cq, 1:4 C; trans-
and cis-CO of W(CO)5], 137.8 (Cq, C4), 134.8 (Cq, i-C Ph), 131.4
(CH, C5), 72.9 (OCH2), 51.4 (NCH2), 30.4 (CH2, C6), 22.9 (CH2,
C7), 15.2 (OCH2CH3), 14.1 (NCH2CH3), 13.8 (CH3, C8). IR
(cyclohexane): ν˜ 2062.6 (10), 1928.4 (100), 1916.4 (30) cm-1 (Ct
O). MS (70 eV, EI): m/z (%) 569 (8) [M]+, 541 (18) [M - CO]+,
485 (100) [M - 3CO]+. HRMS (ESI+): m/z calcd for C21H23NO6-
WNa 592.0930, found 592.0934 [M + Na]+.
(4E)-[2-Ethoxy-3-isopropylamino-4-tert-butyl]-3-aza-1-pen-
tacarbonyltungstahexa-1,4-diene (anti-12e). Pentacarbonyl[1-
ethoxypropylidene]tungsten (7b) (205 mg, 0.50 mmol), N-isopropyl-
2,2-dimethylpropionimidoyl chloride (9c) (162 mg, 1.00 mmol),
N,N-dimethylaminopyridine (6 mg, 0.05 mmol), and triethylamine
(51 mg, 0.50 mmol) were reacted for 1 day as described above.
Chromatography at 25 °C on silica gel (column 2 × 20 cm,
1
14d [14d′]. H NMR (300 MHz, CDCl3, 25 °C): δ 7.53, 7.37,
and 7.23 (each m, 10H; o-, m-, and p-H Ph of both isomers), 3.60
[3.27] (dd, 3J ) 6.9 [6.9] and 7.2 [7.0] Hz, 2H; NCH2), 2.58 [3.03]
(q, 3J ) 7.4 [7.4] Hz, 2H; SCH2), 1.79 [1.59] (m, 2H; NCH2CH2),
1.08 [1.32] (t, 3J ) 7.4 [7.4] Hz, 3H; SCH2CH3), 1.01 [0.87] (t, 3J
) 7.4 [7.4] Hz, 3H; NCH2CH2CH3).

4994 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
4
2,5-Diphenyl-3-propyl-1H-pyrrole (16b) and N-Benzylth-
iobenzimidic Acid Ethyl Ester (14e and 14e′). Pentacarbonyl[1-
(ethylthio)pentylidene]tungsten (8a) (454 mg, 1.00 mmol), N-ben-
zylbenzimidoyl chloride (9e) (459 mg, 2.00 mmol), and triethylamine
(101 mg, 1.00 mmol) were reacted as described above to give
compounds 16b (182 mg, 70%, Rf ) 0.4 in n-pentane/dichlo-
romethane, 4:1, yellowish oil), 14e, and 14e′.
Hz, 2H; 7-H2), 2.19 (d, br, J ) 0.5 Hz, 3H; 6-H3), 1.58 (m, 2H;
8-H2), 1.33 [s, 9H; C(CH3)3], 0.97 (t, 3J ) 7.4 Hz, 3H; 9-H3). 13
C
NMR (CDCl3, 25 °C): 132.8 (Cq, C2), 123.1 (Cq, C5), 118.6 (Cq,
C3), 108.2 (CH, C4), 32.1 [Cq, C(CH3)3], 30.6 [C(CH3)3], 29.6
(CH2, C7), 24.9 (CH2, C8), 14.4 (CH3, C9), 12.8 (CH3, C6). IR
(film): ν˜ 3490.8, 3418.5, br cm-1 (N-H). MS (70 eV, EI): m/z
(%): 179 (22) [M]+, 164 (100), 135 (11), 85 (10). Anal. Calcd
(%) for C12H21N (179.3): C 80.38, H 11.81, N 7.82. Found: C
80.26, H 11.70, N 7.64.
1
16b. H NMR (400 MHz, CDCl3, 25 °C): δ 8.18 (s, br, 1H;
4
NH), 7.45-7.11 (m, 10 H; o-, m-, and p-H Ph), 6.46 (d, br, J )
3
3.2 Hz, 1H; 4-H), 2.60 (dd, J ) 7.6 and 7.9 Hz, 2H; 6-H2), 1.67
(m, 2H; 7-H2), 0.97 (t, 3J ) 7.4 Hz, 3H; 8-H3). 13C NMR (CDCl3,
25 °C): 133.5 and 132.5 (each Cq, i-C Ph), 131.5 (Cq, C5), 129.3
(Cq, C2), 128.8, 128.7, 126.7, 126.2, 126.0, and 123.5 (each CH,
o-, m-, and p-C Ph), 123.5 (Cq, C3), 108.3 (CH, C4), 28.7 (CH2,
C6), 24.2 (CH2, C7), 14.2 (CH3, C8). IR (film): ν˜ 3436.4, 3380.0,
br cm-1 (N-H). MS (70 eV, EI): m/z (%): 261 (100) [M]+, 232
(96), 194 (15), 91 (63). Anal. Calcd (%) for C19H19N (261.4): C
87.31, H 7.33, N 5.36. Found: C 87.40, H 7.28, N 5.55.
1
3
14a. H NMR (400 MHz, CDCl3, 25 °C): δ 3.59 (q, J ) 7.2
Hz, 2H; NCH2), 2.71 (q, 3J ) 7.6 Hz, 2H; SCH2), 1.23 (t, 3J ) 7.2
Hz, 3H; NCH2CH3), 1.22 (t, 3J ) 7.6 Hz, 3H; SCH2CH3), 1.19 [s,
9H; C(CH3)3].
14e [14e′]. 1H NMR (400 MHz, CDCl3, 25 °C): δ 7.58, 7.42-
7.18 (each m, 20H; o-, m-, and p-H Ph of both isomers), 4.87 [4.54]
(s, 2H; NCH2), 2.62 [3.09] (q, 3J ) 7.4 [7.5] Hz, 2H; SCH2), 1.08
5-Methyl-2-phenyl-3-propyl-1H-pyrrole (16e) and N-Ethylth-
iobenzimidic Acid Ethyl Ester (14b and 14b′) (from 8a).
Pentacarbonyl[1-(ethylthio)pentylidene]tungsten (8a) (454 mg, 1.00
mmol), N-ethylbenzimidoyl chloride (9b) (335 mg, 2.00 mmol),
and triethylamine (101 mg, 1.00 mmol) were reacted as described
above to give compounds 16e (141 mg, 71%, Rf ) 0.4 in n-pentane/
dichloromethane, 4:1, yellowish oil), 14b, and 14b′.
3
[1.34] (t, J ) 7.4 [7.5] Hz, 3H; SCH2CH3).
5-Ethyl-2-(2-furyl)-3-propyl-1H-pyrrole (16c) and N-Propy-
lfuran-2-carboximidothioic Acid Ethyl Ester (14f and 14f′).
Pentacarbonyl[1-(ethylthio)pentylidene]tungsten (8a) (454 mg, 1.00
mmol), N-propylfuran-2-carboximidoyl chloride (9f) (343 mg, 2.00
mmol), and triethylamine (101 mg, 1.00 mmol) were reacted as
described above to give compounds 16c (104 mg, 51%, Rf ) 0.5
in n-pentane/dichloromethane, 4:1, yellowish oil), 14f, and 14f′.
1
16e. H NMR (500 MHz, CDCl3, 25 °C): δ 7.76 (s, br, 1H;
NH), 7.37-7.36 (m, 4H; o-, and m-H Ph), 7.23-7.19 (m, 1H; p-H
Ph), 5.87 (d, br, 4J ) 2.5 Hz, 1H; 4-H), 2.56 (dd, 3J ) 7.8 and 7.9
3
Hz, 2H; 7-H2), 2.30 (s, 3H; 6-H3), 1.63 (m, 2H, 8-H2), 0.96 (t, J
) 7.4 Hz, 3H; 9-H3). 13C NMR (CDCl3, 25 °C): 134.0 (Cq, i-C
Ph), 128.6, 126.4, and 125.6 (each CH, o-, m-, and p-C Ph), 127.5
(Cq, C5), 126.6 (Cq, C2), 121.9 (Cq, C3), 108.6 (CH, C4), 28.7
(CH2, C7), 24.4 (CH2, C8), 14.3 (CH3, C9), 13.1 (CH3, C6). IR
(film): ν˜ 3423.8, 3374.9, br cm-1 (N-H). MS (70 eV, EI): m/z
(%) 199 (33) [M], 170 (100), 128 (14), 77 (13). Anal. Calcd (%)
for C14H17N (199.3): C 84.37, H 8.60, N 7.03. Found: C 84.30, H
8.55, N 6.97.
1
16c. H NMR (600 MHz, CDCl3, 25 °C): δ 8.11 (s, br, 1H;
4
3
3
NH), 7.32 (dd, J ) 0.6 Hz, J ) 1.8 Hz, 1H; 5′-H), 6.43 (dd, J
) 1.8 Hz, 3J ) 3.3 Hz, 1H; 4′-H), 6.20 (dd, 4J ) 0.6 Hz, 3J ) 3.3
1
14b [14b′]. H NMR (400 MHz, CDCl3, 25 °C): δ 7.52, 7.36,
4
4
Hz, 1H; 3′-H), 5.83 (d, br, J ) 3.1 Hz, 1H; 4-H), 2.63 (dq, J )
0.5 and 3J ) 7.6 Hz, 2H; 6-H2), 2.55 (dd, 3J ) 7.6 and 7.8 Hz, 2H;
8-H2), 1.63 (m, 2H; 9-H2), 1.26 (t, 3H; 7-H3), 0.99 (t, 3J ) 7.4 Hz,
3H; 10-H3). 13C NMR (CDCl3, 25 °C): 148.5 (Cq, C2′), 139.3 (CH,
C5′), 134.0 (Cq, C5), 122.0 (Cq, C3), 118.4 (Cq, C2), 111.4 (CH,
C4′), 106.7 (CH, C4), 101.9 (CH, C3′), 28.9 (CH2, C8), 23.4 (CH2,
C9), 20.9 (CH2, C6), 14.2 (CH3, C10), 13.5 (CH3, C7). IR (film):
ν˜ 3473.8, 3424.9 (br) cm-1 (N-H). MS (70 eV, EI): m/z (%) 203
(59) [M]+, 188 (41), 174 (100), 146 (21), 130 (37), 117 (31), 77
(11), 55 (18). Anal. Calcd (%) for C13H17NO (203.3): C 76.81, H
8.43, N 6.89. Found: C 76.85, H 8.50, N 6.92.
and 7.23 (each m, 10H; o-, m-, and p-H Ph of both isomers), 3.66
3
3
[3.33] (q, J ) 7.2 [7.2] Hz, 2H; NCH2), 2.56 [3.0] (q, J ) 7.5
[7.4] Hz, 2H; SCH2), 1.34 [1.14] (t, 3J ) 7.2 [7.2] Hz, 3H; NCH2-
CH3), 1.06 [1.31] (t, J ) 7.5 [7.4] Hz, 3H; SCH2CH3).
3
2-tert-Butyl-3,5-dimethyl-1H-pyrrole (16f) and N-Ethyl-2,2-
dimethylthiopropionimidic Acid Ethyl Ester (14a). Pentacarbo-
nyl[1-(ethylthio)propylidene]tungsten (8b) (426 mg, 1.00 mmol),
N-ethyl-2,2-dimethylpropionimidoyl chloride (9a) (295 mg, 2.00
mmol), and triethylamine (101 mg, 1.00 mmol) were reacted as
described above to give compounds 16f (113 mg, 75%, Rf ) 0.5
in n-pentane/dichloromethane, 4:1, yellowish oil) and 14a.
1
14f [14f′]. H NMR (400 MHz, CDCl3, 25 °C): δ 7.50 [7.49]
1
16f. H NMR (400 MHz, CDCl3, 25 °C): δ 7.47 (s, br, 1H;
3
4
(dd, J ) 1.7 [1.8] and J ) 0.8 [0.8] Hz, 1H; 5′-H), 6.87 [6.75]
(d, br, 3J ) 3.3 [3.3] Hz, 1H; 3′-H), 6.45 [6.46] (dd, 3J ) 3.3 [3.3]
and 3J ) 1.7 [1.8] Hz, 1H; 4′-H), 3.69 [3.62] (dd, 3J ) 6.8 and 7.2
[6.4 and 7.2] Hz, 2H; NCH2), 2.88 [3.0] (q, 3J ) 7.4 [7.5] Hz, 2H;
NH), 5.63 (d, br, 4J ) 3.1 Hz, 1H; 4-H), 2.18 (d, br, 4J ) 0.7 Hz,
3H; 6-H3), 2.13 (s, 3H; 7-H3), 1.32 [s, 9H; C(CH3)3]. 13C NMR
(CDCl3, 25 °C): 133.2 (Cq, C2), 122.9 (Cq, C5), 112.6 (Cq, C3),
109.9 (CH, C4), 32.1 [Cq, C(CH3)3], 30.1 [C(CH3)3], 13.2 and 12.7
(each CH3, C-6 and C-7). IR (film): ν˜ 3490.2, 3416.4 (br) cm-1
(N-H). MS (70 eV, EI): m/z (%): 151 (35) [M]+, 136 (100), 70
(18), 61 (23). Anal. Calcd (%) for C10H17N (151.3): C 79.41, H
11.33, N 9.26. Found: C 79.43, H 11.30, N 9.24.
3
SCH2), 1.77 [1.73] (m, 2H; NCH2CH2), 1.21 [1.30] (t, J ) 7.4
3
[7.5] Hz, 3H; SCH2CH3), 0.99 [0.98] (t, J ) 7.4 [7.4] Hz, 3H;
NCH2CH2CH3).
2-tert-Butyl-5-methyl-3-propyl-1H-pyrrole (16d) and N-Ethyl-
2,2-dimethylthiopropionimidic Acid Ethyl Ester (14a) (from 8a).
Pentacarbonyl[1-(ethylthio)pentylidene]tungsten (8a) (454 mg, 1.00
mmol), N-ethyl-2,2-dimethylpropionimidoyl chloride (9a) (295 mg,
2.00 mmol), and triethylamine (101 mg, 1.00 mmol) were reacted
as described above to give compounds 16d (143 mg, 80%, Rf )
0.5 in n-pentane/dichloromethane, 4:1, yellowish oil) and 14a.
14a. See above at the synthesis of 16d for spectroscopic data.
3-Cyclohepta-2,4,6-trien-1-yl-5-methyl-2-phenyl-1H-pyrrole
(16g) and N-Ethylthiobenzimidic Acid Ethyl Ester (14b and
14b′). Pentacarbonyl[2-(cyclohepta-2,4,6-trien-1-yl)-1-(ethylthio)-
ethylidene]tungsten (8c) (502 mg, 1.00 mmol), N-ethylbenzimidoyl
chloride (9b) (335 mg, 2.00 mmol), and triethylamine (101 mg,
1.00 mmol) were reacted as described above to give compounds
1
16d. H NMR (400 MHz, CDCl3, 25 °C): δ 7.43 (s, br, 1H;
NH), 5.69 (d, br, 4J ) 2.8 Hz, 1H; 4-H), 2.48 (dd, 3J ) 7.8 and 8.3

Fischer Alkoxycarbene and Thiocarbene Complexes
Organometallics, Vol. 26, No. 20, 2007 4995
16g (175 mg, 71%, Rf ) 0.3 in n-pentane/dichloromethane, 4:1,
colorless crystals from n-pentane/dichloromethane, 4:1, at -20 °C,
mp 101 °C), 14b, and 14b′.
mmol), and triethylamine (101 mg, 1.00 mmol) were reacted as
described above to give compounds 16e (143 mg, 72%), 14b, and
14b′.
16e, 14b, and 14b′. See above at the synthesis of 16e for
spectroscopic data.
Pentacarbonyl[5-tert-butyl-2,2-dimethyl-4-propyl-2H-pyrrole-
N]tungsten (13k), 5-tert-Butyl-2,2-dimethyl-4-propyl-2H-pyrrole
(17k), and N-Isopropyl-2,2-dimethylthiopropionimidic Acid
Ethyl Ester (14c). Pentacarbonyl[1-(ethylthio)pentylidene]tungsten
(8a) (454 mg, 1.00 mmol), N-isopropyl-2,2-dimethylpropionimidoyl
chloride (9c) (323 mg, 2.00 mmol), and triethylamine (101 mg,
1.00 mmol) were reacted as described above to give compounds
13k, 17k, and 14c. They were not isolated, but characterized from
1H and 13C NMR spectra.
1
16g. H NMR (500 MHz, CDCl3, 25 °C): δ 7.82 (s, br, 1H;
NH), 7.30-7.14 (m, 5H; o-, m-, and p-H Ph), 6.68, 6.20, and 5.45
(each m, 2:2:2 H; from 2′-H to 7′-H), 6.12 (d, br, 4J ) 2.3 Hz, 1H;
4-H), 2.78 (t, br, J ) 5.4 Hz, 1H; 1′-H), 2.34 (s, 3H; 6-H3). 13C
3
NMR (CDCl3, 25 °C): 133.3 (Cq, i-C Ph), 130.8, 127.6, 123.8 (each
CH, 2:2:2 C; from C2′ to C7′), 128.6, 126.6, and 126.0 (each CH,
o-, m-, and p-C Ph), 128.2 (Cq, C5), 127.6 (Cq, C2), 123.4 (Cq,
C3), 106.6 (CH, C4), 37.3 (CH, C1′), 13.2 (CH3, C6). IR (film):
ν˜ 3421.9, 3371.0, br cm-1 (N-H). MS (70 eV, EI): m/z (%) 247
(100) [M]+, 170 (46), 127 (10), 57 (41). Anal. Calcd (%) for
C18H17N (247.3): C 87.41, H 6.93, N 5.66. Found: C 87.19, H
6.79, N 5.91.
1
4
13k. H NMR (300 MHz, CDCl3, 25 °C): δ 7.43 (t, br, J )
14b and 14b′. See above at the synthesis of 16e for spectroscopic
data.
3
4
1.7 Hz, 1H; 3-H), 2.53 (dt, J ) 7.8 and J ) 1.7 Hz, 2H; 6-H2),
1.71 (m, 2H; 7-H2), 1.70 (s, 6H; 2CH3), 1.54 [s, 9H; C(CH3)3],
1.06 (t, 3J ) 7.3 Hz, 3H; 8-H3). 13C NMR (CDCl3, 25 °C): 202.0
and 199.3 [Cq, 1:4 C; trans- and cis-CO of W(CO)5], 189.4 (Cq,
C5), 161.9 (CH, C3), 138.5 (Cq, C4), 73.5 (Cq, C2), 37.3 [Cq,
C(CH3)3], 29.7 (CH2, C6), 27.5 [C(CH3)3], 21.6 (2CH3), 21.5 (CH2,
C7), 13.5 (CH3, C8).
3-[Tricarbonyl(2,4-cyclohexadien-1-yl)iron]-5-methyl-2-phen-
yl-1H-pyrrole (16h) and N-Ethylthiobenzimidic Acid Ethyl Ester
(14b and 14b′). Pentacarbonyl[1-(ethylthio)-2-{tricarbonyl(2,4-
cyclohexadien-1-yl)iron}ethylidene]tungsten (8d) (315 mg, 0.50
mmol), N-ethylbenzimidoyl chloride (9b) (168 mg, 1.00 mmol),
and triethylamine (51 mg, 0.50 mmol) were reacted as described
above to give compounds 16h (120 mg, 64%, Rf ) 0.3 in n-pentane/
dichloromethane, 4:1, yellow crystals from n-pentane/dichlo-
romethane, 4:1, at -20 °C, 4/1, 146-147 °C), 14b, and 14b′.
1
4
17k. H NMR (400 MHz, CDCl3, 25 °C): δ 6.81 (t, br, J )
3
4
1.7 Hz, 1H; 3-H), 2.38 (dt, J ) 7.7 and J ) 1.7 Hz, 2H; 6-H2),
1.59 (m, 2H; 7-H2), 1.28 [s, 9H; C(CH3)3], 1.23 (s, 6H; 2CH3),
0.99 (t, 3J ) 7.3 Hz, 3H; 8-H3). 13C NMR (CDCl3, 25 °C): 179.2
(Cq, C5), 155.9 (CH, C3), 139.4 (Cq, C4), 73.6 (Cq, C2), 35.6 [Cq,
C(CH3)3], 30.9 (CH2, C6), 28.5 [C(CH3)3], 23.6 (2CH3), 22.2 (CH2,
C7), 14.1 (CH3, C8).
16h. 1H NMR (400 MHz, C6D6, 25 °C): δ 6.77 (s, br, 1H; NH),
7.21-7.15 and 7.06 (each m, 4:1 H; o-, m-, and p-H Ph), 5.73 (d,
br, 4J ) 2.1 Hz, 1H; 4-H), 4.91 (m, 1H; 2′-H), 4.84 (m, 1H; 3′-H),
3.61 (dt, 3J ) 11.1 and 3.6 Hz, 1H; 5′-H), 2.98 (m, 1H; 4′-H), 2.71
(m, 1H; 1′-H), 2.13 (m, 1H; 6′endo-H), 1.89 (d, br, 4J ) 0.4 Hz, 3H;
6-H3), 1.56 (m, 1H; 6′exo-H). 13C NMR (CDCl3, 25 °C): 133.3 (Cq,
i-C Ph), 128.8, 126.9, and 126.3 (each CH, o-, m-, and p-C Ph),
128.0, 127.1, and 126.4 (each Cq, C5, C2, and C3), 105.9 (CH,
C4), 86.0 (CH, C2′), 84.4 (CH, C3′), 68.0 (CH, C4′), 60.7 (CH,
C1′), 34.7 (CH, C5′), 34.0 (CH2, C6′), 13.1 (CH3, C6). IR
(cyclohexane): ν˜ 2045.2 (90), 1977.7 (100), 1972.0 (80) cm-1 (Ct
O). IR (film): ν˜ 3462.3, 3419.6, br, 3376.4, br cm-1 (N-H). MS
(70 eV, EI): m/z (%): 375 (14) [M]+, 319 (21), 289 (100), 233
(37), 213 (64), 157 (58), 134 (17). Anal. Calcd (%) for C20H17-
NO3Fe (375.2): C 64.02, H 4.57, N 3.73. Found: C 63.62, H 4.33,
N 3.48.
14c. 1H NMR (300 MHz, CDCl3, 25 °C): δ 4.08 (sep, 3J ) 6.2
Hz, 1H; NCH), 2.73 (q, 3J ) 7.5 Hz, 2H; SCH2), 1.25 (t, 3J ) 7.5
3
Hz, 3H; SCH2CH3), 1.18 [s, 9H; C(CH3)3], 1.12 [d, J ) 6.2 Hz,
6H; NCH(CH3)2].
Pentacarbonyl[5-tert-butyl-2,2,4-trimethyl-2H-pyrrole-N]tung-
sten (13l), 5-tert-Butyl-2,2,4-trimethyl-2H-pyrrole (17l), and
N-Isopropyl-2,2-dimethylthiopropionimidic Acid Ethyl Ester
(14c). Pentacarbonyl[1-(ethylthio)propylidene]tungsten (8b) (426
mg, 1.00 mmol), N-isopropyl-2,2-dimethylpropionimidoyl chloride
(9c) (323 mg, 2.00 mmol), and triethylamine (101 mg, 1.00 mmol)
were reacted as described above to give compounds 13l, 17l, and
14c. They are not isolated but characterized from 1H and 13C NMR
spectra.
14b and 14b′. See above at the synthesis of 16e for spectroscopic
data.
1
2-tert-Butyl-5-methyl-3-propyl-1H-pyrrole (16d) and N-Ethyl-
2,2-dimethylthiopropionimidic Acid Ethyl Ester (14a) (from 8e).
Pentacarbonyl[1-(ethylthio)pentylidene]chromium (8e) (322 mg,
1.00 mmol), N-ethyl-2,2-dimethylpropionimidoyl chloride (9a) (295
mg, 2.00 mmol), and triethylamine (101 mg, 1.00 mmol) were
reacted as described above to give compounds 16d (146 mg, 82%)
and 14a.
16d and 14a. See above at the synthesis of 16d for spectroscopic
data.
5-Methyl-2-phenyl-3-propyl-1H-pyrrole (16e) and N-Ethylth-
iobenzimidic Acid Ethyl Ester (14b and 14b′) (from 8e).
Pentacarbonyl[1-(ethylthio)pentylidene]chromium (8e) (322 mg,
1.00 mmol), N-ethylbenzimidoyl chloride (9b) (335 mg, 2.00
13l. H NMR (300 MHz, CDCl3, 25 °C): δ 7.49 (s, br, 1H;
3-H), 2.30 (s, 3H; 6-H3), 1.70 (s, 6H; 2CH3), 1.54 [s, 9H; C(CH3)3].
13C NMR (CDCl3, 25 °C): 201.7 and 199.0 [Cq, 1:4 C; trans- and
cis-CO of W(CO)5], 189.0 (Cq, C5), 163.6 (CH, C3), 133.1 (Cq,
C4), 73.0 (Cq, C2), 36.8 [Cq, C(CH3)3], 27.1 [C(CH3)3], 21.4 (2CH3),
14.3 (CH3, C6).
1
4
17l. H NMR (400 MHz, CDCl3, 25 °C): δ 6.86 (q, br, J )
1.5 Hz, 1H; 3-H), 2.12 (d, br, 4J ) 1.5 Hz, 3H; 6-H3), 1.32 [s, 9H;
C(CH3)3], 1.29 (s, 6H; 2CH3). 13C NMR (CDCl3, 25 °C): 180.5
(Cq, C5), 158.8 (CH, C3), 134.0 (Cq, C4), 73.3 (Cq, C2), 35.6 [Cq,
C(CH3)3], 28.1 [C(CH3)3], 23.2 (2CH3), 15.0 (CH3, C6).
14c. See above at the synthesis of 13k and 17k for spectroscopic
data.

4996 Organometallics, Vol. 26, No. 20, 2007
Karatas et al.
N-Benzyl-R,R-d2-benzimidoyl Chloride (D2-9e). To N-benzyl-
R,R-d2-benzamide (1.3 g, 6.1 mmol) in a 25 mL flask fitted with
a reflux condenser was added thionyl chloride (0.80 g, 6.7 mmol)
at room temperature. Then the reaction mixture was heated
approximately 1 h at 100 °C after melting of the amide. After the
reaction was completed, the flask was cooled to room temperature
and the reaction mixture was washed with n-pentane. Finally, the
solvent was removed under reduced pressure and the obtained
imidoyl chloride D2-9e was used directly without further purification
(1.1 g, 79%, colorless liquid).
automatically according to the procedure implemented in Gaussian
03. The TSs were located with the QST3 procedure in which in
addition to the structures of the specific reactant and product an
initial TS structure is required as input.34 The initial TS structures
were located with the help of constrained geometry optimizations
by freezing the appropriate reaction coordinate. All optimized
structures correspond to fully converged geometries with gradients
and displacements below the thresholds implemented in the
Gaussian 03 program. The geometry optimizations of the reactants,
transition states, and products were followed by vibrational
frequency analyses. Harmonic frequencies were computed analyti-
cally and used without scaling. Reaction enthalpies ∆H were
calculated from the differences between the total electronic energies
(Eelec), zero-point-vibrational-energies (ZPVE), and thermal energies
(Eth) of the products or TS with respect to the reactants and corrected
for the volume work [∆(PV)] term (eq 1).35
1
D2-9e. H NMR (300 MHz, CDCl3, 25 °C): δ 8.05 and 7.33
(each m, 2:8 H; o-, m-, and p-H 2Ph). 13C NMR (CDCl3, 25 °C):
δ 143.4 (Cq, CdN), 138.0 and 135.6 (each Cq, each i-C Ph), 131.4,
129.1 128.5, 128.3, 127.8, and 127.1 (each CH, o-, m-, and p-C
2Ph), 57.0 (quintet, CD2). MS (70 eV, EI): m/z (%) 231 (0.2) [M]+,
196 (45) [M - Cl]+, 93 (100). Anal. Calcd (%) for C14H10D2ClN
(231.1): C 72.70, H 6.10, N 6.06. Found: C 72.35, H 5.88, N
6.27.
∆H ) ∆Eelec + ∆ZPVE + ∆Eth + ∆(PV)
(1)
4-Deutero-2,5-diphenyl-3-propyl-1H-pyrrole ((4-D)-16e). Pen-
tacarbonyl[1-(ethylthio)pentylidene]tungsten (8a) (123 mg, 0.27
mmol), N-benzyl-R,R-d2-benzimidoyl chloride (D2-9e) (125 mg,
0.54 mmol), and triethylamine (27 mg, 0.27 mmol) were reacted
as described above. After the removal of ether, the residue was
washed with n-pentane (3 × 10 mL) and the solvent was removed
again under reduced pressure. The immediate measurement of the
1H NMR spectrum of the n-pentane-soluble part indicated the
formation of pyrrole (4-D)-16e. On the other hand, pyrrole (4-D)-
16e, N-benzyl-R,R-d2-benzamide, and the triethylammonium salt
were detected in the spectrum of the residue. The compound (4-
D)-16e was analyzed from the latter spectrum. The compound was
not purified further by chromatography in order to prevent proton
exchange in the column.
The thermal energy contributions (Eth) correspond to the sum of
the changes in translational, rotational, and vibrational energies
when going from 0 to 298.13 K. For the volume work term we
assume ideal gas behavior, and thus it is equal to ∆nRT.35
Acknowledgment. I.H.-K. thanks the SFB 424 (“Molekulare
Orientierung als Funktionskriterium in Chemischen Systemen”)
for financial support and Dr. Christian Mu¨ck-Lichtenfeld for
technical support.
Supporting Information Available: (a) Selected optimized
parameters and number of imaginary frequencies of the stationary
structures for the MDPM rearrangement and the R-cyclization
reactions calculated with the TZVP (Tables S1 and S3) and the
LANL2DZ basis sets (Table S2); (b) BP86/LANL2DZ potential
energy profiles for the MDPM rearrangements of the oxo and thio
complexes; (c) BP86/LANL2DZ potential energy profiles for the
hydride migration in 10h and 11o; (d) BP86/TZVP potential energy
profile for the hydrogen transfer in 15m to give 19m. This material
is available free of charge via the Internet at http://pubs.acs.org.
1
(4-D)-16e. H NMR (400 MHz, CDCl3, 25 °C): δ 8.48 (s, br,
1H; NH), 2.63 (m, 2H; 6-H), 1.69 (m, 2H; 7-H), 0.99 (t, 3J ) 7.3
Hz, 3H; 8-H).24
Computational Details. All calculations were carried out with
the density functional theory, DFT.25 They employed the exchange
functional of Becke26 in conjunction with the correlation functional
of Perdew27 as well as the resolution of the identity (RI) approxima-
tion28 for the fitting of the Coulomb potential (RI-BP86). The RI
approximation largely increases the performance of pure DFT
treatments without significantly decreasing accuracy. The geom-
etries of the reactants, transition states (TS), and products were
optimized with two basis sets denoted as BS1 and BS2 by using
the Gaussian 03 program.29 In BS1 the core electrons of sulfur and
tungsten (small-core) were approximated by effective core potentials
(ECP) of Hay and Wadt and the valence electrons described by
the associated double-ú basis.30 For H, C, N, and O atoms an all-
electron D95V basis set was used.31 The basis set BS1 is known
by its acronym LANL2DZ. In BS2 the small-core electrons of
tungsten were approximated by the quasi-relativistic ECP from the
Stuttgart group32 and the valence electrons described by a TZVP
basis: (7s6p5d)/[6s3p3d]. All-electron TZVP basis sets were used
for the remaining atoms; S: (14s10p)/[5s5p], C, N, O: (11s6p1d)/
[5s3p1d], H: (5s1p)/[3s1p]. The TZVP basis sets and ECP were
taken from the TURBOMOLE basis set library33 and introduced
into Gaussian input with the Gen and Pseudo)read keywords. The
auxiliary basis sets for the RI approximation were generated
OM700391T
(29) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Oritz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin. R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzales, C.; Pople, J. A. Gaussian 03 Rev.
C01; Gaussian, Inc.: Wallingford, CT, 2004.
(30) (a) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284-298. (b)
Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299-310.
(31) Dunning, T. H., Jr.; Hay, P. J. In Modern Theoretical Chemistry;
Schaefer, H. F., III, Ed.; Plenum: New York, 1976; Vol. 3, pp 1-28.
(32) Andrae, D.; Ha¨ussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Theor.
Chim. Acta 1990, 77, 123-141.
(33) The basis sets are available from the TURBOMOLE homepage
http://www.turbomole.com via the FTP Server Button in the subdirectory
basen.
1
(24) The phenyl signals in the H NMR spectrum of the pyrrole (4-D)-
16e overlap with the signals of N-benzyl-R,R-d2-benzamide (at 7.53-7.19
ppm), which is generated by hydrolysis of the imidoyl chloride D2-9e.
(25) (a) Parr, R. G.; Yang, W. Density Functional Theory of Atoms and
Molecules; Oxford University Press: New York, 1989. (b) Koch, W.;
Holthausen, M. C. A Chemist’s Guide to Density Functional Theory; Wiley-
VCH: Weinheim, 2000.
(26) Becke, A. D. Phys. ReV. A 1988, 38, 3098-3100.
(34) (a) Peng, C.; Schlegel, H. B. Isr. J. Chem. 1994, 33, 449-454. (b)
Peng, C.; Ayala, P. Y.; Schlegel, H. B.; Frisch, M. J. J. Comput. Chem.
1996, 17, 49-56.
(35) (a) Del Bene, J. E. In Molecular Structure and Energetics: Bonding
Models; Liebmann, J. F., Greenberg, A., Eds.; VCH: Deerfield Beach, FL,
1986; Vol. 1, pp 319-348. (b) Pitzer, K. S. Quantum Chemistry; Prentice
Hall: Englewood Cliffs, NJ, 1961.
(27) Perdew, J. P. Phys. ReV. B 1986, 33, 8822-8824.
(28) (a) Dunlap, B. I. J. Chem. Phys. 1983, 78, 3140-3142. (b) Eichkorn,
K.; Treutler, O.; O¨ hm, H.; Ha¨ser, M.; Ahlrichs, R. Chem. Phys. Lett. 1995,
242, 652-660. (c) Treutler, O.; Ahlrichs, R. J. Chem. Phys. 1995, 102,
346-354. (d) Dunlap, B. I. J. Mol. Struct. (THEOCHEM) 2000, 529, 37-
40. (e) Dunlap, B. I. Phys. Chem. Chem. Phys. 2000, 2, 2113-2116.