Nucleophilic addition to the η2-alkyne ligand in [CpFe(CO)2(η2-R-C≡C-R)]+. Dependence of the alkenyl product stereochemistry on the basicity of the nucleophile

Article abstract of DOI:10.1021/om010095t

Reaction of the cationic η²-alkyne iron complex, [Fp(η²-Ph-C≡CPh)]BF₄ (1) [Fp = (η⁵-C₅H₅)Fe(CO)₂], with various O-, N-, and C-nucleophiles afforded products containing the Ph-C=C

Full text of DOI:10.1021/om010095t

2736
Organometallics 2001, 20, 2736-2750
Nu cleop h ilic Ad d ition to th e η2-Alk yn e Liga n d in
[Cp F e(CO)2(η2-R-CtC-R)]+. Dep en d en ce of th e Alk en yl
P r od u ct Ster eoch em istr y on th e Ba sicity of th e
Nu cleop h ile
Munetaka Akita,* Satoshi Kakuta, Shuichiro Sugimoto, Masako Terada,
Masako Tanaka, and Yoshihiko Moro-oka
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503, J apan
Received February 7, 2001
Reaction of the cationic η2-alkyne iron complex, [Fp(η2-Ph-CtCPh)]BF4 (1) [Fp ) (η5-C5H5)-
Fe(CO)2], with various O-, N-, and C-nucleophiles afforded products containing the Ph-Cd
C-Ph linkage. i.e., cis- (3) and trans-alkenyl complexes (4), Fp-C(Ph)dC(Ph)-Nu, and
metallacycles, Cp(CO)Fe-C(Ph)dC(Ph)-C(dO)-Nu [coordinated at dO (5) or Nu (6)].
Crystallographic determination of the configuration of the CdC moiety in 3 and 4 and
analysis of the product distribution revealed that basic nucleophiles bearing alkyl substit-
uents produced the cis-alkenyl complex (3) and/or the metallacycles (5, 6), whereas less basic
nucleophiles bearing aryl substituents afforded the trans-alkenyl complex (4). Correlation
between the product distribution and pKb values of the nucleophiles leads to the conclusions
that (1) products 3, 5, and 6 arise from acyl intermediates formed by initial nucleophilic
addition of basic nucleophiles at the CO ligand, (2) trans-alkenyl complexes 4 result from
addition of less basic nucleophiles to the η2-alkyne ligand from the exo-side, and (3) the
equilibrium of the CO addition governed by the basicity of the nucleophile is the key step of
the diversity of the stereochemistry of the alkenyl products. Reactions of 2-hexyne complex,
[Fp(η2-Et-CtC-Et)]BF4 (2), were also examined.
Sch em e 1
In tr od u ction
Nucleophilic addition to unsaturated substrates co-
ordinated to a transition metal center is involved as a
key step of various stoichiometric and catalytic trans-
formations of hydrocarbons mediated by organometallic
species.1 As for nucleophilic addition to η2-alkyne com-
plexes (Scheme 1),2,3 previous studies have led to the
conclusion that trans-alkenyl complexes are obtained via
addition from the side opposite of M when the metal
center is coordinatively saturated (path i),2 and contrary
to this, the reaction of coordinatively unsaturated
complexes may form cis-alkenyl complexes via initial
addition to M followed by migration to the alkyne ligand
(path ii),4 though the latter type of reactions similar to
hydrometalation and carbometalation5 has not been
studied in detail.
series of cationic η2-alkyne complexes, [CpFe(CO)(L)-
(η2-R-CtC-R′)]+ [L ) PR′′3, P(OR′′)3], with a variety
(3) Ru: (a) de Klerk-Engels, B.; Delis, J os G. P.; Vrieze, K.; Goubitz,
K.; Fraanje, J . Organometallics 1994, 13, 3269. Pd, Pt: (b) Cacchi, S.
J . Organomet. Chem. 1999, 576, 42. (c) Yamamoto, Y.; Radhakrishnan,
U. Chem. Soc. Rev. 1999, 28, 199. (d) Hewertson, W.; Taylor, I. C. J .
Chem. Soc. D 1970, 428. (e) Appleton, T. G.; Chisholm, M. H.; Clark,
H. C.; Yasufuku, K. J . Am. Chem. Soc. 1974, 96, 6600. (f) Maassarani,
F. Pfeffer, M.; Spencer, J .; Wehman, E. J . Organomet. Chem. 1994,
466, 265. (g) Dupont, J .; Casagrande, O. L., J r.; Aiub, A. C.; Beck, J .;
Hoerner, M.; Bortoluzzi, A. Polyhedron 1994, 13, 2583. (h) Dupont, J .;
Basso, N. R.; Meneghetti, M. R.; Konrath, R. A.; Burrow, R.; Horner,
M. Organometallics 1997, 16, 2386. Mo: (i) Davidson, J . L.; Murray,
I. E. P.; Preston, P. N.; Russo, Maria, V.; Manojlovic-Muir, L.; Muir,
K. W. J . Chem. Soc., Chem. Commun. 1981, 1059. (j) Davidson, J . L.;
Vasapollo, G.; Manojlovic-Muir, L.; Muir, K. W. J . Chem. Soc., Chem.
Commun. 1982, 1025. (k) Feng, S. G.; White, P. S.; Templeton, J . L.
J . Am. Chem. Soc. 1990, 112, 8192. Polymetallic compounds: (l) Aime,
S.; Deeming, A. J . J . Chem. Soc., Dalton Trans. 1983, 1807. (m)
Cherkas, A. A.; Carty, A. J .; Sappa, E.; Pellinghelli, M. A.; Tiripicchio,
A. Inorg. Chem. 1987, 26, 3201. (n) Breimair, J .; Steimann, M.; Wagner,
B.; Beck, W. Chem. Ber. 1990, 123, 7. (o) Cherkas, A. A.; Breckenridge,
S. M.; Carty, A. J . Polyhedron 1992, 11, 1075.
As a typical example of the trans-addition reaction,
the extensive work done by Reger and co-workers can
be raised (Scheme 2).2a They examined reactions of a
(1) Pearson, A. J . Metalloorganic Chemistry; Wiley-Interscience:
New York, 1985. Yamamoto, A. Organotransition Metal Chemistry;
Wiley-Interscience: New York, 1986. Collman, J . P.; Hegedus, L. S.;
Norton, J . R.; Finke, R. G. Principles and Applications of Organo-
transition Metal Chemistry; University Science Books: Mill Valley,
1987. Cornils, B.; Herrmann, W.; Applied Homogeneous Catalysis with
Organometallic Compounds (2 vols.); VCH: Oxford, 1996. Crabtree,
R. H. The Organometallic Chemistry of the Transition Metals, 3rd ed.;
Wiley-Interscience: New York, 2001.
(2) (a) Reger, D. L. Acc. Chem. Res. 1988, 21, 229, and references
therein. (b) Reger, D. L.; Belmore, K. A.; Atwood, J . L.; Hunter, W. E.
J . Am. Chem. Soc. 1983, 105, 5710. (c) Reger, D. L.; Klaeren, Stephen
A.; Babin, J . E.; Adams, R. D. Organometallics 1988, 7, 181.
10.1021/om010095t CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/23/2001

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2737
Sch em e 2
(PR′′3)]. To make clear these effects, nucleophilic addi-
tion reaction to a simple mononuclear η2-alkyne complex
containing the [CpFe(CO)2]+ (Fp+) fragment, [Fp+(η2-
Ph-CtC-Ph)]BF4 (1), was examined. As a result,
reaction with amines and an alkanethiolate produced
cis-alkenyl complexes, as we reported in the previous
communication (see also text),6e and we concluded that
point (ii) was the crucial factor that determined the
initial reaction site; in other words, initial addition to
CO might lead to cis-addition. However, further study
has revealed that reaction of 1 with various nucleophiles
do not always produce cis-alkenyl complexes. Herein we
disclose details of nucleophilic addition to cationic η2-
alkyne iron complexes, [Fp+(η2-Ph-CtC-Ph)]BF4 (1)
and [Fp+(η2-Et-CtC-Et)]BF4 (2), and the present
study reveals factors determining initial nucleophilic
addition sites (e.g., stereochemistry of the alkenyl
products), which are dependent on the basicity (nucleo-
philicity) of the nucleophiles.
Resu lts
of nucleophiles (Nu) giving trans-alkenyl complexes,
CpFe(CO)(L)-C(R)dC(R)-Nu. As a result of a system-
atic study with the aid of crystallographic structure
determination, the trans-addition rule (path i in Scheme
1) was established for the nucleophilic addition. The
only exception was addition to the Cp ring leading to
ring-substituted alkenyl complexes,2b but cis-addition
was not observed at all. However, configuration of tri-
and tetrasubstituted alkenes resulting from the nucleo-
philic addition cannot be determined definitely by
spectroscopic analysis alone. In later studies, therefore,
when the configuration cannot be determined by the
spectroscopic data, the trans-addition rule has been
applied to assign the configuration.
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
Ca tion ic η2-Alk yn e Ir on Com p lexes, [F p +(η2-P h -
CtC-P h )]BF 4 (1) a n d [F p +(η2-Et-CtC-Et)]BF 4
(2). The cationic iron complexes with diphenylacetylene
(1) and 3-hexyne ligand (2) used in the present study
were prepared by substitution reaction of the labile
precursor, [Fp+(isobutene)]BF4, with appropriate alkynes
according to the reported procedure.7 Their molecular
structures were determined by X-ray crystallography.
ORTEP views are shown in Figures 1 and 2, and
selected structural parameters are summarized in Table
1. Details will be discussed later.
Rea ction of [F p +(η2-P h -CtC-P h )]BF 4 (1) w ith
Nu cleop h iles w it h Alk yl Su b st it u en t s (H NR 2,
Na OMe, Na SR) Givin g cis-Alk en yl Com p lexes a n d /
or Meta lla cycles. Reaction of 1 with amines in CH2-
Cl2 afforded two types of products containing the Ph-
CdC-Ph linkage, i.e., Fp-alkenyl complex 3, showing
two ν(CO) vibrations, and/or metallacycle 5, showing
only one ν(CO) vibration (eq 1).8 In addition to these
products, Fp2 was occasionally formed as a minor
byproduct. The spectroscopic data of 3 (Tables S1 and
S2)9 are consistent with alkenyl complexes, Fp-C(Ph)d
C(Ph)-Nu, which arise from nucleophilic addition of
amines to the CtC moiety. Configuration of the CdC
We have been studying structure and reactivity of
cationic dinuclear bridging acetylide complexes, [Fp*2-
(µ-CtC-R)]BF4 [R ) H (I), Ph (II); Fp* ) (η5-C5Me5)-
Fe(CO)2], and it was found that they exhibited divergent
chemical properties depending on the substituent R.6
For example, they showed different reactivity toward
nucleophiles. Reaction of I resulted in deprotonation to
give the ethynediyl complex Fp*-CtC-Fp*,6c,k whereas
addition reaction was observed for II (Scheme 2).6c,d The
addition reaction, however, did not afford a dimetalated
alkene, which we expected on the basis of the trans-
addition rule, but the products with the acyl functional
group such as III, which should result from initial
nucleophilic addition to the CO ligand (path c) instead
of that to the η2-alkyne ligand (path a or b). The
different initial reaction sites [CO (II) vs CtC (Reger’s
system)] might be ascribed to (i) the alkyne substituent
(Fp*) in II, which would cause various types of influence
on the electronic properties of the alkyne moiety, and/
or (ii) the different auxiliary ligands [(CO)2 vs (CO)-
(6) (a) Akita, M.; Moro-oka, Y. Bull. Chem. Soc. J pn. 1995, 68, 420.
(b) Akita, M.; Terada, M.; Oyama, S.; Moro-oka, Y. Organometallics
1990, 9, 816. (c) Akita, M.; Terada, M.; Oyama, S.; Sugimoto, S.; Moro-
oka, Y. Organometallics 1991, 10, 1561. (d) Akita, M.; Terada, M.;
Moro-oka, Y. Organometallics 1991, 10, 2961. The reaction mechanism
was corrected in ref 6h. (e) Akita, M.; Kakuta, S.; Sugimoto, S.; Terada,
M.; Moro-oka, Y. J . Chem. Soc., Chem. Commun. 1992, 451. (f) Akita,
M.; Sugimoto, S.; Terada, M.; Moro-oka, Y. J . Organomet. Chem. 1993,
447, 103. (g) Akita, M.; Ishii, N.; Takabuchi, A.; Tanaka, M.; Moro-
oka, Y. Organometallics 1994, 13, 258. (h) Akita, M.; Takabuchi, A.;
Terada, M.; Ishii, N.; Tanaka, M.; Moro-oka, Y. Organometallics 1994,
13, 2516. (i) Terada, M.; Masaki, Y.; Tanaka, M.; Akita, M.; Moro-oka,
Y. J . Chem. Soc., Chem. Commun. 1995, 1611. (j) Akita, M.; Kato, S.;
Terada, M.; Masaki, Y.; Tanaka, M.; Moro-oka, Y. Organometallics
1997, 16, 2392. (k) Akita, M.; Chung, M.-C.; Sakurai, A.; Sugimoto,
S.; Terada, M.; Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16,
4882. (l) Akita, M.; Sugimoto, S.; Hirakawa, H.; Kato, S.; Terada, M.;
Tanaka, M.; Moro-oka, Y. Organometallics 2001, 20, in press. For
recent related works, see: (m) Akita, M.; Chung, M.-C.; Sakurai, A.;
Moro-oka, Y. J . Chem. Soc., Chem. Commun. 2000, 1285, and refer-
ences therein.
(4) Bottrill, M.; Green, M. J . Am. Chem. Soc. 1977, 99, 5795. Allen,
S. R.; Baker, P. K.; Barnes, S. G.; Bottrill, M.; Green, M.; Orpen, A. G.
J . Chem. Soc., Dalton Trans. 1983, 927.
(5) (a) Negishi, E. Pure Appl. Chem. 1981, 53, 2333. Negishi, E.;
Takahashi, T. J . Synth. Org. Chem. J pn. 1989, 47, 2. (b) Asao, N.;
Yamamoto, Y. Chem. Rev. 1993, 93, 2207. (c) Knochel, P. In Compre-
hensive Organometallic Chemistry II; Abel, E. W., Stone, F. G. A.,
Wilkinson, G., Eds.; Pergamon: Oxford, 1995; Vol. 11, p 159. (d)
Negishi, E.; Kondakov, D. Y. Chem. Soc. Rev. 1996, 25, 417. (e) Marek,
I.; Normant, J . F. Transition Met. Org. Synth. 1998, 1, 514. (f) Marek,
I.; Normant, J . F. In Metal-Catalyzed Cross-Coupling Reactions;
Diederich, F., Stang, P. J ., Eds.; Wiley-VCH: Weinheim, 1998; p 271.
(g) Asao, N.; Yamamoto, Y. Bull. Chem. Soc. J pn. 2000, 73, 1071.
(7) Samuels, S.-B.; Berryhill, S. R.; Rosenblum, M. J . Organomet.
Chem. 1979, 166, C9.

2738 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
F igu r e 1. Molecular structure of the cationic part of 1 drawn at the 30% probability level: (a) molecule 1; (b) molecule 2.
Ch a r t 1
1
by H NMR analysis of the reaction mixtures (entries
4, 5, and 7), the alkenyl complexes 3d ,g were assigned
to cis-structure 3. The other product 5, with a single
ν(CO) vibration and a deshielded 13C NMR signal (δC
220-230), was assigned to the metallacyclic structure,
which was confirmed for the ButNH (5c)9 and pyrroli-
dinyl derivatives (5f, Figure 4) by X-ray crystallography.
The deshielded 13C NMR signal should be ascribed to
the contribution of another resonance structure 5′,
containing the carbenic FedCR moiety (Chart 1).10 In
accord with this description, the Fe1-C1 distances
[1.947(4) Å (5c) and 1.946(7) Å (5f)] are substantially
shorter than those in the alkenyl complexes 3 and 4
obtained by this study [Fe-C: 1.989-2.103 Å], and the
C2-C3 lengths [1.463(6) (5c) and 1.465(8) Å (5f)] are
also shorter than the corresponding bond lengths in the
(8) (a) a , c-g, n -p , r , w : Lide, D. R., Ed. Handbook of Chemistry
and Physics, 76th ed.; CRC Press: Boca Raton, FL, 1995. (b) j, m , q, t:
bond of the NPri derivative (3e) was determined to be
Dean, J . A., Ed. Lange’s Handbook of Chemistry, 12th ed.; McGraw-
Hill: New York, 1985. (c) b, h , i: Riddick, J . A.; Bunger, W. B.; Sakano,
T. K. Organic Solvents: Physical Properties and Methods of Puri-
fication, 4th ed.; Wiley-Interscience: New York, 1986. (d) k : Yabroff,
D. L. Ind. Eng. Chem. 1940, 32, 258. (e) s: Birchall, J . M.; Haszeldin,
R. N. J . Chem. Soc. 1959, 3653. (f) u : Bordwell, F. G.; Anderson,
H. M. J . Am. Chem. Soc. 1953, 75, 6019. (g) Refs 8a,b,d,e, pKb
values in aqueous solutions; ref 8f, pKb value in 48% EtOH aqueous
solution.
2
cis as revealed by X-ray crystallography (Figure 3). The
structural parameters of 3e summarized in Table 2 fall
in the accepted ranges, with the exception of the slightly
bent Fe1-C4-O4 linkage [168(1)°]. This is presumably
due to interaction with the lone pair electrons of N1,
which is directed toward C4 with the separation of
2.69(1) Å. Because only one isomer each of the Fp-
C(Ph)dC(Ph)-Nu-type alkenyl complexes was detected
(9) See Supporting Information.
(10) Mann, B. F.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: New York, 1981.

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2739
Ta ble 1. Selected Str u ctu r a l P a r a m eter s for [F p +(η2-R-CtC-R)]BF 4 [R ) P h (1), Et (2)]
1 (Ph)
[CpFe(CO)[P(OPh)3](η2-Me-CtC-R)]+ a
molecule 1
molecule 2
2 (R ) Et)
R ) Me
R ) Ph
Interatomic Distances (in Å)
Fe1-C101
Fe1-C102
Fe1-C103
Fe1-C104
C101-C102
C101-C111
C102-C121
C103-O103
C104-O104
Fe1-C105-109
2.154(8)
Fe2-C201
2.16(1)
Fe1-C1
Fe1-C2
Fe1-C3
Fe1-C4
C1-C2
C1-C11
C2-C21
C3-O3
C4-O4
2.207(10)
2.165(7)
2.114(6)
1.796(8)
2.155(2)b
1.19(1)
1.47(1)
1.49(1)
1.12(1)
2.14(1)
2.146(9)
1.78(1)
2.162(2)b
1.21(1)
1.49(1)
1.44(1)
1.12(2)
2.116(9)
1.77(1)
1.79(1)
1.24(2)
1.44(1)
1.44(2)
1.15(2)
1.15(1)
Fe2-C202
Fe2-C203
Fe2-C204
C201-C202
C201-C211
C202-C221
C203-O203
C204-O204
2.20(1)
1.796(9)
1.79(1)
1.22(1)
1.45(1)
1.44(1)
1.12(1)
1.14(1)
2.20(1)
1.77(1)
1.77(1)
1.26(2)
1.50(2)
1.52(2)
1.13(1)
1.13(1)
2.02-2.10(2)
2.08-2.11(1) Fe2-C205-209
2.04-2.08(2) Fe1-C5-9
Bond Angles (in deg)
C101-Fe1-C102
Fe1-C101-C102
Fe1-C101-C111
C102-C101-C111 157.8(9)
Fe1-C102-C101
Fe1-C102-C121
33.9(4)
71.4(6)
130.6(7)
C201-Fe2-C202
Fe2-C201-C202
Fe2-C201-C211
C202-C201-C211 159(1)
Fe2-C202-C201
Fe2-C202-C221
32.4(3)
75.5(7)
125.0(6)
C1-Fe1-C2
Fe1-C1-C2
Fe1-C1-C11 125.9(8)
C2-C1-C11
Fe1-C2-C1
Fe1-C2-C21 123.1(7)
33.2(4)
73.0(6)
32.4(3)
32.8(4)
155(2)
161(1)
73.8(7)
157.7(7)
74.8(6)
132.3(6)
72.2(7)
126.7(8)
C101-C102-C121 152.3(9)
C201-C202-C221 169(1)
C1-C2-C21
Fe1-C3-O3
Fe1-C4-O4
163(1)
178.4(8)
177(1)
158.4(8)
175.3(7)
159(1)
175.9(8)
Fe1-C103-O103
177.9(8)
Fe2-C203-O203
Fe2-C204-O204
176(1)
176.1(8)
b
Fe1-C104-O104
176(1)
a
Corresponding parameters are shown. See ref 21. P-C distances.
Ta ble 2. Selected Str u ctu r a l P a r a m eter s for Alk en yl Com p lexes (3, 4, a n d 13) a n d Meta lla cycles (5 a n d 14)a
complexb
Nu (reagent)
C1-C2
Fe1-C1
C2-Nu
Fe1-C1-C2
C1-C2-Nu
3ec (cis)
NPri (HNPri
)
2
1.38(1)
1.30(1)
1.989(7)
2.024(8)
2.046(4)
2.031(2)
2.06(1)
2.021(3)
2.026(4)
2.059(8)
2.019(5)
2.034(3)
2.01(1)
1.45(1)
127.9(7)
127.5(6)
126.9(3)
125.5(2)
126.3(8)
128.6(2)
128.1(3)
129.2(8)
125.6(4)
126.1(2)
124(1)
115.7(3)
114.6(5)
128(1)
114.5(2)
d
120.7(9)
121.7(6)
124.7(3)
116.7(2)
118.7(9)
119.2(3)
119.9(4)
121.7(8)
117.6(4)
117.7(3)
125(2)
2
3k c (cis)
SBut (NaSBut)
1.790(7)
1.513(5)
1.447(3)
1.46(1)
1.429(3)
1.436(4)
1.812(8)
1.446(6)
1.451(4)
1.59(2)
3zc (cis)
C6H2But2OH (C6H3But2ONa)
OC6H4OPh-p (NaOC6H4OPh-p)
OC6H4Me-p (NaOC6H4Me-p)
OC6H4F-p (NaOC6H4F-p)
OC6F5 (NaOC6F5)
1.338(5)
1.331(3)
1.25(1)
1.330(4)
1.291(5)
1.244(9)
1.354(7)
1.312(4)
1.27(2)
4lc (trans)
4oc (trans)
4qc (trans)
4sc (trans)
4tc (trans)
4vc (trans)
4w c (trans)
4yc (trans)
5cc (trans)
5fc (cycle)
13fc (trans)
14ic (cycle)
a
SPh (NaSPh)
N3 (NaN3)
OC(dO)Ph (NaOC(dO)Ph)
CH2C(dO)Ph (CH2dC(OSiMe3)Ph)
NHBut (NH2But)
c-N(CH2)4 (pyrrolidine)
OC6H4Me-p (NaOC6H4Me-p)
SEt (NaSEt)
1.354(6)
1.359(8)
1.28(2)
1.947(4)
1.946(7)
2.15(2)
1.36(2)
118(2)
1.363(3)
1.938(7)
Bond lengths in Å and bond angles in deg. Structures are shown in parentheses. c Obtained from 1. Obtained from 2.
b
F igu r e 2. Molecular structure of the cationic part of 2 drawn at the 30% probability level.
acyclic dC-CO structure [cf. 1.499(7) Å for trans-Fp-
C(Ph)dC(Ph)-COOMe;11 1.478(3) Å for Z-Fp-C(Ph)d
CHCOOMe].6c
A remarkable change in the product distribution is
observed depending on the structure of amines, as can
be seen from eq 1. In general, primary amines tend
to produce metallacycle 5, whereas secondary amines
give cis-alkenyl complexes 3. Reaction with a compact
(11) Kakuta, S.; Akita, M. Unpublished results.

2740 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
F igu r e 3. Molecular structures of cis-alkenyl complexes 3e and 3k drawn at the 30% probability level.
F igu r e 4. Molecular structure of metallacycles 5f and 14i drawn at the 30% probability level.
cyclic secondary amine (pyrrolidine; entry 6), however,
produces the metallacycle 5f in contrast to those with
acyclic secondary amines mentioned above (entries 4,
5, and 7).
In the case of the reaction with ButNH2, a different
type of adduct 3c′ was obtained together with 5c (eq
2). X-ray crystallography of 3c′ revealed the cationic
F igu r e 5. Molecular structure of 3c′ drawn at the 30%
probability level.
atom (C1) is pyramidalized judging from the bond
angles around it [110.8(4)-118.2(5)°; sum 340.3°, aver-
age: 113.4°]. In accord with this structure, its IR
spectrum contains νNH (3261 cm-1), νCO (2021, 1969
iminium ion structure (Figure 5 and Table 3) resulting
from addition of H-NHBut across the CtC bond. The
C1-C2 length [1.453(7) Å] falls in the range of C(sp3)-
C(sp2) single bonds, and the sp3-hybridized R-carbon
1
cm-1), and νBF absorptions (1084 cm-1), and its H NMR

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2741
Ta ble 3. Selected Str u ctu r a l P a r a m eter s for 3c′
be explained in terms of a mechanism involving (1)
decoordination of the CdO group to form the coordina-
tively unsaturated species, (2) cis f trans isomerization
of the alkenyl moiety, (3) C-H activation of the Ph
group, and (4) reductive elimination, but no experimen-
tal support has been obtained. To our surprise, the
indenone derivative was formed only from the MeO
derivative 5h , and no analogous product was obtained
from the reactions with NaOEt and other nucleophiles
described in this paper.
Bond Lengths (in Å)
Fe1-C1
Fe1-C3
Fe1-C4
Fe1-C5-9
O3-C3
2.152(6)
1.749(9)
1.790(7)
2.058(8)-2.109(7)
1.144(8)
N1-C2
N1-C31
C1-C2
C1-C11
C2-C21
1.301(7)
1.515(8)
1.453(7)
1.510(7)
1.471(8)
O4-C4
1.118(7)
Bond Angles (in deg)
C1-Fe1-C3
C1-Fe1-C4
C3-Fe1-C4
C2-N1-C31
Fe1-C1-C2
Fe1-C1-C11
97.9(3)
93.3(3)
94.2(4)
135.2(6)
111.3(4)
110.8(4)
C2-C1-C11
118.2(5)
117.1(6)
120.5(6)
122.3(6)
175.6(8)
175.6(7)
N1-C2-C1
N1-C2-C21
C1-C2-C21
Fe1-C3-O3
Fe1-C4-O4
Reaction with alkanethiolates gave a mixture of three
products: alkenyl complex 3, metallacycle 5, and Fp2
(eq 1). Although a single isomer of the alkenyl complex
3 was detected by 1H NMR monitoring of reaction
mixtures, chromatographic separation caused isomer-
ization, giving a mixture of alkenyl complexes 3j,k and
4j,k . In the case of the reaction with NaSEt, Fp-SEt
was also isolated from the reaction mixture. The kinetic
product of the alkenyl complexes obtained by the
reaction with NaSBut proved to be the cis-isomer 3k as
revealed by X-ray crystallography (Figure 3). Although
the metallacycles 6j,k showed 13C NMR and IR features
similar to those of 5 [(1) deshielded CR signal and (2)
single ν(CO) vibration], the additional ν(CdO) vibration
observed around 1670 cm-1 led to the assignment to
another cyclic structure 6, where the highly polarizable
sulfur atom is coordinated to the iron center instead of
the CdO functional group as in 5.
spectrum contains two broad signals (δH 5.35, 10.70),
which are assigned to the R-CH and NH moieties,
respectively. The former assignment was made based
on a CH-HETCOR (COSY) spectrum,12 in which the δH
5.35 signal was correlated to the sp3-carbon signal at
δC 31.1 (d, J CH ) 128 Hz). The iminium salt 3c′ should
be formed via nucleophilic addition of ButNH2 followed
by H-transfer from N to the R-carbon atom in the
resulting ammonioalkenyl intermediate [Fp-C(Ph)d
C(Ph)-NH2But]+. To examine whether deprotonation of
the imminium species 3c′ leads to alkenyl complex 3 or
4, an isolated sample of 3c′ was treated with bases
stronger than ButNH2 such as NEt3 and 1,8-bis(dimethyl-
amino)naphthalene (proton sponge) (eq 3). As a result,
deprotonation of the NH moiety led to the formation of
unstable imine complex 3c′′ accompanying decomposed
organic compounds. Retention of the R-CH moiety was
supported by its NMR data [δH 4.03 (1H, s); δC 38.1 (d,
J ) 134 Hz)] close to those of 3c′, and the loss of the
NH proton is confirmed by (1) disappearance of the
spectral features due to the NH group (δH, νNH) and (2)
appearance of a νCdN vibration (1673 cm-1). Thus the
formation of 3c′ turned out to be an event independent
from formation of alkenyl complexes.
Thus reaction of 1 with N-, O-, and S-nucleophiles
bearing alkyl substituents afforded alkenyl complex 3
and metallacycles 5 and 6 containing the cis-Ph-Cd
C-Ph linkage, and trans-isomer 4 was not formed at
all. To our knowledge, this type of nucleophilic cis-
addition reaction to a coordinatively saturated η2-alkyne
complex has no precedent. To see the scope and limita-
tion of the present unusual cis-addition reaction, reac-
tions with various nucleophiles were next studied.
Rea ction of [F p +(η2-P h -CtC-P h )]BF 4 (1) w ith
Nu cleop h iles w ith Ar yl Su bstitu en ts (Na OAr , Na -
SAr ) Givin g tr a n s-Alk en yl Com p lexes a n d /or Met-
a lla cycles. As an extension of the above nucleophilic
addition reactions, reaction with nucleophiles bearing
aryl substituents was studied. Because reaction with
aniline derivatives did not afford the expected alkenyl
complex but substituted products such as [Fp(NH2Ph)]-
BF4, the substituent effect was examined in detail for
the O- and S-nucleophiles.
Nucleophilic addition of an alkoxide anion to 1
resulted in the selective formation of metallacycles 5h ,i,
which were characterized on the basis of a single ν(CO)
vibration and a deshielded CR signal as observed for 5f
1
(eq 1). No trace of alkenyl complex was detected by H
NMR experiments. Although reaction with KOBut was
also examined to see effects caused by a bulky substitu-
ent as observed for the reaction with amines, no adduct
but Fp2 was obtained as the sole organometallic product.
Let us note that metallacycle 5h 6e obtained by the
reaction with NaOMe decomposed during chromato-
graphic separation to give indenone derivative 5h ′,
which was characterized by spectroscopic and crystal-
lographic analyses (eq 4).9 In another experiment treat-
Reaction with various phenolate derivatives also
produced alkenyl complex 4 and/or metallacycle 5 (eq
5). Product distribution determined by 1H NMR is
summarized in the table in eq 5. In sharp contrast to
the cis-addition reaction with the alkyl-substituted
nucleophiles, the configuration of the CdC bond in 4
was trans, as revealed by X-ray crystallography of some
of the reaction products, 4l, 4o, 4q, and 4s. As a typical
example, the molecular structure of the p-methylphen-
oxy derivative 4o is shown in Figure 6, and ORTEP
views of the other products are included in Supporting
Information.
ment of an isolated sample of 5h with alumina (over-
night in CH2Cl2) gave 5h ′. The formation of 5h ′ could
Reaction with arenethiolates resulted in the exclusive
formation of alkenyl complexes 4t,u , which were iso-
lated in good yields (eq 6), and the configuration of the
(12) Akitt, J . W.; Mann, B. E. NMR and Chemistry, An Introduction
to Modern NMR Spectroscopy, 4th ed.; Stanley Thorns: Cheltenham,
2000; p 290.

2742 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
F igu r e 6. Molecular structures of trans-alkenyl complexes 4o, 4t, and 13f drawn at the 30% probability level.
Reaction with inorganic and organic salts (NaN3,
PhCOONa, Me2NCS2Na) produced trans-alkenyl com-
plexes 4v,w ,x as sole organometallic products in moder-
ate yields (eq 7),13 and their trans-configuration has
been determined by X-ray crystallography.9
Carbon nucleophiles such as silyl enol ether and
allylstannane readily reacted with 1 to give adducts 4y
CdC moiety was trans, as indicated by the molecular
and 7a (Chart 2),13,14 although no reaction was observed
structure of 4t, which is shown in Figure 6.
with allylsilane (CH2dCHCH2SiMe3). Reaction with a
Rea ction of [F p +(η2-P h -C≡C-P h )]BF 4 (1) w ith
bulky phenolate, NaOC6H3-2,6-But , did not result in
2
Oth er Nu cleop h iles. To further examine the nucleo-
(13) Yields shown are isolated yields.
(14) Chromatographic purification gave 4z as an isomeric mixture
with 3z, but recrystallization of the mixture afforded 3z as single
philic addition reactions to 1, some more reactions with
inorganic and organic salts and carbon nucleophiles
were carried out.
crystals.

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2743
Ch a r t 2
ready reported for the related system, ([CpFe(CO)(L)-
(η2-R-CtC-R′)]+ + borohydrides, L ) PPh3, P(OPh)3;
R, R′ ) Me, Ph, COOMe), by Reger.2b
R ea ct ion of [F p +(η2-E t -CtC-E t )]BF 4 (2) w it h
Nu cleop h iles. Comparative study of the 3-hexyne
complex 2 was carried out in order to see the effect of
the substituents attached to the acetylene part. As a
result, considerably different reactivity was observed as
described below.
Reaction with amine resulted in the formation of
metallacycle 10, substituted product 11, and deproto-
nated product 12, depending on the structure of the
amine used (eq 8),13 and alkenyl complex was not
formed at all. Reaction with a less basic primary amine,
O-alkylation but C-alkylation at the sterically less
congested p-position to give 4z. Because, when left at
ambient temperature, 4z was converted to cis-isomer
3z, characterized crystallographically,9 4z was assigned
to the trans-isomer. Attempted addition reaction with
another O-nucleophile, NaOCH2CF3, resulted in addi-
tion of the Cp functional group (9) in a low yield,
presumably coming from partial decomposition of the
Fp fragment. The configuration of 4y and 9 was
determined to be trans,9,15 whereas that of the oily allyl
complex 7a could not be determined crystallographi-
cally.
n-Butyllithium16 and diethyl sodiomalonate also re-
acted with 1, but replacement at the Cp ligand took
place to give the 1,2-diphenylethenyl complexes 8a ,b.17
Hydride addition with HSnMe3 gave the expected
alkenyl complex 7b . However, again because the
products 7b and 8a were oily, their configuration could
not be determined crystallographically. Complexes 8a ,b
should arise from the intramolecular H-transfer in the
(exo-η4-C5H5Nu)Fe(CO)2(η2-Ph-CtCPh) intermediate
formed by addition to the Cp ring from the exo-side, and
therefore, their configuration was tentatively assigned
to the cis-structure. Similar hydride transfer was al-
NH2Pri, afforded a mixture of metallacycle 10a and
amine complex 11a .9,18 The former product was readily
characterized by comparison with the Ph derivatives 5
[single ν(CO) and deshielded δC(CR)]. In the case of the
reaction with cyclic secondary amines, HN(CH2)n (n )
4, 5), amine complexes 11b,c9,18 were formed as the sole
isolable organometallic products in quantitative yields.
Formation of 11 from 2 indicates that the 2-hexyne
ligand in 2 is more weakly bound to the iron center than
the Ph-CtC-Ph ligand in 1 due to the less effective
back-donation to the alkyl-substituted acetylene. In
contrast to these reactions, basic amines such as NHPri
2
and NEt3 gave oily allenyl complex 12 resulting from
deprotonation of a propargyl hydrogen atom. Complex
12 was characterized on the basis of (1) the presence of
only one ethyl group, (2) appearance of the methyl
signals, and, above all, (3) the three carbon signals
assignable to the allenyl part (δC 76.1, 87.9, 200.3).19
In the case of the reaction with oxygen nucleophiles,
the alkoxide gave metallacycle 10d , whereas aryloxide
and benzoate produced alkenyl complexes 13e-h (eq
9). The structure of the p-methylphenoxy derivative 13f
was confirmed by X-ray crystallography (Figure 6), and
the configuration of the benzoate adduct 13h was
tentatively assigned as trans on the basis of the con-
figuration of the reaction product of 1 (4w ).
(15) The trans configuration of 4x and 9 was also confirmed by X-ray
crystallography, but their structures could not be refined satisfactorily
due to the low quality of crystals. Cell parameters for 4x: monoclinic;
a ) 17.569(4) Å, b ) 6.857(2) Å, c ) 22.30(1) Å, â ) 108.77(2)°,
V ) 2543(1) Å3. 9: monoclinic; a ) 8.318(3) Å, b ) 17.656(3) Å,
c ) 14.470(3) Å, â ) 103.15(2)°, V ) 2069(2) Å3.
As a typical example of S-nucleophile, reaction with
NaSEt was examined (eq 10). Of the four reaction
(16) Reaction with n-BuLi was carried out in THF.
(17) Spectral data for 8a ,b : 8a : δH (CDCl3) 0.89 (3H, t, CH3),
1.2-1.7 (4H, m, (CH2)2), 2.21 (2H, t, CH2), 4.57 (2H, m, η5-C5H4),
4.68 (2H, m, η5-C5H4), 6.62-7.55 (11H, m, Ph and dCH); δC (CDCl3)
13.8 (q, J ) 123, CH3), 22.3, 27.4, 32.7 (t × 3, J ) 125-128, CH2),
85.2, 86.2 (d × 2, J ) 175, CH in η5-C5H4), 107.1 (s, η5-C5H4), 124.1,
124.6, 125.3, 127.7, 127.9, 128.3, 128.5, 131.6 (d × 8, Ph), 139.2
(d, J ) 153, dCH), 139.3, 152.4, 156.1 (s × 3, ipso-Ph and dC). 8b:
δH (CDCl3) 1.29 (6H, t, CH3), 4.20 (4H, q, CH2), 4.76, 5.09 (2H × 2,
s × 2, C5H4), 6.2-7.8 (11H, m, Ar); δC (CDCl3) 13.9 (q, J ) 127 Hz,
CH2CH3), 50.6 (d, J ) 133 Hz, CH(COOEt)2), 62.2 (t, J ) 151 Hz,
OCH2), 86.0 (d, J ) 180 Hz, C5H4), 88.1 (d, J ) 183 Hz, C5H4), 94.3
(s, C5H4), 124.4, 124.6, 125.3, 127.6, 128.6, 139.1, 150.2 (Ph), 139.8
(d, J ) 154 Hz, Câ), 155.5 (d, J ) 8 Hz, CR), 166.6 (s, CdO), 215.1
(s, CO).
(18) Amine complexes 11 were characterized by comparison with
authentic samples prepared by treatment of [Fp(isobutene)]BF4 or
[Fp(THF)]BF4 with appropriate amines. Molecular structures of 11a ,b
were determined by X-ray crystallography. For details, see Supporting
Information. The amine complex 11 adopts a typical three-legged
piano-stool structure. Some pertinent structural parameters of 11a are
as follows: Fe1-N1 2.015(4) Å; Fe1-C4 1.785(6) Å; Fe-C5 1.780(6)
Å; Fe1-C6-10 2.061-2.093(6) Å; N1-Fe1-C4 91.0(2)°; N1-Fe1-C5
93.6(2)°; C4-Fe1-C5 93, 2(3)°. The six substituents attached to the
Fe and N atoms adopt a staggered conformation.
(19) Pretsch, P. D.; Seible, J .; Simon, W.; Clerc, T. Strukturaufkla¨-
lung Organischer Verbindungen, 2nd ed.; Springer: Berlin, 1981.

2744 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
Ch a r t 3
from the side views (Figure 1). In addition, the -Ct
C- linkage in molecule 1 is more twisted with respect
to the axis passing through the Fe atom and the
midpoint of the CtC part. As a result, the C121-126
ring is laid almost coplanar to the Cp ring so that the
C102 atom is located closer to the metal center. The Fe‚
‚‚Ct distances in molecule 1 are slightly shorter than
those in molecule 2. When the structural parameters
are compared with the P(OPh)3 complexes used in
Reger’s study, [CpFe(CO)[P(OPh)3](η2-Me-CtC-R)]-
PF6,21 no significant and systematic differences are
observed within the range of the experimental errors
(Table 1). Although the CpFe(CO)[P(OPh)3] fragment
is expected to cause elongation of the CtC distances
and shortening of the Fe‚‚C distances due to the more
effective back-donation compared to the Fp fragment,
the CtC distances in 1 [1.24(2), 1.22(1) Å] and Reger’s
complexes [1.19(1) Å (R ) Me); 1.21(1) Å (R ) Ph)] are
comparable and longer than free Ph-CtC-Ph [1.198-
(3) Å]22 only by 0.02-0.04 Å. The slightly longer CtC
length of the 3-hexyne complex (2) [1.26(2) Å] may be
ascribed to the electron-releasing character of the ethyl
substituent compared to the phenyl group in the other
complexes. The very similar bent back angles of the
alkyne ligands in the four complexes [1 22.2°, 27.7°
(molecule 1), 21°, 21° (molecule 2); 2 17°, 19°; [CpFe+-
(CO)[P(OPh)3](η2-Me-CtC-R)] R ) Me, 21.6°, 22.3°;
R ) Ph, 21°, 25°]21 are similar to those of Pt(II)-η2-
alkyne complexes [15°, 18°, (η2-But-CtC-Buy)PtCl2(H2-
NPh);23a 12.7°, 14.5°, (η2-Ph-CtC-Ph)Pt(C6F5)2]23b but
are substantially smaller than those in other η2-alkyne
complexes [>30°;24 cf. isoelectronic Cr(0) compound, (η6-
C6Me6)Cr(CO)2(η2-Ph-CtC-Ph), 29.7°, 30.9°].24b These
results indicate that back-donation to the η2-alkyne
ligands in 1 and 2 is not so effective.
products isolated, two were metallacyclic complexes 14i
and 15i, which were differentiated by the absence/
presence of a ν(CdO) vibration as discussed for the 5-
and 6-type structures of the Ph2C2 derivatives, and the
former complex 14i with a ν(CdO) absorption (1664
cm-1) was characterized by X-ray crystallography (Fig-
ure 4). The structural parameters associated with the
cyclic part are essentially the same as those of 5f as
compared in Table 2, indicating the contribution of the
zwitterionic carbenic structure 14i′ (Chart 3). The
alkenyl complex 16i could not be isolated in a pure form
due to its oily nature, and the cis-configuration was
tentatively assigned on the basis of the results of the
reaction with 1 (3j,k ) described above. In this case, too,
a substantial amount of the substituted product, Fp-
SEt,20 was obtained.
Thus replacement of the P(OPh)3 ligand by CO does
not cause significant change in the structure of the
cationic η2-alkyne iron complexes, and the small struc-
tural deformation of the alkyne ligands in these com-
plexes from free alkyne indicates the rather weak
interaction with the metal center in the [CpFe(CO)(L)-
(η2-alkyne)]+-type cationic alkyne complexes. In accord
with this consideration, products resulting from alkyne
ligand dissociation are occasionally formed as described
above.
Discu ssion
Molecu lar Str u ctu r es of Cation ic η2-Alkyn e Com -
p lexes (1, 2), Alk en yl Com p lexes (3, 4, 13), a n d
Meta lla cycles (5, 14). A unit cell of the Ph-CtC-Ph
complex (1) contains two crystallographically indepen-
dent molecules with essentially the same geometry, but
the relative arrangements of the Ph substituents are
different. The phenyl rings in molecule 1 are laid
essentially coplanar with respect to the Fe1-C101-
C102 triangle, whereas those in molecule 2 are laid
almost perpendicular to the triangle, as can be seen
(21) Reger, D. L.; Klaeren, S. A.; Lebioda, L. Organometallics 1988,
7, 189.
(22) Mavridis, A.; Moustakali-Mavridis, I. Acta Crystallogr. Sect. B
1977, B33, 3612.
(23) (a) Davies, G. R.; Hewertson, D. W.; Mais, R. H. B.; Owston, P.
G. J . Chem. Soc. (A) 1970, 1873. (b) Uso´n, R.; Fornie´s, J .; Toma´s, M.;
Menjo´n, B.; Fortn˜o, C.; Welch, A. J .; Smith, D. E. J . Chem. Soc., Dalton
Trans. 1993, 275.
(24) (a) Cappelle, B.: Dartiguenave, M.; Dartiguenave, Y.; Beau-
champ, A. L. J . Am. Chem. Soc. 1983, 105, 4662. (b) Bartlett, I. M.;
Connelly, N. G.; Orpen, A. G.; Quayle, M. J .; Rankin, J . C. J . Chem.
Soc., Chem. Commun. 1996, 2583. Davies, G.; Hewertson, W.; Mais,
R. H. B.; Owston, P. G.; Patel, C. G. J . Chem. Soc. (A) 1970, 1873.
Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B.; Fortunp, C. J . Chem.
Soc., Dalton Trans. 1993, 275.
(20) Repeated recrystallization of Fp-SEt gave the decarbonylated
dimer complex trans-[CpFe(CO)(µ-SEt)]2, 17, which was characterized
crystallographically (Table 4).9 Crystal structure of the cis-isomer was
already reported. Parpiev, N. A.; Toshev, M. T.; Dustov, Kh. B.;
Aleksandrov, G. G.; Alekseeva, S. P.; Nekhaev, A. I. Dokl. Akad.
Uzbekskol. SSR 1988, 43.

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2745
Sch em e 3
In accord with the discussion on the solid-state
structure, the 13C NMR signals of the alkyne carbon
atoms are observed around 50 ppm [δC 58.0 (1), 50.3
(2); [CpFe+(CO)[P(OPh)3](η2-Me-CtC-R)] 46.4 (R )
Me), 51.5, 57.8 (R ) Ph)] upfield compared with that of
free Ph-CtC-Ph [δC 89.5].10
b),1 from which two pathways are feasible. The nucleo-
phile part in E still has lone pair electrons, which may
attack the alkyne carbon atom from the inner side to
give the cis-alkenyl complexes B (path c).26 Migration
of the whole acyl group would give the coordinatively
unsaturated species F , and subsequent coordination of
either the acyl oxygen atom or the nucleophile part
(path e) furnishes the metallacyclic products, C or D,
respectively. A third mechanism operates in some cases.
Dissociation of the Ph-CtC-Ph ligand from E (path
f) followed by retromigratory insertion of the nucleophile
part leads to the formation of Fp-Nu H, which may be
further converted to Fp2 via Fe-Nu homolysis or
â-hydride elimination. Fp2 may be also formed by direct
electron transfer from the nucleophile to the cationic
η2-alkyne complex (1 and 2). Elimination of the η2-
alkyne ligand from the resulting 19e species releases
the 17e radical species (Fp•),27 dimerization of which
leads to Fp2.
Many precedents have been reported for the formation
of the metallacyclic product via an (η1-acyl)(η2-alkyne)
intermediate like E (path d). Such a species can be
alternatively generated by CO insertion of an (alkyl)-
(carbonyl) complex induced by coordination of an alkyne
ligand or nucleophilic addition to a metal carbonyl
complex in the presence of alkyne, as we reported
previously.6c,28 In contrast to this pathway, path c
leading to the cis-alkenyl complex has few precedents.
Acyl group migration giving F (path d) may be inter-
preted in terms of a metathesis-like mechanism, when
the contribution of the oxycarbene structure [M+d
C(O-)-R] for the acyl species is taken into account.
In the case of the reaction with amines, formation of
products involves nucleophilic addition as well as de-
Alkenyl complexes 3, 4, and 13 adopt typical three-
legged piano-stool structures. No significant and sys-
tematic change of the structural parameters depending
on the Nu part (Table 2) can be observed. Although we
also attempted spectroscopic determination of the con-
figuration of the alkenyl moiety,2c no systematic differ-
ence between the cis- and trans-isomers was observed.25
Structural features of metallacycles 5 and 14 can be
rationalized in terms of contribution of the carbenic
structures such as 5′ and 14i′ as discussed above. While
the 1H and 13C NMR signals of the Cp ligand in
metallacycles appear in slightly lower field compared
to those of alkenyl complexes (Table S1 and S2), they
were readily differentiated by the number of νCO ab-
sorptions [1 (metallacycle) vs 2 (alkenyl complexes)] as
discussed above.
Rea ction Mech a n ism s. Reaction of the cationic iron
η2-alkyne complexes 1 and 2 affords various products
including alkenyl complexes [A (trans), 4, 13; B (cis), 3,
16] and metallacyclic compounds [C, 5, 14; D, 6, 15].
The formation of these products from anionic nucleo-
philes such as alkoxide, aryloxide, and alkane- and
arenethiolate is explained in terms of the mechanism
summarized in Scheme 3. Direct nucleophilic addition
to the alkyne carbon atom from the side opposite the
metal center with respect to the CtC part furnishes
trans-alkenyl complexes A (path a). The “trans-addition
rule” has been explained by this mechanism. On the
other hand, initial nucleophilic addition to the carbonyl
ligand would give rise to the acyl intermediate E (path
(26) The acetyl analogue of E, CpFe(CO)(Ph-CtC-Ph)-C(dO)-
Me, which has no lone pair electrons at the position corresponding to
Nu, can be generated by a different method.6c In this case, metallacycle
was formed exclusively due to the lack of lone pair electrons.
(27) Astruc, D. Chem. Rev. 1988, 88, 1189. Baird, M. C. Chem. Rev.
1988, 88, 1217.
(25) In some cases 13C NMR signals for the olefinic carbon atoms
could be assigned by careful examination of the coupling pattern, but
definite assignments were not always possible due to similar appear-
ance of the ipso-carbon signals of the phenyl rings.
(28) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1.

2746 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
Sch em e 4
protonation, and we propose the modified mechanism
shown in Scheme 4.29 Because no trans-alkenyl com-
plex 4 is obtained, the reaction does not follow path
a but path b, which involves initial attack of amine at
the CO ligand to give the ammonium intermediate E′
(path b).
Formation of the cis-alkenyl complex B should be
preceded by deprotonation (path g), because no lone pair
electrons are present on the nitrogen atom in the
ammonium intermediate E′. On the resulting acyl
intermediate E, the process analogous to Scheme 3
should lead to cis-alkenyl complexes B(3) and metalla-
cycles C(5) via the deprotonation-migration sequence.
F a ctor s Deter m in in g th e Regioch em istr y of Nu -
cleop h ilic Ad d ition . Taking into account the product
distribution and the reaction mechanisms, factors de-
termining the regiochemistry of the nucleophilic addi-
tion are considered.
summarized according to the pKb value of the nucleo-
philes (Figure 7).8,30 Fp2 is eliminated from the distribu-
tion, because it can be formed via various mechanisms
as discussed above. Let us note that products B, C, and
D arise from the initial nucleophilic addition to the CO
ligand (path b in Schemes 3 and 4) and that exo-attack
to the alkyne ligand leads to A (path a). Taking into
account this point, we can see a dramatic change in the
distribution around the pKb value of 4. In other words,
the reaction site switches depending on the basicity of
nucleophiles. Nucleophiles with a small pKb value (a
basic nucleophile) attack the carbonyl ligand to give the
olefinic products with the cis-Ph-CdC-Ph linkage (B,
C, and D), whereas nucleophiles with a larger pKb value
(a less basic nucleophile) attack the alkyne ligand from
the exo-side to give trans-alkenyl complex A.
The key point of this interpretation is competition
between the nucleophilic addition to the alkyne carbon
atom (path a) and CO (path b) (Schemes 3 and 4).31 The
former step (path a) is an irreversible one, and revers-
ibility of the latter process (path b) depends on the
basicity of nucleophiles. In the case of the reaction with
a stronger base the equilibrium of path b should be
shifted to the side of E, because formation of a neutral
species E is favored over the separation of highly
charged species: the cationic Fe-alkyne complexes (1,
2) and the anionic nucleophile. In this case, the reaction
may proceed virtually in an irreversible manner to give
B, C, and D with the cis-Ph-CdC-Ph linkage. On the
other hand, the equilibrium for a weak base is not
completely shifted to the side of acyl intermediate E,
and back reaction regenerating the starting complex
may be feasible. In the meantime, the irreversible exo-
attack (path a) would lead to the formation of trans-
alkenyl complex A.
The clear-cut dependence of the product distribution
on the substituents of nucleophiles (alkyl vs aryl)
suggests that basicity (nucleophilicity) of the nucleophile
may affect the reaction pathway. To consider the initial
nucleophilic addition sites, the distribution of three
types of olefinic products, trans-alkenyl complex (A), cis-
alkenyl complex (B), and metallacycles (C and D), is
(29) The result of the reaction with ButNH2, which afforded a
different type of product, 3c′ (eq 2), arouses suspicion that stereo-
chemistry of the alkenyl products 3 and 4 may not be retained in the
reaction system. The 3c′-type product J should be formed by H-
migration of the initially formed ammonioalkenyl intermediate I. C-C
rotation followed by deprotonation would cause stereochemical scram-
bling of the alkenyl moiety. At least the reaction with primary amine
(NR2 ) NHalkyl) does not follow such a reaction pathway, as revealed
by the deprotonation experiment (eq 3). Although the possibility cannot
be completely excluded for the reactions with secondary amines, we
inferred, from (1) formation of a single isomer of alkenyl complex (3/
4), (2) cis-stereochemistry observed for the reaction with NaSR, and
(3) the uniform dependence of the product distribution on pKB values
of nucleophiles (see below), that the H-induced stereochemical scram-
bling was not viable in the present reaction system.
(30) The result of NaOC6H4-Me-o (n ) was removed for clarity,
because small changes in the pKb value around 4 (differences be-
tween m and o <0.07) might cause a drastic change in the product
distribution. The removal did not cause any significant change of
the conclusion.
(31) Liu, L.-K.; Eke, U. B.; Mesubi, M. A. Organometallics 1995,
14, 3958.

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2747
F igu r e 7. Dependence of the product distribution of the nucleophilic addition reactions to 1 on pKb values of nucleophiles.
Ch a r t 4
Sch em e 5
the electronic and steric effects, the nucleophile should
attack the alkyne ligand from the exo-side to give trans-
alkenyl complexes.34
As for the selectivity between cis-alkenyl complex B
and metallacycle C/D, the result of the reaction with
amine (eq 1) suggests that steric bulkiness of the
nucleophile has some influence on the reaction path-
ways, but any decisive conclusion cannot be deduced
from the results obtained so far.
Con clu sion
The present study has revealed that (1) trans-addition
is not always the unique stereochemical outcome upon
nucleophilic addition to transition metal η2-alkyne
complexes bearing a π-acid such as CO and (2) stereo-
chemistry (product distribution) is dependent on the
reaction site (a vs b), which is governed by basicity
(nucleophilicity) of nucleophiles (Scheme 5). Because,
in many cases, carbonyl ligands are involved as auxil-
iary ligands of alkyne complexes, the stereochemistry
of alkenyl complexes obtained by nucleophilic addition
to η2-alkyne complexes should be examined carefully by
means of crystallography combined with various spec-
troscopic techniques. Inadvertent application of the
“trans-addition rule” leads to misinterpretation of the
stereochemistry of nucleophilic addition.
Thus two initial nucleophilic addition sites are fea-
sible for 1 and 2. This result is in sharp contrast to
Reger’s system, where addition to CO was not observed
at all and only trans-adducts were obtained. To see the
electronic state of the ligands attached to the iron center
in these systems, the electron density is calculated for
the simplified model complexes, [Fp+(η2-H-CtC-H)]
(K) and [CpFe+(CO)(PH3)(η2-H-CtC-H)] (L), by EHMO
(Chart 4).32 In the former species, the CO ligands are
the only positively charged sites, and the alkyne carbon
atoms are negatively charged. This result is consistent
with the preferred addition to CO as observed for the
Fp complexes 1 and 2. Introduction of the PH3 ligand
(L) causes increase of the electron density at both the
alkyne and CO moieties. The CO ligand is still the only
positively charged site in the molecule, and the alkyne
carbon atoms are more negatively charged than those
in the Fp complexes. The increase of the negative charge
at CO, however, should hinder the nucleophilic addition
to the CO ligand so as to drive the reaction to path a
(Scheme 3).33 The trans-addition observed for Reger’s
system, therefore, may be ascribed to the shift of the
CO addition equilibrium as well as the steric shielding
of the CO ligand by the bulky PR3 ligand. As a result of
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were carried
out under an inert atmosphere by using standard Schlenk tube
(33) We are grateful to the reviewer’s comment on the consideration
of the electronic effect. The reviewer also suggested to examine the
addition rates of strong and weak nucleophiles. We attempted kinetic
measurements of the nucleophilic addition at low temperatures, but
the reactions were too fast to be followed by NMR. No apparent
difference could be detected.
(34) Slippage of the alkyne ligand induced by the unsymmetrical
electronic structure of the PR3-substituted complexes may be another
possible reason for the trans-addition. Eisenstein, O.; Hoffmann, R. J .
Am. Chem. Soc. 1981, 104, 4308.
(32) CAChe 4.0, Oxford Molecular, 1997.

2748 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
techniques. Ether, hexanes (Na-K alloy), and CH2Cl2 (P2O5)
were treated with appropriate drying agents, distilled, and
stored under argon. The cationic iron η2-alkyne complexes 1
and 2 were prepared from the isobutene complex [Fp+(η2-CH2d
CMe2)]BF4,35 following the reported method.7 Sodium alkoxides
were prepared by careful addition of small pieces of Na metal
to a large amount of alcohol, and the volatiles were removed
from the resulting solution to give a colorless solid, which was
used without further purification. Sodium salts of phenol and
arenethiol derivatives were synthesized by treatment of ap-
propriate phenol or arenethiol with NaH (∼0.8 equiv) sus-
pended in ether followed by filtration, washing with ether, and
drying under reduced pressure. Other chemicals were pur-
chased and used as received. Chromatography was performed
on alumina [aluminum oxide, activity II-IV (Merck Art.
removed under reduced pressure. The residue was extracted
with CH2Cl2 and passed through an alumina plug. Addition
of hexanes and cooling at -30 °C afforded a solid containing
[Fp(ButNH2)]BF4. Further concentration of the supernatant
solution followed by addition of ether and cooling gave 3c′ (155
mg, 0.30 mmol, 24% yield) as brick red crystals. Chromato-
graphic separation of the supernatant solution gave 5c (brown
band, 53 mg, 0.12 mmol, 10% yield) and Fp2 (red-brown band).
3c′: δH (CDCl3) 1.24 (9H, s, But), 4.89 (5H, s, Cp), 5.35 (1H,
br, Fe-CH), 6.80-7.52 (10H, m, Ph), 10.20 (1H, br, NH); δC
(CDCl3) 30.9 (q, 128, CMe3), 31.1 (d, 128, CR), 60.9 (s, CMe3),
88.5 (d, 183, Cp), 125.5, 127.8, 128.0, 128.1, 129.2, 130.8, 131.1,
141.7 (Ph signals), 198.9 (s, CdN), 215.0, 215.6 (s × 2, CO).
IR (KBr): νNH 3261, νCO 2021, 1967, νBF 1084 cm-1. Anal. Calcd
for C25.5H27O2NClBF4Fe [3c′‚(CH2Cl2)1/2]: C, 54.94; H, 4.84;
N: 2.51. Found: C, 54.95; H, 5.05; N, 2.60.
1
1097)]. H and 13C NMR spectra were recorded on J EOL EX-
400 (1H, 400 MHz; 13C, 100 MHz) and J EOL EX-90 spectrom-
eters (1H, 90 MHz). Multiplicity, coupling constants (J C-H in
Hz), and assignments are shown in parentheses. Solvents for
NMR measurements containing 0.5% TMS were dried over
molecular sieves, degassed, distilled under reduced pressure,
and stored under Ar. IR spectra were obtained on a J ASCO
FT/IR 5300 spectrometer.
Spectroscopic and analytical data for new compounds not
shown below are summarized in Tables S1-S3 (Supporting
Information). Of more than 40 new compounds reported in this
paper, satisfactory results of elemental analysis were not
obtained for oily products, 3z, 6j, 8, 14i, and 15i.
R ea ct ion of [F p +(η2-R -CtC-R )]BF 4 (1 a n d 2) w it h
Nu cleop h iles. The reaction was carried out in CH2Cl2. The
product distribution was determined by 1H NMR experiments.
A typical procedure was as follows. To a stirred CH2Cl2 solution
of 1 cooled at -78 °C was added nucleophile (> 5 equiv), and
then the mixture was gradually warmed to room temperature.
After the completion of the reaction was checked by TLC
(disappearance of the orange spot of 1 at the origin), the
volatiles were removed under reduced pressure. The products
were extracted with CH2Cl2, and the insoluble materials were
removed by filtration though an alumina plug. After the
volatiles were removed under reduced pressure, CDCl3 (0.4
mL) and an internal standard (anisole) was added to the
residue, and the product distribution was determined by
comparison of intensities of the Cp signals and the MeO signal
of anisole.
Tr ea tm en t of 3c′ w ith NEt3. To complex 3c′ (670 mg, 1.30
mmol) dissolved in CH2Cl2 (1.5 mL) was added NEt3 (0.24 mL,
1.69 mmol) with stirring. Addition of hexane and ether caused
precipitation of inorganic salts and Fp2. The supernatant
solution was passed through a Celite plug, and the volatiles
were removed under reduced pressure. The residue was
subjected to column chromatography and eluted with CH2Cl2/
hexane ) 1:3. The deep yellow band was collected, and 3c′′
(129 mg, 0.30 mmol, 18% yield) was obtained as a yellow solid
after evaporation. Because 3c′′ was not so stable, it was
subjected to spectroscopic analysis after extraction with ether,
filtration through an alumina plug, and evaporation. Because
repeated crystallization caused decomposition of 3c′′ to give
organic products [PhCH2C(dO)Ph and PhC(dO)NHBut], an
analytically pure sample of 3c′′ could not be obtained.
Rea ction of 1 w ith Na OMe. To a CH2Cl2 solution (25 mL)
of 1 (1.12 g, 2.53 mmol) cooled at -78 °C was added THF (60
mL) and then NaOMe (0.89 g, 16.5 mmol) with stirring. After
3 min the cooling bath was removed, and the resultant mixture
was stirred for 1 h at ambient temperature. The mixture
changed from orange to dark red and then black. After removal
of the volatiles, products were separated by column chroma-
tography and then preparative TLC. From dark brown and
yellow bands 5h (0.37 g, 0.79 mmol, 31% yield)6c and 5h ′ (100
mg, 0.38 mmol, 15% yield) were obtained, respectively. 5h ′:
δH (CDCl3) 3.81 (3H, s, OMe), 7.40, 7.42-7.57 (9H, m,
aromatic). δC (CDCl3) 52.1 (q, 148, OMe), 122.7 (dd, 166, 7),
123.8 (dd, 164, 7), 128.0 (dd, 158, 7), 129.1 (dt, 164, 7), 129.2
(dt (164, 7), 129.7 (dt, 167, 6), 133.8 (d, 7), 135.3 (d, 7), 138.6
(s); aromatic carbon atoms, 165.0 (s, CdO), 195.0 (s, COOMe).
IR (KBr): νCdO 1717 cm-1. Anal. Calcd for C17H12O3: C, 77.29;
H, 4.54. Found: C, 77.05; H, 4.52.
Rea ction of 1 w ith Na SBu t. To a THF solution (20 mL)
of NaSBut (1.04 g, 8.9 mmol) cooled at -78 °C was added
dropwise 1 (1.56 mg, 3.53 mmol) dissolved in THF (30 mL).
Then the cooling bath was removed, and the mixture was
gradually warmed to ambient temperature. During this period,
the solution color changed from orange to yellow green. After
the mixture was stirred for 1 h, the volatiles were removed
under reduced pressure. The residue was extracted with ether
and passed through an alumina plug to remove salts. Chro-
matographic separation (CH2Cl2/hexanes ) 1:10 to 1:7) gave
three organometallic products in the order 3k , 4k , and 6k .
Crystallization from hexanes gave orange 3k (185 mg, 0.42
mmol, 12% yield), yellow 4k (134 mg, 0.30 mmol, 9% yield),
and orange 6k (104 mg, 0.23 mmol, 7% yield) as microcrystals.
Anal. 3k : Calcd for C25H24O2SFe: C, 67.57; H, 5.44. Found:
C, 67.28; H, 5.34. 4k : Calcd for C25H24O2SFe: C, 67.57; H,
5.44. Found: C, 67.15; H, 5.34. 6k : Calcd for C25H24O2SFe:
C, 67.57; H, 5.44. Found: C, 67.15; H, 5.34.
In some cases, reaction was carried out in CD2Cl2, and the
product distribution was determined by 1H NMR after addition
of an internal standard (anisole).
Several typical experimental procedures for isolation of
products are described below in detail.
Rea ction of 1 w ith NHP r i2. To a CH2Cl2 solution (10 mL)
of 1 (223 mg, 0.51 mmol) cooled at -78 °C was added NHPri
2
(0.5 mL) slowly. Then the cooling bath was removed, and the
mixture was gradually warmed to ambient temperature.
During this period, the solution color changed from orange to
yellow green. After the mixture was stirred for 1 h, the
completion of the reaction was checked by TLC (disappearance
of the orange spot at the origin), and then the volatiles were
removed under reduced pressure. The residue was extracted
with hexanes and passed through an alumina plug. Crystal-
lization from Et2O-hexanes gave 3e (168 mg, 0.37 mmol, 72%
yield) as yellow orange crystals. Anal. Calcd for C27H29NO2-
Fe: C, 71.21; H, 6.42; N, 3.08. Found: C, 71.27; H, 6.46; N,
3.10.
Rea ction of 1 w ith Bu tNH2. To a CH2Cl2 solution (27 mL)
of 1 (554 mg, 1.25 mmol) cooled at -78 °C was added ButNH2
(1.58 mL, 15.0 mmol). Then the cooling bath was removed,
and the mixture was gradually warmed to ambient tempera-
ture. After the mixture was stirred for 1 h, the volatiles were
Rea ction of 1 w ith Na OC6H4-p-F . To a CH2Cl2 solution
(10 mL) of 1 (223 mg, 0.51 mmol) cooled at -78 °C was added
NaOC6H4-p-F (234 mg, 1.74 mmol) as a solid in one portion.
Then the cooling bath was removed, and the mixture was
gradually warmed to ambient temperature. After the mixture
(35) Rosenblum, M.; Giering, W. P.; Samuels, A.-B. Inorg. Synth.
1990, 28, 207.

Nucleophilic Addition to the η2-Alkyne Ligand
Organometallics, Vol. 20, No. 13, 2001 2749
Ta ble 4. Cr ysta llogr a p h ic Da ta
1
2
3e
3c′‚(CH2Cl2)1/2
5c
5f
5h ′
3k
formula
C
21H15O2FeBF4 C13H15O2FeBF4 C27H29NO2Fe C25.5H27NO2Fe- C25H25NO2Fe C25H23NO2Fe C17H12O3
BF4Cl
C25H24O2FeS
fw
442.0
345.9
455.4
557.6
427.3
425.3
264.3
444.4
cryst syst
space group
a/Å
b/Å
c/Å
triclinic
P1h
monoclinic
C2/c
16.925(6)
14.213(4)
14.211(5)
monoclinic
P21/n
13.951(5)
17.314(8)
10.245(2)
monoclinic
P2/a
28.35(2)
10.031(7)
9.619(5)
monoclinic
P2/c
9.716(2)
18.969(4)
12.645(2)
monoclinic
P21/a
12.034(3)
18.66(1)
9.776(5)
monoclinic monoclinic
P21/n
P21/a
14.144(6)
14.570(7)
10.129(2)
102.95(2)
99.65(3)
103.38(4)
1925(2)
4
8.671(2)
18.058(3)
8.723(3)
9.193(4)
33.201(8)
8.272(3)
R/deg
â/deg
γ/deg
V/ Å3
Z
111.44(2)
105.62(8)
99.45(5)
109.14(1)
110.0(1)
108.86(2)
115.12(8)
3182(2)
8
1.44
2383(3)
4
1.27
2698(3)
4
1.37
2201.7(7)
4
1.29
2063(3)
4
1.37
1292.5(6)
4
2286(2)
4
d
calcd/g‚cm-3
1.53
8.3
1.36
1.29
µ/cm-1
9.9
6.5
7.07
7.04
7.5
0.93
7.67
2θ/deg
diffractometer
no. of data collected 8450
no. of data with
I > 3σ(I)
2-53
AFC5S
5-50
AFC5R
3027
1631
2-50
AFC5S
4591
2210
5-50
AFC7R
5409
2716
5-50
AFC7R
4268
2366
2-55
AFC5S
5195
1850
5-55
AFC7R
3265
1904
2-55
AFC5R
5707
2793
4479
no. of variables
489
175
280
333
262
262
229
261
isotropic refinement B2, F5-8
B1,2, F1-8
0.085
0.080
H1,2
0.064
0.057
R
0.079
0.080
0.065
0.047
0.033
0.057
0.042
0.041
0.029
0.072
0.057
Rw
0.076
4l
4o
4q
4s
4t
4v
4w
4y
formula
fw
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
C
33H24O4Fe C28H22O3Fe
540.4 462.3
monoclinic orthorhombic orthorhombic triclinic
C27H19FO3Fe C27H15F5O3Fe C27H20SO2Fe C21H15N3O2Fe C28H20O4Fe
466.3 538.3 464.4 397.2 476.3
orthorhombic monoclinic
C29H22O3Fe
474.3
orthorhombic orthorhombic
C2/c
P212121
P212121
P1h
P212121
P21
Pna21
P212121
24.277(5)
11.692(3)
18.988(4)
18.989(6)
6.479(5)
17.919(5)
18.184(3)
18.405(2)
6.494(2)
9.685(3)
13.464(4)
9.080(3)
101.91(3)
98.79(3)
91.91(2)
1142.3(6)
2
17.376(5)
19.83(1)
6.508(2)
8.599(1)
13.703(4)
7.711(2)
17.147(4)
6.546(4)
20.221(3)
6.406(5)
17.524(5)
20.332(6)
101.70(1)
95.10(2)
5279(2)
8
1.36
2205(3)
4
2173.3(7)
4
2243(1)
4
905.0(6)
2
2270(2)
4
2283(1)
4
1.38
Z
d
calcd/g‚cm-3
1.39
1.43
1.57
1.38
1.46
1.39
µ/cm-1
6.0
7.1
7.2
7.2
7.8
8.5
7.0
6.9
2θ/deg
diffractometer
no. of data collected 5005
no. of data with
5-50
AFC5R
5-55
AFC5R
5668
1760
5-60
AFC5R
3571
2556
5-50
AFC5R
5556
3985
5-50
AFC5R
2951
1571
2-50
AFC5S
1801
1498
5-60
AFC5R
3888
2648
5-55
AFC5R
3136
1108
2583
I > 3σ(I)
no. of variables
343
239
289
325
280
243
298
133
isotropic refinement
R
Rw
C12-26
0.059
0.056
C8-38
0.088
0.060
0.040
0.031
0.038
0.026
0.041
0.035
0.060
0.034
0.036
0.025
0.035
0.022
3z
35H36O3Fe
11a
11c
13f
14i
17
formula
fw
C
C10H14NO2FeBF4
322.9
C39H31NO2FeB
612.3
C20H22O3Fe
366.2
C15H20O2SFe
320.2
C16H20O2S2Fe2
420.2
560.5
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
triclinic
P1h
orthorhombic
Pbca
14.652(4)
14.637(2)
12.755(2)
orthorhombic
Pna21
20.802(4)
9.852(2)
orthorhombic
Pbca
19.59(1)
21.432(8)
8.840(6)
orthorhombic
Pbca
16.026(3)
33.059(6)
5.970(3)
monoclinic
P21/c
7.759(3)
12.272(3)
9.765(2)
10.390(2)
16.641(3)
9.366(1)
106.04(1)
95.68(1)
74.65(2)
1500.1(5)
2
14.831(3)
109.60(2)
2735(1)
8
1.57
3039(2)
4
1.34
3712(4)
8
1.31
3163(2)
8
1.35
875.9(4)
2
1.59
Z
d
calcd/g‚cm-3
1.24
5.3
µ/cm-1
11.4
5.32
8.2
10.7
18.9
2θ/deg
5-50
AFC5R
5600
3224
5-60
AFC5R
4451
2088
5-50
AFC5R
2054
1770
5-55
AFC5R
4785
1286
5-55
AFC5R
4106
2285
5-50
AFC5R
1755
1158
diffractometer
no. of data collected
no. of data with
I > 3σ(I)
no. of variables
isotropic refinement
R
355
208
206
179
172
140
H1-9
0.044
0.047
C11-56
0.057
0.056
C5-9
0.078
0.059
H1-8b
0.036
0.029
0.098
0.076
0.029
0.025
Rw

2750 Organometallics, Vol. 20, No. 13, 2001
Akita et al.
was stirred for 30 min, the volatiles were removed under
reduced pressure. The residue was extracted with ether and
passed through an alumina plug. Crystallization from Et2O-
hexanes gave 4q (275 mg, 0.59 mmol, 58% yield) as yellow-
orange crystals. Anal. Calcd for C27H19O2FFe: C, 69.57; H,
4.08; F, 4.08. Found: C, 69.56; H, 4.06; F, 4.16.
Rea ction of 1 w ith Na SP h . To a CH2Cl2 solution (20 mL)
of 1 (454 mg, 1.02 mmol) cooled at -78 °C was added NaSPh
(132 mg, 1.00 mmol) as a solid in one portion. Then the cooling
bath was removed, and the mixture was gradually warmed to
ambient temperature. After the mixture was stirred for 1 h,
the volatiles were removed under reduced pressure. The
residue was extracted with ether and passed through an
alumina plug. Crystallization from nitromethane gave 4t (402
mg, 0.86 mmol, 86% yield) as yellow-orange crystals. Anal.
Calcd for C27H20O2SFe: C, 69.84; H, 4.34; S, 6.91. Found: C,
69.68; H, 4.34; S, 6.61.
Other reactions were carried out with essentially the same
methods as described above.
Exp er im en ta l P r oced u r e for X-r a y Cr ysta llogr a p h y.
Suitable single crystals were mounted on glass fibers, and
diffraction measurements were made on Rigaku AFC-5, AFC-
5R, and AFC7R automated four-circle diffractometers by using
graphite-monochromated Mo KR radiation (λ ) 0.71059 Å).
The unit cells were determined and refined by a least-squares
method using 20 independent reflections (2θ ≈ 20°). Data were
collected with an ω-2θ or ω-scan techniques. If σ(F)/F was
more than 0.1, a scan was repeated up to three times, and the
results were added to the first scan. Three standard reflections
were monitored at every 100 (AFC5) and 150 measurements
(AFC5R and AFC7R). Data collections were performed on a
FACOM A-70 (data collection by AFC5), a micro vax II
computer (data collection by AFC5R), and a VENTURIS FX
5133 computer (data collection by AFC7R), and structural
analysis was performed on IRIS Indigo and O2 computers
(structure analysis) by using the teXsan structure solving
program system36 obtained from the Rigaku Corp., Tokyo,
J apan. Neutral scattering factors were obtained from the
standard source.37 In the reduction of data, Lorentz and
polarization corrections were made. An empirical absorption
correction (Ψ scan) was also made. Crystallographic data and
the results of refinements are summarized in Table 4.
The structures were solved by a combination of the direct
methods (SAPI9138 and MITHRIL87)39 and Fourier synthesis
(DIRDIF).40 Unless otherwise stated, non-hydrogen atoms were
refined with anisotropic thermal parameters, and hydrogen
atoms were fixed at calculated positions (C-H ) 0.95 Å) and
were not refined. In case the number of diffraction data was
not enough for full refinement, some atoms were refined with
isotropic parameters (4o and 4y) or using rigid groups (C22-
26 in 4o; C11-15 in 11c; C5-9 in 13f), as indicated in Table
4. The disordered BF4 groups (B2 and F5-8 in 1 and 2) were
also refined using rigid groups, and the population of the two
disorder components in 2 was found to be B1F1-4:B2F5-8 )
1:1.
Rea ction of 2 w ith NH2P r i. To a CH2Cl2 solution (40 mL)
of 2 (702 mg, 2.03 mmol) cooled at -78 °C was added NH2Pri
(2.0 mL, 34 mmol). Then the cooling bath was removed, and
the mixture was gradually warmed to ambient temperature.
During this period, the solution color changed from orange to
dark brown. After the mixture was stirred for 10 min, the
volatiles were removed under reduced pressure. The residue
was extracted with ether and passed through an alumina plug.
Crystallization from hexanes gave 10a (246 mg, 0.78 mmol,
38% yield) as dark brown crystals. Anal. Calcd for C16H23NO2-
Fe: C, 60.58; H, 7.31; N, 4.42. Found: C, 59.57; H, 7.21; N,
4.15. From the residue, which was insoluble in ether, the
cationic amine complex 11a was isolated as a black solid.
Rea ction of 2 w ith NHP r i2. To a CH2Cl2 solution (20 mL)
of 2 (355 mg, 1.03 mmol) cooled at -78 °C was added NHPri
2
(1.0 mL, 7.1 mmol). Then the cooling bath was removed, and
the mixture was gradually warmed to ambient temperature.
During this period, the solution color changed from orange to
yellow. After the mixture was stirred for 1 h, the volatiles were
removed under reduced pressure. The residue was extracted
with hexanes and passed through an alumina plug. Removal
of the volatiles under reduced pressure left 12 (184 mg, 0.71
mmol, 69% yield) as a yellow oil. 12: δH (C6D6) 1.25 (3H, t,
CH2CH3), 1.72 (3H, d, CHCH3), 2.06-2.19 (2H, m, CH2CH3),
4.13 (5H, s, Cp), 4.7 (1H, m, dCH); δC (C6D6) 15.6, 15.7 (q × 2,
J ) 126 Hz, CH3), 36.6 (t, J ) 178 Hz, CH2), 76.1 (d, 160, d
CH), 85.6 (d, J ) 180, Cp), 87,9 (s, CR), 200.3 (m, Câ), 216.5,
216.7 (s × 2, CO). IR (CH2Cl2): νCO 2013, 1957 cm-1. An
analytically pure sample of oily 12 could not be obtained.
Rea ction of 2 w ith Na SEt. To a CH2Cl2 solution (40 mL)
of 1 (711 mg, 2.05 mmol) cooled at -78 °C was added NaSEt
(277 mg, 3.30 mmol) as a solid in one portion. Then the cooling
bath was removed, and the mixture was gradually warmed to
ambient temperature. After the mixture was stirred for 30
min, the volatiles were removed under reduced pressure. The
residue was extracted with ether and passed through an
alumina plug. Crystallization from CH2Cl2-hexanes gave Fp-
SEt (152 mg, 0.64 mmol, 31% yield). Chromatographic separa-
tion of the mother liquor gave two yellow bands, from which
the two metallacyclic compounds were isolated: 14i (eluted
with CH2Cl2/hexanes ) 1:5; recrystallized from hexanes 107
mg, 0.33 mmol, 16% yield) and 15i (eluted with CH2Cl2/
hexanes ) 1:3; 153 mg, 0.47 mmol, 23% yield). Further
chromatographic separation of the mother liquor of 14i gave
16i (165 mg, 0.52 mmol, 25% yield) as a yellow oil.
Ack n ow led gm en t. We are grateful to the Yamada
Science Foundation and the Ministry of Education,
Culture, Sports, Science and Technology of the J apanese
Government for financial support of this research.
Su p p or tin g In for m a tion Ava ila ble: Tables of spectro-
scopic data for organometallic products and the results of
elemental analyses. Tables of positional parameters and Beq
values, anisotropic thermal parameters, bond lengths and
angles, and atomic numbering schemes. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM010095T
(36) teXsan; Crystal Structure Analysis Package; Rigaku Corp.:
Tokyo, J apan, 1985, 1992, and 1999.
(37) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, 1975; Vol. 4.
(38) Fan, H.-F. Structure Analysis Programs with Intelligent Con-
trol: Rigaku Corp.: Tokyo, J apan, 1991.
(39) Gilmore, C. J . MITHRIL-an integrated direct methods com-
puter program; University of Glasgow: Glasgow, UK, 1990.
(40) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system, Technical Report of the Crystallography
Laboratory; University of Nijmegen: Nijmegen, The Netherlands, 1992.