Preparation, structural characterization, and reactions of tantalum-alkyne complexes TaCl3(R1C≡CR2)L2 (L2 = DME, Bipy, and TMEDA; L = Py)

Article abstract of DOI:10.1021/om020510x

Tantalum-alkyne complexes with the general formula TaCl₃(R¹C≡CR²)(dme) (1a, R¹ = R² = Et; 1b, R¹ = R² = n-C₅H₁₁; 1c, R¹ = Ph, R² = Me; 1d, R¹ = R² = Ph; DME = 1,2-dimethoxyethane) were synthesized by treatment of the corresponding alkynes with a low-valent tantalum derived by reduction of tantalum pentachloride with zinc powder in a mixed solvent of toluene and DME. The DME ligand can be replaced by 2 equiv of pyridine to afford the corresponding dipyridine complexes TaCl₃(R¹C≡CR²)(py)₂ (2a, R¹ = R² = Et; 2b, R¹ = R² = n-C₅H₁₁; 2c, R¹ = Ph, R² = Me; 2d, R¹ = R² = Ph). Additionally, the reaction of 1a with the bidentate nitrogen ligands bipyridine and N,N,N′,N′-tetramethyethylenediamine (= TMEDA) gave TaCl₃(EtC≡CEt)(bipy) (3) and TaCl₃(EtC≡CEt)(tmedia) (4), respectively. The η²- and 4e-coordination mode of an alkyne with a large contribution of a metalacyclopropene canonical structure was revealed by spectroscopic methods (NMR and IR) and crystallographic analyses of 1a, 1c, 2a, and 4. The reactivies of the tantalum-3-hexyne complexes 1a, 2a, 3, and 4 toward 3-phenylpropanal were investigated. Only the pyridine complex 2a reacted with a stoichiometric amount of the aldehyde to afford the corresponding allylic alcohol in 77% yield upon hydrolysis. The reaction proceeded via an oxatantalacyclopentene species.

Full text of DOI:10.1021/om020510x

464
Organometallics 2003, 22, 464-472
P r ep a r a tion , Str u ctu r a l Ch a r a cter iza tion , a n d Rea ction s
of Ta n ta lu m -Alk yn e Com p lexes Ta Cl3(R1CtCR2)L2
(L2 ) DME, Bip y, a n d TMEDA; L ) P y)
Toshiyuki Oshiki,*,† Kouji Tanaka,† J un Yamada,† Takaya Ishiyama,†
Yasutaka Kataoka,‡ Kazushi Mashima,‡ Kazuhide Tani,‡ and Kazuhiko Takai*,†
Department of Applied Chemistry, Faculty of Engineering, Okayama University,
Tsushima, Okayama 700-8530, J apan, and Department of Chemistry, Graduate School of
Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, J apan
Received J une 27, 2002
Tantalum-alkyne complexes with the general formula TaCl3(R1CtCR2)(dme) (1a , R1 )
R2 ) Et; 1b, R1 ) R2 ) n-C5H11; 1c, R1 ) Ph, R2 ) Me; 1d , R1 ) R2 ) Ph; DME ) 1,2-
dimethoxyethane) were synthesized by treatment of the corresponding alkynes with a low-
valent tantalum derived by reduction of tantalum pentachloride with zinc powder in a mixed
solvent of toluene and DME. The DME ligand can be replaced by 2 equiv of pyridine to
afford the corresponding dipyridine complexes TaCl3(R1CtCR2)(py)2 (2a , R1 ) R2 ) Et; 2b,
R1 ) R2 ) n-C5H11; 2c, R1 ) Ph, R2 ) Me; 2d , R1 ) R2 ) Ph). Additionally, the reaction of
1a with the bidentate nitrogen ligands bipyridine and N,N,N′,N′-tetramethyethylenediamine
() TMEDA) gave TaCl3(EtCtCEt)(bipy) (3) and TaCl3(EtCtCEt)(tmeda) (4), respectively.
The η2- and 4e-coordination mode of an alkyne with a large contribution of a metalacyclo-
propene canonical structure was revealed by spectroscopic methods (NMR and IR) and
crystallographic analyses of 1a , 1c, 2a , and 4. The reactivies of the tantalum-3-hexyne
complexes 1a , 2a , 3, and 4 toward 3-phenylpropanal were investigated. Only the pyridine
complex 2a reacted with a stoichiometric amount of the aldehyde to afford the corresponding
allylic alcohol in 77% yield upon hydrolysis. The reaction proceeded via an oxatantalacyclo-
pentene species.
Sch em e 1
In tr od u ction
Alkyne complexes of transition metals have attracted
considerable attention in organometallic chemistry.1-3
Characterization and theoretical calculations of various
alkyne complexes have revealed their structures and the
bonding nature of the metal-alkyne bond. Most mono-
meric metal-alkyne complexes have η2-alkyne ligands,
and the structure of the metal-alkyne fragment is best
described as a metalacyclopropene structure.4-6 These
metal-η2-alkyne complexes react with unsaturated
organic molecules, such as aldehydes and nitriles, and
the reaction involves the insertion of the unsaturated
organic molecule into a metal-carbon bond of the η2-
alkyne complexes to afford a ring-expanded metalacycle
complex.7 These transformations of transition metal η2-
alkyne complexes have been applied to stoichiometric
organic transformation with titanium,8,9 zirconium,10,11
and niobium12,13 as the central metal. In 1990, we
reported that allylic alcohols are synthesized from
alkynes and aldehydes with a low-valent tantalum
(Scheme 1).14-16 In these reactions, the formation of
tantalum-η2-alkyne complexes and the insertion of
carbonyl groups into the tantalum-carbon bonds have
been postulated. The formation of the tantalum-η2-
alkyne complexes has been supported experimentally
† Okayama University.
‡ Osaka University.
(1) Caffyn, A. J . M.; Nicholas, K. M. In Comprehensive Organome-
tallic Chemistry II; Abel, E. W., Stone, F. A., G, W., Eds.; Pergamon:
NewYork, 1995; Vol. 12, p 685.
(2) Schore, N. E. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. A., G, W., Eds.; Pergamon: New York, 1995;
Vol. 12, p 703.
(8) Broene, R. D.; Buchwald, S. L. Science 1993, 261, 1696.
(9) Sato, F.; Urabe, H.; Okamoto, S. Chem. Rev. 2000, 100, 2835.
(10) Negishi, E.; Takahashi, T. Bull. Chem. Soc. J pn. 1998, 71, 755.
(11) Negishi, E.; Takahashi, T. Acc. Chem. Res. 1994, 27, 124.
(12) Roskamp, E. J .; Pedersen, S. F. J . Am. Chem. Soc. 1987, 109,
6551.
(3) Buchwald, S. L.; Nielsen, R. B. Chem. Rev. 1988, 88, 1047.
(4) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals, 3rd ed.; J ohn Wiley & Sons: New York, 2001.
(5) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1.
(6) Otsuka, S.; Nakamura, A. Adv. Organomet. Chem. 1976, 14, 245.
(7) Grotjahn, D. B. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. A., G, W., Eds.; Pergamon: New York, 1995;
Vol. 12, p 741.
(13) Hartung, J . B.; Pedersen, S. F. J . Am. Chem. Soc. 1989, 111,
5468.
(14) Takai, K.; Kataoka, Y.; Utimoto, K. J . Org. Chem. 1990, 55,
1707.
(15) Kataoka, Y.; Miyai, J .; Tezuka, M.; Takai, K.; Utimoto, K. J .
Org. Chem. 1992, 57, 6796.
(16) Kataoka, Y.; Miyai, J .; Oshima, K.; Takai, K.; Utimoto, K. J .
Org. Chem. 1992, 57, 1973.
10.1021/om020510x CCC: $25.00 © 2003 American Chemical Society
Publication on Web 01/08/2003

Reactions of Tantalum-Alkyne Complexes
Organometallics, Vol. 22, No. 3, 2003 465
Ta ble 1. 13C{1H} NMR a n d IR Da ta for Ta n ta lu m -Alk yn e Com p lexes
complex
13C{1H} NMR δ (ppm)
IR (ν CtC) cm-1
ref
1a
1b
1c
1d
2a
2b
2c
2d
3
256.0
253.6
242.0, 256.4
244.2
256.4
253.8
256.2, 243.7
244.2
260.7
256.1
239.4
199.68
237.81
237.01
224.4, 226.0
216.2
188.4
226.8, 269.3
234.7, 262.3
1622
1686
1672
1699
1640
1634
1650
1643
a
1675
b
b
b
b
this work
this work
this work
this work
this work
this work
this work
this work
this work
this work
31
31
33
23
28
21
19
18
18
4
CpTaMe2(ArCtCAr)c
CpTaMe(ArCtCAr)(η2-MeCdNt-Bu)c
LTa(EtCtCEt)Cld
LTa(PrCtCPr)Cld
(DIPP)3Ta(PhCtCSiMe3)e
b
(DIPP)3Ta(PhCtCPh)e
1580
1592
b
e
(EtCtCEt)Ta(dNAr)(DIPP)(py)2
TpMe2TaCl2(PhCtCMe)f
TpMe2TaMe2(PhCtCMe)f
b
a
b
d
Not observed. Not given in the literature. c Ar ) p-tolyl. L ) 2,6-[ArN(SiMe3)CH2]2NC5H3 (Ar )2,6-iPr2C6H3). e DIPP ) 2,6-
diisopropylphenoxide. f TpMe2 ) hydrotris(3,5-dimethylpyrazolyl)borate.
by the formation of a vicinal dideuterated cis-alkene
after quenching a reaction mixture of alkyne and the
low-valent tantalum with alkaline D2O.14,17
generated low-valent tantalum with an equimolar
amount of 3-hexyne at 50 °C for 8 h gave 1a in 65%
yield. During the reaction, the color of the reaction
mixture gradually turned from dark green to reddish
brown. The yield of 1a depended strongly on the solvent,
and a hydrocarbon solvent, such as toluene and benzene,
was necessary in order to suppress a drastic exothermic
reaction between tantalum pentachloride and DME.
Thus, toluene was added to tantalum pentachloride
before slowly adding DME to the resulting suspension.
Complexes 1b-d were prepared in a manner similar
to 1a . All alkyne complexes decomposed upon exposure
to air.
In 1999, Hierso and Etienne isolated the tantalum-
η2-alkyne complex TaCl3(PhCtCMe)(dme), which was
prepared by our low-valent tantalum methodology.18
They characterized the complex by 1H NMR and el-
emental analysis; however, there have been no reports
to date on the crystallographic study of the tantalum-
η2-alkyne complexes with the general formula TaCl3-
(RCtCR′)(dme). In this paper, we present a detailed
synthetic method for TaCl3(RCtCR′)(dme), and their
molecular structures are characterized by an X-ray
crystallographic analysis. The reactivities of these com-
plexes toward nitrogen donor ligands or aldehydes are
also described.
NMR and IR spectral data and elemental analyses of
1
the complexes 1a -d revealed their structures. The H
NMR spectrum of 1a displayed the two methyl signals
of the DME ligand at δ 3.13 and 3.59 and the methylene
signals as two sets of multiplet peaks at δ 3.10-3.17.
The dissymmetric signal pattern of DME suggests that
one of the two oxygen atoms of DME coordinates to the
tantalum atom in a trans position to the alkyne ligand
and the other in a cis position, and hence the three
chloride ligands occupy meridional positions.19 The
complexes 1b-d exhibited essentially the same 1H NMR
spectra as 1a .
Resu lts a n d Discu ssion
Syn th esis an d Ch ar acter ization of TaCl3(alkyn e)-
(d m e) Com p lexes. Tantalum-alkyne complexes with
the general formula TaCl3(R1CtCR2)(dme) (1a , R1
)
R2 ) Et; 1b, R1 ) R2 ) n-C5H11; 1c, R1 ) Ph, R2 ) Me;
1d , R1 ) R2 ) Ph; DME ) 1,2-dimethoxyethane) were
prepared by the reaction of an in situ generated low-
valent tantalum species with the corresponding alkynes
in modest yields (eq 1). For example, the reduction of
In general, an alkyne ligand coordinates to a metal
center as two-electron or four-electron donor molecules.
The four-electron donation has been observed for electron-
deficient organometallic complexes.5 The most informa-
tive data for the coordination mode of the alkyne ligand
are their 13C chemical shift values.20 The 13C NMR
signals for the alkyne carbon atoms of 1a -d appeared
at a lower field (δ 242.0-256.4) than those of the
reported η2-alkyne complexes of tantalum having a
cyclopentadienyl or aryloxy ligand (δ 188.4-239.4)
(Table 1). It should be noted that the alkyne carbon of
TpMe2 tantalum-η2-alkyne complexes also resonated at
ca. 260 ppm.18 These spectroscopic data indicate that
the alkyne ligand donates four electrons to the electron-
tantalum pentachloride with an excess amount of zinc
powder in a mixed solvent of toluene and DME afforded
a low-valent tantalum species. Treatment of the in situ
(19) Chao, Y.-W.; Wexler, P. A.; Wigley, D. E. Inorg. Chem. 1989,
28, 3860.
(20) Templeton, J . L.; Ward, B. C. J . Am. Chem. Soc. 1980, 102,
(17) Kataoka, Y.; Takai, K.; Oshima, K.; Utimoto, K. Tetrahedron
Lett. 1990, 31, 365.
(18) Hierso, J .-C.; Etienne, M. Eur. J . Inorg. Chem. 2000, 839.
3288.

466 Organometallics, Vol. 22, No. 3, 2003
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 1a , 1c, 2a , a n d 4
Oshiki et al.
1a
1c
2a
4
formula
fw
C
10H20Cl3O2Ta
C13H18Cl3O2Ta
493.59
C16H20Cl3N2Ta
527.65
C12H26Cl3N2Ta
485.66
459.57
cryst dimens, mm
cryst syst
space group (No.)
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.30 × 0.40 × 0.50
triclinic
P1h (#2)
7.406(2)
15.822(3)
7.068(1)
96.56(2)
108.53(2)
78.70(2)
768.7(3)
2
0.50 × 0.30 × 0.20
monoclinic
P21/n (#14)
7.105(3)
12.729(5)
18.788(9)
0.50 × 0.20 × 0.10
monoclinic
P21/n (#14)
14.406(3)
8.881(2)
16.330(2)
0.40 × 0.30 × 0.20
monoclinic
P21/c (#14)
7.75(1)
14.13(1)
15.93(2)
93.69(6)
114.62(1)
93.92(5)
1695(1)
4
1.933
69.39
944
1899.2(8)
4
1.845
61.98
1016
1739(3)
4
1.854
67.57
944
Z
F (calcd) (g cm-3
)
1.985
76.45
440
µ (cm-1
F(000)
)
diffractmeter
radiation (d, Å)
2θmax
AFC7R
AFC7R
AFC7R
RAXIS IV
Mo KR () 0.71069 Å)
55.0
55.0
55.0
58.7
total: 3507
unique 3471
no. of reflns measd
total: 3836
unique: 3832
Rint ) 0.038
3271
146
22.40
0.032
0.086
0.213
1.10
total: 4398
unique: 4161
Rint ) 0.089
2962
172
24.19
0.046
0.087
0.123
1.19
total: 4839
unique: 4508
Rint ) 0.041
2962
199
22.65
0.047
0.083
0.147
1.25
no. of reflns obsd (I > 2σ(I))
no. of variables
refln/param ratio
R1(F) (I > 2σ(I))
R1(F2) (all data)
wR2(F2) (all data)
GOF
2915
163
21.29
0.078
0.114
0.209
1.74
deficient metal center.3,20,21 In addition, the IR ab-
sorption bands for the metal-coordinated carbon-carbon
bonds of 1a -d appeared at 1622-1699 cm-1, which are
larger wavenumbers than those of aryloxytantalum
complexes, 1580 cm-1 for (DIPP)3Ta(PhC≡CPh)
(DIPP ) 2,6-diisopropylphenoxide)21 and 1592 cm-1 for
(EtCtCEt)Ta(dNAr)(DIPP)(py)2 (Ar ) 2,6-diisopropyl-
phenyl),19 and are comparable to those of trichloronio-
bium-η2-alkyne complexes, 1684 cm-1 for NbCl3(PhCt
CPh)(thf)222 and 1692 cm-1 for NbCl3(PhCtCMe)(thf)2.22
Although the coordination geometries of the η2-alkyne
unit of 1a and 1c are unsymmetrical in the solid state
(vide infra), the 13C resonances of these η2-alkyne
carbons are observed as a singlet peak. These equivalent
signals can be accounted for by the fact that the
η2-alkyne unit rotates rapidly on a tantalum-trans-
oxygen axis on the NMR time scale.23
Most of the tantalum-alkyne complexes synthesized
to date have bulky ligands such as Cp* and aryloxy
ligands that stabilize alkyne complexes.24-29 In contrast,
the alkyne complexes 1a -d contain no such bulky
ligands and have substitutionally labile chloride ligands.
Thus, these complexes are a useful starting material
for preparing new tantalum complexes having an alkyne
ligand. One example is the preparation of TpMe2TaCl3-
F igu r e 1. ORTEP drawing of complex 1a with the
numbering scheme. Selected bond distances (Å) and angles
(deg) are given in Table 3.
The solid state molecular structures of 1a and 1c were
determined by single-crystal X-ray crystallographic
analyses. Table 2 provides a listing of the crystal data
and refinement data. Figure 1 shows an ORTEP dia-
gram of 1a , and selected bond distances and angles are
listed in Table 3. Orientation of the 3-hexyne ligand for
1a is depicted in Figure 2. For the complex 1a , the
tantalum atom has a distorted octahedral geometry in
which 3-hexyne occupies one corner trans to O(1) of the
DME ligand. The 3-hexyne ligand coordinates in an η2-
fashion to the tantalum center as a formal four-electron
donor ligand and is best described as a tantalacyclo-
propene structure.29 The coordination geometry around
the tantalum center is essentially the same as that
(PhCtCMe) from 1c and KTpMe2 18
.
(21) Strickler, J . R.; Bruck, M. A.; Wexler, P. A.; Wigley, D. E.
Organometallics 1990, 9, 266.
(22) Cotton, F. A.; Shang, M. Inorg. Chem. 1990, 29, 508.
(23) Gue`rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 3154.
(24) Bruck, M. A.; Copenhaver, A. S.; Wigley, D. E. J . Am. Chem.
Soc. 1987, 109, 6525.
(25) Kwon, D.; Curtis, D. Organometallics 1990, 9, 1.
(26) Smith, G.; Schrock, R. R.; Churchill, M. R.; Youngs, W. J . Inorg.
Chem. 1981, 20, 387.
(27) Belmonte, P. A.; Clock, F. G. N.; Theopold, K. H.; Shroch, R. R.
Inorg. Chem. 1984, 23, 2365.
(28) Strickler, J . R.; Wexler, P. A.; Wigley, D. E. Organometallics
1988, 7, 2067.
(29) Curtis, M. D.; Real, J .; Kwon, D. Organometallics 1989, 8, 1644.
(30) Takai, K.; Ishiyama, T.; Yasue, H.; Nobunaka, T.; Itoh, M.;
Oshiki, T.; Mashima, K.; Tani, K. Organometallics 1998, 17, 5128.

Reactions of Tantalum-Alkyne Complexes
Organometallics, Vol. 22, No. 3, 2003 467
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 1a , 1c, 2a , a n d 4
1a
1c
2a
4
Ta-Cl(1)
2.383(2)
2.386(2)
2.417(2)
2.355(6)
2.396(2)
2.377(2)
2.409(2)
2.300(6)
2.417(3) 2.303(4)
2.394(3) 2.375(3)
2.408(3) 2.293(4)
Ta-Cl(2)
Ta-Cl(3)
Ta-O(1)
Ta-N(1)
2.410(9) 2.66(1)
2.275(9) 2.286(9)
Ta-O(2)
2.196(5)
2.216(6)
Ta-N(2)
Ta-C(1)
2.046(9)
2.102(7)
1.39(1)
96.38(8)
89.54(7)
84.0(1)
2.047(9)
2.053(9)
1.31(1)
96.92(10) 96.2(1)
88.73(9)
86.2(2)
2.04(1)
2.07(1)
1.31(2)
2.18(1)
2.19(1)
1.33(2)
88.2(1)
92.8(1)
Ta-C(2)
C(1)-C(2)
Cl(1)-Ta-Cl(2)
Cl(2)-Ta-Cl(3)
Cl(3)-Ta-O(2)
Cl(3)-Ta-N(2)
Cl(1)-Ta-O(2)
Cl(1)-Ta-N(2)
Cl(1)-Ta-Cl(3)
Cl(2)-Ta-O(2)
Cl(2)-Ta-N(2)
Cl(1)-Ta-O(1)
Cl(1)-Ta-N(1)
Cl(1)-Ta-C(1)
Cl(1)-Ta-C(2)
C(1)-Ta-C(2)
O(1)-Ta-O(2)
N(1)-Ta-N(2)
88.5(1)
86.2(2)
84.2(2)
87.8(3)
83.7(1)
81.7(2)
85.2(3)
160.85(8) 161.34(9) 162.4(1) 164.8(1)
157.8(1)
157.3(2)
F igu r e 3. ORTEP drawing of complex 1c with the
numbering scheme. Selected bond distances (Å) and angles
(deg) are given in Table 3.
162.1(2) 156.0(3)
79.8(1)
80.5(2)
80.8(2)
85.7(3)
81.1(3)
88.7(3)
89.0(2)
107.1(2)
39.1(3)
71.7(2)
85.7(3)
105.4(2)
37.3(4)
72.6(2)
the electron-withdrawing phenyl substituent on the
alkyne fragment.
107.7(3) 110.0(5)
37.1(4)
35.5(4)
Liga n d Exch a n ge Rea ction s betw een Com p lexes
1 a n d Nitr ogen Don or Molecu les. The ligand ex-
change reaction of 1a with THF in toluene at room
temperature proceeded rapidly within a few minutes.
However, a complex mixture of unidentified products
was obtained, which is consistent with the observation
that no alkyne complex was obtained from a reaction
of low-valent tantalum and an alkyne in a mixed solvent
of toluene and THF. On the other hand, the DME ligand
of 1a -d was readily replaced by nitrogen donor ligands
such as pyridine, bipyridine, and N,N,N′,N′-tetrameth-
ylenthylenediamine () TMEDA). The ligand replace-
ment reaction of 1a with 2 equiv of pyridine in toluene
at room temperature for 30 min afforded TaCl3(EtCt
CEt)(py)2 (2a ) as red crystals in 42% yield. Other
79.4(3)
143(1)
74.5(4)
135(1)
C(1)-C(2)-C(3) 142.9(9)
138.0(9)
F igu r e 2. Schematic drawing of the coordination geometry
around the tantalum atom of 1a .
pyridine complexes TaCl3(R1CtCR2)(py)2 (2b , R1
)
R2 ) n-C5H11; 2c, R1 ) Ph, R2 ) Me; 2d , R1 ) R2 ) Ph)
were prepared in a similar manner. Moreover, complex
2a was prepared directly by the simple addition of
3-hexyne to a low-valent tantalum generated by reduc-
tion of tantalum pentachloride with zinc in the presence
of 10 equiv of pyridine in toluene. The coordinated
pyridine was found to be labile, as an exchange reaction
between TaCl3(EtCtCEt)(C5D5N)2 (2a -d10) and pyridine
in C6D5CD3 was observed. A similar rapid ligand
exchange of the pyridine ligand on the tantalum atom
was reported for Ta(dNCR3)Cl3(py)2.35 The reaction of
1a with the bidentate ligands bipyridine and TMEDA
afforded more stable alkyne complexes TaCl3(EtCt
CEt)L2 (3, L2 ) bipyridine; 4, L2 ) TMEDA) in 49% and
61% yield, respectively. The 1H NMR spectrum of 4
showed two singlet signals at δ 2.36 and 2.74 due to
two magnetically nonequivalent methyl groups of TME-
DA. This indicates that the TMEDA ligand coordinates
in a bidentate fashion to the tantalum atom and that
the coordination geometry around the tantalum atom
is essentially the same as that of 1. In the 13C NMR
spectral data for 3 and 4, the chemical shift values of
the alkyne carbons were observed at δ 260.7 and 256.1,
observed for TaCl3(dme)(PhCHdNCH2Ph).30 The plane
consists of 3-hexyne carbons, C(1) and C(2), and the
tantalum center roughly bisects the Cl(1)-Ta-Cl(2) and
Cl(3)-Ta-O(2) angles. The dihedral angles of (C(3)-
C(2)-Ta-O(2) and C(3)-C(2)-Ta-Cl(3) are 38(1)° and
45(1)°, respectively. The bond distances of Ta-C(1)
(2.046(9) Å), Ta-C(2) (2.102(7) Å), and C(1)-C(2) (1.39-
(1) Å) and the angles of C(1)-C(2)-C(3) (142.9(9) Å) and
C(2)-C(1)-C(4) (140.6(7) Å) are comparable to those
found for tantalum-η2-alkyne complexes (Table 4).23,31-34
The distance of Ta-O(1) (2.355(6) Å) is much longer
than that of Ta-O(2) (2.196(5) Å). The long Ta-O(1)
distance can be attributed to the strong electron-
donating property (strong trans influence) of the 3-hex-
yne group. The molecular structure of the 1-phenyl-1-
propyne analogue 1c is essentially the same as that of
1a (Figure 3). The Ta-O(1) distance of 1c (2.300(6) Å)
is slightly shorter than that of 1a , presumably due to
(31) Curtis, M. D.; Real, J .; Hirpo, W.; Butler, W. M. Organometallics
1990, 9, 66.
(32) Cotton, F. A.; Hall, W. T. Inorg. Chem. 1980, 20, 2352.
(33) Gue`rin, F.; McConville, D. H.; Vittal, J . J .; Yap, C. A. P.
Organometallics 1998, 17, 1290.
(34) Strickler, J . R.; Wexler, P. A.; Wigley, D. E. Organometallics
1991, 10, 118.
(35) Korolev, A. V.; Rheingold, A. L.; Williams, D. S. Inorg. Chem.
1997, 36, 2647.

468 Organometallics, Vol. 22, No. 3, 2003
Oshiki et al.
Ta ble 4. Selected Bon d Dista n ces a n d An gles for Ta n ta la cyclop r op en e F r a gm en ts of Ta n ta lu m -η2-Alk yn e
Com p lexes
complex
Ta-C
C(1)-C(2)
C(1)-Ta-C(2)
ref
1a
1c
2a
4
2.046(9), 2.102(7)
2.047(9), 2.053(9)
2.07(1), 2.04(1)
2.18(1), 2.19(1)
2.09(1), 2.11(1)
2.069(8), 2.066(8)
2.062(7), 2.085(7)
2.075(14), 2.030(12)
2.070(3), 2.076(3)
2.061(5), 2.063(5)
1.39(1)
1.31(1)
1.31(2)
1.33(2)
39.1(3)
37.3(4)
37.1(4)
35.5(4)
b
b
b
b
this work
this work
this work
this work
31
32
23
33
34
18
CpTaMe(ArCtCAr)Me(CNt-Bu)a
Ta(PhCtCPh)Cl4(py)-
1.30(1)
1.325(12)
1.287(11)
1.30(2)
1.346(5)
1.322(7)
Ta(n-PrCtCn-Pr)(BDPP)c
Ta(PhCtCC(n-Pr)dC(n-Pr)CHdCHPh)(BDPP)c
d
Ta(PhCtCPh)(DIPP)3
37.9(1)
b
TpMe2TaMe2(PhCtCMe)e
a
b
d
Ar ) p-tolyl. Not given in the literature. c BDPP ) 2,6-(ArNCH2)2-NC5H3; Ar ) 2,6-diisopropylphenyl. DIPP ) 2,6-diisopropy-
lphenoxide. e TpMe2 ) hydrotris(3,5-dimethylpyrazolyl)borate.
F igu r e 5. Schematic drawing of the coordination geometry
around the tantalum atom of 2a .
F igu r e 4. ORTEP drawing of complex 2a with the
numbering scheme. Selected bond distances (Å) and angles
(deg) are given in Table 3.
respectively, indicating that the alkyne ligand donates
four electrons to the tantalum center.18
F igu r e 6. ORTEP drawing of complex 4 with the number-
ing scheme. Selected bond distances (Å) and angles (deg)
are given in Table 3.
The 3-hexyne ligand coordinates to the tantalum nearly
orthogonally to the trans-pyridine ring, and the C(1)-
C(2)-Ta plane intersects the Cl(1)-Ta-Cl(2) and Cl(3)-
Ta-N(2) angles. The trans influence of the alkyne
ligand in 2a elongated the bond distance of Ta-N(1)
(2.410(9) Å) more than that of Ta-N(2) (2.275(9) Å). The
chelating coordination of the TMEDA ligand somewhat
deviates the geometry of 4 from that of 2a . On the other
hand, in 4, the Ta-N(1) bond length (2.66(1) Å) trans
to the 3-hexyne ligand is considerably longer than that
of Ta-N(2) (2.286(9) Å). Thus, the N(2) atom of 4
coordinates weakly to the tantalum center.
The pyridine complex 2a (Figures 4 and 5) and
TMEDA complex 4 (Figure 6) were further characterized
by crystallographic studies. Selected bonds distances
and angles of 2a and 4 are listed in Table 4. The
molecular structure of 2a was found to have the same
geometry as the DME complexes 1a and 1c. The
tantalum atom of 2a is surrounded by the 3-hexyne
ligand, two nitrogen atoms of two pyridine ligands, and
three chloride atoms located at meridional positions.

Reactions of Tantalum-Alkyne Complexes
Organometallics, Vol. 22, No. 3, 2003 469
To elucidate the effect of the ligand on the reactivity
of the tantalum-η2-alkyne complex, the reactions of the
tantalum-3-hexyne complexes 1a , 2a , 3, and 4 with
3-phenylpropanal were examined by addition of an
equimolar amount of the aldehyde to a toluene solution
of the tantalum complex, followed by hydrolysis with
an aqueous NaOH solution.
two kinds of methyl protons of the 3-hexyne moiety. In
the 13C{1H} NMR spectrum, the quaternary carbons of
the oxatantalacyclopentene fragment were observed at
δ 100.0 (Cγ), 182.2 (Câ), and 223.9 (CR).21 With the
exception of the oxatantalacyclopentene fragment, the
exact structure of 7a is still unclear, because the
coordination of the other ligands, such as the number
of chloride atoms and pyridines, cannot be identified by
1H and 13C{1H} NMR spectroscopies. The most plausible
pathway to 7a from 2a is that one of the labile pyridine
ligands of 2a is replaced by acetone. However, no signals
When the bis(pyridine) complex 2a was used, 3-phen-
ylpropanal was completely consumed and the allylic
alcohol 6 was obtained in 77% yield. No organic byprod-
ucts were observed in this reaction. On the other hand,
in the case of bidentate diamine complexes 3 and 4 and
the DME complex 1a , the allylic alcohol 5 was not
obtained. Complex 3 did not react with the aldehyde,
and the aldehyde was recovered in 80% yield. When 4
reacted with the aldehyde, 4 was completely consumed
at 25 °C within 2 h, although compound 6 was obtained
in only 4% yield and many uncharacterized organic
products were formed. The reaction of 1a with the
aldehyde at 25 °C within 30 min afforded many organic
products including 1,3-diene, (3E,5E)-4,5-diphenyl-1,8-
diphenyl-3,5-octadiene (9% yield). The formation path-
way for the 1,3-diene was deduced from our previous
report for the reaction of an alkyne and a NbCl5-Zn
reagent.16 Thus, only the tantalum-alkyne complexes
bearing two pyridine ligands, 2a , cleanly reacted with
the aldehyde to afford the corresponding allylic alcohol
6 in good yield. These findings are consistent with our
previous report that pyridine is an indispensable addi-
tive for the preparation of the allylic alcohol in high yield
in the in situ reaction of the tantalum-alkyne complexes
with carbonyl compounds in a mixed solvent of benzene
and DME.16 In addition, the formation of the allylic
alcohol from the tantalum-η2-alkyne complexes strongly
suggests that the reaction proceeds via an oxatantala-
cyclopentene complex 5a , which is generated by the
insertion of a carbonyl group of the aldehyde into the
tantalum-carbon bond of the tantalacyclopropene frag-
ment.
1
due to a free pyridine was observed by H NMR. The
1
variable-temperature H NMR spectrum (-50 to -10
°C) showed three broad singlet peaks (δ 6.54, 6.85, 8.68)
assigned to the pyridines. At higher temperatures, we
could not observe any signals under various experimen-
tal conditions. We suppose that the labile coordinated
pyridine ligand dissociates from the tantalum center
and recoordinates rapidly on the NMR time scale, and
thus no free pyridine signals were observed by NMR
spectroscopy. We cannot rule out another possible
pathway to 7a , which is formed by the exchange of a
chloride anion of 2a for acetone. The oxatantalacyclo-
pentene fragment of 7b derived from 2b and acetone
1
was also characterized by H and 13C{1H} NMR. The
13C signals of quaternary carbon atoms, which construct
the oxatantalacyclopentene, appeared at δ 100.1 (Cγ),
181.6 (Câ), and 223.9 (CR). Hydrolysis of 7b using
aqueous NaOH gave the corresponding allylic alcohol
8 in 83% yield (eq 3). This result also suggests the
proposed oxatantalacyclopentene structures.
Con clu sion s
We have isolated and characterized new tantalum-
η2-alkyne complexes possessing a DME ligand. These
were prepared by a reaction of low-valent tantalum,
which was derived by reduction of tantalum pentachlo-
ride with zinc, and the corresponding alkynes. The
coordinated DME ligand was labile and easily substi-
tuted by pyridine, bipyridine, and TMEDA to afford the
corresponding amine complexes. The bis(pyridine) com-
plexes were intermediates in the formation of allylic
alcohols from alkynes and aldehydes using low-valent
tantalum reagent systems. The coordination of pyridine
to the tantalum center of the η2-alkyne complex was
required to afford the corresponding allylic alcohol upon
treatment with aldehydes and is consistent with our
previous results. In addition, the oxatantalacyclopen-
tene fragment derived from the insertion of a carbonyl
group of acetone into the tantalacyclopropene was
observed in solution by 1H and 13C{1H} NMR spec-
troscopies.
All attempts to isolate the oxatantalacyclopentene
complex 5a failed due to its thermal instability. There-
fore, we characterized the complex in solution by 1H and
13C NMR spectroscopies. For the complex derived from
3-phenylpropanal or benzaldehyde, no signals were
observed, despite using various experimental conditions.
On the other hand, the corresponding oxatantalacyclo-
pentene fragment was observed when 2a was treated
with acetone in C6D5CD3 at 25 °C. The reaction pro-
1
ceeded almost quantitatively to afford 7a . The H NMR
spectra of 7a at 263 K displayed a singlet peak at δ 1.13,
which was assigned to the methyl protons of the acetone
part. Two triplet signals at δ 0.82 and 1.48 were due to

470 Organometallics, Vol. 22, No. 3, 2003
Oshiki et al.
Ta Cl3(d ip h en yla cetylen e)(d m e) (1d ): 65% yield, recrys-
tallized from toluene/hexane. Mp: 143-146 °C (dec). 1H NMR
(C6D6): δ 3.11 (s, 3H, -OCH3), 3.11-3.17(m, 4H, -ÃCH2CH2-
Ã-), 3.73 (s, 3H, -OCH3), 7.01-7.11 (m, 2H, H, Hp-Ph), 7.30
(t, J ) 7.8 Hz, 4H, Ho-Ph), 8.07 (t, J ) 8.4 Hz, 4H, H, Hm-Ph).
13C NMR (C6D6): δ 62.8 (-OCH3), 68.5 (-OCH3), 70.8 (-OCH2-
CH2O-), 76.3 (-OCH2CH2O-), 128.8, 129.7, 130.8, 142.6
(Cipso-Ph), 244.2 (tCPh). IR (Nujol/CsI): 1699 (ν CtC), 303 (ν
Ta-Cl) cm-1. Anal. Calcd for C18H20Cl3O2Ta: C, 38.91; H, 3.67.
Found: C, 33.47; H, 3.34.
Exp er im en ta l Section
All manipulations involving air- and moisture-sensitive
compounds were carried out using standard Schlenk tech-
niques under argon. 1,2-Dimethoxyethane (DME), THF, and
toluene were purchased from Wako Pure Chemical Industries,
Ltd. and stored on 4 Å molecular sieves under argon. Tantalum
pentachloride was purchased from Nacalai Tesque, Inc. 1H and
13C NMR spectra were measured on a J EOL J NM-LA400
spectrometer. All 1H NMR chemical shifts were reported in
ppm relative to protio impurity resonance as follows: CDCl3,
singlet at 7.26 ppm; C6D6, singlet at 7.20 ppm; CD2Cl2, triplet
at 5.35 ppm; C6D5CD3, quintet at 2.09 ppm. Other spectra were
recorded using the following instruments: IR, Nicolet PRO-
TEÄ GEÄ 460T; UV/vis spectra, J asco V-570. Elemental analyses
were performed at RIKEN. Elemental analysis of 1d , 2c, and
2d led to low observed values for carbon under various
analytical conditions. Similar results also have been reported
for group 5 complexes.35-37 All melting points were measured
in sealed tubes and were not corrected.
P r ep a r a tion of P yr id in e Com p lexes 2. A typical proce-
dure is described for the preparation of 2a . To a solution of
1a (0.19 g, 0.42 mmol) in toluene (25 mL) was added pyridine
(0.068 g, 0.85 mmol). The color of the mixture turned to red.
After stirring for 30 min, the red solution was concentrated
to 5 mL in vacuo and cooled to -20 °C for 2 days. Complex 2a
was obtained as red crystals (0.094 g, 0.18 mmol) in 42% yield,
1
mp 157-158 °C (dec). H NMR plus 1H-1H COSY (C6D6): δ
1.41 (t, J ) 7.5 Hz, 6H, tCCH2CH3), 3.73 (q, J ) 7.5 Hz, 4H,
tCCH2CH3), 6.29 (t, J ) 7.2 Hz, 2H, Ho-pyridine-A), 6.53 (t, J )
6.6 Hz, 2H, Ho-pyridine-B), 6.69 (t, J ) 7.6 Hz, 1H, Hp-pyridine-A),
6.83 (t, J ) 7.4 Hz, 1H, Hp-pyridine-B), 8.67 (d, J ) 5.1 Hz, 2H,
P r ep a r a tion of DME Com p lexes 1. A typical procedure
is described for the preparation of 1a . Toluene (16 mL) was
added to TaCl5 (1.2 g, 3.3 mmol) in an 80 mL Schlenk tube,
and then DME (16 mL) was slowly added to the resulting
yellow suspension. Zn powder (0.32 g, 4.9 mmol) was added
to the mixture in one portion at room temperature. After
stirring the mixture at room temperature for 40 min, the low-
valent tantalum was prepared in quantitative yield. 3-Hexyne
(0.37 mL, 3.3 mmol) was added to the suspension and stirred
at 50 °C for 2 h. All volatiles were removed in vacuo, and the
resulting orange powder was extracted with toluene (50 mL).
The extract was placed in a -20 °C freezer. Upon standing
overnight, orange crystals were deposited. Removal of the
supernatant by a syringe afforded 0.98 g (2.1 mmol, 65%) of
H
m-pyridine-B), 9.31 (brs, 2H, Hm-pyridine-A). 13C{1H} NMR plus
DEPT (CD2Cl2): δ 13.3 (tCCH2CH3), 33.4 (tCCH2CH3), 124.5,
139.2, 151.8, 256.4 (tCCH2CH3). IR (Nujol/CsI): 1640 (νCtC),
322 (νTa-Cl) cm-1. Anal. Calcd for C16H20Cl3N2Ta: C, 36.42; H,
3.82; N, 5.31. Found: C, 36.12; H, 3.89; N, 5.50.
Ta Cl
3(6-d od ecyn e)(p y)2 (2b): 87% yield, recrystallized
1
from toluene/hexane. Mp: 48-52 °C (dec).
1H NMR plus H-
1H COSY (C6D6): δ 0.93 (t, J ) 7.2 Hz, 6H, tC(CH2)4CH3),
1.35-1.47 (m, 8H, tC(CH
2)2CH2CH2CH3), 1.92-2.00 (m, 4H,
tCCH
2CH2(CH2)2CH3), 3.80 (t, J ) 7.6 Hz, 4H, tCCH2(CH2)3
-
CH
3), 6.36 (t, J ) 6.8 Hz, 2H, Ho-pyridine-A), 6.57 (brs, 2H,
o-pyridine-B), 6.76 (t, J ) 7.7 Hz, 1H, Hp-pyridine-A), 6.88 (brs,
H
1
1a in 65% yield. Mp: 129-130 °C (dec). H NMR (C6D5CD3):
1H, H
p-pyridine-B), 8.74 (d, J ) 5.5 Hz, 2H, Hm-pyridine-B), 9.32
(brs, 2H, H
m-pyridine-A). 13C{1H} NMR plus DEPT (C6D6): δ 14.3
δ 1.37 (t, J ) 7.5 Hz, 6H, tCCH2CH3), 3.10-3.17(m, 4H,
-OCH2CH2O-), 3.13 (s, 3H, -OCH3), 3.60 (q, J ) 7.5 Hz, 4H,
tCCH2CH3), 3.59 (s, 3H, -OCH3). 13C{1H} NMR plus DEPT
(CD2Cl2): δ 13.2 (tCCH2CH3), 33.3 (tCCH2CH3), 62.1 (-OCH3),
68.9 (-OCH3), 70.6 (-OCH2CH3O-), 76.4 (-OCH2CH2O-),
256.0 (tCCH2CH3). IR (Nujol/CsI): 1622 (ν CtC), 312 (ν Ta-
Cl) cm-1. Anal. Calcd for C10H20Cl3O2Ta: C, 26.14; H, 4.39.
Found: C, 25.92; H, 4.47.
(tC(CH
2)4CH3), 23.0 (tC(CH2)3CH2CH3), 29.1 (tC(CH2)2CH2
-
CH
2CH3), 32.8 (tCCH2CH2(CH2)2CH3), 40.9 (tCCH2(CH2)3
-
CH
3), 124.0, 138.4, 152.7, 253.8(tC(CH2)4CH3). IR (Nujol/
CsI): 1634 (ν
Cl
CtC), 301 (νTa-Cl) cm-1. Anal. Calcd for C22H32
3N2Ta: C, 43.19; H, 5.27; N, 4.58. Found: C, 43.07; H, 4.99;
N, 4.32.
Ta Cl3(1-p h en yl-1-p r op yn e)(p y)2 (2c): 61% yield, recrys-
-
tallized from CH2Cl2/hexane. Mp: 207-208 °C (dec). 1H NMR
(CD2Cl2): δ 3.49 (s, 3H, tCCH3), 7.28-7.53 (m, 9H), 7.86-
7.96 (m, 2H), 8.59 (d, J ) 5.1 Hz, 2H, Hm-pyridine-B), 9.51 (brs,
2H, Hm-pyridine-A). 13C{1H} NMR (CD2Cl2): δ 24.7 (tCCH3),
124.5, 128.1, 130.0, 131.1, 139.3, 141.7 (Cipso-Ph), 151.9, 243.7
(tCCH3), 256.2 (tCPh). IR (Nujol/CsI): 1650 (νCtC), 292
(νTa-Cl) cm-1. Anal. Calcd for C19H18Cl3N2Ta: C, 40.63; H, 3.23;
N, 4.99. Found: C, 39.92; H, 3.19; N, 4.96.
Ta Cl3(6-d od ecyn e)(d m e) (1b): 75% yield, recrystallized
from 1:1 toluene/hexane. Mp: 70-72 °C (dec). 1H NMR
(C6D6): δ 0.95 (t, J ) 6.3 Hz, 6H, tC(CH2)4CH3), 1.40-1.43
(m, 8H, tC(CH2)2CH2CH2CH3), 1.94-2.01 (m, 4H, tCCH2-
CH2(CH2)2CH3), 3.13-3.21 (m, 4H, tCCH2(CH2)3CH3), 3.22 (s,
3H, -OCH3), 3.67 (s, 3H, -OCH3), 3.78 (t, J ) 7.6 Hz, 4H,
-OCH2CH2O-). 13C{1H} NMR plus DEPT (C6D6): δ 14.3
(tC(CH2)4CH3), 22.9 (tC(CH2)3CH2CH3), 29.0 (tC(CH2)2CH2-
CH2CH3), 32.7 (tCCH2CH2(CH2)2CH3), 40.7 (tCCH2(CH2)3-
CH3), 62.3 (-OCH3), 68.0 (-OCH3), 70.4 (-OCH2CH2O-), 75.9
(OCH2CH2O), 253.6 (tC(CH2)4CH3). IR (Nujol/CsI): 1686 (ν
CtC), 325 (ν Ta-Cl) cm-1. Anal. Calcd for C16H32Cl3O2Ta: C,
35.34; H, 5.93. Found: C, 35.26; H, 5.74.
Ta Cl3(d ip h en yla cetylen e)(p y)2 (2d ): 36% yield, recrystal-
lized from CH2Cl2/hexane. Mp: 223-226 °C (dec). 1H NMR
1
plus H-1H COSY (CD2Cl2): δ 7.21-7.24 (m, 2H, Ho-pyridine-A),
7.25-7.29 (m, 2H, Hp-Ph), 7.41 (t, J ) 7.6 Hz, 4H, Hm-Ph), 7.49
(m, 2H, Ho-pyridine-B), 7.59 (d, J ) 6.9 Hz, 4H, Ho-Ph), 7.76-
7.81 (m, 1H, Hp-pyridine-A), 7.96 (t, J ) 7.6 Hz, 1H, Hp-pyridine-B),
8.59 (d, J ) 5.1 Hz, 2H, Hm-pyridine-A), 9.20 (brs, 2 H,
Ta Cl3(1-p h en yl-1-p r op yn e)(d m e) (1c): 57% yield, recrys-
tallized from toluene. Mp: 152-156 °C (dec). 1H NMR (C6D6):
δ 3.05 (s, 3H, tCCH3), 3.09-3.13 (m, 4H, -OCH2CH2O-), 3.61
(s, 3H, -OCH3), 3.70(s, 3H, -OCH3), 7.15--7.17 (m, 1H,
H
m-pyridine-B). 13C{1H} NMR (CD2Cl2): δ 124.4, 127.9, 128.8,
129.8, 139.1, 142.2 (Cipso-Ph), 152.1, 244.2(tCPh). IR (Nujol/
CsI): 1650 (νCtC), 292 (νTa-Cl) cm-1. Anal. Calcd for C24H20
-
H
H
p-Ph), 7.35 (t, J ) 7.8 Hz, 2H, Ho-Ph), 7.96-7.98 (m, 2H,
m-Ph). 13C{1H} NMR plus DEPT (C6D6): δ 24.6 (tCCH3), 62.6
Cl3N2Ta: C, 46.22; H, 3.23; N, 4.49. Found: C, 45.37; H, 3.03;
N, 4.54.
(-OCH3), 69.0 (-OCH3), 70.9 (-OCH2CH2O-), 76.6 (-OCH2-
CH2O-), 126.1, 127.7, 128.4, 129.5, 131.3, 140.7 (Cipso-Ph), 242.0
(tCCH3), 256.4 (tCPh). IR (Nujol/CsI): 1672 (νCtC), 310
(νTa-Cl) cm-1. Anal. Calcd for C13H18Cl3O2Ta: C, 31.63; H, 3.68.
Found: C, 31.40; H, 3.40.
NMR Exp er im en t of Liga n d Exch a n ge Rea ction of 1a .
Pyridine (3.2 µL, 0.040 mmol) was added to a solution of 1a
(9.0 mg, 0.020 mmol) in C6D6 (0.70 mL) containing 1,2-
dichloroethane (3.0 µL) as an internal standard in a NMR tube.
The NMR spectrum of the sample was measured after stand-
ing at room temperature for 30 min. Product ratios were
determined by integration of peak area of the 1H NMR
spectrum. The peak area of the product was given as follows:
(36) Rupprecht, G. A.; Messerle, L. W.; Fellmann, J . D.; Schrock,
R. R. J . Am. Chem. Soc. 1980, 102, 6236.
(37) Murphy, V. J .; Turner, H. Organometallics 1997, 16, 2495.

Reactions of Tantalum-Alkyne Complexes
Organometallics, Vol. 22, No. 3, 2003 471
400 for of 1a (4H, TaCl3(3-hexyne)(MeOCH2CH2OMe)); 403 for
1,2-dimethoxyethane (4H, MeOCH2CH2OMe), and 856 for 1,2-
dichloroethane (4H, ClCH2CH2Cl). From these values, the
yields of 2a and 1,2-dimethoxyethane were calculated to both
be in 91% yield based on the internal standard.
Ta Cl3(3-h exyn e)(bip y) (3). This complex was prepared in
a similar manner described for 2a : 49% yield, recrystallized
from CH2Cl2. Mp: 234-236 °C (dec). 1H NMR (CD2Cl2): δ 1.42
(t, J ) 7.5 Hz, 6H, tCCH2CH3), 3.72 (q, J ) 7.5 Hz, 4H, tC-
CH2CH3), 7.62-7.66 (m. 1H), 7.73-7.76 (m, 1H), 8.17-8.24
(m, 2H), 8.31-8.35 (m, 2H), 8.74-8.76 (m, 1H), 9.87-9.89 (m,
1H). 13C{1H} NMR (CD2Cl2): δ 13.4 (tCCH2CH3), 34.2 (tC-
CH2CH3), 122.8, 123.0, 126.4, 126.6, 139.9, 140.8, 149.4, 151.9,
an SGI O2 workstation at Venture Business Laboratory,
Graduate School of Okayama University. In the subsequent
refinement, the function ∑w(|Fo| - |Fc|)2 was minimized, where
|Fo| and |Fc| are the observed and calculated structure factor
amplitudes, respectively. The agreement indices are defined
as R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) [∑w(|Fo| - |Fc|)2/
∑w(|Fo|)2]1/2, respectively. Atomic positional parameters for the
non-hydrogen atoms of all complexes are given in the Sup-
porting Information.
Reaction of Tan talu m -Alkyn e Com plexes with 3-P h en -
ylp r op a n a l. A typical procedure is described for the reaction
of 2a with 3-phenylpropanal. To a solution of 2a (0.10 g, 0.20
mmol) in toluene (8 mL) was added 3-phenylpropanal (0.027
mL, 0.20 mmol) and stirred at 25 °C for 1.5 h. After addition
of aqueous NaOH (15 wt %), the mixture was stirred for 30
min. The reaction mixture was passed through a Hyflo-Super
Cel, and organic products were extracted with ether (10 mL
× 3). The combined extracts were dried over MgSO4 and
concentrated in vacuo. Purification of the crude product by
preparative TLC on silica gel (benzene/ethyl acetate, 30:1) gave
(E)-4-ethyl-1-phenyl-4-hepten-3-ol (0.033 g, 0.15 mmol) in 77%
152.5, 153.3, 260.7 (tCCH2CH3). IR (Nujol/CsI): 318 (νTa-Cl
)
cm-1. Anal. Calcd for C16H18Cl3N2Ta: C, 36.56; H, 3.45; N, 5.33.
Found: C, 36.38; H, 3.27; N, 5.25.
Ta Cl3(3-h exyn e)(tm ed a ) (4). This complex was prepared
in a similar manner described for 2a : 61% yield, recrystallized
1
from toluene/hexane. Mp: 100-102 °C (dec). H NMR (CD2-
Cl2): δ 1.41 (t, J ) 7.5 Hz, 6H, CH2CH3), 2.09 (m, 4H, CH2),
2.36 (s, 6H, N(CH3)2), 2.74 (s, 6H, N(CH3)2), 3.68 (q, J ) 7.5
Hz, 4H, CH2CH3). 13C{1H} NMR plus DEPT (C6D6): δ 14.0
(tCCH2CH3), 34.2 (tCCH2CH3), 50.8 (N(CH3)2), 53.7 (N(CH3)2),
57.3 (NCH2CH2N), 61.0 (NCH2CH2N), 256.1 (tCCH2CH3). IR
(Nujol/CsI): 1675 (νC≡C), 316 (νTa-Cl) cm-1. Anal. Calcd for
1
yield. Bp: 95 °C (0.9 Torr). H NMR (CDCl3): δ 0.99 (t, J )
7.5 Hz, 3H), 1.01 (t, J ) 7.6 Hz, 3H), 1.38 (brs, 1H), 1.87 (q,
J ) 7.5 Hz, 2H), 2.02-2.13 (m, 4H), 2.58 -2.77(m, 2H), 4.03-
4.07 (m, 1H), 5.37 (t, J ) 7.0 Hz, 1H), 7.18-7.30 (m, 5H). 13C-
{1H} NMR (CDCl3): δ 14.9, 15.2, 20.6, 21.2, 32.8, 76.8, 126.2,
128.8, 129.0, 129.1, 142.7, 143.0. IR (Nujol/CsI): 3350, 3050,
C
12H26Cl3N2Ta: C, 29.68; H, 5.40; N, 5.77. Found: C, 29.55;
H, 5.46; N, 5.68.
2960, 2870, 1605, 1495, 1450, 1050, 860, 750, 695 cm-1
.
Cr ysta llogr a p h ic Da ta Collection s a n d Str u ctu r e De-
ter m in a tion of 1a , 1c, 2a , a n d 4. Da ta Collection . A
suitable crystal of each compound was mounted in a glass
capillary under an argon atmosphere. Data for complexes 1a ,
1c, and 2a were collected by a Rigaku AFC-7R diffractometer
with graphite-monochromated Mo KR (λ ) 0.71069 Å) radia-
tion and a 12 kW rotating anode generator. The incident beam
collimator was 1.0 mm, and the crystal-to-detector distance
was 285 mm. Cell constants and an orientation matrix for data
collection, obtained from a least-squares refinement using the
setting angles of 25 carefully centered reflections, corresponded
to the cells with dimensions listed in Table 2, where details of
the data collection are summarized. The weak reflections (I <
10σ(I)) were rescanned (maximum of 2 rescans), and the counts
were accumulated to ensure good counting statistics. Station-
ary background counts were recorded on each side of the
reflection. The ratio of peak counting time to background
counting time was 2:1. Three standard reflections were chosen
and monitored every 150 reflections. For complex 4, measure-
ment was made on a Rigaku RAIS-IV imaging plate diffrac-
tometer with graphite-monochromated Mo KR (λ ) 0.71069
Å). The incident beam collimator was 0.5 mm, and the crystal-
to-detector distance was 100.02 mm with the detector at the
zero swing position. Indexing was performed from four oscil-
lations which were exposed for 4.0 min. The readout was
obtained in the 0.100 mm pixel mode. A total of 45 plates of
4.00° oscillation images were collected, each being exposed for
4.0 min. Cell constants are listed in Table 2.
NMR Ch a r a cter iza tion of Oxa ta n ta la cyclop en ten e
Com p lexes 7a a n d 7b. 7a : Acetone (4.6 µL, 0.062 mmol) was
added to a solution of 2a (33.0 mg, 0.062 mmol) in C6D5CD3
(0.70 mL) at room temperature in a NMR tube. During the
reaction, the color of the mixture gradually turned from
reddish orange to yellow. The NMR spectrum of the sample
was measured after standing at room temperature for 30 min.
1H NMR (C6D6CD3, 263 K): δ 0.82 (t, J ) 7.6 Hz, 3H), 1.13 (s,
6H), 1.48 (t, J ) 7.6 Hz, 3H), 3.28 (q, J ) 7.6 Hz, 2 H), 6.54
(brs, 4H), 6.85 (brs, 2H), 8.68 (brs, 4H). 13C{1H} NMR plus
DEPT (C6D5CD3, 263 K): δ 14.1, 165.5, 22.5, 27.2, 35.7, 100.0,
124.0, 137.4, 149.5, 182.2. 7b: Acetone (2.6 µL, 0.035 mmol)
was added to a solution of 2b (21.0 mg, 0.035 mmol) in C6D5-
CD3 (0.70 mL) at room temperature in a NMR tube. During
the reaction, the color of the mixture gradually turned from
reddish orange to yellow. The NMR spectrum of the sample
was measured after standing at room temperature for 30 min.
1H NMR (C6D5CD3, 263 K): δ 0.86 (t, J ) 6.9 Hz, 3H), 0.99 (t,
J ) 6.7 Hz, 3H), 1.00-1.27 (m, 6H), 1.39 (s, 6H), 1.49 (brs,
4H), 1.81 (t, J ) 8.1 Hz, 2H), 2.02 (brs, 2H), 3.45 (t, J ) 7.7
Hz, 2H), 6.57 (brs, 4H), 6.86 (brs, 2H), 8.66 (brs, 4H). 13C{1H}
NMR plus DEPT (C6D5CD3, 263 K): δ 14.3, 14.6, 22.7, 23.1,
27.5, 29.6, 30.1, 30.5, 33.0, 33.2, 43.0, 100.1, 124.1, 137.4, 149.4,
181.6, 223.9.
Hyd r olysis of 7b. Complex 7b was generated in situ by
the addition of acetone (13 µL, 0.18 mmol) to 2b (0.108 g, 0.18
mmol) in toluene (5 mL). The reaction mixture was stirred at
25 °C for 2.5 h. After 15% aqueous NaOH was added and
stirred for 30 min, the mixture was passed through a Hyflo-
Super Cel and organic products were extracted with ether (10
mL × 3). The combined extracts were dried over MgSO4 and
concentrated in vacuo. Purification of the crude product by
preparative TLC on silica gel (hexane/ethyl acetate, 3:1) gave
Da ta Red u ction . An empirical absorption correction based
on azimuthal scans of several reflections was applied. The data
were corrected for Lorentz and polarization effects. The decays
of intensities of three representative reflections were -6.57%
for 1a , -5.10% for 1c, and -12.45% for 2a , and thus linear
correction factors were applied to the decay of these observed
data. Complex 4 showed no decay.
1
8 (0.033 g, 0.15 mmol) in 83% yield. H NMR (CDCl3): δ 0.94
Str u ctu r e Deter m in a tion a n d Refin em en t. All calcula-
tions were performed using a teXsan crystallographic software
package,38 and illustrations were drawn with Ortep-3 for
Windows.39 Crystallographic calculations were performed on
(t, J ) 7.1 Hz, 3H), 0.96 (t, J ) 7.1 Hz, 3H), 1.04 (brs, 1H),
1.32 (s, 6H), 1.33-1.37 (m, 8H), 1.39-1.47 (m, 2H), 2.08-2.18
(m, 4H), 5.59 (t, J ) 7.1 Hz, 1H). 13C{1H} NMR (CDCl3): δ
14.26, 14.30, 22.9, 23.0, 28.3, 28.4, 30.0, 30.1, 30.9, 32.1, 33.0,
73.3, 123.3, 146.5.
(38) teXsan, Crystal Structure Analysis Package; Molecular Struc-
ture Corporation, 1985 and 1992.
(39) Ortep-3 for Windows. Farrugia, L. J . J . Appl. Crystallogr. 1997,
30, 565.
Ack n ow led gm en t. We thank Keiko Yamada (RIK-
EN) for elemental analyses of new tantalum complexes.

472 Organometallics, Vol. 22, No. 3, 2003
Oshiki et al.
Su p p or tin g In for m a tion Ava ila ble: Structural drawings
of 1a , 1c, 2a , and 4 and tables of X-ray crystallographic data,
atomic coordinates, anisotropic thermal parameters, and a
complete list of bond distances and angles are included. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM020510X