Synthesis, structure, and reactivity of tantalum and tungsten homoenolate complexes

Article abstract of DOI:10.1021/om060264f

Preparation and characterization of homoenolate complexes of tantalum, Cp*Cl₃Ta(CH₂CR¹₂C(=O)-OR ²) (1a: R¹ = H, R² = Et; 1b: R¹ = R² = Me; 1c: R¹ = Me, R² = C₆H ₄CH₃-4), and tungsten, (Xyl-N=)Cl₃W(CH ₂CH₂C(=O)OEt) (7), using zinc homoenolate reagents are described. Intramolecular coordination of the carbonyl moiety to the metal center in these complexes was confirmed by their NMR and IR spectroscopy together with X-ray analyses of 1a and 1b. The insertion reaction of isocyanide into the metal carbon bond of 1a and 7, respectively, resulted in the formation of a diazametallacycle, Cp*Cl₃Ta-[N(Xyl)-C(=C=N-Xyl)-C(CH ₂CH₂CO₂Et)=N-Xyl] (3a), which possesses a metallacyclic structure with an exocyclic ketene-imine moiety, and an η²-iminoacyl tungsten complex, (Xyl-N=)W{C(-N-Xyl)-CH ₂CH₂CO₂Et}(CNXy])Cl₃ (8). The β-proton of the homoenolate moiety of la was selectively deprotonated by KN(SiMe₃)₂ to afford an η⁴-ethyl acrylate complex, Cp*Cl₂Ta(η⁴-ethyl acrylate) (4a). In the case of complex 1b, in which the β-positions were protected by dimethyl substituents, reaction with the dilithium salt of diazadiene afforded a tantalalactone complex, Cp*(η⁴-p-MeOC₆H ₄-DAD)Ta(CH₂-CMe₂C(=O)O) (5). The addition of Al(C₆F₅)₃ to 5 afforded a novel zwitterionic complex, Cp*(p-MeOC₆H₄-DAD)Ta(CH₂CMe ₂C(=O)O-Al(C₆F₅)₃) (6), in which Al(C₆F₅)₃ coordinated to the exocyclic carbonyl oxygen of the tantalalactone.

Full text of DOI:10.1021/om060264f

Organometallics 2006, 25, 3179-3189
3179
Synthesis, Structure, and Reactivity of Tantalum and Tungsten
Homoenolate Complexes
Hayato Tsurugi, Takashi Ohno, Tsuneaki Yamagata, and Kazushi Mashima*
Department of Chemistry, Graduate School of Engineering Science, Osaka UniVersity, Toyonaka, Osaka
560-8531, Japan
ReceiVed March 23, 2006
Preparation and characterization of homoenolate complexes of tantalum, Cp*Cl3Ta(CH2CR1 C(dO)-
2
OR2) (1a: R1 ) H, R2 ) Et; 1b: R1 ) R2 ) Me; 1c: R1 ) Me, R2 ) C6H4CH3-4), and tungsten, (Xyl-
Nd)Cl3W(CH2CH2C(dO)OEt) (7), using zinc homoenolate reagents are described. Intramolecular
coordination of the carbonyl moiety to the metal center in these complexes was confirmed by their NMR
and IR spectroscopy together with X-ray analyses of 1a and 1b. The insertion reaction of isocyanide into
the metal carbon bond of 1a and 7, respectively, resulted in the formation of a diazametallacycle, Cp*Cl3Ta-
[N(Xyl)-C(dCdN-Xyl)-C(CH2CH2CO2Et)dN-Xyl] (3a), which possesses a metallacyclic structure with
an exocyclic ketene-imine moiety, and an η2-iminoacyl tungsten complex, (Xyl-Nd)W{C(dN-Xyl)-
CH2CH2CO2Et}(CNXyl)Cl3 (8). The â-proton of the homoenolate moiety of 1a was selectively
deprotonated by KN(SiMe3)2 to afford an η4-ethyl acrylate complex, Cp*Cl2Ta(η4-ethyl acrylate) (4a).
In the case of complex 1b, in which the â-positions were protected by dimethyl substituents, reaction
with the dilithium salt of diazadiene afforded a tantalalactone complex, Cp*(η4-p-MeOC6H4-DAD)Ta(CH2-
CMe2C(dO)O) (5). The addition of Al(C6F5)3 to 5 afforded a novel zwitterionic complex, Cp*(p-
MeOC6H4-DAD)Ta(CH2CMe2C(dO)O-Al(C6F5)3) (6), in which Al(C6F5)3 coordinated to the exocyclic
carbonyl oxygen of the tantalalactone.
species are thus fascinating and in high demand. Our studies of
the chemistry of early transition metal complexes with five-
membered aza-7 and oxametallacycles8 led to our interest in
the â-functionalized alkyl complexes of early transition metals
because of the strong interaction between the early transition
metal and the functionalized group, forming an intramolecular
five-membered chelation. Here we report the preparation of
Introduction
Organometallic compounds with a functionalized alkyl ligand,
[LnM-(CH2)n-FG] (FG: functional group), have been the
subject of intensive investigation because the introduction of a
heteroatom into an alkyl moiety has a profound influence on
its stability and reactivity. This class of complexes has important
applications as synthetic building blocks in organic chemistry
and as catalysts for homogeneous reactions.1,2 Among func-
tionalized-alkyl organometallic complexes, â-functionalized
alkyl complexes have attracted special interest, and titanium
homoenolate complexes, which exhibit a unique chelating effect
on stabilizing alkyl species, are versatile reagents for carbon-
carbon bond formation.3 Chelating alkyl species have also been
used for catalytic reactions by late transition metals: the
copolymerization of ethylene and methyl acrylate by palladium
catalysts involving â- or γ-functionalized alkylpalladium com-
plexes,4 and the copolymerization of R-olefins and carbon
monoxide providing â-keto alkylpalladium complexes.5,6 In each
polymerization, these species had important roles in incorporat-
ing further monomers and in determining the polymer micro-
structure. Fundamental studies of the â-functionalized alkyl
(3) For titanium complexes: (a) Nakamura, E.; Kuwajima, I. J. Am.
Chem. Soc. 1977, 99, 7360. (b) Nakamura, E.; Kuwajima, I. J. Am. Chem.
Soc. 1983, 105, 651. (c) Goswami, R. J. Org. Chem. 1985, 50, 5907. (d)
Nakamura, E.; Oshino, H.; Kuwajima, I. J. Am. Chem. Soc. 1986, 108,
3745. (e) Cozzi, P. G.; Carofiglio, T.; Floriani, C. Organometallics 1993,
12, 2845. For other metal complexes: (f) Ryu, I.; Matsumoto, K.; Ando,
M.; Murai, S.; Sonoda, N. Tetrahedron Lett. 1980, 21, 4283. (g) Ryu, I.;
Ando, M.; Ogawa, A.; Murai, S.; Sonoda, N. J. Am. Chem. Soc. 1983,
105, 7192. (h) Nakamura, E.; Shimada, J.; Kuwajima, I. Organometallics
1985, 4, 641. (i) Oshino, H.; Nakamura, E.; Kuwajima, I. J. Org. Chem.
1985, 50, 2802. (j) Ryu, I.; Murai, S.; Sonoda, N. J. Org. Chem. 1986, 51,
2391. (k) Nakamura, E.; Aoki, S.; Sekiya, K.; Oshino, H.; Kuwajima, I. J.
Am. Chem. Soc. 1987, 109, 8056. (l) Aoki, S.; Nakamura, E.; Kuwajima,
I. Tetrahedron Lett. 1988, 29, 1541. (m) Ryu, I.; Suzuki, H.; Ogawa, A.;
Kambe, N.; Sonoda, N. Tetrahedron Lett. 1988, 29, 6137. (n) Aoki, S.;
Fujimura, T.; Nakamura, E.; Kuwajima, I. Tetrahedron Lett. 1989, 30, 6541.
(o) Nakahira, H.; Ryu, I.; Han, L.; Kambe, N.; Sonoda, N. Tetrahedron
Lett. 1991, 32, 229. (p) Kuwajima, I.; Nakamura, E. In ComprehensiVe
Organic Synthesis; Trost, B., Flemming, I., Eds.; Pergamon: Oxford, 1991;
Vol. 2, pp 441-454.
* To whom correspondence should be addressed. E-mail: mashima@
chem.es.osaka-u.ac.jp. Fax: 81-6-6850-6245.
(1) Steinborn, D. Angew. Chem., Int. Ed. Engl. 1992, 31, 401.
(2) (a) Werstiuk, N. H. Tetrahedron 1983, 39, 205. (b) Hoppe, D. Angew.
Chem., Int. Ed. Engl. 1984, 23, 932. (c) Ryu, I.; Sonoda, N. J. Synth. Org.
Chem. Jpn. 1985, 43, 112; Chem. Abstr. 1985, 102, 166796p. (d) Hoppe,
D.; Hense, T. Angew. Chem., Int. Ed. Engl. 1997, 36, 2282. (e) Heck, R.
D. Palladium Reagents in Organic Syntheses; Academic Press: London,
1985. (f) Tsuji, J. Palladium Reagents and Catalysts; Wiley: England, 1995.
(4) (a) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc.
1996, 118, 267. (b) Mecking, S.; Johnson, L. K.; Wang, L.; Brookhart, M.
J. Am. Chem. Soc. 1998, 120, 888.
(5) Recent reviews for R-olefin and CO copolymerization: (a) Sen, A.
Acc. Chem. Res. 1993, 26, 303. (b) Drent, E.; Budzelaar, P. H. M. Chem.
ReV. 1996, 96, 663. (c) Bianchini, C.; Meli, A. Coord. Chem. ReV. 2002,
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10.1021/om060264f CCC: $33.50 © 2006 American Chemical Society
Publication on Web 05/25/2006

3180 Organometallics, Vol. 25, No. 13, 2006
Tsurugi et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) of
Complexes 1a and 1b
homoenolate complexes of tantalum and tungsten, their unique
reactions with 2,6-dimethylphenylisocyanide (XylNC), and their
transformation of the homoenolate moiety by metal-amido
reagents.
1a
1b
Ta-C11
2.2378(16)
2.4241(4)
2.4292(4)
2.3976(4)
2.2263(11)
1.527(2)
1.480(2)
1.2372(18)
83.86(4)
149.57(4)
86.62(4)
74.30(5)
113.28(10)
119.09(10)
110.71(13)
121.52(13)
121.98(14)
2.186(13)
2.391(3)
2.434(3)
2.414(3)
2.234(8)
1.540(16)
1.489(17)
1.240(14)
86.8(3)
150.2(3)
85.7(4)
73.2(4)
118.0(9)
119.2(8)
106.8(10)
122.4(11)
119.7(12)
Ta-Cl1
Ta-Cl2
Results and Discussion
Ta-Cl3
Ta-O1
Synthesis, Characterization, and Reactivity of Tantalum
C11-C12
Homoenolate Complexes. The reaction of Cp*TaCl4 with 0.5
C12-C13
3h
C13-O1
equiv of Zn(CH2CH2CO2Et)2 in ether afforded the tantalum
C11-Ta-Cl1
C11-Ta-Cl2
C11-Ta-Cl3
C11-Ta-O1
Ta-C11-C12
Ta-O1-C13
C11-C12-C13
O1-C13-C12
O1-C13-O2
homoenolate complex 1a in 64% yield. Recrystallization from
a hot toluene solution gave analytically pure yellow crystals of
1a. The 1H NMR spectrum of 1a showed two triplet resonances
at δ 3.55 and 0.65 assignable to R- and â-methylene protons.
In the 13C NMR spectrum, the carbonyl carbon signal was
shifted downfield (δC 193.7) compared to that of the carbonyl
carbon (δC ca. 170) of organic esters, indicating that the carbonyl
group coordinated in an η1-fashion to the tantalum atom. The
coordination of the carbonyl group was further confirmed by
IR spectroscopy, in which ν(CdO) appeared at a lower
frequency (1625 cm-1) compared to organic esters.
smoothly, and 1b and 1c were obtained as yellow crystalline
solids. The stretching frequencies of the carbonyl group (1633
cm-1) and the carbonyl carbon resonance (δ 197.2) of 1b were
almost the same as those of 1a. Thus, the carbonyl group of
the homoenolate chain of 1b also coordinated to the tantalum
atom in the same mode. In the case of 1c, the chemical shift
value of the carbonyl carbon (δ 195.3) was assignable to the
coordinating carbonyl group of the tantalum atom. The carbonyl
stretching frequency of 1c (1649 cm-1) was slightly increased
compared to 1a and 1b due to the inductive effect of the
aromatic ester.
Similarly, â,â′-dimethyl-substituted homoenolate complexes,
Cp*Cl3Ta(CH2CMe2C(dO)OMe) (1b) and Cp*Cl3Ta(CH2-
CMe2C(dO)OC6H4CH3-4) (1c), were obtained by treating
Cp*TaCl4 with 1 equiv of IZn(CH2CMe2CO2R) (R ) Me, C6H4-
CH3-4). The transmetalation from zinc to tantalum proceeded
(6) For isolated â-keto alkyl palladium complexes as an intermediate
for R-olefin and CO copolymerization: (a) Drent, E.; Broekhoven, J. A.
M.; Doyle, M. J. J. Organomet. Chem. 1991, 417, 235. (b) Ozawa, F.;
Hayashi, T.; Koide, H.; Yamamoto, A. J. Chem. Soc., Chem. Commun.
1991, 1469. (c) Markies, B. A.; Rietveld, M. H. P.; Boersma, J.; Spek, A.
L.; van Koten, G. J. Organomet. Chem. 1992, 424, C12. (d) Dekker: G. P.
C. M.; Elsevier, C. J.; Vrieze, K.; van Leeuwen, P. W. N. M.; Roobeek, C.
F. J. Organomet. Chem. 1992, 430, 357. (e) van Asselt, R.; Gielens, E. E.
C. G.; Rulke, R. E.; Elsevier: C. J. J. Chem. Soc., Chem. Commun. 1993,
1203. (f) van Asselt, R.; Gielens, E. E. C. G.; Ru¨lke, R. E.; Vrieze, K.;
Elsevier, C. J. J. Am. Chem. Soc. 1994, 116, 977. (g) Markies, B. A.; Kruis,
D.; Rietveld, M. H. P.; Verkerk, K. A. N.; Boersma, J.; Kooijman, H.;
Lakin, M. T.; Spek, A. L.; van Koten, G. J. Am. Chem. Soc. 1995, 117,
5263. (h) Nozaki, K.; Sato, N.; Tonomura, Y.; Yasutomi, M.; Takaya, H.;
Hiyama, T.; Matsubara, T.; Koga, N. J. Am. Chem. Soc. 1997, 119, 12779.
(i) Green, M. J.; Britovsek, G. J. P.; Cavell, K. J.; Gerhards, F.; Yates, B.
F.; Frankcombe, K.; Skelton, B. W.; White, A. H. J. Chem. Soc., Dalton
Trans. 1998, 1137. (j) Groen, J. H.; De Zwart, A.; Vlaar, M. J. M.; Ernsting,
J. M.; van Leeuwen, P. W. N. M.; Vrieze, K.; Kooijman, H.; Smeets, W.
J. J.; Spek, A. L.; Anthony, L.; Budzelaar, P. H. M.; Xiang, Q.; Thummel,
R. P. Eur. J. Inorg. Chem. 1998, 8, 1129. (k) Luinstra, G. A.; Brinkmann,
P. H. P. Organometallics 1998, 17, 5160. (l) Reddy, K. R.; Chen, C.; Liu,
Y.; Peng, S.; Chen, J.; Liu, S. Organometallics 1999, 18, 2574. (m)
Braunstein, P.; Cossy, J.; Knorr, M.; Strohmann, C.; Vogel, P. New J. Chem.
1999, 23, 1215. (n) Braunstein, P.; Frison, C.; Morise, X. Angew. Chem.,
Int. Ed. 2000, 39, 2867. (o) Reddy, K. R.; Surekha, K.; Lee, G.; Peng, S.;
Chen, J.; Liu, S. Organometallics 2001, 20, 1292. (p) Braunstein, P.; Durand,
J.; Knorr, M.; Strohmann, C. Chem. Commun. 2001, 211. (q) Carfagna, C.;
Gatti, G.; Martini, D.; Pettinari, C. Organometallics 2001, 20, 2175. (r)
Stoccoro, S.; Minghetti, G.; Cinellu, M.; Zucca, A.; Manassero, M.
Organometallics 2001, 20, 4111. (s) Binotti, B.; Carfagna, C.; Gatti, G.;
Martini, D.; Mosca, L.; Pettinari, C. Organometallics 2003, 22, 1115. (t)
Shen, H.; Jordan, R. F. Organometallics 2003, 22, 1878. (u) Bianchini, C.;
Meli, A.; Oberhauser, W.; van Leeuwen, P. W. N. M.; Zuideveld, M. A.;
Freixa, Z.; Kamer, P. C. J.; Spek, A. L.; Gusev, O. V.; Kal’sin, A. M.
Organometallics 2003, 22, 2409. (v) Wu, H.; Liu, Y.; Peng, S.; Liu, S.
Eur. J. Inorg. Chem. 2003, 17, 3152. (w) Setsune, J.; Yamaguchi, T.;
Tanikawa, S.; Hirose, Y.; Watanabe, J. Organometallics 2004, 23, 6058.
(7) (a) Mashima, K.; Matsuo, Y.; Tani, K. Chem. Lett. 1997, 767. (b)
Mashima, K.; Matsuo, Y.; Tani, K. Organometallics 1999, 18, 1471. (c)
Mashima, K.; Matsuo, Y.; Nakahara, S.; Tani, K. J. Organomet. Chem.
2000, 593/594, 69. (d) Nakamura, A.; Mashima, K. J. Organomet. Chem.
2001, 621, 224. (e) Matsuo, Y.; Mashima, K.; Tani, K. Bull. Chem. Soc.
Jpn. 2002, 75, 1291. (f) Matsuo, Y.; Mashima, K.; Tani, K. Organometallics
2002, 21, 138.
The chelate structures of 1a and 1b were confirmed by X-ray
analyses (Figures 1a and 1b). Selected bond distances and angles
are summarized in Table 1. The tantalum atom of each complex
has a four-legged piano stool geometry with an additional
donation from the carbonyl oxygen atom at the opposite side
toward the Cp* ligand. Thus, the homoenolate moiety coordi-
nates to the tantalum atom via C(11) and O(1) atoms to form a
five-membered chelating structure. The molecular orbital of the
d0 piano stool CpTa fragment had two low-lying empty orbitals,
9
2
2
2
dx -y and dz , the latter being situated at the opposite side of
the CpTa moiety. The bond angles of Ta-O(1)-C(13) (119.09°
and 119.2°) and Cpcentroid-Ta-O(1) (177.8° and 175.8°) indicate
that the lone pair of carbonyl oxygens overlapped with the empty
2
dz orbital. A similar interaction between the electron donor
molecules, such as phosphine, isocyanide, carbonyl oxygen, and
2
ylide, and the empty dz orbital of the tantalum(V) complexes
with the four-legged piano stool geometry has been reported.10
(9) Yasuda, H.; Tatsumi, K.; Okamoto, T.; Mashima, K.; Lee, K.;
Nakamura, A.; Kai, Y.; Kanehisa, N.; Kasai, N. J. Am. Chem. Soc. 1985,
107, 2410.
(10) (a) Fandos, R.; Go´mez, M.; Royo, P.; Garcia-Blanco, S.; Martinez-
Carrera, S.; Sanz-Aparicio, J. Organometallics 1987, 6, 1581. (b) Arnold,
J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J.; Arif, A. M. J. Am. Chem.
Soc. 1989, 111, 149. (c) Go´mez, M., Go´mez-Sal, P.; Nicola´s, M. P.; Royo,
P. J. Organomet. Chem. 1995, 491, 121. (d) Ho¨cher, T.; Blaurock, S.; Hey-
Hawkins, E. Eur. J. Inorg. Chem. 2002, 1174. (e) Blaurock, S.; Hey-
Hawkins, E. Z. Anorg. Allg. Chem. 2002, 628, 2515.
(8) Matsuo, Y.; Mashima, K.; Tani, K. Angew. Chem., Int. Ed. 2001,
40, 960.

Tantalum and Tungsten Homoenolate Complexes
Organometallics, Vol. 25, No. 13, 2006 3181
The bond distance of Ta-O(1) [2.2263(11) Å for 1a and 2.234-
(8) Å for 1b] is in the range typically observed for tantalum
complexes with a coordinating carbonyl oxygen atom.11 The
Lewis acidic nature of the tantalum atom resulted in the
intramolecular chelating structure, which was also observed for
tin(IV)12 and Ti(IV)3a-e complexes, whereas homoenolate
complexes of Pt(II)13 and Au(I)14 have a nonchelating structure
due to the soft nature of their metal centers. The coordination
mode of the homoenolate depends on the Lewis acidity of the
metal. Notable differences between 1a and 1b are the distance
of the Ta-C(11) bond (2.2378 Å for 1a and 2.186 Å for 1b)
and the angles of Ta-C(11)-C(12) (113.28° for 1a and 118.0°
for 1b) and C(11)-C(12)-C(13) (110.71° for 1a and 106.8°
for 1b), which are presumably due to the steric effect of the
dimethyl group at the â-carbon of 1b.
The triflate ligand has a stronger electron-withdrawing
property than halides,15 and hence the metal center with triflate
ligands generally becomes more electron-deficient than that with
chlorine ligands. We conducted a ligand exchange reaction of
chlorine atoms with triflate ligands and compared the influence
of triflate or chloride on the coordination of carbonyl to the
tantalum atom. Metathesis reaction of 1a with 3 equiv of AgOTf
in toluene afforded a tris(triflate) complex, Cp*Ta(CH2CH2C-
(dO)OEt)(OTf)3 (2a), in 75% yield (eq 1), in which the three
triflates comprised the inner sphere ligands. The observed
solubility of 2a in aromatic hydrocarbons is consistent with the
general tendency that neutral early transition metal triflate
complexes are dissolved in aromatic and aliphatic solvents16
and an ionized bis(triflate) tantalum complex is insoluble in
aromatic and aliphatic hydrocarbons.17 In the 19F NMR spec-
trum, two singlet signals were observed as a 2:1 integral ratio,
indicating that the triflate ligands were tightly bound in an η1-
coordination mode to tantalum at two cis and one trans positions
relative to the alkyl moiety, and the ligand exchange process
between the inner and outer coordination spheres was accord-
ingly ruled out on the basis of the 19F NMR time scale at 308
K. In the 13C NMR spectrum, a resonance due to the methylene
carbon R to the tantalum atom was observed at δ 71.6, a value
downfield of that for 1a. Replacement of chloride atoms by
triflate ligands strengthened the bond between the carbonyl
oxygen atom and the tantalum atom of 1a, as evidenced by the
downfield shift of the carbonyl carbon (δC 198.9) and the
decreased CdO stretching frequency (1587 cm-1).
Figure 1. Molecular structure of the complexes 1a (top) and 1b
(bottom). All hydrogen atoms are omitted for clarity.
acrylate, or diphenylacetylene, due to the strong binding between
the carbonyl oxygen and the tantalum atom. In contrast,
isocyanide reacted with 1a to give an isocyanide multiple
insertion product. The addition of 2,6-dimethylphenylisocyanide
to 1a in toluene afforded Cp*Cl3Ta[N(Xyl)-C(dCdN-Xyl)-
C(CH2CH2CO2Et)dN-Xyl] (3a), in which 3 equiv of isocyanide
were consequently inserted into the tantalum carbon bond of
1a (eq 2). Although the single insertion of isocyanide into
metal-alkyl or -iminoacyl bonds of high-valent early transition
metal complexes has been extensively studied,18 there are only
a few examples of an isocyanide multiple insertion reaction for
tantalum complexes.18d,i,k The 13C NMR spectrum of 3a
displayed the carbonyl carbon signal around δ 170, the chemical
shift suggesting that the ester group of the homoenolate moiety
was released from the tantalum atom. The IR spectrum of 3a
exhibited three strong bands at 2037, 1731, and 1548 cm-1
,
which are assignable to ketene-imine, carbonyl, and imine
groups, respectively. The structural characteristics of 3a were
revealed by the X-ray analysis (Figure 2). Selected bond
distances and angles are listed in Table 2. Complex 3a has a
diazametallacycle structure with an exocyclic ketene-imine
group. Rothwell et al. reported a similar metallacyclic structure
for tantalum complexes supported by bulky aryloxy ligands.18d,i
The bond distance of Ta-N(1) [2.370(3) Å] is much longer
than that of Ta-N(3) [2.063(3) Å], indicating that the former
bond is an imine-donating bond to the tantalum atom,18d,i,h while
The metal-carbon bond of homoenolate is expected to be
reactive toward typical unsaturated organic molecules; however,
1a in CDCl3 did not react with carbon monoxide (1 atm), methyl
(11) (a) Sperry, C. K.; Cotter, W. D.; Lee, R. A.; Lachicotte, R. J.; Bazan,
G. C. J. Am. Chem. Soc. 1998, 120, 7791. (b) Weinert, C. S.; Fanwick, P.
E.; Rothwell, I. P. Organometallics 2005, 24, 5759.
(12) Harrison, P. G.; King, T. J.; Healy, M. A. J. Organomet. Chem.
1979, 182, 17.
(13) Ikura, K.; Ryu, I.; Ogawa, A.; Sonoda, N.; Harada, S.; Kasai, N.
Organometallics 1991, 10, 528.
(14) Ito, Y.; Inoue, M.; Suginome, M.; Murakami, M. J. Organomet.
Chem. 1988, 342, C41.
(15) Lawrance, G. A. AdV. Inorg. Chem. 1989, 34, 145.

3182 Organometallics, Vol. 25, No. 13, 2006
Tsurugi et al.
the replacement of the coordinated carbonyl moiety by the first
equivalent of isocyanide.
Figure 2. Molecular structure of 3a. All hydrogen atoms are
omitted for clarity.
Table 2. Selected Bond Distances (Å) and Angles (deg) of
Complex 3a
Scheme 1 shows two plausible mechanisms for the formation
of 3a. The first step of the reaction between 1a and isocyanide,
after the release of the carbonyl moiety from the tantalum atom,
afforded an η2-iminoacyl species. Typical η2-iminoacyl ligands
of high-valent early transition metal, lanthanide, and actinide
complexes are described as the three resonance structures A
(zwitterionic resonance form), B (amido-carbene resonance
form), and C (η2-iminoacyl resonance form), schematically
shown in Scheme 1.18a The formation of 3a was rationally
illustrated by two pathways (path A and path B). In path A, the
migratory insertion of isocyanide into the metal-iminoacyl
bond, giving 3a′, followed by nucleophilic attack of the third
isocyanide at the iminoacyl carbon, results in the formation of
3a. A similar mechanism for the formation of the imine-η2-
iminoacyl species, corresponding to 3a′, was proposed by Royo
et al. for the reaction of Cp*Ta(dNR) derivatives with excess
XylNC.18k The other pathway (path B) involves a nucleophilic
attack of isocyanide at the iminoacyl carbon to form an amido-
Ta-N1
2.370(3)
2.441(1)
2.473(1)
1.442(5)
1.354(5)
1.218(5)
97.05(10)
85.5(1)
Ta-N3
2.063(3)
2.4544(9)
1.307(4)
1.434(4)
1.200(5)
Ta-Cl1
Ta-Cl2
N1-C19
N3-C25
N2-C26
Ta-Cl3
C19-C25
C25-C26
O1-C22
N3-Ta-Cl1
N3-Ta-Cl3
N1-C19-C25
N2-C26-C25
N3-Ta-Cl2
N1-Ta-N3
N3-C25-C19
148.86(8)
72.7(1)
117.1(3)
114.5(3)
170.0(5)
the latter bond has the typical distance of a Ta-N(arylamido)
bond.7f,19 The ketene-imine moiety is revealed by the bond
distances of C(25)-C(26) [1.354(5) Å] and N(2)-C(26) [1.200-
(5) Å] and the bond angle of C(25)-C(26)-N(2) [170.0-
(5)°].18i,20 The ester moiety of the homoenolate fragment of 3a
is located at the outer coordination sphere of the tantalum atom,
suggesting that the resulting isocyanide insertion is initiated by
Scheme 1

Tantalum and Tungsten Homoenolate Complexes
Organometallics, Vol. 25, No. 13, 2006 3183
ketene-imine complex 3a′′, which is followed by the nucleo-
philic attack of CNXyl to the ketene-imine carbon. Tilley and
co-workers reported that the reaction of the thorium-silicon
bond with 2 equiv of carbon monoxide gave a metaloxy
ketene complex, Cp*2Th(Cl)[OC(dCdO)Si(SiMe3)3], an ana-
logue to 3a′′, and the following nucleophilic attack of iso-
cyanide at the ketene carbon afforded a dioxametallacycle
metal-homoenolate fragment was transformed to metallalactone
by cleavage of the O-CH3 bond from the ester group. The
formation of 5 might involve an elimination of CH3Cl via a
four-membered transition state. The same reaction pathway was
proposed by Qian et al. for their titanium complexes.24 Metal-
lalactone complexes of late transition metals are prepared by
the oxidative addition of acrylic acid or lactone to electron-
rich low-valent metals25 or a coupling reaction among metal,
alkene, and carbon dioxide.26 Early transition metals, titanalac-
tone,27 zirconalactone,28 and tantalalactone29 are prepared by
the reaction of low-valent ethylene or benzyne complexes with
CO2. Complex 5 is a relatively rare example of metallalactone
complexes of early transition metals.
bearing a ketene-imine moiety, Cp*2(Cl)Th[OC(dCdN-Xyl)-
C{Si(SiMe3)3}dO].21 It is likely that the reaction proceeded
through path A because an isoelectronic tungsten-homoenolate
complex reacted with 2 equiv of XylNC to give an η2-iminoacyl
complex with an η1-XylNC ligand (vide infra).
Reaction of Tantalum Homoenolate Complexes with
Metal-Amide Reagent. Deprotonation of the methylene proton
â to the tantalum atom and R to the carbonyl group was
accomplished by treatment of 1a with 1 equiv of KN(SiMe3)2,
giving an η4-EA (EA ) ethyl acrylate) complex, Cp*Cl2Ta-
(CH2CHdC(O)OEt) (4a) (eq 3). Similar oxatantalacyclopentene
complexes, Cp*Cl2Ta(CMe2CHdC(O)CH3),22 Cp*Cl2Ta(CH2-
CHdC(O)OMe),23 and Cp*Cl2Ta(CH2C(Me)dC(O)OMe),8 have
1
been reported. The H NMR spectrum of 4a showed three
doublets of doublets (δ 5.11, 1.32, and 0.53), assignable to an
olefinic proton and methylene protons bound to the tantalum
atom, and the spectral pattern was identical to that of
Cp*Cl2Ta(CH2CHdC(O)OMe).23 The 13C NMR spectrum of
4a displayed a new signal at δ 161.8, assignable to an olefinic
carbon bound to oxygen atoms, suggesting the formation of
oxatantalacyclopentene. In contrast, the reaction of 1a with the
dilithium salt of 1,4-bis(p-methoxyphenyl)-1,4-diaza-1,3-buta-
diene (abbreviated p-MeOC6H4-DAD) provided no isolable
species from a complicated reaction mixture.
The 1H and 13C NMR spectra of 5 displayed only two
methoxy groups of the p-MeOC6H4-DAD, indicating the
elimination of the methyl group of the ester. In the 13C NMR
spectrum, the carbonyl carbon was observed at δ 190.6, a higher
field shift than that of 1b. The IR spectrum of 5 exhibited ν-
(18) (a) Durfee, L. D.; Rothwell, I. P. Chem. ReV. 1988, 88, 1859, and
references are therein. For tantalum complexes: (b) Chamberlain, L. R.;
Steffey, B. D.; Rothwell, I. P.; Huffman, J. C. Polyhedron 1989, 8, 341.
(c) Koschmieder, S. U.; Hussain-Bates, B.; Hursthouse, M. B.; Wilkinson,
G. J. Chem. Soc., Dalton Trans. 1991, 2785. (d) Clark, J. R.; Fanwick, P.
E.; Rothwell, I. P. J. Chem. Soc., Chem. Commun. 1993, 1233. (e) Galakhov,
M. V.; Go´mez, M.; Jimenez, G.; Royo, P.; Pellinghelli, M. A.; Tiripicchio,
A. Organometallics 1994, 13, 1564. (f) Galakhov, M. V.; Go´mez, M.;
Jimenez, G.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A. Organometallics
1995, 14, 1901. (g) Galakhov, M.; Go´mez, M.; Jimenez, G.; Royo, P.;
Pellinghelli, M. A.; Tiripicchio, A. Organometallics 1995, 14, 2843. (h)
Bazan, G. C.; Rodriguez, G. Polyhedron 1995, 14, 93. (i) Clark, J. R.;
Fanwick, P. E.; Rothwell, I. P. Organometallics 1996, 15, 3232. (j) Go´mez,
M.; Go´mez-Sal, P.; Mart´ın, A.; Royo, P. Organometallics 1996, 15, 3579.
(k) Sa´nchez-Nieves, J.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A.
Organometallics 2000, 19, 3161.
The reaction of 1b with KN(SiMe3)2 did not proceed because
the â-methylene protons were protected by two methyl groups.
On the other hand, reaction of 1b with 1 equiv of the dilithium
salt of p-MeOC6H4-DAD afforded a tantalalactone complex,
(19) (a) Suh, S.; Hoffman, D. M. Inorg. Chem. 1996, 35, 5015. (b)
Gue´rin, F.; McConville, D. H.; Vittal, J. J.; Yap, G. A. P. Organometallics
1998, 17, 1290. (c) Araujo, J. P.; Wicht, D. K.; Bonitatebus, P. J.; Schrock,
R. R. Organometallics 2001, 20, 5682.
Cp*(η4-p-MeOC6H4-DAD)Ta(CH2CMe2C(dO)O) (5) (eq 4),
whose formulation was revealed by spectroscopic methods. The
(16) (a) Freundlich, J. S.; Schrock, R. R.; Cummins, C.; Davis, W. M.
J. Am. Chem. Soc. 1994, 116, 6476. (b) Mashima, K.; Fujikawa, S.; Tanaka,
Y.; Urata, H.; Oshiki, T.; Tanaka, E.; Nakamura, A. Organometallics 1995,
14, 2633. (c) Freundlich, J. S.; Schrock, R. R.; Davis, W. M. J. Am. Chem.
Soc. 1996, 118, 3643. (d) Gavenonis, J.; Tilley, T. D. Organometallics 2002,
21, 5549. (e) Gavenonis, J.; Tilley, T. D. Organometallics 2004, 23, 31.
(17) Turner, H. W.; Schrock, R. R.; Fellmann, J. D.; Holmes, S. J. J.
Am. Chem. Soc. 1983, 105, 4942.
(20) (a) Valero, C.; Grehl, M.; Wingbermu¨hle, D.; Kloppenburg, L.;
Carpenetti, D.; Erker, G.; Petersen, J. L. Organometallics 1994, 13, 415.
(b) Gerlach, C. P.; Arnold, J. J. Chem. Soc., Dalton Trans. 1997, 4795. (c)
Bashall, A.; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mountford, P.; Pugh,
S. M.; Radojevic, S.; Schubart, M.; Scowen, I. J.; Tro¨sch, D. J. M.
Organometallics 2000, 19, 4784.
(21) Radu, N. S.; Engeler, M. P.; Gerlach, C. P.; Tilley, T. D. J. Am.
Chem. Soc. 1995, 117, 3621.

3184 Organometallics, Vol. 25, No. 13, 2006
Tsurugi et al.
Table 3. Selected Bond Distances (Å) and Angles (deg) of
Complex 6
Ta-N1
2.038(2)
2.489(2)
2.256(2)
1.378(3)
1.381(3)
1.269(3)
1.520(3)
2.001(2)
1.996(3)
33.61(7)
84.69(8)
121.4(1)
119.2(2)
135.5(1)
Ta-N2
2.026(2)
2.478(2)
2.182(2)
1.391(3)
1.268(2)
1.544(3)
1.810(2)
2.003(2)
Ta-C11
Ta-C12
Ta-O3
Ta-C27
N1-C11
N2-C12
C31-O3
C27-C28
Al-O4
C11-C12
C31-O4
C28-C31
Al-C32
Al-C38
Al-C44
N1-Ta-C11
N1-Ta-N2
Ta-O3-C31
O3-C31-C28
Al-O4-C31
N2-Ta-C12
O3-Ta-C27
O3-C31-O4
O4-C31-C28
34.13(8)
85.09(8)
122.5(2)
118.3(2)
observed in oxatantallacycle complexes.8,18h,22,23 The same bond
distances of C(31)-O(3) [1.268(2) Å] and C(31)-O(4) [1.269-
(3) Å] and the sp2-hybridized C(31) [360.0° for the sum of the
angles around C(31)] represent a resonance structure of the
carboxyl group. The aluminum-oxygen bond distance [1.810-
(2) Å] is comparable to that of (C6F5)3Al(MMA) [1.811(2) Å],33
but shorter than that of (C6F5)3Al(THF) [1.860(2) Å],34 (C6F5)3-
Al(OH2) [1.857(3) Å],35 and (C6F5)3Al(OHCH3) [1.858(2) Å].35
The diazadiene ligand coordinated in an η4-supine fashion to
the tantalum atom, and the bond distances of Ta-C(11) [2.489-
(2) Å] and Ta-C(12) [2.478(2) Å] are short enough for the
tantalum atom to interact with the inner olefin carbons of the
diazadiene ligand.7b,36 Although a long-short-long sequence
of the diazadiene moiety was not clearly observed, the bond
distance of C(11)-C(12) [1.381(3) Å] was shorter than that of
the free ligand, s-trans-cyclohexyl-DAD [1.457(2) Å],37 and the
bond distances of N(1)-C(11) [1.378(3) Å] and N(2)-C(12)
[1.391(3) Å] were longer than those found for the s-trans-
cyclohexyl-DAD [1.258(2) Å].
Figure 3. Molecular structure of 6. All hydrogen atoms are omitted
for clarity.
(CO) at 1668 cm-1, consistent with those of metallalactone
complexes of early transition metals, Cp*2Ti(CH2CH2C(dO)-
O) (1653 cm-1),27 Cp2Zr(CH2CH2C(dO)O) (1687 cm-1),28 and
Cp*(η4-C4H6)Ta(C6H4C(dO)O) (1670 cm-1).29
Because the reaction of carbonyl compounds with strong
organo Lewis acids such as B(C6F5)3 and Al(C6F5)3 form stable
adducts,30,31 the addition of 1 equiv of organo Lewis acid, Al-
(C6F5)3, to tantalalactone 5 yielded a zwitterionic metallalac-
tone-Al(C6F5)3 adduct 6 (eq 5). In the 1H NMR spectrum, the
resonances of methylene protons and Cp* protons were shifted
upfield compared to those of 5. A downfield shifted carbonyl
carbon was observed by 13C NMR spectroscopy.
Preparation of Tungsten Homoenolate Complex and
Reactivity to 2,6-Dimethylphenylisocyanide. The zinc ho-
moenolates were versatile alkylation reagents and applicable
to prepare other transition metals.3e,h Treatment of [Et4N][(Xyl-
Nd)WCl5] with 0.5 equiv of Zn(CH2CH2CO2Et)2 in ether gave
a tungsten homoenolate complex, (Xyl-Nd)Cl3W(CH2CH2C-
(dO)OEt) (7), as dark red crystalline solids (eq 6). The chelating
structure of the homoenolate moiety was confirmed by NMR
1
and IR spectroscopy. The H NMR spectrum of 7 displayed
two triplet resonances (δ 4.08 and 2.27), assignable to the
methylene protons at the R- and â-positions of the homoenolate
moiety. The downfield shift of the carbonyl carbon resonance
(δ 194.9) compared to that of the carbonyl carbon resonance
of organic esters and the lower stretching frequency of the
carbonyl group (1620 cm-1) clearly indicated that the carbonyl
group of the homoenolate moiety coordinated to the tungsten
atom. The chemical shift value and the stretching frequency of
the carbonyl group were identical to those of 1a-c.
Recrystallization by slow evaporation of the solvent gave
single crystals suitable for X-ray diffraction study, and the
molecular structure of 6 was finally confirmed by X-ray analysis.
Figure 3 shows the molecular structure. Selected bond distances
and angles are summarized in Table 3. The single-crystal X-ray
diffraction study clearly demonstrated that tris(pentafluorophe-
nyl)alane is bound to the exocyclic oxygen atom of tantalalac-
tone and the carboxylate moiety bridges the tantalum and
aluminum atoms. A similar structure was reported by Chen et
al. for the zwitterionic zirconocene complex [rac-(EBI)ZrMe]-
[µ-OC(CHMe2)OAl(C6F5)3] (EBI ) C2H4(Ind)2).32 The bond
distance of Ta-O(3) [2.182(2) Å] is significantly elongated from
the tantalum-oxygen covalent bond distance (1.888-2.043 Å)
(22) Guggolz, E.; Ziegler, M. L.; Biersack, H.; Herrman, W. A. J.
Organomet. Chem. 1980, 194, 317.
(23) Kwon, D.; Curtis, M. D. Organometallics 1990, 9, 1.
(24) (a) Qian, Y.; Huang, J.; Yang, J.; Chan, A. S. C.; Chen, W.; Chen,
X.; Li, G.; Jin, X.; Yang, Q. J. Organomet. Chem. 1997, 547, 263. (b)
Huang, J.; Lian, B.; Qian, Y.; Zhou, W.; Chen, W.; Zheng, G. Macromol-
ecules 2002, 35, 4871.
We conducted a reaction of tungsten homoenolate 7 with an
excess of 2,6-dimethylphenylisocyanide to give 8, which

Tantalum and Tungsten Homoenolate Complexes
Organometallics, Vol. 25, No. 13, 2006 3185
Table 4. Selected Bond Distances (Å) and Angles (deg) of
Complex 8
W-N1
1.748(6)
2.444(2)
2.480(2)
2.171(8)
1.149(6)
170.8(2)
166.5(2)
174.8(3)
W-N2
W-Cl2
W-C9
N2-C9
2.119(7)
2.400(2)
2.131(8)
1.256(9)
W-Cl1
W-Cl3
W-C23
N3-C23
N1-W-Cl3
N2-W-Cl1
W-N1-C1
C23-W-Cl2
C9-W-Cl1
N3-C23-W
158.9(2)
154.9(2)
175.4(4)
Complex 8 adopts a pseudo-octahedral geometry around the
tungsten atom, where the imido nitrogen atom (N1) and the
η2-iminoacyl group occupy cis positions. Three chlorine atoms
are attached in a facial fashion to the tungsten atom. Complex
8 has a short bond distance of W-N(1) [1.748(6) Å] and a
linear angle of W-N(1)-C(1) [174.8(3)°], consistent with the
tungsten-nitrogen triple bond character.38 The bond distances
of W-N(2) [2.119(7) Å], W-C(9) [2.131(8) Å], and N(2)-
C(9) [1.256(9) Å] are consistent with a typical η2-iminoacyl
bond to early transition metals.18a,39 XylNC occupies a position
cis to the imido nitrogen atom N(1) and the η2-iminoacyl CdN
moiety. The bond distance of W-C(23) [2.171(8) Å] is longer
than that of the low-valent homoleptic tungsten complex,
W(CNXyl)6 (average: 2.05 Å).40 The elongated bond length of
W-C(23) is due to the lack of π-back-bonding from the metal
to the π* orbital of the isocyanide ligand, presumably because
of the strong π-bonding interaction between the tungsten atom
and the imido nitrogen atom. The oxygen atom (O1) of the ester
carbonyl moiety is outside the coordination sphere of the
tungsten atom, as predicted by the spectral data.
Figure 4. Molecular structure of 8. All hydrogen atoms and solvent
molecule are omitted for clarity.
possesses an η2-iminoacyl group and an η1-isocyanide ligand
(eq 7). Even in the presence of excess XylNC, further insertion
of XylNC did not proceed. The 13C NMR spectrum of 8
exhibited three resonances due to the iminoacyl carbon (δ
198.2), the carbonyl carbon (δ 170.6), and the isocyanide carbon
(δ 149.9). The chemical shift value of the iminoacyl carbon
was in the range of typical η2-iminoacyl moieties bound to early
transition metals.18a The chemical shift value of the carbonyl
carbon was consistently assigned to a noncoordinating carbonyl
group, and the resonance due to isocyanide indicated that
isocyanide coordinated in an η1-fashion to the tungsten atom.
Conclusion
We demonstrated that zinc homoenolates are versatile re-
agents for preparing tantalum and tungsten homoenolate com-
plexes. The isolated homoenolate complexes had a five-
membered chelating structure through the coordination of the
carbonyl oxygen of the homoenolate group to the metal. X-ray
analyses of tantalum complexes 1a and 1b revealed that the
carbonyl group of the homoenolate moiety was positioned at
the opposite side toward the Cp* ligand and the lone pair of
Complex 8 was isolated as yellow crystals, and the molecular
structure was determined by X-ray analysis (Figure 4). The
selected bond distances and angles are shown in Table 4.
2
the carbonyl oxygens overlapped with the empty dz orbital of
(25) (a) Yamamoto, T.; Igarashi, K.; Komiya, S.; Yamamoto, A. J. Am.
Chem. Soc. 1980, 102, 7448. (b) Yamamoto, T.; Sano, K.; Yamamoto, A.
J. Am. Chem. Soc. 1987, 109, 1092. (c) Aye, K.-T.; Colpltts, D.; Ferguson,
G.; Puddephatt, R. Organometallics 1988, 7, 1454. (d) Zlota, A.; Frolow,
F.; Milstein, D. Organometallics 1990, 9, 1300.
(26) (a) Hoberg, H.; Schaefer, D. J. Organomet. Chem. 1982, 236, C28.
(b) Hoberg, H.; Schaefer, D. J. Organomet. Chem. 1983, 251, C51. (c)
Hoberg, H.; Schaefer, D.; Burkhart, G.; Kru¨ger, C.; Roma˜o, M. J. J.
Organomet. Chem. 1984, 266, 203. (d) Hoberg, H.; Peres, Y.; Milchereit,
A. J. Organomet. Chem. 1986, 307, C38. (e) Hoberg, H.; Peres, Y.;
Milchereit, A. J. Organomet. Chem. 1986, 307, C41. (f) Braunstein, P.;
Matt, D.; Nobel, D. Chem. ReV. 1988, 88, 747.
(27) Cohen, S. A.; Bercaw, J. E. Organometallics 1985, 4, 1006.
(28) Alt, H. G.; Denner, C. E. J. Organomet. Chem. 1990, 390, 53.
(29) Mashima, K.; Tanaka, Y.; Nakamura, A. Organometallics 1995,
14, 5642.
(30) Parks, D. J.; Piers, W. E.; Parvez, M.; Atencio, R.; Zaworotko, M.
J. Organometallics 1998, 17, 1369.
(31) (a) Komon, Z. J. A.; Bu, X.; Bazan, G. C. J. Am. Chem. Soc. 2000,
122, 1830. (b) Lee, B. Y.; Bazan, G. C.; Vela, J.; Komon, Z. J. A.; Bu, X.
J. Am. Chem. Soc. 2001, 123, 5352.
(32) Bolig, A. D.; Chen, E. Y.-X. J. Am. Chem. Soc. 2004, 126, 4897.
(33) (a) Bolig, A. D.; Chen, E. Y.-X. J. Am. Chem. Soc. 2001, 123, 7943.
(b) Rodriguez-Delgado, A.; Chen, E. Y.-X. J. Am. Chem. Soc. 2005, 127,
961.
(34) Belgardt, T.; Storre, J.; Roesky, H. W.; Noltemeyer, M.; Schmidt,
H.-G. Inorg. Chem. 1995, 34, 3821.
(35) Chakraborty, D.; Chen, E. Y.-X. Organometallics 2003, 22, 207.
(36) Kawaguchi, H.; Yamamoto, Y.; Asaoka, K.; Tatsumi, K. Organo-
metallics 1998, 17, 4380.
the tantalum atom. As a result, the carbonyl oxygen of the
homoenolate moiety was tightly bound to the tantalum atom
and the metal-carbon bond of the homoenolate complexes
showed less reactivity toward insertion of unsaturated small
molecules, except for 2,6-dimethylisocyanide: 3 equiv of
isocyanide inserted consecutively into the Ta-C bond of 1a to
give 3a because the coordinated carbonyl moiety was released
by the first coordination of isocyanide. Similarly, tungsten
homoenolate complex 6 reacted with XylNC to give 8, which
had an η2-iminoacyl moiety and an η1-isocyanide ligand. The
reaction of 1a with KN(SiMe3)2 afforded the ethyl acrylate
complex 4a via the deprotonation reaction, while the reaction
of 1b with Li2(p-MeOC6H4-DAD)(thf)n resulted in the formation
of tantalalactone complex 5. The organo-Lewis acid Al(C6F5)3
reacted with the exocyclic carbonyl oxygen atom of 5 to form
the zwitterionic tantalum-aluminum adduct 6. The molecular
structure of 6, determined by X-ray diffraction study, indicates
(37) van Koten, G.; Vrieze, K. AdV. Organomet. Chem. 1982, 21, 151.
(38) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV. 1980, 31, 123.
(39) Huff, R. L.; Wang, S. S.; Abboud, K. A.; Boncella, J. M.
Organometallics 1997, 16, 1779.
(40) Lockwood, M. A.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1997, 16, 3574.

3186 Organometallics, Vol. 25, No. 13, 2006
Tsurugi et al.
Preparation of ICH2CMe2CO2C6H4CH3-4. To a mixture of
ICH2CMe2CO2H (29.22 g, 128.1 mmol) and (CF3CO)2O (20 mL,
0.14 mol) was added p-cresol (15 mL, 0.15 mol). The reaction
mixture was stirred overnight at room temperature. ICH2CMe2-
CO2C6H4CH3-4 was vacuum distilled out of the reaction mixture
that the carboxylate moiety of 6 interacted with both the
tantalum and aluminum atoms.
Experimental Section
1
as a colorless oil (18.5 g, 45% yield), bp 99 °C (0.1 mmHg). H
General Procedures. All manipulations involving air- and
moisture-sensitive organometallic compounds were operated using
the standard glovebox and Schlenk techniques under argon.
Complexes Cp*TaCl4,41 [Et4N][(Xyl-Nd)WCl5],42 Zn(CH2CH2CO2-
Et)2,3h IZn(CH2CMe2CO2Me),3e ICH2CMe2CO2H,43 Al(C6F5)3‚
NMR (300 MHz, CDCl3, 308 K): δ 7.19 (d, 2H, 3JH-H ) 8.9 Hz,
aromatic protons), 7.02 (d, 2H, 3JH-H ) 8.9 Hz, aromatic protons),
3.49 (s, 2H, ICH2), 2.37 (s, 3H, Ar-CH3), 1.51 (s, 6H, C(CH3)2);
13C NMR (75 MHz, CDCl3, 308 K): δ 173.0 (CdO), 148.4
(aromatic carbon), 135.3 (aromatic carbon), 129.7 (aromatic
carbons), 121.0 (aromatic carbons), 43.7 (C(CH3)2), 25.4 (C(CH3)2),
20.9 (Ar-CH3), 15.8 (ICH2). IR (Nujol): 1758 cm-1 (CdO). EI-
MS: m/z 318 ([M+]). HRMS: m/z calcd for C12H15O2I 318.0117,
found 318.0096.
(C7H8)0.5,
44 and 1,4-bis(p-methoxyphenyl)-1,4-diaza-1,3-butadiene45
were prepared according to the literature. AgOTf, B(C6F5)3, KN-
(SiMe3)2, and 2,6-dimethylphenylisocyanide were purchased and
used as received. Hexane, THF, toluene, and ether were dried and
deoxygenated by distillation over sodium benzophenone ketyl under
argon. Benzene-d6 was distilled from P2O5 and thoroughly degassed
by trap-to-trap distillation before use. Bromobenzene-d5 and
chloroform-d1 were distilled over CaH2 and then degassed. The 1H
(300 MHz) and 13C (75 Hz) NMR spectra were measured on a
Varian-Mercury-300 spectrometer. The elemental analyses were
recorded by using a Perkin-Elmer 2400 at the Faculty of Engineer-
ing Science, Osaka University. All melting points were measured
in sealed tubes under argon atmosphere and were not corrected.
Preparation of IZn(CH2CMe2CO2C6H4CH3-4). ICH2CMe2-
CO2C6H4CH3-4 (2.5 mL, 12.4 mmol) was added to a THF (8 mL)
suspension of activated zinc (0.976 g, 14.9 mmol, 1.2 equiv). After
the reaction mixture was stirred overnight at room temperature,
THF (20 mL) was added to the reaction mixture. After insoluble
materials were removed by centrifugation, the brown supernatant
was concentrated to give brown oil, which was extracted with ether
(80 mL). Ether was evaporated, and the resulting pale yellow oil
was washed with toluene (10 mL) and hexane (20 mL) to give
IZn(CH2CMe2CO2C6H4CH3-4) as white powder (1.98 g, 42% yield).
Preparation of Cp*Cl3Ta(CH2CH2C(dO)OEt) (1a). To a
suspension of Cp*TaCl4 (441 mg, 0.96 mmol) in ether (20 mL)
was added a solution of Zn(CH2CH2CO2Et)2 in ether (0.42 M, 1.4
mL, 0.59 mmol, 0.6 equiv) at -78 °C. The reaction mixture was
allowed to warm to room temperature and further stirred overnight
at room temperature. After all volatiles were removed under reduced
pressure, the residue was extracted with toluene (30 mL and then
20 mL). The combined toluene extract was concentrated under
reduced pressure to give 1a as yellow powders (320 mg, 64% yield),
3
1H NMR (300 MHz, CDCl3, 308 K): δ 7.17 (d, 2H, JH-H ) 8.4
3
Hz, aromatic protons), 6.94 (d, 2H, JH-H ) 8.4 Hz, aromatic
protons), 2.35 (s, 3H, Ar-CH3), 1.44 (s, 6H, C(CH3)2), 0.72 (s,
2H, ZnCH2). 13C NMR (75 MHz, CDCl3, 308 K): δ 189.0 (Cd
O), 148.7 (aromatic carbon), 136.0 (aromatic carbon), 130.0
(aromatic carbons), 120.6 (aromatic carbons), 45.1 (C(CH3)2), 30.3
(C(CH3)2), 26.9 (ZnCH2), 21.0 (Ar-CH3). IR (Nujol): 1681 cm-1
(CdO).
1
mp 193-200 °C (dec). H NMR (300 MHz, CDCl3, 308 K): δ
4.66 (q, 3JH-H ) 7.1 Hz, 2H, OCH2), 3.55 (t, 3JH-H ) 6.9 Hz, 2H,
Preparation of Cp*Cl3Ta(CH2CMe2C(dO)OC6H4CH3-4) (1c).
To a suspension of Cp*TaCl4 (829 mg, 1.82 mmol) in ether (20
mL) was added a solution of IZn(CH2CMe2CO2C6H4CH3-4) (697
mg, 1.82 mmol) in ether (15 mL) at -78 °C. The reaction mixture
was allowed to warm to room temperature and further stirred
overnight at room temperature. After all volatiles were removed
under reduced pressure, the residue was extracted with toluene (160
mL). Toluene was evaporated to give a yellow oil, which was
extracted with hexane (160 mL). The hexane extract was concen-
trated under reduced pressure, and the resulting yellow oil was
washed with hexane to give 1c as yellow powders (231 mg, 21%
3
TaCH2CH2), 2.43 (s, 15H, C5Me5), 1.47 (t, JH-H ) 7.1 Hz, 3H,
3
OCH2CH3), 0.65 (t, JH-H ) 6.9 Hz, 2H, TaCH2). 13C NMR (75
MHz, CDCl3, 308 K): δ 193.7 (s, CdO), 128.9 (s, C5Me5), 66.2
(t, 1JC-H ) 150 Hz, OCH2CH3), 62.7 (t, 1JC-H ) 127 Hz, TaCH2),
1
1
37.6 (t, JC-H ) 128 Hz, TaCH2CH2), 14.3 (q, JC-H ) 130 Hz,
1
OCH2CH3), 13.1 (q, JC-H ) 128 Hz, C5Me5). IR (Nujol): 1625
cm-1 (CdO). FAB-MS: m/z 487 (M+ - Cl). Anal. Calcd for
C15H24O2Cl3Ta: C, 34.40; H, 4.62. Found: C, 34.72; H, 4.93.
Preparation of Cp*Cl3Ta(CH2CMe2C(dO)OMe) (1b). A
solution of IZn(CH2CMe2CO2Me) (0.98 mmol, 1.2 equiv) in THF
(4.3 mL) was added to a suspension of Cp*TaCl4 (371 mg, 0.81
mmol) in ether (30 mL) cooled at -78 °C. The reaction mixture
was allowed to warm to room temperature and stirred overnight.
Solvent was evaporated under reduced pressure, and the resulting
yellow oil was extracted with hexane (60 mL). The hexane extract
was evaporated to give 1b as yellow microcrystals (159 mg, 36%
1
yield), mp 144-147 °C (dec). H NMR (300 MHz, CDCl3, 308
3
K): δ 7.33 (d, 2H, JH-H ) 8.5 Hz, aromatic protons), 7.20 (d,
2H, 3JH-H ) 8.5 Hz, aromatic protons), 2.42 (s, 15H, C5Me5), 2.34
(s, 3H, Ar-CH3), 1.41 (s, 6H, CMe2), 0.66 (s, 2H, TaCH2). 13C
NMR (75 MHz, CDCl3, 308 K): δ 195.3 (s, CdO), 148.8 (s, ipso-
1
Ar), 136.3 (para-Ar), 130.0 (d, JC-H ) 161 Hz, meta-Ar), 128.9
(s, C5Me5), 120.1 (d, 1JC-H ) 164 Hz, ortho-Ar), 82.0 (t, 1JC-H
)
1
120 Hz, TaCH2), 48.2 (s, TaCH2CMe2), 29.4 (q, 1JC-H ) 129 Hz,
yield), mp 172-179 °C (dec). H NMR (300 MHz, CDCl3, 308
TaCH2CMe2), 21.0 (q, 1JC-H ) 127 Hz, ArCH3), 13.2 (q, 1JC-H
)
K): δ 4.19 (s, 3H, OCH3), 2.41 (s, 15H, C5Me5), 1.23 (s, 6H,
CMe2), 0.57 (s, 2H, TaCH2). 13C NMR (75 MHz, CDCl3, 308 K):
129 Hz, C5Me5). IR (Nujol): 1649 cm-1 (CdO). FAB-MS: m/z
577 (M+ - Cl). Anal. Calcd for C22H30O2Cl3Ta: C, 43.05; H, 4.93.
Found: C, 43.38; H, 4.94.
1
δ 197.2 (s, CdO), 128.9 (s, C5Me5), 82.6 (t, JC-H ) 125.0 Hz,
TaCH2), 56.5 (q, 1JC-H ) 149.7 Hz, OCH3), 47.6 (s, TaCH2CMe2),
1
1
29.3 (q, JC-H ) 129.0 Hz, TaCH2CMe2), 13.1 (q, JC-H ) 129.0
Hz, C5Me5). IR (Nujol): 1633 cm-1 (CdO). FAB-MS: m/z 500
(M+ - Cl).
Preparation of Cp*Ta(CH2CH2C(dO)OEt)(OTf)3 (2a). To a
solution of 1a (76 mg, 0.15 mmol) in toluene (10 mL) at -78 °C
was added a solution of AgOTf (0.52 mmol, 3.6 equiv) in toluene
(4 mL). The reaction mixture was allowed to warm to room
temperature, and the reaction mixture was stirred overnight. After
the insoluble materials were removed by centrifugation, all volatiles
were evaporated to leave a yellow waxy solid. The solid was washed
with hexane (3 mL), and then solvent was evaporated to give 2a
as light yellow powders (94 mg, 75% yield), mp 115-123 °C (dec).
(41) Cardoso, A. M.; Clark, R. J. H.; Moorhouse, S. J. Chem. Soc., Dalton
Trans. 1980, 1156.
(42) Pederson, S. F.; Schrock, R. R. J. Am. Chem. Soc. 1982, 104, 7483.
(43) Kohn, M.; Schmidt, A. Monatsh. Chem. 1907, 28, 1055.
(44) Feng, S.; Roof, G. R.; Chen, E. Y.-X. Organometallics 2002, 21,
832.
(45) (a) Kliegman, J. M.; Barnes, R. K. Tetrahedron 1970, 26, 2555.
(b) Kliegman, J. M.; Barnes, R. K. J. Org. Chem. 1970, 35, 3140.
3
1H NMR (300 MHz, CDCl3, 308 K): δ 4.74 (q, JH-H ) 7.1 Hz,

Tantalum and Tungsten Homoenolate Complexes
Organometallics, Vol. 25, No. 13, 2006 3187
2H, OCH2), 3.81 (pseudo t, 3JH-H ) 7.0 Hz, 2H, TaCH2CH2), 2.54
toluene was removed. The resulting oil was treated with hexane (2
3
(s, 15H, C5Me5), 1.53 (pseudo t, JH-H ) 7.0 Hz, 2H, TaCH2),
mL) to give 5 as yellow-brown powders (203 mg, 83% yield), mp
3
1
1.42 (t, JH-H ) 7.1 Hz, 3H, OCH2CH3). 13C NMR (75 MHz,
148-160 °C (dec). H NMR (300 MHz, CDCl3, 308 K): δ 7.29
CDCl3, 308 K): δ 198.9 (s, CdO), 133.6 (s, C5Me5), 119.2 (q,
(d, 3JH-H ) 9.1 Hz, 2H, aromatic protons), 6.90 (m, 6H, aromatic
1
1JC-F ) 317 Hz, CF3), 118.8 (q, JC-F ) 317 Hz, 2C, CF3), 71.6
2
2
protons), 6.21 (d, JH-H ) 3.3 Hz, 1H, N-CH), 5.76 (d, JH-H
)
(t, 1JC-H ) 126 Hz, TaCH2), 70.4 (t, 1JC-H ) 153 Hz, OCH2CH3),
3.3 Hz, 1H, N-CH), 3.82 (s, 3H, OMe), 3.80 (s, 3H, OMe), 1.99
(s, 15H, C5Me5), 1.14 (s, 3H, CMe), 0.77 (s, 3H, CMe), 1.12 and
1
1
37.0 (t, JC-H ) 131 Hz, TaCH2CH2), 13.7 (q, JC-H ) 128 Hz,
OCH2CH3), 11.7 (q, 1JC-H ) 130 Hz, C5Me5). 19F NMR (282 MHz,
CDCl3, 308 K): δ -76.4 (s, 6F, OSO2CF3 cis to TaCH2), -77.8
(s, 3F, OSO2CF3 trans to TaCH2). IR (Nujol): 1587 cm-1 (CdO).
FAB-MS: m/z 715 (M+ - OTf). Anal. Calcd for C18H24S3O11F9-
Ta: C, 25.01; H, 2.80. Found: C, 25.03; H, 2.79.
2
0.68 (ABq, JH-H ) 13.5 Hz, 2H, TaCHH). 13C NMR (75 MHz,
CDCl3, 308 K): δ 190.6 (s, CdO), 156.9 (s, p-C6H4OCH3), 156.7
1
(s, p-C6H4OCH3), 143.4 (s, 2C, ipso-C6H4OCH3), 125.4 (d, JC-H
1
) 159.5 Hz, aromatic carbons), 124.7 (d, JC-H ) 160.1 Hz,
aromatic carbons), 118.5 (s, C5Me5), 113.8 (d, 1JC-H ) 159.5 Hz,
1
aromatic carbon), 113.7 (d, JC-H ) 159.5 Hz, aromatic carbon),
Preparation of Cp*Cl3Ta[N(Xyl)-C(dCdN-Xyl)-C(CH2-
1
1
109.4 (d, JC-H ) 176.2 Hz, N-CH)), 104.3 (d, JC-H ) 176.8
Hz, N-CH), 59.9 (br, TaCH2), 55.6 (q, 1JC-H ) 143.4 Hz, OCH3),
55.5 (q, 1JC-H ) 143.4 Hz, OCH3), 46.4 (s, CMe2), 32.9 (q, 1JC-H
CH2CO2Et)dN-Xyl] (3a). 2,6-Dimethyphenylisocyanide (111 mg,
0.85 mmol) was added to a solution of 1a (143 mg, 0.27 mmol) in
toluene (10 mL) at 0 °C. The reaction mixture was stirred overnight
at room temperature. The solvent was evaporated under reduced
pressure, and the resulting red waxy solid was washed with hexane
(5 mL) to give red precipitates, which were dried under reduced
pressure to give 3a as red powders (202 mg, 80% yield), mp 177-
185 °C (dec). 1H NMR (300 MHz, CDCl3, 308 K): δ 7.1-6.8 (m,
1
) 128.4 Hz, CMe), 30.7 (q, JC-H ) 130.7 Hz, CMe), 11.6 (q,
1JC-H ) 127.8 Hz, C5Me5). IR (Nujol): 1668 cm-1 (CdO), 1506
cm-1 (CdC). FAB-MS: m/z 684 (M+), 669 (M+ - CH3). Anal.
Calcd for C31H39N2O4Ta: C, 54.39; H, 5.74; N, 4.09. Found: C,
54.97; H, 6.02; N, 3.98.
Preparation of Cp*(p-MeOC6H4-DAD)Ta(CH2CMe2C(dO)-
O-Al(C6F5)3) (6). In a glovebox, toluene (5 mL) was added to a
mixture of 5 (115 mg, 0.17 mmol) and Al(C6F5)3(toluene)0.5 (99
mg, 0.17 mmol). The reaction mixture was stirred overnight, and
then toluene was evaporated. The resulting brown oil was washed
with hexane (5 mL) to give 6 as yellow-brown powders (135 mg,
66% yield), mp 226-234 °C (dec). Single crystals were obtained
by the slow evaporation of C6D6 from a NMR tube sample in a
3
9H, aromatic protons), 3.84 (q, JH-H ) 7.1 Hz, 2H, OCH2), 2.52
(s, 6H, CH3), 2.50 (m, 4H, CH2CH2), 2.39 (s, 6H, CH3), 2.12 (s,
3
6H, CH3), 2.06 (s, 15H, C5Me5), 1.01 (t, JH-H ) 7.1 Hz, 3H,
OCH2CH3). 13C NMR (75 MHz, CDCl3, 308 K): δ 172.9 (s), 171.1
(s), and 168.9 (s) (corresponding to CdN, CdO, and CdCdN),
152.4 (s, ipso), 147.6 (s, ipso), 137.4 (s, o-Xyl), 135.9 (s, o-Xyl),
134.7 (s, o-Xyl), 130.8 (s, ipso), 129.6 (d, 1JC-H ) 161 Hz, p-Xyl),
1
1
128.5 (d, JC-H ) 164 Hz, m-Xyl), 128.5 (d, JC-H ) 161 Hz,
glovebox. 1H NMR (300 MHz, C6D6, 308 K): δ 6.87 (d, 3JH-H
)
p-Xyl), 127.8 (d, 1JC-H ) 158 Hz, m-Xyl), 127.4 (s, C5Me5), 126.8
9.1 Hz, 2H, Ar), 6.80 (d, 3JH-H ) 8.5 Hz, 4H, Ar), 6.68 (d, 3JH-H
) 8.8 Hz, 2H, Ar), 6.26 (d, 1JH-H ) 3.0 Hz, 1H, N-CH), 5.40 (d,
1JH-H ) 3.0 Hz, 1H, N-CH), 3.46 (s, 3H, OMe), 3.41 (s, 3H,
OMe), 1.50 (s, 15H, C5Me5), 1.38 (s, 3H, CMe), 1.11 (s, 3H, CMe),
0.93 and 0.03 (ABq, 2JH-H ) 14.7 Hz, 2H, TaCH2). 13C NMR (75
MHz, C6D6, 298 K): δ 200.4 (s, CdO), 159.2 (s, p-C6H4OCH3),
158.8 (s, p-C6H4OCH3), 150.9 (d, 1JC-F ) 231 Hz, o-C6F5), 143.1
1
1
(d, JC-H ) 160 Hz, p-Xyl), 125.8 (d, JC-H ) 158 Hz, p-Xyl),
107.5 (s, CdCdN), 60.7 (t, 1JC-H ) 147 Hz, OCH2), 31.4 (t, 1JC-H
) 135 Hz, CH2), 27.8 (t, 1JC-H ) 127 Hz, CH2), 22.5 (q, 1JC-H
)
)
1
1
127 Hz, CH3), 20.1 (q, JC-H ) 127 Hz, CH3), 18.8 (q, JC-H
127 Hz, CH3), 14.1 (q, 1JC-H ) 127 Hz, OCH2CH3), 12.0 (q, 1JC-H
) 128 Hz, C5Me5). IR (Nujol): 2047 cm-1 (CdCdN), 1731 cm-1
(CdO), 1548 cm-1 (CdN). FAB-MS: m/z 880 (M+ - Cl). Anal.
Calcd for C42H51N3O2Cl3Ta: C, 55.00; H, 5.60; N, 4.58. Found:
C, 55.07; H, 5.92; N, 4.48.
(s, ipso-C6H4OCH3), 142.3 (s, ipso-C6H4OCH3), 142.0 (d, 1JC-F
)
1
250 Hz, p-C6F5), 137.7 (d, JC-F ) 268 Hz, m-C6F5), 127.0 (d,
1JC-H ) 158 Hz, o-C6H4OCH3), 126.2 (d, 1JC-H ) 161 Hz, o-C6H4-
OCH3), 120.5 (s, C5Me5), 114.6 (d, 1JC-H ) 160 Hz, m-C6H4OCH3),
Preparation of Cp*Cl2Ta(CH2CHdC(O)OEt) (4a). To a
suspension of 1a (401 mg, 0.77 mmol) in toluene (15 mL) at -78
°C was added a solution of KN(SiMe3)2 (0.90 mmol, 1.2 equiv) in
toluene (1.8 mL). The reaction mixture was allowed to warm to
room temperature and stirred further for 2 h. Removal of solvent
under reduced pressure afforded a red-brown residue, which was
extracted with hexane (30 mL). After insoluble materials were
removed by centrifugation, a clear solution was concentrated to
give 4a as purple microcrystals (224 mg, 60% yield), mp 96-103
°C. 1H NMR (300 MHz, CDCl3, 308 K): δ 4.92 (dd, 3JH-H ) 4.7
and 7.7 Hz, 1H, TaCH2CH), 4.12 (m, 1H, OCH2CH3), 2.26 (s, 15H,
1
1
114.1 (d, JC-H ) 161 Hz, m-C6H4OCH3), 108.1 (d, JC-H ) 181
Hz, N-CH), 107.8 (d, 1JC-H ) 182 Hz, N-CH), 55.8 (q, 1JC-H
143 Hz, OCH3), 55.5 (q, 1JC-H ) 144 Hz, OCH3), 55.5 (t, 1JC-H
)
)
119 Hz, TaCH2), 47.8 (s, CMe2), 33.8 (q, 1JC-H ) 130 Hz, CMe),
32.3 (q, 1JC-H ) 115 Hz, CMe), 11.8 (q, 1JC-H ) 128 Hz, C5Me5).
19F NMR (282 MHz, C6D6, 308 K): δ -123.7 (m, 6F, ortho),
3
-155.7 (t, JF-F ) 15.9 Hz, 3F, para), -163.1 (m, 6F, meta). IR
(Nujol): 1508 cm-1 (CdC). Anal. Calcd for C49H39N2O4F15AlTa:
C, 48.53; H, 3.24; N, 2.31. Found: C, 48.93; H, 3.45; N, 2.70.
Preparation of (Xyl-Nd)Cl3W(CH2CH2C(dO)OEt) (7). To
a suspension of [Et4N][(Xyl-Nd)WCl5] (3.109 g, 5.10 mmol) in
ether (30 mL) at -78 °C was added a solution of Zn(CH2CH2-
CO2Et)2 in ether (0.58 M, 5.0 mL, 2.88 mmol). The reaction mixture
was allowed to warm to room temperature and then stirred for 2 h.
All volatiles were removed, and the resulting residue was extracted
by hexane (60 mL × 4). The combined extract was concentrated
to give 7 as dark red crystalline solids (1.25 g, 48% yield), mp
3
1
C5Me5), 1.34 (t, JH-H ) 7.1 Hz, 3H, OCH2CH3), 1.32 (dd, JH-H
3
1
) 8.6 Hz, JH-H ) 7.7 Hz, 1H, TaCHH), 0.53 (dd, JH-H ) 8.6
Hz, JH-H ) 4.7 Hz, 1H, TaCHH). 13C NMR (75 MHz, CDCl3,
3
1
308 K): δ 161.8 (s, HCdC), 125.0 (s, C5Me5), 71.3 (d, JC-H
)
1
174 Hz, TaCH2CH), 67.0 (t, JC-H ) 147 Hz, TaCH2), 64.1 (t,
1JC-H ) 147 Hz, OCH2CH3), 14.8 (q, 1JC-H ) 127 Hz, OCH2CH3),
11.5 (q, 1JC-H ) 128 Hz, C5Me5). IR (Nujol): 1531 cm-1 (CdC).
FAB-MS: m/z 451 (M+ - Cl). Anal. Calcd for C15H23Cl2O2Ta:
C, 36.98; H, 4.76. Found: C, 37.12; H, 4.98.
1
85-89 °C (dec). H NMR (300 MHz, CDCl3, 308 K): δ 7.26 (d,
3
3JH-H ) 7.7 Hz, 2H, m-Ph), 6.68 (t, JH-H ) 7.7 Hz, 1H, p-Ph),
4.73 (q, 3JH-H ) 7.1 Hz, 2H, OCH2CH3), 4.08 (t, 3JH-H ) 6.6 Hz,
Preparation of Cp*(p-MeOC6H4-DAD)Ta(CH2CMe2C(dO)O)
(5). A solution of Li2(p-MeOC6H4-DAD) in THF (5.0 mL) was
added to a solution of 1b (185 mg, 0.34 mmol) in THF (10 mL)
cooled at -78 °C. After the reaction mixture was stirred overnight
at room temperature, all volatiles were removed under reduced
pressure. The residue was extracted with toluene (20 mL), and then
3
2H, WCH2CH2), 3.08 (s, 6H, ArCH3), 2.27 (t, JH-H ) 6.6 Hz,
3
2H, WCH2), 1.51 (t, JH-H ) 7.1 Hz, 3H, OCH2CH3). 13C NMR
(75 MHz, CDCl3, 308 K): δ 194.9 (s, CO2Et), 142.6 (o-Xyl), 131.6
1
1
(d, JC-H ) 160 Hz, p-Xyl), 126.3 (d, JC-H ) 161 Hz, m-Xyl),
1
1
66.7 (t, JC-H ) 148 Hz, OCH2CH3), 65.4 (t, JW-C ) 33.4 Hz,

3188 Organometallics, Vol. 25, No. 13, 2006
Table 5. Crystal Data and Data Collection Parameters of 1a, 1b, 3a, 6, and 8a,b
Tsurugi et al.
1a
1b
formula
fw
C15H24Cl3O2Ta
523.64
C16H26Cl3O2Ta
537.67
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21/c (No. 14)
8.6818(3)
13.6267(3)
14.9759(4)
orthorhombic
Pccn (No. 56)
25.7248(20)
21.1152(17)
8.6368(8)
R, deg
â, deg
γ, deg
V, Å3
Z
92.3894(14)
1770.17(8)
4
1.965
74492
1016
4691.4(7)
8
D
calcd, g/cm-3
1.522
38549
2096
50.30
120
no. of reflns for cell det
F(000)
µ [Mo KR], cm-1
T, K
66.63
120
cryst size, mm
2θmax, deg
0.22 × 0.10 × 0.06
0.21 × 0.15 × 0.05
60.08
55.0
no. of reflns measd
49 755
5165 (0.0261)
4890
65 872
5379 (0.2416)
3034
199
0.0679
0.1602
0.1383
0.1843
1.03
no. of unique data (Rint
)
no. of observns (I > 2.0σ(I))
no. of variables
R1 (I > 2.0σ(I))
wR2 (I > 2.0σ(I))
R1 (all data)
286
0.0132
0.0276
0.0152
0.0280
1.11
wR2 (all data)
GOF on F2
∆F, e Å-3
0.475, -0.406
1.936, -1.510
3a
6
8
formula
fw
C42H51Cl3N3O2Ta
917.19
C49H39O4N2F15AlTa
1212.76
C31H36Cl3N3O2W(C7H8)
864.99
cryst syst
space group
a, Å
b, Å
c, Å
triclinic
P1h (No. 2)
9.436(4)
11.148(4)
20.172(8)
76.47(3)
76.69(3)
80.30(3)
1992(1)
2
monoclinic
P21/c (No. 14)
11.646(1)
30.716(3)
14.1092(8)
monoclinic
P21/a (No. 14)
15.302(2)
12.380(2)
19.488(3)
R, deg
â, deg
γ, deg
V, Å3
Z
109.847(3)
93.025(6)
4747.4(6)
4
1.697
3686.5(8)
4
1.558
D
calcd, g/cm-3
1.528
no. of reflns for cell det
F(000)
39 014
928
29.94
120
111 001
2400
24.36
81 658
1736
33.91
µ [Mo KR], cm-1
T, K
120
120
cryst size, mm
2θmax, deg
0.20 × 0.15 × 0.05
0.40 × 0.65 × 0.10
0.20 × 0.25 × 0.05
55.0
55.0
54.8
no. of reflns measd
34 100
8987 (0.076)
7327
664
0.0360
0.0607
0.0523
0.0634
0.956
84 125
10865 (0.040)
9819
61 273
8276 (0.058)
6746
no. of unique data (Rint
)
no. of observns (I > 2.0σ(I))
no. of variables
R1 (I > 2.0σ(I))
wR2 (I > 2.0σ(I))
R1 (all data)
649
413
0.0229
0.0792
0.0268
0.0833
0.725
0.0353
0.1058
0.0472
0.1125
0.848
wR2 (all data)
GOF on F2
∆F, e Å-3
1.27, -1.79
0.90, -0.77
1.58, -1.56
2
2
4
a R1 ) (∑||Fo| - |Fc||)/(∑|Fo|). b wR2 ) [{∑w(Fo - Fc )2}/{∑w(Fo )}]1/2
.
1
1JC-H ) 132 Hz, WCH2), 37.9 (t, JC-H ) 130 Hz, WCH2CH2),
crystals (54 mg, 57% yield), mp 207-210 °C (dec). 1H NMR (300
MHz, CDCl3, 298 K): δ 7.33 (t, 3JH-H ) 7.7 Hz, 1H, p-Xyl), 7.25-
7.15 (m, 4H, m- and p-Xyl), 7.01 (d, 3JH-H ) 7.4 Hz, 3H, m-Xyl),
6.84 (t, JH-H ) 7.7 Hz, 1H, p-Xyl), 4.11 (ddd, JH-H ) 18.8 Hz,
3JH-H ) 6.8 and 9.1 Hz, 1H, CHHCO2Et), 4.0-3.7 (m, 3H,
CHHCO2Et and CO2CH2CH3), 2.90 (ddd, 2JH-H ) 17.8 Hz, 3JH-H
) 5.1 and 6.8 Hz, 1H, NdCCHH), 2.80-2.65 (1H, NdCCHH
overlapped with ArCH3 resonance), 2.75 (br s, 6H, ArCH3), 2.59
(s, 6H, ArCH3), 2.42 (s, 3H, ArCH3), 1.88 (s, 3H, ArCH3), 1.07 (t,
3JH-H ) 7.1 Hz, 3H, OCH2CH3). 13C NMR (75 MHz, CDCl3, 298
K): δ 198.2 (W-CdN), 170.6 (CdO), 149.9 (W-CNXyl), 136.5,
1
1
18.3 (q, JC-H ) 128 Hz, Ar-CH3), 14.1 (q, JC-H ) 128 Hz,
OCH2CH3). IR (Nujol): 1620 cm-1 (CdO). Anal. Calcd for
C13H18O2N1Cl3W: C, 30.59; H, 3.55; N, 2.74. Found: C, 30.53;
H, 3.63; N, 2.64.
Preparation of (Xyl-Nd)W{C(dN-Xyl)CH2CH2CO2Et}-
(CNXyl)Cl3 (8). To a solution of 7 (63 mg, 0.122 mmol) in toluene
(1 mL) was layered a solution of 2,6-dimethylphenylisocyanide
(40.5 mg, 0.309 mmol) in toluene (3 mL). Yellow crystals of 8
were formed after 3 days. The crystals were separated, washed with
hexane, and then dried under reduced pressure to give 8 as yellow
3
2

Tantalum and Tungsten Homoenolate Complexes
Organometallics, Vol. 25, No. 13, 2006 3189
134.2, 134.1, 132.4, 131.0, 129.3, 128.89, 128.85, 128.7, 128.5,
128.4, 128.1, 127.4 (br), 127.3 (br), 125.2, 61.4 (OCH2), 31.3, 29.5,
20.0 (ArCH3), 19.2 (ArCH3), 19.1 (ArCH3), 18.7 (ArCH3), 14.1
(OCH2CH3). IR (Nujol): 2210 cm-1 (CtN), 1773 cm-1 (CdN),
1726 cm-1 (CdO). FAB-MS: m/z 736 (M+ - Cl). Anal. Calcd
for C31H36O2N3Cl3W‚0.33(C7H8) (confirmed by integrated 1H NMR
spectrum): C, 49.82; H, 4.85; N, 5.23. Found: C, 49.94; H, 4.85;
N, 5.14.
X-ray Crystallography. All crystals were handled similarly. The
crystals were fixed on the end of glass fibers with heavy mineral
oil or inside a CryoLoop (Hampton Research Corp.) with heavy
mineral oil and placed in a nitrogen stream at 120(1) K. All
measurements were made on a Rigaku RAXIS-RAPID imaging
plate diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.71075). Indexing was performed from 3 or 4 oscillations,
which were exposed for the appropriate time for each crystal. The
camera radius was 127.40 mm. Readout was performed in the 0.100
mm pixel mode. For the data collection, reflections were measured
at a temperature of 120(1) K. Crystal data and structure refinement
parameters are summarized in Table 5.
matrix least-squares method, using SHELXL-97.49 Non-hydrogen
atoms were anisotropically refined, and all H atoms were isotro-
pically refined for 1a and 3a. Non-hydrogen atoms were anisotro-
pically refined, and all H atoms were included in the refinement
on calculated positions riding on their carrier atoms for 1b and 6.
For 8, most of the non-hydrogen atoms, except for the solvated
toluene molecule, were anisotropically refined and the rest were
refined isotropically. All H atoms were included in the refinement
on calculated positions riding on their carrier atoms. The ORTEP-3
program50 was used to draw the molecule.
Acknowledgment. One of the authors (H.T.) thanks the
Japan Society for the Promotion of Science (JSPS) research
fellowships for Young Scientists.
Supporting Information Available: CIF files giving crystal-
lographic data for 1a, 1b, 3a, 6, and 8. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM060264F
The structure of 1a and 1b were solved by direct methods
(SIR97).46 The structures of 3a and 6 were solved by direct methods
(SIR92).47 The structure of 8 was solved by direct methods
(SHELXS-97).48 All of the structures were refined on F2 by a full-
(47) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1994,
27, 435.
(48) Sheldrick, G. M. SHELXS-97, Programs for the Solution of Crystal
Structures; University of Go¨ttingen: Germany, 1997.
(46) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(49) Sheldrick, G. M. SHELXL-97, Programs for the Refinement of
Crystal Structures; University of Go¨ttingen: Germany, 1997.
(50) ORTEP-3: Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.