Alkylation and insertion reactions in dichloro azatantalacyclopropane complexes. X-ray crystal structures of [TaCpCl2{C(Ph)CHCMe 2NAr-κ2C,N}] (Cp = n5-C 5Me5, n5-C5H4SiMe 3; Ar = 2,6-Me2C6H3)

Article abstract of DOI:10.1021/om049110v

The alkylation and insertion reactions in dichloro azatantalacyclopropane complexes were analyzed. The ethylene and propene insertion reactions into the Ta-C bond of the azatantalacyclopropane system lead to dichloro azatantalacyclopropane complexes. A plausible decomposition process could consist in a β-hydrogen activation and a subsequent rupture of the Ta-C and N-C bonds into a concerted four-center transition state. The alkyne insertion reaction is faster and gives dichloro azatantalacyclopropane complexes which are more stable than the azatantalacyclopropane complexes due to the delocalization of the electronic density along the Ar-N-Ta-C=C bond system.

Full text of DOI:10.1021/om049110v

848
Organometallics 2005, 24, 848-856
Alkylation and Insertion Reactions in Dichloro
Azatantalacyclopropane Complexes. X-ray Crystal
Structures of [TaCpCl2{C(Ph)CHCMe2NAr-K2C,N}] (Cp )
η5-C5Me5, η5-C5H4SiMe3; Ar ) 2,6-Me2C6H3)§
Mikhail V. Galakhov,‡ Manuel Go´mez,*,† Pilar Go´mez-Sal,† and Patricia Velasco†
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´ de Henares, Campus
Universitario, E-28871 Alcala´ de Henares, Spain, and Centro de Espectroscopia de RMN,
Universidad de Alcala´ de Henares, Campus Universitario, E-28871 Alcala´ de Henares, Spain
Received November 17, 2004
Dichloro azatantalacyclopropane complexes [TaCpCl2(CMe2NAr-κ2C,N)] (Ar ) 2,6-Me2C6H3;
Cp ) η5-C5Me5, 1; η5-C5H4SiMe3, 2) can be obtained by treating TaCpCl2Me2 with 1 equiv of
2,6-dimethylphenylisocyanide. Alkylation of 1 with an excess of MgCl(CH2SiMe3) leads to
[TaCp*Cl(CH2SiMe3)(CMe2NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 3), which in
solution slowly decomposes to give [TaCp*Cl{C(Me)dCH2}(NAr)] (Cp* ) η5-C5Me5;
Ar ) 2,6-Me2C6H3, 4) with elimination of SiMe4. The same reaction with other alkylating
reagents takes place with the formation of 4, although we have not observed similar
intermediate monoalkyl derivatives. The complexes 1 and 2 react with ethylene to give the
dichloro azatantalacyclopentane compounds [TaCpCl2(CH2CH2CMe2NAr-κ2C,N)] (Ar ) 2,
6-Me2C6H3; Cp ) η5-C5Me5, 5; η5-C5H4SiMe3, 6). However, benzene-d6 solutions of 5 and 6
decompose at room temperature to give a dichloro(imido) tantalum complex [TaCpCl2(NAr)]
(Ar ) 2,6-Me2C6H3, Cp ) η5-C5Me5, 7;η5-C5H4SiMe3, 8) with elimination of 2-methyl-2-butene
(Me2CdCH-Me) and 3-methyl-1-butene (H2CdCH-CHMe2) (decomposition of 5) and only
2-methyl-2-butene (decomposition of 6). The complex [TaCp*Cl2{CH2CH(Me)CMe2NAr-
κ2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 9) was detected by NMR spectroscopy after
treatment of 1 with propylene in dichloromethane-d2. The analogous reaction of 1 or 2 with
alkynes RCtCH (R ) H, Ph, SiMe3) leads to the formation of the dichloro azatantalacyclo-
pentene complexes [TaCpCl2(CRCHCMe2NAr-κ2C,N)] (Ar ) 2,6-Me2C6H3; Cp ) η5-C5Me5,
R ) H, 10; Ph, 11; SiMe3, 12; Cp ) η5-C5H4SiMe3, R ) H, 13; Ph, 14; SiMe3, 15), the process
being regioselective when monosubstituted alkynes RCtCH (R ) Ph, SiMe3) were used. All
the new compounds were studied by IR and NMR spectroscopy, and the molecular structures
of complexes 11 and 14 were determined by X-ray diffraction methods.
Introduction
cyclopentadienyl) niobium and tantalum complexes
MCp*Cl4-xMex (M ) Nb, Ta; Cp* ) η5-C5Me5) in which
η2-iminoacyl (x ) 1), azametalacyclopropane (x ) 2, 3),
and (alkenylamido)imido (x ) 3, 4) derivatives were
isolated.
The chemistry associated with azametalacyclopropane
complexes has witnessed an important development,3
and although some group 5 metal η2-imine complexes
have been postulated as intermediates in organometallic
processes,4 only a few have been isolated.5 These
complexes can be accessible by cyclometalation of di-
The transfer of alkyl groups from transition metals
to coordinated isocyanides is one of the most relevant
organometallic reactions because the resulting metal-
iminoacyl functions are key and versatile reactive
intermediates in many synthetic applications. Especially
the use of transition metals as catalysts for achieving
coupling reactions which involve metalated species has
increased the use of heterocyclic organometallics in all
kinds of organic transformations.1 In this area, we have
reported the insertion processes2 of isocyanides into
metal-methyl bonds of chloro(methyl)(pentamethyl-
(2) (a) Galakhov, M. V.; Go´mez, M.; Jime´nez, G.; Royo, P.; Pelling-
helli, M. A.; Tiripicchio, A. Organometallics 1995, 14, 1901-1910.
(b) Galakhov, M. V.; Go´mez, M.; Jime´nez, G.; Royo, P.; Pellinghelli,
M. A.; Tiripicchio, A. Organometallics 1995, 14, 2843-2854. (c) Castro,
A.; Galakhov, M. V.; Go´mez, M.; Go´mez-Sal, P.; Mart´ın, A.; Sa´nchez,
F.; Velasco, P. Eur. J. Inorg. Chem. 2000, 2047-2054.
(3) (a) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J. C. J. Chem.
Soc., Chem. Commun. 1986, 1203-1205. (b) Sielisch, T.; Behrens, U.
J. Organomet. Chem. 1986, 310, 179-187. (c) Brunner, H.; Wachter,
J.; Schmidbauer, Organometallics 1986, 5, 2212-2219. (d) Durfee, L.
D.; Fanwick, P. E.; Rothwell, I. P. Folting, K.; Huffman, J. C. J. Am.
Chem. Soc. 1987, 109, 4720-4722. (e) Chamberlain, L. R.; Steffey, B.
D.; Rothwell, I. P.; Huffman, J. C. Polyhedron 1989, 8, 341-349.
(f) Durfee, L. D.; Hill, J. E.; Fanwick, P. E.; Rothwell, I. P. Organo-
metallics 1990, 9, 75-80.
§ This paper is dedicated to the daughter of Manuel Go´mez, Maria
Jesu´s, who was a victim of the March 11, 2004, tragedy in Madrid.
* To whom correspondence should be addressed. Fax:
34-91-885.46.83. E-mail: manuel.gomez@uah.es.
† Departamento de Qu´ımica Inorga´nica.
‡ Centro de Espectroscopia de RMN.
(1) (a) Abel, E. W.; Stone, F. G. A.; Wilkinson, G. Comprehensive
Organometallic Chemistry; Pergamon: Oxford, 1995. (b) Cornils, B.;
Herrmann, W. A. Applied Homogeneous Catalysis with Organometallic
Compounds; VCH: Weinheim, Germany, 1996. (c) Diederich, F.; Stang,
P. J. Metal-Catalyzed Croos-Coupling Reactions; Wiley-VCH: Wein-
heim, Germany, 1998. (d) Stanforth, S. P. Tetrahedron 1998, 54, 263-
303. (e) Beletskaya, I. P. Pure Appl. Chem. 2002, 74, 1327.
10.1021/om049110v CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/02/2005

Dichloro Azatantalacyclopropane Complexes
Organometallics, Vol. 24, No. 5, 2005 849
alkylamido ligands,4b,6 by alkyl or hydride reduction of
η2-iminoacyl ligands,3e,5e,7 by transfer of a hydrogen
atom from an amine-metal complex,5d and also by
addition of imines to low-valent metal derivatives.3b,c,8
Such η2-geometry has been identified in the crystal
structures of some imine tantalum,2a,c zirconium,7a,9 and
tungsten7b,c derivatives and also in the analogous oxo-
tantalacyclopropane complexes TaCp*X2(η2-OCMe2)
(Cp* ) η5-C5Me5; X ) Cl;4c Me2b), which exhibit a
bonding system through both the carbon and oxygen
atoms.
Scheme 1. Synthesis of Dichloro
Azatantalacyclopropane Complexes
On the other hand, nitrogen-containing molecules are
among the most important organic compounds basically
due to the biological activity10 of amino acids and
alkaloids. For the synthesis of these kinds of molecules,
allylamines are considered ideal building blocks, and
thus, many methods for the racemic and asymmetric
syntheses of allylamines11 have appeared in recent
years. In this context, Buchwald et al. described an
efficient method to prepare allylamine derivatives from
simple amines.12 This process relies on the formation
of an η2-imine zirconocene complex from an amide
methyl zirconocene and its entrapment with an alkyne
to give an azazirconacylopentene derivative, which
affords the desired allylamine on protic workup.13 This
sequence constitutes a powerful synthetic transforma-
tion since it accomplishes both a C-H activation and a
carbometalation process, reactions that are difficult to
achieve with conventional reagents.
alkylating reagents and their behavior in olefin and
acetylene insertion processes. All compounds were
studied by usual spectroscopic methods and the molec-
ular structure of some of them by X-ray diffraction.
Results and Discussion
Synthesis of Dichloro Azatantalacyclopropane
Complexes. The azatantalacyclopropane complexes
[TaCpCl2(CMe2NAr-κ2C,N)] (Ar ) 2,6-Me2C6H3; Cp )
η5-C5Me5, 1; η5-C5H4SiMe3, 2) were synthesized as
described, by addition of 1 equiv of 2,6-Me2C6H3NC to
a toluene solution of TaCpCl2Me2 (Cp ) η5-C5Me5;14 η5-
C5H4SiMe315) via migration of both methyl groups to the
As part of a program concerned with the development
of reactions involving monocylopentadienyl tantalum
complexes, we wish to report in this paper the results
observed when dichloro azatantalacyclopropane com-
plexes TaCpCl2(CMe2NAr-κ2C,N) (Ar ) 2,6-Me2C6H3;
Cp ) η5-C5Me5, 1; η5-C5H4SiMe3, 2) are treated with
1
isocyanide carbon atom (Scheme 1).2a The H and 13C-
{1H} NMR spectroscopic data (see Experimental Sec-
tion) for complex 2 are in accordance with the proposed
structure and also with the previous solution isom-
erization studies2a related to this type of compounds.
(4) (a) Takahashi, Y.; Onoyama, N.; Ishikawa, Y.; Motojima, S.;
Sugiyama, K. Chem. Lett. 1978, 525-528. (b) Mayer, J. M.; Curtis, C.
J.; Bercaw, J. E. J. Am. Chem. Soc. 1983, 105, 2651-2660. (c) Go´mez,
M.; Go´mez-Sal, P.; Jime´nez, G.; Mart´ın, A.; Royo, P.; Sa´nchez-Nieves,
J. Organometallics 1996, 15, 3579-3587.
Alkylation Reactions of Dichloro Azatantalacy-
clopropane Complexes. Reaction of a toluene solution
of the dichloro azatantalacyclopropane complex 1 at -78
°C with an excess of YCH2SiMe3 (Y ) MgCl, Li) afforded
the chloro trimethylsilylmethyl derivative [TaCp*Cl-
(CH2SiMe3)(CMe2NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar )
2,6-Me2C6H3, 3), which was isolated as a yellow solid
and characterized by elemental analysis and NMR
spectroscopy (Scheme 2). Complex 3 is thermally stable
in the solid state, but its benzene-d6 or toluene solutions
slowly decompose at room temperature, leading to the
imido 2-propenyl complex [TaCp*Cl{C(Me)dCH2}(NAr)]
(Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 4) with elimination
(5) (a) Neithamer, D. R.; Pa´rka´nyi, L.; Mitchell, J. F.; Wolczanski,
P. T. J. Am. Chem. Soc. 1988, 110, 4421-4423. (b) Strickler, J. R.;
Bruck, M. A.; Wigley, D. E. J. Am. Chem. Soc. 1990, 112, 2814-2816.
(c) Smith, D. P.; Strickler, J. R.; Gray, S. D.; Bruck, M. A.; Holmes, R.
S.; Wigley, D. E. Organometallics 1992, 11, 1275-1288. (d) Boncella,
J. M.; Cajigal, M. L.; Abboud, K. A. Organometallics 1996, 15, 1905-
1912. (e) Clark, J. R.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1996, 15, 3232-3237.
(6) Nugent, W. A.; Overall, D. W.; Holmes, S. J. Organometallics
1983, 2, 161-162.
(7) (a) Wolczanski, P. T.; Bercaw, J. E. J. Am. Chem. Soc. 1979, 101,
6450-6452. (b) Chiu, K. W.; Jones, R. A.; Wilkinson, G.; Galas, A. M.
R.; Hursthouse, M. B. J. Am. Chem. Soc. 1980, 102, 7979-7980.
(c) Chiu, K. W.; Jones, R. A.; Wilkinson, G.; Galas, A. M. R.;
Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1981, 2088-2097.
(8) (a) Roskamp, E. J.; Pedersen, S. F. J. Am. Chem. Soc. 1978, 109,
6551-6553. (b) Takai, K.; Ishiyama, T.; Yasue, H.; Nobunaka, T.; Itoh,
M.; Oshiki, T.; Mashima, K.; Tani, K. Organometallics 1998, 17, 5128-
5132.
1
of SiMe4, as confirmed by H NMR spectroscopy.
(14) Go´mez, M.; Jime´nez, G.; Royo, P.; Selas, J. M.; Raithby, P. R.
J. Organomet. Chem. 1992, 439, 147-154.
(9) Guram, A. S.; Swenson, D. C.; Jordan, R. F. J. Am. Chem. Soc.
1992, 114, 8991-8996.
(15) Synthesis of Ta(η5-C5H4SiMe3)Cl2Me2. A 2 M solution of ZnMe2
in toluene (1.09 mL, 2.10 mmol) was injected dropwise into a stirred
suspension of Ta(η5-C5H4SiMe3)Cl4 (1.00 g, 2.10 mmol) in toluene
(25 mL). The resultant brown suspension was stirred to room tem-
perature for 8 h. Afterwards, the brown suspension was filtered and
the solvent removed in a vacuum. The residue was extracted with
hexane (3 × 20 mL) and the solution concentrated to ca. 10 mL and
cooled to -40 °C to give yellow crystals of Ta(η5-C5H4SiMe3)Cl2Me2.
Yield: 0.70 g (78%). IR (KBr, νj cm-1): 2960(m), 1631(m), 1404(m),
1251(s), 1171(m), 1048(m), 908(w), 842(vs), 759(w), 699(w), 629(w), 498-
(w), 460(m), 420(w). 1H NMR (δ ppm, in benzene-d6): 5.99 (m, 2H),
5.59 (m, 2H, C5H4SiMe3), 1.28 (s, 6H, Ta-Me2), 0.135 (s, 9H, C5H4-
SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 125.08 (Ci, C5H4SiMe3),
120.95 (C2,5, C5H4SiMe3), 118.02 (C3,4, C5H4SiMe3), 72.05 (Ta-Me2), 0.85
(C5H4SiMe3). Anal. Calcd for C10H19Cl2SiTa: C, 28.65; H, 4.57.
Found: C, 28.81; H, 4.45.
(10) (a) Hetch, S. Bioinorganic Chemistry: Peptides and Proteins;
Oxford University Press: Oxford, 1998. (b) Hesse, M. Alkaloids:
Nature’s Curse or Blessing?; Wiley-CCH: New York, 2000.
(11) (a) Trost, B. M.; Radinov, R. J. Am. Chem. Soc. 1997, 119,
5962-5963. (b) Donde, Y.; Overman, L. E. J. Am. Chem. Soc. 1999,
121, 2933-2934. (c) Evans, P. A.; Robinson, J. E.; Nelson, J. D. J. Am.
Chem. Soc. 1999, 121, 6761-6762. (d) Ohmura, T.; Hartwig, J. F. J.
Am. Chem. Soc. 2002, 124, 15164-15165.
(12) (a) Buchwald, S. L.; Watson, B. T.; Wannamaker, M. W.; Dewan,
J. C. J. Am. Chem. Soc. 1989, 111, 4486-4494. (b) Grossman, R. B.;
Davis, W. M.; Buchwald, S. L. J. Am. Chem. Soc. 1991, 113, 2321-
2322.
(13) Coles, N.; Harris, M. C. J.; Whitby, R. J.; Blagg, J. Organo-
metallics 1994, 13, 190-199.

850 Organometallics, Vol. 24, No. 5, 2005
Galakhov et al.
Scheme 2. Alkylation of Dichloro
Azatantalacyclopropane Complexes
Scheme 4. Synthesis of Dichloro
Azatantalacyclopentane Complexes
589 cm-1, respectively, while complex 4 shows absorp-
tions assigned to the ν CdC4c,7b,c,18 and TadN19 stretch-
ing vibrations at νj 1585 and 1314 cm-1, respectively.
Scheme 3. Alkylation of Dichloro
Azatantalacyclopropane Complexes
1
The H NMR spectrum of 3 shows all the expected
resonances for the proposed structure with a chiral
1
metal center. In the H NMR spectrum of complex 4
appear two doublets of quartets at δ 5.83 (1H, 4J ) 1.5
4
Hz) and 4.96 (1H, J ) 1.2 Hz) (2J ) 0.6 Hz) and one
doublet of doublets at δ 2.46 (3H), corresponding to the
resonances of the 2-propenyl group bonded to the
tantalum atom in agreement with the value of the
1
carbon chemical shift δ 212.2. Moreover, the H NMR
spectra of complexes 3 and 4 show that the 2,6-
dimethylphenyl ring (δ Cipso ) 153) of the imido
susbtituent4c,20 possesses a C2v symmetry.
Synthesis of Dichloro Azatantalacyclopentane
Complexes. Complexes 1 and 2 react with ethylene
(1 atm) at room temperature in toluene to give, in good
yields, the azatantalacyclopentane complexes [TaCpCl2-
(CH2CH2CMe2NAr-κ2C,N)] (Ar ) 2,6-Me2C6H3; Cp ) η5-
C5Me5, 5; η5-C5H4SiMe3, 6), as result of an ethylene
insertion reaction into the Ta-C bond of the starting
azatantalacyclopropane derivatives (Scheme 4).
Both complexes were found to be air- and moisture-
sensitive but in the solid state and under a rigorously
dry inert gas atmosphere are stable for weeks. However,
toluene or benzene-d6 solutions of complexes 5 and 6
slowly and spontaneously decompose at room temper-
ature to give dichloro(imido) tantalum compounds
[TaCpCl2(NAr)] (Ar ) 2,6-Me2C6H3; Cp ) η5-C5Me5,
7;2a,21 η5-C5H4SiMe3, 822). When these reactions were
followed by 1H NMR spectroscopy in extremely dry
conditions, the elimination of 2-methyl-2-butene (Me2Cd
CH-Me) and 3-methyl-1-butene (Me2CH-CHdCH2) in
a 4:1 ratio (decomposition of 5) and only 2-methyl-2-
However, when complex 1 was treated with other
alkylating reagents such as MgR2(thf)2 (R ) CH2Ph,
CH2CMe3), MgClR, or LiR (R ) CH2CMe2Ph, CH2Ph,
CH2CMe3) in 1:1 or 1:2 molar ratios or even in excess,
complex 4 can be obtained with a similar yield, but the
formation of the intermediate alkyl chloro azatantala-
cyclopropane could not be verified. A similar treatment
of the trimethylsilylcyclopentadienyl derivative 2 led,
in all cases, to mixtures of unidentified species.
As ilustrated in Scheme 3, we suggest that the
formation of compound 4 takes place through a con-
certed transition state (A) by means of a C-H bond
activation of one of the two methyl groups with the
subsequent rearrangement and spontaneous elimina-
tion of the corresponding hydrocarbon. Similar ruptures
of the C(Me)-N(Ar) bond have been previously ob-
served2a,b in the formation of imido and alkenylamido
imido tantalum compounds by reaction of TaCp*Cl4-xMex
(Cp* ) η5-C5Me5; x ) 2, 3, 4) with 2 equiv of isocyanides.
The larger steric hindrance of the trimethylsilylmethyl
substituent makes it difficult to reach the concerted
transition state (A), and in agreement with this, we
observed the alkyl chloro azatantalacyclopropane com-
plex 3.
(17) (a) de Castro, I.; de la Mata, J.; Go´mez, M.; Go´mez-Sal, P.; Royo,
P.; Selas, J. M. Polyhedron 1992, 11, 1023-1027. (b) Castro, A.; Go´mez,
M.; Go´mez-Sal, P.; Manzanero, A.; Royo, P. J. Organomet. Chem. 1996,
518, 37-46. (c) Castro, A.; Galakhov, M. V.; Go´mez, M.; Go´mez-Sal,
P.; Mart´ın, A.; Sa´nchez, F. J. Organomet. Chem. 2000, 595, 36-53.
(18) (a) Curtis, M. D.; Thanedar, S.; Butler, W. M. Organometallics
1984, 3, 1855-1859. (b) Meyer, T. Y.; Garner, L. R.; Baenzinger, N.
C.; Messerle, L. W. Inorg. Chem. 1990, 29, 4045-4050.
(19) (a) Bradley, D. C.; Hursthouse, M. B.; Howes, A. J.; Jelfs, A. N.
de M.; Runnacles, J. D.; Thornton-Pett, M. J. J. Chem. Soc., Dalton
Trans. 1991, 841-847. (b) Williams, D. N.; Mitchell, J. P.; Poole, A.
D.; Siemeling, U.; Clegg, W.; Hockless, D. C. R.; O’Neil, P. A.; Gibson,
V. C. J. Chem. Soc., Dalton Trans. 1992, 739-751.
The IR spectrum of complex 3 shows the character-
istic absorptions due to the pentamethylcyclopenta-
dienyl ring,16 the trimethylsilyl substituent,2c,17 and the
Ta-C2a,17c bond at νj 1049 (νC-C), 1245 [δas(CH3)], and
(20) (a) Ting, C.; Messerle, L. J. Am. Chem. Soc. 1987, 109, 6506-
6508. (b) Matchett, S. A.; Norton, J. R.; Anderson, O. P. Organo-
metallics 1988, 7, 2228-2230.
(21) Galakhov, M. V.; Go´mez, M.; Jime´nez, G.; Royo, P.; Pellinghelli,
M. A.; Tiripicchio, A. Organometallics 1994, 13, 1564-1566.
(16) King, R. B.; Bisnette, M. B. J. Organomet. Chem. 1967, 8, 287-
297.

Dichloro Azatantalacyclopropane Complexes
Organometallics, Vol. 24, No. 5, 2005 851
Scheme 5. Decomposition of Dichloro
Azatantalacyclopentane Complexes
Scheme 6. Synthesis of Dichloro
Azatantalacyclopentene Complexes
an unresolved mixture of different species, from which
only the dichloro(imido)tantalum complex 72a,21 was
characterized. However, when the reaction of 1 with
butene (decomposition of 6) was detected. At room
temperature, the decomposition process is very slow in
the darkness but in the presence of light takes place
quickly and is complete after 5 h.
We suggest that a plausible decomposition process
could consist in a â-hydrogen activation and a subse-
quent rupture of the Ta-C and N-C bonds into a
concerted four-center transition state. So, the migration
of hydrogen to the R-CH2 carbon atom (i) leads to the
internal olefin (2-methyl-2-butene), while the migration
to the â-CMe2 carbon atom (ii) produces the terminal
olefin (3-methyl-1-butene) (see Scheme 5).
1
propylene in dichloromethane-d2 was monitored by H
NMR spectroscopy, the formation of the dichloro aza-
tantalacyclopentane complex [TaCp*Cl2{CH2CH(Me)-
CMe2NAr-κ2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3,
9) was proposed, in accord with the observation in the
tocsy1d spectrum of the resonances at δ -0.28 (dd, 1H,
2J ) 3.9 Hz, 3J ) 5.4 Hz), 0.27 (dd, 1H, 2J ) 3.9 Hz, 3J
) 8.44 Hz), 0.43 (ddq, 1H, 3J ) 5.4 Hz, 3J ) 8.44 Hz, 3J
3
) 6.03 Hz), and 0.93 (d, 3H, J ) 6.03 Hz) for the Ta-
CH2-CHMe-CMe2- moiety, respectively.
An unidentified mixture of several compounds was
obtained by treatment of the dichloro azatantalacyclo-
propane complex 2 with propylene. Attempts to synthe-
size new azatantalacyclopentane complexes using
2-butene, styrene, p-metoxiphenylethylene, and 1-meth-
oxy-2-phenylethylene were unsuccessful.
The analytical and spectroscopic data for complexes
5 and 6 are consistent with the expected four-legged
piano-stool geometry. IR spectra show the characteristic
absorptions of the pentamethylcyclopentadienyl (νjC-C
) 1023 cm-1 2c,16,17c
rings (νjC-H ) 839 cm-1 2c,17,23
)
and trimethylsilylcyclopentadienyl
and the trimethylsilyl
)
Synthesis of Dichloro Azatantalacyclopentene
Complexes. Dichloro azatantalacyclopropane com-
plexes 1 and 2 react quickly with alkynes RCtCH
(R ) H, Ph, SiMe3) at room temperature in toluene,
leading to the dichloro azatantalacyclopentene com-
plexes [TaCpCl2(CRCHCMe2NAr-κ2C,N)] (Ar ) 2,6-
Me2C6H3; Cp ) η5-C5Me5, R ) H, 10; Ph, 11; SiMe3, 12;
Cp ) η5-C5H4SiMe3, R ) H, 13; Ph, 14; SiMe3, 15), as
result of the insertion of the alkyne into the Ta-C bond
of the starting product (Scheme 6). All the complexes
10-15 are soluble in most organic solvents including
saturated hydrocarbons. They are extremely air- and
moisture-sensitive, so rigorously dried solvents and
handling under dry inert atmosphere were found to be
imperative for successful preparations. All of them were
isolated as microcrystalline solids in good yields and are
stable under argon atmosphere over a period of several
weeks. Further, complexes 10-15 are more stable than
the azatantalacyclopentane derivatives 5 and 6 proceed-
ing from the olefin insertion, probably due to their
higher electronic density delocalization.
substituent {νj [δas(CH3)] ) 1247 cm-1).2c,17,23 Absorp-
tions due to the C-N,24 Ta-N,24 and Ta-C2c,17,23
stretching vibrations are observed at νj 1179, 575, and
501 cm-1, respectively.
The NMR spectra (1H, 13C{1H}, tocsy1d, gHMQC) of
both complexes 5 and 6 (see Experimental Section) show
all the expected resonances for 2,6-dimethylphenyl and
cyclopentadienyl rings and an ABCD spin system for
the methylene groups of the Ta-CH2-CH2-CMe2-
moiety at δ 2.7, 2.08 (δ 13C ) 79.3) and 3.3, 2.16 (δ 13
C
) 43.73) (5), with typical values of the proton-proton
coupling constants. Moreover, the spectrum of complex
5 presents two signals for the methyl groups -CMe2-
that are in a very slow spin exchange process in
accordance with the 1H EXSY (noesy1d; mix time ) 500
ms) spectrum, while in complex 6 the rate of the spin
exchange is higher, in agreement with the observation
of only one broad resonance at δ 0.89 (δ 13C ) 27.47).
On the other hand, 1 reacts with propylene (1 atm)
at room temperature in benzene-d6 or toluene to give
(22) NMR spectroscopic data for [Ta(η5-C5H4SiMe3)Cl2{N(C6H3-
The spectroscopic and analytical data for the com-
plexes 10-15 are in agreement with the proposed
structures. The NMR spectra show the disappearance
of the signals for free acetylenes, a very large deshield-
ing of the proton (∆δ > 5) and carbon (∆δ > 100)
3
Me2)}], 8. 1H NMR (δ ppm, in benzene-d6): 6.96 (d, 2H, JH-H ) 7.5
3
Hz), 6.63 [t, 2H, JH-H ) 7.5 Hz, TadN(2,6-Me2C6H3)], 6.14 (m, 2H),
5.9 (m, 2H, C5H4SiMe3), 2.47 [s, 6H, TadN(2,6-Me2C6H3)], 0.15
(s, 9H, C5H4SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 153 (Ci),
135.4 (Co), 127.3 (Cp), 124.9 [Cm, TadN(2,6-Me2C6H3)], 124.5 (Ci), 121.5
(C2, 5), 112.9 (C3,4,C5H4SiMe3), 19.1 [TadN(2,6-Me2C6H3)], -0.75 (C5H4-
SiMe3).
(23) (a) Castro, A.; Galakhov, M. V.; Go´mez, M.; Sa´nchez, F. J.
Organomet. Chem. 1999, 580, 161-168. (b). Galindo, A.; Go´mez, M.;
del Rio, D.; Sa´nchez, F. Eur. J. Inorg. Chem. 2002, 1326-1335.
(c) Castro, A.; Galakhov, M. V.; Go´mez, M.; Go´mez-Sal, P.; Mart´ın, A.
Eur. J. Inorg. Chem. 2002, 1336-1342.
(24) Pretsch, E.; Clerc, T.; Seibl, J.; Simon, W. Tablas para la
elucidacio´n estructural de compuestos orga´nicos por me´todos espectro-
sco´picos; Alhambra: Madrid, 1980.
(25) (a) Smith, G.; Schrock, R. R.; Churchill, M. R.; Youngs, W. J.
Inorg. Chem. 1981, 20, 387-393. (b) Bianconi, P. A.; Williams, I. D.;
Engeler, M. P.; Lippard, S. J. J. Am. Chem. Soc. 1986, 108, 311-313.
(c) Bianconi, P. A.; Vrtis, R. N.; Rao, C. P.; Williams, I. D.; Engeler,
M. P.; Lippard, S. J. Organometallics 1987, 6, 1968-1977. (d) McGeary,
M. J.; Gamble, A. S.; Templeton, J. L. Organometallics 1988, 7, 271-
279. (e) Galindo, A.; Go´mez, M.; Go´mez-Sal, P.; Mart´ın, A.; del Rio,
D.; Sa´nchez, F. Organometallics 2002, 21, 293-304.

852 Organometallics, Vol. 24, No. 5, 2005
Galakhov et al.
1
Table 1. Selected H and 13C Chemical Shifts for
Complexes 10-15
R
Cpa
C1-H
C2-H
H
Cp*, 10
Cp′, 13
Cp*, 11
Cp′, 14
Cp*, 12
Cp′, 15
205/8.25
198.75/8.37
213.5/-
210/-
222.6/-
216.3/-
147.3/7.36
147.1/7.35
155.5/7.31
150.3/7.02
159.1/8.32
161.2/8.25
Ph
SiMe3
a Cp* ) η5-C5Me5. Cp′ ) η5-C5H4SiMe3.
resonances, and a decrease of the direct carbon-proton
coupling constant (∆J ≈ 100 Hz) values, in accord with
the hybridization change25 of the carbon atoms from sp
to sp2 due to the alkyne insertion reaction into the Ta-C
bond of the starting azatantalacyclopropane complexes.
The resonances due to C1-H and C2-H protons in
complexes 10 and 13 were assigned on the basis of their
correlations with corresponding carbon signals and by
a NOESY experiment. In the NMR spectra of complexes
11, 14 (R ) Ph) and 12, 15 (R ) SiMe3) we observed
only one set of the signals indicating the regioselectivity
of the insertion processes. The analysis of the proton
and carbon chemical shifts for the Ta-CRdCH-CMe2-
moiety did not allow the assignment of the SiMe3
position in complexes 12 and 15, since the experimental
values of δ (see Table 1) obtained from gHMQC and
gHMBC data indicate different positions. However, the
results of the noesy1d experiment show that the phenyl
(11, 14) and trimethylsilyl (12, 15) groups fill the closest
position to the cyclopentadienyl ring.
Figure 1. ORTEP drawing of compound 11.
This result reflects the pure electronic control, not
steric, in the insertion process of polarized unsaturated
molecules into the Ta-C bond of 1 and 2, which
probably takes place in the transition state of the
isomerization process in the starting azatantalacyclo-
propane complexes, as we have earlier proposed.2a
Unfortunately, the insertion of diphenylacetylene,
2-butyne, and tertbutylacetylene does not occur.
At room temperature, the 1H NMR spectra show some
very broad (∆ν1/2 > 50 Hz) for 13-15 and slightly broad
(∆∆ν1/2 ≈ 2 Hz) for 11, 12 resonances due to mutual spin
exchange between the -CMe2-, -N-C6H3Me2, and
C5H4SiMe3 resonances. This spectral behavior consists
in an interconversion process of two four-legged piano-
stool enantiomeric species with a trigonal bipyramidal
transition state with Cs symmetry (see Scheme 7). The
collapse point for -CMe2- resonances was found for
Figure 2. ORTEP drawing of compound 14.
Ta-N (values 2.010(10) Å for 11 and 1.995(4) Å for 14)
and between the carbon atoms R and â with respect to
the tantalum atom (C18-C17 1.338(16) Å for 11 and
C6-C7 1.320(6) Å for 14). The distance Ta-CR (Ta-
C18 2.219(10) Å in 11 and Ta-C6 2.207(4) Å in 14) is
typical for a single bond. The azatantalacyclopentene
ring is fairly planar, the corresponding fold angle being
defined between the N(1), Ta(1), CR and N(1), CR, Câ,
Câ′ planes as 15.6(4)° and 14.5(1)°, respectively.
Although in the literature there have been reported
a few azatantalacycles, the bonding situation found is
different from that observed in complexes 11 and 14.
So, in the complex [TaCpMe{C(Ph)C(Ph)C(Me)N(tBu)}]
(Cp ) η5-C5H5)26 the TaC3N ring is folded 120° and the
Ta-C and Ta-N distances in the metallacycle are both
1.98(1) Å and are commensurate with TadC and Tad
N double bonds. So, the authors suggest that the ring
structure is a derivative of a metallacyclopentatriene.
On the other hand, the complexes [TaCp*Cl2(supine-
complexes 13 (∆G#236.2K
) 50.6 kJ‚mol-1) and 15
col
(∆G#307K
) 63.5 kJ‚mol-1). The same process was
col
observed for complexes 5 and 6.
The molecular structures of compounds 11 and 14
were determined by X-ray diffraction methods and are
shown in the Figures 1 and 2, while selected bond
distances and angles are presented in Tables 2 and 3,
respectively. In the crystals of these compounds, one
molecule of benzene (11) and toluene (14) solvate is
present for each complex molecule.
Both complexes 11 and 14 can be described as
monomers with a typical four-legged piano-stool envi-
ronment for the tantalum atom, with a cyclopentadienyl
ring in the cap position and the legs defined by two
chlorine, the nitrogen, and one carbon atom included
in an azatantalacyclopentene unit TaC3N, in which the
bonding corresponds to a diene with a double bond
(26) (a) Curtis, M. D.; Real, J. J. Am. Chem. Soc. 1986, 108, 4668-
4669. (b) Curtis, M. D.; Real, J.; Hirpo, W.; Butler, W. M. Organo-
metallics 1990, 9, 66-74.

Dichloro Azatantalacyclopropane Complexes
Organometallics, Vol. 24, No. 5, 2005 853
Scheme 7. Isomerization Process in Azatantalacyclopentene Complexes
Table 2. Selected Bond Lengths [Å] and Angles
[deg] for Compound 11
both ring planes of 40.9(1)°, in agreement with the
different steric hindrance of the cyclopentadienyl moi-
eties.
Ta(1)-N(1)
Ta(1)-Cl(2)
Ta(1)-C(11)
Ta(1)-C(13)
Ta(1)-C(15)
N(1)-C(16)
C(17)-C(18)
2.010(10)
2.366(3)
2.494(12)
2.408(11)
2.535(12)
1.527(15)
1.338(16)
Ta(1)-C(18)
Ta(1)-Cl(1)
Ta(1)-C(12)
Ta(1)-C(14)
N(1)-C(25)
C(16)-C(17)
C(18)-C(19)
2.219(10)
2.441(3)
2.491(11)
2.458(12)
1.481(14)
1.493(15)
1.516(15)
Conclusions
In this paper we report a study of the alkylation and
insertion reactions in dichloro azatantalacyclopropane
complexes. So, a stable 16-electron chloro(imido) 2-pro-
penyl compound [TaCp*Cl{C(Me)dCH2}(NAr)] (Cp* )
η5-C5Me5; Ar ) 2,6-Me2C6H3, 4) is obtained by treating
the dichloro azatantalacyclopropane complex 1 with
different alkylating reagents with elimination of a
hydrocarbon and via intermediate alkyl chloro azatan-
talacyclopropane species [TaCp*ClR(CMe2NAr-κ2C,N)]
characterized for R ) CH2SiMe3, 3. The ethylene and
propene insertion reactions into the Ta-C bond of the
azatantalacyclopropane system lead to dichloro azatan-
talacyclopentane complexes [TaCpCl2{CH2CH(R)CMe2-
NAr-κ2C,N}] (Cp ) η5-C5Me5, R ) H, 5; Me, 9; Cp )
η5-C5H4SiMe3, R ) H, 6), being a regioselective and very
slow process in the case of the propene insertion.
However, complexes 5 and 6 decompose in benzene-d6
or toluene solutions at room temperature, leading to a
dichloro(imido)tantalum compound [TaCpCl2(NAr)]
(Cp ) η5-C5Me5, 7; η5-C5H4SiMe3, 8) with elimination
of 2-methyl-2-butene and 3-methyl-1-butene (decompo-
sition of 5) and only 2-methyl-2-butene (decomposition
of 6). The alkyne insertion reaction is faster and gives
dichloro azatantalacyclopentene complexes [TaCpCl2-
(CRCHCMe2NAr-κ2C,N)] (Cp ) η5-C5Me5, R ) H, 10;
Ph, 11; SiMe3, 12; Cp ) η5-C5H4SiMe3, R ) H, 13; Ph,
14; SiMe3, 15), which are more stable than the azatan-
talacyclopentane complexes due to the delocalization of
the electronic density along the Ar-N-Ta-CdC bond
system. Further, the monosubstitued alkyne insertion
reaction is regiospecific and takes place with the forma-
tion of the unitary products 11, 12, 14, and 15 with the
phenyl and trimethylsilyl groups oriented to the cyclo-
pentadienyl ring, as confirmed by the corresponding
structural studies.
N(1)-Ta(1)-C(18)
C(18)-Ta(1)-Cl(2)
C(18)-Ta(1)-Cl(1)
76.7(4)
88.2(3)
152.3(3)
N(1)-Ta(1)-Cl(2)
N(1)-Ta(1)-Cl(1)
Cl(2)-Ta(1)-Cl(1)
113.4(3)
82.4(3)
83.6(1)
Table 3. Selected Bond Lengths [Å] and Angles
[deg] for Compound 14
Ta(1)-N(1)
Ta(1)-Cl(1)
Ta(1)-C(1)
Ta(1)-C(3)
Ta(1)-C(5)
Si(6)-C(25)
Si(6)-C(27)
N(1)-C(8)
C(6)-C(19)
1.995(4)
2.346(1)
2.504(5)
2.381(4)
2.479(4)
1.848(6)
1.846(5)
1.521(6)
1.496(6)
Ta(1)-C(6)
Ta(1)-Cl(2)
Ta(1)-C(2)
Ta(1)-C(4)
Si(6)-C(1)
Si(6)-C(26)
N(1)-C(9)
C(6)-C(7)
C(7)-C(8)
2.207(4)
2.413(1)
2.403(4)
2.411(4)
1.901(5)
1.873(5)
1.457(5)
1.320(6)
1.483(6)
N(1)-Ta(1)-Cl(1)
C(6)-Ta(1)-Cl(1)
C(6)-Ta(1)-Cl(2)
119.8(1)
85.4(1)
150.5(1)
N(1)-Ta(1)-C(6)
N(1)-Ta(1)-Cl(2)
Cl(1)-Ta(1)-Cl(2)
76.1(2)
84.9(1)
84.7(1)
R2-AD)] (Cp* ) η5-C5Me5; R2-AD ) 1,4-diphenyl-1-aza-
1,3-butadiene;27a 1-o-tolyl-4-phenyl-1-aza-1,3-butadiene27b
)
exhibit a similar structure with typical double bond
TadN (2.010(7) Å) and CâdCâ′ (1.39(1) Å) distances. The
TaC3N ring presents an important folding effect of
103.8(3)° but smaller than in the case mentioned above.
Further, the three carbon atoms of the cycle have
similar bond distances (ranging from 2.322(8) Å for CR
to 2.437(9) Å for Câ), and due to this, the AD ligand
coordinates to the tantalum atom with the contribution
of the η1-N-η3-allyl canonical form. In our case, the lack
of a π-bonding interaction between the metal center and
the three carbon atoms of the cycle is also confirmed by
a reinforcement of the Ta-Cl bond trans to the nitrogen
atom. Both structures show very short Ta-Cl2 (2.366-
(3) Å in 11) and Ta-Cl1 (2.346(1) Å in 14) bond
distances.
The 2,6-Me2C6H3 ring bonded to the nitrogen atom is
located in both structures quasi perpendicular to the
cyclopentadienyl ring plane (62.1(4)° in 11 and 71.8(1)°
in 14), while the phenyl ring bonded to the carbon atom
exhibits a very different position, being in complex 11
fairly parallel to the pentamethylcyclopentadienyl ring
(10.6(4)°) and in complex 14 bending toward the tri-
methylsilylcyclopentadienyl ring with an angle between
Experimental Section
All operations were carried out under a dry argon atmo-
sphere using standard Schlenk-tube and cannula techniques
or in a conventional argon-filled glovebox. Solvents were
refluxed over an appropriate drying agent and distilled and
degassed prior to use: benzene-d6 and hexane (Na/K alloy) and
toluene (Na). Starting materials Ta(η5-C5H4SiMe3)Cl4,28 Ta-
(η5-C5H4SiMe3)Cl2Me2,15 [Ta(η5-C5Me5)Cl2{CMe2N(2,6-Me2C6H3)-
(27) (a) Mashima, K.; Matsuo, Y.; Nakahara, S.; Tani, K. J.
Organomet.Chem. 2000, 593-594, 69-76. (b) Matsuo, Y.; Mashima,
K.; Tani, K. Bull. Chem. Soc. Jpn. 2002, 75, 1291.
(28) Go´mez, M.; Royo, P.; Selas, J. M. J. Organomet. Chem. 1986,
314, 131-138.

854 Organometallics, Vol. 24, No. 5, 2005
Galakhov et al.
κ2C,N}],2a and Mg(CH2Ph)2(thf)229 were prepared as described
previously. Reagent grade C2H4 (Air L´ıquide), H2CdCH-CH3
(Air L´ıquide), C2H2 (Air L´ıquide), RCtCH (R ) Ph, SiMe3,
Aldrich), MgCl(CH2SiMe3) (1 M in diethyl ether, Aldrich),
ZnMe2 (2 M in toluene, Aldrich), and 2,6-Me2C6H3NC (Fluka)
were purchased from commercial sources and were used
without further purification.
Samples for infrared spectroscopy were prepared as Nujol
mulls between CsI pellets or in KBr pellets and recorded on a
Perkin-Elmer Spectrum 2000 spectrophotometer (4000-400
cm-1). 1H and 13C{1H} NMR spectra were recorded on a Unity-
300 and/or Unity Plus-500 (Varian) spectrometer; chemical
shifts were referenced to the 13C (δ ) 128) and residual 1H
(δ ) 7.15) resonances of the benzene-d6 solvent. Microanalyses
(C, H, N) were performed in a Heraeus CHN-O-Rapid micro-
analyzer.
hexane (3 × 10 mL). The solution was filtered, concentrated
to ca. 10 mL, and cooled to -40 °C to give 4 as a yellow
microcrystalline solid. Yield: 0.25 g (54%).
4 can be isolated with a similar yield by treatment of 1 with
Mg(CH2CMe3)2(thf)2, MgClR (R ) CH2CMe2Ph, CH2Ph, CH2-
CMe3). and/or LiR (R ) CH2CMe2Ph, CH2Ph, CH2CMe3) in a
1:1 or 1:2 molar ratio or in excess. Alternatively, the benzene-
d6 or toluene solution of complex 3 slowly decomposes at room
temperature to give 4 in good yield.
The data for 4 follow. IR (Nujol mull, νj cm-1): 1588(m),
1545(m), 1415(m), 1314(vs), 1285(w), 1158(m), 1137(m), 1095-
(m), 1025(m), 982(m), 930(m), 902(s), 799(m), 757(s), 624(m),
590(w), 450(w), 440(w). 1H NMR (δ ppm, in benzene-d6): 7.03
[d, 2H, 3JH-H ) 7.6 Hz], 6.72 [t, 1H, 3JH-H ) 7.6 Hz, Ta-N(2,6-
Me2C6H3)], 5.83 (dq, 1H, 4JH-H ) 1.5 Hz, 2JH-H ) 0.6 Hz), 4.96
4
2
[dq, 1H, JH-H ) 1.2 Hz, JH-H ) 0.6 Hz, Ta-C(Me)dCH2],
2.55 [s, 6H, Ta-N(2,6-Me2C6H3)], 2.46 [dd, 3H, 4JH-H ) 1.5;1,
2 Hz, Ta-C(Me)dCH2], 1.77 (s, 15H, C5Me5). 13C{1H} NMR
(δ ppm, in benzene-d6): 212.2 [Ta-C(Me)dCH2], 153.1 (Ci),
134.6 (Co), 127.6 (Cm), 123.1 [Cp, Ta-N(2,6-Me2C6H3)], 118.7
[Ta-C(Me)dCH2], 118.5 (C5Me5), 34 [Ta-C(Me)dCH2], 20
[Ta-N(2,6-Me2C6H3)], 11.2 (C5Me5). Anal. Calcd for C21H29-
ClNTa: C, 47.27; H, 5.71; N, 2.73. Found: C, 47.36; H, 5.81;
N, 2.70.
Synthesis of [Ta(η5-C5H4SiMe3)Cl2(CMe2NAr-K2C,N)]
(Ar ) 2,6-Me2C6H3, 2). A yellow solution of Ta(η5-C5H4-
SiMe3)Cl2Me2 (1.00 g, 2.38 mmol) in toluene (60 mL) was
treated with 2,6-Me2C6H3NC (0.31 g, 2.38 mmol) under rigor-
ously anhydrous conditions for 2 h. The solution was filtered,
concentrated to ca. 10 mL, and cooled to -40 °C to give 2 as
garnet crystals.
The data for 2 follow. Yield: 1.05 g (81%). IR (KBr, νj cm-1):
2947(m), 1456(s), 1400(m), 1371(m), 1274(s), 1247(s), 1193-
(m), 1173(s), 1104(m), 1039(m), 906(s), 839(vs), 762(s), 631-
(m), 576(w), 512(w), 420(m). 1H NMR (δ ppm, in benzene-d6):
7.09 (d, 2H, 3JH-H ) 7.5 Hz), 6.95 [t, 1H, 3JH-H ) 7.5 Hz, Ta-
N(2,6-Me2C6H3)-], 6.21 (m, 2H), 5.86 (m, 2H, C5H4SiMe3), 2.23
[s, 6H, Ta-N(2,6-Me2C6H3)-], 2.20(s, 6H, Ta-CMe2-), 0.28
(s, 9H, C5H4SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6):
151.6 (Ci), 134.1 (Co), 129.2 (Cm), 125.7 [Cp, Ta-N(2,6-
Me2C6H3)-], 125.2 (Ci), 124.7 (C2,5), 112.1 (C3,4, C5H4SiMe3),
90.6 (Ta-CMe2-), 30.7 (Ta-CMe2-), 20.2 [Ta-N(2,6-
Me2C6H3)-], -0.2 (C5H4SiMe3). Anal. Calcd for C19H28Cl2-
NSiTa: C, 41.46; H, 5.13; N, 2.55. Found: C, 41.31; H, 5.01;
N, 2.63.
Synthesis of [TaCpCl2(CH2CH2CMe2NAr-K2C,N)] (Ar )
2,6-Me2C6H3; Cp ) η5-C5Me5, 5; η5-C5H4SiMe3, 6). A solution
of 1 or 2 (1.00 g, 1.81 mmol) in toluene (40 mL) was placed
into a Schlenk tube and the argon atmosphere replaced by
ethylene (1 atm). Under rigorously anhydrous conditions the
solution was stirred for 2 h and the resulting reddish solution
was concentrated to ca. 10 mL and cooled overnight at
-40 °C to yield 5 or 6 as red microcrystalline solids.
The data for 5 follow. Yield: 0.68 g (65%). IR (KBr, νj cm-1):
2910(vs), 1646(w), 1586(w), 1452(vs), 1376(s), 1258(m), 1172-
(vs), 1147(s), 1098(s), 1073(m), 1023(s), 949(m), 864(m), 796-
(w), 765(s), 596(w), 524(w), 492(w). 1H NMR (δ ppm, in
benzene-d6): 7.05 (d, 2H,3JH-H ) 7.5 Hz), 6.92 [t, 1H, 3JH-H
)
Synthesis of [TaCp*Cl(CH2SiMe3)(CMe2NAr-K2C,N)]
(Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 3). A 1 M solution of
MgCl(CH2SiMe3) in OEt2 (2.00 mL, 2.40 mmol) was added at
-78 °C to a solution of 1 (0.50 g, 0.91 mmol) in toluene
(30 mL), and the mixture was stirred for 30 min. It was
warmed to room temperature for 12 h, the solvent was
removed in vacuo, and the residue was extracted into hexane
(3 × 10 mL). The solution was concentrated to ca. 10 mL and
cooled to -40 °C overnight to give 3 as a yellow microcrystal-
line solid.
7.5 Hz, Ta-N(2,6-Me2C6H3)-], 3.30 (m, 1H, -CH2-CMe2-),
3.10 [s, 3H, Ta-N(2,6-Me2C6H3)-], 2.70 (m, 1H, Ta-CH2-),
2.16 (m, 1H, -CH2-CMe2-), 2.08 (m, 1H, Ta-CH2-), 2.07
[s, 3H, Ta-N(2,6-Me2C6H3)], 1.96 (s, 15H, C5Me5), 1.08 (s, 3H,
-CH2-CMe2-), 0.81 (s, 3H, -CH2-CMe2-). 13C{1H} NMR
(δ ppm, in benzene-d6): 158.92 (Ci), 128.74 (Co), 127.45 (Cm),
124.64 [Cp, Ta-N(2,6-Me2C6H3)], 126.08 (C5Me5), 79.38 (Ta-
CH2-), 78.03 (-CH2-CMe2-), 43.73 (-CH2-CMe2-), 30.45,
26.94 (-CH2-CMe2-), 22.94, 21.23 [Ta-N(2,6-Me2C6H3)-],
12.40 (C5Me5). Anal. Calcd for C23H34Cl2NTa: C, 47.93; H,
5.95; N, 2.43. Found: C, 47.86; H, 5.60; N, 2.39.
The data for 6 follow. Yield: 0.89 g (86%). 1H NMR (δ ppm,
in benzene-d6): 6.98 (d, 2H,3JH-H ) 7.4 Hz), 6.86 [t, 1H, 3JH-H
) 7.4 Hz, Ta-N(2,6-Me2C6H3)-], 6.17 (br, 4H, C5H4SiMe3),
3.05-2.59 (m, 4H, Ta-CH2-CH2-), 2.4 [br, 6H, Ta-N(2,6-
Me2C6H3)-], 0.89 (s, 6H, -CH2-CMe2-), 0.26 (s, 9H, C5H4-
SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 155.88 (Ci),
135.0 (Co), 128.84 (Cm), 125.52 [Cp, Ta-N(2,6-Me2C6H3)-],
128.6 (Ci, C5H4SiMe3), 116.15 (C5H4SiMe3), 75.93 (-CH2-
CMe2-), 72.11 (Ta-CH2-), 38.25 (-CH2-CMe2-), 27.47
(-CH2-CMe2-), 22.07 [Ta-N(2,6-Me2C6H3)-], -0.13 (C5H4-
SiMe3). Repeated attempts to obtain a satisfactory microan-
alysis on this material were unsuccessful.
The data for 3 follow. Yield: 0.32 g (59%). IR (Nujol mull,
νj cm-1): 1580(w), 1550(m), 1420(m), 1245(s), 1225(m), 1105-
(m), 1090(m), 1026(m), 975(m), 785(s), 769(s), 574(m), 490(w),
475(w). 1H NMR (δ ppm, in benzene-d6): 7.02 [d, 2H, 3JH-H
)
3
7.6 Hz], 6.93 [t, 1H, JH-H ) 7.6 Hz, Ta-N(2,6-Me2C6H3)-],
2.33 (s, 3H), 2.25 [s, 3H, Ta-N(2,6-Me2C6H3)-], 2.09 (s, 3H),
2.01 (s, 3H, Ta-CMe2-), 1.65(s, 15H, C5Me5), 1.60, 1.31 (AB,
2
2H, JH-H ) 11.3 Hz, Ta-CH2SiMe3), 0.30 (s, 9H, Ta-CH2-
SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 150.3 (Ci), 133.6
(Co), 128.7 (Cm), 124.7 [Cp, Ta-N(2,6-Me2C6H3)-], 118.5
(C5Me5), 91.8 (Ta-CMe2-), 71.7 (Ta-CH2SiMe3), 30, 26.8
(Ta-CMe2-), 20.8, 20.3 [Ta-N(2,6-Me2C6H3)-], 10.7 (C5Me5),
2.8 (Ta-CH2SiMe3). Anal. Calcd for C25H41ClNSiTa: C, 50.04;
H, 6.89; N, 2.33. Found: C, 50.10; H, 6.90; N, 2.30.
Synthesis of [TaCp*Cl{C(Me)dCH2}(NAr)] (Cp* ) η5-
C5Me5: Ar ) 2,6-Me2C6H3, 4). A toluene (10 mL) solution of
Mg(CH2Ph)2(thf)2 (0.32 g, 0.91 mmol or 0.16 g, 0.46 mmol) was
added at -78 °C to a solution of 1 (0.50 g, 0.91 mmol) in
toluene (25 mL), and the mixture was stirred for 30 min. The
color of the mixture changed slowly from reddish to yellow. It
was then warmed to room temperature for 10 h, the solvent
removed in vacuo, and the resulting residue extracted with
Synthesis of [TaCpCl2(CHCHCMe2NAr-K2C,N)] (Ar )
2,6-Me2C6H3; Cp ) η5-C5Me5, 10; η5-C5H4SiMe3, 13). Under
rigorously anhydrous conditions, a toluene (35 mL) solution
of 1 or 2 (1.00 g, 1.81 mmol) was placed into a Schlenk tube
and the argon atmosphere replaced by acetylene (1 atm). The
reaction mixture was stirred at room temperature 4 h. The
resulting solution was filtered, and the filtrate was concen-
trated to a volume of ca. 10 mL. Cooling at -40 °C overnight
led to the deposition of microcrystalline yellow solids identified
as 10 and 13
(29) Schrock, R. R. J. Organomet. Chem. 1976, 122, 209-225.

Dichloro Azatantalacyclopropane Complexes
Organometallics, Vol. 24, No. 5, 2005 855
Table 4. Crystal Data and Structure Refinement
for 11 and 14
.
The data for 10 follow. Yield: 0.75 g (72%). IR (KBr, νj cm-1):
2910(s), 1650(w), 1582(m), 1457(s), 1375(s), 1305(w), 1251-
(w), 1182(vs), 1159(s), 1097(m), 1021(m), 949(m), 901(s),
879(m), 813(m), 760(s), 547(w), 508(m), 426(w). 1H NMR
(δ ppm, in benzene-d6): 8.25 (d, 1H, 2JH-H ) 9.8 Hz, Ta-CHd
11
14
chem formula
C
29H36NCl2Ta‚C6H6 C27H34NCl2SiTa‚
C7H8
fw
T, K
728.55
100(2)
0.71073
744.63
153(2)
0.71073
2
CH-), 7.36 (d, 1H, JH-H ) 9.8 Hz, Ta-CHdCH-), 7.07
(d, 2H, 3JH-H ) 7.5 Hz), 6.92 [t, 1H,3JH-H ) 7.5 Hz, Ta-N(2,6-
Me2C6H3)-], 2.98 (s, 3H), 2.09 [s, 3H, Ta-N(2,6-Me2C6H3)-
],1.96 (s, 15H, C5Me5), 0.98 (s, 6H, -CHdCH-CMe2-).
13C{1H} NMR (δ ppm, in benzene-d6): 205 (Ta-CHdCH-),
147.3 (Ta-CHdCH-), 138.3 (Ci), 131.0 (Co), 128.7 (Cm), 126.5
[Cp, Ta-N(2,6-Me2C6H3)-], 124.7 (C5Me5), 85.0 (-CHdCH-
CMe2-), 32, 26.6 (-CHdCH-CMe2-), 22.9, 21.1 [Ta-N(2,6-
Me2C6H3)-], 12.5 (C5Me5). Anal. Calcd for C23H32Cl2NTa: C,
48.09; H, 5.62; N, 2.44. Found: C, 48.03; H, 5.90; N, 2.61.
The data for 13 follow. Yield: 0.30 g (30%). IR (KBr, νj cm-1):
2977(m), 1585(m), 1458(s), 1380(m), 1250(s), 1177(s), 1100-
(m), 1046(m), 905(s), 842(vs), 766(s), 631(w), 510(w), 418(w).
1H NMR (δ ppm, in benzene-d6): 8.37 (d, 1H, 2JH-H ) 9.5 Hz,
λ (Mo, KR), Å
cryst syst, space
group
orthorhombic, Pbca monoclinic, P21/n
a, Å
15.544(2)
19.634(3)
20.140(7)
6147(2)
17.621(1)
8.3557(7); 102.76(1)
22.317(3)
3204.7(6)
4
1.545
3.658
b, Å; â, deg
c, Å
V, Å3
Z
8
F
calcd, g cm-3
1.575
µ, mm-1
3.775
cryst size, mm
θ range, deg
index ranges
0.58 × 0.35 × 0.24
3.18 to 27.5
-19 e h e 19,
-25 e k e 24,
-25 e l e 25
37934
6304 [R(int) )
0.159]
4287
0.4 × 0.3 × 0.3
5.01 to 27.51
-22 e h e 22,
-10 e k e 10,
-28 e l e 25
19331
7257 [R(int) )
0.108]
5685
2
Ta-CHdCH-), 7.35 (d, 1H, JH-H ) 9.5 Hz, Ta-CHdCH-),
no. of data collected
no. of unique data
7.05 (d, 2H, 3JH-H ) 7.3 Hz), 6.88 [t, 1H,3JH-H ) 7.3 Hz, Ta-
N(2,6-Me2C6H3)-], 6.33 (m, 2H), 6.30 (m, 2H, C5H4SiMe3), 2.47
[s, 6H, Ta-N(2,6-Me2C6H3)-], 0.94 (s, 6H, -CHdCH-CMe2-
), 0.24 (s, 9H, C5H4SiMe3). 13C{1H} NMR (δ ppm, in benzene-
d6): 198.75 (Ta-CHdCH-), 159.47 [Ci, Ta-N(2,6-Me2C6H3)-
], 147.09 (Ta-CHdCH-), 134.27 (Ci, C5H4SiMe3), 132.06 (Co),
128.44 (Cm), 125.16 [Cp, Ta-N(2,6-Me2C6H3)-], 124.36 (C2,5),
117.63 (C3,4, C5H4SiMe3), 85.8 (-CHdCH-CMe2-), 25.45
(-CHdCH-CMe2-), 21.69 [Ta-N(2,6-Me2C6H3)-], -0.41
(C5H4SiMe3). Anal. Calcd for C21H30Cl2NSiTa: C, 43.75; H,
5.24; N, 2.43. Found: C, 43.85; H, 5.14; N, 2.60.
no. of obsd reflns
[I >2σ(I)]
absorp corr
Gaussian
semiempirical
from equivalents
1.644 and 0.580
max. and min.
transmn
0.293 and 0.172
no. of params refined 323
352
1.009
R1 ) 0.040,
wR2 ) 0.093
R1 ) 0.061,
wR2 ) 0.101
2.444 and -1.921
goodness-of-fit on F2 1.060
final R indicesa
R1 ) 0.073,
wR2 ) 0.170
R1 ) 0.118,
wR2 ) 0.199
Synthesis of [TaCpCl2{C(Ph)CHCMe2NAr-K2C,N}] (Ar
) 2,6-Me2C6H3; Cp ) η5-C5Me5, 11; η5-C5H4SiMe3, 14). A
solution of 1 or 2 (0.50 g, 0.91 mmol) in toluene (30 mL) was
treated with excess PhCtCH (0.15 mL, 1.36 mmol) under
rigorously anhydrous conditions. The mixture was stirred for
15 h and then filtered. The filtrate was concentrated to ca.
5 mL, and cooling overnight at -40 °C produced 11 or 14,
deposited as a red microcrystalline solids.
R indices (all data)
largest diff peak and 1.979 and -1.796
hole, e Å-3
2 2
a R1 ) ∑||Fo| - |Fc||/[∑|Fo|]; wR2 ) {[∑w(Fo2 - Fc)2]/[∑w(Fo ) ]}1/2
.
Me2C6H3)-], -0.70 (C5H4SiMe3). Anal. Calcd for C27H34Cl2-
NSiTa: C, 49.69; H, 5.25; N, 2.15. Found: C, 49.73; H, 5.10;
N, 2.23.
The data for 11 follow. Yield: 0.42 g (71%). IR (KBr, νj cm-1):
2914(s), 1631(w), 1590(w), 1570(w), 1456(vs), 1377(s), 1298-
(w), 1253(w), 1176(vs), 1137(s), 1098(m), 1026(m), 963(m),
876(s), 806(m), 766(vs), 705(m), 599(w), 545(w), 476(w). 1H
NMR (δ ppm, in benzene-d6): 7.65 [m, 2H, Ta-C(C6H5)dCH-
Synthesis of [TaCp*Cl2{C(SiMe3)CHCMe2NAr-K2C,N }-
] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 12). A 100 mL ampule
(Teflon stopcock) was charged with 1 (0.40 g, 0.73 mmol), an
excess of trimethylsilylacetylene (0.15 mL, 1.06 mmol), and
toluene (20 mL). After the reaction mixture had been stirred
at room temperature for 6 days the volatile components were
removed under reduced pressure. The resultant oily reddish
solid was washed with hexane (2 × 5 mL) and identified by
1H NMR spectroscopy as a mixture of 12, the starting material
1, and the dichloro(imido) complex 7. By successive recrystal-
lization in toluene complex 12 can be isolated as a red solid
but always impurified with 1 and the dichloro(imido) complex
7 as minority components.
], 7.31 [s, 1H, Ta-C(Ph)dCH-], 7.27 [t, 2H, Ta-C(C6H5)d
CH], 7.14 [m, 1H, Ta-C(C6H5)dCH-], 7.10 (d, 1H, JH-H
3
)
3
7.2 Hz), 6.91 [t, 1H, JH-H ) 7.2 Hz, Ta-N(2,6-Me2C6H3)-],
3.01 (s, 3H), 2.18 [s, 3H, Ta-N(2,6-Me2C6H3)-], 1.94 (s, 15H,
C5Me5), 1.13 (s, 3H), 0.81 (s, 3H, dCH-CMe2-). 13C{1H} NMR
(δ ppm, in benzene-d6): 213.6 [Ta-C(Ph)dCH-], 155-126
[several phenyl, Ta-C(C6H5)dCH-], 155-126 [several phenyl,
Ta-N(2,6-Me2C6H3)-], 146.53 [Ta-C(Ph)dCH-], 124.8 (C5-
Me5), 77.9 (dCH-CMe2-), 32.9, 27.9 (dCH-CMe2-), 22.9,
21.0 [Ta-N(2,6-Me2C6H3)-], 12.95 (C5Me5). Anal. Calcd for
C29H36Cl2NTa: C, 53.55; H, 5.58; N, 2.15. Found: C, 53.47;
H, 5.49; N, 2.21.
The data for 12 follow. 1H NMR (δ ppm, in benzene-d6): 8.32
[s, 1H, Ta-C(SiMe3)dCH-], 7.11 (d, 2H, 3JH-H ) 7.5 Hz), 6.88
3
The data for 14 follow. Yield: 0.35 g (62%). IR (KBr, νj cm-1):
2966(s), 1829(w), 1768(w), 1590(s), 1460(s), 1323(w), 1289-
(w), 1247(s), 1172(s), 1137(s), 1098(m), 1075(m), 1053(m),
962(m), 905(s), 840(vs), 760(vs), 702(s), 629(m), 543(w), 482-
(w), 414(m). 1H NMR (δ ppm, in benzene-d6): 7.47-6.64
[several phenyl, Ta-C(C6H5)dCH-, Ta-N(2,6-Me2C6H3)-],
7.02 [s, 1H, Ta-C(Ph)dCH-], 6.40 (m, 1H), 6.32 (m, 1H), 6.19
(m, 1H), 5.72 (m, 1H, C5H4SiMe3), 2.94 (br, 3H), 2.16 [br, 3H,
Ta-N(2,6-Me2C6H3)-], 0.92 (br, 6H, dCH-CMe2-), 0.14 (s,
9H, C5H4SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 210
[Ta-C(Ph)dCH-], 160.33 [Ta-C(Ph)dCH-], 151.9-129.2
[several phenyl, Ta-C(C6H5)dCH-, Ta-N(2,6-Me2C6H3)-],
126.1 (Ci), 125.5, 125.2, 123.3, 118.5 (C5H4SiMe3), 82.1 (dCH-
CMe2-), 31.78 (br, dCH-CMe2-), 26.54, 21.75 [br, Ta-N(2,6-
[t, 1H, JH-H ) 7.5 Hz, Ta-N(2,6-Me2C6H3)-], 2.92 (s, 3H),
2.20 [s, 3H, Ta-N(2,6-Me2C6H3)-], 2.04 (s, 15H, C5Me5), 1.02
(s, 3H), 0.86 (s, 3H, dCH-CMe2-), 0.37 [s, 9H, Ta-C(SiMe3)d
CH-]. 13C{1H} NMR (δ ppm, in benzene-d6): 222.6 [Ta-
C(SiMe3)dCH-], 159.1 [Ta-C(SiMe3)dCH-], 160-126 [sev-
eral phenyl, Ta-N(2,6-Me2C6H3)-], 124.7 (C5Me5), 84.5
(dCH-CMe2-), 29.2, 27.8(dCH-CMe2-), 22.9, 20.8 [Ta-
N(2,6-Me2C6H3)-], 12.97 (C5Me5), 2.92 [Ta-C(SiMe3)
dCH-].
Synthesis of [TaCp′Cl2{C(SiMe3)CHCMe2NAr-K2C,N}]
(Cp′ ) η5-C5H4SiMe3; Ar ) 2,6-Me2C6H3, 15). A 100 mL
Schlenk flask was charged with 2 (0.40 g, 0.73 mmol), excess
Me3SiCtCH (0.15 mL, 1.06 mmol), and toluene (25 mL). After
the mixture had been stirred at room temperature for 10 h,

856 Organometallics, Vol. 24, No. 5, 2005
Galakhov et al.
the volume of the solution was concentrated to ca. 10 mL under
reduced pressure. The resulting solution was cooled to
-40 °C overnight to afford orange crystals of 15.
of 7 s per frame (4 sets; 316 frames). Raw data were corrected
for Lorentz and polarization effects.
Both structures were solved by direct methods, completed
by the subsequent difference Fourier techniques, and refined
by full-matrix least squares on F2 (SHELXL-97).30 Anisotropic
thermal parameters were used in the last cycles of refinement
for the non hydrogen atoms expect for seven atoms in
compound 11, which have some of the thermal parameters
fixed in the last cycle of refinement. The hydrogen atoms were
included from geometrical calculations and refined using a
riding model. All the calculations were made using the WINGX
system.31
The data for 15 follow. Yield: 0.32 g (68%). IR (KBr, νj cm-1):
2949(s), 1585(w), 1553(m), 1461(m), 1410(m), 1371(m), 1287-
(w), 1245(s), 1179(s), 1138(m), 1096(m), 1049(m), 957(w),
878(s), 836(vs), 756(s), 648(m), 628(m), 589(w), 468(w), 442-
(w), 416(w). 1H NMR (δ ppm, in benzene-d6): 8.25 [s, 1H, Ta-
3
C(SiMe3)dCH-], 7.03 (d, 2H, JH-H ) 7.4 Hz), 6.85 [t, 1H,
3JH-H ) 7.4 Hz, Ta-N(2,6-Me2C6H3)-], 6.5 (br, 4H, C5H4-
SiMe3), 2.50 [br, 6H, Ta-N(2,6-Me2C6H3)-], 0.91 (br, 6H, d
CH-CMe2-), 0.36 [s, 9H, Ta-C(SiMe3)dCH-], 0.26 (s, 9H,
C5H4SiMe3). 13C{1H} NMR (δ ppm, in benzene-d6): 216.32
[Ta-C(SiMe3)dCH-], 157.93 [Ta-C(SiMe3)dCH-], 161.17-
(Ci), 132.94 (Co), 128.16 (Cp), 125.16 [Cm, Ta-N(2,6-Me2C6H3)-
], 124.9(Ci), 122.8 (C5H4SiMe3), 86.79 (dCH-CMe2-), 28.9
(dCH-CMe2-), 21.57 [Ta-N(2,6-Me2C6H3)-], 1.66 [Ta-
C(SiMe3)dCH-], 0.1 (C5H4SiMe3). Anal. Calcd for C24H38Cl2-
NSi2Ta: C, 44.40; H, 5.90; N, 2.16. Found: C, 43.85; H, 5.99;
N, 2.16.
Acknowledgment. We thank the MCYT (Project
BQU 2002-03754) for its financial support of this
research.
Supporting Information Available: Tables of experi-
mental details of the X-ray studies, atomic coordinates and
equivalent isotropic thermal parameters, bond distances and
angles, anisotropic displacement parameters, and hydrogen
atom coordinates for 11 and 14 and in CIF format. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Crystal Structure Determination of Compounds 11
and 14. Crystals suitable for the X-ray analyses were obtained
by recrystallization from benzene (11) and toluene (14) solu-
tions. The crystallographic and experimental details of the
crystal structure determinations are given in Table 4. Suitable
crystals of complexes 11 and 14 were covered with mineral
oil and mounted in the N2 stream of a Bruker-Nonius Kappa
CCD diffractometer, and data were collected using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). Data
collection was performed at low temperature (see Table 4), in
the case of compound 11 with an exposure time of 8 s per frame
(3 sets; 286 frames) and compound 14 with an exposure time
OM049110V
(30) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Analysis (Release 97-2); University of Go¨ttingen: Go¨ttingen, Germany,
1998.
(31) WINGX: Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837-
838.