Alkylation, insertion of isocyanides, and intramolecular rearrangement processes in azatantalacyclopentene complexes. X-ray crystal Structure of [TaCp*Me2(CHCHCMe2NAr-K2C,N)] (Cp* - η5-C5Me5</sub

Article abstract of DOI:10.1021/om050289z

Chloro methyl and dimethyl azatantalacyclopentene complexes were prepared. Reaction of 1a with dibenzylmagnesium leads to the monoalkylated complex. Anisotropic thermal parameters were used in the last cycles of refinement for the nonhydrogen atoms. All c

Full text of DOI:10.1021/om050289z

3552
Organometallics 2005, 24, 3552-3560
Alkylation, Insertion of Isocyanides, and Intramolecular
Rearrangement Processes in Azatantalacyclopentene
Complexes. X-ray Crystal Structure of
[TaCp*Me2(CHCHCMe2NAr-K2C,N)] (Cp* ) η5-C5Me5;
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 April 15, 2005
Chloro methyl and dimethyl azatantalacyclopentene complexes [TaCp*Cl2-xMex(CHCHCMe2-
NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3; x ) 1, 2; 2, 3) can be prepared by reaction
of [TaCp*Cl2(CHCHCMe2NAr-κ2C,N)] (1a) with dimethylzinc and chloromethylmagnesium,
respectively. Reaction of 1a with dibenzylmagnesium leads to the monoalkylated complex
[TaCp*Cl(CH2Ph)(CHCHCMe2NAr-κ2C,N)] (4). The alkylation of [TaCp*Cl2{C(Ph)CHCMe2-
NAr-κ2C,N}] (1b) with 2 equiv of chloromethylmagnesium at low temperature gave the
dimethyl azatantalacyclopentene complex [TaCp*Me2{C(Ph)CHCMe2NAr-κ2C,N}] (5), which
at room temperature decomposes, giving the dimethyl(imido) complex [TaCp*Me2(NAr)] (7),
identified by NMR spectroscopy. Alkylation of 1b with 0.5 equiv of dibenzylmagnesium leads
to the monobenzyl complex [TaCp*Cl(CH2Ph){C(Ph)CHCMe2NAr-κ2C,N}] (6); however
treatment with 1 equiv of the alkylating reagent gave the dibenzyl(imido) [TaCp*(CH2Ph)2-
(NAr)] (8) in a mixture with 6 as minor component. Moreover, 1a reacts with 1 equiv of
isocyanides RNC (R ) 2,6-Me2C6H3; tBu) to give the dichloro(imido) complex [TaCp*Cl2-
(NAr)] (9), while the treatment of the chloro methyl azatantalacyclopentene 2 with 2 equiv
of isocyanides RNC (R ) 2,6-Me2C6H3; tBu) at different conditions affords the imido η2-
iminoacyl derivatives [TaCp*Cl(NAr){η2-C(Me)dNR}] (R ) 2,6-Me2C6H3, 12; tBu, 13) in good
yields with simultaneous elimination of s-trans-vinylazacumulenes R-NdCdCH-CHdCMe2
(R ) 2,6-Me2C6H3, 10; tBu, 11). Similarly, the reaction of the dimethyl azatantalacyclopentene
3 with 1 equiv of 2,6-Me2C6H3NC produces the alkenylamido imido methyl derivative
[TaCp*Me(NAr){η1-N(Ar)-C(Me)dCH-CHdCMe2}] (14), which with one additional equiva-
lent of isocyanide gives the imido η2-iminoacyl methyl compound [TaCp*Me(NAr)(η2-C{CH-
(CMedNAr)(CHdCMe2)}dNAr)] (15). All compounds were studied by IR and NMR
spectroscopy, and the molecular structure of complex 3 was determined by X-ray diffraction
methods.
Introduction
monomers,2 and several organometallic systems capable
of catalyzing the living polymerization of olefins have
been designed.3 Alternatively, also provided were con-
venient routes to synthetic applications4 by unsaturated
organic derivatives coupling reactions, via metallacyclic
intermediates.5 Several studies related with titanium
and zirconium η2-imine complexes4a,6 have been re-
Mono- and bis(cyclopentadienyl) complexes of early
transition metals are well established as important
types of olefin polymerization catalysts.1 The 1990s have
witnessed a spectacular development of a new genera-
tion of “nonmetallocene” catalysts potentially useful to
polymerize ethylene on its own and with other olefinic
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Soc. 1995, 117, 6414-6415. (c) Britovsek, G. J. P.; Gibson, V. C.;
Kimberley, B. S.; Maddox, P. J.; McTavish, S. J.; Solan, G. A.; White,
A. J. P.; Williams, D. J. Chem. Commun. 1998, 849-850. (d) Small, B.
L.; Brookhart, M.; Bennett, A. M. A. J. Am. Chem. Soc. 1998, 120,
4049-4050.
§ This paper is dedicated to the memory of Dr. Juan Carlos del Amo,
who was a victim of the March 11, 2004, tragedy in Madrid.
* Corresponding
author.
Fax:
34-91-885.46.83.
E-mail:
manuel.gomez@uah.es.
† Departamento de Qu´ımica Inorga´nica.
‡ Centro de Espectroscopia de RMN.
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Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143-1170.
(b) Mashima, K.; Nakayama, Y.; Nakamura, A. Adv. Polym. Sci. 1997,
133, 1-51. (c) McKnight, A. L.; Waymouth, R. M. Chem. Rev. 1998,
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10.1021/om050289z CCC: $30.25 © 2005 American Chemical Society
Publication on Web 06/09/2005

Azatantalacyclopentene Complexes
Organometallics, Vol. 24, No. 14, 2005 3553
ported but few with monocyclopentadienyl derivatives
of group 5 metals.5f,g These derivatives may participate
in the development of simple and general methods for
the synthesis of enantiomerically pure organic com-
pounds such as the following: (i) substituted pyrroles
by reaction with CO,7 (ii) racemic allylic amines from
simple amines and unfunctionalized alkynes,8 (iii) car-
bocyclic and heterocyclic rings,9 and (iv) cyclopentyl-
amines and unusual R-amino acids.10
Further, the broad success of early transition metal
based organic synthesis is due in part to the unique
ability of the metal to activate ligands to which it is
directly bound through organometallic transformations
that are often highly chemo-, regio-, and stereoselective
processes. In this context, zirconacycles9a,b,11 are avail-
able from simple organic precursors either by cocycliza-
tion of 1,n-dienes, enynes, and diynes using a zir-
conocene fragment or by trapping of metallocene η2-
alkene, -alkyne, and -benzyne complexes with alkenes
or alkynes. Methods for further elaboration of these
zirconacycles forming carbon-heteroatom bonds include
oxygenation, halogenation,12 and metathesis with a
variety of element-dihalides.13 Carbon-carbon bond
forming methods include carbonylation14 or, more re-
cently, tandem processes involving the insertion of
isocyanides and trapping of the resulting zirconocene
η2-imine complexes with unsaturated species.6p,r,10,15,16a
Further, the intermolecular addition of titanocene vi-
nylidene complexes to alkynes gives titanacyclobutenes,
which undergo an insertion-rearrangement with tert-
butyl isocyanide to afford allenylketenimines.16b
In group 5, niobium and tantalum alkyne com-
plexes17-20 have provided convenient routes to organic
products4b,c,6i,21 via metallacyclic intermediates.4a,22 Fur-
thermore, alkyne tantalum(III) derivatives react with
nitriles, leading to azatantalacyclopentene complexes
that may participate in an intermolecular isomerization
process to enamines.4c
We report herein the synthesis of alkyl azatantala-
cyclopentene derivatives, their reactivity with isocya-
nides, and the intramolecular rearrangement processes
observed in the resulting complexes. The X-ray molec-
ular structure of the complex [TaCp*Me2(CHCHCMe2-
NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 3) is
also described.
Results and Discussion
Synthesis of Alkyl Azatantalacyclopentene Com-
plexes. [TaCp*Cl2-xMex(CHCHCMe2NAr-κ2C,N)] (Cp*
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3554 Organometallics, Vol. 24, No. 14, 2005
Galakhov et al.
lacyclopentene moiety23 and leads to a mixture of
compounds in which 6 as minor component and the
dibenzyl(imido) tantalum complex [TaCp*(CH2Ph)2-
(NAr)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 8)25 were
identified by NMR spectroscopy. The presence of the
dibenzyl imido complex 8 among the reaction products
can be explained assuming that the decomposition of
the dibenzyl azatantalacyclopentene derivative is faster
that its formation rate.
Scheme 1
All of the complexes 2-6 are soluble in aromatic
hydrocarbons and chlorinated solvents and only slightly
soluble in saturated hydrocarbons. The IR spectra show
the characteristic absorptions due to the ν(CdC),5c,d,24,26
ν(C-N),27 ν(C-C)(Cp* ring),5g,28,29 ν(Ta-N),27 and ν(Ta-
C)5g,29-31 stretching vibrations at νj 1585, 1175, 1025,
580, and 505 cm-1, respectively. The NMR data of the
alkyl azatantalacyclopentene derivatives are in agree-
ment with the expected pseudo-square-pyramidal ge-
ometry for 3 and 5 and also with the asymmetrical
structure for 2, 4, and 6.
Scheme 2
1
Moreover, at room temperature the H NMR spec-
trum of complex 3 shows some broad signals. When a
CD2Cl2 solution of 3 was studied by 1H variable-
temperature NMR between 203 and 313 K, the mutual
exchange of the Ta-Me2, CMe2, and 2,6-Me2C6H3 reso-
nances, respectively, was observed. Kinetics param-
eters32 calculated on the basis of line shape analysis
data show that this transformation is an intramolecular
process (log A ) 12) which consists of the interconver-
sion between two four-legged piano-stool enantiomeric
ground states through a trigonal bipyramidal transition
state, well-known as Berry pseudorotation and similar
to other previously described transformations.5g,6a,33
A view of the molecular structure of the dimethyl
azatantalacyclopentene complex 3 is shown in the
Figure 1. Selected bond distances and angles are
presented in Table 1.
) η5-C5Me5; Ar ) 2,6-Me2C6H3; x ) 1, 2; 2, 3) were
obtained in good yields by treatment of the dichloro
azatantalacyclopentene complex [TaCp*Cl2(CHCHCMe2-
NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 1a)23
with 1 equiv of ZnMe2 or 2 equiv of MgClMe in toluene
at room temperature (see Scheme 1). Alkylation of 1a
with Mg(CH2Ph)2(thf)2, in a 1:1 molar ratio or in excess,
gave the monoalkylated derivative [TaCp*Cl(CH2Ph)-
(CHCHCMe2NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-
Me2C6H3, 4) as a red microcrystalline solid.
Compound 3 can be described as a monomer with a
typical four-legged piano-stool environment for the
tantalum atom, with the pentamethylcyclopentadienyl
ring in the cap position, the legs defined by two methyl
groups, and the nitrogen and a carbon atom included
The addition of 2 equiv of MgClMe to toluene solu-
tions of [TaCp*Cl2{C(Ph)CHCMe2NAr-κ2C,N}] (Cp* )
η5-C5Me5; Ar ) 2,6-Me2C6H3, 1b)23 under rigorously
anhydrous conditions at -78 °C yields the dimethyl
azatantalacyclopentene complex [TaCp*Me2{C(Ph)-
CHCMe2NAr-κ2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-
Me2C6H3, 5) (Scheme 2). When the alkylation was
carried out at room temperature, complex 5 decomposed,
giving a mixture in which the dimethyl(imido) tantalum
complex [TaCp*Me2(NAr)] (Cp* ) η5-C5Me5; Ar ) 2,6-
Me2C6H3, 7)24 was identified by NMR spectroscopy.
On the other hand, 1b also reacts with 0.5 equiv of
Mg(CH2Ph)2(thf)2 at room temperature in toluene to
give the expected benzyl chloro derivative [TaCp*Cl-
(CH2Ph){C(Ph)CHCMe2NAr-κ2C,N}] (Cp* ) η5-C5Me5;
Ar ) 2,6-Me2C6H3, 6). However, when 1 equiv of Mg-
(CH2Ph)2(thf)2 is used, the reaction takes place with the
rupture of the Ta-C and C-N bonds in the azatanta-
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Castro, A.; Galakhov, M. V.; Go´mez, M.; Go´mez-Sal, P.; Mart´ın, A. Eur.
J. Inorg. Chem. 2002, 1336-1342.
(32) log A ) 11.3 ( 0.25; Eact. ) 12.00 ( 0.30 kcal/mol (r ) 0.998,
F6.2 ) 1645.4); ∆H# ) 11.80 ( 0.31 kcal/mol, ∆S# ) -8.23 ( 1.20 eu (r
) 0.998, F6.2 ) 1466.67); ∆G#298K ) 14.2 kcal/mol.
(33) (a) Galakhov, M. V.; Go´mez, M.; Jime´nez, G.; Royo, P.; Pelling-
helli, M. A.; Tiripicchio, A. Organometallics 1995, 14, 2843-2854. (b)
de Castro, I.; Galakhov, M. V.; Go´mez, M.; Go´mez-Sal, P.; Mart´ın, A.;
Royo, P. J. Organomet. Chem. 1996, 514, 51-58.
(23) Galakhov, M. V.; Go´mez, M.; Go´mez-Sal, P.; Velasco, P. Orga-
nometallics 2005, 24, 848-856.
(24) Go´mez, M.; Go´mez-Sal, P.; Jime´nez, G.; Mart´ın, A.; Royo, P.;
Sa´nchez-Nieves, J. Organometallics 1996, 15, 3579-3587.

Azatantalacyclopentene Complexes
Organometallics, Vol. 24, No. 14, 2005 3555
Scheme 3
Scheme 4
Reactions with Isocyanides. [TaCp*Cl2(CHCH-
CMe2NAr-κ2C,N)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3,
1a) reacts with 1 equiv of isocyanides RNC (R ) 2,6-
Me2C6H3; tBu) in toluene, giving a reddish solution,
which after manipulations affords a mixture of the
dichloro(imido) tantalum complex [TaCp*Cl2{N(2,6-
Me2C6H3)}] (Cp* ) η5-C5Me5, 9)5f and the s-trans-
vinylazacumulenes R-NdCdCH-CHdCMe2 (R ) 2,6-
Me2C6H3, 10; tBu, 11) in a 1:1 ratio (Scheme 3).
The formation of compounds 9-11 probably takes
place assuming the coordination34 of the isocyanide to
the metal center of complex 1a in the first reaction step
to give an intermediate adduct A (see Scheme 4). The
subsequent Ta-C(sp2) bond rupture and the coupling
between two carbon atoms leads to a metallacyclic
species B, which by an intramolecular rearrangement
gives a dichloro(imido) complex 9 and the vinylazacu-
mulenes 10 and 11.
Figure 1. ORTEP drawing of compound 3.
Table 1. Selected Bond Lengths [Å] and Angles
[deg] for Compound 3a
Ta(1)-N(1)
Ta(1)-C(2)
Ta(1)-C(3)
Ta(1)-C(5)
Ta(1)-C(7)
N(1)-C(10)
C(9)-C(10)
2.028(4)
2.209(6)
2.455(5)
2.453(6)
2.519(6)
1.533(7)
1.499(9)
Ta(1)-C(8)
Ta(1)-C(1)
Ta(1)-C(4)
Ta(1)-C(6)
N(1)-C(11)
C(8)-C(9)
Cp-Ta(1)
2.181(6)
2.213(6)
2.402(6)
2.534(5)
1.436(7)
1.314(9)
2.158
N(1)-Ta(1)-C(8)
C(8)-Ta(1)-C(2)
C(8)-Ta(1)-C(1)
C(8)-C(9)-C(10)
Cp-Ta(1)-C(8)
Cp-Ta(1)-C(1)
76.0(2)
79.2(3)
143.9(3)
119.5(6)
106.16
107.6
N(1)-Ta(1)-C(2)
N(1)-Ta(1)-C(1)
C(2)-Ta(1)-C(1)
C(9)-C(8)-Ta(1)
Cp-Ta(1)-N(1)
Cp-Ta(1)-C(2)
112.1(2)
85.1(2)
79.8(3)
115.9(5)
142.2
105.33
a Cp is the centroid of the C3-C4-C5-C6-C7 ring.
On the other hand, when a benzene-d6 solution of the
chloro methyl complex 2 is treated with the same
isocyanides in a 1:2 ratio (see Scheme 3), in a sealed
NMR tube, the formation of the η2-iminoacyl derivatives
[TaCp*Cl(NAr){η2-C(Me)dNR}] (Cp* ) η5-C5Me5; Ar )
2,6-Me2C6H3; R ) 2,6-Me2C6H3, 12;24 tBu, 13) and the
s-trans-vinylazacumulenes 10 and 11 was observed by
1H NMR spectroscopy. Under these conditions, a chloro
imido methyl complex, similar to 9, was not detected,
but we suggest (see Scheme 5) that the chloro imido η2-
iminoacyl derivatives 12 (R ) 2,6-Me2C6H3) and 13 (R
) tBu) form from such intermediate species C by fast
insertion of isocyanide into the Ta-CH3 bond.
The complexes 12 and 13 are soluble in aromatic,
chlorinated, and ethereal solvents but only slightly
soluble in saturated hydrocarbons, and their spectro-
scopic data are consistent with their formulation. Both
complexes show the characteristic absorption for
the pentamethylcyclopentadienyl ring (νjC-C ) 1027
cm-1),5g,28,29 and the imido η2-iminoacyl complex 13
in the azatantalacyclopentene moiety TaC3N. This
structure is very similar to that described by us for the
dichloro azatantalacyclopentene derivative [TaCp*Cl2-
{C(Ph)CHCMe2NAr-κ2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-
Me2C6H3, 1b).23 The bonding in the TaC3N unity cor-
responds to a diene with a double bond Ta-N (2.028(4)
Å), and between the carbon atoms R and â with respect
to the tantalum atom the C8-C9 bond distance is 1.314-
(9) Å. The distance Ta-C8 (2.181(6) Å) is typical of a
single bond. The azatantalacyclopentene moiety is fairly
planar, with a fold angle defined between the planes
N1, Ta1, C8 and N1, C8, C9, C10 of 15.6(2)°. The Ta-
C(methyl) distances (Ta-C1 2.213(6) Å, Ta-C2 2.209-
(6) Å) are in the range corresponding to normal values
of a Ta-C5f,24,29,33a single bond and are both almost
identical, in contrast with the situation in the afore-
mentioned complex 1b,23 where clearly different values
for the Ta-Cl distances were found. The 2,6-Me2C6H3
ring bonded to the nitrogen atom is located quasi
perpendicular to the azatantalacyclopentene moiety
(80.9(1)°) and to the pentamethylcyclopentadienyl ring
planes (61.45(2)°).
(34) Go´mez, M.; Go´mez-Sal, P.; Nicola´s, M. P.; Royo, P. J. Orga-
nomet. Chem. 1995, 491, 121-125.

3556 Organometallics, Vol. 24, No. 14, 2005
Galakhov et al.
Scheme 5
Scheme 6
shows the νTadN24,25,29,31a,36 and νC(Me)dN5g,29,37 IR absorp-
tions at 1330 and 1646 cm-1, respectively.
In the IR spectra of R-NdCdCH-CHdCMe2 (R )
2,6-Me2C6H3, 10; tBu, 11) were observed absorption
bands at 2023 (10) and 2015 (11) cm-1, which can be
assigned to the νCN stretching vibration.33a,38 The 13C-
{1H} NMR spectra of both vinylazacumulenes show the
typical resonances at δ 190.8, 186.7 (-NdCdCH-) and
52.2, 55.8 (-NdCdCH-) for 10 and 11, respectively.
In solution, they are mainly present as s-trans isomers
in accordance with the observed NOE effects and with
the vicinal (3JH-H) SSCC values found of 10.7 Hz (10)
and 10.8 Hz (11).
(X ) Cl, Me; Ar ) 2,6-Me2C6H3). Moreover, when 3 is
treated with 2 equiv of 2,6-Me2C6H3NC in the same
conditions, an unresolved mixture was obtained.
The presence of the imido ligand in complex 14 was
confirmed by the absorption band located at 1305 cm-1
,
whereas the NMR spectra in C6D6 show the presence
of a pentamethylcyclopentadienyl ring, one methyl
group bonded to the tantalum atom (δ 0.97 (1H); 34.8
(13C)), the expected signals for a N-C(Me)dCH-CHd
CMe2 moiety, and two types of 2,6-Me2C6H3 rings (see
Experimental Section). The 1H NMR spectrum at room
temperature also shows a broad signal at δ 1.67 (6H,
∆ν ) 9.5 Hz) for -CHdCMe2 and another one at δ 2.17
(6H, ∆ν ) 8.3 Hz) for the Ta-N(2,6-Me2C6H3). Its
assignment and the corresponding C6H3 signals at δ
6.89 (2H) and 6.60 (1H)) in the amido moiety were
realized by observation in the gHMBC spectrum of its
coherence cross-peaks, with the broad (∆ν ) 25 Hz)
resonance at δ 151.7 due to C1 of the aryl amido ring,
whereas the more deshielded C1 signal for the imido
group is observed at δ 153.2. Moreover, the carbon
spectrum at 25 °C shows other broad signals at δ 144.0
(∆ν ) 8 Hz) and 134.2 (∆ν ) 15 Hz) corresponding to
the aryl amido and at δ 108.4 (∆ν ) 10 Hz) for -HCd
CMeN- moieties.
The NMR data for the η2-iminoacyl complex 13 (see
Experimental Section) are in agreement with the ex-
pected pseudo-square-pyramidal geometry found for
similar chiral niobium and tantalum derivatives24,29 in
which a characteristic η2-iminoacyl carbon resonance
appears at δ 233.
The addition of 1 equiv of 2,6-Me2C6H3NC to a toluene
solution of the dimethyl azatantalacyclopentene
[TaCp*Me2(CHCHCMe2NAr-κ2C,N)] (Cp* ) η5-C5Me5;
Ar ) 2,6-Me2C6H3, 3) leads to the formation of the
alkenyl-enamido imido methyl derivative [TaCp*Me-
(NAr){η1-N(Ar)-C(Me)dCH-CHdCMe2}] (Cp* ) η5-C5-
Me5; Ar ) 2,6-Me2C6H3, 14) (Scheme 6).
A similar reaction pathway to that shown in Scheme
4 could explain the formation of 14 from a transition
state I (Scheme 6). The coordination of the free nitrogen
electron pair to the tantalum atom, the migration of the
methyl group to the carbon atom of the inserted isocya-
nide with the concertated rupture of the Ta-C and
N-C, and R-migration of the π CdC bonds lead to the
resultant product 14. This behavior is similar to that
reported33a for the [TaCp*ClxMe4-x] (Cp* ) η5-C5Me5; x
) 1, 0) complexes, which in the presence of 2 equiv of
isocyanides afford the chloro and methyl alkenylamido
imido compounds [TaCp*X(NAr){η1-N(Ar)-C(Me)dCMe2}]
The 1H (500 MHz) NMR spectra of 14 in CD2Cl2
solution obtained between 178 and 298 K (see Figure
2) show the significant line width variations that are
in accordance with typical spin exchange processes of
more than two very different populated positions39 and
could be explained by the well-known restricted rotation
about C-N and CdC bonds (see Scheme 7) in organic
enamines40 and organometallic enamides.33a
We suggest that this behavior, coincidental to that
previously observed by us for similar tantalum deriva-
tives,33a determines the reactivity of complex 14. So,
when 1 equiv of 2,6-Me2C6H3NC is added to a benzene-
d6 solution of pure 14, under rigorously anhydrous
conditions, a new reaction takes place to give an imido
η2-iminoacyl methyl derivative [TaCp*Me(NAr)(η2-C{CH-
(CMedNAr)(CHdCMe2)}dNAr)] (Cp* ) η5-C5Me5; Ar
) 2,6-Me2C6H3, 15) in quantitative yield (Scheme 7).
After coordination of the isocyanide to the tantalum
atom, it forms a transition state I, in which a concer-
(35) Curtis, M. D.; Real, J. J. Am. Chem. Soc. 1986, 108, 4668-
4669.
(36) (a) Bradley, D. C.; Hursthouse, M. B.; Howes, A. J.; Jelfs, A. N.
de M.; Runnacles, J. D.; Thornton-Pett, M. 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.
(37) (a) Klei, E.; Telgen, J. H.; Teuben, J. H. J. Organomet. Chem.
1981, 209, 297-307. (b) Chamberlain, L. R.; Durfee, L. D.; Fanwick,
P. E.; Kobriger, L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.;
Folting, K.; Huffman, J. C.; Streib, W. E.; Wang, R. J. Am. Chem. Soc.
1987, 109, 390-402.
(38) (a) Bestmann, H. J.; Lienert, J.; Mott, L. Liebigs Ann. Chem.
1968, 718, 24. (b) Collier, C.; Webb, G. A. Org. Magn. Reson. 1979, 12,
659.
(39) Jackman, K. M.; Cotton, F. A. DNMR Spectroscopy; Academic
Press: New York, 1975.
(40) Bakmutov, V. I.; Fedin, E. I. Bull. Magn. Reson. 1984, 6, 142.

Azatantalacyclopentene Complexes
Organometallics, Vol. 24, No. 14, 2005 3557
1
Figure 2. VT H NMR spectra of complex 14 in CD2Cl2.
Scheme 7
tated carbon-carbon coupling, a tantalum-nitrogen
bond rupture, and the nitrogen free electron pair
coordination to the metal to give the final product 15
take place.
The NMR spectra of 15 show all the expected reso-
nances (see Experimental Section) due to the η2-imi-
noacyl (δ13C 239.5) and the vinylimine moieties, three
sets for the 2,6-Me2C6H3 rings and one for the penta-

3558 Organometallics, Vol. 24, No. 14, 2005
Galakhov et al.
signals. Microanalyses (C, H, N) were performed in a LECO
CHNS 932 microanalyzer.
methylcyclopentadienyl ring and the methyl group
bonded to the tantalum atom (δ1H 0.56; δ13C 21.3).
Moreover, for the dCH-CH- vinylimine moiety, the 1H
NMR spectrum shows an AB system (3JH-H ) 10.7 Hz)
at δ 5.58 and 5.01, in which the first doublet is
desdoubled in septuplet by allylic coupling with both
methyl protons (4JH-H ) 1.2 Hz), whereas its carbon
resonances are observed at δ 121.4 and 60.1, in agree-
ment with the gHMQC data.
Synthesis of [TaCp*ClMe(CHCHCMe2NAr-K2C,N)] (Cp*
) η5-C5Me5; Ar ) 2,6-Me2C6H3, 2). A 2 M toluene solution of
ZnMe2 (0.65 mL, 1.30 mmol) was added at room temperature
to a yellow solution of 1a (0.75 g, 1.30 mmol) in toluene (40
mL), and the mixture was stirred for 12 h. The resulting
suspension was filtered, the solvent reduced to dryness, and
the residue extracted with hexane (3 × 15 mL). Subsequently,
the solution was concentrated to ca. 10 mL and cooled to -40
°C overnight to afford 2 as an extremely air-sensitive micro-
crystalline yellow solid.
Conclusions
The data for 2 follow. Yield: 0.45 g (62%). IR (KBr, νj cm-1):
2913(vs), 1635(w), 1577(m), 1456(vs), 1375(s), 1348(w), 1305-
(m), 1184(vs), 1163(s), 1138(m), 1098(s), 1024(s), 958(m), 907-
(s), 882(m), 814(m), 764(s), 687(w), 599(w), 544(w), 507(m),
482(m), 434(w). 1H NMR (δ ppm, in benzene-d6): 7.68(d, 1H),
7.24(d, 1H, 2JH-H ) 10.6 Hz, Ta-CHdCH-), 7.10(d, 2H), 6.97-
The direct alkylation of [TaCp*Cl2{C(R)CHCMe2NAr-
κ2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3; R ) H,
1a; Ph, 1b) with the appropriate amount of alkylating
reagent and in different conditions leads to the forma-
tion of the alkyl azatantalacyclopentene complexes
[TaCp*Cl2-xR′x{C(R)CHCMe2NAr-κ2C,N}] (Cp* ) η5-C5-
Me5; Ar ) 2,6-Me2C6H3; R ) H, x ) 1, R′ ) Me, 2; CH2-
Ph, 4; x ) 2, R′ ) Me, 3; R ) Ph, x ) 1, R′ ) CH2Ph, 6;
x ) 2, R′ ) Me, 5). Reaction of 1a with 1 equiv of
isocyanides RNC (R ) 2,6-Me2C6H3; tBu) probably takes
place through the initial formation of nonstable adducts
whose intramolecular rearrangement gave a dichloro
imido tantalum compound [TaCp*Cl2(NAr)] (Cp* ) η5-
C5Me5; Ar ) 2,6-Me2C6H3, 9) and the s-trans-vinylaza-
cumulenes R-NdCdCH-CHdCMe2 (R ) 2,6-Me2C6H3,
10; tBu, 11). When a toluene solution of 2 was treated
with 2 equiv of isocyanides, the organic product 10 (R
) 2,6-Me2C6H3) or 11 (R ) tBu) and the chloro imido
η2-iminoacyl complexes [TaCp*Cl(NAr){η2-C(Me)dNR}]
(Cp* ) η5-C5Me5; R ) 2,6-Me2C6H3, 12; tBu, 13) were
obtained, probably via coordination, insertion, and in-
tramolecular rearrangement processes. Treatment of
the dimethyl azatantalacyclopentene 3 with 1 equiv of
2,6-Me2C6H3NC produces the alkenylenamido imido
methyl derivative [TaCp*Me(NAr){η1-N(Ar)-C(Me)d
CH-CHdCMe2}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3,
14), but the intermediate species were not observed
3
[t, 1H, JH-H ) 7.2 Hz, Ta-N(2,6-Me2C6H3)-], 2.99(s, 3H),
2.14[s, 3H, Ta-N(2,6-Me2C6H3)-], 1.81(s, 15H, C5Me5), 1.14-
(s, 3H), 0.97(s, 3H, dCH-CMe2-), 0.73(s, 3H, Ta-Me). 13C-
{1H} NMR (δ ppm, in benzene-d6): 204.6(Ta-CHdCH-),
147.2(Ta-CHdCH-), 157.4(C1), 138(C2,6), 132.5(C3,5), 128.9-
[C4, Ta-N(2,6-Me2C6H3)-], 121.9(C5Me5), 81.3(dCH-CMe2-),
51.64(Ta-Me), 31.5, 25.7(dCH-CMe2-), 22.7, 21.3[Ta-N(2,6-
Me2C6H3)-], 11.84(C5Me5). Anal. Calcd for C24H35-
ClNTa: C, 52.03; H, 6.37; N, 2.52. Found: C, 52.09; H, 6.38;
N, 2.62.
Synthesis of [TaCp*Me2(CHCHCMe2NAr-K2C,N)] (Cp*
) η5-C5Me5; Ar ) 2,6-Me2C6H3, 3). Under rigorously anhy-
drous conditions, a 3 M solution of MgClMe in THF (1 mL, 3
mmol) was added at -78 °C to a solution of 1a (0.75 g, 1.30
mmol) in toluene (40 mL), and the reaction mixture was stirred
for 30 min. It was warmed to room temperature for 6 h, the
solvent evaporated to dryness, and the residue extracted with
hexane (3 × 10 mL). The solution was concentrated to ca. 10
mL and cooled to -40 °C overnight to give 3 as yellow crystals.
The data for 3 follow. Yield: 0.60 g (83%). IR (KBr, νj cm-1):
2915(vs), 1844(w), 1653(w), 1566(m), 1488(m), 1456(s), 1423-
(s), 1374(s), 1347(m), 1302(w), 1249(w), 1232(w), 1189(vs),
1164(s), 1097(m), 1068(w), 1024(m), 957(m), 898(s), 810(m),
768(s), 746(m), 697(w), 668(w), 597(w), 566(w), 543(w), 499-
(m), 484(m), 440(m). 1H NMR (δ ppm, in benzene-d6): 7.98(d,
1H), 7.04(d, 1H, 2JH-H ) 10.9 Hz, Ta-CHdCH-), 7.12(d, 2H),
6.95[t, 1H, 3JH-H) 7.5 Hz, Ta-N(2,6-Me2C6H3)-], 2.50[br, 6H,
Ta-N(2,6-Me2C6H3)-], 1.74(s, 15H, C5Me5), 1.11(br, 6H, d
CH-CMe2-), 0.20(br, 6H, Ta-Me2). 13C{1H} NMR (δ ppm, in
benzene-d6): 203.9(Ta-CHdCH-), 146.5(Ta-CHdCH-), 154.7-
(C1), 129.9(C2,6), 128.6(C3,5), 124.1[C4, Ta-N(2,6-Me2C6H3)-],
119.1(C5Me5), 79.5(dCH-CMe2-), 51.6(Ta-Me2), 31.8(dCH-
CMe2-), 21.6[Ta-N(2,6-Me2C6H3)-], 11.4(C5Me5). Anal. Calcd
for C25H38NTa: C, 56.28; H, 7.17; N, 2.62. Found: C, 56.16;
H, 7.03; N, 2.66.
1
when the reaction was followed by H NMR spectros-
copy. 14 reacts with 1 equiv of isocyanide, giving the
imido η2-iminoacyl methyl derivative [TaCp*Me(NAr)-
(η2-C{CH(CMedNAr)(CHdCMe2)}dNAr)] (Cp* ) η5-C5-
Me5; Ar ) 2,6-Me2C6H3, 15) in quantitative yield.
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-C5Me5)Cl2(CRCHCMe2-
NAr-κ2C,N)])] (Ar ) 2,6-Me2C6H3; R ) H, 1a; Ph, 1b)23 and
the alkylating reagent [Mg(CH2Ph)2(thf)2]41 were prepared as
described previously. Reagent grade MCl2-xRx (M ) Zn, R )
Me, x ) 2, 2 M in toluene; M ) Mg, R ) Me, x ) 1, 3 M in
THF; Aldrich) and RNC (R ) 2,6-Me2C6H3, Fluka; tBu,
Aldrich) were purchased from commercial sources and were
used without further purification.
Synthesis of [TaCp*Cl(CH2Ph)(CHCHCMe2NAr-K2C,N)]
(Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 4). Toluene (40 mL) was
added to a mixture of 1a (0.50 g, 0.87 mmol) and Mg(CH2Ph)2-
(thf)2 (0.30 g, 0.87 mmol) at room temperature, and the mixture
was stirred for 12 h under rigorously anhydrous conditions
(glovebox). The suspension was removed by filtration, and the
resulting solution was evaporated to dryness. The residue was
extracted with a toluene/hexane mixture (2 × 15 mL) and the
solution concentrated to ca. 10 mL and cooled to -40 °C
overnight to give a microcrystalline red solid identified as 4.
The data for 4 follow. Yield: 0.36 g (66%). IR (KBr, νj cm-1):
2964(vs), 2907(s), 1650(w), 1586(m), 1488(s), 1457(vs), 1375-
(s), 1314(w), 1259(w), 1205(m), 1176(vs), 1160(s), 1099(s), 1024-
(m), 955(w), 910(m), 879(w), 813(m), 768(s), 755(s), 697(s),
Samples for IR spectroscopy were prepared as KBr pellets
and recorded on a Perkin-Elmer Spectrum 2000 spectropho-
tometer (4000-400 cm-1). NMR spectra were recorded on
Unity-300 and Varian Unity-Plus 500 spectrometers (“Varian
NMR Systems”); chemical shifts were referenced to the solvent
1
666(m), 601(w), 544(m), 507(m), 428(m). H NMR (δ ppm, in
2
benzene-d6): 7.76(d, 1H), 7.36(d, 1H, JH-H ) 10.8 Hz, Ta-
CHdCH-), 7.32(m, 2Hm), 7.28(m, 2Ho), 6.912(tt, 1Hp, Ta-
(41) Schrock, R. R. J. Organomet. Chem.1976, 122, 209-225.
CH2C6H5), 7.12(dd, 1H), 7.01(dd, 1H, 4JH-H ) 1.13 Hz), 6.905[t,

Azatantalacyclopentene Complexes
Organometallics, Vol. 24, No. 14, 2005 3559
3
1H, JH-H) 7.5 Hz, Ta-N(2,6-Me2C6H3)-], 2.08(s, 3H), 1.98-
CMe2), not observed(-CHdCMe2), 52.2(dCdCH-), 25.9, 18.3-
(-CHdCMe2), 18.7(2,6-Me2H3C6-Nd). The data for 11 follow.
1H NMR (δ ppm, in benzene-d6): 5.64(d, 1H, 3JH-H) 10.8 Hz,
[s, 3H, Ta-N(2,6-Me2C6H3)-], 1.76(s, 15H, C5Me5), 1.69, 1.40-
(AB, 2H, JH-H ) 10.6 Hz, Ta-CH2C6H5), 1.01(s, 3H), 0.85(s,
2
3H, dCH-CMe2-). 13C{1H} NMR (δ ppm, in benzene-d6):
203.4(Ta-CHdCH-), 148.5(Ta-CHdCH-), 156(C1), 138.5,
133.1(C2,6), 129.8, 127.3(C3,5), 124.6[C4, Ta-N(2,6-Me2C6H3)-],
148.6(C1), 130.7(C2,6), 127.4(C3,5), 123.4(C4, Ta-CH2C6H5),
122.5(C5Me5), 82.3(dCH-CMe2-), 78.5(Ta-CH2C6H5), 29.4,
24.4(dCH-CMe2-), 22.4, 22.2[Ta-N(2,6-Me2C6H3)-], 12.1-
(C5Me5). Anal. Calcd for C30H39ClNTa: C, 57.19; H, 6.24; N,
2.22. Found: C, 57.49; H, 6.52; N, 2.35.
-CHdCMe2), 4.60(d, 1H, JH-H ) 10.8 Hz, dCdCH-), 1.64-
3
(s, 3H), 1.49(s, 3H, -CHdCMe2), 1.15(s, 9H, Me3C-Nd).13C-
{1H} NMR (δ ppm, in benzene-d6): 186.7(dCdCH-), 116.2(-
CHdCMe2), 58.3(Me3C-Nd), 55.8(dCdCH-), 30(Me3C-Nd),
25.8, 17.9(-CHdCMe2).
Reaction of 2 with 2,6-Me2C6H3NC. A solution of 2 (0.20
g, 0.36 mmol) in toluene (20 mL) was treated with 2,6-
Me2C6H3NC (0.09 g, 0.72 mmol) under rigorously anhydrous
conditions. The mixture was heated for 30 h at 50 °C and then
filtered. The filtrate was concentrated to dryness and the
residue extracted with hexane (2 × 10 mL). The solution was
concentrated to ca. 5 mL and cooled to -40 °C to give a yellow
microcrystalline solid identified as a mixture of 10 and the
η2-iminoacyl complex [TaCp*Cl(NAr){η2-C(Me)dNAr}] (Cp* )
η5-C5Me5; Ar ) 2,6-Me2C6H3, 1224) in a 1:1 ratio.
Synthesis of [TaCp*Me2{C(Ph)CHCMe2NAr-K2C,N}]
(Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 5). A sample of 1b (0.40
g, 0.61 mmol) was dissolved in 30 mL of toluene in a Schlenk
tube and at -78 °C was treated with a 3 M solution of MgClMe
in THF (0.50 mL, 1.50 mmol). The mixture was stirred at low
temperature 6 h, and after, the resulting suspension was
decanted and filtered. The filtrate was concentrated to ca. 10
mL and cooled to -40 °C to give 5 as a microcrystalline yellow
solid.
Reaction of 2 with tBuNC. tBuNC (0.11 mL, 1.02 mmol)
was added to a solution of 2 (0.25 g, 0.45 mmol) in toluene (20
mL) at room temperature, and the mixture was stirred for 20
h. The resulting solution was filtered and the filtrate concen-
trated to dryness. The residue solid was washed with hexane
(2 × 10 mL), and the resulting yellow suspension was decanted
and filtered. The yellow microcrystalline solid was dried in
vacuo and identified as the η2-iminoacyl complex [TaCp*Cl-
(NAr){η2-C(Me)dNtBu}] (Cp* ) η5-C5Me5, 13). The filtrate was
concentrated to ca. 5 mL and cooled to -40 °C to give the
organic product 11 impurified with a small portion of the
complex 13.
The data for 5 follow. Yield: 0.22 g (59%). 1H NMR (δ ppm,
in benzene-d6): 7.28-7.01[d, 2H, JH-H ) 7.5 Hz, Ta-N(2,6-
3
Me2C6H3)-], 7.28-7.01[m, 5H, Ta-C(C6H5)dCH-], 6.95[t, 1H,
3JH-H ) 7.5 Hz, Ta-N(2,6-Me2C6H3)-], 6.76[s, 1H, Ta-C(Ph)d
CH-], 3.06(s, 3H), 2.12[s, 3H, Ta-N(2,6-Me2C6H3)-], 1.66(s,
15H, C5Me5), 1.30(s, 3H), 0.94(s, 3H, dCH-CMe2-), 0.68(s,
3H), -0.13(s, 3H, Ta-Me2).
Synthesis of [TaCp*Cl(CH2Ph){C(Ph)CHCMe2NAr-
K2C,N}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 6). At room
temperature, toluene (50 mL) was added to a mixture of
compound 1b (0.40 g, 0.61 mmol) and Mg(CH2Ph)2(thf)2 (0.10
g, 0.30 mmol). The mixture was stirred for 12 h, the magne-
sium chloride, MgCl2, formed removed by filtration, and the
filtrate concentrated to a volume of ca. 10 mL. Cooling at -40
°C overnight led to the deposition of a microcrystalline yellow
solid identified as 6.
The data for 13 follow. Yield: 0.13 g (51%). IR (KBr, νj cm-1):
2908(s), 1890(w), 1828(w), 1772(w), 1646(s), 1588(m), 1459-
(vs), 1366(s), 1330(vs), 1243(m), 1200(s), 1121(m), 1095(m),
1026(m), 980(m), 851(m), 805(w), 759(s), 650(w), 561(w), 508-
1
(w), 463(m), 412(w). H NMR (δ ppm, in benzene-d6): 7.04(d,
3
2H), 6.71[t, 1H, JH-H) 7.5 Hz, TadN(2,6-Me2C6H3)], 2.51[s,
The data for 6 follow. Yield: 0.31 g (72%). IR (KBr, νj cm-1):
2913(vs), 1593(m), 1487(s), 1458(vs), 1375(s), 1322(vs), 1263-
(m), 1204(w), 1158(m), 1098(m), 1068(m), 1026(s), 984(m), 917-
(w), 867(w), 803(m), 765(vs), 701(vs), 588(m), 507(w), 484(w).
1H NMR (δ ppm, in benzene-d6): 7.12-6.86[several phenyl,
10H, Ta-CH2C6H5, Ta-C(C6H5)dCH-], 6.98(d, 2H), 6.69[t,
6H, TadN(2,6-Me2C6H3)], 2.38[s, 3H, Ta-C(Me)dNtBu], 1.83-
(s, 15H, C5Me5), 1.22[s, 9H, Ta-C(Me)dN(CMe3)]. 13C{1H}
NMR (δ ppm, in benzene-d6): 233[Ta-C(Me)dNtBu], 154.4-
(C1), 131.9(C2,6), 127.2(C3,5), 120.8[C4, TadN(2,6-Me2-
C6H3)], 115(C5Me5), 63.9[Ta-C(Me)dN(CMe3)], 29.9[Ta-
C(Me)dN(CMe3)], 20.1[Ta-C(Me)dN(CMe3)], 19.9[TadN(2,6-
Me2C6H3)], 11.1(C5Me5). Anal. Calcd for C24H36ClN2Ta: C,
50.66; H, 6.38; N, 4.92. Found: C, 50.99; H, 6.51; N, 5.09.
Synthesis of [TaCp*Me(NAr){η1-N(Ar)-C(Me)dCH-
CHdCMe2}] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 14). A
stirred yellow solution of 3 (0.40 g, 0.75 mmol) in toluene (20
mL) was treated with 2,6-Me2C6H3NC (0.13 g, 1.00 mmol)
under rigorously anhydrous conditions for 3 h. The color of
the mixture changed quickly from yellow to dark red. The
solution was filtered, concentrated to ca. 5 mL, and cooled to
-40 °C to give 14 as a brown microcrystalline solid.
3
1H, JH-H ) 7.5 Hz, Ta-N(2,6-Me2C6H3)-], 5.60[s, 1H, Ta-
C(Ph)dCH-], 2.67, 2.61(AB, 2H, 2JH-H ) 13 Hz, Ta-CH2Ph),
2.25[s, 6H, Ta-N(2,6-Me2C6H3)-], 1.84(s, 15H, C5Me5), 0.96-
(s, 3H), 0.83(s, 3H, dCH-CMe2-). 13C{1H} NMR (δ ppm, in
benzene-d6): 209.6[Ta-C(Ph)dCH-], 187.7[Ta-C(Ph)dCH-],
149-131[several phenyl, Ta-CH2C6H5, Ta-C(C6H5)dCH-],
138.4(C1), 126.4(C2,6), 125.2(C3,5), 123.3[C4, Ta-N(2,6-Me2-
C6H3)-], 117.9(C5Me5), 50(dCH-CMe2-), 41.3(Ta-CH2C6H5),
29.5, 28.2(dCH-CMe2-), 19.5[Ta-N(2,6-Me2C6H3)-], 11.5-
(C5Me5). Anal. Calcd for C36H43ClNTa: C, 61.23; H, 6.14; N,
1.98. Found: C, 61.15; H, 6.05; N, 2.08.
The data for 14 follow. Yield: 0.29 g (58%). IR (KBr, νj cm-1):
2912(vs), 1709(w), 1587(m), 1462(vs), 1432(s), 1376(s), 1305-
(vs), 1251(w), 1213(w), 1191(s), 1151(s), 1098(m), 1024(m),
980(w), 899(m), 849(w), 762(s), 673(w), 593(m), 526(w), 480-
(m), 397(w). 1H NMR (δ ppm, in benzene-d6): 7.00(dd, 2H),
Reaction of 1a with Isocyanides RNC (R ) 2,6-
Me2C6H3; tBu). RNC (0.52 mmol; R ) 2,6-Me2C6H3, 0.07 g;
tBu, 0.06 mL) was added at room temperature to a solution of
1a (0.30 g, 0.52 mmol) in toluene (25 mL), and the mixture
was stirred for 24 h (R ) 2,6-Me2C6H3) and 10 h (R ) tBu).
The reaction was checked by 1H NMR spectroscopy until total
conversion of the tantalum starting complex. The reddish
solution was evaporated to dryness, and the 1H NMR analysis
of the crude residue showed this to consist of a mixture of
[TaCp*Cl2{N(2,6-Me2C6H3)}] (Cp* ) η5-C5Me5, 95f) and the
organic material s-trans-R-NdCdCH-CHdCMe2 (R ) 2,6-
Me2C6H3, 10; tBu, 11) in a 1:1 molar ratio.
3
6.79(dd, 1H, 4JH-H)1.98 Hz), 6.83[t, 1H, JH-H) 7.4 Hz, Tad
N(2,6-Me2C6H3)], 6.88(d, 2H), 6.60[t, 1H, 3JH-H ) 7.4 Hz, Ta-
4
N(2,6-Me2C6H3)], 6.01(dsept, 1H, JH-H ) 1.43 Hz, -CHd
3
CMe2), 5.55[d, 1H, JH-H ) 10.9 Hz, -C(Me)dCH-], 2.48(s,
3H), 2.32[s, 3H, TadN(2,6-Me2C6H3)], 2.17[br, 6H, Ta-N(2,6-
Me2C6H3)], 1.77(s, 15H, C5Me5), 1.76[s, 3H, -C(Me)dCH-],
1.67(br, 6H, -CHdCMe2), 0.97(s, 3H, Ta-Me). 13C{1H} NMR
(δ ppm, in benzene-d6): 153.2[C1, TadN(2,6-Me2C6H3)], 151.7-
[C1, Ta-N(2,6-Me2C6H3)], 136, 134.2, 130.9, 129.6, 128.1,
127.2, 125.1, 121.9[several phenyl carbons, TadN(2,6-Me2C6H3),
Ta-N(2,6-Me2C6H3)], 145.6[-N-C(Me)dCH-], 133.2(-CHd
CMe2), 122.7(-CHdCMe2), 115.7(C5Me5), 108.4[-C(Me)dCH-],
34.8(Ta-Me), 26.4, 18.6(-CHdCMe2), 19.99, 19.94[TadN(2,6-
Me2C6H3)], 19.85[Ta-N(2,6-Me2C6H3)], 17.8[-C(Me)dCH-],
The data for 10 follow. 1H NMR (δ ppm, in benzene-d6):
3
6.86(m, 3H, 2,6-Me2H3C6-Nd), 5.66(dsept, 1H, JH-H ) 10.7
Hz, -CHdCMe2), 4.60(d, 1H, 3JH-H ) 10.7 Hz, -NdCdCH-),
2.24(s, 6H, 2,6-Me2H3C6-Nd), 1.65(s, 3H), 1.47(s, 3H, -CHd
CMe2). 13C{1H} NMR (δ ppm, in benzene-d6): 190.8(dCdCH-),
150-131.5(several phenyl, 2,6-Me2H3C6-Nd), 114.5(-CHd

3560 Organometallics, Vol. 24, No. 14, 2005
Galakhov et al.
Table 2. Crystal Data and Structure Refinement
for Compound 3
C{CH(CMedN(2,6-Me2C6H3)(CHdCMe2)}dN(2,6-Me2C6H3)],
1.96(s, 15H, C5Me5), 1.57(s, 3H, -CMedNAr), 1.46(s, 3H), 1.38-
(s, 3H, Me2CdCH-CH-), 0.56(s, 3H, Ta-Me). 13C{1H} NMR
(δ ppm, in benzene-d6): 239.5[Ta-C{CH(CMedN(2,6-Me2C6H3)-
(CHdCMe2)}dN(2,6-Me2C6H3)], 169.1[-CMedN(2,6-Me2C6H3)],
155.1-119.9[several phenyl carbons, TadN(2,6-Me2C6H3), Ta-
C{CH(CMedN(2,6-Me2C6H3)(CHdCMe2)}dN(2,6-Me2C6H3)],
119.8(Me2CdCH-CH-), not observed (Me2CdCH-CH-),
113.4(C5Me5), 60.1(Me2CdCH-CH-), 25.7, 17.9(Me2CdCH-
CH-), 21.3(Ta-Me), 19.4[-CMedN(2,6-Me2C6H3)], 20.2, 20.1,
18.8, 18.6, 18.3, 17.6[TadN(2,6-Me2C6H3), Ta-C{CH(CMed
N(2,6-Me2C6H3)(CHdCMe2)}dN(2,6-Me2C6H3)], 11.5(C5Me5).
Crystal Structure Determination of Compound 3.
Crystallographic and experimental details of the crystal
structure determinations are given in Table 2. Suitable
crystals for the X-ray analyses of complex 3 were obtained by
recrystallization from a hexane solution and then covered with
mineral oil and mounted in the N2 stream in a Bruker-Nonius
Kappa CCD diffractometer. Data were collected using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). Data
collection was performed at 200 K (see Table 2) with an
exposure time of 6 s per frame (4 sets, 582 frames). Raw data
were corrected for Lorentz and polarization effects.
chem formula
C25H38NTa
533.51
fw
T (K)
200(2)
λ (Mo KR), Å
0.71073
cryst syst, space group
orthorhombic, P212121
8.3124(10)
a, Å
b, Å
c, Å
V, Å3
Z
10.5190(7)
26.0587(18)
2278.5(4)
4
F
calcd, g cm-3
1.555
µ, mm-1
4.883
cryst size, mm
F(000)
0.35 × 0.2 × 0.2
1072
θ range, deg
index ranges
5.01 to 27.52
-4 e h e 10,
-13 e k e 13,
-31 e l e 33
10 010
5155 [R(int) ) 0.0662]
4588
no. of data collected
no. of unique data
no. of obsd reflns [I >2σ (I)]
absorp corr
semiempirical from
equivalents
1.284 and 0.821
252
max. and min. transmn
no. of params refined
The structure was solved by direct methods, completed by
subsequent difference Fourier techniques, and refined by full-
matrix least squares on F2 (SHELXL-97).42 Anisotropic ther-
mal parameters were used in the last cycles of refinement for
the non hydrogen atoms. Hydrogen atoms were included from
geometrical calculations and refined using a riding model. All
the calculations were made using the WINGX system.43
goodness-of-fit on F2
1.036
final R indices [I > 2σ(I)]a
R indices (all data)a
R1 ) 0.0351, wR2 ) 0.0644
R1 ) 0.0454, wR2 ) 0.0670
0.807 and -1.032
largest diff peak and hole, e Å-3
2 2
a R1 ) ∑|Fo| - |Fc||/[∑|Fo|]; wR2 ) {[∑w(Fo2 - Fc)2]/[∑w(Fo ) ]}1/2
.
Acknowledgment. We thank the MCYT (Project
BQU 2002-03754) for its financial support of this
research.
10.9(C5Me5). Anal. Calcd for C34H47N2Ta: C, 61.45; H, 7.12;
N, 4.21. Found: C, 61.22; H, 6.80; N, 4.41.
Synthesis of [TaCp*Me(NAr)(η2-C{CH(CMedNAr)(CHd
CMe2)}dNAr)] (Cp* ) η5-C5Me5; Ar ) 2,6-Me2C6H3, 15).
Benzene-d6 (0.60 mL) was added to a mixture of complex 14
(0.035 g, 0.052 mmol) and 2,6-Me2C6H3NC (0.007 g, 0.052
mmol) in a NMR valved tube. The reaction was monitored by
1H NMR spectroscopy until no further change was observed.
After 15 h the spectrum showed the presence of 15 in
quantitative yield.
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 3 (Tables S1-S5). This material is
available free of charge via the Internet at http://pubs.acs.org.
The data for 15 follow. 1H NMR (δ ppm, in benzene-d6):
7.08-6.56[m, 9H, TadN(2,6-Me2C6H3), Ta-C{CH(CMedN(2,6-
Me2C6H3)(CHdCMe2)}dN(2,6-Me2C6H3)], 5.58(dsept, 1H, 3JH-H
OM050289Z
(42) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Analysis (Release 97-2); University of Go¨ttingen: Go¨ttingen, Ger-
4
) 10.7 Hz, JH-H ) 1.2 Hz, Me2CdCH-CH-), 5.01(d, 1H,
many, 1998.
3JH-H ) 10.7 Hz, Me2CdCH-CH-), 2.49(s, 6H), 2.06(s, 3H),
1.93(s, 3H), 1.79(s, 3H), 1.78[s, 3H, TadN(2,6-Me2C6H3), Ta-
(43) WINGX.; Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837-
838.