Insertion of CO and CNR into tantalum-methyl bonds of imido(pentamethylcyclopentadienyl)tantalum complexes. X-ray crystal structures of [TaCp*(NR)-Me{η2-C(Me)=NR}] and [TaCp*Cl(O){η2-C(Me)=NR}] (R = 2,6-Me2C6H<s

Article abstract of DOI:10.1021/om9602015

[TaCp*Cl₂{N(2,6-Me₂C₆H ₃)}] reacts with 2 equiv of LiMe at -78 °C to give the imido dimethyl complex TaCp*Me₂{N(2,6-Me₂C₆H₃)} (1) in almost quantitative yield, whereas

Full text of DOI:10.1021/om9602015

Organometallics 1996, 15, 3579-3587
3579
In ser tion of CO a n d CNR in to Ta n ta lu m -Meth yl Bon d s
of Im id o(p en ta m eth ylcyclop en ta d ien yl)ta n ta lu m
Com p lexes. X-r a y Cr ysta l Str u ctu r es of [Ta Cp *(NR)-
Me{η2-C(Me)dNR}] a n d [Ta Cp *Cl(O){η2-C(Me)dNR}] (R )
2,6-Me2C6H3)†
Manuel Go´mez, Pilar Go´mez-Sal,‡ Gerardo J ime´nez, Avelino Mart´ın,‡
Pascual Royo,* and J avier Sa´nchez-Nieves
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´ de Henares,
Campus Universitario, E-28871 Alcala´ de Henares, Spain
Received March 18, 1996X
[TaCp*Cl2{N(2,6-Me2C6H3)}] reacts with 2 equiv of LiMe at -78 °C to give the imido
dimethyl complex TaCp*Me2{N(2,6-Me2C6H3)} (1) in almost quantitative yield, whereas the
monomethyl imido derivatives [TaCp*MeX{N(2,6-Me2C6H3)}] (X ) Cl (2), OC6H3Me2 (3))
can be prepared by addition of HX (X ) Cl, OC6H3Me2) to toluene solutions of [TaCp*Me-
(NR){NR(CMedCMe2)}] (R ) 2,6-Me2C6H3) with elimination of the corresponding imine
RNdCMeCHMe2. Complex 1 reacts with CO to give the dinuclear ene diolate complex
[TaCp*{N(2,6-Me2C6H3)Me}]2{µ-η2-OC(Me)dC(Me)O} (5) via intermolecular coupling between
two acyl carbon atoms of the intermediate η2-acyl complex TaCp*Me{N(2,6-Me2C6H3)}{η2-
C(Me)dO} (4). However, when the same reaction was carried out with the chloro imido
methyl derivative 2, the unexpected oxo η2-iminoacyl complex [TaCp*Cl(O){η2-C(Me)dN-
(2,6-Me2C6H3)}] (7) was obtained via the barely stable intermediate η2-acyl complex [TaCp*Cl-
{N(2,6-Me2C6H3)}{η2-C(Me)dO}] (6). The analogous reaction of [TaCp*Cl2Me2] with CO leads
to the formation of the dichloro oxotantalacyclopropane complex [TaCp*Cl2(η2-CMe2O)] (8),
but the acyl intermediate species was not observed. Similarly, the azatantalacyclopropane
complexes [TaCp*XMe(η2CMe2-NR)] react with 1 equiv of CO to form the stable enolate
derivatives [TaCp*X(NR){OC(Me)dCMe2}] (X ) Cl (9), Me (10); R ) 2,6-Me2C6H3). The
stable 18-electron imido η2-iminoacyl derivatives [TaCp*X(NR){η2-C(Me)dNR}] (X ) Me (11),
Cl (12), OC(Me)dCMe2 (13); R ) 2,6-Me2C6H3) are formed when the isocyanide RNC (1 equiv)
is added to toluene solutions of the imido complexes 1, 2, and 10, respectively. All compounds
were characterized by IR and NMR (1H and 13C), and the molecular structures of 7 and 11
were studied by X-ray diffraction methods.
In tr od u ction
two complexes transforms the amido into an iminoacyl
ligand containing a terminal ketimine function.
We herein report the synthesis of new imido(penta-
methylcyclopentadienyl)tantalum complexes, their re-
activity with CO and CNR, and the intramolecular
rearrangements of the resulting complexes. The X-ray
molecular structures of the complexes [TaCp*Cl(O){η2-
C(Me)dNR}] and [TaCp*(NR)Me{η2-C(Me)dNR}] (R )
2,6-Me2C6H3) are also described.
One of the most important organometallic reactions,
with many synthetic applications, is the transfer of alkyl
groups from transition metals to coordinated unsatur-
ated molecules, such as carbon monoxide1 and isocya-
nides,2 to give acyl and iminoacyl complexes whose
reactivity3 is well documented. Recently, we have
reported a systematic study4 of isocyanide insertion
reactions into tantalum-methyl bonds of different halo-
methyl(pentamethylcyclopentadienyl)tantalum com-
plexes TaCp*Cl4-nMen, which led to the isolation of η2-
iminoacyl (n ) 1), dichloro azatantalacyclopropane (n
) 2), and chloro and methyl imido alkenyl amido (n )
3, 4) complexes. Further attack of the isocyanide at the
terminal olefinic carbon of the alkenyl moiety of the last
(3) (a) Takahashi, Y.; Onoyama, N.; Ishikawa, Y.; Motojima, S.;
Sugiyama, K. Chem. Lett. 1978, 525. (b) Wolczanski, P. T.; Bercaw, J .
E. J . Am. Chem. Soc. 1979, 101, 6450. (c) Wolczanski, P. T.; Bercaw,
J . E. Acc. Chem. Res. 1980, 13, 121. (d) Chiu, K. W.; J ones, R. A.;
Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B. J . Am. Chem. Soc.
1980, 102, 7978. (e) Chiu, K. W.; J ones, R. A.; Wilkinson, G.; Galas,
A. M. R.; Hursthouse, M. B. J . Chem. Soc., Dalton Trans. 1981, 2088.
(f) Mayer, J . M.; Curtis, C. J .; Bercaw, J . E. J . Am. Chem. Soc. 1983,
105, 2651. (g) Nugent, W. A.; Overall, D. W.; Holmes, S. J . Organo-
metallics 1983, 2, 161. (h) Chamberlain, L. R.; Rothwell, I. P.; Huffman,
J . C. J . Chem. Soc., Chem. Commun. 1986, 1203. (i) Sielisch, T.;
Behrens, U. J . Organomet. Chem. 1986, 310, 179. (j) Brunner, H.;
Wachter, J .; Schmidbauer, J . Organometallics 1986, 5, 2212. (k) Durfee,
L. D.; Fanwick, P. E.; Rothwell, I. P. J . Am. Chem. Soc. 1987, 109,
4720. (l) Chamberlain, L. R.; Steffey, B. D.; Rothwell, I. P.; Huffman,
J . D. Polyhedron 1989, 8, 341. (m) Durfee, L. D.; Hill, J . E.; Fanwick,
P. E.; Rothwell, I. P. Organometallics 1990, 9, 75.
† Dedicated to Professor Rafael Uso´n on the occasion of his 70th
birthday.
‡ X-ray diffraction studies.
X Abstract published in Advance ACS Abstracts, J uly 15, 1996.
(1) (a) Calderazzo, F. Angew. Chem., Int. Ed. Engl. 1977, 16, 299.
(b) Wood, C. D.; Schrock, R. R. J . Am. Chem. Soc. 1979, 101, 5421.
(c) Kulhmann, E. J .; Alexander, J . J . Coord. Chem. Rev. 1980, 33,
195.
(4) (a) Galakhov, M. V.; Go´mez, M.; J ime´nez, G.; Royo, P.; Pellin-
ghelli, M. A.; Tiripicchio, A. Organometallics 1995, 14, 1901. (b)
Galakhov, M. V.; Go´mez, M.; J ime´nez, G.; Royo, P.; Pellinghelli, M.
A.; Tiripicchio, A. Organometallics 1995, 14, 2843.
(2) (a) Treitchel, P. M. Adv. Organomet. Chem. 1973, 11, 21. (b)
Andersen, R. A. Inorg. Chem. 1979, 18, 2928.
S0276-7333(96)00201-4 CCC: $12.00 © 1996 American Chemical Society

3580 Organometallics, Vol. 15, No. 16, 1996
Go´mez et al.
Sch em e 1a
a
Reagents and conditions: (i) 2 equiv LiMe (1.6 M in OEt2), toluene, -78 °C, 30 min, room temperature, 2 h; (ii) X ) Cl, 1
equiv HCl (1 M in OEt2), toluene, -78 °C, 20 min, X ) OC6H3Me2, sealed NMR tube, 1 equiv 2,6-Me2C6H3(OH), benzene-d6, 60
°C, 3 days.
Sch em e 2a
a
Reagents and conditions: (i) sealed NMR tube, CO (1 atm), chloroform-d, N2(l), fast; (ii) room temperature; (iii) CO (1 atm),
toluene, room temperature, 16 h.
Resu lts a n d Discu ssion
(see Experimental Section) are consistent with the
expected pseudotetrahedral structure.8
Syn th esis of Im id o Com p lexes. Reaction of [Ta-
Cp*Cl2{N(2,6-Me2C6H3}] with 2 equiv of LiMe at -78
°C afforded the imido dimethyl complex [TaCp*Me2-
{N(2,6-Me2C6H3)}] (1) in almost quantitative yield.
When the same reaction was carried out using 1 equiv
of LiMe, the same redistribution reaction observed for
other halotantalum complexes5 takes place for the
expected halo methyl complex to give a 1:1 mixture of
1 and the starting product.
Rea ction s w ith CO. Complex 1 reacts with carbon
monoxide (1 atm) at room temperature in toluene to give
the dinuclear ene diolate complex [{TaCp*(NR)Me}2{µ-
η2-OC(Me)dC(Me)O}] (R ) 2,6-Me2C6H3; 5) in good
yield.
As shown in Scheme 2, this reaction takes place by
intermolecular coupling between two acyl carbon atoms
of the intermediate η2-acyl complex [TaCp*Me{N(2,6-
Me2C6H3)}{η2-C(Me)dO}] (4). Formation of complex 4
can be observed when the reaction is followed by NMR
spectroscopy at low temperature. The NMR spectrum
As shown in Scheme 1, the monomethyl imido deriva-
tives [TaCp*MeX{N(2,6-Me2C6H3)}] (X ) Cl (2), OC6H3-
Me2 (3)) are easily obtained when 1 equiv of the
appropriate HX reagent is added at room temperature
(X ) Cl) or at 60 °C (X ) OC6H3Me2) to toluene solutions
of TaCp*(NR)Me[NR(CMedCMe2)] with elimination of
the corresponding imine RNdCMeCHMe2 (R ) 2,6-
Me2C6H3).
1
in CDCl3 at -50 °C shows one H resonance at δ 3.13
ppm and one 13C{1H} signal at δ 320 ppm, as expected
for the η2-C(Me)dO ligand.9 Complex 4 is quantita-
tively transformed into the ene diolate derivative 5 on
heating to room temperature, preventing its isolation
as a solid.
The new imido complexes show a ν(TadN)7 IR ab-
1
(7) (a) Bradley, D. C.; Hursthouse, M. B.; Howes, A. J .; J elfs, A. N.
de M.; Runnacles, J . D.; Thornton-Pett, M. J . Chem. Soc., Dalton Trans.
1991, 841. (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.
(8) (a) Gibson, V. C.; Poole, A. D.; Siemeling, U.; Williams, D. N.;
Clegg, W.; Hockless, D. C. R. J . Organomet. Chem. 1993, 462, C12. (b)
Galakhov, M. V.; Go´mez, M.; J ime´nez, G.; Pellinghelli, M. A.; Royo,
P.; Tiripicchio, A. Organometallics 1994, 13, 1564.
sorption at ∼1322 cm-1. Their H and 13C NMR spectra
(5) (a) Curtis, M. D.; Real, J .; Hirpo, W.; Butler, W. M. Organome-
tallics 1990, 9, 66. (b) Go´mez, M.; J ime´nez, G.; Royo, P.; Pellinghelli,
M. A.; Tiripicchio, A. J . Organomet. Chem. 1992, 439, 309.
(6) (a) Schrock, R. R. J . Am. Chem. Soc. 1974, 96, 6796. (b) Andersen,
R. A. Inorg. Chem. 1979, 18, 3622. (c) Chamberlain, L. R.; Rothwell, I.
P.; Folting, K.; Huffman, J . C. J . Chem. Soc., Dalton Trans. 1987,
155.
(9) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059.

Insertion of CO and CNR into Ta-Me Bonds
Organometallics, Vol. 15, No. 16, 1996 3581
Sch em e 3a
a
Reagents and conditions: (i) sealed NMR tube, CO (1 atm), chloroform-d, -40 °C, fast; (ii) room temperature; (iii) CO (1
atm), toluene, room temperature, 12 h.
When the same reaction with CO was carried out
using the chloro methyl derivative 2 as the starting
compound, the expected imido acyl compound was not
obtained, since it was spontaneously converted into the
oxo η2-iminoacyl complex [TaCp*Cl(O){η2-C(Me)dN(2,6-
Me2C6H3)}] (7).
react with 1 equiv of CO to form the stable enolate
derivatives [TaCp*X{N(2,6-Me2C6H3)}{OC(Me)dCMe2}]
(X ) Cl (9), Me (10)), which probably exhibit the same
pseudotetrahedral structure known for the related
isoelectronic complexes [TaCp*{N(2,6-Me2C6H3)}{N(2,6-
Me2C6H3)CMedCMe2}] previously reported.4b We as-
sume that the coordination of CO is followed by a double
migration of one methyl group and the metallacycle
alkyl group to the electrophilic carbonyl carbon atom,
but when the reactions were followed by 1H NMR
spectroscopy, the proposed intermediate species shown
in Scheme 4 could not be detected. Depending on the
order of migration of both groups, either of the two
different pathways lead to the same unidentified inter-
mediate species that spontaneously rearranges, break-
ing the TasC and CsN(amido) bonds with simulta-
neous CdC double-bond formation, to give the resultant
products 9 and 10.
As shown in Scheme 3, the formation of complex 7
can be explained assuming the initial coordination of
CO, followed by the migration of the methyl group
bonded to the metal to the electrophilic carbonyl carbon
atom to give the barely stable intermediate η2-acyl
complex [TaCp*Cl{N(2,6-Me2C6H3)}{η2-C(Me)dO}] (6).
Formation of complex 6 was checked, monitoring the
1
reaction by NMR spectroscopy. The H NMR and 13C-
{1H} NMR spectra of complex 6 in CDCl3 at -40 °C
show singlets at δ 3.12 and 316.1 ppm, respectively, as
expected for the acyl ligand.9 The nucleophilic attack
of the imido nitrogen atom at the electrophilic acyl
carbon atom leads to an unidentified intermediate
species which spontaneously rearranges, breaking the
CsO bond with simultaneous formation of MsC and
the MdO double bonds to give the final η2-iminoacyl
oxo complex 7.
All of the complexes 4-10 are soluble in aromatic
hydrocarbons and chlorinated solvents and only slightly
soluble in saturated hydrocarbons.
The formulation of complexes 5, 9, and 10 as enolate
derivatives is supported by the IR spectra, which show
ν(CdC),1b,3de,10 ν(CsO),1b and ν(TasO)11 absorptions at
1587-1676, 1198-1180, and 804-816 cm-1, respec-
The analogous reaction of TaCp*Cl2Me2 with CO in
benzene-d6 carried out in an NMR tube leads to the
formation of the corresponding dichloro oxotantalacy-
clopropane complex TaCp*Cl2(η2-CMe2O) (8), as a result
of a double migration of two methyl groups, first to the
electrophilic carbon atom of the coordinated CO and
then to the related η2-acyl intermediate, which could
not be observed. Compound 8, which is not further
transformed, is analogous to the reported1b,3f tantalum
acetone complex TaCp*Me2(η2-CMe2O).
1
tively. The H NMR spectrum of complex 5 shows one
singlet at δ 2.17 ppm for the equivalent methyl substi-
tuents of the bridging enolate ligand, whereas the reso-
nances corresponding to the nonequivalent methyl sub-
stituents of the terminal enolate ligand in complexes 9
(10) (a) Curtis, M. D.; Thanedar, S.; Butler, W. M. Organometallics
1984, 3, 1855. (b) Meyer, T. Y.; Garner, L. R.; Baenzinger, N. C.;
Messerle, L. W. Inorg. Chem. 1990, 29, 4045.
(11) Nakamoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds; Wiley: New York, 1978.
Similarly, the azatantalacyclopropane complexes [Ta-
Cp*XMe(η2-CMe2NR)] (X ) Cl, Me; R ) 2,6-Me2C6H3)4a

3582 Organometallics, Vol. 15, No. 16, 1996
Go´mez et al.
Sch em e 4a
a
Reagents and conditions: (i) sealed NMR tube, CO (1 atm), benzene-d6, room temperature, fast; (ii) X ) Cl, CO (1 atm),
toluene, -78 °C, 2 h, X ) Me, sealed NMR tube, CO (1 atm), benzene-d6, room temperature, 2 h.
and 10 appear as three multiplets due to the existence of
a rigid CdC double bond on the NMR time scale.1b,3de,10,12
The η2-iminoacyl oxo complex 7 shows the ν(CdN)9
tion. The complex is chiral, and two distinct enanti-
omers were found in the crystals.
The η2-iminoacyl group is coordinated in a situation
similar to that found in the previously reported com-
pound [TaCp*(NR)Me{η2-C(CMe2CMedNR)NR}]4b (R )
2,6-Me2C6H3) or in compound 11 in this paper, with Ta-
C(1) and Ta-N(1) distances of 2.133(9) and 2.132(7) Å,
respectively, corresponding to single bonds, and a C(1)-
N(1) distance of 1.276(11) Å, which implies double-bond
character. The Ta-Cp*(centroid) distance is 2.156 Å,
as in the compounds mentioned above.
The Ta-Cl distance is 2.409(3) Å, shorter than the
distances found in [TaCp*Cl3(η2-NRCMe2CNHR)],4b
which ranged from 2.452(1) to 2.526(1) Å, but longer
than those found in [TaCp*Cl2(N-2,6-Me2C6H3)],8b where
the distances are 2.331(2) and 2.326(6) Å. The oxygen
ligand is bonded to the tantalum atom with a distance
of 1.731(7) Å. To the best of our knowledge only two
and ν(TadO)10b,13 IR absorptions at 1628 and 906 cm-1
,
respectively. In addition, two singlets are observed in
the 1H and 13C NMR spectra (see Experimental Section)
for the o-methyl(phenyl) groups of the η2-iminoacyl
ligand, which are nonequivalent due to the rigid struc-
ture of 7 on the NMR time scale.
The molecular structure of 7 with the atom-number-
ing scheme is shown in Figure 1. Selected bond
distances and angles are given in Table 1.
Complex 7 has a monomeric structure with the
tantalum atom coordinated to a pentamethylcyclopen-
tadienyl ring in an almost η5-bonding mode (Ta-C
distances ranged from 2.431(9) to 2.526(8) Å), an η2-
iminoacyl group, one chlorine atom, and one oxygen
atom. When the centroid of the iminoacyl group is
taken as occupying a single site, the tantalum atom can
be considered to be in a three-legged piano-stool situa-
structures with terminal TadO bonds have been re-
14
ported: Ta(O)(NPri )
and TaCp*2(O)H.13b In both
2 2
cases a double bond was proposed with a mean distance
of 1.72 Å, very similar to that found in our case. Single-
bond Ta-O distances are ca. 2.18 Å, whereas mean
(12) (a) Planalp, R. P.; Andersen, R. A. J . Am.Chem. Soc. 1983, 105,
7774. (b) Arnold, J .; Tilley, T. D.; Rheingold, A. L.; Geib, S. J .; Arif, A.
M. J . Am. Chem. Soc. 1989, 111, 149. (c) Veya, P.; Floriani, C.; Chiesi-
Villa, A.; Guastini, C. Organometallics 1994, 13, 208.
(13) (a) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
Wiley: New York, 1988. (b) Parkin, G.; Van Asselt, A.; Leahy, D. J .;
Whinnery, L.-R.; Hua, N. G.; Quan, R. W.; Henling, L. M.; Schaefer,
W. P.; Santarsiero, B. D.; Bercaw, J . E. Inorg. Chem. 1992, 31, 82.
(14) Bradley, D. C. Private communication (cited in: Nugent, W.
A.; Mayer, J . M. Metal-Ligand Multiple Bonds; Wiley: New York, 1988;
p 163).

Insertion of CO and CNR into Ta-Me Bonds
Organometallics, Vol. 15, No. 16, 1996 3583
Ta ble 1. Bon d Len gth s (Å) a n d An gles (d eg) for 7
Ta(1)-O(1)
Ta(1)-Cl(1)
Ta(1)-C(14)
N(1)-C(1)
C(11)-C(15)
C(12)-C(13)
C(13)-C(18)
C(15)-C(20)
C(22)-C(23)
C(24)-C(25)
Ta(1)-Cp*(1)a
1.731(7)
2.409(3)
2.440(9)
1.276(11)
1.402(13)
1.411(14)
1.487(14)
1.479(14)
1.39(2)
Ta(1)-N(1)
Ta(1)-C(11)
Ta(1)-C(13)
N(1)-C(21)
C(11)-C(12)
C(12)-C(17)
C(14)-C(15)
C(21)-C(26)
C(22)-C(27)
C(25)-C(26)
2.132(7)
2.431(9)
2.522(8)
1.435(11)
1.426(14)
1.499(13)
1.43(2)
1.387(14)
1.49(2)
1.39(2)
Ta(1)-C(1)
Ta(1)-C(15)
Ta(1)-C(12)
C(1)-C(2)
C(11)-C(16)
C(13)-C(14)
C(14)-C(19)
C(21)-C(22)
C(23)-C(24)
C(26)-C(28)
2.133(9)
2.434(8)
2.526(8)
1.471(14)
1.496(14)
1.428(14)
1.496(14)
1.392(13)
1.36(2)
1.35(2)
2.156
1.496(14)
O(1)-Ta(1)-N(1)
O(1)-Ta(1)-Cl(1)
C(1)-N(1)-C(21)
N(1)-C(1)-C(2)
Cp*(1)-Ta(1)-Cl(1)
Cp*(1)-Ta(1)-C(1)
107.2(3)
101.4(3)
131.4(8)
127.5(9)
108.8
O(1)-Ta(1)-C(1)
N(1)-Ta(1)-Cl(1)
C(1)-N(1)-Ta(1)
N(1)-C(1)-Ta(1)
Cp*(1)-Ta(1)-N(1)
99.5(4)
85.5(2)
72.6(5)
72.6(5)
129.2
N(1)-Ta(1)-C(1)
C(1)-Ta(1)-Cl(1)
C(21)-N(1)-Ta(1)
C(2)-C(1)-Ta(1)
Cp*(1)-Ta(1)-O(1)
34.8(3)
120.3(3)
155.4(6)
159.7(8)
116.4
110.2
a
Cp* is the centroid of the η5-C5Me5 ring.
Sch em e 5
F igu r e 1. ORTEP view of the molecular structure of
TaCp*Cl(O){η2- C(Me)dN(2,6-Me2C6H3)} (7), with the atom-
numbering scheme.
(Me)dCMe2 the methyl group bound to tantalum mi-
grates to the electrophilic carbon atom of the isocyanide
ligand, which does not attack the terminal olefinic
carbon atom of the enolate ligand, in contrast with the
results observed4b when the imido alkenylamido com-
plexes are used.
values between 1.8515 and 1.97 Å have been found for
compounds with terminal Ta-OH bonds and for com-
pounds with various π bond contributions, such as
[TaCp*Me(CPhCPhCCH3O)].16 All these distances in-
dicate a π donor contribution from the ligands, trying
to compensate for the electron deficiency of the 16-
electron metal center.
The X-ray crystal structure of 11 with the atomic
labeling scheme is shown in Figure 2. Selected bond
distances and angles are given in Table 2.
The molecular structure of 11 shows the tantalum
atom bonded to a Cp* ring, one methyl group, one imido
group, and the η2-coordinated iminoacyl system. The
coordination around the metal atom could be considered
in two ways, either with a pseudo-square-pyramidal
geometry where the Cp* centroid is in the apical
position, or with a tetrahedral geometry if we assume
that the Cp* centroid and the center of the η2-iminoacyl
group are occupying single coordination sites. Complex
11 is chiral, and the two different enantiomers were
found in the unit cell.
Rea ction s w ith Isocya n id es. When isocyanides
are added to toluene solutions of the imido complexes
1, 2, or 10 an instantaneous insertion reaction takes
place to give the stable 18-electron imido η2-iminoacyl
derivatives [TaCp*X(NR){η2-C(Me)dNR}] (X ) Me (11),
Cl (12), OC(Me)dCMe2 (13); R ) 2,6-Me2C6H3) (Scheme
5).
When X ) Me the migration of the second methyl
8b
group observed for TaCp*Cl2Me2 does not take place
and the presence of an excess of isocyanide does not
produce a second insertion reaction in the Ta-Me or
Ta-C(iminoacyl) bonds.9,17,18 However, when X ) OC-
(17) (a) Carmona, E.; Mar´ın, J . M.; Palma, P.; Poveda, P. L. J .
Organomet. Chem. 1989, 377, 157. (b) Filippou, A. C.; Gru¨nleitner, W.;
Vo¨lk, C.; Kiprof, P. J . Organomet.Chem. 1991, 413, 181.
(18) Filippou, A. C.; Vo¨lk, C.; Kiprof, P. J . Organomet. Chem. 1991,
415, 375.
(15) Schaefer, W. P.; Quan, R. W.; Bercaw, J . E. Acta Crystallogr.,
Sect. C 1993, 49, 878.
(16) Hirpo, W.; Curtis, M. D. Organometallics 1994, 13, 2706.

3584 Organometallics, Vol. 15, No. 16, 1996
Go´mez et al.
derivatives [TaCp*X{N(2,6-Me2C6H3)}{η2-C(Me)dO}]
but lead to different products, depending on X. Attack
of the imido nitrogen at the more electrophilic acyl
carbon atom when X ) Cl gives the oxo iminoacyl com-
plex [TaCp*Cl(O){η2-C(Me)dN(2,6-Me2C6H3)}], whereas
the higher carbenoid character of the acyl ligand when
X ) Me leads to the dinuclear ene diolate complex
[TaCp*{N(2,6-Me2C6H3)Me}]2{µ-η2-OC(Me)dC(Me)O}.
However, reactions of the related azatantalacyclopro-
pane complexes [TaCp*XMe(η2-CMe2NR)] (X ) Cl, Me)
with CO take place with conversion into the imido
enolate derivatives [TaCp*X(NR){OC(Me)dCMe2}]. In
contrast, the same imidotantalum complexes react with
CN(2,6-Me2C6H3) to give the stable 18-electron imino-
acyl compounds [TaCp*X(NR){η2-C(Me)dNR}] (X ) Cl,
Me) and the analogous product is also obtained when
X ) OC(Me)dCMe2, without any further transforma-
tion.
F igu r e 2. ORTEP view of the molecular structure of
TaCp*Me(NR){η2- C(Me)dNR} (R ) 2,6-Me2C6H3; 11), with
the atom-numbering scheme.
Ta ble 2. Selected Bon d Len gth s (Å) a n d
An gles (d eg) for 11
Exp er im en ta l Section
Ta(1)-N(1)
Ta(1)-N(2)
Ta(1)-C(15)
Ta(1)-C(14)
Ta(1)-C(12)
N(2)-C(41)
C(41)-C(42)
1.805(4)
2.162(4)
2.422(5)
2.439(5)
2.494(6)
1.281(7)
1.466(8)
Ta(1)-C(41)
Ta(1)-C(1)
Ta(1)-C(13)
Ta(1)-C(11)
N(1)-C(31)
N(2)-C(43)
Ta(1)-Cp1
2.153(6)
2.226(5)
2.430(5)
2.495(6)
1.376(6)
1.428(7)
2.148
All operations were carried out under a dry argon atmo-
sphere either in a Vacuum Atmosphere Dri-lab or by standard
Schlenk techniques. Hydrocarbon solvents were dried and
freshly distilled: n-hexane from sodium-potassium alloy and
toluene from sodium. Reagent grade CO (SEO), LiMe (1.6 M
in OEt2, Aldrich), HCl (1 M in OEt2, Aldrich), and 2,6-Me2C6H3-
OH (Panreac) were purchased from commercial sources and
were used without further purification. Isocyanides19 RNC (R
) 2,6-Me2C6H3, 2,4,6-Me3C6H2), and the starting materials
TaCp*Cl2Me2,20 TaCp*Cl2-xMex(η2- CMe2-NR) (x ) 0,4a 1,4b 2,4a
R ) 2,6-Me2C6H3), TaCp*{N-(2,6-Me2C6H3)}Cl2,4a and TaCp*-
(NR)Me(η1-NRCMedCMe2) (R ) 2,6-Me2C6H3)4b were prepared
as described previously.
N(1)-Ta(1)-C(41)
C(41)-Ta(1)-N(2)
C(41)-Ta(1)-C(1)
C(31)-N(1)-Ta(1)
C(41)-N(2)-Ta(1)
N(1)-C(31)-C(36)
N(2)-C(41)-C(42)
101.9(2) N(1)-Ta(1)-N(2)
34.5(2) N(1)-Ta(1)-C(1)
115.8(2) N(2)-Ta(1)-C(1)
106.9(2)
99.9(2)
81.4(2)
172.2(4) C(41)-N(2)-C(43) 131.3(5)
72.4(3) C(43)-N(2)-Ta(1) 155.6(4)
119.6(5) N(1)-C(31)-C(32) 121.3(5)
124.9(5) N(2)-C(41)-Ta(1)
73.1(3)
119.5
107.9
C(42)-C(41)-Ta(1) 161.7(5) N(1)-Ta(1)-Cp1
N(2)-Ta(1)-Cp1
129.3
C(1)-Ta(1)-Cp1
Infrared spectra were recorded on a Perkin-Elmer 583
spectrophotometer (4000-200 cm-1) as Nujol mulls between
CsI or polyethylene pellets. 1H and 13C NMR spectra were
recorded on Varian Unity VXR 300 MHz and Varian Unity
FT 500 MHz instruments, and chemical shifts were measured
a
Cp is the centroid of the η5-C5Me5 ring.
The imido group is almost linear, the Ta-N(1)-C(31)
angle being 172.2(4)°, and the Ta-N(1) (1.805(4) Å) and
N(1)-C(31) (1.376(6) Å) distances are very close to those
found in similar systems such as [TaCp*Cl2(NR)] (R )
2,6-iPr2C6H3,7b 2,6-Me2C6H38b) and [TaCp*Me(NR)-
(NRCMedCMe2)]4b (R ) 2,6-Me2C6H3), corresponding
to a Ta-N triple bond. The Ta-C(1) bond distance of
2.226(5) Å is the normal value for a Ta-CH3 bond.
The situation of the η2-iminoacyl system is parallel
to that found in complex 7 with distances Ta-C(41) )
2.153(6) Å, Ta-N(2) ) 2.162(5) Å, and C(41)-N(2) )
1.281(7) Å. The nitrogen atom of the iminoacyl group
is located in a trans position with respect to the imido
group.
The N(1), N(2), C(41), and C(1) atoms are not in a
plane, but the mean plane defined by them is almost
parallel to the Cp* plane, with the N(2) and the
tantalum atoms above this plane at 0.25 and 0.945 Å,
respectively, whereas the C(41) and C(1) atoms are
below this plane by 0.357 and 0.178 Å, respectively.
The Cp* ring is bonded to tantalum in a fairly
symmetric way, and the Ta-C distances ranged from
2.422(5) to 2.495(6) Å.
1
relative to residual H and 13C resonances in the deuterated
solvents C6D6 (δ 7.15), CDCl3 (δ 7.24) and C6D6 (δ 128), CDCl3
(δ 77), respectively. Mass spectra were recorded on an HP
5988 A instrument. C, H, and N analyses were carried out
with a Perkin-Elmer 240C microanalyzer.
[Ta Cp *Me2{N(2,6-Me2C6H3)}] (1). A 1.6 M solution of
LiMe in OEt2 (6.17 mL, 9.88 mmol) was added at -78 °C to a
solution of [TaCp*Cl2{N(2,6-Me2C6H3)}] (2.50 g, 4.94 mmol)
in toluene (60 mL), and the mixture was stirred for 30 min.
The color of the mixture changed quickly from red to green. It
was then warmed to room temperature for 2 h, the solvent
removed in vacuo, and the residue extracted into n-hexane (3
× 20 mL). The solution was concentrated to ca. 25 mL and
cooled to -40 °C to give 1 as green crystals.
Data for 1 are as follows. Yield: 1.6 g (70%). IR (Nujol
mull; ν, cm-1): 1328 (vs), 1154 (m), 1094 (s), 1025 (m), 983
(m), 802 (w), 756 (s), 536 (m), 499 (s), 483 (m), 391 (w), 353
2
(m). 1H NMR (δ, ppm; in benzene-d6): 7.15 (d, 2H, J H-H
)
7.2 Hz, H3C6Me2), 6.80 (t, 1H, 2J H-H ) 7.2 Hz, H3C6Me2), 2.49
(s, 6H, 2,6-Me2C6H3), 1.69 (s, 15H, C5Me5), 0.31 (s, 6H, Ta-
Me2). 13C{1H} NMR (δ, ppm; in benzene-d6): 154.02 s, 133.71
s, 126.84 s, 120.84 s (Ci, Co, Cm, Cp, C6H3Me2), 116.12 (s, C5-
Me5), 47.95 (s, Ta-Me2), 18.90 (s, 2,6-Me2C6H3), 10.88 (s,
Con clu sion
(19) Weber, W. P.; Go¨kel, G. W.; Ugi, I. K. Angew. Chem., Int. Ed.
Engl. 1972, 11, 530.
(20) Go´mez, M.; J ime´nez, G.; Royo, P.; Selas, J . M.; Raithby, P. R.
J . Organomet. Chem. 1992, 439, 147.
Reactions of the imido methyl tantalum(V) complexes
[TaCp*MeX{N(2,6-Me2C6H3)}] (X ) Cl, Me) with CO
take place through the formation of the expected acyl

Insertion of CO and CNR into Ta-Me Bonds
Organometallics, Vol. 15, No. 16, 1996 3585
C5Me5). Anal. Calcd for C20H30NTa: C, 51.60; H, 6.51; N,
3.00. Found:C, 52.00; H, 6.27; N, 2.95.
16 h, and the resulting brown solution was evaporated to
dryness. Recrystallization from n-hexane at -40 °C afforded
5 as brown crystals in 80% yield (1.70 g).
[Ta Cp *ClMe{N(2,6-Me2C6H3)}] (2). A 1 M solution of HCl
in OEt2 (3.92 mL, 3.91 mmol) was added at -78 °C to a
solution of [TaCp*(NR)Me{η1-NRC(Me)dCMe2}] (2.50 g, 3.91
mmol) in toluene (50 mL), and the mixture was stirred for 20
min. The color of the mixture changed slowly from yellow to
reddish. It was then warmed to room temperature for 2 h,
the solvent removed in vacuo, and the resulting residue
extracted into n-hexane (3 × 20 mL). The solution was
filtered, concentrated to ca. 15 mL, and cooled to -40°C to
give 2 as orange crystals.
Data for 5 are as follows. IR (Nujol mull; ν, cm-1): 1587
1
(w), 1331 (s), 1198 (m), 1026 (w), 804 (m), 495 (d), 352 (d). H
NMR (δ, ppm; in benzene-d6): 6.93 (m, 3H, H3C6Me2), 2.42
(s, 6H, 2,6-Me2C6H3), 2.17 [s, 6H, OC(Me)dC(Me)O], 1.78 (s,
15H, C5Me5), 0.78 (s, 3H, Ta-Me). 13C{1H} NMR (δ, ppm; in
benzene-d6): 154.3 [s, OC(Me)dC(Me)O], 142.1 s, 132.7 s,
126.8 s, 121.1 s (Ci, Co, Cm, Cp, C6H3Me2), 116.4 (s, C5Me5),
28.8 [s, OC(Me)dC(Me)O], 19.3 (s, 2,6-Me2C6H3), 17.7 (s, Ta-
Me), 10.7 (s, C5Me5). Anal. Calcd for C42H60N2O2Ta2: C,
51.11; H, 6.13; N, 2.84. Found: C, 50.80; H, 5.90; N, 2.70.
[Ta Cp *Cl(O){η2-C(Me)dNC6H3Me2}] (7). A toluene (25
mL) solution of 2 (1.00 g, 2.06 mmol) was placed into an
ampule under a CO atmosphere (1 atm) and then sealed. The
reaction mixture was stirred for 12 h, and the resulting orange-
yellow solution was cooled to -40 °C overnight to give white
crystals, which were subsequently isolated by filtration,
washed with n-hexane (2 × 10 mL), and identified as 7.
Data for 7 are as follows. Yield: 0.90 g (85%). IR (Nujol
mull; ν, cm-1): 1628 (s), 1023 (m), 906 (s), 352 (w), 317 (w).
1H NMR (δ, ppm; in benzene-d6): 6.85 (m, 3H, H3C6Me2), 2.09
(s, 3H, MeCdNC6H3Me2), 1.99 (s, 15H, C5Me5), 1.97 s, 1.61 s
(6H, 2,6-Me2C6H3). 13C{1H} NMR (δ, ppm; in chloroform-d):
236.8 (s, MeCdNC6H3Me2), 139.6 s, 131.7 s, 128.7 s, 128.6 s,
127.8 s, 127.0 s (several phenyl carbons, C6H3Me2), 117.6 (s,
Data for 2 are as follows. Yield: 1.65 g (87%). IR (Nujol
mull; ν, cm-1): 1325 (vs), 1262 (m), 1095 (s), 1024 (m), 800
(s), 756 (s), 484 (m), 396 (m), 350 (s). 1H NMR (δ, ppm; in
3
benzene-d6): 7.04 (d, 2H, J H-H ) 7.2 Hz, H3C6Me2), 6.93 (t,
1H, 3J H-H ) 7.2 Hz, H3C6Me2), 2.45 (s, 6H, 2,6-Me2C6H3), 1.73
(s, 15H, C5Me5), 0.84 (s, 3H, Ta-Me). 13C NMR (δ, ppm; in
benzene-d6): 152.7 (m, Ci, C6H3Me2), 133.8 (m, Co, C6H3Me2),
127.0 (dm, Cm, 1J C-H ) 160.2 Hz, C6H3Me2), 122.5 (d, Cp, 1J C-H
) 159.7 Hz, C6H3Me2), 117.7 (m, C5Me5), 42.2 (q, 1J C-H ) 121.3
1
3
Hz, Ta-Me), 18.8 (qd, J C-H ) 126.4 Hz, J C-H ) 5.0 Hz, 2,6-
1
Me2C6H3), 10.6 (q, J C-H ) 127.7 Hz, C5Me5). Anal. Calcd
for C19H27ClNTa: C, 46.96; H, 5.61; N, 2.88. Found: C, 46.71;
H, 5.37; N, 2.75.
[Ta Cp *(OC6H3Me2)Me{N(2,6-Me2C6H3)}] (3). In a sealed
NMR tube, [TaCp*Me{N(2,6-Me2C6H3)}{η1-N(2,6-Me2C6H3)C-
(Me)dCMe2}] (0.11 g, 0.17 mmol) was treated with 2,6-
Me2C6H3OH (0.02 g, 0.17 mmol) in benzene-d6 (0.6 mL) at 60
°C for 3 days. The reaction was monitored by 1H NMR
spectroscopy until quantitative conversion of the imido alk-
enylamido complex into 3 with simultaneous appearance of
the imine RNdCMeCHMe2 was observed.
C5Me5), 20.8 (s, MeCdNC6H3Me2), 18.2 s, 17.9
s (2,6-
Me2C6H3), 11.1 (s, C5Me5). MS (EI, 70 eV): m/e 513 ([M+], 1),
498 (0.4), 367 (1.8), 363 (1.0), 351 (0.6), 146 (100). Anal. Calcd
for C20H27NOClTa: C, 46.75; H, 5.30; N, 2.73. Found: C,
46.52; H, 5.25; N, 2.63.
[Ta Cp *Cl2(η2-CMe2O)] (8). A C6D6 (0.6 mL) solution of
TaCp*Cl2Me2 (0.08 g, 0.19 mmol) was placed in a NMR tube
under a CO atmosphere (1 atm), and then the tube was sealed.
The color of the mixture changed quickly from green to orange,
and the reaction was monitored by 1H NMR spectroscopy until
TaCp*Cl2Me2 was totally transformed into the η2-acetone
complex 8.
Data for 3 are as follows. 1H NMR (δ, ppm; in chloroform-
d): 7.95 (d, 2H, 3J H-H ) 7.5 Hz, H3C6OMe2), 7.00 (d, 2H, 3J H-H
3
) 7.2 Hz, H3C6Me2), 6.67 (t, 1H, J H-H ) 7.2 Hz, H3C6Me2),
3
6.54 (t, 1H, J H-H ) 7.5 Hz, H3C6OMe2), 2.27 (s, 6H, 2,6-
Me2C6H3), 2.18 (s, 6H, 2,6-Me2C6H3O), 2.02 (s, 15H, C5Me5),
0.87 (s, 3H, Ta-Me). 13C NMR (δ, ppm; in chloroform-d):
159.5 (m, Ci, C6H3OMe2), 153.6 (m, Ci, C6H3Me2), 132.7 (m,
Data for 8 are as follows. 1H NMR (δ ppm, in benzene-d6):
1.95 (s, 6H, CMe2O), 1.68 (s, 15H, C5Me5).
1
Co, C6H3Me2), 128.2 (dm, Cm, J C-H ) 156.1 Hz, C6H3OMe2),
126.7 (dm, Cm, 1J C-H ) 155.6 Hz, C6H3Me2), 126.0 (m, Co, C6H3-
[Ta Cp *Cl{N(2,6-Me2C6H 3)}{OC(Me)dCMe2}], 9. [Ta-
Cp*ClMe{η2-CMe2N(2,6-Me2C6H3)}] (0.08 g, 0.15 mmol) and
C6D6 (0.6 mL) were placed in a NMR tube under a CO
atmosphere (1 atm), and then the tube was sealed. The
reaction was instantaneous, and the formation of 9 in quan-
titative yield was confirmed by NMR.
1
OMe2), 120.4 (d, Cp, J C-H ) 157.5 Hz, C6H3OMe2), 120.3 (d,
1
Cp, J C-H ) 160.7 Hz, C6H3Me2), 116.8 (m, C5Me5), 32.0 (q,
1
3
1J C-H ) 121.8 Hz, Ta-Me), 19.4 (qd, J C-H ) 125.8 Hz, J C-H
1
3
) 5.5 Hz, 2,6-Me2C6H3), 17.7 (qd, J C-H ) 126.3 Hz, J C-H
5.5 Hz, 2,6-Me2C6H3O), 10.9 (q, J C-H ) 127.2 Hz, C5Me5).
)
1
[Ta Cp *X(NR){η2-C(Me)dO}] (R ) 2,6-Me2C6H3; X ) Me
(4), Cl, (6)). In a typical experiment, a CDCl3 solution of 1 or
2 (1.07 mmol) was placed into an NMR tube, the argon
atmosphere replaced by CO, and the tube sealed. The reaction
was monitored by NMR spectroscopy at -50°C until no further
change was observed. Formation of the corresponding η2-acyl
complexes 4 and 6 was confirmed by their 1H and 13C NMR
spectra.
Data for 4 are as follows. 1H NMR (δ, ppm; in chloroform-
d, -50 °C): 6.76 (m, 3H, H3C6Me2), 3.13 (s, 3H, Me-CO), 2.24
(s, 6H, 2,6-Me2C6H3), 1.95 (s, 15H, C5Me5), 0.59 (s, Ta-Me).
13C{1H} NMR (δ, ppm; in CDCl3, -50 °C): 320.4 (s, OC-Me),
153.5 s, 131.4 s, 126.4 s, 119.8 s (Ci, Co, Cm, Cp, C6H3Me2), 113.3
(s, C5Me5), 30.5 (s, Me-CO), 23.3 (s, Ta-Me), 19.1 (s, 2,6-
Me2C6H3), 10.9 (s, C5Me5).
Data for 6 are as follows. 1H NMR (δ, ppm; in chloroform-
d, -40 °C): 6.75 (m, 3H, H3C6Me2), 3.12 (s, 3H, Me-CO), 2.26
(s, 6H, 2,6-Me2C6H3), 2.02 (s, 15H, C5Me5). 13C{1H} NMR (δ,
ppm; in chloroform-d, -40 °C): 316.1 (s, OC-Me), 152.0 s,
131.1 s, 126.4, 121.5 s (Ci, Co, Cm, Cp, C6H3Me2), 116.1 (s, C5-
Me5), 30.4 (s, Me-CO), 19.1 (s, 2,6-Me2C6H3), 11.1 (s, C5Me5).
[{Ta Cp *Me(NR )}2{µ-η2-OC(Me)dC(Me)O}] (R ) 2,6-
Me2C6H3 (5)). A solution of 1 (1.00 g, 2.15 mmol) in toluene
(25 mL) was placed in an ampule under a CO atmosphere (1
atm) and then sealed. The reaction mixture was stirred for
Data for 9 are as follows: IR (Nujol mull; ν, cm-1): 1673
(m), 1337 (vs), 1250 (m), 1180 (vs), 1095 (m), 1025 (m), 980
(w), 951 (m), 817 (s), 760 (s), 342 (s). 1H NMR (δ, ppm; in
chloroform-d): 6.90 (d, 2H, 3J H-H ) 7.5 Hz, H3C6Me2), 6.60 (t,
1H, 3J H-H ) 7.5 Hz, H3C6Me2), 2.26 (s, 6H, 2,6-Me2C6H3), 2.13
(s, 15H, C5Me5), 1.91 [m, 3H, O(Me)CdCMe2], 1.7 m, 1.5 m
[6H, Me2CdC(Me)O]. 13C NMR (δ, ppm; in chloroform-d):
151.8 (m, Ci, C6H3Me2), 149.5 [m, OC(Me)dCMe2], 133.3 (m,
1
Co, C6H3Me2), 126.4 (dm, Cm, J C-H ) 155.7 Hz, C6H3Me2),
1
121.4 (d, Cp, J C-H ) 156.8 Hz, C6H3Me2), 119.3 (m, C5Me5),
107.2 [m, Me2CdC(Me)], 18.8 [m, Me2CdC(Me)O], 18.9 [m,
1
3
Me2CdC(Me)O], 18.2 (qd, J C-H ) 126.3 Hz, J C-H ) 5.3 Hz,
2,6-Me2C6H3), 17.4 [m, O(Me)CdCMe2], 10.8 (q, 1J C-H ) 127.9
Hz, C5Me5).
[TaCp*Me{N(2,6-Me2C6H3)}{OC(Me)dCMe2}], 10. A tolu-
ene (40 mL) solution of [TaCp*Me2{η2-CMe2N(2,6-Me2C6H3)}]
(1.50 g, 2.96 mmol) was placed in a Schlenk tube under a CO
atmosphere (1 atm), and the mixture then was stirred at room
temperature for 2 h. The resulting green solution was
evaporated to dryness and the residue recrystallized from
cold n-hexane (20 mL) to give 10 as a green microcrystalline
solid.
Data for 10 are as follows. Yield: 1.44 g (91%). IR (Nujol
mull; ν, cm-1): 1676 (m), 1335 (vs), 1258 (w), 1179 (vs), 1096
(m), 1026 (m), 985 (w), 947 (m), 816 (s), 758 (s), 494 (m), 353

3586 Organometallics, Vol. 15, No. 16, 1996
Go´mez et al.
Ta ble 3. Cr ysta l a n d Exp er im en ta l Da ta a n d Str u ctu r e Refin em en t P r oced u r es for Com p ou n d s 7 a n d 11
11
7
formula
cryst habit
color
C20H27ClNOTa
prismatic
white
C29H39N2Ta
prismatic
yellow
temp, K
293(2)
293(2)
cryst size, mm
symmetry
unit cell determn
unit cell dimens
a, b, c, Å
â, deg
0.35 × 0.32 × 0.28
0.37 × 0.32 × 0.25
monoclinic, P21/c
monoclinic, P21/c
least-squares fit from 25 rflns
8.913(2), 15.550(3), 14.430(3)
96.74(3)
1986.1(7)
17.476(3), 8.662(2), 18.568(9)
105.51(2)
2708.4
V, Å3
Z
4
4
D
calcd, g cm-3
1.718
1.463
mw
513.83
596.57
F(000)
1008
56.75
ω scans; θmax ) 37°
1200
40.76
ω scans; θmax ) 27°
µ, cm-1
scan mode
no. of rflns
measd
3659
6121
indep
3260 (Rint ) 0.1456)
5824 (Rint ) 0.0580)
no. of data/restraints/params
range of hkl
std rflns
3247/0/217
5810/0/300
0 < h < 10, -18 < k < 0, -16 < l < 16
-22 < h < 0, 0 < k < 11, -23 < l < 23
2 rflns every 120 min, no variation
R indices (I > 2σ(I))
R indices (all data)
max peak in final diff map, e/Å3
min peak in final diff map, e/Å3
goodness of fit on F2
weighting schemea
R1 ) 0.0369, wR2 ) 0.0831
R1 ) 0.0344, wR2 ) 0.0804
R1 ) 0.0785, wR2 ) 0.1325
R1 ) 0.0653, wR2 ) 0.1460
0.725
-0.683
1.297
1.671
-1.776
1.204
w ) 1/[σ2(Fo2) + (0.010P)2 + 12.188P]
w ) 1/[σ2(Fo)2 + (0.040P)2 + 3.663P]
a
2
P ) (Fo + 2Fc2)/3.
3
(m). 1H NMR (δ, ppm; in benzene-d6): 7.09 (d, 2H, J H-H
)
H3C6Me2), 2.67 sbr, 2.25 sbr [6H, 2,6-Me2H3C6NdC(Me)], 1.81
s, 1.79 s (6H, 2,6-Me2H3C6NdTa), 2.06 [s, 3H, MeCdNC6H3-
Me2], 1.90 (s, 15H, C5Me5). 13C{1H} NMR (δ, ppm; in chloro-
form-d): 240.4 [s, C(Me)dNC6H3Me2], 153.0 s, 140.3 s, 129.7
s, 128.5 s, 127.7 s, 126.2 s, 120.3 s (several phenyl carbons,
C6H3Me2), 115.0 (s, C5Me5), 20.7 (s, MeCdNC6H3Me2), 19.1 s,
18.8 s [2,6-Me2H3C6NdC(Me)], 18.4 s, 18.1 s (2,6-Me2H3-
C6NdTa), 20.7 (s, MeCdNC6H3Me2), 11.1 (s, C5Me5). MS (EI,
70 eV): m/e 619 ([M+], 0.3), 582 (0.3), 472 (0.6), 435 (0.6), 146
(100), 105 (48.6). Anal. Calcd for C28H36N2ClTa: C, 54.51;
H, 5.88; N, 4.54. Found: C, 54.70; H, 6.10; N, 4.45.
7.2 Hz, H3C6Me2), 6.75 (t, 1H, 3J H-H ) 7.2 Hz, H3C6Me2), 2.42
(s, 6H, 2,6-Me2C6H3), 1.90 [m, 3H, O(Me)CdCMe2], 1.81 (s,
15H, C5Me5), 1.74 [m, 3H, Me2CdC(Me)O], 1.57 [m, 3H,
Me2CdC(Me)O], 0.84 (s, 3H, Ta-Me). 13C NMR (δ, ppm; in
benzene-d6): 153.9 (m, Ci, C6H3Me2), 149.0 [m, OC(Me)dCMe2],
132.5 (m, Co, C6H3Me2), 126.6 (dm, Cm, 1J C-H ) 152.5 Hz, C6H3-
1
Me2), 120.1 (d, Cp, J C-H ) 157.5 Hz, C6H3Me2), 116.4 (m, C5-
1
Me5), 105.9 [m, Me2CdC(Me)O], 28.8 (q, J C-H ) 120.8 Hz,
Ta-Me), 19.05 [m, Me2CdC(Me)O], 18.99 [m, Me2CdC(Me)O],
1
3
18.90 (qd, J C-H ) 126.6 Hz, J C-H ) 5.5 Hz, 2,6-Me2C6H3),-
1
17.4 [m, O(Me)CdCMe2], 10.8 (q, J C-H ) 127.3 Hz, C5Me5).
Data for 13 are as follows. Yield: 0.60 g (84%). IR (Nujol
mull; ν, cm-1): 1678 (m), 1630 (s), 1332 (s), 1250 (m), 1180
(m), 1026 (m), 982 (w), 817 (s), 760 (s), 480 (w), 340 (s). 1H
NMR (δ, ppm; in benzene-d6): 7.08-6.69 (m, 6H, 2 H3C6Me2),
2.40 [sbr, 6H, 2,6-Me2C6H3NdC(Me)], 2.09 (s, 3H, MeCdNC6H3-
Me2), 1.96 (s, 15H, C5Me5), 1.90 [m, 3H, OC(Me)dCMe2], 1.84
[m, 3H, Me2CdC(Me)O], 1.82 (s, 6H, 2,6-Me2H3C6NdTa), 1.49
[m, 3H, Me2CdC(Me)O]. 13C NMR (δ, ppm; in benzene-d6):
Anal. Calcd for C24H36NOTa: C, 53.82; H, 6.79; N, 2.61.
Found: C, 53.31; H, 2.55; N, 6.67.
[T a C p *X{N (2,6-Me 2C 6H 3)}{η2-C (Me )dN (2,6-Me 2C 6-
H3)}] (X ) Me (11), Cl (12), OC(Me)dCMe2 (13)). A sample
of 1, 2, or 10 (1.07 mmol) was dissolved in 25 mL of toluene in
a Schlenk tube. After the addition of a toluene (10 mL)
solution of CN-2,6-Me2C6H3 (0.14 g, 0.07 mmol), the color of
the mixture changed quickly from brown-green to orange. The
reaction mixture was stirred for 4 h at room temperature and
evaporated to dryness. The oily residue was extracted into
n-hexane (2 × 10 mL) and cooled to -40 °C to give 11-13 as
yellow crystals.
2
247.1 [q, J C-H ) 6.1 Hz, C(Me)dNC6H3Me2], 151.0 [m,
OC(Me)dCMe2], 154.2 m, 142.5 m (Ci, C6H3Me2), 130.5 m,
1
129.6 m (Co, C6H3Me2), 128.5 dm, 127.9 dm (Cm, J C-H ) 158
1
Hz, C6H3Me2), 126.0 d, 120.4 d (Cp, J C-H ) 158.5 Hz, C6H3-
Me2), 115.2 (m, C5Me5), 100.4 [m, Me2CdC(Me)O], 21.13 (q,
1J C-H ) 127.9 Hz, MeCdNC6H3Me2), 19.86 [m, Me2CdC-
(Me)O], 19.84 [m, OC(Me)dCMe2], 19.42 [br, 2,6-Me2C6H3NdC-
(Me)], 18.98 [m, Me2CdC(Me)O], 18.7 (qd,1J C-H ) 126.6 Hz,
Data for 11 are as follows. Yield 0.54 g (85%). IR (Nujol
mull; ν, cm-1): 1620 (s), 1333 (s), 980 (w), 480 (w), 354 (w). 1H
NMR (δ, ppm; in benzene-d6): 6.85 (m, 6H, 2 H3C6Me2), 2.40
[sbr, 6H, 2,6-Me2H3C6NdC(Me)], 2.11 (s, 3H, MeCdNC6H3-
Me2), 1.89 (s, 15H, C5Me5), 1.79 s, 1.64 s (6H, 2,6- Me2H3-
C6NdTa), 0.61 (s, 3H, Ta-Me). 13C{1H} NMR (δ, ppm; in chlo-
roform-d): 241.6 [s, C(Me)dNC6H3Me2], 154.7 s, 141.3 s, 130.6
s, 128.4 s, 126.4 s, 125.7 s, 119.2 s (several phenyl carbons,
C6H3Me2), 112.7 (s, C5Me5), 20.3 (s, MeCdNC6H3Me2), 19.1
[s, 2,6-Me2H3C6NdC(Me)], 18.3 s, 18.0 s (2,6-Me2H3C6NdTa),
17.7 (s, Ta-Me), 10.9 (s, C5Me5). MS (EI, 70 eV): m/e 596
([M+], 12.30), 581 (12.9), 435 (14.2), 146 (77.8), 105 (100). Anal.
Calcd for C29H39N2Ta: C, 58.38; H, 6.59; N, 4.70. Found: C,
57.80; H, 6.50; N, 4.60.
1
3J C-H ) 4.6 Hz, 2,6-Me2H3C6NdTa), 18.09 (qd, J C-H ) 127.1
Hz, 3J C-H ) 4.9 Hz, 2,6-Me2H3C6NdTa), 11.1 (q, 1J C-H ) 126.8
Hz, C5Me5). Anal. Calcd for C33H45N2OTa: C, 59.45; H, 6.80;
N, 4.20. Found: C, 59.54; H, 6.85; N, 4.12.
Cr ysta l Str u ctu r e Deter m in a tion of Com p ou n d s 7 a n d
11. Crystallographic and experimental details of the crystal
structure determinations are given in Table 3. Suitable
crystals of complexes 7 and 11 were mounted on an Enraf-
Nonius CAD 4 automatic four-circle diffractometer with bisect-
ing geometry, equipped with a graphite-oriented monochro-
mator and Mo KR radiation (λ ) 0.710 73 Å). Data were
collected at room temperature. Intensities were corrected for
Lorentz and polarization effects in the usual manner. No
absorption or extinction corrections were made.
Data for 12 are as follows. Yield: 0.83 g (86%). IR (Nujol
mull; ν, cm-1): 1626 (s), 1328 (s), 976 (w), 485 (w), 358 (w),
306 (m). 1H NMR (δ, ppm; in benzene-d6): 6.80 (m, 6H, 2

Insertion of CO and CNR into Ta-Me Bonds
Organometallics, Vol. 15, No. 16, 1996 3587
The structures were solved by direct methods (SHELXS
90)21 and refined by full-matrix least-squares against F2
(SHELXL 93).22 All non-hydrogen atoms were refined aniso-
tropically. In the last cycle of refinement the hydrogen atoms
were positioned geometrically and refined using a riding model
with fixed thermal parameters (U ) 0.08 Å2).
Ack n ow led gm en t. We thank the DGICYT (Grant
PB92-0178-C) for financial support.
Su p p or tin g In for m a tion Ava ila ble: Hydrogen atom
coordinates (Tables S1-7 and S1-11), anisotropic displacement
parameters (Tables S2-7 and S2-11), complete bond distances
and angles (Tables S3-7 and S3-11), and final atomic coordi-
nates and equivalent isotropic thermal parameters for non-
hydrogen atoms (Tables S5-7 and S5-11) for complexes 7 and
11 (9 pages). Ordering information is given on any current
masthead page.
Calculations were carried on an ALPHA AXP (Digital)
workstation.
(21) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(22) Sheldrick, G. M. SHELXL 93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.
OM9602015