Synthesis of molybdenum and tantalum complexes that contain diamido/donor ligands of the type [(3,5-Cl2C6H3NCH2 CH2)2NMe]2- or [(3,5-Cl2C6H3NCH<s

Article abstract of DOI:10.1021/om0106985

The palladium-catalyzed reaction between diethylenetriamine and 2 equiv of 3,5-dichlorobromobenzene gave (3,5-Cl₂C₆H₃NHCH₂ CH₂)₂NH. Methylation of the central nitrogen with methyl iodide ga

Full text of DOI:10.1021/om0106985

5682
Organometallics 2001, 20, 5682-5689
Syn th esis of Molybd en u m a n d Ta n ta lu m Com p lexes th a t
Con ta in Dia m id o/Don or Liga n d s of th e Typ e
[(3,5-Cl2C6H3NCH2CH2)2NMe]2- or
[(3,5-Cl2C6H3NCH2)2C(2-C5H4N)(CH3)]2-
J ames P. Araujo, Denyce K. Wicht, Peter J . Bonitatebus, J r., and
Richard R. Schrock*
The Department of Chemistry, Massachusetts Institute of Technology,
77 Massachusetts Avenue, Cambridge, Massachusetts 02139
Received August 2, 2001
The palladium-catalyzed reaction between diethylenetriamine and 2 equiv of 3,5-
dichlorobromobenzene gave (3,5-Cl2C6H3NHCH2CH2)2NH. Methylation of the central nitrogen
with methyl iodide gave (3,5-Cl2C6H3NHCH2CH2)2NMe (H2[ArClNNMe]). The palladium-
catalyzed reaction between (H2NCH2)2C(2-C5H4N)(CH3) and 3,5-dichlorobromobenzene gave
(3,5-Cl2C6H3HNCH2)2C(2-C5H4N)(CH3) (H2[ArClNpy]). Molybdenum compounds that were
prepared include [Et3NH]{[ArClNNMe]MoCl3} (1a ), [ArClNNMe]Mo(CCMe3)(CH2CMe3) (2),
[ArClNNMe]MoCl(CH2R) [R ) CMe3 (4a ) or SiMe3 (4b)], [Et3NH]{[ArClNpy]MoCl3} (5), and
Mo[ArClNpy]2 (6). Tantalum complexes that were prepared include [ArClNNMe]TaMe3 (7)
and [ArClNpy]TaMe3 (8). X-ray studies of 1a , 4a , 6, and 7 are reported.
In tr od u ction
uent is an aryl group such as mesityl, the primary focus
being the stabilization of monoalkyl cations of zirco-
nium and hafnium and polymerization of olefins by
them.9,12,17,18,20 Recently, however, we have begun to
explore the synthesis of diamido/donor complexes of
more electron-rich metals, e.g., molybdenum(IV) and
tungsten(IV). Two reports have appeared that deal with
complexes that contain the [(C6F5NCH2CH2)2NMe]2- or
[(3,4,5-C6F3H2NCH2CH2)2NMe]2- ligands.10,11 These stud-
ies suggested that electron-withdrawing groups on the
amido nitrogens facilitated the synthesis of more electron-
rich diamido/donor complexes. Also, in the process it
became clear that at least ortho fluorides were poten-
tially problematic. The fact that we have not yet been
able to prepare any examples of simple Mo(IV) or W(IV)
complexes that contain the known17,20 mesityl-substi-
tuted ligand [(MesNCH2)2C(CH3)(2-C5H4N)]2- led us to
suspect that the smaller size of second and third metals
in group 6 compared to group 4 combined with their
lower electrophilicity may be the source of the difficulty.
(Molybdenum(IV) triamido/amine complexes that con-
Diamido/donor ligands in which the central donor is
a
nitrogen include [(RNCH2CH2)2NR′]2- 1-12
[(RN-
CH2)2C(2-C5H4N)(CH3)]2- 13-20
and [2,6-(CH2NHR)2C6-
H3N]2- 21-24
In our group we have been interested in
,
,
.
variations of the first two in which the amido substit-
(1) Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B.;
Wainwright, A. P. J . Organomet. Chem. 1995, 501, 333.
(2) Clentsmith, G. K. B.; Bates, V. M. E.; Hitchcock, P. B.; Cloke, F.
G. N. J . Am. Chem. Soc. 1999, 121, 10444.
(3) Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B. J . Chem. Soc., Dalton
Trans. 1995, 25.
(4) Horton, A. D.; de With, J . Chem. Commun. 1996, 1375.
(5) Horton, A. D.; de With, J .; van der Linden, A. J .; van de Weg, H.
Organometallics 1996, 15, 2672.
(6) Horton, A. D.; de With, J . Organometallics 1997, 16, 5424.
(7) Liang, L.-C.; Schrock, R. R.; Davis, W. M. J . Am. Chem. Soc.
1999, 120, 5797.
(8) Schrock, R. R.; Lee, J .; Liang, L.-C.; Davis, W. M. Inorg. Chim.
Acta 1998, 270, 353.
(9) Schrock, R. R.; Casado, A. L.; Goodman, J . T.; Liang, L.-C.;
Bonitatebus, P. J ., J r.; Davis, W. M. Organometallics 2000, 19, 5325.
(10) Cochran, F. V.; Bonitatebus, P. J ., J r.; Schrock, R. R. Organo-
metallics 2000, 19, 2414.
(11) Cochran, F. V.; Schrock, R. R. Organometallics 2001, 20, 2127.
(12) Schrock, R. R.; Bonitatebus, P. J ., J r.; Schrodi, Y. Organome-
tallics 2001, 20, 1056.
(13) Bashall, A.; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mount-
ford, P.; Tro¨sch, D. T. Chem. Commun. 1998, 2555.
(14) Blake, A. J .; Collier, P. E.; Gade, L. H.; McPartlin, M.;
Mountford, P.; Schubart, M.; Scowen, I. J . Chem. Commun. 1997, 1955.
(15) Blake, A. J .; Collier, P. E.; Gade, L. H.; Mountford, P.; Lloyd,
J .; Pugh, S. M.; Schubart, M.; Skinner, M. E. G.; Tro¨sch, D. J . M. Inorg.
Chem. 2001, 40, 870.
tain mesityl substituents also could not be prepared.25,26
)
We felt that the 3,5-dichlorophenyl group would be a
potentially useful alternative to a fluorinated phenyl
group, and since 3,5-dichlorobromobenzene is com-
mercially available, amines that contain the 3,5-dichlo-
(21) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 3154.
(22) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics
1996, 15, 5085.
(23) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1996, 15, 5586.
(24) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1997, 16, 1491.
(16) Friedrich, S.; Schubart, M.; Gade, L. H.; Scowen, I. J .; Edwards,
A. J .; McPartlin, M. Chem. Ber. Rec. 1997, 130, 1751.
(17) Mehrkhodavandi, P.; Bonitatebus, P. J ., J r.; Schrock, R. R. J .
Am. Chem. Soc. 2000, 122, 7841.
(18) Schrodi, Y.; Schrock, R. R.; Bonitatebus, P. J ., J r. Organome-
tallics 2001, 20, 3560.
(19) Gade, L. H.; Mountford, P. Coord. Chem. Rev. 2001, 216-217,
65.
(25) Greco, G. E.; Popa, A. I.; Schrock, R. R. Organometallics 1998,
17, 5591.
(26) Greco, G. E.; Schrock, R. R. Inorg. Chem. 2001, 40, 3850.
(20) Mehrkhodavandi, P.; Schrock, R. R. J . Am. Chem. Soc. 2001,
123, 10746.
10.1021/om0106985 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 11/20/2001

Synthesis of Molybdenum and Tantalum Complexes
Organometallics, Vol. 20, No. 26, 2001 5683
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for [Et3NH]{[Ar ClNNMe]MoCl3} (1a ),
{[Ar ClNNMe]MoCl(CH2-t-Bu ) (4a ), a n d [Ar ClNp y]2Mo (6)
1a
4a
6
empirical formula
fw
C
54H80Cl14Mo2N8O2
C26H36Cl5MoN3O
679.77
C50H34Cl8MoN6
1098.37
1561.44
temp, K
293(2)
293(2
293(2)
wavelength, Å
cryst syst, space group
unit cell dimens
0.71073
triclinic, P1h
0.71073
triclinic, P1h
0.71073
orthorhombic, Pbca
a ) 14.478(4) Å
b ) 16.193(4) Å
c ) 22.068(5) Å
R ) 90°
a ) 9.0361(7) Å
b ) 13.8989(11) Å
c ) 14.0760(11) Å
R ) 90.6080(10)°
â ) 96.7660(10)°
γ ) 104.1260(10)°
1701.0(2)
a ) 8.6227(6) Å
b ) 11.7787(8) Å
c ) 15.6400(11) Å
R ) 77.4370(10)°
â ) 80.5480(10)°
γ ) 79.2080(10)°
1510.32(18)
â ) 90°
γ ) 90°
volume, Å3
5174(2)
Z, calcd density, Mg/m3
abs coeff, mm-1
F(000)
1, 1.524
0.963
798
2, 1.495
0.901
696
4, 1.410
0.706
2216
θ range for data collection
2.60-23.29°
2.44-23.30°
2.10-20.00°
-13 e h e 13, -15 e k e 15,
-12e l e 21
14297/2404 [R(int) ) 0.1294]
99.7%
limiting indices
-10 e h e 9, -15 e k e 10,
-14 e l e 15
-9 e h e 8, -13 e k e 12,
-17 e l e 12
no. of reflns collected/unique
completeness to θ ) 23.29
abs corr
6841/4769 [R(int) ) 0.0357]
97.1%
6113/ 4246 [R(int) ) 0.0503]
97.0%
empirical
none
none
refinement method
full-matrix least-squares on F2
4769/0/361
full-matrix least-squares on F2
4246/0/330
full-matrix least-squares on F2
2404/0/307
no. of data/restraints/params
goodness-of-fit on F2
1.075
1.068
1.240
final R indices [I>2σ(I)]
R indices (all data)
R1 ) 0.0420, wR2 ) 0.0994
R1 ) 0.0496, wR2 ) 0.1028
0.625 and -0.569
R1 ) 0.0343, wR2 ) 0.0891
R1 ) 0.0363, wR2 ) 0.0911
0.748 and -0.586
R1 ) 0.0829, wR2 ) 0.1750
R1 ) 0.1074, wR2 ) 0.1854
0.767 and -0.703
largest diff peak and hole, e Å-3
rophenyl group might be preparable via a palladium-
catalyzed N-C coupling reaction27,28 that we have used
to prepare many other arylated amido ligands. In this
paper we report two new diamines, (3,5-C6Cl2H3NHCH2-
CH2)2NMe and (3,5-C6Cl2H3NHCH2)2C(CH3)(2-C5H4N),
and several molybdenum and two tantalum complexes
that contain the diamido/donor ligands derived from
them.
THF gave purple, crystalline [NBu4]{[ArClNNMe]MoCl3}
(1b) in 86% yield. The H NMR spectrum of 1b in C6D6
showed three broad resonances at 1.46, 1.19, and 0.94
ppm for the tetrabutylammonium cation.
1
Resu lts a n d Discu ssion
Syn th eses of Molybd en u m Sp ecies th a t Con ta in
[(3,5-Cl2C6H3NCH2CH2)2NMe]2-. The palladium-cata-
lyzed reaction between diethylenetriamine and 2 equiv
of 3,5-dichlorobromobenzene yields (3,5-Cl2C6H3NHCH2-
CH2)2NH in 50% isolated yield after recrystallization
from a solution of methylene chloride and pentane at 0
°C. The central nitrogen can be methylated with methyl
iodide in acetonitrile in the presence of potassium
carbonate at room temperature over the course of 16 h
to give (3,5-Cl2C6H3NHCH2CH2)2NMe (H2[ArClNNMe])
as a yellow crystalline solid in 65% yield after recrys-
tallization from a solution of diethyl ether and pentane
at 0 °C. Deprotonation of H2[ArClNNMe] with n-butyl-
lithium in ether gave the dilithiomonoetherate salt
Li2[ArClNNMe]‚Et2O as an orange powder in 59% yield.
The reaction between H2[ArClNNMe] and MoCl4-
(THF)2 in THF in the presence of 2.2 equiv of triethyl-
amine gave paramagnetic [Et3NH]{[ArClNNMe]MoCl3}
(1a ) (eq 1) as a deep purple, crystalline solid in 89%
yield. Resonances for the triethylammonium cation
X-ray quality crystals of 1a were grown from a 1:1
THF/diethyl ether solution at -30 °C. The X-ray crystal
structure (Table 1, Figure 1) shows a near octahedral
molybdenum center with the diamido/amine ligand
coordinated in a fac arrangement. One molecule of THF
is present in the unit cell. Relevant bond distances and
angles can be found in Table 2. The Mo-N(amido) bond
lengths (1.980(3) and 2.013(3) Å) are in the expected
range, and the Mo-N(donor) bond length (2.242(3) Å)
is consistent with a Mo-N dative bond. The Mo-Cl
bonds trans to the amido ligands are lengthened by ∼0.1
Å compared to Mo-Cl(1) as a consequence of strong σ
and π donation from the amido nitrogens. The structure
is essentially the same as that of [Et3NH]{[(C6F5NCH2-
CH2)2NMe]MoCl3}.10
1
could be observed in the H NMR spectrum at 2.31 and
1.97 ppm in CD2Cl2 and 1.40 ppm in C6D6. Salt meta-
thesis of 1a with tetrabutylammonium chloride in
(27) Wolfe, J . P.; Wagaw, S.; Marcoux, J .-F.; Buchwald, S. L. Acc.
Chem. Res. 1998, 31, 805.
(28) Hartwig, J . F. Angew. Chem., Int. Ed. 1998, 37, 2046.
Reaction of 1a with 3 equiv of neopentylmagnesium
chloride resulted in formation of the diamagnetic neo-

5684 Organometallics, Vol. 20, No. 26, 2001
Araujo et al.
2 in C6D6 showed distinct singlet resonances for two
different tert-butyl groups at 1.41 and 0.77 ppm and for
one neopentyl methylene group at 1.58 ppm. The
alkylidyne carbon resonance was found at 309.8 ppm
in the 13C{1H} NMR spectrum in C6D6 (cf. 307.7 ppm
in [(3,4,5-F3C6H2CH2CH2)2NMe]Mo(CCMe3)(CH2CMe3)11).
A reaction analogous to that described in eq 2 was
performed between 1a and 3 equiv of trimethylsilyl-
methylmagnesium chloride (eq 3). The reaction mixture
F igu r e 1. ORTEP drawing of the structure of [Et3NH]-
{[ArClNNMe]MoCl3} (1a ). The triethylammonium cation
has been omitted for clarity.
immediately became deep green after the addition of the
Grignard reagent and gradually turned brown after
being stirred for a period of 90 min at room temperature.
The ether-soluble brown powder, isolated in 78% yield,
was found to be the paramagnetic bis(trimethylsilyl-
methyl)molybdenum complex [ArClNNMe]Mo(CH2SiMe3)2
(3). Two broad resonances at 3.57 and 1.15 ppm in the
1H NMR spectrum in C6D6 were assigned to the two
inequivalent trimethylsilyl groups.
Monoalkyl molybdenum complexes containing the
[ArClNNMe]2- ligand can be synthesized by treating 1a
with dialkyl zinc reagents. Reaction of 1a with either
dineopentyl zinc or bistrimethylsilylmethyl zinc affords
[ArClNNMe]MoCl(CH2CMe3) (4a ) in 38% yield or [ArCl-
NNMe]MoCl(CH2SiMe3) (4b) in 68% yield, respectively
(eq 4). The substantially lower yield of 4a is partly due
Ta ble 2. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Et3NH]{[Ar ClNNMe]MoCl3} (1a )
Bond Lengths
Mo-N(3)
Mo-N(1)
Mo-N(2)
1.980(3)
2.013(3)
2.242(3)
Mo-Cl(1)
Mo-Cl(2)
Mo-Cl(3)
2.3993(11)
2.5206(11)
2.4697(11)
Bond Angles
N(3)-Mo-N(1)
N(3)-Mo-N(2)
N(3)-Mo-Cl(2)
N(3)-Mo-Cl(3)
N(3)-Mo-Cl(1)
N(2)-Mo-Cl(3)
N(2)-Mo-Cl(2)
N(2)-Mo-Cl(1)
101.44(14)
79.35(13)
169.85(10)
91.58(10)
95.80(10)
163.28(10)
91.02(9)
N(2)-Mo-N(1)
N(1)-Mo-Cl(1)
N(1)-Mo-Cl(2)
N(1)-Mo-Cl(3)
Cl(1)-Mo-Cl(2)
Cl(1)-Mo-Cl(3)
Cl(2)-Mo-Cl(3)
79.35(13)
98.17(10)
83.12(10)
163.28(10)
92.48(4)
92.82(4)
82.43(4)
175.44(9)
pentyl/neopentylidyne molybdenum complex [ArClNNMe]-
Mo(CCMe3)(CH2CMe3) (2; eq 2). We propose that this
1
to its higher solubility in ether. The H NMR spectra of
4a have single broad resonances at 3.85 ppm in C6D6
species is formed by loss of molecular hydrogen from
putative [ArClNNMe]Mo(CH2CMe3)2 (R,R-dehydrogen-
ation).29-32 An analogous complex that contains a
[(3,4,5-F3C6H2CH2CH2)2NMe]2- ligand has been crys-
tallographically characterized;11 the neopentylidyne
ligand was found in the axial position trans to the amine
donor. Compound 2 was recrystallized from a 1:1 ether/
pentane solution at -30 °C as yellow-brown crystals in
55% yield. Low yields are due in part to the compound’s
and at 3.62 ppm in CD2Cl2 for the methyl groups of the
1
neopentyl ligand, while the H NMR spectrum of 4b in
C6D6 reveals a single broad resonance at 3.05 ppm for
the methyl groups of the trimethylsilyl group.
X-ray quality crystals of 4a were obtained from a 1:2
mixture of THF and pentane at -30 °C. One molecule
of THF is present in the unit cell. The X-ray crystal
structure of 4a (Table 1, Figure 2) shows the chloride
to be in the apical site trans to the amine donor.
Pertinent bond distances and angles are listed in Table
3. All bond distances are within the expected ranges.
Steric interaction between the neopentyl group and the
aryl rings is likely to be the reason the isomer with the
neopentyl group in the axial position is not observed.
The Mo-C(18)-C(19) angle (129.3°) is normal for a
neopentyl group, as opposed to the large angle that is
observed for the neopentyl group in an axial position in
1
slight solubility in pentane. The H NMR spectrum of
(29) Seidel, S. W.; Schrock, R. R.; Davis, W. M. Organometallics
1998, 17, 1058.
(30) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Shih, K.-Y.;
O’Donoghue, M. B.; Davis, W. M.; Reiff, W. M. J . Am. Chem. Soc. 1997,
119, 11876.
(31) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Dobbs, D.
A.; Shih, K.-Y.; Davis, W. M. Organometallics 1997, 16, 5195.
(32) Shih, K.-Y.; Totland, K.; Seidel, S. W.; Schrock, R. R. J . Am.
Chem. Soc. 1994, 116, 12103.

Synthesis of Molybdenum and Tantalum Complexes
Organometallics, Vol. 20, No. 26, 2001 5685
treatment of 5 with Grignard reagents and dialkyl zinc
reagents in reactions analogous to those involving 1a
have not yet yielded isolable five-coordinate species. We
suspect that the pyridine donor is more labile than the
amine donor in [ArClNNMe]2- complexes and that the
ligand is thereby attacked and possibly removed from
the metal at some point.
In the process of exploring routes to Mo complexes
we turned to reactions involving Li2[ArClNpy], which
was prepared readily by deprotonation of H2[ArClNpy]
with n-butyllithium. The reaction between Li2[ArClNpy]
in THF and MoCl4(THF)2 gave a purple paramagnetic
product, the yield of which we found was optimized by
employing 2 equiv of Li2[ArClNpy] per Mo (eq 7). This
F igu r e 2. ORTEP drawing of the structure of [ArClNNMe]-
MoCl(CH2-t-Bu) (4a ).
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Ar ClNNMe]MoCl(CH2-t-Bu ) (4a )
Bond Lengths
Mo-N(1)
Mo-N(2)
Mo-N(3)
2.236(2)
1.975(3)
1.994(3)
Mo-C(18)
Mo-Cl(1)
2.137(3)
2.3881(8)
Bond Angles
N(2)-Mo-N(3)
N(2)-Mo-N(1)
N(2)-Mo-Cl(1)
129.12(11) N(3)-Mo-N(1)
80.54(10)
167.84(7)
89.67(11)
102.49(8)
80.15(10) N(1)-Mo-Cl(1)
94.71(8)
N(1)-Mo-C(18)
N(2)-Mo-Cl(18) 112.69(12) C(18)-Mo-Cl(1)
N(3)-Mo-C(18)
N(3)-Mo-Cl(1)
113.77(12) Mo-C(18)-C(19) 129.3(2)
94.54(8)
[MesNNMe]Zr(CH2CMe3)2.18 We assume that 4b has a
structure analogous to that of 4a .
Syn th esis of Molybd en u m Com p lexes th a t Con -
t a in t h e [(3,5-Cl2C6H 3NCH 2)2C(2-C5H 4N)(CH 3)]2-
Liga n d . The diamine, H2[(3,5-Cl2C6H3NCH2)2C(2-C5H4-
N)(CH3)], was prepared in 60% yield by treating (H2-
NCH2)2C(2-C5H4N)(CH3) with 2 equiv of 3,5-dichloro-
bromobenzene and 2 equiv of NaO-t-Bu in the presence
of a catalytic amount of Pd(0)/rac-Binap (eq 5). The
complex can be recrystallized readily from a mixture of
THF and pentane at -30 °C. An X-ray study (Table 1)
revealed the complex to be Mo[ArClNpy]2 (6), in which
two ligands are coordinated to one Mo center (Figure
3). The complex has a center of inversion at Mo. The
two Mo-N(amide) bonds are the same within experi-
mental error (Mo-N(1) ) 2.058(9) Å and Mo-N(2) )
2.076(8) Å); the Mo-N(pyridine) bond (Mo-N(3) )
2.147(9) Å) is slightly shorter than the Mo-N(donor)
bond in 1 (Mo-N(2) ) 2.319(4) Å). All angles between
cis ligands are within the range 87(5)-92(3)°.
Syn th esis of Ta n ta lu m Com p lexes. For compari-
son we attempted to prepare simple six-coordinate d0
tantalum trimethyl complexes. The reaction between
Li2[ArClNNMe]‚Et2O and TaCl2Me3 took place smoothly
to give 7 (eq 8) in high yield. All three methyl groups
ligand is obtained as off-white analytically pure crystals
after recrystallization from a mixture of pentane and
ether.
1
The reaction between H2[ArClNpy] and MoCl4(THF)2
followed by addition of triethylamine produced deep
purple paramagnetic [Et3NH]{[ArClNpy]MoCl3} (5; eq
6). This product is only slightly soluble in benzene, but
very soluble in methylene chloride. Two broad reso-
nances were present at 2.77 and 2.16 ppm in the 1H
NMR spectrum in CD2Cl2; they are assigned to the ethyl
groups of the triethylammonium cation. Unfortunately,
coordinated to tantalum are equivalent on the H NMR
time scale at room temperature and appear as a singlet
at 1.14 ppm in C6D6. The aryl rings rotate freely at room
temperature on the basis of the appearance of a sharp
doublet at 6.82 ppm. In the 13C{1H} NMR spectrum the
resonance of the methyl groups on tantalum is seen as
a broad peak at 68.8 ppm in C6D6 at room temperature.
We assume that the fluxional behavior of 7 is the result

5686 Organometallics, Vol. 20, No. 26, 2001
Araujo et al.
Ta ble 4. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for [Ar ClNNMe]Ta Me3 (7)
empirical formula
fw
C20H26Cl4N3Ta
631.19
temp
293(2) K
wavelength
cryst syst
0.71073 Å
monoclinic
space group
unit cell dimens
P21/c
a ) 12.006(3) Å, R ) 90°
b ) 11.415(3) Å, â ) 95.27(3)°
c ) 17.381(6) Å, γ ) 90°
2372.0(12) Å3
volume
Z
4
density(calcd)
abs coeff
1.767 Mg/m3
5.096 mm-1
F(000)
cryst size
θ range for data collection
index ranges
1232
0.24 × 0.40 × 0.70 mm3
2.47-23.28°
-12 e h e 13, -5 e k e 12,
-19 e l e 19
F igu r e 3. ORTEP drawing of the structure of Mo[ArCl
-
no. of reflns collected
no. of ind reflns
completeness to θ ) 23.28°
abs corr
9163
Npy]2 (6). Selected bond lengths (Å) and angles (deg): Mo-
N(1) ) 2.058(9); Mo-N(2) ) 2.076(8); Mo-N(3) ) 2.147(9);
N(1)-Mo-N(2A) ) 87.3(3); N(1)-Mo-N(2) ) 92.7(3);
N(1)-Mo-N(3) ) 92.5(4); N(2)-Mo-N(3A) ) 91.7(3);
N(2)-Mo-N(3) ) 88.3(3); N(1)-Mo-N(3A) ) 87.5(4).
3413 [R(int) ) 0.1044]
99.6%
empirical
max. and min. transmn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
R indices (all data)
extinction coeff
0.9949 and 0.5716
full-matrix least-squares on F2
3413/0/254
1.122
R1 ) 0.0527, wR2 ) 0.1456
R1 ) 0.0540, wR2 ) 0.1469
0.0016(3)
largest diff peak and hole
2.866 and -2.055 e Å-3
Ta ble 5. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Ar ClNNMe]Ta Me3 (7)
Bond Lengths
Ta-N(1)
Ta-N(2)
Ta-N(3)
2.379(7)
2.057(8)
2.005(7)
Ta-C(1)
Ta-C(2)
Ta-C(3)
2.218(10)
2.241(10)
2.214(10)
Bond Angles
N(3)-Ta-N(2)
N(3)-Ta-C(2)
N(3)-Ta-C(3)
N(3)-Ta-N(1)
N(3)-Ta-C(1)
N(2)-Ta-N(1)
N(2)-Ta-C(1)
N(2)-Ta-C(3)
135.6(3)
93.8(4)
113.3(4)
71.2(3)
94.2(4)
73.2(3)
84.6(4)
91.0(4)
N(2)-Ta-C(2)
C(3)-Ta-N(1)
C(2)-Ta-N(1)
C(1)-Ta-N(1)
C(3)-Ta-C(1)
C(3)-Ta(1)-C(2)
C(1)-Ta-C(2)
128.4(3)
88.2(3)
153.8(4)
124.4(4)
143.6(4)
78.0(4)
F igu r e 4. ORTEP drawing of the structure of [ArClNNMe]-
TaMe3 (7).
of an intramolecular rearrangement, although we have
no definitive data that bear on that point.
76.8(4)
become equivalent as a consequence of dissociation of
N(1) from the metal and subsequent rearrangement of
the five-cordinate bisamidotrimethyl species. The me-
ridional geometry found for 7 contrasts with the facial
geometry found for 1a . At this point it is not clear why,
even if one takes into consideration the difference in d
electron count.
A trimethyl tantalum complex, [ArClNpy]TaMe3 (8),
is also formed by the reaction between Li2[ArClNpy]‚
2Et2O and TaCl2Me3 (eq 9). The resonances for the three
X-ray quality crystals of 7 were obtained from a 1:1
toluene/pentane solution at -30 °C over a period of 2
days. The solid-state structure of 7 (Table 4, Figure 4)
shows that the ligand is bound to the metal in a
meridional geometry. Relevant bond distances and
angles are listed in Table 5. The compound is a highly
distorted octahedral species with a relatively long Ta-
N(1) bond (2.379(7) Å). All Ta-C bond lengths are
normal and approximately the same length. The long
Ta-N(1) bond suggests that the three methyl groups
equivalent methyl groups are observed as a singlet at
1.31 ppm in the 1H NMR spectrum in C6D6 and as a
singlet at 72.7 ppm in the 13C{1H} NMR spectrum in
C6D6. We assume that the ligand in 8 must adopt a

Synthesis of Molybdenum and Tantalum Complexes
Organometallics, Vol. 20, No. 26, 2001 5687
mL round-bottom flask with heating. Pd2(dba)3 (0.333 g, 0.364
mmol) was added to the warm solution, and the solution was
stirred for 20-30 min, then filtered to remove Pd(0). The
resulting deep red-orange solution was transferred to a 300
mL Schlenk flask containing diethylenetriamine (5.00 g, 48.5
mmol) and 1-bromo-3,5-dichlorobenzene (21.9 g, 97.0 mmol).
Sodium tert-butoxide (10.8 g, 112 mmol) was added, and the
Schlenk flask sealed and removed from the drybox. The
reaction mixture was opened to a flow of nitrogen, stirred for
36 h at 85 °C, then cooled slightly. The warm mixture was
filtered to remove NaBr and then the toluene removed from
the filtrate. The residue was taken up in diethyl ether (350
mL) and extracted with H2O (300 mL). The water layer was
separated and washed with diethyl ether (2 × 100 mL). The
ether portions were combined and rinsed with water (2 × 100
mL), then dried with MgSO4. The MgSO4 was filtered off and
the filtrate concentrated using the rotary evaporator to leave
a red-brown oil. This oil was dissolved in methylene chloride
(100 mL) and transferred to a 250 mL round-bottom flask.
Pentane (100 mL) was added to the brown solution, and the
flask was stored at 0 °C overnight, over which time a brown
solid formed. Two crops were obtained. Yield: 9.11 g (48%).
1H NMR (CDCl3): δ 6.68 (m, 2, Hp), 6.48 (m, 4, Ho), 4.25 (s, 2,
ArNH), 3.18 (q, 4, ArNHCH2), 2.89 (t, 4, AlkylNHCH2), 1.26
(s, 1, AlkylNH). 1H NMR (C6D6): δ 6.74 (m, 2, Hp), 6.24 (m, 4,
Ho), 3.55 (s, 2, ArNH), 2.41 (q, 4, ArNHCH2), 2.10 (t, 4,
AlkylNHCH2), 0.18 (s, 1, AlkylNH). 13C{1H} NMR (CDCl3): δ
150.1 135.7 117.4 111.2 48.2 43.4. 13C{1H} NMR (C6D6): δ
150.7 136.3 117.6 111.6 48.0 43.2. HRMS (ESI): calcd for
facial geometry as a consequence of its tethered back-
bone structure. (Unfortunately, X-ray quality crystals
could not be obtained.) The [ArClNpy]2- ligand also may
be flexible enough to allow equilibration of the three
methyl groups after dissociation of the pyridine donor.19
Con clu sion s
We conclude that the 3,5-dichlorophenyl group on the
amido nitrogens in two types of diamido/donor ligands
is a viable alternative to fluorinated aryl rings. The
advantages of the 3,5-dichlorophenyl group are that 3,5-
dichlorobromobenzene is not expensive and ligands may
be prepared via C-N coupling reactions. The disadvan-
tage of the 3,5-dichlorophenyl group relative to a
fluorinated group is that there is no ready NMR handle
for following reactions of paramagenetic species. The
potential lability of the donor in each ligand, especially
[(3,5-Cl2C6H3NCH2)2C(2-C5H4N)(CH3)]2-, ultimately may
limit the chemistry that is available for less electrophilic
metal centers.
Exp er im en ta l Section
Gen er a l P r oced u r es. All air-sensitive work was carried
out in a Vacuum Atmospheres drybox under a nitrogen
atmosphere or by standard Schlenk techniques unless other-
wise noted. Diethyl ether, toluene, and pentane were sparged
with nitrogen and passed through a column of activated
alumina. Tetrahydrofuran, benzene, and methylene chloride
were distilled from benzophenone ketyl. C6D6 and CD2Cl2 were
sparged with nitrogen for 10 min. All listed solvents were
stored over 4 Å molecular sieves. MoCl4(THF)2 was synthesized
according to the literature preparation.33 Me3SiCH2MgCl was
obtained from Aldrich and used without further purification.
Triethylamine was obtained from Aldrich and distilled from
calcium hydride. Tetrabutylammonium chloride was obtained
from Aldrich and placed under high vacuum overnight prior
to use. Neopentylmagnesium chloride,34 dineopentyl zinc,35,36
C
16H17N3Cl4 [M + H]+ 392.0255, found [M + H]+ 392.0245.
H2[Ar ClNNMe]. The acetonitrile, diethyl ether, and pentane
used in this reaction were reagent grade and used as obtained
from the supplier. K2CO3 (4.59 g, 33.2 mmol) was added to a
solution of H2[ArClNNH] (3.57 g, 9.08 mmol) in acetonitrile (150
mL). The reaction mixture was purged with N2 for 20 min and
then opened to a flow of nitrogen. Methyl iodide (0.59 mL, 9.54
mmol) was added via syringe in three portions over 60 min,
and the reaction mixture was stirred overnight. Volatile
components were removed in vacuo. The remaining tan residue
was taken up in diethyl ether (200 mL) and extracted with
water (200 mL). The water layer was separated and extracted
with ether (100 mL). The ether portions were combined, rinsed
with water (100 mL), then with saturated NaCl solution (100
mL), and dried with MgSO4. The MgSO4 was filtered off and
ether removed by the rotary evaporator, leaving a thick yellow
oil. The oil was redissolved in diethyl ether (10 mL) and
layered on a plug of silica gel on packed Celite, which was
subsequently eluted with ether (200 mL). The pale yellow
filtrate was concentrated to approximately 5 mL, and pentane
(10 mL) was added. The solution became cloudy with a white
precipitate. Cooling of this mixture to 0 °C overnight gave an
off-white crystalline solid, yield 2.42 g (65%). 1H NMR
(CDCl3): δ 6.68 (m, 2, Hp), 6.43 (m, 4, Ho), 4.26 (s, 2, ArNH),
3.13 (q, 4, ArNHCH2), 2.65 (t, 4, AlkylNMeCH2), 2.30 (s, 3,
(Me3SiCH2)2Zn,36 and TaCl2Me3 were synthesized according
37
to their respective literature preparations. Diethylenetriamine
was obtained from Aldrich and distilled from calcium hydride.
Pd2(dba)3 and rac-BINAP were obtained from Strem and used
without further purification. The diamine starting material,
H3CC(2-C5H4N)(CH2NH2)2, was synthesized according to the
literature preparation.16 1-Bromo-3,5-dichlorobenzene was
obtained from Aldrich and placed under high vacuum over-
night prior to use. n-Butyllithium was obtained from Aldrich
and titrated with 1-propanol and phenanthroline before use.
Silica gel 60, particle size 0.040-0.063 mm (230-400 mesh
ASTM), used for column chromatography was obtained from
EM Science. Elemental analyses were performed by Kolbe
Microanalytical Laboratory (Mu¨lheim an der Ruhr, Germany).
Reported NMR chemical shifts are listed in parts per million
referenced to either the residual protons or carbon-13 atoms
of the deuterated solvents. 1H NMR spectra were obtained on
an instrument operating at 500 MHz, while 13C{1H} NMR
spectra were obtained on an instrument operating at 125 MHz.
All spectra were recorded near 22 °C.
1
AlkylNMe). H NMR (C6D6): δ 6.75 (t, 2, Hp), 6.19 (d, 4, Ho),
3.61 (t, 2, ArNH), 2.39 (q, 4, ArNHCH2), 1.91 (t, 4, Alkyl-
NHCH2), 1.74 (s, 3, AlkylNMe). 13C{1H} NMR (CDCl3): δ 150.0
135.7 117.3 111.2 56.0 42.0 41.0. 13C{1H} NMR (C6D6): δ 150.5
136.4 117.7 111.6 55.7 41.9 40.9. HRMS (ESI): calcd for
C
17H19N3Cl4 [M + H]+ 406.0411, found [M + H]+ 406.0405.
Li2[Ar ClNNMe]‚Et2O. n-Butyllithium (3.16 mL, 1.71 M,
H2[Ar ClNNH]. The Pd catalyst was prepared by dissolving
rac-BINAP (0.453 g, 0.727 mmol) in toluene (50 mL) in a 100
5.40 mmol) was added dropwise to a solution of H2[ArClNNMe]
(1.00 g, 2.46 mmol) in diethyl ether (25 mL) at -30 °C. A
precipitate formed immediately, and the mixture was stirred
for 60 min at room temperature. The solid was filtered off,
rinsed with pentane (50 mL), and dried to yield an orange
powder, yield 710 mg (59%). 1H NMR (C6D6): δ 6.67 (s, 2, Ho),
6.28 (s, 4, Hp), 2.85 (q, 4, Et2O), 2.60 (m, 2, CH2 backbone),
2.52 (m, 2, CH2 backbone), 2.17 (m, 2, CH2 backbone), 1.97
(m, 2, CH2 backbone), 1.69 (s, 3, NMe), 0.66 (t, 6, Et2O). Anal.
(33) Dilworth, J . R.; Richards, R. L.; Chen, G. J .-J .; McDonald, J .
W. Inorg. Synth. 1980, 20, 119.
(34) Schrock, R. R.; Sancho, J .; Pederson, S. F. Inorg. Synth. 1989,
26, 44.
(35) Schrock, R. R.; Fellmann, J . D. J . Am. Chem. Soc. 1978, 100,
3359.
(36) Moorhouse, S.; Wilkinson, G. J . Chem. Soc., Dalton Trans. 1974,
2187.
(37) J uvinall, G. L. J . Am. Chem. Soc. 1964, 86, 4202.

5688 Organometallics, Vol. 20, No. 26, 2001
Araujo et al.
Calcd for C21H27N3Cl4Li2O: C, 51.15; H, 5.52; N, 8.52; Cl, 28.76.
Found: C, 51.24; H, 5.43; N, 8.40; Cl, 28.70.
(C6D6): δ 27.40 (br s), 19.48 (sharp s), 5.83 (br s), 1.46, 1.19,
0.94 (Bu4N), -2.15 (br s), -29.37 (br s), -94.52 (br s), -102.04
(br s). Anal. Calcd for C27H41N4Cl7Mo: C, 46.64; H, 6.29; N,
6.59; Cl, 29.20. Found: C, 46.74; H, 6.36; N, 6.64; Cl, 29.14.
[Ar ClNNMe]Mo(CCMe3)(CH2CMe3) (2). Me3CCH2MgCl
(0.19 mL, 2.43 M, 0.462 mmol) was added dropwise to a
stirring solution of 1a (0.120 g, 0.154 mmol) in THF (5 mL) at
-30 °C. The reaction immediately turned deep green and
gradually became brown while stirring at room temperature
for 30 min. Volatile components were removed in vacuo.
Diethyl ether (5 mL) was added to the brown residue followed
by 1,4-dioxane (0.13 mL, 1.54 mmol). The mixture was stirred
for 10 min and filtered, and the solid was rinsed with ether (3
× 2 mL). The dark yellow-brown filtrate was concentrated to
approximately 1 mL and filtered through glass filter paper.
Pentane (1 mL) was added to the solution, which was then
stored at -30 °C overnight to yield yellow-brown crystals, yield
H2[Ar ClNp y]. The Pd catalyst was prepared by dissolving
rac-BINAP (0.566 g, 0.909 mmol) in toluene (30 mL) in a 100
mL round-bottom flask with heating. Pd2(dba)3 (0.416 g, 0.455
mmol) was added to the warm solution and the solution was
stirred for 20-30 min, then filtered to remove Pd(0). The
resulting deep red-orange solution was transferred to a 300
mL Schlenk flask containing the diamine, H3CC(2-C5H4N)(CH2-
NH2)2 (5.00 g, 30.3 mmol), and 1-bromo-3,5-dichlorobenzene
(14.4 g, 63.6 mmol). Sodium tert-butoxide (6.70 g, 69.7 mmol)
was added, and the Schlenk flask was sealed and removed
from the drybox. The reaction mixture was stirred for 12 h at
85 °C, then cooled slightly. The warm mixture was filtered to
remove NaBr and then the toluene removed from the filtrate.
The residue was taken up in diethyl ether (200 mL) and
extracted with H2O (200 mL). The water layer was washed
with diethyl ether (3 × 100 mL). The ether portions were
combined and dried with MgSO4. The MgSO4 was filtered off
and the filtrate concentrated to approximately 50 mL. Addition
of pentane (50 mL) to the yellow solution followed by cooling
to 0 °C gave an off-white crystalline solid in three crops, yield
1
55 mg (56%). H NMR (C6D6): δ 7.06 (d, 4, Ho), 6.97 (t, 2, Hp),
3.13 (m, 2, backbone CH2), 3.07 (m, 2, backbone CH2), 2.11
(m, 2, backbone CH2), 1.92 (s, 3, NMe), 1.90 (m, 2, backbone
CH2), 1.58 (s, 2, neopentyl CH2), 1.41 (s, 9, CMe3), 0.77 (s, 9,
CMe3). 13C{1H} NMR (C6D6): δ 309.8 166.7 134.7 123.7 123.5
72.8 58.7 55.1 50.9 43.9 35.21 35.15 30.0. Anal. Calcd for
1
6.10 g (44%). H NMR (CDCl3): δ 8.63 (d, 1, Py), 7.71 (m, 1,
Py), 7.36 (d, 1, Py), 7.24 (dd, 1, Py), 6.63 (s, 2, Hp), 6.44 (s, 4,
Ho), 4.63 (t, 2, CH2NHAr), 3.55 (d, 2, CH2NHAr), 3.38 (d, 2,
CH2NHAr), 1.50 (s, 3, CH3). 1H NMR (C6D6): δ 8.30 (d, 1, py),
6.99 (m, 1, py), 6.70 (s, 2, Hp), 6.67 (d, 1, py), 6.59 (m, 1, py),
6.17 (d, 4, Ho), 4.06 (t, 2, CH2NHAr), 3.04 (dd, 2, CH2NHAr),
2.83 (dd, 2, CH2NHAr), 0.95 (s, 3, CH3). 13C{1H} (CDCl3): δ
163.4 150.3 149.2 137.5 135.6 122.4 121.4 117.1 111.3 51.8 45.3
22.8. 13C{1H} (C6D6): δ 163.9 150.8 149.3 137.2 136.2 122.4
121.7 117.6 111.7 51.6 45.6 22.4. Anal. Calcd for C21H19N3Cl4:
C, 55.41; H, 4.21; N, 9.23. Found: C, 55.54; H, 4.30; N 9.30.
Li2[Ar ClNp y]‚2Et2O. n-Butyllithium (2.88 mL, 1.60 M, 4.61
mmol) was added to a solution of H2[ArClNpy] (1.00 g, 2.20
mmol) in diethyl ether (10 mL) at -30 °C and a precipitate
formed. The mixture was stirred at room temperature for 1 h.
The white powder was filtered, rinsed with diethyl ether (3 ×
4 mL), and dried in vacuo, yield 0.757 g (83%). 1H NMR
(C6D6): δ 7.91 (m, 1, Py), 7.19 (m, 1, Py), 6.97 (d, 1, Py), 6.59-
6.56 (m, 3, Py and Hp), 6.33 (br s, 4, Ho), 3.17 (br d, 2, CH2-
NLiAr), 3.11 (q, 8, Et2O), 3.03 (br d, 2, CH2NLiAr), 1.19 (br s,
3, CH3), 0.87 (t, 12, Et2O). Anal. Calcd for C29H37N3Cl4Li2O2:
C, 56.61; H, 6.06; N, 6.83. Found: C, 56.48; H, 6.15; N 6.88.
[Et3NH]{[Ar ClNNMe]MoCl3} (1a ). MoCl4(THF)2 (0.938 g,
2.46 mmol) was added to a stirring solution of H2[ArClNNMe]
(1.00 g, 2.46 mmol) in THF (25 mL). A deep red solution formed
and was stirred for 10 min. NEt3 (0.75 mL, 5.40 mmol) was
added dropwise. The solution became deep purple, and a white
solid formed immediately. The reaction mixture was stirred
for an additional 3 h and filtered. The dark purple solid was
collected (a mixture of the desired product and Et3NHCl) and
rinsed with THF (100 mL). The deep purple THF filtrate was
concentrated to dryness to leave a sparkling purple solid. This
solid was transferred to a frit and rinsed with diethyl ether
(25 mL) to remove unreacted starting material. X-ray quality
crystals were obtained from a 1:1 THF/diethyl ether solution
C27H37N3Cl4Mo: C, 50.56; H, 5.81; N, 6.55; Cl, 22.11. Found:
C, 50.44; H, 5.92; N, 6.50; Cl, 21.98.
[Ar ClNNMe]Mo(CH2SiMe3)2 (3). Me3SiCH2MgCl (1.06 mL,
1.0 M, 1.06 mmol) was added dropwise to a stirring solution
of 1a (0.250 g, 0.320 mmol) in THF (10 mL) at -30 °C. The
reaction immediately turned deep green and gradually became
brown while stirring at room temperature for 90 min. Volatile
components were removed in vacuo. Diethyl ether (5 mL) was
added to the brown residue followed by 1,4-dioxane (0.27 mL,
3.20 mmol). The mixture was stirred for 10 min and filtered,
and the solid was rinsed with ether (3 × 2 mL). The brown
filtrate was concentrated to dryness, and the brown residue
left was triturated with pentane (5 mL) and filtered, yield 170
mg (79%). 1H NMR (C6D6): δ 17.07 (br s), 12.24 (br s), 9.97
(br s), 6.15 (sharp s), 3.57 (br s, SiMe3), 1.15 (br s, SiMe3),
-41.25 (br s), -57.87 (br s). Anal. Calcd for C25H39N3Cl4Si2-
Mo: C, 44.45; H, 5.82; N, 6.22; Cl, 20.99. Found: C, 44.52; H,
5.71; N, 6.21; Cl, 21.14.
[Ar ClNNMe]MoCl(CH2CMe3) (4a ). (Me3CCH2)2Zn (68 mg,
0.282 mmol), diluted with THF (1 mL), was added dropwise
to a stirring solution of 1a (0.100 g, 0.128 mmol) in THF (5
mL) at -30 °C. The solution immediately turned deep green
and was stirred at room temperature for 90 min. Volatile
components were removed in vacuo. The remaining solid was
triturated with ether (5 mL). The mixture was filtered, and
the solid was rinsed with ether (5 mL) and pentane (5 mL)
and dried to yield a green-gray powder. X-ray quality crystals
were obtained from a 1:2 THF/pentane solution at -30 °C over
1
3 days, yield 30 mg (39%). H NMR (CD2Cl2): δ 35.20 (br s),
25.61 (weak br s), 15.64 (br s), 10.66 (br s), 4.73 (sharp s), 3.62
1
(br s, CMe3), -48.38 (br s), -86.63 (br s). H NMR (C6D6): δ
35.83 (br s), 26.69 (weak br s), 15.33 (br s), 10.29 (br s), 4.07
(sharp s), 3.85 (br s, CMe3), -46.64 (br s), -83.91 (br s). Anal.
Calcd for C22H28N3Cl5Mo: C, 43.48; H, 4.64; N, 6.91; Cl, 29.17.
Found: C, 43.58; H, 4.57; N, 7.08; Cl, 29.31.
1
at -30 °C, yield 1.72 g (89%). H NMR (CD2Cl2): δ 26.57 (br
s), 19.42 (sharp s), 8.49 (br s), 2.31, 1.97 (Et3NH), -2.36 (br
s), -29.80 (br s), -96.30 (br s), -110.74 (br s). 1H NMR
(C6D6): δ 26.93 (br s), 19.58 (sharp s), 8.41 (br s), 1.40 (Et3-
NH), -2.94 (br s), -30.03 (br s), -97.75 (br s), -107.02 (br s).
Anal. Calcd for C23H33N4Cl7Mo: C, 38.93; H, 4.69; N, 7.89; Cl,
34.97. Found: C, 39.12; H, 4.78; N, 7.74; Cl, 35.11.
[Bu 4N]{ [Ar ClNNMe]MoCl3} (1b). Solid Bu4NCl (0.136 g,
0.491 mmol) was added to a stirring solution of 1a (0.500 g,
0.705 mmol) in THF (30 mL). The reaction mixture was stirred
overnight and then THF removed in vacuo. The residue was
extracted with benzene (5 mL) and filtered to remove Et3NHCl
and excess Bu4NCl. The benzene was removed to leave a
sparkling dark purple solid, yield 0.520 g (87%). 1H NMR
[Ar ClNNMe]MoCl(CH2SiMe3) (4b). (Me3SiCH2)2Zn (68 mg,
0.282 mmol), diluted in THF (1 mL), was added dropwise to a
stirring solution of 1a (0.100 g, 0.128 mmol) in THF (5 mL) at
-30 °C. The solution immediately turned deep green and was
stirred at room temperature for 90 min. Volatile components
were removed in vacuo. The remaining solid was triturated
with ether (5 mL). The mixture was filtered, and the solid was
rinsed with ether (5 mL) and pentane (5 mL) and dried in
vacuo to yield a green powder, yield 55 mg (69%). 1H NMR
(C6D6): δ 25.30 (br s), 14.05 (br s), 3.55 (sharp s), 3.05 (br s,
SiMe3), -53.78 (br s), -82.78 (br s). Anal. Calcd for C21H28N3-
Cl5SiMo: C, 40.44; H, 4.52; N, 6.74; Cl, 28.42. Found: C, 40.32;
H, 4.46; N, 6.65; Cl, 28.54.

Synthesis of Molybdenum and Tantalum Complexes
Organometallics, Vol. 20, No. 26, 2001 5689
[Et3NH]{[Ar ClNp y]MoCl3} (5). MoCl4(THF)2 (0.419 g, 1.10
mmol) was added to a stirring solution of H2[ArClNpy] (0.500
g, 1.10 mmol) in THF (10 mL). A deep red solution formed
and was stirred for 10 min. NEt3 (0.34 mL, 2.42 mmol) was
added dropwise. The solution became a deep red-purple color,
and a white solid formed immediately. The reaction mixture
was stirred for an additional 3 h and filtered. The dark purple
solid was rinsed with THF (10 mL). The deep purple filtrate
was concentrated to dryness to leave a dark red-purple foam.
This foam was redissolved in THF (5 mL) and added to stirring
chilled (-30 °C) pentane. The resulting purple solid was
collected, rinsed with ether (5 mL) and pentane (10 mL), and
in benzene (10 mL), and the solution was filtered through
Celite to remove LiCl. All solvents were removed from the
yellow filtrate in vacuo to leave a yellow powder. X-ray quality
crystals were grown from a 1:1 toluene/pentane solution, yield
0.195 g (79%). 1H NMR (C6D6): δ 6.90 (t, 2, Hp), 6.82 (d, 4,
Ho), 3.09 (m, 2, arylNCH2), 3.02 (m, 2, arylNCH2), 2.11 (m, 2,
alkylNCH2), 1.90 (s, 3, NMe), 1.75 (m, 2, alkylNCH2), 1.14 (s,
9, TaMe3). 13C{1H} NMR (C6D6): δ 155.7 135.6 123.5 121.3
68.8 56.6 54.8 45.3. Anal. Calcd for C20H26N3Cl4Ta: C, 38.06;
H, 4.15; N, 6.66; Cl, 22.47. Found: C, 38.16; H, 4.07; N, 6.58;
Cl, 22.35.
[Ar ClNp y]Ta Me3 (8). A solution of TaCl2Me3 (0.100 g, 0.337
mmol) in diethyl ether (3 mL) was added dropwise to a slurry
of Li2[(ArCl)2N2py]‚2Et2O (0.205 g, 0.337 mmol) in diethyl ether
(3 mL) at -30 °C. The dark orange mixture was stirred for 30
min at room temperature, then concentrated to dryness. The
resulting residue was taken up in benzene (5 mL), and the
solution was filtered through Celite to remove LiCl. The brown
filtrate was concentrated to dryness. The resulting brown solid
was triturated and rinsed with pentane (10 mL). An orange-
brown powder was collected, yield 0.198 g (87%). 1H NMR
(C6D6): δ 8.23 (m, 1, py), 6.84 (m, py and Hp), 6.72 (d, 4, Ho),
6.63 (d, 1, py), 6.27 (m, 1, py), 3.06 (d, 2, backbone CH2), 3.26
(d, 2, backbone CH2), 1.31 (s, 9, TaMe3), 0.72 (s, 3, Me). 13C-
{1H} NMR (C6D6): δ 160.9 155.2 147.5 138.5 135.5 122.8 122.4
120.8 120.3 72.7 63.9 44.6 23.2. Anal. Calcd for C24H26N3Cl4-
Ta: C, 42.44; H, 3.86; N, 6.19; Cl, 20.88. Found: C, 42.57; H,
3.92; N, 6.11; Cl, 20.78.
1
dried, yield 0.645 g (78%). H NMR (CD2Cl2): δ 92.85 (br s),
33.25 (sharp s), 22.55 (sharp s), 5.19 (sharp s), 2.77, 2.16 (Et3-
NH), -11.75 (strong sharp s), -22.14 (br s), -38.51 (sharp s),
-61.81 (br s). Anal. Calcd for C27H33N4Cl7Mo: C, 42.80; H,
4.39; N, 7.39; Cl, 32.75. Found: C, 42.71; H, 4.47; N, 7.48; Cl,
32.63.
Mo[Ar ClNp y]2. To Li2[ArClNpy]‚2Et2O (963 mg, 1.58 mmol)
in THF (10 mL) was added solid MoCl4(THF)2 (303 mg, 0.793
mmol). The dark brown reaction mixture was stirred at room
temperature for 12 h, and the solution became dark red. The
solvent was removed under vacuum, and the dark residue was
extracted with CH2Cl2 (20 mL) and filtered through a frit with
Celite. The CH2Cl2 was removed under vacuum to give a dark
purple oil. The oil was triturated with a minimum amount of
ether, and the dark purple ether filtrate was pipetted from
the dark residue. The residue was dissolved in THF, and the
solution was filtered. The THF solution was concentrated to
∼5 mL and layered with pentane (∼2 mL). Cooling this
solution to -30 °C overnight gave 257 mg (32%) of dark purple-
red crystalline product. 1H NMR (C6D6): δ 24.5, 21.4 (br), 15.2,
13.3, 4.4, -21.7, -23.7, -28.7, -30.1, -30.8, -34.9. Anal.
Calcd for C42H34Cl8N6Mo: C, 50.33; H, 3.42; N, 8.38; Cl, 28.30.
Found: C, 50.18; H, 3.51; N, 8.26; Cl 28.19.
Ack n ow led gm en t. We thank the National Science
Foundation (CHE-9988766 to R.R.S.) and the National
Institutes of Health (GM-59426) for supporting this
research.
[Ar ClNNMe]Ta Me3 (7). A solution of TaCl2Me3 (0.116 g,
0.391 mmol) in diethyl ether (3 mL) was added dropwise to a
slurry of Li2[ArClNNMe]‚Et2O (0.193 g, 0.391 mmol) in diethyl
ether (5 mL) at -30 °C. The bright yellow mixture was stirred
for 25 min at room temperature, then all solvents were
removed in vacuo. The resulting yellow powder was dissolved
Su ppor tin g In for m ation Available: Fully labeled ORTEP
drawing, atomic coordinates, bond lengths and angles, and
anisotropic displacement parameters for 1a , 4a , 6, and 7 are
available free of charge via the Internet at http://pubs.acs.org.
OM0106985