Molybdenum, tungsten, and rhenium d2 complexes that contain the [(C6F5NCH2CH2)2NMe]2- ligand

Article abstract of DOI:10.1021/om0001117

The reaction between (C₆F₅NHCH₂CH₂)₂NH and methyl iodide in the presence of base leads to (C₆F₅NHCH₂CH₂)₂NMe (H₂[Ar_FNMe]) i

Full text of DOI:10.1021/om0001117

2414
Organometallics 2000, 19, 2414-2416
Molybd en u m , Tu n gsten , a n d Rh en iu m d 2 Com p lexes
Th a t Con ta in th e [(C6F 5NCH2CH2)2NMe]2- Liga n d
Frank V. Cochran, Peter J . Bonitatebus, J r., and Richard R. Schrock*
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue,
Cambridge, Massachusetts 02139
Received February 8, 2000
Summary: The reaction between (C6F5NHCH2CH2)2NH
and methyl iodide in the presence of base leads to (C6F5-
NHCH2CH2)2NMe (H2[ArFNMe]) in good yield. Reac-
tions between H2[ArFNMe] and MCl4 (M ) Mo or W) in
the presence of NEt3 yield pseudooctahedral paramag-
netic compounds of the type [Et3NH]{[ArFNMe]MCl3}.
The reaction between 3 equiv of MeMgCl and [Et3NH]-
{[ArFNMe]MoCl3} produced paramagnetic trigonal bi-
pyramidal [ArFNMe]MoMe2. The reaction between H2[ArF-
NMe] and Mo(NMe2)4 produced paramagnetic seven-
coordinate [(C6F4(NMe2)NCH2CH2)2NMe]MoF2 instead
of five-coordinate [(C6F5NCH2CH2)2NMe]Mo(NMe2)2,
while the reaction between H2[ArFNMe], [NEt4]2[Re(O)-
Cl5], and NEt3 produced diamagnetic trigonal bipyra-
midal [ArFNMe]Re(O)Cl. X-ray studies confirmed the
structures of [Et3NH]{[ArFNMe]MoCl3}, [ArFNMe]MoMe2,
[(C6F4(NMe2)NCH2CH2)2NMe]MoF2, and [ArFNMe]Re-
(O)Cl.
molecular nitrogen.15 Although we are continuing to
prepare new types of triamidoamine ligands, most
recently those that contain various aryl substituents on
the amido nitrogens,16 we have also begun to explore
the synthesis and chemistry of diamidoamine complexes
in the hopes of making the metal center more accessible.
(Complexes that contain planar diamido donor ligands
with a central pyridine donor of the type [C5H3N(CH2-
NAryl)2]2- also have been described.7-9) Interestingly,
in vanadium chemistry involving the [(Me3SiNCH2CH2)2-
NSiMe3]2- ligand, dinitrogen recently has been cleaved
between two vanadium centers to yield a V2(µ-N)2
complex.17 Two examples of structurally characterized
Mo(IV) diamidoamine complexes exist,11 but no general
route to Mo, W, or Re complexes containing such ligands
has been reported. Here we report examples of Mo, W,
and Re complexes that contain the [(C6F5NCH2CH2)2-
NMe]2- ([ArFNMe]2-) ligand.
The reaction between diethylenetriamine and C6F6 in
the presence of K2CO3 has been reported to yield (C6F5-
NHCH2CH2)2NH.18 The fact that the central nitrogen
can be deprotonated to produce a planar trianionic
ligand18 is a potential complication that we would like
to avoid. We have found that the central nitrogen can
be methylated with methyl iodide in CH3CN (eq 1).19
Pure H2[ArFNMe] can be readily made by this route in
good yield on a 6-7 g scale.
We have been interested in complexes that contain
triamidoamine ligands, [(RNCH2CH2)3N]3- (R ) SiMe3
or C6F5), in part because of their ability to define and
sterically protect a trigonal coordination pocket.1-6
Triamidoamine ligands have also allowed us to explore
relatively rare middle oxidation states (2+, 3+, 4+) of Mo
and W, particularly with regard to dinitrogen activation
and reduction.10-13 Related trigonal planar14 molybde-
num complexes that contain monodentate amido ligands
have recently displayed dramatic success in terms of
cleaving strong multiple bonds, in particular that of
1.3 CH3I, K2CO3
(C6F5NHCH2CH2)2NH
8
CH3CN, 15 h
(C6F5NHCH2CH2)2NMe (1)
H2[ArFNMe]
(1) 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.
(2) Mo¨sch-Zanetti, N. C.; Schrock, R. R.; Davis, W. M.; Wanninger,
K.; Seidel, S. W.; O’Donoghue, M. B. J . Am. Chem. Soc. 1997, 119,
11037.
(3) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Dobbs, D.
A.; Shih, K.-Y.; Davis, W. M. Organometallics 1997, 16, 5195.
(4) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9.
(5) Seidel, S. W.; Schrock, R. R.; Davis, W. M. Organometallics 1998,
17, 1058.
(6) Shih, K.-Y.; Totland, K.; Seidel, S. W.; Schrock, R. R. J . Am.
Chem. Soc. 1994, 116, 12103.
(7) Ziniuk, Z.; Goldberg, I.; Kol, M. Inorg. Chem. Commun. 1999, 2,
549.
The reaction between MoCl4(THF)2, H2[ArFNMe], and
NEt3 in THF gave a paramagnetic, burgundy red
powder (eq 2).20 The 19F NMR spectrum of this product
H2[ArFNMe] + MoCl4(THF)2 2.2 NEt , THF8
3
22 °C, 2 h
[Et3NH]{[ArFNMe]MoCl3} (2)
(8) Guerin, F.; McConville, D. H.; Vittal, J . J .; Yap, G. A. P.
Organometallics 1998, 17, 5172-5177.
in THF displayed five resonances at -95.5, -119.3,
-131.3, -135.0, and -169.3 ppm, consistent with
(9) Guerin, F.; Del Vecchio, G.; McConville, D. H. Polyhedron 1998,
17, 917-923.
(10) O’Donoghue, M. B.; Zanetti, N. C.; Schrock, R. R.; Davis, W.
M. J . Am. Chem. Soc. 1997, 119, 2753.
(11) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R. Inorg. Chem.
1998, 37, 5149.
(12) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R.; Reiff, W. M.
Inorg. Chem. 1999, 38, 243.
(13) Kol, M.; Schrock, R. R.; Kempe, R.; Davis, W. M. J . Am. Chem.
Soc. 1994, 116, 4382.
(15) Peters, J . C.; Cherry, J . P. F.; Thomas, J . C.; Baraldo, L.;
Mindiola, D. J .; Davis, W. M.; Cummins, C. C. J . Am. Chem. Soc. 1999,
121, 10053.
(16) Greco, G. E.; Popa, A. I.; Schrock, R. R. Organometallics 1998,
17, 5591.
(17) Clentsmith, G. K. B.; Bates, V. M. E.; Hitchcock, P. B.; Cloke,
F. G. N. J . Am. Chem. Soc. 1999, 121, 10444.
(18) Schrock, R. R.; Lee, J .; Liang, L.-C.; Davis, W. M. Inorg. Chim.
Acta 1998, 270, 353.
(14) Cummins, C. C. Prog. Inorg. Chem. 1998, 47, 685.
10.1021/om0001117 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/24/2000

Communications
Organometallics, Vol. 19, No. 13, 2000 2415
F igu r e 2. ORTEP drawing (30% probability) of the
structure of [(C6F5NCH2CH2)2NMe]MoMe2 (bond lengths
in Å, angles in deg): Mo-N(1) ) 1.970(4), Mo-N(2) )
1.957(4), Mo-N(3) ) 2.325(4), Mo-Cl(1) ) 2.269(4), Mo-
C(2) ) 2.134(6), N(2)-Mo-N(1) ) 123.3(2), N(2)-Mo-C(2)
) 114.9(2), N(2)-Mo-C(1) ) 96.4(2), N(3)-Mo-C(1) )
171.4(2). N(3)-Mo-C(2) ) 96.7(2), N(3)-Mo-N(2) ) 78.7-
(2). [C19H17F10MoN3, monoclinic, P21/n, Z ) 2, a ) 11.7234-
(4) Å, b ) 12.0802(4) Å, c ) 16.2635(5) Å, â ) 110.599(1)°,
R1 ) 0.0496, wR2 ) 0.1127.]
F igu r e 1. ORTEP drawing (30% probability) of the
structure of the anion in [HNEt3]{[(C6F5NCH2CH2)2NMe]-
MoCl3} (bond lengths in Å, angles in deg): Mo-N(1) )
1.991(8), Mo-N(2) ) 2.216(8), Mo-N(3) ) 2.019(9), Mo-
Cl(1) ) 2.410(3), Mo-Cl(2) ) 2.480(3), N(1)-Mo-N(3) )
102.9(3), N(1)-Mo-N(2) ) 77.9(3), N(1)-Mo-Cl(1) ) 94.6-
(2), N(2)-Mo-Cl(1) ) 171.5(2), N(1)-Mo-Cl(3) ) 167.8-
(2). [C23H27Cl3F10MoN4, monoclinic, P21/c, Z ) 4, a )
11.811(3) Å, b ) 17.123(4) Å, c ) 17.325(4) Å, â ) 95.233-
(4)°, T ) 180(2) K, R1 ) 0.0807, wR2 ) 0.1833 (all data).]
trigonal bipyramidal with “equatorial” L-M-L angles
of 123.3°, 114.9°, and 118.8°. The Mo-Namido and Mo-
Namine bond lengths are normal. Addition of 2,6-luti-
dinium chloride to [ArFNMe]MoMe2 in diethyl ether
yielded a paramagnetic blue-green product that we
formulate as [ArFNMe]MoMeCl on the basis of elemen-
tal analysis (C, H, N, Cl).
equivalent, but not rapidly rotating pentafluorophenyl
rings. A single-crystal X-ray study revealed the product
to be [Et3NH]{[ArFNMe]MoCl3} (Figure 1). (X-ray data
were collected on a Bruker CCD diffractometer with Mo
KR ) 0.71073 Å and solved using a full-matrix least-
squares refinement on F2.) The coordination geometry
is approximately octahedral, with the [ArFNMe]2- ligand
arranged in a fac manner (N(1)-Mo-N(3) ) 102.9(3)°).
The Mo-N(1) and Mo-N(3) bond lengths are those
expected for metal-amido bonds, and the Mo-N(2)
bond length is that expected for a dative interaction
between the amine donor and the metal. A toluene-
soluble tetrabutylammonium salt was prepared in
quantitative yield by treating [Et3NH]{[ArFNMe]MoCl3}
with [Bu4N]Cl in THF.
A reaction similar to that shown in eq 2 between
WCl4(dme), H2[ArFNMe], and NEt3 in diethyl ether gave
[Et3NH]{[ArFNMe]WCl3} in 60% yield. An X-ray study
(to be reported later) showed the structure to be
analogous to that of [Et3NH]{[ArFNMe]MoCl3}. A tet-
rabutylammonium salt could be prepared in the same
manner as noted above for [Bu4N]{[ArFNMe]MoCl3}.
The reaction between H2[ArFNMe] and Mo(NMe2)4
(toluene, 22 °C, 12 h) gave a paramagnetic green product
in relatively low isolated yield (23%) that had only four
approximately equally intense resonances in the 19F
NMR spectrum (in THF) at -70.8, -122.3, -124.9, and
-145.2 ppm. An X-ray study showed this product to be
one in which an ortho fluorine on each ring was replaced
with a dimethylamido group. This transformation led
to the product being seven-coordinate [(C6F4(NMe2)NCH2-
CH2)2NMe]MoF2 instead of five-coordinate [(C6F5NCH2-
CH2)2NMe]Mo(NMe2)2 (Figure 3). The N(5)-Mo-N(2)
angle is only 95.19(19)°, as a consequence of the high
coordination number. The Mo-N(1) and Mo-N(3) bond
lengths are slightly longer than the Mo-N(4) bond
length, presumably for steric reasons. The mechanism
of this unusual reaction is not known. The favored
proposal at this stage is nucleophilic attack on the ortho
carbon of the C6F5 ring by a coordinated amide or free
amine, followed by loss of F- or direct transfer of the
ortho fluoride to Mo. In any case, this result reveals the
potential complications that might arise through the use
of C6F5-substituted amides in the presence of strong
nucleophiles. The yield of [(C6F4(NMe2)NCH2CH2)2NMe]-
Addition of 3 equiv of MeMgCl to [Et3NH]{[ArFNMe]-
MoCl3} in THF led to a deep forest green, paramagnetic
product in 50% yield21 with 19F NMR resonances (in
THF) at -57.2, -73.0, -106.0, -147.4, and -149.0 ppm.
An X-ray study revealed this species to be [ArFNMe]-
MoMe2 (Figure 2). The geometry is approximately
(19) Methyl iodide (1.86 mL, 29.9 mmol) was added dropwise to a
stirred mixture of (C6F5NHCH2CH2)2NH (10 g, 23.0 mmol) and K2-
CO3 (17.5 g, 126 mmol) in CH3CN (120 mL). After 15 h the volatile
components were removed in vacuo and the residue was washed with
water (200 mL) and extracted into ethyl acetate (200 mL). The product
was isolated from the ethyl acetate layer.
(20) MoCl4(THF)2 (2.55 g, 6.67 mmol) was added as a solid to a
stirred solution of (C6F5NHCH2CH2)2NMe (3 g, 6.67 mmol) in THF (50
mL) at room temperature. After 30 min NEt3 (2.0 mL, 14.35 mmol)
was added. After an additional 2 h the reaction mixture was filtered
through Celite and the filtrate was added to 100 mL of rapidly stirred
pentane. The burgundy product was filtered off; yield 4.70 g (83%).
(21) A solution of MeMgCl (3.2 M in THF) was added to a solution
of [HNEt3]{[(C6F5NCH2CH2)2NMe]MoCl3} (0.75 g, 1.01 mmol) in THF
(20 mL) at -30 °C. The reaction was allowed to warm to room
temperature as it was stirred. After 30 min, the solution was
concentrated to dryness in vacuo. The residue was extracted into ether
(20 mL), and 1,4-dioxane (0.28 mL) was added. The mixture was
filtered through Celite, and the filtrate was added dropwise to rapidly
stirred volume of pentane (100 mL). A small amount of brown solid
was filtered off, and the filtrate was concentrated to approximately
15 mL to produce green crystalline product; yield 0.29 g (50%).

2416 Organometallics, Vol. 19, No. 13, 2000
Communications
F igu r e 4. ORTEP drawing (30% probability) of the
structure of [(C6F5NCH2CH2)2NMe]Re(O)Cl (bond lengths
in Å, angles in deg): Re-O(1) ) 1.675(9), Re-N(2) ) 1.951-
(7), Re-N(3) ) 1.960(7), Re-N(1) ) 2.154(8), Re-Cl(1) )
2.362(2), O(1)-Re-N(2) ) 118.9(3), N(2)-Re-N(3) )
119.7(3), O(1)-Re-N(1) ) 97.7(4), N(2)-Re-N(1) ) 80.4-
(3), O(1)-Re-Cl(1) ) 102.8(3), N(2)-Re-Cl(1) ) 89.9(2),
N(1)-Re-Cl(1) ) 159.5(3). [C17H11ClF10N3ORe, monoclinic,
P21/n, a ) 7.923(3) Å, b ) 19.766(4) Å, c ) 13.182(4) Å, â
) 106.182(19)°, R1 ) 0.0435, wR2 ) 0.1084 (all data).]
F igu r e 3. ORTEP drawing (30% probability) of the
structure of [(C6F4(NMe2)NCH2CH2)2NMe]MoF2 (bond
lengths in Å, angles in deg): Mo-F(1) ) 1.968(3), Mo(1)-
F(10) ) 1.933(3), Mo-N(5) ) 2.008(5), Mo-N(2) ) 2.013-
(5), Mo-N(4) ) 2.330(5), Mo-N(1) ) 2.440(5), Mo-N(3) )
2.482(5), F(10)-Mo-F(1) ) 120.45(14), F(10)-Mo-N(5) )
123.20(16), F(1)-Mo-N(5) ) 90.99(16), N(5)-Mo-N(2) )
95.19(19), N(5)-Mo-N(4) ) 76.46(18). [C48H46F10MoN5,
monoclinic, P21/n, a ) 11.237(8) Å, b ) 13.674(9) Å, c )
17.159(12) Å, â ) 99.936(12)°, T ) 293(2) K, R1 ) 0.0914,
wR2 ) 0.1110 (all data).]
other Mo compounds presented here, perhaps as a
consequence of the higher formal oxidation state of the
metal.
MoF2 probably is not high, as evidenced by a substantial
amount of free ligand produced along with other un-
known paramagnetic products.
We conclude that five-coordinate or six-coordinate
complexes of Mo, W, and Re that contain the [(C6F5-
NCH2CH2)NMe]2- ligand can be prepared from d2 Mo,
W, or Re halides by relatively “direct” routes. We are
currently exploring the chemistry of these new species,
in particular with regard to dinitrogen fixation and
reduction. We are also exploring the possibility of
synthesizing similar complexes that contain less electron-
withdrawing aryl substituents on the amido nitrogens,
as well as complexes that contain bulkier aryl rings to
better protect the metal center against bimolecular
reactions.
We have reported that the reaction between (C6F5-
NHCH2CH2)3N, [NEt4]2[Re(O)Cl5], and NEt3 produces
a five-coordinate oxo chloro Re(V) species in which the
[(C6F5NCH2CH2)2N(CH2CH2NHC6F5)]2- ligand is
present; this complex was not structurally character-
ized.22 A similar reaction between H2[ArFNMe], [NEt4]2-
[Re(O)Cl5], and NEt3 produced an aquamarine-colored
diamagnetic product that is virtually insoluble in all
common solvents with the exception of pyridine, in
which it displays only moderate solubility (eq 3). Al-
H2[ArFNMe] + [NEt4][Re(O)Cl5] 2.2 NEt , CH CN8
3
3
22 °C, 30 min
Ack n ow led gm en t. R.R.S. thanks the National In-
stitutes of Health (GM 31978) for research support.
F.V.C. thanks J onathan Goodman and George Greco for
helpful discussions.
[ArFNMe]Re(O)Cl (3)
lowing pentane to diffuse into a pyridine solution of the
complex over several hours yielded crystals of suitable
quality for X-ray diffraction. The complex was found to
be a trigonal bipyramid with the oxo ligand in the
equatorial position (Figure 4). The relatively short Re-
O(1) distance (1.675(9) Å) reflects the pseudo triple bond
character of this moiety. The Re-N(2), Re-N(3), and
Re-N(1) distances are all somewhat shorter than in the
Su p p or tin g In for m a tion Ava ila ble: Experimental de-
tails, labeled ORTEP drawings, crystal data and structure
refinement, atomic coordinates, bond lengths and angles, and
anisotropic displacement parameters for [Et3NH]{[ArFNMe]-
MoCl3}, [ArFNMe]MoMe2, [(C6F4(NMe2)NCH2CH2)2NMe]MoF2,
and [ArFNMe]Re(O)Cl. This material is available free of charge
via the Internet at http://pubs.acs.org.
(22) Reid, S. M.; Neuner, B.; Schrock, R. R.; Davis, W. M. Organo-
metallics 1998, 17, 4077.
OM0001117