Synthesis and protonolysis of tungsten- and molybdenum - Dinitrogen complexes bearing ruthenocenyldiphosphines

Article abstract of DOI:10.1021/om900298g

Tungsten - and molybdenum - dinitrogen complexes bearing 1,1′-bis(diethylphosphino)ruthenocene (depr) or 1,1′- bis(dimethylphosphino)ruthenocene (dmpr) have been prepared and characterized spectroscopically. Reactions of tungsten- and molybdenum - dinitro

Full text of DOI:10.1021/om900298g

Organometallics 2009, 28, 4741–4746 4741
DOI: 10.1021/om900298g
Synthesis and Protonolysis of Tungsten- and Molybdenum-Dinitrogen
Complexes Bearing Ruthenocenyldiphosphines
Masahiro Yuki, Tatsuya Midorikawa, Yoshihiro Miyake, and Yoshiaki Nishibayashi*
Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi, Bunkyo-ku,
Tokyo 113-8656, Japan
Received April 21, 2009
Tungsten- and molybdenum-dinitrogen complexes bearing 1,10-bis(diethylphosphino)ruthenocene
(depr) or 1,10-bis(dimethylphosphino)ruthenocene (dmpr) have been prepared and characterized
spectroscopically. Reactions of tungsten- and molybdenum-dinitrogen complexes bearing ruthenoce-
nyldiphosphines with an excess amount of sulfuric acid in methanol at room temperature give ammonia
in good yields.
Ferrocene and its derivatives are widely used in organome-
tallic chemistry and material sciences.1 Ferrocene-based ligands
are also of increasing importance in transition-metal-catalyzed
organic syntheses, including asymmetric transformations.2,3
Ferrocenyldiphosphines such as 1,10-bis(diphenylphosphino)-
ferrocene (dppf) are common diphosphine ligands because of
their relatively large bite angle, capacity for dative bond
formation with electron-deficient metal centers, and chemi-
cal robustness of the ferrocene skeleton.3 It is also known
that the catalytic behavior of complexes can be fine-tuned
by replacing the ferrocenyldiphosphines with ruthenocenyl-
diphosphines.4 In general, a ruthenocenyldiphosphine such
as 1,10-bis(diphenylphosphino)ruthenocene (dppr) gives a
slightly larger bite angle compared to dppf, as a consequence
of the larger atomic radii of ruthenium.5 In addition, it is also
possible that the difference in electronic properties between
ferrocene and ruthenocene moieties modifies the electronic
and structural properties of the corresponding complexes
bearing these metallocenes.6
Recently, we have reported the preparation of tungsten-
and molybdenum-dinitrogen complexes bearing ferrocenyldi-
phosphines as auxiliary ligands, [M(N2)2(depf)2] (M = W,
Mo; depf = 1,10-bis(diethylphosphino)ferrocene).7 Reactions
of these dinitrogen complexes with an excess amount of sulfuric
acid afforded ammonia in good yields. It is noteworthy that the
ferrocene moiety in these complexes plays an important role in
the conversion of the coordinated dinitrogen into ammonia.8
This result is in sharp contrast to the previous result that
protonolysis of tungsten- and molybdenum-dinitrogen com-
plexes bearing conventional diphosphines such as [M(N2)2-
(dppe)2] and [M(N2)2(depe)2] did not produce ammonia. In the
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*To whom correspondence should be addressed. E-mail: ynishiba@
sogo.t.u-tokyo.ac.jp.
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Nishihara, H. Adv. Inorg. Chem. 2002, 53, 41. (c) Nakamura, E. Pure Appl.
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2009 American Chemical Society
Published on Web 07/24/2009
pubs.acs.org/Organometallics

4742 Organometallics, Vol. 28, No. 16, 2009
Yuki et al.
Scheme 1
Scheme 2
Figure 1. ORTEP view of trans-[W(N2)2(depr)(PPh2Me)2] (1)
˚
with 50% thermal ellipsoids. Selected interatomic distances (A)
and bond angles (deg): W-P(1)=2.512(2), W-P(2)=2.518(2),
W-P(3)=2.479(2), W-P(4)=2.461(2), W-N(1)=1.967(5), W-
N(3)=1.972(6), N(1)-N(2)=1.161(8), N(3)-N(4)=1.138(9),
W
Ru=4.5775(7); P(1)-W-P(2)=98.72(6), P(2)-W-P(3) =
3 3 3
88.93(6), P(3)-W-P(4) = 85.23(7), P(4)-W-P(1) = 90.32(7),
N(1)-W-N(3)=178.7(2).
course of our continuing interest in dinitrogen fixation chem-
istry,7-11 we now report the preparation and protonation of
tungsten- and molybdenum-dinitrogen complexes bearing
ruthenocenyldiphosphines as auxiliary ligands.
Results and Discussion
Ruthenocenyldiphosphines were prepared by a procedure
similar to that for ferrocenyldiphosphines.7 Dilithiation
of ruthenocene with n-butyllithium-TMEDA in hexane
at room temperature afforded a white powder of 1,10-
dilithioruthenocene, which was treated with PEt2Cl to give
1,10-bis(diethylphosphino)ruthenocene (depr) in 25% yield
(Scheme 1). Similarly, 1,10-bis(dimethylphosphino)ruthe-
nocene (dmpr) was also prepared in 22% yield by using
PMe2Cl instead of PEt2Cl.
Figure 2. Structures of trans-[W(N2)2(depr)(PPh2Me)2] (1)
(left) and trans-[W(N2)2(depf)(PPh2Me)2]12 (right).
of depf in trans-[W(N2)2(depf)(PPh2Me)2] (96.72(6)°)12
˚
(Figure 2). The W-Ru distance of 4.5775(7) A indicated
no bonding interaction between ruthenium and tungsten
The reaction of trans-[W(N2)2(PPh2Me)4] with 2 equiv of
depr at 60 °C for 12 h gave trans-[W(N2)2(depr)(PPh2Me)2]
(1) as a major complex together with a trace amount of
trans-[W(N2)2(depr)2] (2) (Scheme 2). Recrystallization of
the mixture of two complexes from THF-hexane afforded 1
in 29% isolated yield as orange-red plates. The IR spectrum
atoms and was almost the same as the W-Fe distance of
trans-[W(N2)2(depf)(PPh2Me)2] (4.5631(11) A).
˚
Next, we carried out the reaction of trans-[W(N2)2-
(PPh2Me)4] with an excess amount of depr at a higher reaction
temperature such as 70 °C for 4 h to afford trans-[W(N2)2-
(depr)2] (2) in 29% yield as a pink powder (Scheme 2). The 1H
NMR spectrum of 2 was very similar to that of trans-[W(N2)2-
(depf)2] (3). In the 31P{1H} NMR spectrum of 2, four equiva-
lent phosphorus atoms were observed at -6.8 ppm as a singlet
with 183W satellites (1JPW =319 Hz). The IR spectrum of 2
showed a strong absorption band for νNN at 1879 cm-1, which
was almost the same frequency as that of 3 (νNN 1883 cm-1).
These observations were consistent with the trans configura-
tion of 2, as in the case of 3. A cyclic voltammogram (CV) of 2
showed a reversible one-electron-oxidation wave at -0.97 V
assignable to the W(0/I) redox couple. This value was very
close to the values observed for 3 and trans-[W(N2)2(depe)2], as
shown in Table 1. Both the IR and CV data of 2 display the
same strongly electron donating properties of depr as for depf.
The reaction of trans-[W(N2)2(PPh2Me)4] with 1 equiv of
dmpr at 60 °C for 3 h afforded trans-[W(N2)2(dmpr)-
(PPh2Me)2] (4) in 39% yield (Scheme 3). The IR spectrum
of 1 exhibited one absorption band for νNN at 1895 cm-1
,
indicating the trans arrangement of two dinitrogen ligands.
In the 31P{1H} NMR spectrum, four phosphorus atoms
displayed an AA0BB0 spectrum centered at -8.5 ppm, due
to two pairs of chemically equivalent but magnetically
inequivalent phosphorus atoms bound to a tungsten center.
The molecular structure of 1 was unequivocally determined
by X-ray crystallography. An ORTEP drawing of 1 is shown
in Figure 1. Around the octahedrally coordinated tungsten
center, two dinitrogen ligands occupied positions trans to
each other. The ruthenocene moiety adopts a staggered
conformation with a rotation angle of 46.4°. The bite angle
of depr in 1 is 98.72(6)°. This value is slightly larger than that
(12) Yuki, M.; Miyake, Y.; Nishibayashi, Y. Unpublished results.
Crystal data for trans-[W(N2)2(depf)(PPh2Me)2] are given in the Sup-
porting Information.

Article
Organometallics, Vol. 28, No. 16, 2009 4743
Scheme 3
Scheme 5
The reaction of trans-[Mo(N2)2(PPh2Me)4] with 1 equiv of
dmpr gave trans-[Mo(N2)2(dmpr)(PPh2Me)2] (7) in 56%
yield (Scheme 5). The IR and NMR spectra of 7 supported
the structure of 7. The molecular structure of 7 was con-
firmed by X-ray crystallography, as shown in Figure 3. The
ruthenocene moiety of 7 adopts an eclipsed conformation
with a rotation angle of 11.1°, in contrast to the staggered
structure of 1. This conformation is due to the remarkably
small bite angle of the dmpr ligand (88.33(3)°). The bond
angle betweenthe two PPh2Me ligands is rather large (P(3)-
Mo-P(4)=92.66(2)°). These structural differences indicate
that the conformations of ruthenocene moieties are deter-
mined by the subtle balance of steric repulsion between the
coordinated ligands in these complexes. Both eclipsed and
staggered conformations were previously observed for two
ferrocene moieties in one molecule of trans-[M(N2)2(depf)2]
(M=W, Mo).7 When the reaction was carried out with an
excess amount of dmpr, the formation of the possible com-
plex trans-[Mo(N2)2(dmpr)2] (8) was observed in solution by
NMR spectra.14 Unfortunately, any effort to isolate 8 has
been in vain at the present.
Scheme 4
of 4 exhibited one absorption band of νNN at 1899 cm-1. A
cyclic voltammogram of 4 showed a reversible W(0/I) redox
wave at -0.80 V, close to that of 1. On the other hand, we
could not obtain a complex such as trans-[W(N2)2(dmpr)2],
even if the reaction was carried out with an excess amount of
dmpr for a longer reaction time.
Finally, we investigated the reactivity of novel tungsten-
and molybdenum-dinitrogen complexes toward protonoly-
sis.15,16 Reactions of dinitrogen complexes with an excess
amount of sulfuric acid in methanol at room temperature for
24 h gave ammonia in all cases (Scheme 6). In no case was
hydrazine detected. Similar to the previous results of the
protonation of dinitrogen complexes,15 dinitrogen com-
plexes bearing monodentate phosphines as auxiliary ligands
such as 1, 4, 5, and 7 gave ammonia in good to high yields.
Interestingly, protonation of 2 with sulfuric acid also gave
ammonia in 68% yield based on the tungsten atom. This
result is in sharp contrast with those for molybdenum- and
tungsten-dinitrogen complexes bearing chelating dipho-
sphines as auxiliary ligands [M(N2)2L2] (M=Mo, W; L=
dppe, depe), where ammonia was not found and only the
The reaction of trans-[Mo(N2)2(PPh2Me)4] with 2 equiv of
depr proceeded even at room temperature to give a mixture
of trans-[Mo(N2)2(depr)(PPh2Me)2] (5) and trans-[Mo(N2)2-
(depr)2] (6) as an orange powder (Scheme 4). The 1H NMR
spectrum of the powder exhibited signals assignable to 5 and
6 in a ratio of ca. 15:1. The chemical shifts were almost same
as for the corresponding tungsten complexes 1 and 2, respec-
tively. The 31P{1H} NMR spectrum showed a set of sym-
metric multiplet signals centered at 20.5 ppm consistent with
the AA0BB0 spin system of 5 due to four phosphorus atoms
bound to the molybdenum center. A singlet signal of 6 was
also observed at 21.6 ppm. When the reaction was carried out
with an excess amount of depr, complex 6 was observed as a
major product in benzene-d6 solution by NMR. However, we
have not yet isolated 5 or 6 in pure form.
Table 1. IR and Electrochemical Data of Tungsten- and Molybdenum-Dinitrogen Complexes
complexa
ν
NN(asym)/cm-1b
E1/2/V c
ref
trans-[W(N2)2(depr)(PPh2Me)2] (1)
trans-[W(N2)2(depr)2] (2)
trans-[W(N2)2(dmpr)(PPh2Me)2] (4)
trans-[W(N2)2(depf)2]
trans-[W(N2)2(depe)2]
trans-[W(N2)2(dppe)2]
trans-[W(N2)2(dchpe)2]
trans-[W(N2)2(dppe)(PPh2Me)2]
trans-[W(N2)2(PPh2Me)4]
trans-[W(N2)2(PPhMe2)4]
trans-[Mo(N2)2(dmpr)(PPh2Me)2] (7)
trans-[Mo(N2)2(depf)2]
1895
1879
1899
1883
1895
1943
1880d
1920d
1899
1898
1925
1907
1928
1975
1943d
1922
-0.83
-0.97
-0.80
-0.95
-0.96
-0.68
-1.02
this work
this work
this work
7
13a,13b
13a,13b
13b
13c
7,13c
13d
this work
7
-0.71
-0.83
-0.80
-0.97
-0.97
-0.70
trans-[Mo(N2)2(depe)2]
trans-[Mo(N2)2(dppe)2]
trans-[Mo(N2)2(dppe)(PPh2Me)2]
trans-[Mo(N2)2(PPh2Me)4]
13b,13e
13b
13c
-0.71
13f,13g
a Abbreviations: dppe=1,10-bis(diphenylphosphino)ethane; depe=1,10-bis(diethylphosphino)ethane; dchpe=1,10-bis(dicyclohexylphosphino)ethane.
b Asymmetric NN stretching bands in KBr pellets. c Relative to ferrocene-ferrocenium couple in THF. d Nujol mull.

4744 Organometallics, Vol. 28, No. 16, 2009
Yuki et al.
Scheme 6
Figure 3. ORTEP view of trans-[Mo(N2)2(dmpr)(PPh2Me)2] (7)
˚
with 50% thermal ellipsoids. Selected interatomic distances (A) and
bond angles (deg): Mo-P(1) = 2.4635(10), Mo-P(2) = 2.4881-
(9), Mo-P(3) = 2.4856(8), Mo-P(4) = 2.4763(9), Mo-N(1) =
2.012(2), Mo-N(3)=2.009(2), N(1)-N(2)=1.128(3), N(3)-N-
(N2)2(depr)2] with 2 equiv of HOTf. At present, we have not
yet clarified the exact role of ruthenocenyldiphosphines in
these dinitrogen complexes, but it may be possible to assume
that the electron transfer process from ruthenocene units to
the tungsten or molybdenum center assists the reduction of
the dinitrogen molecule to ammonia. A similar electron
transfer has been previously proposed in the protonation
of tungsten- and molybdenum-dinitrogen complexes bear-
ing ferrocenyldiphosphines.7
In summary, we have prepared novel tungsten- and
molybdenum-dinitrogen complexes bearing ruthenocenyl-
diphosphines as auxiliary ligands. Reactions of these com-
plexes with an excess amount of sulfuric acid in methanol at
room temperature gave ammonia in good yields. Although
the details are not yet clear, the ruthenocene moiety in these
complexes plays an important role in the facile conversion of
the coordinated dinitrogen into ammonia.
(4)=1.126(3), Mo Ru=4.5215(3); P(1)-Mo-P(2)=88.33(3),
3 3 3
P(2)-Mo-P(3) = 92.17(3), P(3)-Mo-P(4) = 92.66(2), P(4)-
Mo-P(1)=89.21(3), N(1)-Mo-N(3)=175.02(11).
formation of the corresponding hydrazido complexes was
observed.16 On the other hand, the result described in this
paper is similar to those for protonation of tungsten- and
molybdenum-dinitrogen complexes bearing ferrocenyldi-
phosphines such as trans-[M(N2)2(depf)2] (M=W, Mo) with
sulfuric acid, where ammonia was obtained in 129% and
48% yields, respectively.7 Although we previously isolated
the corresponding hydrazido complexes as reactive
intermediates in the protonation of trans-[M(N2)2(depf)2]
(M = W, Mo) with 2 equiv of HOTf,7 we cannot isolate
similar hydrazido complexes in the protonation of trans-[W-
Experimental Section
1
General Method. H NMR (270 MHz) and 31P{1H} NMR
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(109 MHz) spectra were measured on a JEOL Excalibur 270
spectrometer, and 31P chemical shifts were quoted relative to an
external standard of 85% H3PO4. The chemical shifts and the
coupling constants of AA0BB0 spin systems were determined by
line shape analysis.17 IR spectra were recorded on a JASCO FT/
IR 4100 Fourier transform infrared spectrophotometer. Ele-
mental analyses were performed on an Exeter Analytical CE-
440 elemental analyzer or at the Microanalytical Center of The
University of Tokyo. Cyclic voltammograms were recorded on
an ALS/Chi Model 610C electrochemical analyzer with a pla-
tinum working electrode in THF containing 0.1 M nBu4NBF4 as
a supporting electrolyte. The potentials were quoted relative to
the ferrocene/ferrocenium couple. All manipulations were per-
formed under a dry nitrogen atmosphere. Solvents were dried
over appropriate reagents and distilled prior to use. N,N,N0,N0-
Tetramethylethylenediamine (TMEDA) was distilled from
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NMR (270 MHz, C6D6): δ 4.80 (t, J = 2 Hz, 8H, C5H4), 4.61 (t, J = 2
Hz, 8H, C5H4), 1.62 (br s, 24H, Me). 31P{1H} NMR (C6D6): δ 4.4 (s).
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S. N.; Richards, R. L.; Hughes, D. L. J. Chem. Soc., Dalton Trans. 1986,
245.
(16) (a) Heath, G. A.; Mason, R.; Thomas, K. M. J. Am. Chem. Soc.
1974, 96, 259. (b) Hidai, M.; Kodama, T.; Sato, M.; Hirakawa, M.; Uchida, Y.
Inorg. Chem. 1976, 15, 2694. (c) Chatt, J.; Leigh, G. J.; Neukomm, H.;
Pickett, C. J.; Stanley, D. R. J. Chem. Soc., Dalton Trans. 1980, 121. (d)
Nishihara, H.; Mori, Y.; Nakano, K.; Saito, T.; Sasaki, Y. J. Am. Chem. Soc.
1982, 104, 4367. (e) Henderson, R. A. J. Chem. Soc., Dalton Trans. 1982,
917. (f) Bakar, M. A.; Hughes, D. L.; Hussain, W.; Leigh, G. J.; Macdonald,
C. J.; Mohd.-Ali, H. J. Chem. Soc., Dalton Trans. 1988, 2545. (g) Barclay, J.
E.; Hills, A.; Hughes, D. L.; Leigh, G. J.; Macdonald, C. J.; Bakar, M. A.;
Mohd.-Ali, H. J. Chem. Soc., Dalton Trans. 1990, 2503.
calcium hydride. The complexes trans-[W(N2)2(PPh2Me)4] -
3
1.5THF13c and trans-[Mo(N2)2(PPh2Me)4]18 were prepared by
the literature methods. Other reagents were purchased and used
as received.
Preparation of 1,10-Bis(diethylphosphino)ruthenocene (depr).
A mixture of ruthenocene (4.00 g, 17.3 mmol), TMEDA (5.2
mL, 34.5 mmol), and nBuLi (1.58 M, 22.0 mL, 34.8 mmol) in n-
(17) Reich, H. J. WINDNMR: NMR Spectrum Calculations, version
7.1.12; Department of Chemistry, University of Wisconsin, Madison, WI,
2005.
(18) Lazarowych, N. J.; Morris, R. H.; Ressner, J. M. Inorg. Chem.
1986, 25, 3926.

Article
Organometallics, Vol. 28, No. 16, 2009 4745
hexane (25 mL) was stirred at room temperature overnight. The
pale yellow precipitates were separated from the supernatant by
decantation and were washed with n-hexane (50 mL). After
removal of the washings, the precipitates were suspended into
hexane (30 mL). To the suspension was added PEt2Cl (5.0 g,
40.1 mmol), and the mixture was stirred at room temperature
overnight. The reaction mixture was filtered through a Celite
pad, and the filtrate was concentrated in vacuo. The pale yellow
residue was subjected to silica gel column chromatography.
Elution with n-hexane-benzene (1/1) afforded depr (1.38 g,
25%) as a pale yellow solid. 1H NMR (C6D6): δ 4.59-4.56 (m,
4H, C5H4), 4.55-4.53 (m, 4H, C5H4), 1.50 (q, 3JHH=8 Hz, 8H,
CH2), 1.06 (dt, 3JPH=15 Hz, 3JHH=8 Hz, 12H, CH3). 31P{1H}
NMR (C6D6): δ -27.2 (s). Anal. Calcd for C18H28P2Ru: C,
53.06; H, 6.93. Found: C, 53.06; H, 6.99.
Table 2. Summary of Crystallographic Data for 1 and 7
1
7
formula
C44H54N4P4RuW
1047.75
C40H46N4P4MoRu
903.73
formula wt
cryst size/mm
color, habit
cryst syst
space group
˚
0.15 ꢀ 0.10 ꢀ 0.02
orange plate
monoclinic
P21/n (No. 14)
10.4793(7)
19.8614(12)
20.6273(13)
99.581(4)
4233.4(5)
4
1.644
3.263
30 497 (2θ < 50°)
7470 (0.118)
541
0.30 ꢀ 0.30 ꢀ 0.15
orange plate
monoclinic
P21/n (No. 14)
12.9067(5)
22.0993(7)
14.0746(6)
104.0972(13)
3893.6(2)
4
1.542
9.085
37 334 (2θ < 55°)
8861 (0.053)
497
a/A
˚
b/A
˚
c/A
β/deg
3
˚
V/A
Z
dc/g cm-3
μ(Mo KR)/mm-1
no. of data collected
no. of unique data (Rint
no. of params refined
R1a (F2 > 2σ)
wR2b (all data)
Preparation of 1,10-Bis(dimethylphosphino)ruthenocene (dmpr).
The compound was obtained in 22% yield by a procedure
similar to that for depr, using Me2PCl in place of Et2PCl. H
)
1
NMR (C6D6): δ 4.54 (t, 3JHH=1 Hz, 4H, C5H4), 4.51 (t, 3JHH
=
0.046
0.061
0.94
þ1.71 to -1.86
0.034
0.072
1.02
þ0.97 to -1.09
1 Hz, 4H, C5H4), 1.06 (d, 2JPH = 3 Hz, 12H, Me). 31P{1H} NMR
(C6D6): δ -56.9 (s). Anal. Calcd for C14H20P2Ru: C, 47.86; H,
5.74. Found: C, 47.67; H, 5.73.
goodness of fit indicatorc
residual electron
˚
density/e A
-3
Preparation of trans-[W(N2)2(depr)(PPh2Me)2] (1). A solution
of trans-[W(N2)2(PMePh2)4] 1.5THF (500 mg, 0.435 mmol)
P
P
P
P
a R1 = ||Fo| - |Fc||/ |Fo|. b wR2 = [ w(Fo2 - Fc2)2/ w(Fo)2]1/2
.
3
P
c
and depr (397 mg, 0.974 mmol) in THF (15 mL) was stirred at
60 °C for 12 h. After removal of the solvent under reduced
pressure, the residue was washed with hexane and recrystallized
from THF-hexane, affording red plates of 1 (132 mg, 0.126 mmol,
29%). 1H NMR (270 MHz, C6D6): δ 7.62 (br t, J=7 Hz, 8H, Ph),
7.07 (t, J=7 Hz, 8H, Ph), 6.98 (t, J = 7 Hz, 4H, Ph), 4.80 (br, 4H,
C5H4), 4.61 (t, J=1 Hz, 4H, C5H4), 2.14-1.98 (m, 4H, CH2), 2.03
(br, 6H, PPh2Me), 1.80-1.62 (m, 4H, CH2), 1.04-0.91 (m, 12H,
PCH2CH3). 31P NMR (109 MHz, C6D6): δ -8.2 (1JPW=318 Hz),
-8.7 (1JPW =314 Hz) (AA0BB0 spin system with 183W satellites,
[
w(Fo2 - F2c)2/(Nobservns - Nparams)]1/2
.
temperature for 24 h. After removal of the volatiles in vacuo, the
residue was washed with hexane (10 mL ꢀ 2) and extracted with
toluene (40 mL). The extract was concentrated under vacuum,
giving a mixture of trans-[Mo(N2)2(depr)(PPh2Me)2] (5) and
trans-[Mo(N2)2(depr)2] (6) as an orange powder (165 mg). The
1H NMR spectrum indicated that the powder contains 5 and 6 in
a ratio of ca. 15:1. Further purification of the products was not
successful. NMR data for 5 are as follows. 1H NMR (270 MHz,
C6D6): δ 7.61 (t, J=7 Hz, 8H, Ph), 7.07 (t, J=7 Hz, 8H, Ph), 6.99
(t, J=7 Hz, 4H, Ph), 4.80 (br, 4H, C5H4), 4.62 (t, J=1 Hz,
4H, C5H4), 1.95-1.82 (m, 4H, CH2), 1.88 (d, 2JHP=3 Hz, 6H,
PPh2Me), 1.65-1.47 (m, 4H, CH2), 1.05-0.93 (m, 12H,
CH2Me). 31P NMR (109 MHz, C6D6): δ 21.8 and 19.2
0
0
0
J
AB(trans) = 123 Hz, JAB =-17 Hz, JAA and JBB =-24 and
-42 Hz). IR (KBr): νNN 1961 vw, 1895 vs cm-1. Anal. Calcd for
C44H54N4P4RuW: C, 50.44; H, 5.19; N, 5.35. Found: C, 50.18; H,
5.34; N, 5.43.
Preparation of trans-[W(N2)2(depr)2] (2). A solution of
trans-[W(N2)2(PMePh2)4] 1.5THF (206 mg, 0.179 mmol) and
(AA0BB0 spin system, JAB(trans)=105 Hz, JAB =-8 Hz, JAA
3
0
0
depr (463 mg, 1.14 mmol) in toluene (10 mL) was heated at 70 °C
for 4 h. After concentration, the dark orange oily residue was
washed with hexane (15 mL) to give a red solid. The solid was
dissolved in THF, followed by precipitation with hexane, to give
0
and JBB =-13 and -21 Hz, PPh2Me and depr). NMR data for 6
are as follows. 1H NMR (C6D6): δ 4.90 (t, J=2 Hz, 8H, C5H4),
4.64 (t, J = 2 Hz, 8H, C5H4), 2.45-2.10 (m, 16H, CH2), 1.25-
1.10 (m, 24H, Me). 31P{1H} NMR (C6D6): δ 21.6 (s).
1
2 as a pink powder (54 mg, 29%). H NMR (C6D6): δ 4.89 (t,
Preparation of trans-[Mo(N2)2(dmpr)(PPh2Me)2] (7). A solu-
tion of trans-[Mo(N2)2(PPh2Me)4] (191 mg, 0.200 mmol) and
dmpr (71 mg, 0.203 mmol) in toluene (15 mL) was stirred at
room temperature for 3 h. The solvent was removed under
reduced pressure. Recrystallization from THF-hexane af-
forded orange plates of 7 (101 mg, 56%). 1H NMR (270 MHz,
C6D6): δ 7.49 (t, J=8 Hz, 8H, Ph), 7.03 (t, J=8 Hz, 8H, Ph), 6.95
(t, J = 8 Hz, 4H, Ph), 4.90 (q, J = 1 Hz, 4H, C5H4), 4.54 (t, J=1
Hz, 4H, C5H4), 1.89 (d, 2JPH=4 Hz, 6H, PPh2Me), 1.35 (d, 2JPH
=4 Hz, 12H, PMe2). 31P{1H} NMR (C6D6): δ 23.0 (d, 3JPP=95
Hz, PPh2Me), 1.70 (d, 3JPP=95 Hz, dmpr). IR (KBr): νNN 2000
J=2 Hz, 8H, C5H4), 4.64 (t, J = 2 Hz, 8H, C5H4), 2.45-2.18 (m,
16H, CH2), 1.25-1.11 (m, 24H, Me). 31P{1H} NMR (C6D6): δ -
6.8 (s with 183W satellites, 1JP-W=319 Hz). IR (KBr): νNN 1960
vw, 1879 vs cm-1. Anal. Calcd for C36H56N4P4Ru2W: C, 40.99;
H, 5.35; N, 5.31. Found: C, 41.02; H, 5.40; N, 5.06.
Preparation of trans-[W(N2)2(dmpr)(PPh2Me)2] (4). A mix-
ture of trans-[W(N2)2(PMePh2)4] 1.5THF (230 mg, 0.200 mmol)
3
and dmpr (77 mg, 0.219 mmol) in THF (10 mL) was heated
at 60 °C for 3 h. The solution was concentrated to ca. 1 mL,
and hexane (15 mL) was added to the solution. After the
resulting orange precipitate was removed by filtration, the
solution was concentrated to dryness. The orange oily residue
was triturated with hexane to give an orange powder of 4 (78 mg,
vw, 1925 vs cm-1
.
Anal. Calcd for C40H46-
N4MoP4Ru: C, 53.16; H, 5.13; N, 6.20. Found: C, 53.12; H,
5.26; N, 6.02.
1
39%). H NMR (C6D6): δ, 7.47 (t, J=8 Hz, 8H, Ph), 7.03 (t,
Protonation of Dinitrogen Complexes with Sulfuric Acid. To a
methanol (5 mL) suspension of dinitrogen complex (ca. 40 μmol)
was added H2SO4 (0.05 mL). After 24 h of stirring at room
temperature, ammonia was base-distilled and quantified by the
indophenol method.19 Hydrazine was also analyzed with
p-(dimethylamino)benzaldehyde reagent.20
J=8 Hz, 8H, Ph), 6.94 (t, J=8 Hz, 4H, Ph), 4.90 (q, J=2 Hz, 4H,
C5H4), 4.53 (t, J=2 Hz, 4H, C5H4), 2.30 (br d, 2JPH=5 Hz, 8H,
PPh2Me), 1.46 (d, 2JPH=6 Hz, 12H, PMe2). 31P NMR (C6D6): δ
-4.6 (dt with 183W satellites, 2JPP=111 and 7 Hz, 1JPW=319 Hz,
2
PPh2Me), -26.3 (dt with 183W satellites, JPP=111 and 7 Hz,
1JPW=322 Hz, dmpr). IR (KBr): νNN 1970 vw, 1899 vs cm-1
Anal. Calcd for C40H46N4P4RuW: C, 48.45; H, 4.68; N, 5.65.
Found: C, 48.76; H, 4.51; N, 5.38.
.
X-ray Crystallography of 1 and 7. Crystallographic data for
complexes 1 and 7 are summarized in Table 2. A paraffin-coated
Reaction of trans-[Mo(N2)2(PPh2Me)4] with depr. A solution
of trans-[Mo(N2)2(PPh2Me)4] (203 mg, 0.213 mmol) and depr
(178 mg, 0.437 mmol) in toluene (10 mL) was stirred at room
(19) Chaney, A. L.; Marbach, E. P. Clin. Chem. 1962, 8, 130.
(20) Watt, G. W.; Chrisp, J. D. Anal. Chem. 1952, 24, 2006.

4746 Organometallics, Vol. 28, No. 16, 2009
Yuki et al.
crystal was placed on a nylon loop and mounted on a Rigaku
RAXIS RAPID imaging plate system. Data were collected at
-100 °C under a cold nitrogen stream using graphite-mono-
Full-matrix least-squares refinement on F2 was carried out until
the maximum parameter shift/esd converged to less than
0.001.23 All calculations were performed using the Crystal
Structure software package.24
˚
chromated Mo KR radiation (λ = 0.710 69 A). Data were
corrected for absorption, Lorentz, and polarization effects.
The structures were solved by direct methods21 and expanded
using Fourier techniques.22 Anisotropic thermal parameters
were introduced for the other non-hydrogen atoms. Hydrogen
atoms were generated at calculated positions (dC-H=0.97 A)
and treated as riding atoms with isotropic thermal factors.
Acknowledgment. This work was supported by
Grants-in-Aid for Scientific Research for Young Scien-
tists (S) (No. 19675002) and for Scientific Research on
Priority Areas (No. 18066003) from the Ministry of
Education, Culture, Sports, Science and Technology of
Japan. Y.N. thanks the Tonen General Sekiyu Founda-
tion for the Promotion of Science, Technology, the
Mazda Science and Technology Foundation, and the
Iwatani Naoji Foundation.
˚
(21) SIR97: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.
C.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. J. Appl. Crystallogr. 1999, 32, 115.
(22) DIRDIF99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The
DIRDIF-99 program system, Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1999.
(23) Carruthers, J. R.; Rollett, J. S.; Betteridge, P. W.; Kinna, D.;
Pearce, L.; Larsen, A.; Gabe, E. CRYSTALS Issue 11; Chemical Crystal-
lography Laboratory, Oxford, U.K., 1999.
Supporting Information Available: CIF files giving crystal-
lographic data for 1, trans-[W(N2)2(depf)(PPh2Me)2], and 7.
This material is available free of charge via the Internet at http://
pubs.acs.org.
(24) CrystalStructure 3.8: Crystal Structure Analysis Package; Riga-
ku and Rigaku Americas, 2000-2007.