From amine to ruthenaziridine to azaallyl: Unusual transformation of di-(2-pyridylmethyl)amine on ruthenium

Article abstract of DOI:10.1039/c1dt10626k

The complexation of di-(2-pyridylmethyl)amine to RuHCl(PPh ₃)₃ affords the salt [RuH{κ³N-fac-1,3-di- (2-pyridylmethyl)amine}(PPh₃)₂]Cl. Reaction with potassium tert-butoxide at room temperature yields the unusual ruthenaziridine complex RuH{κ³C^alkNN^py-1,3-di-(2-pyridylmethyl) amine}(PPh₃)₂, where the central nitrogen atom, adjacent alkyl carbon, and pyridine arm coordinate to the metal, leaving the second pyridine arm uncoordinated. Surprisingly, heating of this ruthenaziridine complex with concomitant H₂ formation affords the ruthenium azaallyl complex RuH(κ³N-1,3-di-(2-pyridyl)-2-azaallyl)(PPh ₃)₂. This is a rare example of a 4d metal complex containing the azaallyl ligand. X-Ray crystal structures and NMR characterization of all three compounds are presented herein.

Full text of DOI:10.1039/c1dt10626k

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PAPER
From amine to ruthenaziridine to azaallyl: unusual transformation of
di-(2-pyridylmethyl)amine on ruthenium†
Demyan E. Prokopchuk, Alan J. Lough and Robert H. Morris*
Received 12th April 2011, Accepted 10th June 2011
DOI: 10.1039/c1dt10626k
3
The complexation of di-(2-pyridylmethyl)amine to RuHCl(PPh3)3 affords the salt [RuH{k N-fac-
1,3-di-(2-pyridylmethyl)amine}(PPh3)2]Cl. Reaction with potassium tert-butoxide at room temperature
3
yields the unusual ruthenaziridine complex RuH{k CalkNNpy-1,3-di-(2-pyridylmethyl)amine}(PPh3)2,
where the central nitrogen atom, adjacent alkyl carbon, and pyridine arm coordinate to the metal,
leaving the second pyridine arm uncoordinated. Surprisingly, heating of this ruthenaziridine complex
3
with concomitant H2 formation affords the ruthenium azaallyl complex RuH(k N-1,3-di-(2-pyridyl)-
2-azaallyl)(PPh3)2. This is a rare example of a 4d metal complex containing the azaallyl ligand. X-Ray
crystal structures and NMR characterization of all three compounds are presented herein.
starting point, we chose to use the parent compound di-(2-
pyridylmethyl)amine, which contains two pendant methylpyridine
“arms” and a central secondary amine donor. It is easily synthe-
sized in high yields44 and is cost-effective, both desirable properties
of any ligand system. There are only a few reports of ruthenium
compounds containing this ligand.45–49 We decided to investigate
its reactivity with the common ruthenium hydride precursor
RuHCl(PPh3)3 rationalizing that a combination of a secondary
amine proton and metal hydride may offer a promising metal–
ligand bifunctional system for catalytic transformations, such as
H2 hydrogenation and/or transfer hydrogenation.13,14,18,20,22–25,50–55
1
Introduction
Tridentate ligands containing mixed nitrogen and phosphorus
donors have recently received much attention, affording tunable
and robust ligand systems for late transition metals.1–7 For exam-
ple, the highly reactive five-coordinate Ru–PNP complex A, which
8
contains a central secondary nitrogen, reversibly reacts with H2
and is a highly active ammonia–borane dehydrogenation catalyst
(Scheme 1).9 Moreover, Ru–PNN complex B which contains a
central pyridine ring that is dearomatized also reversibly reacts
with H2.7 It efficiently catalyzes the formation of alcohols into
esters10 and splits water into H2 and O2.11 Ruthenium compounds
with tridentate PNP and PNN ligands have also been utilized
in the catalytic reduction of ketones.12–15 The tridentate ligand in
these examples is thought to assist in the activation of substrates
during bifunctional catalysis.16–25
2
Results and discussion
2.1 Synthesis of ruthenium di-(2-pyridylmethyl)amine and
ruthenaziridine complexes
Our investigations began by reacting RuHCl(PPh3)3 with di-(2-
pyridylmethyl)amine, expecting that removal of two phosphines
would lead to coordination of the tridentate ligand. However,
stirring for several minutes in tetrahydrofuran (THF) afforded the
3
salt [RuH{k N-fac-1,3-di-(2-pyridylmethyl)amine}(PPh3)2]Cl (1)
in excellent yield (Scheme 2). Complex 1 is freely soluble in protic
solvents and was fully characterized by NMR studies in methanol-
d4. This product resulted from the displacement of the chloride an-
ion and removal of only one phosphine. The 1H NMR shows that
the NH proton on the di-(2-pyridylmethyl)amine ligand is shifted
Scheme 1 Examples of ruthenium-based PNP and PNN systems.
Some iron-group complexes containing tridentate nitrogen
donor ligands (NNN) have been examined for use in catalysis.26–40
For example, iron complexes of amine-functionalized di-(2-
pyridylmethyl)amines have been intensely studied as analogues
of active sites of iron-containing oxidases.41–43 As a simpler
Department of Chemistry, University of Toronto, 80 St. George Street,
Toronto, ON, M5S3H6, Canada. E-mail: rmorris@chem.utoronto.ca
† CCDC reference numbers 821591–821593. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c1dt10626k
Scheme 2 Synthesis of complex 1.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10603–10608 | 10603
©

◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for complexes 1, 2,
and 3
significantly downfield (6.2 ppm) compared to the methylene
protons (3.8–3.6 ppm). The hydride resonance appears at -14.7
ppm as a triplet (2JHP = 29 Hz), given the Cs symmetry of the cation.
An X-ray crystal structure of complex 1 was also obtained
(Fig. 1, Table 1 and Table 2). In the solid state, 1 adopts a
distorted octahedral geometry with the chloride counteranion
hydrogen bonded to the amine proton. The bite angles between
the central nitrogen atom and pendant pyridine arms are 77.4(2)◦
and 83.7(2)◦ for the N1–Ru–N2 and N1–Ru–N3 angles, re-
spectively (Table 1). This is complemented by the larger angle
of 95.70(7)◦ between the phosphine ligands. The Ru–N2 bond
is longer for 1 than in the related complexes trans,fac-[Ru{di-
(2-pyridylmethyl)amine)}(CO)2Cl][PF6] and cis,fac-[Ru{di-(2-
pyridylmethyl)amine}(CO)2(MeCN)][PF6]2 due to the presence of
a hydride trans- to the central nitrogen atom.46
Parameter
1
2
3
Ru–H1
Ru–N1
Ru–N2
Ru–N3
1.74(7)
2.128(6)
2.234(5)
2.111(6)
—
1.63(3)
2.175(3)
2.131(3)
—
2.121(3)
2.244(1)
2.276(1)
1.463(5)
1.452(4)
76.7(1)
—
1.61(3)
2.107(3)
2.055(2)
2.113(2)
—
Ru–C7
Ru–P1
Ru–P2
N2–C6
N2–C7
N1–Ru–N2
N1–Ru–N3
N2–Ru–N3
P1–Ru–P2
P2–Ru–N1
P1–Ru–N3
2.293(2)
2.284(2)
1.492(8)
1.487(8)
77.4(2)
83.7(2)
77.0(2)
95.70(7)
172.1(2)
172.6(2)
2.3002(7)
2.3081(7)
1.335(4)
1.334(4)
78.8(1)
157.1(1)
78.5(1)
157.96(3)
88.24(7)
90.84(7)
—
103.37(4)
94.39(7)
—
IR analysis reveals an NH stretching mode at 3271 cm-1. Based
on complete 1D/2D NMR spectral characterization and a crystal
3
structure, we determined the compound to be RuH{k CalkNNpy-
1,3-di-(2-pyridylmethyl)amine}(PPh3)2 which contains an anionic
ruthenaziridine moiety and a decoordinated pyridine ring. (2,
Scheme 3, Fig. 2, Table 1 and Table 2). The methine hydrogen
of the alkyl in complex 2 appears at 3.1 ppm.
Scheme 3 Synthesis of 2.
Fig. 1 Molecular structure of 1 depicted with thermal ellipsoids at
the 30% probability level. Hydrogen atoms on the aromatic rings and
methylene carbons have been omitted for clarity.
When 1 was reacted with one equivalent of potassium tert-
butoxide, we expected rapid and selective deprotonation of the
central nitrogen atom at room temperature to afford RuH{fac-1,3-
di-(2-pyridylmethyl)amide}(PPh3)2. However, when monitoring
the course of the reaction by NMR spectroscopy, we observed
a complex mixture of products as indicated by multiple metal
hydride, ligand, and phosphorus signals. The mixture was allowed
to stir for 24 h at room temperature and these coalesced into one
major product. The 1H NMR spectrum of this product contained
a hydride signal coupled to two inequivalent cis-phosphines
2
(-15.8 ppm, JHP = 29 and 25 Hz). When trying to assign the
proton signals in the 1H NMR spectrum, we noticed that one of
the protons on the CNC backbone of the ligand, appearing as a
broad multiplet, was shifted far downfield (at 5.1 ppm) compared
to three other protons, which have well-resolved couplings (at 3.5–
3.1 ppm). This is reminiscent of the NH proton in 1, which was
also far downfield with respect to the methylene protons. Indeed,
Fig. 2 Molecular structure of 2 depicted with thermal ellipsoids at the
30% probability level. Hydrogen atoms on the aromatic rings have been
omitted for clarity.
10604 | Dalton Trans., 2011, 40, 10603–10608
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The Royal Society of Chemistry 2011
©

Table 2 X-Ray crystal structure and refinement data for complexes 1, 2, and 3
Compounds
1
2
3
Empirical formula
Formula mass
T/K
C48H44ClN3P2Ru
861.32
150(1)
C48H43N3P2Ru
824.86
150(1)
C48H41N3P2Ru
822.85
150(1)
˚
Wavelength (A)
0.71073
0.71073
0.71073
Crystal system
Monoclinic
P21/n
Monoclinic
P21/c
21.076(4)
9.289(2)
20.185(4)
90
93.48(3)
90
3944(1)
4
1.389
0.517
1704
0.18 ¥ 0.08 ¥ 0.04
2.58–27.47
38699
Triclinic
P1
11.5061(3)
11.7305(3)
16.1489(3)
88.632(1)
78.804(1)
83.233(1)
2123.28(9)
2
1.287
0.480
848
0.30 ¥ 0.13 ¥ 0.03
2.57–25.12
15884
¯
Space group
˚
a/A
11.0768(3)
33.850(1)
12.4059(2)
90
91.673(2)
90
4649.6(2)
4
1.230
0.497
1776
0.20 ¥ 0.20 ¥ 0.15
2.57–25.00
29446
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
Volume/A
Z
Density (calculated/g cm-3)
Absorption coefficient (mm-1)
F(000)
Crystal Size/mm
Theta range for data collection (◦)
Reflections collected
Independent reflections
Completeness to q = 25.00◦ (%)
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2s(I)]
R indices (all data)
8097 [R(int) = 0.115]
9006 [R(int) = 0.0761]
7369 [R(int) = 0.082]
99.0
99.8
97.2
Multi-scan
0.930, 0.731
Full-matrix least-squares on F2
8097/0/471
0.930
R1 = 0.0730
wR2 = 0.2182
Multi-scan
0.982, 0.899
Full-matrix least-squares on F2
9006/1/496
1.020
R1 = 0.0509
wR2 = 0.1308
Multi-scan
0.988, 0.585
Full-matrix least-squares on F2
7369/0/491
1.069
R1 = 0.0407
wR2 = 0.1128
Crystals of 2 were obtained via diffusion of pentane into a
concentrated solution of benzene. Selected bond lengths and
angles are given in Table 1. The complex is severely distorted
from an ideal octahedron with large P1–Ru–C7 and P2–Ru–N2
angles of 103.5(1)◦ and 113.19(8)◦, respectively, and a very acute
N2–Ru–C7 angle of 39.9(1)◦. The hydride ligand is trans- to the
coordinated pyridine arm. The N2–C7 bond length is 1.452(4)
Scheme 4 Summary of the reactivity of complexes 1 and 2.
3
˚
A, which is indicative of an sp -hybridized carbon atom and is
comparable with the slightly longer N2–C7 distance of 1.487(8)
˚
Selected metrical parameters for 3 are presented in Table 1. The
A in 1. The only other two other crystallographically defined
bite angle between the pyridine nitrogens is 157.96(3)◦, while the
compounds that contain the ruthenaziridine motif are prepared by
reacting the carbonyl cluster Ru3(CO)12 with 1,4-diazabutadienes
(a-diimines).56,57 The products in these cases were dimers while
2 remains monomeric, possibly due to the steric bulk of the
phosphines.
˚
central Ru–N bond is slightly shorter (Ru–N2 = 2.055(2) A) than
the pyridine Ru–N bonds (Ru–N1 = 2.107(3), Ru–N3 = 2.113(2)
˚
˚
A). The azaallyl N–C bonds are identical (N2–C6 = 1.335(4) A,
˚
N2–C7 = 1.334(4) A), which suggests delocalization of negative
charge about all three atoms. These bond lengths and angles are
similar to a previously reported iron 1,3-di-(2-pyridyl)-2-azallyl
complex.60
2.2 Synthesis of a ruthenium azaallyl complex
In the preparation of complex 2 by reaction of base with
The symmetrical structure of 3 explains the triplet pattern of the
hydride resonance in the 1H NMR spectrum and the singlet phos-
phorus peak. Not only was the central amine proton removed from
di-(2-pyridylmethyl)amine, but a proton and hydride equivalent
were also eliminated to form the tridentate anionic azaallyl ligand.
The trans- arrangement of the PPh3 ligands suggests that some
ligand rearrangement must have occurred during the formation of
3, possibly involving phosphine or pyridine arm dissociation.
Initially discovered as a degradation product attached to zinc,59
the azaallyl ligand has attracted attention more recently due to
the intense colours it imparts on a variety of 3d metal precursors.
Wolczanski and co-workers have synthesized similar complexes by
reacting the lithium dipyridylazaallyl salt with a variety of metals
complex
solid also forms in low yield as a by-product. Its pres-
ence is signalled by a hydride triplet at -8.6 ppm (2JHP
1 at room temperature, a deep emerald green
=
29 Hz) in crude samples of 2. When ruthenium salt 1 is heated in
THF with potassium tert-butoxide, an intensely coloured emerald
green solution formed, which we thought to be (RuH{fac-1,3-di-
(pyridylmethyl)amide}(PPh3)2). The NMR spectrum showed that
2 was replaced by a highly symmetrical molecule containing a
triplet at -8.6 ppm (2JHP = 29 Hz) and a singlet phosphorus peak
(proton decoupled) at 50.9 ppm appeared. Surprisingly, it was
identified by use of single crystal X-ray diffraction to be a rare
azaallyl complex58–62 with trans-PPh3 ligands (Scheme 4, Fig. 3).
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The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10603–10608 | 10605
©

binds as a neutral tridentate ligand. Upon addition of base, one of
the alkyl carbons becomes an anionic two-electron donor and an
unusual ruthenaziridine complex (2) is formed. Finally, refluxing
1 with base or 2 without base leads to the novel ruthenium
hydrido azaallyl complex 3 with concomitant H2 production. This
deprotonation/dehydrogenation reaction pathway is unusual, and
mechanistic studies are currently under way.
4
Experimental
4.1 General comments
All experiments were carried out under argon using standard
Schlenk and glove box techniques. Tetrahydrofuran (THF) was
distilled over Na/benzophenone prior to use. RuHCl(PPh3)3
was prepared according to a known literature procedure.65 Di-
(2-pyridylmethyl)amine, sublimed potassium tert-butoxide, and
methanol-d4 (ampules) were used as received (Aldrich). Air
and moisture free benzene-d6 was prepared by stirring with
Na/benzophenone for 2 days, followed by three freeze–pump–
thaw cycles and vacuum transfer. All NMR spectroscopic data
were collected using a Varian 400 MHz or a Bruker 400 MHz
NMR system operating at 400 MHz for 1H, 101 MHz for 13C, or
162 MHz for 31P. All 1H and 13C NMR samples were referenced to
Fig. 3 Molecular structure of 3 depicted with thermal ellipsoids at the
30% probability level. Hydrogen atoms on the phenyl rings have been
omitted for clarity.
(Scheme 5).60,63 These molecules have two intraligand transitions60
in the visible region with extinction coefficients ranging from
20000–50000 M-1cm-1. Azaallyl compound 3 also has two intrali-
gand UV-vis absorption bands, with broad absorbances centered
at 697 nm (e = 8500 M-1cm-1) and 405 nm (e = 32000 M-1cm-1).
their respective residual solvent peaks. Spectroscopic data for 31
P
NMR were referenced to an external standard of 85% aqueous
H3PO4 at d = 0.00. Single-crystal X-ray diffraction data were
collected at 150 K using a Nonius Kappa-CCD diffractometer
˚
with Mo-Ka radiation (l = 0.71073 A). The CCD data were
integrated and scaled using the Denzo-SMN package.66 The
structures were solved and refined using SHELXTL V6.1.67
Refinement was by full-matrix least-squares on F2 using all data.
All IR spectra were prepared as KBr pellets and carried out on
a Perkin-Elmer Spectrum One FT-IR spectrometer. All UV-vis
spectra were recorded on a Hewlett-Packard Agilent 8453 UV-
vis spectrophotometer. Elemental Analyses were performed on
a Perkin–Elmer 2400 CHN elemental analyzer. For compounds
2 and 3 elemental analyses were attempted several times and
consistently produced low carbon percentages despite being pure
by all other spectroscopic means.
Scheme 5 Azaallyl complexes prepared by Wolczanski and co-workers.
There is a minor by-product that forms with 3 which contains
a hydride triplet 0.1 ppm upfield and a phosphorus singlet 2 ppm
downfield from the signals in 3, respectively. We were unable
to identify or isolate this electronically similar product, but its
presence can be minimized if two equivalents of base are used to
synthesize complex 3 instead of one.64
The azaallyl complex 3 can also be synthesized directly from 2
by refluxing in THF with no added base (Scheme 4). This shows
that 2 is indeed a reaction intermediate. However, the azaallyl
complex 3 can be synthesized in higher yields and greater purity
if two equivalents of base are used when starting from 1 (vide
supra). Interestingly, the amine proton and hydride of 2 are cis- to
one another in the solid state (Fig. 2), which suggests that H2 loss
occurs in a bifunctional manner.54
4.2 Synthesis
4.2.1 [RuH{j3N-fac-1,3-di-(2-pyridylmethyl)amine}(PPh3)2]-
Cl (1). A suspension of RuHCl(PPh3)3 (1.00 g, 1.08 mmol) in
THF (15 mL) was placed in a glass vial charged with a teflon-
coated stir bar. Di-(2-pyridylmethyl)amine (237 mg, 1.19 mmol)
was added and after 10 min of stirring the solution became cloudy
yellow. This was immediately filtered over a medium-pore glass frit
and washed with THF (2 ¥ 1 mL). The yellow precipitate on the
frit was washed through with methanol (10 mL) and the yellow
filtrate was collected. Excess solvent was removed in vacuo to afford
a bright yellow microcrystalline solid (857 mg, 92%). Crystals
suitable for X-ray diffraction were grown via slow diffusion of
diethyl ether into a concentrated methanol solution at 25 ◦C. EA:
found C 66.4, H 5.3, N 4.9. Calc. for C48H44N3P2ClRu: C 66.9, H
5.15, N 4.9%. UV-vis: lmax(CH3CN)/nm 345 (e/M-1cm-1 14000).
3
Conclusion
We have shown that
a simple ligand precursor, di-(2-
pyridylmethyl)amine, can be manipulated into adopting three
3
1
different coordination modes. Firstly, the salt [RuH{k N-fac-
IR: nmax/cm-1 3273 w (NH), 1956 s (RuH). H NMR (CD3OD):
1,3-di-(2-pyridylmethyl)amine}(PPh3)2]Cl is synthesized where it
10606 | Dalton Trans., 2011, 40, 10603–10608
d 8.67 (2H, d, 3J = 6 Hz, 6-pyH), 7.33–7.23 (14H, m, 4-pyH and
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The Royal Society of Chemistry 2011
©

C6H5), 7.09 (6H, m, C6H5), 6.95 (12H, m, C6H5), 6.89 (2H, d,
3J = 8 Hz, 3-pyH), 6.61 (2H, m, 5-pyH), 6.16 (1H, m, NH), 3.83
(2H, d, 2J = 16 Hz, CH2), 3.64 (2H, dd, 2J = 16 Hz, CH2), -14.66
6-pyH), 6.38 (2H, s, CHazaallyl), 6.25 (2H, m, 4-pyH), 5.88 (2H,
2
2
d, J = 7 Hz, 3-pyH), 5.16 (2H, m, 5-pyH), -8.59 (1H, t, JHP
=
1
29 Hz, RuH). 13C { H} NMR: d 166.89 (2-pyC), 156.53 (6-pyC),
2
1
(1H, t, JHP = 29 Hz, RuH). 13C { H} NMR: d 161.55 (2-pyC),
156.61 (6-pyC), 138–139 (C6H5), 137.24 (4-pyC), 135.09 (C6H5),
129.76 (C6H5), 128.56 (C6H5), 124.88 (3-pyC), 122.89 (5-pyC),
137.07 (C6H5), 134.56 (C6H5), 128.75–128.00 (C6H5 buried under
1
solvent), 115.58 (Cazaallyl), 113.82 (5-pyC), 113.67 (3-pyC). 31P { H}
NMR: d 50.94 (s, RuP). MS (DART): found: m/z 822.2. Calc. for
1
63.06 (CH2). 31P { H} NMR: d 67.40 (s, RuP). MS (ESI): found:
[C48H40N3P2Ru]+ (loss of H-): 822.2.
m/z 826.1961. Calc. for [C48H44N3P2Ru]+ 826.2048.
4.2.2 RuH{j3CalkNNpy - 1,3 - di - (2 - pyridylmethyl )amine}-
(PPh3)2 (2). A suspension of 1 (28 mg, 0.033 mmol) in tetrahy-
drofuran (2 mL) was placed in a glass vial charged with a teflon-
coated stir bar. Potassium tert-butoxide (4 mg, 0.033 mmol, 0.085
M in THF) was added (excess base is not detrimental). The
solution darkened immediately after addition of base and was
stirred for 24 h at room temperature, during which the colour
changed to green–brown. This green–brown solution was filtered
through a pad of Celite, dried in vacuo, then redissolved in hexanes
(3 mL) and stirred overnight. Finally, the solution was filtered
over a medium-pore glass frit and the solid was washed with
hexanes (about 3 mL) until the outgoing filtrate was colourless.
The remaining solid was dried in vacuo to afford a yellow–brown
powder (14 mg, 52%). Crystals suitable for X-ray diffraction
were grown via slow diffusion of pentane into a concentrated
benzene solution at 25 ◦C. EA: found: 63.7, 5.1, 4.9. Calc. for
C48H43N3P2Ru: C 69.9, H 5.25, N 5.1%. IR: nmax/cm-1 3271 w
(NH), 1953 s (RuH). 1H NMR (C6D6, coord = coordinated,
uncoord = uncoordinated): d 8.50 (1H, d, 2J = 5 Hz, 6-pyHuncoord ),
Acknowledgements
We thank the Natural Sciences and Engineering Research Council
(NSERC) for a Discovery Grant to R.H.M. D.E.P. would like to
thank NSERC and the Ontario Graduate Studies in Science and
Technology (OGSST) scholarships for graduate funding.
References
1 J. van der Vlugt and J. Reek, Angew. Chem., Int. Ed., 2009, 48, 8832–
8846.
2 D. Benito-Garagorri and K. Kirchner, Acc. Chem. Res., 2008, 41, 201–
213.
3 L.-C. Liang, Coord. Chem. Rev., 2006, 250, 1152–1177.
4 N. Tsvetkov, H. Fan and K. G. Caulton, Dalton Trans., 2011, 40, 1105–
1110.
5 A. Friedrich, M. Drees, M. Ka¨b, E. Herdtweck and S. Schneider, Inorg.
Chem., 2010, 49, 5482–5494.
6 M. D. Fryzuk, P. A. MacNeil and S. J. Rettig, Organometallics, 1985,
4, 1145–1147.
7 D. Milstein, Top. Catal., 2010, 53, 915–923.
8 A. Friedrich, M. Drees, J. Schmedt, auf der Gu¨nne and S. Schneider,
J. Am. Chem. Soc., 2009, 131, 17552–17553.
9 M. Ka¨b, A. Friedrich, M. Drees and S. Schneider, Angew. Chem., Int.
Ed., 2009, 48, 905–907.
10 J. Zhang, G. Leitus, Y. Ben-David and D. Milstein, J. Am. Chem. Soc.,
2005, 127, 10840–10841.
11 S. W. Kohl, L. Weiner, L. Schwartsburd, L. Konstantinovski, L. J. W.
Shimon, Y. Ben-David, M. A. Iron and D. Milstein, Science, 2009, 324,
74–77.
2
7.80 (1H, d, J = 5 Hz, 6-pyHcoord ), 7.55 (12H, m, C6H5), 7.02–
6.94 (18H, m, C6H5), 6.87 (1H, m, 4-pyHuncoord ), 6.58 (1H, m,
2
5-pyHuncoord ), 6.56 (1H, m, 4-pyHcoord ), 6.11 (1H, d, J = 7 Hz,
2
3-pyHcoord ), 5.94 (1H, d, J = 7 Hz, 3-pyHuncoord ), 5.86 (1H, m, 5-
2
pyHcoord ), 5.10 (1H, m, NH), 3.42 (1H, dd, J = 16 Hz, CH2),
2
3.26 (1H, dd, J = 16 Hz, CH2), 3.11 (1H, m, CHNH), -15.81
2
2
1
(1H, dd, JHP = 29 Hz, JHP = 25 Hz, RuH). 13C { H} NMR:
d 169.65 (2-pyCuncoord ), 158.52 (2-pyCcoord ), 154.41 (6-pyCcoord ),
149.26 (6-pyCuncoord ), 143.86–142.71 (C6H5), 134.91 (4-pyCuncoord ),
134.64-133.86 (C6H5), 131.57 (4-pyCcoord ), 127.84 (C6H5), 121.97
(5-pyCcoord ), 120.56 (3-pyCcoord ), 119.13 (3-pyCuncoord ), 116.27 (5-
12 A. Del Zotto, W. Baratta, M. Ballico, E. Herdtweck and P. Rigo,
Organometallics, 2007, 26, 5636–5642.
13 M. L. Clarke, M. B. D´ıaz-Valenzuela and A. M. Z. Slawin,
Organometallics, 2007, 26, 16–19.
14 M. D´ıaz-Valenzuela, S. Phillips, M. France, M. Gunn and M. Clarke,
Chem.–Eur. J., 2009, 15, 1227–1232.
15 S. Phillips, J. Fuentes and M. Clarke, Chem.–Eur. J., 2010, 16, 8002–
8005.
pyCuncoord ), 59.54 (CHNH), 56.10 (CH2). 31P { H} NMR: d 77.39
1
(m, RuP), 61.73 (m, RuP). MS (DART): found: m/z 824.2. Calc.
16 M. Yamakawa, H. Ito and R. Noyori, J. Am. Chem. Soc., 2000, 122,
for [C48H40N3P2Ru]+ (loss of H-): 824.2.
1466–1478.
17 R. Noyori and T. Ohkuma, Angew. Chem., Int. Ed., 2001, 40, 40–73.
18 S. E. Clapham, A. Hadzovic and R. H. Morris, Coord. Chem. Rev.,
2004, 248, 2201–2237.
4.2.3 RuH(j3N-1,3-di-(2-pyridyl)-2-azaallyl)(PPh3)2 (3).
A
suspension of 1 (28 mg, 0.033 mmol) in THF (2 mL) was placed
in a Schlenk flask charged with a teflon-coated stir bar. Potassium
tert-butoxide (8 mg, 0.067 mmol, 0.085 M in THF) was added.
The solution turned dark immediately after addition of base and
was heated at 60 ◦C overnight. The resulting deep emerald green
solution was filtered through Celite and dried in vacuo. Pentane
was added (1 mL), the solution was stirred for 1 h, then filtered
over a medium-pore glass frit (the product is soluble in pentane
so it must be used sparingly). Solvent was removed in vacuo to
afford a dark green powder (20 mg 75%). Crystals suitable for
X-ray diffraction were grown via slow diffusion of pentanes into
a concentrated ethereal solution at -30 ◦C. EA: found: C 68.0,
H 5.2, N 5.1. Calc. for C48H41N3P2Ru: C 70.1, H 5.0, N 5.1%.
19 T. Ikariya, K. Murata and R. Noyori, Org. Biomol. Chem., 2006, 4,
393–406.
20 M. Ito and T. Ikariya, Chem. Commun., 2007, 5134–5142.
21 T. Ikariya and A. J. Blacker, Acc. Chem. Res., 2007, 40, 1300–1308.
22 S. Kuwata and T. Ikariya, Dalton Trans., 2010, 39, 2984–2992.
23 T. Ikariya and I. Gridnev, Top. Catal., 2010, 53, 894–901.
24 D. Grotjahn, Top. Catal., 2010, 53, 1009–1014.
25 T. Ikariya, Bull. Chem. Soc. Jpn., 2011, 84, 1–16.
26 T. E. Chavez-Gil, M. Yasaka, T. Senokuchi, M. Sumimoto, H. Kurosaki
and M. Goto, Chem. Commun., 2001, 2388–2389.
27 H. Nishiyama and A. Furuta, Chem. Commun., 2007, 760–762.
28 T. Inagaki, L. Phong, A. Furuta, J.-i Ito and H. Nishiyama, Chem.–Eur.
J., 2010, 16, 3090–3096.
29 A. Poater, J. Mola, A. G. Saliner, I. Romero, M. Rodriguez, A. Llobet
and M. Sola, Chem. Phys. Lett., 2008, 458, 200–204.
30 G. J. P. Britovsek, J. England, S. K. Spitzmesser, A. J. P. White and D.
J. Williams, Dalton Trans., 2005, 945–955.
31 Q. Knijnenburg, S. Gambarotta and P. H. M. Budzelaar, Dalton Trans.,
2006, 5442–5448.
UV-vis: lmax(C6H6)/nm 697 (e/M-1cm-1 8500), 405 (32000). IR:
1
n
max/cm-1 1818 m (RuH). H NMR (C6D6): d 7.87–7.83 (12H,
2
m, C6H5), 7.07–6.99 (18H, m, C6H5), 6.39 (2H, d, J = 6 Hz,
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10603–10608 | 10607
©

32 G. J. P. Britovsek, V. C. Gibson, O. D. Hoarau, S. K. Spitzmesser, A. J.
P. White and D. J. Williams, Inorg. Chem., 2003, 42, 3454–3465.
33 R. A. T. M. Abbenhuis, I. del R´ıo, M. M. Bergshoef, J. Boersma, N.
Veldman, A. L. Spek and G. van Koten, Inorg. Chem., 1998, 37, 1749–
1758.
52 C. Hedberg, K. Ka¨llstro¨m, P. I. Arvidsson, P. Brandt and
P. G. Andersson, J. Am. Chem. Soc., 2005, 127, 15083–
15090.
53 K. Abdur-Rashid, M. Faatz, A. J. Lough and R. H. Morris, J. Am.
Chem. Soc., 2001, 123, 7473–7474.
34 H. Mishra, A. K. Patra and R. Mukherjee, Inorg. Chim. Acta, 2009,
54 K. Abdur-Rashid, S. E. Clapham, A. Hadzovic, J. N. Harvey, A.
J. Lough and R. H. Morris, J. Am. Chem. Soc., 2002, 124, 15104–
15118.
362, 483–490.
35 O. Dayan and B. Cetinkaya, J. Mol. Catal. A: Chem., 2007, 271, 134–
141.
55 M. Zimmer-De Iuliis and R. H. Morris, J. Am. Chem. Soc., 2009, 131,
36 B. L. Small and M. Brookhart, Macromolecules, 1999, 32, 2120–2130.
37 S. Bhor, G. Anilkumar, M. K. Tse, M. Klawonn, C. Do¨bler, B. Bitterlich,
A. Grotevendt and M. Beller, Org. Lett., 2005, 7, 3393–3396.
38 F. A. R. Kaul, G. T. Puchta, G. D. Frey, E. Herdtweck and W. A.
Herrmann, Organometallics, 2007, 26, 988–999.
39 S. Fukui, N. Suzuki, T. Wada, K. Tanaka and H. Nagao,
Organometallics, 2010, 29, 1534–1536.
40 R. K. O’Reilly, V. C. Gibson, A. J. White and D. J. Williams, Polyhedron,
2004, 23, 2921–2928.
41 M. K. Panda, A. John, M. M. Shaikh and P. Ghosh, Inorg. Chem.,
2008, 47, 11847–11856.
11263–11269.
56 L. H. Staal, L. H. Polm, R. W. Balk, G. Van Koten, K. Vrieze and A.
M. F. Brouwers, Inorg. Chem., 1980, 19, 3343–3351.
57 L. H. Polm, C. J. Elsevier, G. Van Koten, J. M. Ernsting, D. J. Stufkens,
K. Vrieze, R. R. Andrea and C. H. Stam, Organometallics, 1987, 6,
1096–1104.
58 B. A. Frazier, P. T. Wolczanski and E. B. Lobkovsky, Inorg. Chem.,
2009, 48, 11576–11585.
59 M. Westerhausen and A. N. Kneifel, Inorg. Chem. Commun., 2004, 7,
763–766.
60 B. A. Frazier, P. T. Wolczanski, E. B. Lobkovsky and T. R. Cundari, J.
42 M. G. G. Fuchs, S. Dechert, S. Demeshko, U. Ryde and F. Meyer, Inorg.
Chem., 2010, 49, 5853–5858.
43 K. Visvaganesan, R. Mayilmurugan, E. Suresh and M. Palaniandavar,
Inorg. Chem., 2007, 46, 10294–10306.
Am. Chem. Soc., 2009, 131, 3428–3429.
61 A. Malassa, C. Agthe, H. Go¨rls, M. Friedrich and M. Westerhausen,
J. Organomet. Chem., 2010, 695, 1641–1650.
62 E. C. Volpe, P. T. Wolczanski and E. B. Lobkovsky, Organometallics,
2010, 29, 364–377.
63 P. T. Wolczanski and B. A. Frazier, U.S. Pat. Appl. Publ., US
20100204473, CAN 153 : 302632, 2010.
64 The electronically similar product may be a dimer. Wolczanski and co-
workers found that one of their monomeric iron(II) azaallyl complexes
was in equilibrium with a dimerized product connected through the
azaallyl carbons. See reference 60.
44 D. W. Gruenwedel, Inorg. Chem., 1968, 7, 495–501.
45 S. K. Sahni, M. G. B. Drew, T. W. Bell and B. S. Brunschwig, J. Chem.
Soc., Chem. Commun., 1993, 123–125.
46 D. H. Gibson, J. Wu and M. S. Mashuta, Inorg. Chim. Acta, 2006, 359,
309–319.
47 A. Soliman, M. Khattab and R. Ramadan, Transition Met. Chem.,
2007, 32, 325–331.
48 M. Omar, J. Therm. Anal. Calorim., 2009, 96, 607–615.
49 A. Yogi, J.-H. Oh, T. Nishioka, R. Tanaka, E. Asato, I. Kinoshita and
S. Takara, Polyhedron, 2010, 29, 1508–1514.
50 K. Abdur-Rashid, R. Abbel, A. Hadzovic, A. J. Lough and R. H.
Morris, Inorg. Chem., 2005, 44, 2483–2492.
51 F. N. Haque, A. J. Lough and R. H. Morris, Inorg. Chim. Acta, 2008,
361, 3149–3158.
65 P. S. Hallman, B. R. McGarvey and G. Wilkinson, J. Chem. Soc. A,
1968, 3143–3150.
66 Z. Otwinowski and W. Minor, in Macromolecular Crystallography Part
A, ed. J. Charles and W. Carter, Academic Press, 1997, vol. 276, pp.
307–326.
67 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
64, 112–122.
10608 | Dalton Trans., 2011, 40, 10603–10608
This journal is
The Royal Society of Chemistry 2011
©