Reactivity of the oxime/oximato group in ruthenium(II) complexes

Article abstract of DOI:10.1021/ic8009699

Oxime targeted reactions of the complexes trans-[(κ³- dapdOH)Ru(CO)(PPh₃)₂]PF₆ (1) (dapdOH = diacetylpyridinedioxime) and trans-[(κ³-dapmOH)RuCl(PPh ₃)₂]PF₆ (2) (dapmO

Full text of DOI:10.1021/ic8009699

Inorg. Chem. 2008, 47, 11942-11949
Reactivity of the Oxime/Oximato Group in Ruthenium(II) Complexes
Sanjay Kumar Singh,† Sanjeev Sharma,† Sudhakar Dhar Dwivedi,† Ru-Qiang Zou,‡ Qiang Xu,‡
and Daya Shankar Pandey*,†
Department of Chemistry, Faculty of Science, Banaras Hindu UniVersity,
Varanasi - 221 005 U.P., India, and National Institute of AdVanced Industrial Science and
Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
Received May 29, 2008
Oxime targeted reactions of the complexes trans-[(κ3-dapdOH)Ru(CO)(PPh3)2]PF6 (1) (dapdOH ) diacetylpy-
ridinedioxime) and trans-[(κ3-dapmOH)RuCl(PPh3)2]PF6 (2) (dapmOH ) diacetylpyridinemonooxime) with SOCl2,
NaBH4, or HCHO led into conversion of oxime to oximato, imino, or hydroxymethylimino groups. The reaction
products have been characterized by analytical and spectral studies. Molecular structures of the representative
homo/heteroleptic oxime/oximato complexes trans-[(κ3-dapdOH)Ru(CO)(PPh3)2]PF6 (1), trans-[(κ3-dapdO)Ru-
(CO)(PPh3)2] (11) and oximato/imino complex trans-[(κ3-dapd-NH)Ru(CO)(PPh3)2]PF6 (13) have been authenticated
by single-crystal X-ray diffraction analyses. Structural studies revealed the presence of various oxime/oximato/
imino based O-H· · ·O, C-H · · · O, and N-H · · · F interactions in the complexes 1, 11, and 13.
Introduction
nitrogen or oxygen atoms.3 It may coordinate with one metal
ion through nitrogen and another through the oxygen atom
forming an oximato bridge.4 In the majority of complexes,
oxime generally coordinates via nitrogen, and the oxygen
atom does not participate in coordination to the metal center.
In contrast, O-binding occurs in multinuclear assemblies
incorporating two-atom bridging modes, wherein the nitrogen
atom is also involved in bonding.5 Among the oxime ligands,
the chelating properties of 2,6-diacetylpyridinedioxime (dap-
dOH2) and 2,6-diacetylpyridinemonooxime (dapmOH) have
been investigated, and various coordination modes have been
discovered.6 Further, dapdOH2 has been recently employed
in the construction of high-nuclearity clusters.7 Although,
synthetic and structural chemistries of metal-oxime com-
plexes have been extensively studied,8-10 reactivity of the
coordinated oxime group has received little attention.11-16
Metal mediated or catalyzed Beckmann rearrangement has
been an established approach in isomerization of aldoxime
to amide, and depending upon the nature of reacting oxime
Justification of the role of metal complexes in organic
reactions has attracted sustained interest among the scientific
community over many decades. In this regard, application
of a purely organic approach in inorganic molecules has been
the subject of investigation by many research groups.1
Further, analogous to Schiff bases, oxime ligands have played
a significant role in the development of coordination chem-
istry2 because a ligand oxime moiety is potentially ambi-
dentate and can coordinate with metal ions either through
* To whom correspondence should be addressed. E-mail: dspbhu@
bhu.ac.in.
†
Banaras Hindu University.
National Institute of Advanced Industrial Science and Technology.
‡
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11942 Inorganic Chemistry, Vol. 47, No. 24, 2008
10.1021/ic8009699 CCC: $40.75  2008 American Chemical Society
Published on Web 11/12/2008

ReactiWity of the Oxime/Oximato Group in Ru(II) Complexes
moieties, reaction conditions have been modified consider-
ably.17 In contrast to aldoximes, metal-mediated isomeriza-
tion of ketoximes is a rare reaction.18 In this direction, we
have dedicated our efforts to examine the influence of metal
ion on reactivity of the metal coordinated ketoxime group
of the ligands dapdOH2 and dapmOH in ruthenium com-
plexes trans-[(κ3-dapdOH)Ru(CO)(PPh3)2]PF6 (1) and trans-
[(κ3-dapmOH)RuCl(PPh3)2]PF6 (2). In this paper, we describe
the reactivity of the oxime moiety of dapmOH and dapdOH2
with various species, SOCl2, NaBH4, and HCHO, in com-
plexes 1 and 2 leading to the oximato, imino, or hydroxym-
ethylimino groups. We also present herein structural support
for the formation of heteroleptic oxime/oximato complex
trans-[(κ3-dapdOH)Ru(CO)(PPh3)2]PF6 (1) and its trans-
formed products homoleptic oximato/oximato complex trans-
[(κ3-dapdO)Ru(CO)(PPh3)2] (11) and heteroleptic oximato/
imino complex trans-[(κ3-dapd-NH)Ru(CO)(PPh3)2]PF6 (13).
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Results and Discussion
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Synthesis and Characterization of Cationic trans-
[(K3-dapdOH)Ru(CO)(PPh3)2]PF6 (1) and trans-[(K3-
dapmOH)RuCl(PPh3)2]PF6 (2). The parent cationic com-
plex trans-[(κ3-dapdOH)Ru(CO)(PPh3)2]PF6 (1) was prepared
by reaction of a methanolic solution of dapdOH2 with
RuH(CO)Cl(PPh3)3 under refluxing conditions, and trans-
[(κ3-dapmOH)RuCl(PPh3)2]PF6 (2) was prepared following
our earlier procedure.19 The infrared spectrum of 1 displayed
a marked shift in position of the bands associated with νCdN
and oxime νN-O toward higher frequency by 30 and 85 cm-1,
respectively, compared with that in free ligand. Further, it
exhibited an additional band at 1093 cm-1 corresponding to
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ν
N-O. The presence of a band associated with νN-O in the
high-energy side suggested deprotonation of one of the oxime
N-OH groups. Bands at 1601 and 1625 cm-1 may be
assigned to νCdN of the oximato and νCdN of the oxime group,
respectively. Coordinated carbonyl group (νCtO) vibrated as
1
a sharp band at 1987 cm-1. In the H NMR spectrum of
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and triphenylphosphine ligands appeared at their usual
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formulation of the complex. It was further authenticated
crystallographically. An ORTEP view of the complex cation
of 1 is shown in Figure 1. Important crystallographic data
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Inorganic Chemistry, Vol. 47, No. 24, 2008 11943

Singh et al.
N5,N6,P3,P4), equatorial positions about the ruthenium
center are occupied by the central pyridyl nitrogen (avg
Ru-N 2.013 Å), the oximato (avg Ru-N 2.075 Å) and
oxime nitrogens (avg Ru-N 2.115 Å) of dapdOH, and the
carbonyl group (avg Ru-C 1.897 Å), which is trans to the
central pyridyl nitrogen (avg C-Ru-N 178.35°). The apical
positions are occupied by triphenylphosphine groups (avg
Ru-P 2.4272 Å, avg P-Ru-P 176.98°). It is noteworthy
that the Ru-Noximato distances (avg 2.075 Å) are shorter than
the Ru-Noxime distance (avg 2.115 Å), indicating better donor
ability of the oximato group.12a Furthermore, deprotonation
of the N-OH group leads to shortening of the N-O and
lengthening of the CdN bond lengths. As indicated, the
CdNoximato bond lengths (C3-N1 1.328 Å; C49-N4 1.318
Å; avg 1.323 Å) are longer than the CdNoxime bond distances
(C9-N3 1.297 Å; C55-N6 1.302 Å; avg 1.300 Å). The
N-Ooximato bond lengths (N(3)-O(2) 1.295(6) Å; N(6)-O(5)
1.300 Å; avg 1.298 Å) are well below the N-Ooxime bond
distances (N(1)-O(1) 1.371(7) Å; N(4)-O(4) 1.363(6) Å;
avg 1.367 Å).
Although coordination geometry about the metal center
in the crystallographically independent molecular units of 1
are equivalent, overall arrangements of the phenyl rings of
triphenylphosphine are quite different (see Supporting In-
formation, Figure S1). It is interesting to see that the phenyl
rings of triphenylphosphine in the molecule associated with
Ru2 are in eclipsed conformation with a dihedral angle of
0.75°, on the other hand a highly stable staggered arrange-
ment (dihedral angle 60.69°) has been observed in the other
unit with Ru1 as the metal center. The eclipsed conformation
of the phosphines leaves ∼50% of dapdOH ligand uncovered,
with involvement of direct πph/πpy/πph interactions (πph-πpy
3.546 Å, πpy-πph 3.387 Å); however in the staggered
arrangement, the whole of the dapdOH is covered and, as
expected, no direct π/π/π interactions have been observed
(average parameter for π/π interactions, πph-πpy 3.412 Å).20
The molecular units of 1 are interconnected via the inter-
mediacy of a bridging water molecule (bridging angle )
123.31(23)°) as shown in Figure 2. The oxime and oximato
oxygen atoms are involved in an intermolecular hydrogen-
bonding interaction. The Ooxime · · ·Owater distances are 2.691(13)
and 2.716(13) Å for O3 · · ·O2w and O6 · · ·O1w, respectively.
The corresponding O5 · · · O2w distance for oximato oxygen
is 2.726(11) Å.21
Figure 1. ORTEP view of complex cation of 1 (hydrogen atoms omitted
for clarity).
Table 1. Crystallographic Data for 1, 11, and 13
1
11
13
C92H80F12N6
O8P6Ru2
2013.58
monoclinic
P21/a
15.919(2)
24.2481(16)
24.8093(16)
106.15
C46H39N3
O3P2Ru
844.81
monoclinic
P21/n
9.837(2)
23.636(5)
17.079(3)
90.48(3)
3970.7(14)
4
C46H40F6N3
O5P3Ru
1022.79
monoclinic
P21/c
9.924(2)
20.904(4)
22.941(5)
91.03(3)
4758.2(17)
4
formula
fw
cryst syst
space group
a, Å
b, Å
c, Å
ꢀ, deg
V, Å3
9198.7(15)
4
Z
F(calcd), g cm-3
µ, mm-1
no. reflns collected
no. unique reflns
Rint
R1[I > 2σ(I)]
wR2[I > 2σ(I)]
R1 (all data)
wR2 (all data)
GOF
1.454
0.515
16740
16099
0.0444
0.0560
0.1441
0.1557
1.413
0.521
51079
7117
0.0972
0.0635
0.2449
0.0700
0.2549
1.139
1.428
0.501
42955
8340
0.1730
0.0963
0.2137
0.1207
0.2300
1.082
0.1747
1.017
Table 2. Selected Interatomic Distances (Å) and Angles (deg) for 1,
11, and 13
1
11
13
Ru-N2py
2.010(5)
2.063(5)
2.117(5)
1.898(8)
2.4317(17)
2.4225(18)
1.294(6)
1.377(6)
1.145(8)
1.329(8)
1.296(8)
175.74(6)
154.4(2)
177.9(3)
2.019(5)
2.114(5)
2.099(4)
1.868(6)
2.3932(14)
2.4016(13)
1.320(6)
1.302(6)
1.151(8)
1.329(9)
1.352(8)
175.57(4)
153.9(2)
177.90(18)
2.021(6)
2.059(6)
2.121(6)
1.871(8)
2.4222(18)
2.3910(18)
1.280(9)
Ru-N1oximato
Ru-N3oxime/oximato/imino
Ru-C1carbonyl
Ru-P1
Ru-P2
N1-O2oximato
N3-O3oxime/oximato
C1-O1carbonyl
C3-N1oximato
C9-N3oxime/oximato/imino
P1-Ru1-P2
N1-Ru1-N3
C1-Ru1-N2
Complexes 1 and 2 reacted with various species under
varying reaction conditions to afford complexes 3-14.
Analytical and spectral data along with the reaction details
are recorded in the Experimental Section. Substitution of the
chloro group in complex 2 by CN- and Br- easily afforded
the complexes trans-[(κ3-dapmOH)RuCN(PPh3)2]PF6 (3) and
1.133(9)
1.354(10)
1.283(9)
176.38(6)
152.8(3)
178.0(3)
and selected geometrical parameters are summarized in
Tables 1 and 2, respectively.
(20) (a) Braga, D.; Dyson, P. J.; Grepioni, F.; Johnson, B. F. G. Chem.
ReV. 1994, 94, 1585. (b) Ye, S.; Kaim, W.; Sarkar, B.; Schwederski,
B.; Lissner, F.; Schleid, T.; Toia, C. D.; Fiedler, J. Inorg. Chem.
Commun. 2003, 6, 1196. (c) Meyer, E. A.; Castellano, R. K.; Diederich,
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Orange red crystals of the heteroleptic complex 1 crystal-
lize in the P21/a space group with two crystallographically
independent molecules in the asymmetric unit. Coordination
geometry about each Ru(II) center (Ru1 and Ru2) can be
best described as a distorted octahedron with CN3P2 donor
groups.Ineachunit(Ru1,C1,N1,N2,N3,P1,P2andRu2,C2,N4,-
11944 Inorganic Chemistry, Vol. 47, No. 24, 2008

ReactiWity of the Oxime/Oximato Group in Ru(II) Complexes
Scheme 2
Figure 2. Diagram showing hydrogen-bonding interactions between two
crystallographically independent molecular units of 1.
7-10 in appreciably good yields (Scheme 2). All the
complexes have been characterized by analytical and spectral
studies (see Experimental Section). It was observed that the
reactions of bis-chelating ligands bpy or phen forced the
coordinated κ3-dapdOH to κ2 mode providing a site for
coordination of the entrant group.25 Spectral data of 7 and 8
supported octahedral coordination geometry about the metal
center, wherein ruthenium is bonded to a bidentate ligand
bpy or phen, triphenylphosphine, carbonyl group, and
dapdOH bonded in a κ2 mode. Further, being a strong donor,
oximato nitrogen is expected to remain intact with the metal
center in complexes 7 and 8. Analytical and spectral data
supported an analogous arrangement of the various groups
about the metal center with pendant oxime nitrogen in 9 and
10. The central pyridyl nitrogen of dapdOH or dapmOH is
trans to carbonyl and chloro groups in 7 and 8 and 9 and
10, respectively.
Further, it was observed that in each case an excess of
bis-chelating ligand is required to afford the final products.
In the formation of 8 and 10, use of 1.5-2.0-fold excess of
phenanthroline afforded the complexes in good yield. Further,
reaction of complex 2 with a large excess of phenanthroline
led to the formation of [Ru(phen)3]2+ as one of the side
products.
Synthesis of trans-[(K3-dapdO)Ru(CO)(PPh3)2] (11)
and trans-[(K3-dapmO)RuCl (PPh3)2] (12). Metal-assisted
deoxygenation reactions of oximes are expected to undergo
reduction with intermediacy of an oximato-metal intermedi-
ate complex, which is formed by cleavage of the oxime OH
bond;24,25 however decarboxylation is also considered in
some cases.26 The organic imines formed by deoxygenation
are easily hydrolyzed to ketone, whereas coordination of the
oxime with the metal center provides enough stability and
rigidity to coordinated nitrogen to diminish the chances of
facile hydrolysis of imine to ketone. Reaction of an equimolar
mixture of 1 in dry methanol and NaBH4 rapidly afforded a
dark-red precipitate, which was characterized as 11 (Scheme
Scheme 1
trans-[(κ3-(dapmOH)RuBr(PPh3)2]PF6 (4). The presence of
characteristic bands corresponding to coordinated CN at 2070
cm-1 in the infrared spectrum of 3 indicated the feasibility
of the substitution processes.
Synthesis of trans-[(K3-dapd-OCH2OH)Ru(CO)(P-
Ph3)2]PF6 (5) and trans-[(K3-dapm-OCH2OH)RuCl(P-
Ph3)2]PF6 (6). Alkylation, acylation, and arylation of oximes
have been extensively studied in organic chemistry;22
however, involvement of metal complexes in these processes
have scarcely been explored.12a,23 Reactions of 1 with
formaldehyde in 2-methoxyethanol transformed the oxime
OH to OCH2OH and afforded complex 5. In a similar
manner, complex 2 afforded [(κ3-dapm-OCH2OH)RuCl-
1
(PPh3)2]PF6 (6) as shown in Scheme 1. H NMR spectra of
5 and 6 in CDCl3 displayed resonances associated with
methylene protons as singlets at 2.75 and 3.24 ppm,
respectively. The hydroxyl proton in these complexes ap-
peared at 12.300 (5) and 11.669 ppm (6). Pyridyl and PPh3
protons resonated at their usual positions.14
Synthesis of [(K2-dapdOH)Ru(CO)(L)(PPh3)]PF6 (L
) bpy (7), phen (8)) and [(K2-dapmOH)RuCl(L)-
(PPh3)]PF6 (L ) bpy (9), phen (10)). Treatment of 1 and
2 with 2,2-bipyridine (bpy) and 1,10-phenanthroline (phen)
in dichloromethane at room temperature afforded complexes
(22) Metzger, H. In Houben-Weyl’s Methoden der organischen Chemie,
4th ed.; Mu¨ller, E., Ed.; G. Thieme Verlag: Stuttgart, Germany, 1968;
Stickstoffverbindungen I, Teil 4, Vol. 10:4, p 217.
(23) (a) Kazankov, G. M.; Dyachenko, O. G.; Nemukhin, A. V.; Ryabov,
A. D. MendeleeV Commun. 1997, 159. (b) Zerbib, V.; Robert, F.;
Gouzerh, P. J. Chem. Soc., Chem. Commun. 1993, 2179.
(24) (a) Alper, H.; Edward, J. T. Can. J. Chem. 1970, 48, 1543. (b)
Charalambous, J.; Haines, L. I. B.; Morgan, J. S.; Peat, D. S.;
Campbell, M. J. M.; Bailey, J. Polyhedron 1987, 6, 1027.
(25) Akazome, M.; Tsuji, Y.; Watanabe, Y. Chem. Lett. 1990, 635.
(26) Langenbahn, M.; Stoeckli-Evans, H.; Suss-Fink, G. HelV. Chim. Acta
1991, 74, 549.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11945

Singh et al.
Scheme 3
3). Contrary to other reports, a single product was obtained.27
Furthermore, conversion of the carbonyl group to a formyl
group was not observed as reported for related carbonyl
complexes.27 This may be attributed to the ability of a softer
client for the oxime N-OH bond than the carbonyl group.
An easier dissociation of the oxime proton leads to delocal-
ization of electron density over CdNsO- bond. Although
use of dry methanol as a solvent facilitated reaction by
effective precipitation and purification of the final product,
acetonitrile-water (1:1 v/v) mixture also afforded the same
product in quantitative yield.28 An analogous product with
the formulation trans-[(κ3-dapmO)Ru(PPh3)2Cl] (12) was
obtained from reactions of 2 under analogous conditions.
Treatment of 1 and 2 with other mild bases such as methyl
amine or methoxide afforded neutral products, which cor-
responded to 11 and 12, respectively (Scheme 3). All the
complexes have been characterized by elemental analyses
and spectral data. The coordinated CO group in the infrared
spectrum of 11 vibrated at 1959 cm-1. Deprotonation of the
oxime causes lengthening of the CdN bond distance, which
is supported by presence of a band at 1582 cm-1. Similarly,
in the infrared spectrum of 12, the band at 1582 cm-1 may
be attributed to νCdN oximato, and the νCdO band appears at
1627 cm-1.
It is noteworthy that the treatment of dapdOH2 with
RuH(CO)Cl(PPh3)3 in benzene also afforded 11 in high yield,
which has been characterized by spectral data (Scheme 3).
The molecular structure of 11 has been determined crystal-
lographically. ORTEP depiction of 11 is shown in Figure 3.
Crystallographic data and selected bond parameters for 11
are summarized in the Tables 1 and 2, respectively. Complex
11 exhibits a distorted octahedral geometry about the
ruthenium center analogous to that observed in complex 1,
with a dianionic κ3-dapdO, two trans disposed triph-
enylphosphines, and a carbonyl group trans to central pyridyl
nitrogen. A significant distortion is evidenced from the
N1-Ru1-N3 bond angle, which is 153.9°. The P1-Ru1-P2
angle of 175.57° shows that the triphenylphosphine ligands
are disposed trans to each other. The chelate bite angles
involving N1-Ru1-N2 and N2-Ru1-N3 are 77.0° and
76.9°, respectively, which also reflects observed deviation
Figure 3. ORTEP plot for complex 11 with 30% ellipsoid probability.
Figure 4. Diagram showing hydrogen bonding between two adjacent
molecular units in 11.
from the octahedral geometry. The C1-Ru1-N2 bond angle
of 177.90° suggested that the carbonyl group is trans to the
central pyridyl nitrogen. Both the N-O bond distances
are similar with an average distance of ca. 1.311 Å,12a and
the C-O bond distance is 1.151(8) Å. Figure 4 shows the
involvement of oximato and carbonyl oxygen atoms in
intermolecular C-H· · ·O hydrogen bonding interactions with
phenyl and pyridyl protons, respectively. The matrices for
these interactions are as follows: C44Ph-H44 · · · O3oximato
,
H44· · ·O32.612(35)Å,C44 · · ·O33.319(48)Å,∠C44-H44 · · ·O3
133.27(35)°; C5py-H5 · · · O1CO, H5 · · · O1 2.550(34) Å,
C5 · · · O1 3.465(47) Å, ∠C5-H5 · · · O1 167.68(34)°.
Synthesis of trans-[(K3-dapd-NH)Ru(CO)(PPh3)2]PF6
(13) and trans-[(K3-dapm-NH)Ru(CO)(PPh3)2]PF6 (14). An
attempt has been made to examine isomerization of the metal
coordinated ketoxime ligand in 1 and 2 under the conditions
employed for Beckmann rearrangement. Treatment of cat-
ionic parent complexes 1 and 2 with thionyl chloride in
tetrahydrofuran followed by vigorous boiling of resultant
solid product in distilled water afforded complex 13 and 14,
respectively. Interestingly, in contrast to expected amido
group, the oxime group is efficiently transformed to imine
as shown in Scheme 4.
(27) (a) Gibson, D. H.; Andino, J. G.; Bhamidi, S.; Sleadd, B. A.; Mashuta,
M. S. Organometallics 2001, 20, 4956. (b) Schwartsburd, L.; Pover-
enov, E.; Shimon, L. J. W.; Milstein, D. Organometallics 2007, 26,
2931. (c) Tam, W.; Lin, G.-Y.; Wong, W.-K.; Kiel, W. A.; Wong,
V. K.; Gladysz, J. A. J. Am. Chem. Soc. 1982, 104, 141. (d) Tam,
W.; Wong, W.-K.; Gladysz, J. A. J. Am. Chem. Soc. 1982, 104, 141.
(e) Sweet, J. R.; Graham, W. A. G. J. Am. Chem. Soc. 1982, 104,
2811.
(28) (a) Gibson, D. H.; Owens, K.; Richardson, J. F. Organometallics 1987,
6, 2624. (b) Gladysz, J. A. AdV. Organomet. Chem. 1982, 20, 1. (c)
Gibson, D. H.; Owens, K.; Mandal, S. K.; Franco, J. O.; Sattich, W. E.
Organometallics 1989, 8, 498.
Both the complexes were characterized by elemental
analyses, spectral data, and X-ray crystallography. A sharp
band at ca. 3500 cm-1 in the infrared spectra reflects
11946 Inorganic Chemistry, Vol. 47, No. 24, 2008

ReactiWity of the Oxime/Oximato Group in Ru(II) Complexes
Scheme 4
Chart 1
Figure 6. ORTEP view of complex 14 with 30% ellipsoid probability.
parameters of 13 are summarized in Tables 1 and 2. (We
could not get satisfactory data on complex 14, and structural
refinement of this complex is not sufficiently good for
reporting; however, available data supports our viewpoint.)
The molecular identity and overall coordination geometry
about the ruthenium center in 13 and 14 is similar to that in
the respective parent complexes 1 and 2. In trans-[(κ3-dapd-
NH)Ru(CO)(PPh3)2]PF6 (13), the Ru-Nimine bond is 2.099(4)
Å. The chelate bite angles involving N1-Ru1-N2 and
N2-Ru1-N3 are 77.0(2)° and 76.9(2)°, respectively, which
reflects observed deviation from the octahedral geometry.
Further, the tridentate mode of dapd-NH reflects the
distortion as evidenced by the N1-Ru1-N3 bond angle of
152.8(3)°. The phosphine ligands are essentially trans
disposed (P1-Ru1-P2 176.38(6)°); however, the relative
orientation of the phenyl rings force it to a staggered
arrangement when viewed along P1-Ru1-P2 axis. The
trans position of the carbonyl group to the central pyridyl
nitrogen is reflected by the C1-Ru1-N2 bond angle of
178.0(3)°. The imino nitrogen is involved in an intermo-
lecular N-H · · · F interaction with a fluoride atom of the
reduction of the N-OH to N-H. Following the conventional
mechanistic pathway for Beckmann rearrangement in organic
molecules, a proposed mechanism is illustrated in Chart 1.
However in our case the oxime to imino transformation
process favors a “water-assisted reduction pathway”, because
it has been observed that under the reaction conditions water
may act as a dehalogenating agent.17e,f
ORTEP views of 13 and 14 are shown in Figures 5 and
6, respectively. Crystallographic data and important bond
-
counteranion PF6 . The matrices for these interactions are
as follows: N3-H1 · · ·F1, H1 · · ·F1 1.819 Å, N3 · · ·F1 3.013
Å, ∠N3-H1 · · · F1 147.21°.
Conclusions
In this work an effort has been made to apply an organic
approach to inorganic molecules and to efficiently transform
metal-coordinated oxime to oximato/imino/hydroxyimino
complexes. Application of conventional Beckmann rear-
rangement on 1 and 2 shows that the coordination of
heteroatoms to the metal center additionally stabilizes the
organic moiety, thus effectively influencing the traditional
mechanistic pathways and final products.
Experimental Section
General Considerations. Elemental analyses on complexes were
performed by the Microanalytical Section of the Sophisticated
Analytical Instrumentation Centre, Central Drug Research Institute,
Lucknow. Infrared spectra in KBr discs were obtained on a Varian
Figure 5. ORTEP view of complex 13 with 30% ellipsoid probability.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11947

Singh et al.
spectrometer. NMR spectra were recorded on a Bruker DRX-300
refluxing over 8 h. Resulting solution was cooled to room
temperature and evaporated to dryness to afford a dark brown
residue. The residue was washed with water, redissolved in
methanol, and evaporated to dryness. The solid product thus
obtained was washed with diethyl ether and dried in air; the yield
was 0.742 g (72%). Anal. Calcd for C45H40N2O2BrP3F6Ru (1030):
C, 52.43; H, 3.88; N, 2.72%. Found: C, 52.78; H, 3.72; N, 2.92.
1
NMR spectrometer. H and 31P and chemical shifts are reported
relative to TMS and PCl3 (δ ) 220), respectively. FAB mass spectra
were acquired on a JEOL SX 102/DA 6000 mass spectrometer using
Xenon (6 kV, 10 mA) as the FAB gas. Accelerating voltage was
10 kV, and the spectra were recorded at room temperature with
m-nitrobenzyl alcohol as matrix.
Materials. All the synthetic manipulations were performed using
deaerated AR grade solvents, which were purified rigorously by
standard procedures prior to their use.29 Ammonium hexafluoro-
phosphate, 2,6-diacetylpyridine, and ruthenium(III) chloride hydrate
(all Aldrich) were used as received without further purification.
The complexes RuH(CO)Cl(PPh3)3 and RuCl2(PPh3)3 and the
ligands 2,6-diacetylpyridinedioxime (dapdOH2) were synthesized
following the literature procedures.30,31 The precursor complex
trans-[(κ3-dapmOH)RuCl(PPh3)2]PF6 (2) was synthesized using our
procedure reported elsewhere.19
1
IR (KBr, cm-1): νP-F 842. H NMR (300 MHz, CDCl3): δ 10.41
(s, 1H, N-OH), 7.60 (t, J ) 7.7 Hz, 1H), 7.44 (d, J ) 7.2 Hz, 1H),
7.26-7.21 (m, 30H, PPh3), 6.81 (d, J ) 5.0 Hz, 1H), 1.85 (s, 6H).
31P NMR (120 MHz, CDCl3): δ 29.97 (s, PPh3), -141.21 (septet,
PF6).
Synthesis and Characterization of trans-[(K3-dapd-OCH2-
OH)Ru(CO)(PPh3)2]PF6 (5). To a suspension of complex 1 (0.992
g, 1.0 mmol) in 2-methoxyethanol (60 mL), formaldehyde (37-41%
20 mL) was added, and the reaction mixture was refluxed for 4 h.
The resulting solution was filtered to remove any solid impurities
and filtrate was precipitated by addition of diethyl ether. The orange-
brown product thus precipitated was separated by filtration,
repeatedly washed with petroleum spirit, and dried in air; the yield
was 0.634 g (62%). Anal. Calcd for C46H42N3O4P3F6Ru (1022): C,
55.19; H, 4.11; N, 4.11%. Found: C, 54.98; H, 4.32; N, 3.92%.
Selected IR data (KBr, cm-1): 2001 (νCtO), 1654(νCdN), 842 (νP-F).
1H NMR (300 MHz, CDCl3): δ 7.76 (t, J ) 7.7 Hz, 1H), 7.48 (d,
J ) 7.2 Hz, 1H), 7.36-7.25 (m, 30H, PPh3), 6.69 (d, J ) 5.0 Hz,
1H), 4.12 (br, s, 1H, OH), 2.75 (s, CH2, 2H), 1.85 (br. s, 6H, CH3).
31P NMR (120 MHz, CDCl3): δ 45.84 (s, PPh3), -141.23 (septet,
PF6).
Synthesis and Characterization of trans-[(K3-dapm-OCH2-
OH)RuCl(PPh3)2]PF6 (6). Complex 6 was prepared following the
above procedure adopted for 5, except that complex 2 was used in
place of 1. After filtration, the solution was allowed to cool at ∼ 4
°C over several days. It gave a microcrystalline dark brown
compound, which was washed with diethyl ether and air-dried; the
yield was 0.620 g, (∼61%). Anal. Calcd for C46H42N2O3ClP3F6Ru
(1016): C, 54.33; H, 4.13; N, 2.76%. Found: C, 54.48; H, 4.02; N,
2.98%. Selected IR data (KBr, cm-1): 1627 (νCdN), 840 (νP-F). 1H
NMR (300 MHz, CDCl3): δ 7.79 (m, 1H), 7.51-7.12 (m, 30H,
PPh3), 6.82 (d, J ) 7.1 Hz, 1H), 4.12 (br, s, 1H, OH), 3.24 (s,
CH2, 2H), 2.01 (br. s, 6H, CH3). 31P NMR (120 MHz, CDCl3): δ
32.24 (s, PPh3), -141.01 (septet, PF6).
Synthesis and Characterization of [(K2-dapdOH)Ru(CO)-
(K2-bpy)(PPh3)]PF6 (7). Complex 1 (0.099 g, 0.1 mmol) was treated
with a large excess of 2,2′-bipyridine (∼1.5 mmol) in dichlo-
romethane (80 mL) and stirred for 8 h. The solution was evaporated
to dryness and extracted with dichloromethane and filtered. The
filtrate was treated with diethyl ether to afford a light orange
compound. The product was separated by filtration, washed with
diethyl ether, and dried under vacuum; the yield was 0.050 g (56%).
Anal. Calcd for C38H33N5O3P2F6Ru (885): C, 51.53; H, 3.73; N,
7.91%. Found: C, 51.90; H, 3.62; N, 8.02%. Selected IR data (KBr,
cm-1): 1998 (νCtO), 1601 (νCdN), 843 (νP-F). 1H NMR (300 MHz,
CDCl3): δ 11.01 (s, 1H, N-OH), 8.92 (m, 2H), 8.68 (d, J ) 7.9
Hz, 2H), 8.35 (d, J ) 7.9 Hz, 2H), 7.78-7.62 (m, 3H), 7.50-7.36
(m, 15H), 6.24 (d, J ) 7.7 Hz, 2H), 1.26 (br. s, 6H, CH3). 31P
NMR (120 MHz, CDCl3): δ 30.64 (s, PPh3), -142.11 (septet, PF6).
Synthesis and Characterization of [(K2-dapdoH)Ru(CO)-
(K2-phen)(PPh3)]PF6 (8). Complex 8 was prepared following the
above procedure for 7 except that a small excess of 1,10-
phenenthroline (0.040 g, 0.2 mmol) was used in place of 2,2′-
bipyridine. Complex 8 was obtained as red-orange solid; the yield
was 0.049 g, (54%). Anal. Calcd for C40H33N5O3P2F6Ru (909): C,
52.81; H, 3.63; N, 7.70%. Found: C, 52.47; H, 3.77; N, 7.91%.
Synthesis and Characterization of trans-[(K3-dapdOH)-
Ru(CO)(PPh3)2]PF6 (1). To a methanolic solution (15 mL) of
dapdOH2 (1.0 mmol, 0.192 g), RuH(CO)Cl(PPh3)3 (0.955 g, 1.0
mmol) was added, and the reaction mixture was refluxed for 14 h.
The resulting orange-red solution was filtered and concentrated to
approximately (4 mL). A saturated solution of ammonium hexaflu-
orophosphate dissolved in methanol (10 mL) was added to it and
left undisturbed to concentrate slowly by evaporation at room
temperature. It separated as an orange red microcrystalline complex,
which was separated by filtration, washed twice with methanol and
diethyl ether, and dried under vacuum; the yield was 0.605 g
(∼61%). Anal. Calcd for C46H40N3OP3F6Ru (992): C, 55.65; H,
4.03; N, 4.23%. Found: C, 55.79; H, 4.42; N, 3.92%. Selected IR
data (KBr, cm-1): 1987 νCtO, 1625, 1601, 1483, 1435, 1294, 1093,
1
999, 854, 775, 748, 698, 519. H NMR (300 MHz, acetone-d6): δ
10.94 (s, 1H, N-OH), 7.79 (t, J ) 7.8 Hz, 1H), 7.50 (d, J ) 7.2
Hz, 1H), 7.38-7.44 (m, 30H, PPh3), 6.64 (d, J ) 7.8 Hz, 1H),
1.85 (s, br.). 31P NMR (120 MHz, acetone-d6): δ 29.45 (s, PPh3),
-142.81 (septet, PF6). UV-vis.(acetone, λmax nm): 450 (12300),
355 (46220), 273 (48900); Emission (acetone, λem (λex) nm): 675
(450).
Synthesis and Characterization of trans-[(K3-dapmOH)-
RuCN(PPh3)2]PF6 (3). To a suspension of complex 2 (0.985 g,
1.0 mmol) in methanol (25 mL), NaCN (0.049 g, 1.0 mmol) was
added and refluxed for 8 h. Resulting solution was evaporated to
dryness and washed a couple of times with diethyl ether and dried
in air to afford a light brown compound. It was recrystallized from
CHCl3 and petroleum ether (60-80 °C); the yield was 0.771 g
(79%). Anal. Calcd for C46H40N3O2P3F6Ru (976): C, 56.56; H, 4.16;
N, 4.30%. Found: C, 56.48; H, 4.52; N, 4.12%. Selected IR data
(KBr, cm-1): 2070 (νCtN), 842 (νP-F). 1H NMR (300 MHz, CDCl3):
δ 10.41 (s, 1H, N-OH), 7.60 (t, J ) 7.7 Hz, 1H), 7.44 (d, J ) 7.2
Hz, 1H), 7.26-7.21 (m, 30H, PPh3), 6.81 (d, J ) 5.0 Hz, 1H),
1.85 (s, 6H). 31P NMR (120 MHz, CDCl3): δ 30.11 (s, PPh3),
-141.79 (septet, PF6).
Synthesis and Characterization of trans-[(K3-dapmOH)-
RuBr(PPh3)2]PF6 (4). Complex 4 was prepared by reaction of
complex 2 (0.985 g, 1.0 mmol) with a large excess of KBr (∼20
mmol) in an ethanol-water mixture (25 mL, 3:1 v/v) under
(29) Perrin, D. D.; Armango, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, U.K., 1986.
(30) (a) Ahmad, N.; Levison, J. J.; Robinson, S. D.; Uttley, M. F.;
Debaerdemaeker, T. J. Chem. Soc., Dalton. Trans. 1988, 2033. (b)
Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,
12, 238.
(31) Glynn, C. W.; Turnbull, M. M. Transition Met. Chem. 2002, 27, 822.
11948 Inorganic Chemistry, Vol. 47, No. 24, 2008

ReactiWity of the Oxime/Oximato Group in Ru(II) Complexes
Selected IR data (KBr, cm-1): 1965 (νCtO), 1654 (νCdN), 844 (νP-F).
1H NMR (300 MHz, CDCl3): δ 10.95 (s, 1H, N-OH), 9.20 (d, J
) 3.9 Hz, 2H), 8.26 (d, J ) 6.9 Hz, 2H), 7.81-7.65 (m, 5H),
7.45-7.29 (m, 15H), 6.18 (d, J ) 7.8 Hz, 2H), 1.25 (br. s, 6H,
CH3). 31P NMR (120 MHz, CDCl3): δ 30.52 (s, PPh3), -143.21
(septet, PF6).
Synthesis and Characterization of [(K2-dapmOH)RuCl-
(K2-bpy)(PPh3)]PF6 (9). Complex 2 (0.099 g, 0.1 mmol) was
dissolved in dichloromethane (35 mL), and bpy (0.020 g, 0.15
mmol) was added to it. The resulting dark brown-orange solution
was stirred for 24 h and then completely evaporated to dryness.
The solid residue was extracted with dichloromethane and precipi-
tated with diethyl ether. Resulting solid was washed with diethyl
ether and dried in air; the yield was 0.053 g (60%). Anal. Calcd
for C37H33N4O2ClP2F6Ru (879): C, 50.51; H, 3.75; N, 6.37%.
Found: C, 50.79; H, 3.79; N, 6.62%. Selected IR data (KBr, cm-1):
1602 (νCdN), 840 (νP-F). 1H NMR (300 MHz, CDCl3): δ 10.06 (s,
1H, N-OH), 9.61 (m, 2H), 8.69 (d, J ) 7.9 Hz, 2H), 8.39 (d, J )
8.1 Hz, 2H), 7.83-7.66 (m, 3H), 7.52-7.23 (m, 15H), 6.96 (d, J
) 7.5 Hz, 2H), 1.98 (br. s, 6H, CH3). 31P NMR (120 MHz, CDCl3):
δ 28.51 (s, PPh3), -142.71 (septet, PF6).
Synthesis and Characterization of [(K2-dapdoH)RuCl-
(K2-phen)(PPh3)]PF6 (10). Complex 10 was prepared from the
reaction of complex 2 (0.099 g, 0.1 mmol) with 1,10-phenanthroline
(0.030 g, 0.15 mmol) in dichloromethane (30 mL) and worked up
as complex 9. Complex 10 was obtained as orange-brown solid;
the yield was 0.054 g (∼61%). Anal. Calcd for C39H33-
N4O2ClP2F6Ru (903): C, 51.83; H, 3.65; N, 6.20%. Found: C, 52.01;
H, 3.72; N, 6.02%. Selected IR data (KBr, cm-1): 1602 (νCdN),
840 (νP-F) 1H NMR (300 MHz, CDCl3): δ 10.06 (s, 1H, N-OH),
9.59 (m, 2H), 9.19 (d, J ) 7.9 Hz, 2H), 8.25 (d, J ) 8.1 Hz, 2H),
7.81-7.60 (m, 3H), 7.52-7.23 (m, 15H), 6.96 (d, J ) 7.5 Hz,
2H), 1.99 (s, 6H, CH3). 31P NMR (120 MHz, CDCl3): δ 28.63 (s,
PPh3), -143.01 (septet, PF6).
the filtrate, freshly distilled thionyl chloride (3 mL) was added,
and the reaction mixture was stirred for 1 h. The dark red solution
rapidly turns to an orange-brown solution. It was allowed to stir
for an additional 1 h to afford a brown-orange precipitate. The
reaction mixture along with the precipitate was concentrated to
dryness and vigorously boiled with distilled water (25 mL) for
several hours. Resulting residue was filtered and washed with
diethyl ether to afford an orange-brown solid; the yield was 0.064
g (66%). Anal. Calcd for C46H40N3O2P3F6Ru (976): C, 56.56; H,
4.10; N, 4.30%. Found: C, 56.78; H, 4.42; N, 3.98%. Selected IR
data (KBr, cm-1): 1959 (νCtO), 1584 (νCdN). 1H NMR (300 MHz,
CDCl3): δ 7.43 (t, J ) 5.7 Hz, 1H), 7.41-7.26 (m, 30H), 6.65 (d,
J ) 7.1 Hz, 2H), 1.92 (s, 6H, CH3). 31P NMR (120 MHz, CDCl3):
δ 33.19 (s, PPh3), -141.41 (sep., PF6).
Synthesis and Characterization of trans-[(K3-dapm-NH)-
RuCl(PPh3)2]PF6 (14). A solution of complex 2 (0.099 g, 0.1
mmol) in THF (20 mL) was treated with freshly distilled thionyl
chloride (2.5 mL) and stirred for 1 h, affording a dark brown
precipitate. The solution along with the precipitate was concentrated,
and the residue thus obtained was vigorously boiled in distilled
water (25 mL) for several hours. The residue was extracted with
ethanol, which upon evaporation gave the desired complex; the yield
was 0.066 g (68%). Anal. Calcd for C45H40N2OClP3F6Ru (970):
C, 55.67; H, 4.12; N, 2.89. Found: C, 55.98; H, 4.42; N, 2.90%.
1
Selected IR data (KBr, cm-1): 1590, 839 (νP-F). H NMR (300
MHz, CDCl3): δ 7.89 (t, J ) 8.1 Hz, 1H), 7.45-7.30 (m, 30H),
6.71 (d, J ) 7.8 Hz, 2H), 2.00 (s, 6H, CH3). 31P NMR (120 MHz,
CDCl3): δ 28.24 (s, PPh3), -141.63 (sep., PF6).
Crystal Structure Determinations. Crystals suitable for single-
crystal X-ray diffraction analyses for complexes 1, 11, 13, and 14
were obtained by a liquid-liquid diffusion technique at room
temperature. Intensity data for 1 were collected at 293(2) K on
Enraf-Nonius CAD 4 diffractometer using graphite-monochroma-
tized Mo KR radiation (λ ) 0.71073 Å). Intensities of these
reflections were measured periodically to monitor crystal decay.
Single-crystal X-ray diffraction data for complexes 11, 13, and 14
were collected on an R-AXIS RAPID II diffractometer at room
temperature with Mo KR radiation (λ ) 0.71073 Å). The structures
were solved by direct methods and refined by full-matrix least-
squares on F2 (SHELX-97).32 All non-hydrogen atoms were refined
anisotropically. The contributions due to H-atoms attached to carbon
atoms were included as fixed contributions. Details about data
collection, structure solution, and refinement are recorded in Table
1, and selected geometrical parameters are presented in Table 2.
Synthesis and Characterization of trans-[(K3-dapdO)Ru-
(CO)(PPh3)2] (11). Complex 1 (0.099 g, 1.0 mmol) was stirred
with NaBH4 (0.019 g in 1 mL of diglyme) in dry methanol (10
mL) for 15 min, whereupon a dark red precipitate separated out.
The resulting precipitate was filtered through a sintered crucible,
washed with acetonitrile and diethyl ether, and dried under vacuum;
the yield was 0.060 g (70%). Anal. Calcd for C46H39N3O3P2Ru
(846): C, 65.25; H, 4.61; N, 4.96%. Found: C, 65.60; H, 4.32; N,
1
4.82%. Selected IR data (KBr, cm-1): νCtO 1959, νCdN 1586. H
NMR (300 MHz, CDCl3): δ 7.43 (t, J ) 5.7 Hz, 1H), 7.31-7.21
(m, 30H), 6.12 (d, J ) 7.1 Hz, 2H), 1.12 (s, 6H, CH3). 31P NMR
(120 MHz, CDCl3): δ 29.43 (s, PPh3).
Acknowledgment. The present work is supported by the
Council for Scientific and Industrial Research, New Delhi,
under Award No. 9/13(97)/2006-EMR-I. We also thank the
Head, Department of Chemistry, Faculty of Science, Banaras
Hindu University, Varanasi, India, and National Institute of
Advanced Industrial Science and Technology (AIST), Osaka,
Japan, for extending facilities.
Synthesis and Characterization of trans-[(K3-dapmO)Ru-
Cl(PPh3)2] (12). Complex 2 (0.099 g, 0.1 mmol) was stirred with
NaBH4 (0.019 g in 1 mL of diglyme) in an acetonitrile-water
mixture (6 mL, 1:1 v/v) for 30 min. A brown precipitate separated,
which was filtered, washed with diethyl ether, and air-dried; the
yield was 0.058 g (69%). Anal. Calcd for C45H39N2O2ClP2Ru (840):
C, 64.29; H, 4.64; N, 3.33%. Found: C, 64.66; H, 4.97; N, 3.45%.
1
Selected IR data (KBr, cm-1): 1584 (νCdN). H NMR (300 MHz,
Supporting Information Available: Crystallographic data (cif
format) of the complexes 1, 11, and 13 and figures showing the
relative arrangement of phenyl rings of the triphenylphosphine in
complex 1. This material is available free of charge via the Internet
at http://pubs.acs.org.
CDCl3): δ 7.43 (t, J ) 5.7 Hz, 1H), 7.31-7.21 (m, 30H), 6.12 (d,
J ) 7.1 Hz, 2H), 1.12 (s, 6H, CH3). 31P NMR (120 MHz, CDCl3):
δ 31.02 (s, PPh3).
Synthesis and Characterization of trans-[(K3-dapd-NH)-
Ru(CO)(PPh3)2]PF6 (13). Complex 1 (0.099 g, 0.1 mmol) was
dissolved in acetone (2 mL), and THF (25 mL) was added to it.
The resulting solution was concentrated to a final volume of 10
mL in a water bath, cooled to room temperature, and filtered. To
IC8009699
(32) Sheldrick, G. M. SHELXS-97: Program for Structure solution and
refinement of crystal structure, Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 47, No. 24, 2008 11949