Reactions of 2-(arylazo)aniline with ruthenium substrates: Isolation, characterizations and reactivities of delocalized diazoketiminato and orthometallated Ru(II) chelates

Article abstract of DOI:10.1016/j.jorganchem.2009.06.038

Reactions of 2-(arylazo)aniline, HL-NH₂ [H represents the dissociable protons upon complexation and HL-NH₂ is p-RC₆H₄N{double bond, long}NC₆H₄-NH₂; R = H for HL¹-NH

Full text of DOI:10.1016/j.jorganchem.2009.06.038

Journal of Organometallic Chemistry 694 (2009) 3401–3408
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactions of 2-(arylazo)aniline with ruthenium substrates: Isolation,
characterizations and reactivities of delocalized diazoketiminato
and orthometallated Ru(II) chelates
*
Jahar Lal Pratihar, Shantanu Bhaduri, Poulami Pattanayak, Debprasad Patra, Surajit Chattopadhyay
Department of Chemistry, University of Kalyani, Kalyani 741 235, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 2-(arylazo)aniline, HL-NH2 [H represents the dissociable protons upon complexation and
HL-NH2 is p-RC6H4N@NC6H4-NH2; R = H for HL1-NH2; CH3 for HL2-NH2 and Cl for HL3-NH2] with Ru(H)
(CO)(PPh3)3Cl and Ru(CO)3(PPh3)2 afforded products of compositions [(HL-NH)Ru(CO)Cl(PPh3)2] and
[(L-NH)Ru(PPh3)2(CO)], respectively. All the complexes were characterized unequivocally. The X-ray
structures of the complexes 4c and 5c have been determined. The cyclic volatammograms exhibited
one reversible oxidative response in the range of 0.56–0.16 V versus SCE for [(L-NH)Ru(PPh3)2(CO)]
and a quasi reversible oxidative response within 0.56–0.70 V versus SCE for [(HL-NH)Ru(CO)Cl(PPh3)2].
The conversion of ketones to corresponding alcohols has been studied in presence of newly synthesized
ruthenium complexes.
Received 30 April 2009
Received in revised form 22 June 2009
Accepted 26 June 2009
Available online 1 July 2009
Keywords:
2-(Arylazo)aniline
Ruthenium
Cycloruthenation
Redox
Ó 2009 Elsevier B.V. All rights reserved.
Hydrogen transfer reaction
1. Introduction
nium complexes of AAP to obtain new complexes where the
ligands bind with tridentate (N,N,S) mode [20], Several studies
Research in the area of coordination chemistry of ruthenium
incorporating various kinds of ligands has upsurged in recent years
due to the fascinating reactivities exhibited by the resultant com-
plexes [1–4]. Studies on the chemistry of ruthenium complexes
with azo ligands have been ongoing and several interesting results,
related to electron transfer reaction [5–26], metal–carbon bond
formation [14,22,23,25,26], aromatic ring amination [16–18],
isomerism [7,8,24], cytotoxicity toward cancer cells [5–11] and
application in catalytic transformations [25,26], were reported.
R
or
N
N
N
N
N
Hy =
or
R
X
1c
1b
1a
N
N
NH
Hy
The
p-acidic nature of azo (–N@N–) function was indicated to be
N
one of the reasons for fascinating properties of such ruthenium
complexes [5–26]. As a consequence we expected that the appro-
priately designed azo ligands can dictate the properties of ruthe-
nium complexes to originate new and more attractive results.
In general, the azo ligand systems may be divided into two cat-
egories: (i) arylazo heterocycles, 1 and (ii) associates of azobenzene
moiety, 2. Among these ligands most widely studied system is 2-
arylazo pyridine (AAP), 1a. AAP ligands bind to the ruthenium cen-
ter in bidentate fashion (N,N) affording different types of isomeric
complexes [7,8]. It was also reported that the metal mediated aryl
ring amination of AAP ligand lead to the formation of tridentate
(N,N,N) ligands [16–18], Aryl ring thiolation was studied in ruthe-
or
Hy =
H
R = Alkyl ; X=
,
1
R & R' = Alkyl
X
Y
X
2a
N
H
H
H
N
2b
2c
2d
OH
OH
SR'
Y
OH
H
R
* Corresponding author. Tel.: +91 33 24149725; fax: +91 33 25828282.
E-mail address: scha8@rediffmail.com (S. Chattopadhyay).
2
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.06.038

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J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
The products were characterized unequivocally. Redox properties
and conversion of ketones in presence of new ruthenium complexes
have been described.
related to electron transfer behavior [5–26], optical properties
[12,13] and cytotoxic behavior of ruthenium AAP complexes [5–
11] are worthwhile to mention. Isomerism and redox behavior of
ruthenium complexes of aryl azo imidazole, 1b, ligands were stud-
ied to a considerable extent [24].
2. Results and discussion
Chemistry of ruthenium complexes with azobenzene and related
ligands was not studied as much as that of arylazo heterocycle com-
plexes. A few ruthenium complexes of azobenzene and related
ligands were prepared and have been described to have interesting
properties. The complexes of 2-arylazo phenols, 2b, were demon-
strated to exhibit C–H activation [22,23,25,26], C–C activation
[23], C–C coupling [22] and catalytic hydrogen transfer reactions
[25,26]. Viewing this, we intended to study the chemistry of ruthe-
nium with new azobenzene related ligands. For the present pur-
pose, we have utilized 2-(arylazo)aniline, HL-NH2, 3, ligand for the
preparation of different types of ruthenium chelates.
2.1. Complex formation
Reactions of HL-NH2 with RuH(CO)Cl(PPh3)3 in refluxing tolu-
ene in anaerobic condition afforded a blue complex. Dissociation
of one amino proton of HL-NH2 and one hydride from RuH
(CO)Cl(PPh3)3 gave rise to the formation of blue and non conduct-
ing complex [(HL-NH)Ru(CO)Cl(PPh3)2], 4 (Scheme 1). The anionic
[HL-NH]ꢀ ligand coordinated the metal center forming a six mem-
bered diazoketiminato chelate. Therefore, formally the elimination
of one equivalent of hydrogen (H+ + Hꢀ ? H2) in addition to disso-
ciation of a PPh3 ligand was believed to be the essential criterion to
form the complex 4. Previously, we reported that the reaction of
HL-NH2 with RhCl(PPh)3, where oxidative addition of the ligand
led to the formation of cyclometallated Rh(III) complex [27]. By
analogy we considered that an oxidative addition on ruthenium
center may also afford the cyclometallated complex.
Hence, we assumed that a Ru(0) substrate may bind with
HL-NH2 giving rise to Ru–C bond formation. Indeed, reactions of
the ligand system 2-(arylazo)aniline, with Ru(CO)3(PPh3)2, afforded
the cyclometallated complexes as given in 5. The [(L-NH)Ru(PPh3)2
(CO)], 5, complexes are a new family of orthometallated complexes
of Ru(II) [Eq. (1)]. Besides the elimination of one of the amino pro-
tons, an aryl proton of HL-NH2 was dissociated from the pendant
aryl ring during orthometallation. Two electron oxidation of
Ru(0) center and concomitant dissociation of two protons from
the ligand is formally consistent with the release of 2H+ ꢀ 2eꢀ.
Reactions of HL-NH2 with Ru(CO)3(PPh3)2 in inert condition or in
R
R= H for HL1-NH2 (3a); CH3 for
HL2-NH2 (3b); Cl for HL3-NH2 (3c)
N
N
NH2
3
Herein we report the reaction of 2-(arylazo)aniline, 3, with two
ruthenium substrates. It has been shown that the different products
were formed upon varying the ruthenium substrates. Orthometal-
lated ruthenium (II) complexes were obtained from Ru(0) substrate.
R
PPh3
RuH(CO)Cl(PPh3)3
Toluene
CO
Cl
N
N
R
Ru
NH
PPh3
N
4
N
NH2
R
N
Ph3P
3
CO
Ru
Ru(CO)3(PPh3)2
Toluene
N
PPh3
Compound
R
H
NH
3a; 4a; 5a
CH3
Cl
3b; 4b; 5b
3c; 4c; 5c
5
Scheme 1.

J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
3403
presence of air afforded the identical product which was antici-
pated to occur either by releasing H2 or H2O, respectively.
600 nm and 800 nm, respectively. The low energy absorptions in
metal complexes have been reported to occur due to electronic
transition either from or to the energy levels containing substantial
ligand character [27–32]. The representative UV–Vis spectra of
complexes are shown in Fig. 1. The UV–Vis spectra of all the com-
plexes are given in Supplementary material (Figs. S1–S6) and data
are collected in Section 3.
HL-NH2 þ ½Ru0ꢁ ! ½ðL-NHÞRuIIꢁ þ 2Hþ þ 2e
ð1Þ
2.2. Spectral characterization
All the complexes 4 and 5 exhibited sharp singlet mNH stretches
The UV–Vis spectra of [(HL-NH)Ru(CO)Cl(PPh3)2] 4 and [(L-NH)
Ru(CO)(PPh3)2] 5 exhibited low energy absorption band near
within the range 3330–3353 cmꢀ1. This is consistent with the dis-
sociation of an amino proton of HL-NH2 since mNH of free ligands
2
appear as a twin band near 3455 and 3380 cmꢀ1 [30,31]. For the
complexes the mN
@
(1333–1432 cmꢀ1) shifted to lower energy
N
than the mN
@
N
(1458–1474 cmꢀ1) of the free ligands [27–32] indi-
cating the coordination of azo nitrogen. The mCO of [(HL-NH)Ru(-
CO)Cl(PPh3)2] and [(L-NH)Ru(CO)(PPh3)2] appeared as a singlet
within the range 1910–1930 cmꢀ1. The IR spectra of all the com-
plexes are given in Supplementary material (Figs. S7–S12) and data
are collected in Section 3.
The 1H NMR spectra of [(HL-NH)Ru(CO)Cl(PPh3)2], 4, complexes
exhibited N–H resonance as a broad singlet in the range d
5.37ꢀ5.57 for one equivalent proton signifying the dissociation
of one of the amino protons of HL-NH2 during complexation
[27,29–31]. A singlet near d 6.7 in the 1H NMR spectra of [(L2-
NH)Ru(CO)(PPh3)2] and [(L3-NH)Ru(CO)(PPh3)2] signified ortho-
metallation [27]. The N–H resonance has been overlapped by the
signals of other protons and therefore could not be identified
unequivocally even when the spectra drawn after shaking with
D2O. Only one N–H hydrogen could be located during X-ray struc-
ture determination of [(L3-NH)Ru(CO)(PPh3)2] (see below) is con-
sistent with the dissociation of one of the amino protons in the
complex.
Fig. 1. A representative UV–Vis spectra of [(HL1-NH)RuCOCl(PPh3)2] (- - -) and [(L1-
NH)RuCO(PPh3)2] (—).
Fig. 2. Molecular structure of [(HL3-NH)Ru(CO)Cl(PPh3)2] with atom numbering scheme. The hydrogen atoms excepting on N(1) of the amino groups have been omitted for
clarity.

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J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
2.3. Crystal and molecular structure of [(HL3-NH)Ru(CO)Cl(PPh3)2]
and [(L3-NH)Ru(CO)(PPh3)2]
(ꢀ1.25 Å) in free azo molecules [27]. These observations are in
support of backbone conjugation within the coordinated ligand
[27]. The quinonoid distortion in the phenyl ring (C1–C6) adjacent
to the chelate ring with four longer (ꢂ1.42 Å) and two shorter
(ꢂ1.35 Å) bonds, like other coordinated arylimines [30,31], is con-
sistent with delocalization [29–31]. The packing of the molecules
4c in crystals do not show any significant interaction either
amongst each other or with the benzene solvents molecules. The
solvents of crystallization, i.e. benzene are situated in the void
spaces of the lattice formed by the complex, 4c molecules. The
views of packing diagrams are given in Fig. S19 (Supplementary
material).
2.3.1. [(HL3-NH)Ru(CO)Cl(PPh3)2]
Suitable crystals of [(HL3-NH)Ru(CO)Cl(PPh3)2] 4c were grown
by slow diffusion of dichloromethane solution into petroleum
ether with few drops of benzene. A perspective view of the mole-
cule is shown in Fig. 2 and selected bond distances and angles
are collected in Table 1. The [(HL3-NH)Ru(CO)Cl(PPh3)2] 4c coordi-
nation sphere has distorted octahedral geometry. The monoanionic
(HL-NH)ꢀ ligands bind to the metal in an N,N-bidentate fashion
forming diazoketiminato chelate. One chloride, one CO and two
trans PPh3 ligands are present in the coordination sphere of
[(HL3-NH)Ru(CO)Cl(PPh3)2]. There is half benzene molecule per
asymmetric unit in the crystal lattice. The Ru–Cl, Ru–CO and Ru–
P bond lengths of [(HL3-NH)Ru(CO)Cl(PPh3)2] 4c are within the
normal range [22,23]. Only one hydrogen [H(1)] atom on N(1)
could be located from difference Fourier mapping, signifying disso-
ciation of the other amino proton consistent with the 1H NMR data
(vide infra). The C(1)–N(1) bond (1.30 Å) is shorter than C(7)–N(3)
single bond (1.43 Å) in the same molecule and similar to a imine
(–C@N–) length as a result of delocalization [30,31]. Nhe ruthe-
nium center is closer to azo nitrogen N(3) (2.09 Å) and the N(2)–
N(3) distance (1.30 Å) is longer than the azo (–N@N–) distance
2.3.2. [(L3-NH)Ru(CO)(PPh3)2]
Suitable crystals of [(L3-NH)Ru(CO)(PPh3)2] 5c were grown by
slow diffusion of dichloromethane solution into petroleum ether.
A perspective view of the molecule is shown in Fig. 3 and selected
bond distances and angles are collected in Table 1.
The Ru(CNN)(CO)(P)2 coordination sphere has distorted octahe-
dral geometry. The dianionic (L3-NH)2ꢀ ligand coordinates the
Ru(II) in a tridentate (C, N, N) fashion along with two mutually
trans PPh3 and a CO ligand. There is a CH2Cl2 molecule per asym-
metric unit in the crystal lattice. The Ru–C (aryl), Ru–C (carbonyl)
and Ru–P bond lengths of 5c are within the normal range [22,23].
Only one hydrogen [H(1)] atom could be located on N(1) from dif-
ference Fourier mapping, signifying dissociation of the other amino
proton. The C(1)–N(1) bond (1.32 Å) is shorter than C(6)–N(2) sin-
gle bond (1.37 Å) in the same molecule and similar to a imine
(>C@N–) length as a result of delocalization [30,31]. The quinonoid
distortion in the phenyl ring (C1–C6) adjacent to the five mem-
bered chelate with two shorter (av. ꢂ1.35 Å) and four longer (av.
ꢂ1.40 Å) bonds is also in accordance with the delocalization and
imine formation [27]. Thus in 5 the formation of five membered
azoimine chelate has been inferred. The packing of the molecules
5c in crystals do not show any significant interaction. The view
of packing diagram is given in Figs. S20 (Supplementary material).
Table 1
Selected bond distances (Å) and angles (°) for [(HL3-NH)Ru(CO)Cl(PPh3)2] and [(L3-
NH)Ru(CO)(PPh3)2].
[(HL3-NH)Ru(CO)Cl(PPh3)2]
Distances (Å)
Ru1–P1
Ru1–P2
Ru1–N1
Ru1–Cl1
N1–C1
N2–C6
C1–C2
C2–C3
Ru1–C13
2.430(2)
2.415(2)
2.055(6)
2.4330(18)
1.307(11)
1.354(12)
1.445(13)
1.348(15)
1.856(8)
N2–N3
Ru1–N3
C4–C5
C5–C6
O–C13
C3–C4
N3–C7
C1–C6
1.303(10)
2.091(5)
1.354(15)
1.428(13)
1.129(10)
1.394(18)
1.431(10)
1.448(14)
2.4. Electrochemistry
Angles (°)
P1–Ru1–P2
P1–Ru1–N1
P1–Ru1–N3
N1–Ru1–Cl1
P1–Ru1–C13
P2–Ru1–N3
N1–Ru1–C13
P2–Ru1–C13
173.90(7)
85.78(19)
94.25(18)
82.8(2)
Ru1–N3–N2
N3–Ru1–C13
N3–N2–C6
N2–N3–C7
P2–Ru1–N1
Cl1–Ru1–C13
N1–Ru1–N3
N2–C6–C1
127.3(5)
96.0(3)
126.1(6)
109.2(5)
90.52(19)
94.1(2)
[(HL-NH)Ru(CO)Cl(PPh3)2], 4, complexes exhibited one electron
quasireversible oxidative cyclic voltammetric responses with the
E1/2 in the range of 0.56–0.70 V versus SCE in dichloromethane
solution. On the other hand [(L-NH)Ru(CO)(PPh3)2], 5, complexes
displayed reversible oxidative couples within 0.05–0.16 V versus
SCE in dichloromethane–acetonitrile mixed solvent. The oxidations
have been assigned according to the couple of Eqs. (2) and (3),
where [(L-NH)Ru(CO)(PPh3)2]+ and [(HL-NH)Ru(CO)Cl(PPh3)2]+
are the Ru(III) analogs of [(L-NH)Ru(CO)(PPh3)2] and [(HL-NH)Ru
(CO)Cl(PPh3)2]. Representative cyclic voltammograms of [(L1-NH)
Ru(CO)(PPh3)2] and [(HL1-NH)Ru(CO)Cl(PPh3)2] is shown in Fig. 4
and all other cyclic voltammograms are given in Supplementary
material (Figs. S21–S24). Further the relative positions of MLCT
absorptions in low energy region, ꢂ800 nm and ꢂ600 nm for
[(L-NH)Ru(CO)(PPh3)2] and [(HL-NH)Ru(CO)Cl(PPh3)2], respec-
tively, were consistent with the metal oxidation potentials.
93.1(2)
90.41(18)
176.8(3)
90.3(2)
87.1(3)
127.0(8)
[(L3-NH)Ru(CO)(PPh3)2]
Distances (Å)
Ru1–P1
Ru1–P2
Ru1–N2
Ru1–C13
N1–C1
N2–C6
C1–C2
C2–C3
2.3642(11)
2.3624(12)
2.064(3)
1.859(3)
1.326(6)
1.379(5)
1.442(7)
1.359(7)
1.388(10)
Ru1–Cl2
Ru1–N1
C4–C5
C5–C6
O–C13
N2–N3
N3–C7
C1–C6
2.063(4)
2.164(4)
1.376(8)
1.407(6)
1.155(5)
1.286(5)
1.399(5)
1.419(7)
C3–C4
Angles (°)
½ðL-NHÞRuðCOÞðPPh3Þ ꢁ ꢀ e ! ½ðL-NHÞRuðCOÞðPPh3Þ ꢁþ
ð2Þ
P1–Ru1–P2
P1–Ru1–N1
P1–Ru1–N2
P1–Ru1–C12
P1–Ru1–C13
P2–Ru1–N2
P2–Ru1–C12
P2–Ru1–C13
N1–Ru1–N2
N1–Ru1–C12
N1–Ru1–C13
178.40(3)
89.31(11)
90.08(12)
91.01(12)
89.89(13)
91.45(12)
88.89(12)
88.55(13)
76.26(14)
153.30(13)
107.45(15)
Ru1–N2–N3
Ru1–N2–C6
N3–N2–C6
N2–N3–C7
P2–Ru1–N1
N2–C6–C1
121.7(2)
117.8(3)
120.5(3)
110.1(3)
91.49(11)
113.3(3)
119.1(4)
77.04(13)
176.29(15)
99.25(15)
2
2
½ðHL-NHÞRuðCOÞClðPPh3Þ ꢁ ꢀ e ! ½ðHL-NHÞRuðCOÞClðPPh3Þ ꢁþ ð3Þ
2
2
2.5. Transformation of ketones to 20 – alcohols via hydrogen transfer
reactions
N1–C1–C6
N2–Ru1–C12
N2–Ru1–C13
C12–Ru1–C13
Homogenous hydrogenation of organic compounds via catalytic
hydrogen transfer reactions have been under investigation in re-
cent years using Ruthenium catalyst [25,26]. This information

J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
3405
Fig. 3. Molecular structure of [(L3-NH)Ru(CO)(PPh3)2] with atom numbering scheme. The hydrogen atoms excepting on N(1) of the amino groups have been omitted for
clarity.
Fig. 4. Cyclic voltammograms of [(L1-NH)Ru(CO)(PPh3)2] (a) and [(HL1-NH)Ru(CO)Cl(PPh3)2] (b).
encouraged us to study the activity of [(L-NH)Ru(CO)(PPh3)2] and
[(HL-NH)Ru(CO)Cl(PPh3)2] toward the transfer hydrogenation of
representative aliphatic and aromatic ketones in presence of KOH
and isopropyl alcohol promoters.
The conversion of ketones to corresponding alcohols were stud-
ied adding small amount of [(L1-NH)Ru(CO)(PPh3)2], 5a, or [(HL1-
NH)Ru(CO)Cl(PPh3)2], 4a, in the reaction mixture Eq. (4). The re-
sults of transformations are given in Table 2. However, at the end
of each reaction neither we could isolate the original ruthenium
complexes (4a or 5a) nor did we obtain only one complex as the
major one suitable for characterization. Since the formation of spe-
cies other than 4a or 5a could not be excluded during the transfor-
mations, the original complexes (4a and 5a) were not considered to
be the only catalytically active species. The 1H NMR and IR spectra
of the residues obtained after catalytic reactions were identical sig-
nifying formation of identical catalytically active species in both
the cases.
OH
O
0.0013 mmol
4a or 5a, KOH
ð4Þ
R/
2-propanol
R
R
R/

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J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
Table 2
Transformation of ketones to 20 – alcohols via hydrogen transfer reactions for [(HL1-NH)Ru(CO)Cl(PPh3)2] and [(L1-NH)Ru(CO)(PPh3)2].
Entry
1
Substrate
Product
Time (h)
Isolated yield (%)
Complex 4a
90
Complex 5a
1
90
O
OH
2
3
1.5
1.5
82
75
70
75
O
OH
O
OH
MeO
Me
MeO
4
5
1.5
1.5
78
70
75
65
O
OH
Me
Me
Me
O
O
OH
OH
6
7
1.5
1.5
73
68
71
65
Cl
Cl
O
OH
Cl
O
Cl
OH
8
9
1.5
1.5
45
42
43
44
O
OH
All the reactions were carried out in ambient condition unlike
the reported reactions using other ruthenium orthometallated com-
plexes, incorporating azo ligands, as catalyst [25,26]. A series of
blank reactions were carried out in absence of complex 4a and 5a
and in presence of only ligand or RuCl3ꢃ3H2O. This ascertained the
necessity of the complex during the reaction. The yields of the alco-
hols obtained from all the ketones were determined after isolation.
kin–Elmer L120-00A FT-IR spectrometer with the samples pre-
pared as KBr pellets. Electronic spectra were recorded on a
Shimadzu UV-2401 PC spectrophotometer. 1H NMR spectra were
obtained on Brucker DPX 400 and Brucker 500 RPX NMR spectrom-
eters in CDCl3 using TMS as the internal standard. Electrochemical
measurements were made under dinitrogen atmosphere using a
PAR model VARSASTAT-II potentiostat. A platinum disc working
electrode, a platinum wire auxiliary electrode and an aqueous sat-
urated calomel reference electrode (SCE) were used in a three-elec-
trode configuration. Electrochemical data were collected at 298 K
and are uncorrected for junction potentials.
3. Experimental
3.1. Materials
3.3. Synthesis of complexes
The solvents used in the reactions were of reagent grade (E.
Marck, Kolkata, India) and were purified and dried by reported pro-
cedure [33]. Ruthenium trichloride was purchased from Johnson
Matthey, India. Ru(CO)3(PPh3)2 and RuH(CO)Cl(PPh3)3 were syn-
thesized following the reported procedure [34]. The ligands 2-
(phenylazo)aniline (HL1-NH2), 2-(p-tolylazo)aniline (HL2-NH2),
and 2-(p-chlorophenylazo)aniline (HL3-NH2) were prepared fol-
lowing the reported procedures [30,31].
3.3.1. [(HL1-NH)Ru(CO)Cl(PPh3)2]
HL1-NH2 (0.043 g, 0.22 mmol) was dissolved in toluene (40 mL)
and to it were added RuH(CO)Cl(PPh3)3 (0.021 g, 0.22 mmol). The
mixture was then refluxed for 3 h, when a bluish solution was ob-
tained. Evaporation of these solutions afforded a dark solid which
was washed with hexane several times to remove excess ligands.
The blue solid, obtained upon evaporation of the solvent, was
recrystallized from dichloromethane–petroleum ether to afford
[(HL1-NH)Ru(CO)Cl(PPh3)2] as a crystalline dark solid. Isolated
yield: 0.117 g (60%). Anal. Calc. for RuC49H40N3ClOP2 (885.46): C,
66.46; H, 4.55; N, 4.75. Found: C, 66.62; H, 4.42; N, 4.68%. UV–
3.2. Physical measurements
Microanalysis (C, H, N) was performed using a Perkin–Elmer
240C elemental analyzer. Infrared spectra were recorded on a Par-
Vis spectrum (CH2Cl2) kmax
(e,
Mꢀ1 cmꢀ1) = 600 (3300), 400

J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
3407
(3750), 320 (11 175), 265 (34 360). IR (KBr):
(C@O), 1615 (C@N), 1432 (N@N) cmꢀ1
d = 7.35–7.40 (m, 12H), 7.24–7.27 (m, 6H), 7.15–7.19 (m, 12H),
6.98 (d, 1H), 6.87 (t, 1H), 6.71 (t, 2H), 6.47 (t, 1H), 6.01 (t, 2H),
5.63 (d, 1H), 5.47 (s, NH). E1/2 [V]: 0.56.
m
= 3335 (NH), 1934
Vis spectrum (CH2Cl2) kmax
(
e
,
Mꢀ1 cmꢀ1) = 800 (3430), 410
.
1H NMR (CDCl3):
(4830), 340 (10 520), 270 (26 030). IR (KBr):
m = 3333 (NH) 1919
(C@O), 1598 (C@N), 1434 (N@N) cmꢀ1 1H NMR (CDCl3): d = 7.44
.
(b, 12H), 7.27 (t, 6H), 7.21 (t, 12H), 6.75 (d, 1H), 6.71 (d, 1H),
6.38 (d, 1H), 6.08 (t, 1H), 5.91 (d, 1H), 5.40 (d, 1H), 5.33 (d, 1H).
E1/2 [V]: 0.05.
3.3.2. [(HL2-NH)Ru(CO)Cl(PPh3)2] and [(HL3-NH)Ru(CO)Cl(PPh3)2]
Complex [(HL2-NH)Ru(CO)Cl(PPh3)2] and [(HL3-NH)Ru(CO)-
Cl(PPh3)2] were prepared and purified by following a similar proce-
dure as described for [(HL1-NH)Ru(CO)Cl(PPh3)2] using ligand
HL2-NH2 and HL3-NH2 in place of HL1-NH2. Isolated yield:
0.119 g, (60%) and 0.131 g (65%), respectively.
3.3.4. [(L2-NH)Ru(CO)(PPh3)2 and (L3-NH)Ru(CO)(PPh3)2]
Complex [(L2-NH)Ru(CO)(PPh3)2] and [(L3-NH)Ru(CO)(PPh3)2]
were prepared and purified following a similar procedure as de-
scribed for [(L1-NH)Ru(CO)(PPh3)2] using ligand HL2-NH2 and
HL3-NH2 in place of HL1-NH2. Yield: 0.114 g, (60%) and 0.101 g
(55%), respectively.
Anal. Calc. for RuC50H42N3OClP2 (899.49): C, 66.76; H, 4.70; N,
4.68. Found: C, 66.61; H, 4.552; N, 4.78%. UV–Vis spectrum
Anal. Calc. for RuC50H41N3OP2 (863.03): C, 69.58; H, 4.78; N,
4.88. Found: C, 69.62; H, 4.62; N, 4.75%. UV–Vis spectrum (CH2Cl2)
(CH2Cl2) kmax
(10 600), 265 (34 600). IR (KBr):
(C@N), 1432 (N@N) cmꢀ1 1H NMR (CDCl3): d = 7.35–7.40 (m,
(e,
Mꢀ1 cmꢀ1) = 600 (3030), 400 (4200), 325
m
= 3333 (NH), 1928 (C@O), 1615
kmax
(29 100). IR (KBr):
(N@N) cmꢀ1 1H NMR (CDCl3): d = 7.38–7.45 (m, 12H), 7.23–7.28
(e
, Mꢀ1 cmꢀ1) = 800 (3850), 420 (6780), 340 (12 360), 270
.
m = 3353 (NH), 1910 (C@O), 1596 (C@N), 1433
12H), 7.23–7.28 (m, 6H), 7.15–7.19 (m, 12H), 6.97 (d, 1H), 6.45–
6.52 (m, 3H), 6.00 (t, 2H), 5.89 (d, 2H), 5.64 (d, 1H), 5.37 (s, NH),
2.17 (s, 3H). E1/2 [V]: 0.62.
.
(m, 6H), 7.18–7.22 (m, 12H), 6.81 (d, 1H), 6.63 (s, 1H), 6.25 (d,
1H), 6.09 (t, 1H), 5.86 (d, 1H), 5.42 (d, 1H), 5.28 (b, 1H), 1.88 (s,
3H). E1/2 [V]: 0.10.
Anal. Calc. for RuC49H39N3OClP2 (919.91): C, 63.97; H, 4.27; N,
4.58. Found: C, 64.18; H, 4.21; N, 4.68%. UV–Vis spectrum (CH2Cl2)
Anal. Calc. for RuC49H38N3ClOP2 (883.45): C, 66.61; H, 4.33; N,
4.76. Found: C, 66.73; H, 4.42; N, 4.62%. UV–Vis spectrum (CH2Cl2)
kmax
(30 400). IR (KBr):
(N@N) cmꢀ1 1H NMR (CDCl3): d = 7.41–7.44 (m, 12H), 7.25–7.28
(e
, Mꢀ1 cmꢀ1) = 600 (3130), 400 (3140), 325 (11 150), 270
m
= 3330 (NH), 1933 (C@O), 1614 (C@N), 1433
kmax
(32 020). IR (KBr):
(N@N) cmꢀ1 1H NMR (CDCl3): d = 7.40–7.44 (m, 12H), 7.28–7.31
(e
, Mꢀ1 cmꢀ1) = 800 (4680), 420 (6380), 350 (13 410), 270
.
m = 3352 (NH), 1920 (C@O), 1598 (C@N), 1433
(m, 6H), 7.15–7.20 (m, 12H), 6.95 (d, 1H), 6.64 (d, 2H), 6.46 (t,
.
1H), 6.02 (t, 1H), 5.97 (d, 2H), 5.57 (s, NH). E1/2 [V]: 0.70.
(m, 6H), 7.22–7.25 (m, 12H), 6.75 (d, 1H), 6.71 (s, 1H), 6.38 (d,
1H), 6.08 (t, 1H), 5.91 (d, 1H), 5.40 (d, 1H), 5.33 (d, 1H). E1/2 [V]:
0.15.
3.3.3. [(L1-NH)Ru(CO)(PPh3)2]
HL1-NH2 (0.043 g, 0.22 mmol) was dissolved in toluene
(40 mL) and to it were added Ru(CO)3(PPh3)2 (0.0156 g,
0.22 mmol). The mixture was then refluxed for 4 h, when a green
solution was obtained. Evaporation of these solutions afforded a
dark solid which was washed with hexane several times to re-
move excess ligands, and then it was purified by thin layer chro-
matography on silica plate with toluene:acetonitrile (90:10) as
the eluent. A yellowish pink band separated and the complex
was extracted from it with methanol turns to green solution.
The pure green crystals, obtained upon evaporation of the solvent,
was recrystallized from dichloromethane–petroleum ether to af-
ford [(L1-NH)Ru(CO)(PPh3)2] as a crystalline green solid. Isolated
yield: 0.093 g (50%). Anal. Calc. for RuC49H39N3OP2 (849): C,
69.32; H, 4.62; N, 4.96. Found: C, 69.15; H, 4.53; N, 5.12%. UV–
3.4. Transformation of ketones to 20 – alcohols via hydrogen transfer
reactions
A mixture containing ketones (0.071 g, 3.9 mmol), the ruthe-
nium complex (0.0012 g, 0.0013 mmol) and (0.0036 g,
0.0625 mmol) of KOH was heated to reflux in 10 mL of i-PrOH for
appropriate period of time as mentioned in Table 2. The complex
was removed as precipitate from the reaction mixture by the addi-
tion of diethyl ether followed by filtration and subsequent neutral-
ization with 5 mL of 1 (M) HCl. Then the ether layer was passed
through a short path of silica gel and purified by preparative chro-
matography. The hydrogenated products were characterized by
matching the UV–Vis and IR spectra of authentic samples.
Table 3
Crystallographic data for [(HL3-NH)Ru(CO)Cl(PPh3)2] and [(L3-NH)Ru(CO)(PPh3)2].
[(HL3-NH)Ru(CO)Cl-(PPh3)2]
[(L3-NH)Ru(CO)(PPh3)2]
Chemical formula
Formula weight
Space group
Crystal system
a (Å)
C49H39Cl2N3OP2Ruꢃ0.5(C6H6)
C49H38ClN3OP2RuꢃCH2Cl2
958.80
P21/n
968.21
ꢀ
P1
monoclinic
12.3751(16)
20.948(3)
17.946(2)
90
106.849(4)
90
0.71073
4452.5(10)
4
triclinic
12.2334(6)
13.1599(7)
17.3881(9)
68.127(3)
89.056(3)
62.302(3)
0.71073
2257.9(2)
2
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
k (Å)
V (Å3)
Z
Temperature (K)
293
1.430
0.587
293
1.424
0.636
Dcalc (g cmꢀ3
)
l
(mmꢀ1
)
R1
wR2
0.0393
0.1051
3406/2550
1.06
0.0510
0.1621
11 005/7853
1.02
Unique reflections [I > 2
Goodness-of-fit (GOF)
r(I)]

3408
J.L. Pratihar et al. / Journal of Organometallic Chemistry 694 (2009) 3401–3408
[4] T. Ren, Chem. Rev. 108 (2008) 4185–4207.
4. Crystallography
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Spek, Dalton Trans. (2004) 448–455.
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(2006) 10882–10894.
The suitable X-ray crystals of [(L3-NH)Ru(CO)(PPh3)2] and
[(HL3-NH)Ru(CO)Cl(PPh3)2] were obtained by slow diffusion of a
dichloromethane solution into petroleum ether with few drop of
benzene at 298 K. Data were collected by
Bruker Smart CCD diffractometer with Mo K
mated by graphite crystal. Structure solution was done by direct
method with SHELXS-97 program [35,36]. Full matrix least square
refinements on F2 were performed using SHELXL-97 program
[35,36]. All non-hydrogen atoms were refined anisotropically using
[7] A.C.G. Hotze, A.H. Velders, F. Ugozzoli, M. Biagini-Cingi, A.M. Manotti-Lanfredi,
J.G. Haasnoot, J. Reedijk, Inorg. Chem. 39 (2000) 3838–3844.
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Chem. 39 (2000) 2966–2967.
x
a
-scan technique on a
radiation monochro-
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Haasnoot, J. Reedijk, Inorg. Chem. 43 (2004) 4935–4943.
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Chakravorty, Inorg. Chem. 25 (1986) 1715–1721.
reflections I > 2r(I). All hydrogens were included at calculated
positions excepting H1 for both the complexes. These were located
by difference Fourier mapping and refined isotropically. The data
collection parameters and relevant crystal data are collected in
Table 3.
[15] G.K. Lahiri, S. Bhattacharya, M. Mukherjee, A.K. Mukherjee, A. Chakravorty,
Inorg. Chem. 26 (1987) 3359–3365.
[16] C. Das, A.K. Ghosh, C.-H. Hung, G.-H. Lee, S.-M. Peng, S. Goswami, Inorg. Chem.
41 (2002) 7125–7135.
Acknowledgments
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(2003) 198–204.
[18] S. Samanta, P. Singh, J. Fiedler, S. Záliš, W. Kaim, S. Goswami, Inorg. Chem. 47
(2008) 1625–1633.
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4816.
We are thankful to the DST (New Delhi) for funding under DST-
SERC project (SR/S1/IC-0026/2007). J.P. is thankful to the CSIR
(New Delhi) for his fellowship (No. 09/106(0097)2K8-EMR-I). The
necessary laboratory and infrastructural facility are provided by
the Department of Chemistry, University of Kalyani. The support
of DST under FIST and UGC SAP program to the Department of
Chemistry, University of Kalyani is acknowledged.
Appendix A. Supplementary material
[24] T.K. Misra, D. Das, C. Sinha, P. Ghosh, C.K. Pal, Inorg. Chem. 37 (1998) 1672–
1678.
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4821.
[28] J.L. Pratihar, N. Maiti, S. Chattopadhyay, Inorg. Chem. 44 (2005) 6111–6114.
[29] J.L. Pratihar, B. Shee, P. Pattanayak, D. Patra, A. Bhattacharyya, V.G. Puranik,
C.H. Hung, S. Chattopadhyay, Eur. J. Inorg. Chem. 1 (2007) 4272–4281.
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Eur. J. Inorg. Chem. (2007) 4263–4271.
CCDC 724146 and 724145 contain the supplementary crystallo-
graphic data for [(HL3-NH)Ru(CO)Cl(PPh3)2] (4c) and [(L3-NH)Ru
(CO)(PPh3)2] (5c). These data can be obtained free of charge from
The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.
uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.06.038.
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