[RuCl2(PPh3)(PNN′)] complexes as efficient catalysts in transfer hydrogenation of ketones

Article abstract of DOI:10.1021/om700647k

Ruthenium complexes of the general formula [RuCl₂(PPh ₃)(PNN′)] have been obtained from tridentate PNN′ ligands containing phosphine (P), amine or imine (N), and pyridyl donor groups (N′). The imino ligand Ph₂P(0,0′-C₆H ₄CH=NCH₂C₅H₄N) (a) has been synthesized from Ph₂P(2-C₆H₄CHO) and 2-(aminomethyl)pyridine, whereas amino Ph₂P(o,o′-C ₆H₄CH₂NHCH₂C₅H ₄N) (b) is prepared by the reduction of a with NaBH₄. The complexes TrQnS-[RuCl₂(PPh₃)(PNN′)] [PNN′ = b, (1); a, (2)] containing a fivemembered NN′ cycle have been isolated in high yield by the reaction of RuCl₂(PPh₃)₃ with b and a, respectively. By the same route and using the ligand Ph ₂P(0,0′-C₆H₄CH=NCH₂CH ₂C₅H₄N)] (c), the complex cis-[RuCl ₂(PPh₃)(c)] (3) was isolated, and it displays a different stereochemistry as a result of the different size of the tridentate ligand. For the amino derivative 1, an X-ray diffraction experiment was carried out. Treatment of [RuHCl(PPh₃)₃] with the ligands a or b leads to the monohydride complexes trans-[RuHCl(PPh₃)(PNN′)] [PNN′ = b, (4); a, (5)]. Complexes 1-5 have been proven to catalyze the transfer hydrogenation of linear, cyclic, and aromatic ketones to secondary alcohols in 2-propanol at reflux and in the presence of (CH₃) ₂CHONa with a very high rate (TOF values up to 250 000 h ^-1)- The trans derivatives 1 and 2 containing the amino and imino functions catalyze the reduction of acetophenone with the same activity (TOF = 190 000 and 185 000 h^-l, respectively), suggesting that the C=N group is reduced during catalysis. A lower activity has been observed for complexes 3-5.

Full text of DOI:10.1021/om700647k

5636
Organometallics 2007, 26, 5636-5642
[RuCl2(PPh3)(PNN′)] Complexes as Efficient Catalysts in Transfer
Hydrogenation of Ketones
Alessandro Del Zotto,*,† Walter Baratta,*,† Maurizio Ballico,† Eberhardt Herdtweck,‡ and
Pierluigi Rigo†
Dipartimento di Scienze e Tecnologie Chimiche, UniVersita` di Udine, Via Cotonificio 108,
I-33100 Udine, Italy, and Department Chemie, Lehrstuhl fu¨r Anorganische Chemie, Technische UniVersita¨t
Mu¨nchen, Lichtenbergstrasse 4, D-85747 Garching, Germany
ReceiVed June 27, 2007
Ruthenium complexes of the general formula [RuCl2(PPh3)(PNN′)] have been obtained from tridentate
PNN′ ligands containing phosphine (P), amine or imine (N), and pyridyl donor groups (N′). The imino
ligand Ph2P(o,o′-C6H4CHdNCH2C5H4N) (a) has been synthesized from Ph2P(2-C6H4CHO) and 2-(ami-
nomethyl)pyridine, whereas amino Ph2P(o,o′-C6H4CH2NHCH2C5H4N) (b) is prepared by the reduction
of a with NaBH4. The complexes trans-[RuCl2(PPh3)(PNN′)] [PNN′ ) b, (1); a, (2)] containing a five-
membered NN′ cycle have been isolated in high yield by the reaction of RuCl2(PPh3)3 with b and a,
respectively. By the same route and using the ligand Ph2P(o,o′-C6H4CHdNCH2CH2C5H4N)] (c), the
complex cis-[RuCl2(PPh3)(c)] (3) was isolated, and it displays a different stereochemistry as a result of
the different size of the tridentate ligand. For the amino derivative 1, an X-ray diffraction experiment
was carried out. Treatment of [RuHCl(PPh3)3] with the ligands a or b leads to the monohydride complexes
trans-[RuHCl(PPh3)(PNN′)] [PNN′ ) b, (4); a, (5)]. Complexes 1-5 have been proven to catalyze the
transfer hydrogenation of linear, cyclic, and aromatic ketones to secondary alcohols in 2-propanol at
reflux and in the presence of (CH3)2CHONa with a very high rate (TOF values up to 250 000 h-1). The
trans derivatives 1 and 2 containing the amino and imino functions catalyze the reduction of acetophenone
with the same activity (TOF ) 190 000 and 185 000 h-1, respectively), suggesting that the CdN group
is reduced during catalysis. A lower activity has been observed for complexes 3-5.
phine),3 [RuCl2(PN)2],3a,4 [RuCl(p-cymene)(PN)][BF4] (PN )
Introduction
phosphole-pyridine),5 [RuCl(p-cymene)(NN)][BF4],6 [RuCl2(P)-
(NPN)],7 [RuCl2(NPN)],8 [RuCl2(P)(NNN)]9 (NPN and NNN
) oxazoline based ligands), and [RuCl2(PNNP)] (PNNP )
diphosphine/diamine ligand).10 A particularly active complex
The catalytic transfer hydrogenation of polarized unsaturated
compounds using 2-propanol or formic acid as the hydrogen
source is a widely investigated reaction that is promoted by
different transition metal complexes.1 Employment of highly
active catalytic systems makes this approach quite attracting
for the preparation of alcohols, rivaling the well-established
hydrogenation process, which necessitates hydrogen under
pressure. The most active systems are based on Ru, Rh, and Ir
bearing nitrogen- and/or phosphorus-containing ligands, which
allow the easy formation of catalytically active hydride species.
(2) (a) de Araujo, M. P.; de Figueiredo, A. T.; Bogado, A. L.; Von
Poelhsitz, G.; Ellena, J.; Castellano, E. E.; Donnici, C. L.; Comasseto, J.
V.; Batista, A. A. Organometallics 2005, 24, 6159. (b) Rautenstrauch, V.;
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Lindner, E.; Jiang, Z. J.; Schuring, V. Z. Anorg. Allg. Chem. 2003, 629,
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2003, 27, 414. (b) Crochet, P.; Gimeno, J.; Garc´ıa-Granda, S.; Borge, J.
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Org. Chem. 1997, 62, 6104. (d) Nishibayashi, Y.; Takei, I.; Uemura, S.;
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Matoba, K.; Nishibayashi, Y.; Hidai, M.; Uemura, S. J. Organomet. Chem.
1999, 572, 163.
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Ruthenium complexes containing suitable combinations of
P and N or mixed PN ligands have proven to be highly efficient
catalysts for the hydrogenation and transfer hydrogenation of
carbonyl compounds. Thus, bi-, tri-, and tetradentate achiral and
chiral ligands have successfully been used to prepared five- and
six-coordinate complexes for the transfer hydrogenation, namely,
[RuCl2(P)2(NN)] and [RuCl2(PP)(NN)] (P ) phosphine; PP )
diphosphine; NN ) diamine, dipyridine),2 [RuCl2(P)(PN)] (PN
) amino- or imino-phosphine and oxazolinylferrocenylphos-
* Corresponding author. E-mail: alessandro.delzotto@uniud.it (A.D.Z.)
and inorg@uniud.it (W.B.).
(7) Braunstein, P.; Fryzuk, M. D.; Naud, F.; Rettig, S. J. J. Chem. Soc.,
Dalton Trans. 1999, 589.
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2000, 19, 2676.
† Universita` di Udine.
‡ Technische Universita¨t Mu¨nchen.
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Chem. Soc. ReV. 2006, 35, 237. (b) Gladiali, S.; Alberico, E. Chem. Soc.
ReV. 2006, 35, 226. (c) Ikariya, T.; Murata, K.; Noyori, R. Org. Biomol.
Chem. 2006, 4, 393. (d) Clapham, S. E.; Hadzovic, A.; Morris, R. H. Coord.
Chem. ReV. 2004, 248, 2201. (e) Ba¨ckvall, J. E. J. Organomet. Chem. 2002,
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10.1021/om700647k CCC: $37.00 © 2007 American Chemical Society
Publication on Web 10/03/2007

[RuCl2(PPh3)(PNN′)] Complexes as Efficient Catalysts
Organometallics, Vol. 26, No. 23, 2007 5637
is [RuCl2(P)(PNO)],11 which contains a mixed tridentate ligand
with a labile oxygen donor atom. In addition, enantioselective
catalytic systems have been obtained by the in situ reaction of
ruthenium precursors (i.e., [RuCl2(PPh3)3], [RuCl2(η6-arene)]2,
or [RuCl2(DMSO)4]) with the NNN,12 NPN,13 PNP,14 PNN,15
and PNO16 ligands.
The complexes Ru(η6-arene) containing diamines or ami-
noalcohols, discovered by Noyori and co-workers, are highly
enantioselective and show a high rate of reaction due to the
presence of primary amine ligands.17 Recently, we have found
that highly active ruthenium catalysts are obtained using
2-(aminomethyl)pyridine (ampy) as the bidentate NN′ ligand
(ligand acceleration effect).18 Particularly attractive are the
complexes of the general formula [RuCl2(PP)(ampy)], which
are active for both transfer hydrogenation and hydrogenation.19
As an extension of this chemistry with ampy, we have prepared
terdentate complexes [RuCl(CNN)(PP)] (HCNN ) 6-(aryl)-2-
pyridinemethanamines), which display the highest rate in the
transfer hydrogenation of ketones (turnover frequency (TOF)
up to 106 h-1).20 In all these systems containing amine ligands,
the presence of the NH2 function has been proven to be crucial
for achieving a highly efficient transfer hydrogenation of ketones
(bifunctional catalysis). According to the studies of Noyori and
co-workers on the [RuCl2(PNNP)] systems, the imino derivatives
display a very low activity as compared to the amino
analogues.10a,c,21 By contrast, catalytic studies performed by
Gimeno and co-workers on [RuCl2(P)(PN)]3b show that amino
and imino derivatives have the same activity.
Figure 1.
Figure 2.
Furthermore, under analogous experimental conditions, the
imine and amine derivatives display the same catalytic activity.
Results and Discussion
Synthesis and Characterization of Ligands and Com-
plexes. The tridentate PNN′ ligands (N ) imine or amine donor
and N′ ) pyridine) employed in this work show a combination
of triphenylphosphine and ortho substituted pyridines with a
C1 or C2 chain and linked through an imine or amine moiety
(Figure 2).
Similar to the synthesis of c,22 the ligand a was prepared by
treatment of 2-(diphenylphosphino)benzaldehyde with ampy in
toluene at reflux (Scheme 1).
It should be noted that few rhodium complexes have been
described with a, but this compound was not characterized.23
The amino PNN′ ligand b was isolated in good yield by
reduction of the in situ formed a, prepared in methanol in
the presence of Na2SO4 with NaBH4 at room temperature
(Scheme 1).
We describe here the synthesis and characterization of the
complexes 1-5 of the general formula [RuClX(PPh3)(PNN′)]
(X ) Cl, H), bearing tridentate ligands showing phosphine,
imino versus amino and pyridine donors, obtained from Ph2P(2-
C6H4CHO) and ampy or 2-(aminoethyl)pyridine (Figure 1).
These complexes in a basic 2-propanol solution at reflux
efficiently catalyze the transfer hydrogenation of numerous
ketones with a very high rate (TOF up to 250 000 h-1).
The thermally stable complex trans-[RuCl2(PPh3)(a)] (1) was
easily synthesized by treatment of [RuCl2(PPh3)3] with 1.1 equiv
of a in dichloromethane at room temperature for 1 h (eq 1).
(11) (a) Yang, H.; Lugan, N.; Mathieu, R. C. R. Acad. Sci., Ser. IIc:
Chim. 1999, 2, 251. (b) Yang, H.; Alvarez-Gressier, M.; Lugan, N.; Mathieu,
R. Organometallics 1997, 16, 1401. (c) Yang, H.; Alvarez, M.; Lugan, N.;
Mathieu, R. J. Chem. Soc., Chem. Commun. 1995, 1721.
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K.; Bitterlich, B.; Junge, K.; Erre, G.; Beller, M. AdV. Synth. Catal. 2007,
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Asymmetry 2003, 14, 1467.
The 31P{1H} NMR spectrum of 1 in the CD2Cl2 solution
shows two doublets at δ 46.6 and 41.8 with 2J(PP) ) 29.6 Hz,
indicating a cis arrangement of the two phosphorus atoms.24
The 1H NMR signals for the methylene groups appear at δ 4.61,
4.46, 4.09, and 3.77, whereas in the 13C{1H} spectrum, the two
CH2 groups are at δ 60.2 and 53.8 (d, J(CP) ) 5.1 Hz), the
latter attributable to the carbon bound to the phenyl ring. The
IR spectrum of complex 1 shows a single νRu-Cl band at 321
cm-1, which supports a trans arrangement of the Cl atoms. The
molecular structure of 1 was definitively confirmed by an X-ray
(17) (a) Yamakawa, M.; Ito, H.; Noyori, R. J. Am. Chem. Soc. 2000,
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S.; Fujii, A.; Inoue, S.; Ikariya, T.; Noyori, R. Chem. Commun. 1996, 233.
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P. J. Organomet. Chem. 2005, 690, 5570. (b) Baratta, W.; Del Zotto, A.;
Esposito, G.; Sechi, A.; Toniutti, M.; Zangrando, E.; Rigo, P. Organome-
tallics 2004, 23, 6264. (c) Baratta, W.; Da Ros, P.; Del Zotto, A.; Sechi,
A.; Zangrando, E.; Rigo, P. Angew. Chem., Int. Ed. 2004, 43, 3584.
(19) (a) Baratta, W.; Herdtweck, E.; Siega, K.; Toniutti, M.; Rigo, P.
Organometallics 2005, 24, 1660. (b) Ohkuma, T.; Sandoval, C. A.;
Srinivasan, R.; Lin, Q.; Wei, Y.; Mun˜iz, K.; Noyori, R. J. Am. Chem. Soc.
2005, 127, 8288.
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5638 Organometallics, Vol. 26, No. 23, 2007
Del Zotto et al.
The reaction between [RuCl2(PPh3)3] and appropriate imino
PNN′ ligand in toluene at 90 °C afforded the six-coordinate
complexes trans-[RuCl2(PPh3)(PNN′)] [PNN′ ) a, (2); c, (3)],
isolated in high yield (Scheme 2).
The 31P{1H} NMR spectra of 2 in CD2Cl2 solution shows
two doublets at δ 33.2 and 53.2 [2J(PP) ) 28.3 Hz], whereas
the resonances for 3 are at δ 31.5 and 49.4 [2J(PP) ) 29.1 Hz],
indicating a cis P-Ru-P arrangement. In the 1H NMR spectra
of complexes 2 and 3, the signal of the HCdN proton at δ ca.
8.8 shows 4J(P,H) of 8.2 and 7.1 Hz, respectively, as established
by heteronuclear 31P-1H correlation. These values are in accord
with a mutual trans arrangement of the imine nitrogen and
PPh3.29 As a matter of fact, in the related square-planar
complexes [MCl(c)]PF6 (M ) Pd or Pt), in which the imine
moiety is cis to the phosphorus atom, almost negligible 4J(P,H)
values for the HCdN proton (1.7 and 0.5 Hz, respectively) have
been observed.30 The IR spectrum of 2 exhibits a single Ru-
Cl stretching mode at 320 cm-1, indicating that this species is
isostructural with 1. On the contrary, two bands of comparable
intensity at 312 and 320 cm-1 are observed for 3, in agreement
with a cis Cl-Ru-Cl arrangement. Therefore, while in com-
plexes 1 and 2 the shorter tridentate ligand is mer coordinated,
complex 3 shows a different stereochemistry with the longer
ligand c displaying a fac arrangement. The vinylidene
Figure 3. Ball-and-stick model25,26 of 1 in the solid state. Selected
bond lengths (Å): Ru-Cl1 2.413(2), Ru-Cl2 2.391(2), Ru-P1
2.297(2), Ru-P2 2.321(2), Ru-N1 2.170(5), Ru-N8 2.148(5),
N8-C7 1.478(9), and N8-C9 1.480(9) and bond angles (deg):
Cl1-Ru-Cl2 169.18(6), Cl1-Ru-P1 88.24(6), Cl1-Ru-P2
101.19(6), Cl-Ru-N1 85.3(2), Cl1-Ru-N8 81.9(1), Cl2-Ru-
P1 93.90(6), Cl2-Ru-P2 89.04(6), C2-Ru-N1 89.8(2), Cl2-
Ru-N8 87.5(1), P1-Ru-P2 97.79(6), P1-Ru-N1 163.7(1), P1-
Ru-N8 88.7(1), P2-Ru-N1 98.1(1), P2-Ru-N8 172.9(1), N1-
Ru-N8 75.7(2), and C7-N8-C9 111.7(5).
t
derivatives trans-[RuCl2(CCHR)(c)] (R ) Ph, Bu) recently
reported by Spivak and co-workers show a trans Cl-Ru-Cl
analysis carried out on a single crystal. The ruthenium center
of 1 is in a pseudo-octahedral environment with the tridentate
PNN ligand adopting a mer arrangement with two cis phos-
phorus atoms and two trans chlorides (Figure 3). The Ru-N1
and the Ru-N8 distances are similar (2.170(5) and 2.148(5)
Å) and relatively long, due to the phosphine trans influence.
The Cl1-Ru-Cl2 angle is 169.18(6)°, while the P1-Ru-N1
angle is 163.7(1)° with a short N1-Ru-N8 angle (75.7(2)°).
The two phosphorus and two nitrogen atoms are displaced by
+0.074(3) and -0.079(3) Å from the best-fit plane. The
arrangement of the PNN ligand leads one N-H bond to be
almost parallel to the Ru-Cl1 bond (H8-N8-Ru-Cl1 dihedral
angle of about -10° with a H8‚‚‚Cl1 distance of 2.46 Å),
suggesting a possible intramolecular hydrogen bond interac-
tion.27 This structure resembles that of related trans-[RuCl2-
(PPh3)(PNN)] and trans-[RuCl2(PPh3)(PNNP*)] complexes (P*
denotes an uncoordinated phosphorus atom) bearing ligands with
amino or imino groups.28
arrangement.31
Complexes 2 and 3 are stable in the solid state but decompose
slowly in solution. 1H and 31P NMR spectra indicate a fluxional
1
behavior in the whole range of 293-183 K. H spectra of 2
and 3, as well as the 13C{1H} spectrum of the former complex,
were recorded at 193 K, while even at low temperatures, 3 led
to poor quality 13C{1H} NMR spectra. The 31P NMR monitoring
of CDCl3 solutions of both 2 and 3 evidenced complicated
patterns after a few hours, consistent with the formation of two
derivatives bearing PPh3 and PNN′ ligands as well as three
species arising from the dissociation of PPh3. Because of the
formation of equilibrium mixtures, isolation of a single species
was not possible. By contrast, the amino complex 1 is stable in
solution, and the 1H and 31P spectra show sharp signals,
suggesting that in 2 and 3, the imino donor ligand exerts a trans-
labilizing effect on triphenylphosphine, leading to the labile
species.
The monohydride complex trans,mer-[RuHCl(PPh3)(b)] (4)
was isolated following the procedure adopted for the preparation
of trans,cis-[RuHCl(PPh3)2(ampy)].19a The reaction between
equimolar amounts of [RuHCl(PPh3)3] and b in refluxing
heptane afforded a 3:1 mixture of 4 and a closely related
monohydride isomer (1H NMR for RuH at δ -16.91 with J(HP)
) 21.6, 28.2 Hz; 31P NMR: δ 66.5 and 62.7 with J(PP) )
32.8 Hz), which in dichloromethane converts into 4. Similar to
4, the complex trans,mer-[RuHCl(PPh3)(a)] (5) was prepared
from [RuHCl(PPh3)3] and a in heptane (Scheme 3).
The 31P{1H} NMR spectra of 4 and 5 show two doublets at
δ 64.3 and 66.5 [J(PP) ) 33.0 Hz] and δ 57.8 and 67.4 [J(PP)
) 29.8 Hz], respectively, indicating a cis arrangement of the
two phosphorus atoms. In the high field region of the 1H NMR
spectra, a doublet of doublets is present at ca. δ -17, and the
(25) Data collection was aborted due to low crystal quality. The quick
solution revealed non-resolvable disordered solvent molecules. Compound
1: [(C43H38Cl2N2P2Ru), n(CH2Cl2), light brown fragment (0.38 mm × 0.45
mm × 0.48 mm), monoclinic, C2/c (No. 15), a ) 37.2956(10) Å, b )
9.9079(3) Å, c ) 24.8352(5) Å, â ) 90.938(2)°, V ) 9175.9(4) Å3, Z )
8. Preliminary examination and data collection were carried out on
a κ-CCD device (Oxford Diffraction, Xcalibur) with an Oxford Cryosystems
cooling system at the window of a sealed tube (Enhance X-ray Source,
Spellman, DF3) with graphite monochromated Mo KR radiation (λ )
0.71073 Å). Data collection was performed at 153 K. Full-matrix least-
squares refinements were aborted at R1 ) 0.0686 (6984 intensities, Io >
2σ(Io)) and wR2 ) 0.1693 (8431 intensities, all data).
(26) Brandenburg, K. Diamond, Version 3.1d; Crystal Impact GbR:
Bonn, Germany, 2006.
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X.; Guo, J. P.; Wong, W. Y. Eur. J. Inorg. Chem. 2002, 231. (c) Wong,
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(30) Del Zotto, A.; Zangrando, E.; Baratta, W.; Felluga, A.; Martinuzzi,
P.; Rigo, P. Eur. J. Inorg. Chem. 2005, 4707.
(31) Beach, N. J.; Walker, J. M.; Jenkins, H. A.; Spivak, G. J. J.
Organomet. Chem. 2006, 691, 4147.

[RuCl2(PPh3)(PNN′)] Complexes as Efficient Catalysts
Organometallics, Vol. 26, No. 23, 2007 5639
Scheme 1
Scheme 2
Scheme 3
size of the N,N′ bound rings, show a remarkable different
activity. As a matter of fact, complex 2 resulted in being much
more active than 3, as inferred from the TOF values (2: 185 000
h-1, 3: 21 000 h-1; Table 1). This is also consistent with our
previous finding, which shows that the substitution of ampy
with 2-(aminoethyl)pyridine, in the complexes [RuCl2(PPh3)2-
(NN′)], resulted in lower catalytic performances.36 Most prob-
ably, the presence of a five-membered chelate ring in a gives a
higher stability to the six-coordinate complex with a neat
increase of its catalytic efficiency. On the basis of the high
activity shown by complex 2 in the transfer hydrogenation of
acetophenone, we decided to further explore its catalytic
potential in the reduction of other ketones. The results are listed
in Table 2. Generally, a good efficiency of complex 2 as a
precatalyst has been observed for all substrates employed. The
higher TOFs (≈250 000 h-1) were obtained for the acetophe-
none derivatives showing a chloro atom in the meta or para
position (Table 2, entries 3 and 4). Conversely, the chloro atom
two coupling constant values (in the range of 24-32 Hz) are
in agreement with the presence of two P atoms both cis to
hydride, as for trans,cis-[RuHCl(PPh3)2(ampy)].19a It should be
noted that a trans H-Ru-Cl arrangement characterizes other
Ru(II) complexes with a HClP2N2 donor set, namely, [RuHCl-
(P)2(NN)],32 [RuHCl(PP)(NN)],33 [RuHCl(PN)2],34 and [RuHCl-
(PNNP)],35 reported by Morris and co-workers.
Catalytic Transfer Hydrogenation. The reduction of ac-
etophenone to 1-phenylethanol by 2-propanol has been chosen
as a model reaction to explore the catalytic behavior of
complexes 1-3 in transfer hydrogenation. The catalytic trials
were carried out using a 0.1 M solution of the substrate, 0.1
mol % of catalyst, and 4 mol % of (CH3)2CHONa freshly
prepared from elemental sodium (eq 2). A 2-propanol solution
containing the catalyst and base was added to a 2-propanol
solution of the substrate kept at reflux. During the dissolution
of the Ru(II) complex into the alcohol, which was accomplished
within few minutes, the color of the solution changed from red-
brown to greenish yellow.
in the ortho position leads to a much lower TOF (70 000 h-1
)
(Table 2, entry 2). The whole trend can be rationalized in terms
of steric hindrance, which is kinetically relevant when the chloro
atom is in the ortho position. Lower TOFs with respect to that
observed for acetophenone (Table 2, entry 1) were found for
cyclic and linear aliphatic ketones (Table 2, entries 5-7). Using
complex 2 as the catalyst, 1-phenylethanol was prepared on a
gram-scale in nearly quantitative yield and 96% purity.
It is noteworthy that the amino and imino complexes 1 and
2 display the same activity for the reduction of acetophenone
under these conditions. Similar catalytic activity for phosphine/
imine versus phosphine/amine complexes [RuCl2(PPh3)(PN)]
has been reported by Gimeno and co-workers.3b On the basis
of these results, we were stimulated to investigate the catalytic
behavior of the tetradentate diimino versus diamino complexes
[RuCl2(PNNP)2] 6 and 7, respectively (Figure 4). Complex 7
has been described by Gao et al. and Noyori et al.10a,c to be an
excellent precatalyst for the transfer hydrogenation of ketones,
while 6 showed a poor activity in the presence of a low base
amount (base/Ru ) 0.5).
The amino complex 1 has been found to catalyze the
quantitative reduction of acetophenone to 1-phenylethanol in 2
min, affording a turnover frequency number of 190 000 h-1 at
50% conversion, which is a value of the same order to that
reported for the related complexes cis,cis-[RuCl2(diphosphine)-
(ampy)].19a The imino derivatives 2 and 3, displaying a trans
and cis Cl-Ru-Cl arrangement, respectively, and a different
In the catalytic conditions adopted by us (i.e., in the presence
of an excess of base and under reflux), interestingly, complexes
6 and 7 showed substantially the same catalytic activity (TOF:
6, 27 000 h-1; 7, 26 000 h-1, Table 1), thus confirming that
there is no difference between the catalytic performances of
complexes with phosphine/imine or phosphine/amine ligands.
These results may suggest that during catalysis, the imino
(32) (a) Abdur-Rashid, K.; Abbel, R.; Hadzovic, A.; Lough, A. J.; Morris,
R. H. Inorg. Chem. 2005, 44, 2483. (b) Abdur-Rashid, K.; Lough, A. J.;
Morris, R. H. Organometallics 2000, 19, 2655.
(33) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics
2001, 20, 1047.
(34) Guo, R.; Lough, A. J.; Morris, R. H.; Song, D. Organometallics
2004, 23, 5524.
(35) Rautenstrauch, V.; Hoang-Cong, X.; Churlaud, R.; Abdur-Rashid,
K.; Morris, R. H. Chem.sEur. J. 2003, 9, 4954.
(36) Baratta, W. et al., unpublished results.

5640 Organometallics, Vol. 26, No. 23, 2007
Del Zotto et al.
Table 1. Catalytic Transfer Hydrogenation of Acetophenone
of the ampy moiety that, as we previously reported, enables
fast hydrogen transfer reactions (i.e., a ligand acceleration
effect).18
with Complexes 1-7a
c
complex
yield % (min)b
TOF (h-1
)
The monohydride complexes 4 and 5 do not catalyze the
reduction of acetophenone in the absence of base, suggesting
that a dihydride species should be involved in the catalysis.
Under the catalytic conditions adopted with complexes 1-3,
also 4 and 5 induce the reduction of acetophenone but at lower
rates (TOF ) 16 000 h-1 4; 15 000 h-1 5), which can be ascribed
to the formation of different isomer dihydride species. A lower
performance of hydride versus chloride Ru(II) precatalysts has
also been reported by other authors.38 As regards the catalytic
cycle, the precursors 1-5 undergo different rapid transforma-
tions to give the catalytically active species. With the imino
ligands, the formation of Ru-hydride complexes leads to
concomitant reduction of the CdN bond, affording amino
ligands. According to our study on cis-[RuCl2(PP)(ampy)],19a
it is likely that with 1-5, the transfer hydrogenation occurs via
the amino [RuHX(PPh3)(PNN′)] (X ) H, OR′) species, involv-
ing â-hydrogen elimination versus ketone insertion reactions.1f,39
1
2
2d
3
4
5
6
7
98 (2)
98 (2)
190 000
185 000
97 (12)
98 (15)
96 (15)
96 (15)
97 (20)
96 (20)
125 000
21 000
16 000
15 000
27 000
26 000
a Experimental conditions: reactions carried out at 82 °C, acetophenone
0.1 M in 2-propanol, acetophenone/complex/(CH3)2CHONa ) 1000:1:40.
b Determined by GC analysis. c Turnover frequency (mol of substrate per
mol of complex per hour) at 50% conversion. d Acetophenone/2/
(CH3)2CHONa ) 5000:1:40.
Table 2. Catalytic Transfer Hydrogenation of Ketones with
Complex 2a
Conclusion
In summary, we have described the ruthenium complexes
[RuCl2(PPh3)(PNN′)] with tridentate PNN′ ligands containing
phosphine (P), amine or imine (N), and pyridyl donor groups
(N′), which are efficient catalytic precursors for the transfer
hydrogenation of ketones. In the trans complexes 1 and 2, the
PNN′ ligands containing a five-membered NN′ cycle adopt a
mer arrangement, while a fac geometry has been observed for
the cis 3, characterized by a six-membered NN′ cycle. Interest-
ingly, in the catalytic transfer hydrogenation, the trans complexes
1 and 2 are the most active and show similar rates, suggesting
that during the catalysis, the CdN group is reduced, affording
the amine N-H moiety, which is a prerequisite to achieve high
activity. Work is in progress to extend the chemistry of imino
ruthenium complexes in asymmetric transfer hydrogenation.
a Experimental conditions: reactions carried out at 82 °C, acetophenone
0.1 M in 2-propanol, acetophenone/complex/(CH3)2CHONa ) 1000:1:40.
b Determined by GC or GC-MS analysis. c Turnover frequency (mol of
substrate per mol of complex per hour) at 50% conversion.
Experimental Procedures
General Remarks and Instrumentation. All reagents were
purchased from Aldrich and used without further purification.
Commercial reagent grade solvents were dried according to standard
methods and freshly distilled under argon before use. All syntheses
and manipulations were carried out in an atmosphere of argon using
standard Schlenk techniques. The ligand N-(2-(diphenylphosphino)-
benzylidene)(2-(2-pyridyl)ethyl)amine (c)22 and complexes [RuCl2-
(PPh3)3]40 and [RuHCl(PPh3)3]41 were synthesized according to
literature procedures.
The 1H, 13C, and 31P NMR spectra (at 200.13, 50.32, and 81.02
MHz, respectively) were recorded on a Bruker AC 200 F QNP
Figure 4.
1
spectrometer. The H and 13C chemical shifts were referenced to
complex precursors are converted to amino species for which
the presence of the N-H moiety is responsible for the high
rate. The reduction of the CdN function of the coordinated
ligand into a CH-NH bond is therefore favored by the excess
of a strong base and at high temperature. Ruthenium complexes
have been found to catalyze the transfer hydrogenation of
aldimines in basic alcohol media at high temperatures.37 The
higher activity found for the tridentate PNN′ compounds 1 and
2, as compared to the tetra- or bidentate [RuCl2(PNNP)] and
[RuCl2(PPh3)(PN)] complexes, is certainly due to the presence
SiMe4, while positive 31P chemical shifts were downfield from 85%
H3PO4 as the external standard. The GC-MS analyses, run to control
the identity of the compounds obtained in the catalytic trials, were
carried out with a Fisons TRIO 2000 gas chromatograph-mass
spectrometer working in the positive ion 70 eV electron impact
(38) (a) Gagliardo, M.; Chase, P. A.; Brouwer, S.; van Link, G. P. M.;
van Koten, G. Organometallics 2007, 26, 2219. (b) Amoroso, D.; Jabri,
A.; Yap, G. P. A.; Gusev, D. G.; dos Santos, E. N.; Fogg, D. E.
Organometallics 2004, 23, 4047.
(39) Aranyos, A.; Csjernyik, G.; Szabo´, K. J.; Ba¨ckvall, J. E. Chem.
Commun. 1999, 351.
(37) (a) Yi, C. S.; He, Z.; Guzei, I. A. Organometallics 2001, 20, 3641.
(b) Mizushima, E.; Yamaguchi, M.; Yamagishi, T. J. Mol. Catal. A: Chem.
1999, 148, 69. (c) Wang, G. Z.; Ba¨ckvall, J. E. Chem. Commun. 1992,
980.
(40) Stephenson, T. A.; Wilkinson, G. J. Inorg. Nucl. Chem. 1966, 28,
945.
(41) Amoroso, D.; Snelgrove, J. L.; Conrad, J. C.; Drouin, S. D.; Yap,
G. P. A.; Fogg, D. E. AdV. Synth. Catal. 2002, 344, 757.

[RuCl2(PPh3)(PNN′)] Complexes as Efficient Catalysts
Organometallics, Vol. 26, No. 23, 2007 5641
dried under reduced pressure. Yield: 269 mg, 82%. Anal. calcd
for C43H38Cl2N2P2Ru (816.72): C, 63.24%; H, 4.69%; N, 3.43%.
Found: C, 62.93%; H, 4.68%; N, 3.38%. IR (polyethene): 321
cm-1 (νRu-Cl). 31P NMR (CD2Cl2, 295 K): δ 46.6 (d, J(PP) ) 29.6
Hz), 41.8 (d, J(PP) ) 29.6 Hz). 1H NMR (CD2Cl2, 295 K): δ 8.27
(d, J(HH) ) 4.0 Hz, 1H, pyridine), 7.8-6.9 (m, 27H, aromatic
and pyridine), 6.61 (t, J(HH) ) 7.1 Hz, 1H, pyridine), 6.55 (t, J(HH)
) 7.1 Hz, 1H, pyridine), 5.94 (t, J(HH) ) 8.2 Hz, 2H, aromatic),
5.55 (t, J(HH) ) 12.4 Hz, 1H, aromatic), 4.61 (t, J(HH) ) 8.4 Hz,
1H, CH2), 4.46 (t, J(HH) ) 8.4 Hz, 1H, CH2), 4.09 (dt, J(HH) )
13.4, 3.2 Hz, 1H, CH2), 3.77 (m, 1H, CH2), 0.50 (br s, 1H, NH).
13C{1H} NMR (CD2Cl2, 295 K, see Figure 5 for the numbering of
C atoms, 13C-31P coupling constants (in Hz) are reported in
brackets): δ 161.0 (C9), 157.7 (C13), 139.7 [13.8] (Ci), 136.7 (C6),
135.9 (C11), 135.1 [5.7] (C4), 134.2 [8.9] (C2), 132.6 (C3), 131.2
[7.9] (C5), 130.2 [54.7] (C1), 129.2 [25.0] (Co), 128.0 [4.2] (Cm),
127.1 (Cp), 121.3 (C10), 121.1 (C12), 60.2 (C8), 56.7 [5.1] (C7).
Figure 5.
mode. The injector temperature was kept at 250 °C, and the column
(Supelco SE-54, 30 m long, 0.25 mm i.d., coated with a 0.5 µm
phenyl methyl silicone film) temperature was programmed from
50 to 280 °C with a gradient of 10 °C/min. The GC analyses of
the catalytic mixtures were run on a Fisons GC 8000 Series gas
chromatograph equipped with a Supelco PTA-5 column (30 m long,
0.53 mm i.d., coated with a 3.0 µm poly(5% diphenyl-95%
dimethylsiloxane) film). The injector and column temperatures were
as indicated previously. The elemental analyses (C, H, and N) were
carried out in the Microanalytical Laboratory of the Dipartimento
di Scienze e Tecnologie Chimiche, Universita` di Udine, with a Carlo
Erba 1106 elemental analyzer.
Synthesis of Ligand a. 2-(Diphenylphosphino)benzaldehyde
(580 mg, 2.0 mmol) and 2-(aminomethyl)pyridine (238 mg, 2.2
mmol) were stirred in toluene (20 mL), and the mixture was
refluxed for 1 h. A yellow oil was obtained upon elimination of
the solvent under reduced pressure. Twice, the treatment with
dichloromethane (10 mL)/cold n-hexane (50 mL) resulted in a
purification of the product, which, however, did not crystallize.
Yield: 657 mg, 86%. 31P{1H} NMR (CDCl3, 295 K): δ -13.0.
1H NMR (CDCl3, 295 K): δ 9.05 (dt, J(HH) ) 1.3 Hz, JHP ) 4.8
Hz, 1H, HCdN), 8.48 (ddd, J(HH) ) 2.0, 0.7, 0.5 Hz, 1H,
pyridine), 8.04 (ddd, J(HH) ) 1.6, 0.6 Hz, JHP ) 3.9 Hz, 1H,
aromatic), 7.47 (dt, J(HH) ) 3.0, 0.7 Hz, 1H, pyridine), 7.4-7.0
(m, 12H, aromatic), 7.06 (ddd, J(HH) ) 3.0, 2.0, 0.5 Hz, 1H,
pyridine), 7.0-6.8 (m, 2H, pyridine and aromatic), 4.83 (s, 2H,
CH2). 13C{1H} NMR (CDCl3, 295 K, see Figure 5 for the numbering
of C atoms, 13C-31P coupling constants (in Hz) are reported in
brackets): δ 162.0 [20.2] (C7), 159.1 (C9), 148.8 (C13), 139.3 [17.7]
(C1), 136.5 [9.8] (Ci), 136.5 (C11), 137.6 [19.5] (C6), 133.9 [20.1]
(Co), 133.4 [9.5] (C5), 130.4 [1.2] (C4), 128.9 (C3), 128.8 (Cp), 128.5
[8.5] (Cm), 128.1 (C2), 122.1 (C10), 121.7 (C12), 66.5 (C8).
Synthesis of trans-[RuCl2(PPh3)(a)] (2). A mixture of [RuCl2-
(PPh3)3] (815 mg, 0.85 mmol), a (358 mg, 0.94 mmol), and toluene
(20 mL) was stirred at 90 °C for 20 min. The resulting purple-red
mixture was cooled, and n-hexane (20 mL) was added to complete
the precipitation of the product. The pink-purple solid was filtered
off, washed with n-hexane and ethyl ether, and dried under reduced
pressure. Yield: 610 mg, 88%. Anal. calcd for C43H36Cl2N2P2Ru
(814.70): C, 63.39%; H, 4.45%; N, 3.44%. Found: C, 63.15%;
H, 4.48%; N, 3.33%. IR (polyethene): 320 cm-1 (νRu-Cl). 31P NMR
(CD2Cl2, 295 K): δ 53.2 (d, J(PP) ) 28.3 Hz), 33.2 (d, J(PP) )
1
28.3 Hz). H NMR (CD2Cl2, 193 K): δ 8.84 (m, 1H, HCdN),
8.17 (m, 3H, aromatic and pyridine), 7.7-6.2 (m, 28H, aromatic
and pyridine), 5.52 (m, 2H, aromatic), 5.16 (m, 1H, CH2), 4.46
(m, 1H, CH2). 13C{1H} NMR (CD2Cl2, 193 K, see Figure 5 for the
numbering of C atoms, 13C-31P coupling constants (in Hz) are
reported in brackets): δ 166.3 (C9), 156.4 (C13), 136.9 [14.5] (Ci),
136.5 (C6), 135.5 (C11), 135.4 [4.7] (C4), 134.7 [7.3] (C2), 133.7
(C3), 132.0 [2.6] (C5), 130.1 [49.3] (C1), 129.6 [22.1] (Co), 129.2
(Cp), 127.4 [5.0] (Cm), 125.5 (C10), 122.4 (C12), 74.5 (C8), 55.1
[3.9] (C7).
Synthesis of cis-[RuCl2(PPh3)(c)] (3). To [RuCl2(PPh3)3] (575
mg, 0.60 mmol) and c (260 mg, 0.66 mmol) was added 20 mL of
toluene, and the slurry was stirred at 90 °C for 20 min. The resulting
deep red mixture was cooled, and n-hexane (30 mL) was added to
complete the precipitation of the product. The brick-red solid was
filtered off, washed with n-hexane and ethyl ether, and dried under
reduced pressure. Yield: 453 mg, 91%. Anal. calcd for C44H38-
Cl2N2P2Ru (828.72): C, 63.77%; H, 4.62%; N, 3.38%. Found: C,
63.04%; H, 4.60%; N, 3.29%. IR (polyethene): 320, 312 cm-1
(νRu-Cl). 31P NMR (CD2Cl2, 295 K): δ 49.4 (d, J(PP) ) 29.1 Hz),
31.5 (d, J(PP) ) 29.1 Hz). 1H NMR (CD2Cl2, 193 K): δ 8.82 (m,
1H, HCdN), 8.58 (m, 1H, pyridine), 8.33 (m, 3H, aromatic and
pyridine), 7.7-6.1 (m, 26H, aromatic and pyridine), 5.57 (m, 3H,
aromatic), 4.03 (m, 2H, CH2), 2.74 (m, 2H, CH2).
Synthesis of Ligand b. 2-(Diphenylphosphino)benzaldehyde
(580 mg, 2.0 mmol) and 2-(aminomethyl)pyridine (238 mg, 2.2
mmol) were stirred at room temperature in methanol (20 mL) in
the presence of an excess of Na2SO4 (710 mg, 5.0 mmol) for 3 h.
Then, after elimination of the solid by filtration, NaBH4 (76 mg,
2.0 mmol) was added, and the mixture was gently warmed for 30
min at 45 °C. The solvent was eliminated under reduced pressure,
and after the addition of water (10 mL), the organic material was
extracted with ethyl ether (3 × 10 mL). The desired product was
obtained as a yellow oil by pumping off the solvent under reduced
pressure. Yield: 536 mg, 70%. 31P{1H} NMR (CDCl3, 295 K): δ
1
) -15.3. H NMR (CDCl3, 295 K): 8.40 (d, J(HH) ) 4.1 Hz,
1H, pyridine), 7.6-6.9 (m, 16H, aromatic and pyridine), 6.82 (dd,
J(HH) ) 4.1, 2.1 Hz, 1H, pyridine), 3.95 (s, 2H, CH2), 3.73 (s,
2H, CH2), 2.06 (br s, 1H, NH). 13C{1H} NMR (CDCl3, 295 K, see
Figure 5 for the numbering of C atoms, 13C-31P coupling constants
(in Hz) are reported in brackets): δ 159.9 (C9), 149.1 (C13), 144.3
[23.8] (C1), 136.8 [10.2] (Ci), 136.3 (C11), 135.7 [14.1] (C6), 133.8
[19.6] (Co), 131.9 [9.6] (C5), 129.1 [5.4] (C4), 129.0 (C3), 128.8
(Cp), 128.6 [7.0] (Cm), 127.21 (C2), 122.0 (C10), 121.7 (C12), 54.5
(C8), 51.9 [21.0] (C7).
Synthesis of trans-[RuCl2(PPh3)(b)] (1). [RuCl2(PPh3)3] (383
mg, 0.40 mmol) was dissolved in dichloromethane (5 mL), and to
the solution was added b (168 mg, 0.44 mmol) dissolved in
dichloromethane (1 mL). The solution was stirred at room tem-
perature for 1 h and then concentrated to ca. 3 mL. The addition
of ethyl ether (15 mL) afforded a light brown precipitate. The
product was isolated by filtration, washed with ethyl ether, and
Synthesis of trans-[RuHCl(PPh3)(b)] (4). [RuHCl(PPh3)3] (185
mg, 0.20 mmol) and b (84 mg, 0.22 mmol) were suspended in
n-heptane (10 mL), and the slurry was refluxed for 2 h. The solid
was filtered off, washed with ethyl ether, and dried under reduced
pressure. The product was then dissolved in dichloromethane (5
mL), and the solution was stirred for 30 min. Concentration and
addition of n-pentane afforded a red-brown precipitate, which was
filtered, washed with n-pentane, and dried under reduced pressure.
Yield: 92 mg, 59%. Anal. calcd for C43H39ClN2P2Ru (782.28): C,
66.02%; H, 5.03%; N, 3.58%. Found: C, 65.93%; H, 4.98%; N,
3.51%. 31P NMR (CD2Cl2, 295 K): δ 66.5 (d, J(PP) ) 33.0 Hz),
1
64.3 (d, J(PP) ) 33.0 Hz). H NMR (CD2Cl2, 295 K): δ 7.96 (d,
1H, pyridine), 7.8-6.7 (m, 30H, aromatic and pyridine protons),
6.70 (t, 1H, aromatic), 6.46 (t, 1H, aromatic), 4.59 (t, 1H, CH2),
4.30 (dt, 1H, CH2), 3.89 (m, 2H, CH2), 3.73 (m, 1H, NH), -17.72
(dd, J(HP) ) 24.5, 31.6 Hz, 1H, Ru-H). 13C{1H} NMR (CD2Cl2,

5642 Organometallics, Vol. 26, No. 23, 2007
Del Zotto et al.
295 K, see Figure 5 for the numbering of C atoms, 13C-31P coupling
constants (in Hz) are reported in brackets): δ 162.7 (C9), 156.6
(C13), 138.9 [14.2] (Ci), 137.1 [42.6] (C1), 135.0 (C6), 134.2 [8.2]
(C2), 134.8 (C11), 134.3 [9.8] (C4), 132.3 (C3), 131.4 [7.2] (C5),
129.2 [17.8] (Co), 128.6 [2.3] (Cp), 127.4 [8.5] (Cm), 122.8 (C10),
119.8 (C12), 63.2 (C8), 59.6 [7.1] (C7).
was added to solution a kept at reflux, with immediate starting of
the reaction. For the gas chromatographic analysis of the reaction
mixture, 0.2 mL of solution was extracted by means of a syringe,
cooled, and mixed with 1 mL of ethyl ether. The resulting solution
was passed through a microcolumn filled with silica gel to eliminate
any inorganic material.
Synthesis of trans-[RuHCl(PPh3)(a)] (5). [RuHCl(PPh3)3] (232
mg, 0.25 mmol) and a (107 mg, 0.28 mmol) were suspended in
n-heptane (15 mL), and the slurry was refluxed for 2 h. The brown
solid was filtered off, washed with ethyl ether, and dried under
reduced pressure. Yield: 134 mg, 68%. Anal. calcd for C43H37-
ClN2P2Ru (780.26): C, 66.19%; H, 4.78%; N, 3.59%. Found: C,
66.01%; H, 4.71%; N, 3.50%. 31P NMR (CD2Cl2, 295 K): δ 67.4
Synthesis of (()-1-Phenylethanol. A 500 mL three-necked
round-bottomed flask, equipped with a magnetic stirrer and a
condenser, was charged with complex 2 (40.9 mg, 50 µmol) and
200 mL of a sodium isopropoxide solution in 2-propanol prepared
from Na (46 mg, 2 mmol). The mixture was gently warmed until
a clear solution was obtained. Then, acetophenone (6.00 g, 0.05
mol) in 2-propanol (200 mL) was added, and the solution was
refluxed for 30 min. After cooling, the solvent was pumped off,
and the orange-brown residue was purified by column chroma-
tography using silica gel and ethyl ether as the eluent. Elimination
of the solvent afforded 5.92 g (97%) of the desired product, whose
1
(d, J(PP) ) 29.8 Hz), 57.8 (d, J(PP) ) 29.8 Hz). H NMR (CD2-
Cl2, 193 K): δ 8.59 (m, 1H, HCdN), 7.87 (m, 1H, pyridine), 7.7-
6.4 (m, 31H, aromatic and pyridine), 5.51 (m, 1H, aromatic), 4.96
(m, 1H, CH2), 4.29 (m, 1H, CH2), -16.38 (dd, J(HP) ) 24.6, 30.5
Hz, 1H, Ru-H). 13C{1H} NMR (CD2Cl2, 193 K, see Figure 5 for
the numbering of C atoms, 13C-31P coupling constants (in Hz) are
reported in brackets): δ 158.1 (C9), 149.7 (C13), 139.1 [13.5] (Ci),
136.0 (C6), 135.1 [44.3] (C1), 134.9 (C11), 134.6 [8.0] (C2), 134.0
[6.7] (C4), 132.9 (C3), 131.4 [6.1] (C5), 130.2 [12.9] (Co), 128.4
[2.1] (Cp), 128.1 [8.8] (Cm), 124.2 (C10), 121.8 (C12), 65.3 (C8),
58.9 [6.3] (C7).
1
purity (96%) was checked by GC and H NMR.
Acknowledgment. This research was financially supported
by the Ministero Italiano dell’Universita` e della Ricerca (MIUR),
Rome, Italy (COFIN 2005/07 fund). We thank Johnson-Matthey/
Alfa Aesar for a generous loan of ruthenium(III) chloride hydrate
and P. Polese for carrying out elemental analyses.
General Procedure for the Catalytic Transfer Hydrogenation.
Solutions containing the substrate (a) and the catalyst (b) were
prepared as follows: (a) the organic substrate (1 mmol) was
dissolved into 9 mL of 2-propanol, and (b) the ruthenium complex
(2.5 µmol) was suspended into 1.5 mL of 2-propanol, and to the
mixture was added 1 mL of a 0.1 M solution of (CH3)2CHONa in
2-propanol. Then, the slurry was gently warmed until complete
dissolution of the complex was achieved. Finally, solution b (1 mL)
Supporting Information Available: Tables of crystal and
data collection parameters, bond lengths, and bond angles for 1.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM700647K