Synthesis of ruthenium(II) complexes containing hydroxymethylphosphines and their catalytic activities for hydrogenation of supercritical carbon dioxide

Article abstract of DOI:10.1021/ic700470n

Ligand substitution of RuCl₂[P(C₆H₅) ₃]₃ and Cp*RuCl(isoprene) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) complexes with hydroxymethylphosphines was investigated to develop new catalyst systems for CO₂ hydrogenation. A reaction of P(C₆H₅)₂CH ₂OH with RuCl₂[P(C₆H₆) ₃]₃ in CH₂Cl₂ gave Ru(H)Cl(CO)[P(C₆H₅)₂CH₂OH] ₃ (1), which was characterized by NMR spectroscopy and X-ray crystallographic analysis. An isotope labeling experiment using P(C ₆H₅)₂¹³CH₂OH indicated that the carbonyl moiety in complex 1 originated from formaldehyde formed by degradation of the hydroxymethylphosphine. Elimination of formaldehyde from PCy₂CH₂OH (Cy = cyclohexyl) was also promoted by treatment of RuCl₂[P(C₆H₅)₃]₃ in ethanol to give RuCl₂(PHCy₂)₄ under mild conditions. On the other hand, the substitution reaction using Cp*RuCl(isoprene) with the hydroxymethylphosphine ligands proceeded smoothly with formation of Cp*RuCl(L)₂ [2a-2c; L = P(C ₆H₅)₂CH₂OH, PCy(CH ₂OH)₂, and P(CH₂OH)₃] in good yields. The isolable hydroxymethylphosphine complexes 1 and 2 efficiently catalyzed the hydrogenative amidation of supercritical carbon dioxide (scCO ₂) to N,N-dimethylformamide (DMF).

Full text of DOI:10.1021/ic700470n

Inorg. Chem. 2007, 46, 5791−5797
Synthesis of Ruthenium(II) Complexes Containing
Hydroxymethylphosphines and Their Catalytic Activities for
Hydrogenation of Supercritical Carbon Dioxide
Yoshihito Kayaki, Yoshiki Shimokawatoko, and Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of
Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
Received March 10, 2007
Ligand substitution of RuCl2[P(C6H5)3]3 and Cp*RuCl(isoprene) (Cp*
) 1,2,3,4,5-pentamethylcyclopentadienyl)
complexes with hydroxymethylphosphines was investigated to develop new catalyst systems for CO2 hydrogenation.
A reaction of P(C6H5)2CH2OH with RuCl2[P(C6H5)3]3 in CH2Cl2 gave Ru(H)Cl(CO)[P(C6H5)2CH2OH]3 (1), which was
characterized by NMR spectroscopy and X-ray crystallographic analysis. An isotope labeling experiment using
P(C6H5)213CH2OH indicated that the carbonyl moiety in complex 1 originated from formaldehyde formed by degradation
of the hydroxymethylphosphine. Elimination of formaldehyde from PCy2CH2OH (Cy
) cyclohexyl) was also promoted
by treatment of RuCl2[P(C6H5)3]3 in ethanol to give RuCl2(PHCy2)4 under mild conditions. On the other hand, the
substitution reaction using Cp*RuCl(isoprene) with the hydroxymethylphosphine ligands proceeded smoothly with
formation of Cp*RuCl(L)2 [2a−2c; L ) P(C6H5)2CH2OH, PCy(CH2OH)2, and P(CH2OH)3] in good yields. The isolable
hydroxymethylphosphine complexes 1 and 2 efficiently catalyzed the hydrogenative amidation of supercritical carbon
dioxide (scCO2) to N,N-dimethylformamide (DMF).
Introduction
amine (Scheme 1).7 For the hydrogenation of CO2, scCO2
has been shown to be an advantageous reaction medium
because of its unique physicochemical properties;8 however,
Water-soluble tertiary phosphines have attracted consider-
able interest in the development of easily recoverable and
reusable organometallic catalysts.1 Structural modification
of hydrophilic phosphorus ligands has been extensively
studied, by practical works on aqueous biphasic catalysis with
TPPTS (3,3′,3′′-phosphinetriylbenzene sulfonic acid),2 for
aryl- and alkyl-phosphines with hydroxy, ammonium, phos-
phonium, or carboxylate groups.3 Among them, tris(hy-
droxymethyl)phosphine, P(CH2OH)3, has been applied to the
area of catalysis and biomedicine as a readily available and
moderately air-stable compound.4-6
(4) (a) Chatt, J.; Leigh, G. J.; Slade, R. M. J. Chem. Soc., Dalton Trans.
1973, 2021-2028. (b) Pringle, P. G.; Smith, M. B. Platinum Met.
ReV. 1990, 34, 74-76. (c) Harrison, K. N.; Hoye, P. A. T.; Orpen, A.
G.; Pringle, P. G.; Smith, M. B. J. Chem. Soc., Chem. Commun. 1989,
1096-1097. (d) Ellis, J. W.; Harrison, K. N.; Hoye, P. A. T.; Orpen,
A. G.; Pringle, P. G.; Smith, M. B. Inorg. Chem. 1992, 31, 3026-
3033. (e) Hoye, P. A. T.; Pringle, P. G.; Smith, M. B.; Worboys, K.
J. Chem. Soc., Dalton Trans. 1993, 269-274. (f) Fukuoka, A.; Kosugi,
W.; Morishita, F.; Hirano, M.; McCaffrey, L.; Henderson, W.; Komiya,
S. Chem. Commun. 1999, 489-490. (g) Komiya, S.; Ikuine, M.;
Komine, N.; Hirano, M. Chem. Lett. 2002, 31, 72-73. (h) Komiya,
S.; Ikuine, M.; Komine, N.; Hirano, M. Bull. Chem. Soc. Jpn. 2003,
76, 183-188. (i) Berning, D. E.; Katti, K. V.; Barbour, L. J.; Volkert,
W. A. Inorg. Chem. 1998, 37, 334-339. (j) Raghuraman, K.;
Pillarsetty, N.; Volkert, W. A.; Barnes, C.; Jurisson, S.; Katti, K. V.
J. Am. Chem. Soc. 2002, 124, 7276-7277. (k) Driessen-Ho¨lscher, B.;
Heinen, J. J. Organomet. Chem. 1998, 570, 141-146. (l) Bianchini,
M.; Frediani, P.; Salvini, A.; Rosi, L.; Pistolesi, L.; Piacenti, F.; Ianelli,
S.; Nardelli, M. Organometallics 1997, 16, 482-489. (m) Salvini,
A.; Frediani, P.; Bianchini, M.; Piacenti, F.; Pistolesi, L.; Rosi, L. J.
Organomet. Chem. 1999, 582, 218-228. (n) Cadierno, V.; Crochet,
P.; Garc´ıa-Garrido, S. E.; Gimeno, J. Dalton Trans. 2004, 3635-3641.
(o) Maynard, H. D.; Grubbs, R. H. Tetrahedron Lett. 1999, 40, 4137-
4140. (p) Bharathi, D. S.; Sridhar, M. A.; Prasad, J. S.; Samuelson,
A. G. Inorg. Chem. Commun. 2001, 4, 490-492. (q) Ezhova, M. B.;
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(r) Cubrilo, J.; Hartenbach, I.; Schleid, T.; Winter, R. F. Z. Anorg.
Allg. Chem. 2006, 632, 400-408.
We have previously reported that P(CH2OH)3 was a
beneficial supporting ligand of a highly efficient Ru catalyst
for hydrogenation of scCO2 to the formate salt, which
transformed into DMF after its dehydration with dimethyl-
* To whom correspondence should be addressed. E-mail: tikariya@
apc.titech.ac.jp. Fax: +81-3-5734-2637.
(1) Joo´, F.; Katho´, A. In Aqueous-Phase Organometallic Catalysis:
Concepts and Applications; Cornils, B., Herrmann, W. A., Eds.; Wiley-
VCH: Weinheim, Germany, 1998; pp. 340-372.
(2) Cornils, B. Org. Proc. Res. DeV. 1998, 2, 121-127.
(3) (a) Pinault, N.; Bruce, D. W. Coord. Chem. ReV. 2003, 241, 1-25.
(b) Katti, K. V.; Gali, H.; Smith, C. J.; Berning, D. E. Acc. Chem.
Res. 1999, 32, 9-17.
10.1021/ic700470n CCC: $37.00
Published on Web 06/13/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 14, 2007 5791

Kayaki et al.
Scheme 1
Scheme 2
the catalyst performance may be altered by subtle phase
behavior during the progress of reaction. In fact, compared
with a Ru-P(CH3)3 system,9 an analogous Ru-P(CH2OH)3
complex, RuCl2[PH(CH2OH)2]2[P(CH2OH)3]2,5 provided su-
perior catalyst performance even at the later stage of the
DMF synthesis, because the water-soluble catalyst could
merge effectively with the reaction mixture including the
coproduct water in scCO2.7 This finding of a marked ligand
effect on the hydrogenation of scCO2 prompted us to study
other Ru catalyst precursors bearing OH-substituted phos-
phorus ligands with different polarity. We describe herein
the synthesis of novel ruthenium(II) complexes by ligand
substitution using several hydroxymethylphosphines and
catalytic hydrogenative amidation of scCO2 with these
complexes.
Figure 1. Molecular structure of Ru(H)Cl(CO)[P(C6H5)2CH2OH]3‚CH2Cl2
(1). The solvent molecule and hydrogen atoms, other than H(1), H(14),
H(27), and H(40), are omitted for clarity, and the ellipsoids represent 50%
probability. The dashed lines indicate the hydrogen bonds. Selected bond
lengths (Å) and angles (deg): Ru(1)-H(1) ) 1.57(3), Ru(1)-Cl(1) )
2.5133(6), Ru(1)-P(1) ) 2.3497(7), Ru(1)-P(2) ) 2.3632(6), Ru(1)-P(2)
) 2.4453(6), Ru(1)-C(1) ) 1.827(3), C(1)-O(1) ) 1.149(3), P(1)-Ru-
(1)-Cl(1) ) 92.01(2), P(2)-Ru(1)-Cl(1) ) 92.01(2), P(3)-Ru(1)-Cl(1)
) 87.85(2), C(1)-Ru(1)-P(1) ) 85.90(8), C(1)-Ru(1)-P(3) ) 98.46(8),
P(1)-Ru(1)-P(3) ) 101.71(2), P(2)-Ru(1)-P(3) ) 95.53(2).
solution at ambient temperature. The molecular structure of
complex 1 was determined using the data collected at low
temperature. The X-ray crystal structure of 1 is depicted in
Figure 1, with selected bond lengths including the Ru-H
bond and angles in the caption.
Results and Discussion
Reaction of RuCl2[P(C6H5)3]3 with Hydroxymethylphos-
phines. The ligand exchange of the Ru complex, RuCl2-
[P(C6H5)3]3, with P(C6H5)2CH2OH was examined according
to the reported procedure for the reaction with P(CH2OH)3.5
The reaction of RuCl2[P(C6H5)3]3 with 4 molar equiv of
P(C6H5)2CH2OH at room temperature in CH2Cl2 for 24 h
gave a colorless complex, Ru(H)Cl(CO)[P(C6H5)2CH2OH]3
(1), bearing hydrido and carbonyl ligands in addition to
P(C6H5)2CH2OH ligands in 45% yield, as shown in Scheme
2. The 1H NMR spectrum of 1 exhibits the hydrido resonance
at -6.7 ppm as a doublet of triplets coupled to the phosphine
Complex 1 has an octahedral geometry with a meridional
arrangement of three phosphines and a trans configuration
of the carbonyl and chloro ligands. The hydrido ligand is in
a cis position to Cl and CO ligands; the Ru-H distance is
1.57 Å and the H-Ru-Cl and H-Ru-C angles are 84 and
89°, respectively. Although the lengths of the Ru-P, Ru-
C, and C-O bonds in 1 resemble the values observed for a
related OH-free complex, Ru(H)Cl(CO)[P(C6H5)2CH3]3, the
Ru-Cl distance of 2.5133 Å in 1 is somewhat longer than
that of 2.486 Å in the P(C6H5)2CH3 complex.10 Notably, an
intramolecular hydrogen bond between the chloro ligand and
hydroxy tails of two phosphine ligands adjacent to the
hydrido ligand was observed, while no marked interactions
with the hydroxy group of neighboring molecules were
found. The O(H)‚‚‚Cl contacts (3.061 and 3.080 Å)11 are
shorter than those observed for RuCl2[PH(CH2OH)2]2[P(CH2-
OH)3]2 (3.142 and 3.226 Å).5a The Ru-Cl bond elongation
of 1 compared to the P(C6H5)2CH3 complex would be
ascribed to the bifurcate hydrogen-bonding interaction of the
chloro ligand.
ligands and two different sets of methylene protons at 4.54
2
and 4.25 ppm. The 31P signals observed at 15.5 (t, JPP
)
15.6 Hz) and 34.5 ppm (d, 2JPP ) 15.6 Hz) correspond to an
AX2 pattern with no fluxional behavior. The IR spectrum of
1 displayed a strong CO stretching band around 1940 cm-1,
as well as absorption of the Ru-H group at 2359 cm-1.
Single crystals suitable for an X-ray diffraction study were
obtained as solvates (1‚CH2Cl2) from a concentrated CH2Cl2
(5) (a) Higham, L.; Powell, A. K.; Whittlesey, M. K.; Wocadlo, S.; Wood,
P. T. Chem. Commun. 1998, 1107-1108. (b) Higham, L.; Whittlesey,
M. K.; Wood, P. T. Dalton Trans. 2004, 4202-4208.
(6) (a) Shibili, R.; Katti, K. V.; Volkert, W. A.; Barnes, C. L. Inorg. Chem.
2001, 40, 2358-2362. (b) Kothari, K. K.; Pillarsetty, N. K.; Katti, K.
V.; Volkert, W. A. Radiochim. Acta 2003, 91, 53-57.
(7) Kayaki, Y.; Suzuki, T.; Ikariya, T. Chem. Lett. 2001, 1016-1017.
(8) (a) Jessop, P. G.; Ikariya, T.; Noyori, R. Chem. ReV. 1999, 99, 475-
493. (b) Chemical Synthesis Using Supercritical Fluids; Jessop, P.
G., Leitner, W., Eds.; Wiley-VCH: Weinheim, Germany, 1999. (c)
Beckman, E. J. J. Supercrit. Fluids 2004, 28, 121-191.
(9) (a) Jessop, P. G.; Hsiao, Y.; Ikariya, T.; Noyori, R. J. Am. Chem.
Soc. 1994, 116, 8851-8852. (b) Jessop, P. G.; Hsiao, Y.; Ikariya, T.;
Noyori, R. J. Am. Chem. Soc. 1996, 118, 344-355.
To clarify the origin of the carbonyl moieties in the com-
plex 1, we prepared a 13C-labeled phosphine, P(C6H5)213CH2-
OH, from H13CHO and PH(C6H5)2 and examined the ligand-
exchange reaction using RuCl2[P(C6H5)3]3 (Scheme 3). In
the 13C{1H} NMR spectrum of the resulting complex, an
(10) Motevalli, M.; Hursthouse, M. B.; Barron, A. R.; Wilkinson, G. Acta
Crystallogr., Sect C 1987, 43, 214-216.
(11) The Cl(1)-H(14) and Cl(1)-H(27) distances are 2.36 and 2.37 Å,
respectively.
5792 Inorganic Chemistry, Vol. 46, No. 14, 2007

Ru(II) Complexes with Hydroxymethylphosphines
Scheme 3
enhanced signal from the carbonyl carbon was observed at
2
200.1 ppm with JCP ) 15.6 and 7.6 Hz, indicating the
formation of the 13C-enriched carbonyl complex. The coor-
dination of 13CO was further evidenced by the 13C-coupled
31P{1H} NMR signals at 15.5 (2JCP ) 7.6 Hz) and 34.5 ppm
(2JCP ) 15.3 Hz). On the basis of a well-known synthetic
procedure for hydrido(carbonyl)ruthenium complexes Ru-
(H)Cl(CO)L3 (L ) P(C6H5)3 and P(C6H5)2CH3) from form-
aldehyde and dichlororuthenium(II) complexes RuCl2L3,12
the carbonyl and hydrido ligands in 1 would be introduced
via the reverse process of the hydroxymethylphosphine
formation from formaldehyde and PH(C6H5)2. In fact,
elimination of a formaldehyde unit from hydroxymeth-
ylphosphine ligands has already been reported in synthetic
procedures of the [Pt{P(CH2OH)2CH2OP(CH2OH)2}2]Cl2,
RuCl2[PH(CH2OH)2]2[P(CH2OH)3]2, and RuCl2[PH(C6H5)-
(CH2OH)]2[P(C6H5)(CH2OH)2]2 complexes.4e,5
Figure 2. Molecular structure of Cp*RuCl[P(C6H5)2CH2OH]2‚CH2Cl2
(2a). Ellipsoids are shown at the 50% probability level for the non-hydrogen
atoms, other than the solvent molecule.
The hydrido(carbonyl) complex 1 was also successfully
synthesized in 56% yield from the reaction of trans-RuCl2-
(DMSO)4 with P(C6H5)2CH2OH in a 1:10 molar ratio in
CH2Cl2 for 3 h at room temperature (Scheme 4). Monitoring
the progress of this reaction at 0 °C by 31P{1H} NMR
spectroscopy showed an initially formed complex, RuCl2-
[P(C6H5)2CH2OH]3 (14.1 ppm), which gradually converted
into the carbonyl complex 1, indicating that the reaction
proceeds through the coordination of P(C6H5)2CH2OH to a
ruthenium(II) center, followed by its degradation and incor-
poration of the hydrido and carbonyl ligands.
The elimination of the formaldehyde unit from hydroxy-
methylphosphines was also observed in the ligand exchange
with PCy2CH2OH. The reaction of RuCl2[P(C6H5)3]3 with 4
molar equiv of PCy2CH2OH in ethanol at room temperature
for 1 h gave rise to a yellow compound formulated as trans-
RuCl2(PHCy2)4 in 79% yield as outlined in Scheme 5. The
1H NMR spectrum in CDCl3 exhibits a doublet signal
assigned to the secondary phosphine at 2.35 ppm with a large
1JPH coupling constant of 143.1 Hz. The hydroxymethyl
moiety of PCy2CH2OH was lost to give RuCl2(PHCy2)4,
whereas partial elimination of formaldehyde from the ligand
exchange with P(CH2OH)3 was observed and resulted in the
formation of RuCl2[PH(CH2OH)2]2[P(CH2OH)3]2.5
Figure 3. Molecular structure of Cp*RuCl[PCy(CH2OH)2]2 (2b). Only
one of the two independent molecules is shown. Ellipsoids are shown at
the 50% probability level for the non-hydrogen atoms, other than the solvent
molecule.
Coordination of Hydroxymethylphosphines to the
Cp*Ru System. In contrast to the reaction chemistry of
dichlororuthenium(II) complexes as discussed above, the
reaction of Cp*RuCl(isoprene) with hydroxymethylphos-
phines such as P(C6H5)2CH2OH, PCy(CH2OH)2 and P(CH2-
OH)3 in a 1:2 molar ratio at room temperature gave
bis(phosphine) complexes Cp*RuClL2 (2a-2c) as shown in
Scheme 6. In all cases, the 1H and 31P{1H} NMR spectra of
the reaction mixtures indicated formation of the correspond-
ing bis(phosphine) complexes without loss of the hydroxy-
methyl moiety.13
Figure 4. Schematic representation of the bimolecular interaction in
Cp*RuCl[P(C6H5)2CH2OH]2 (2a). The dashed lines indicate the hydrogen
bonds.
The molecular structures of complexes 2a and 2b were
determined by X-ray crystallographic analysis. These ORTEP
depictions are given in Figures 2 and 3, and selected bond
lengths and angles are summarized in Table 1. Both
complexes have a distorted octahedral geometry with Cp*,
(13) The loss of hydroxymethyl moiety was not observed similarly for
coordination of P(CH2OH)3 to Cp*RuCl(CO)2 under irradiation with
UV light in ref 4k.
(12) Levinson, J. J.; Robinson, S. D. J. Chem. Soc. A 1970, 2947-2954.
Inorganic Chemistry, Vol. 46, No. 14, 2007 5793

Kayaki et al.
Scheme 4
31P{1H}-NMR experiments at 25 °C revealed that the P(CH2-
OH)3 complex 2c is more soluble in D2O (>4.4 × 10-2 mol
L-1) than in C6D6 (∼1.6 × 10-4 mol L-1), whereas the
P(C6H5)2CH2OH complex 2a has appreciable solubility in
C6D6 (>0.11 mol L-1) and is sparingly soluble in D2O (∼6.3
× 10-5 mol L-1). Notably, the PCy(CH2OH)2 complex 2b
has amphiphilic nature in solution. Although it is hardly
soluble in D2O at 25 °C, an increase in the solution
temperature caused a significant improvement in the solubil-
ity up to 2.2 × 10-2 mol L-1 in D2O at 70 °C. The solid-
state structure of 2b as shown in Figure 5 implies that
formation of the intra- and intermolecular hydrogen bond
networks using all of the hydroxyl groups would contribute
to formation of a rigid bimolecular pair, thereby preventing
water molecules from approaching. Thus, the amphiphilic
property of the complex 2b was demonstrated by a compa-
rable solubility (1.5 × 10-2 mol L-1) in C6D6 at 70 °C.
Catalysis for Hydrogenative DMF Formation Using
scCO2. Synthesis of formic acid derivatives by hydrogenation
of CO2 using molecular catalysts represents one of the
promising methods for CO2 fixation into useful commodity
chemicals.15 In a number of experimental9b,16 and theoretical17
studies, it has been recognized that the ligand modulation
and the presence of protic cocatalysts such as water, alcohols,
and amines significantly influence the reaction profiles. The
presence of hydroxy moiety on the alkylphosphines may
provide positive effect on the CO2 hydrogenation catalyzed
by the Ru complexes.
Scheme 5
Scheme 6
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2a and 2b
2a·CH2Cl2
2ba
Ru-P
2.3247(9)
2.3136(9)
2.4778(7)
2.3340(6)
2.3256(6)
2.4940(7)
2.3315(6)
2.3297(6)
2.4918(7)
Ru-Cl
P-Ru-P
P-Ru-Cl
94.54(3)
88.37(3)
88.11(3)
99.13(2)
89.44(2)
87.57(2)
99.13(2)
89.84(2)
87.49(2)
a Two independent molecules were observed.
two phosphines, and chloro ligands. The structure of 2a is
similar to that of a related OH-free bis(phosphine) complex,
Cp*RuCl[P(C6H5)2CH3]3: both complexes are monoclinic
with the same space group (No. 14), although with different
settings (P21/n and P21/c, respectively).14 A slight increase
in the average Ru-P bond length of 2a (av 2.319 Å)
compared to that of the OH-free bis(phosphine) complex (av
2.310 Å) may reflect the greater steric effect or lower
electron-donating property of P(C6H5)2CH2OH compared to
that of P(C6H5)2CH3. The increased steric demands can also
be seen in the P-Ru-P bite angle of the P(C6H5)2CH2OH
complex (94.54°), being larger than that of the P(C6H5)2-
CH3 complex (93.02°).
The isolable hydroxymethylphosphine-ruthenium(II) com-
plexes were tested for the catalytic hydrogenative amidation
In contrast to the complex 1, the X-ray crystallography of
2a does not show the presence of intramolecular hydrogen
bond interactions through the hydroxy group, but each
molecule has a connected neighbor, as shown in Figure 4.
A distance of 3.142 Å for the O(H)‚‚‚Cl motif indicates the
presence of intermolecular hydrogen bonding, and therefore
the Ru-Cl bond in 2a may display a slightly longer distance
(2.4778 Å) than that in the P(C6H5)2CH3 complex (2.4522
Å). On the other hand, it is also found that the hydroxyl
moieties of 2b participate in intramolecular O(H)‚‚‚Cl
contacts (O‚‚‚Cl ) 3.035-3.078 Å) and partly contact with
two distinct adjacent hydroxy units (O‚‚‚O ) 2.819-3.083
Å), as shown in Figure 5.
The number of hydroxymethyl groups on the phosphine
ligands in complexes 2a-2c was found to influence the
1
solubility of the complexes in water. For example, H and
Figure 5. Schematic representation of the bimolecular interaction in
Cp*RuCl[PCy(CH2OH)2]2 (2b). The dashed lines indicate the hydrogen
bonds.
(14) Smith, D. C., Jr.; Haar, C. M.; Luo, L.; Li, C.; Cucullu, M. E.; Mahler,
C. H.; Nolan, S. P. Organometallics 1999, 18, 2357-2361.
5794 Inorganic Chemistry, Vol. 46, No. 14, 2007

Ru(II) Complexes with Hydroxymethylphosphines
Table 2. DMF Synthesis by Ruthenium Catalysts with
and P(CH2OH)3), have been prepared and characterized by
NMR spectroscopy and X-ray crystallographic analysis. The
elimination of the formaldehyde unit from hydroxymeth-
ylphosphines, P(C6H5)2CH2OH and PCy2CH2OH, proceeded
during the ligand exchange reaction with dichlororuthenium-
(II) species, RuCl2[P(C6H5)3]3 or trans-RuCl2(DMSO)4 to
give 1 and trans-RuCl2(PHCy2)4, respectively. The 13C-
labeling experiments revealed that the carbonyl moiety in 1
was originated from formaldehyde released from the hy-
droxymethylphosphine. On the other hand, degradation of
the hydroxymethyl moiety was not observed in the ligand
substitution of Cp*RuCl(isoprene) complex. Our current
study also demonstrates that the hydroxymethylphosphine
complexes, 1 and 2, serve as useful catalyst precursors for
hydrogenative amidation of scCO2 to afford DMF efficiently.
Hydroxymethylphosphinesa
run
Ru cat
TON
1
2
3
4
5
Ru(H)Cl(CO)[P(C6H5)2CH2OH]3, 1
RuCl2[PH(CH2OH)2]2[P(CH2OH)3]2
Cp*RuCl[P(C6H5)2CH2OH]2, 2a
Cp*RuCl[PCy(CH2OH)2]2, 2b
Cp*RuCl[P(CH2OH)3] 2, 2c
4800
9000
4100
3300
2100
b
a The reaction was conducted at 100 °C for 15 h, in a 50-mL reaction
vessel: Ru catalyst ) 4.7-5.3 × 10-3 mmol, [(CH3)2NH2]+[OCON(CH3)2]-
) 24 mmol, PH ) 8.4-8.6 MPa, total initial pressure ) 21.6-22.0 MPa.
b Ru catalyst )23.1 × 10-3 mmol, [(CH3)2NH2]+[OCON(CH3)2]- ) 15.5
mmol.
of scCO2 (Scheme 1). The reaction with the catalysts 1 and
2 was conducted under the standard conditions (T ) 100
°C, Ptotal ) 21.0-21.4 MPa, PCO ) 12.8-13.0 MPa, with
2
amine/catalyst molar ratio of 10 000:1) for comparison with
our previous results obtained with RuCl2[PH(CH2OH)2]2-
[P(CH2OH)3]2.7,18 The turnover numbers (TON) of the
reaction are summarized in Table 2. The catalyst performance
of new complexes 1 and 2 proved to be reliable for selective
DMF formation analogously to RuCl2[PH(CH2OH)2]2[P(CH2-
OH)3]2. It should be noted that the reaction using the hydrido-
(carbonyl) complex 1 resulted in a TON of 4800 after 15 h,
even though the presence of CO bound to ruthenium center
might suppress the catalysis.19 The intrinsic effect of hy-
droxymethylphosphines was also observed for the Cp*Ru
complexes. Although limited catalyst activity of cyclopen-
tadienyl-Ru complexes has been reported for the hydroge-
nation of CO2,20 the TON in the DMF formation using
Cp*RuCl(L)2 2a-2c ranged from 2100 to 4100, increasing
Experimental Section
General Procedures. All reactions and manipulations were
carried out under atmosphere of argon by using Schlenk techniques.
Solvents were freshly distilled under argon after they were dried
over an appropriate drying agent. Special grade liquefied carbon
dioxide (99.999% purity) was used as received without purification.
Diphenylphosphine was purchased from Tokyo Kasei Co., Ltd.,
and distilled before use. Other reagents were used as delivered
unless otherwise noted. RuCl2[P(C6H5)3]3,21 trans-RuCl2(DMSO)4,22
and Cp*RuCl(isoprene)23 were prepared according to the literature.
NMR spectra were recorded on a JEOL Lambda 300 spectrometer
for 1H (300.5 MHz, referenced to SiMe4 via residual solvent
protons), 13C{1H} (75.5 MHz, referenced to SiMe4 via the solvent
resonance), and 31P{1H} (121.7 MHz, referenced to 85% H3PO4
as an external standard) NMR. IR spectra were recorded on a Jasco
FT/IR-600 spectrometer. Elemental analyses were carried out using
a CHNS-932 (LECO) and SX-Elements Micro Analyzer VS-10
(Yanaco).
in the order of L ) P(CH2OH)3 < PCy(CH2OH)2
<
P(C6H5)2CH2OH.
Synthesis of Hydroxymethylphosphines. Caution: For safe
handling of the phosphine compounds, well-Ventilated laboratory
space and good fume hoods are required. P(C6H5)2CH2OH, PCy2-
CH2OH, and PCy(CH2OH)2 were prepared by reactions of the
corresponding secondary and primary phosphines with paraform-
aldehyde or aqueous formaldehyde according to the literature
methods.24 P(CH2OH)3 was prepared from P(CH2OH)4Cl following
the method reported in the literature.4d
P(C6H5)213CH2OH. Hydroxymethyldiphenylphosphine labeled
with 13C on the hydroxymethyl carbon was prepared from the
reaction of formaldehyde-13C. PH(C6H5)2 (0.562 g, 3.02 mmol) was
added to an aqueous solution of formaldehyde-13C (20% in H2O,
99 atom % 13C; 2.99 g, 3.85 mmol), and the mixture was stirred at
110 °C for 10 min. The reaction mixture was allowed to cool to
room temperature and was evaporated under reduced pressure to
give a colorless liquid as an analytically pure compound, quanti-
tatively (0.654 g, 3.01 mmol). The 13C{1H} NMR spectrum was
Conclusions
A range of the novel ruthenium(II) complexes bearing
hydroxymethylphosphines, Ru(H)Cl(CO)[P(C6H5)2CH2OH]3
1 and Cp*RuCl(L)2 2 (L ) P(C6H5)2CH2OH, PCy(CH2OH)2,
(15) (a) Jessop, P. G.; Joo´, F.; Tai, C.-C. Coord. Chem. ReV. 2004, 248,
2425-2442. (b) Jessop, P. G.; Ikariya, T.; Noyori, R. Chem. ReV.
1995, 95, 259-272. (c) Leitner, W. Angew. Chem., Int. Ed. Engl. 1995,
34, 2207-2221.
(16) (a) Tsai, J.-C.; Nicholas, K. M. J. Am. Chem. Soc. 1992, 114, 5117-
5124. (b) Yin, C.; Xu, Z.; Yang, S.-Y.; Ng, S. M.; Wong, K. Y.; Lin,
Z.; Lau, C. P. Organometallics 2001, 20, 1216-1222. (c) Thomas,
C. A.; Bonilla, J.; Huang, Y.; Jessop, P. G. Can. J. Chem. 2001, 79,
719-724. (d) Munshi, P.; Main, A. D.; Linehan, J. C.; Tai, C.-C.;
Jessop, P. G. J. Am. Chem. Soc. 2002, 124, 7963-7971. (e) Tai, C.-
C.; Pitts, J.; Linehan, J. C.; Main, A. D.; Munshi, P.; Jessop, P. G.
Inorg. Chem. 2002, 41, 1606-1614. (f) Koike, T.; Ikariya, T. AdV.
Synth. Catal. 2004, 346, 37-41.
(17) (a) Musashi, Y.; Sakaki, S. J. Am. Chem. Soc. 2000, 122, 3867-
3877. (b) Matsubara, T. Organometallics 2001, 20, 19-24. (c)
Matsubara, T.; Hirao, K. Organometallics 2001, 20, 5759-5768. (d)
Ohnishi, Y.; Matsunaga, T.; Nakao, Y.; Sato, H.; Sakaki, S. J. Am.
Chem. Soc. 2005, 127, 4021-4032.
(21) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,
12, 237-240.
(22) James, B. R.; Ochiai, E.; Rempel. G. L. Inorg. Nucl. Chem. Lett. 1971,
7, 781-784.
(23) (a) Masuda, K.; Ohkita, H.; Kurumatani, S. Itoh K. Organometallics
1993, 12, 2221-2226. (b) Fagan, P. J.; Mahoney, W. S.; Calabrese,
J. C.; Williams, I. D. Organometallics 1990, 9, 1843-1852.
(24) (a) Hellmann, H.; Bader, J.; Birkner, H.; Schumacher, O. Liebigs
Ann. Chem. 1962, 659, 49-63. (b) Ku¨hl, O.; Blaurock, S.; Sieler, J.;
Hey-Hawkins, E. Polyhedron 2001, 20, 2171-2177. (c) Gon-
schorowsky, M.; Merz, K.; Driess, M. Eur. J. Inorg. Chem. 2006,
455-463.
(18) We employed [(CH3)2NH2]+[OCON(CH3)2]- as a convenient and
reproducible dimethylamino source alternative to dimethylamine.
(19) Zhang, J. Z.; Li, Z.; Wang, H.; Wang, C. Y. J. Mol. Catal. A: Chem.
1996, 112, 9-14.
(20) Synthesis of formic acid by using CpRu complexes has been reported
by Lau’s group. (a) For [{C5H4(CH2)3NMe2}Ru(dppm)]BF4 (TON )
8), Chu, H. S.; Lau, C. P.; Wong, K. Y. Organometallics 1998, 17,
2768-2777. (b) For CpRu(CO)(µ-dppm)Mo(CO)2Cp (TON ) 43),
Man, M. L.; Zhou, S. M.; Ng, S. M.; Lau, C. P. Dalton Trans. 2003,
3727-3735.
Inorganic Chemistry, Vol. 46, No. 14, 2007 5795

Kayaki et al.
identical to that of the unlabeled P(C6H5)2CH2OH, except that the
peak at 63.0 ppm was greatly increased in intensity, consistent with
13C labeling of the hydroxymethyl carbon. The doublet signal at
-10.2 ppm (1JCP ) 14.7 Hz) in 31P NMR was consistent with the
phosphorus atom attached to the labeled carbon. 1H NMR
[P(C6H5)2CH2OH]3 and free P(C6H5)2CH2OH were observed at 14.1
and -10.4 ppm, respectively. Repeated recrystallization of the
products from THF-ether at -20 °C yielded an orange solid
formulated as RuCl2[P(C6H5)2CH2OH]3‚2(C4H8O). Yield: 3%
1
(0.027 g, 0.028 mmol). H NMR (300.5 MHz, CD2Cl2): δ 2.46
2
(CD2Cl2): δ 1.64 (brs, OH, 1 H), 4.40 (ddd, CH2, JHC ) 145.8
(br, OH, 3 H), 4.95 (m, CH2, 6 H), 7.0-7.8 (m, C6H5, 15 H). 31P-
{1H} NMR (121.7 MHz, CD2Cl2): δ 14.1 (s). Anal. Calcd for
C47H55Cl2O5P3Ru: C, 58.51; H, 5.75. Found: C, 59.06; H, 5.69.
Formation of RuCl2(PHCy2)4 from PCy2(CH2OH) and RuCl2-
(PPh3)3. PCy2(CH2OH) (1.97 g, 7.58 mmol) was dissolved in
ethanol (10 mL) and slowly added to RuCl2[P(C6H5)3]3 (1.82 g,
1.90 mmol) in ethanol (25 mL). After the mixture was stirred for
30 min at room temperature, the resultant precipitate was filtered
off, washed with ether (10 mL × 3), and dried in vacuo to yield a
bright yellow powder of RuCl2(PHCy2)4. Yield: 79% (1.45 g, 1.50
2
3
Hz, JHP ) 8.3 Hz, JHH ) 5.6 Hz, 2 H), 7.32-7.40 (m, C6H5, 6
H), 7.44-7.51 (m, C6H5, 4 H). 13C{1H} NMR (CD2Cl2): δ 63.0
(d, 1JCP ) 14.5 Hz), 129.0 (d, JCP ) 6.5 Hz), 129.3, 133.5 (dd, JCP
) 17.9, JCC ) 2.3 Hz), 135.6 (d, JCP ) 11.7 Hz). 31P{1H} NMR
1
(CD2Cl2): δ -10.2 (d, JCP ) 14.7 Hz).
Synthesis of Ru(H)Cl(CO)[P(C6H5)2CH2OH]3 (1). Method A.
A solution of P(C6H5)2CH2OH (0.796 g, 3.68 mmol) in 2 mL of
CH2Cl2 was added to a stirred solution of RuCl2[P(C6H5)3]3 (1.19
g, 1.24 mmol) in 10 mL of CH2Cl2. The resulting mixture was
stirred at room temperature for 36 h. The product was formed as a
white precipitate, which was collected by filtration, washed with
ether (5 mL × 3), and dried under vacuum. Yield: 42% (0.427 g,
0.524 mmol). After recrystallization from CH2Cl2, colorless crystals
formulated as Ru(H)Cl(CO)[P(C6H5)2CH2OH]3‚CH2Cl2 were ob-
tained. Method B. P(C6H5)2CH2OH (2.14 g, 9.91 mmol) was
dissolved in CH2Cl2 (5 mL) and added slowly to a solution (30
mL) of trans-RuCl2(DMSO)4 (0.487 g, 1.01 mmol) in the same
solvent. After the mixture was stirred for 18 h at room temperature,
the white precipitate was collected by filtration and washed with
ether (5 mL × 3) to give the analytically pure compound 1. Yield:
56% (0.464 g, 0.570 mmol). mp: 176.3 °C (dec). 1H NMR (300.5
1
mmol). H NMR (300.5 MHz, CDCl3): δ 1.18-1.82 (m, C6H11,
44 H), 2.35 (d, PHCy2, 1JHP ) 143.1 Hz, 4 H). 31P{1H} NMR (121.7
MHz, CDCl3): δ 12.8 (s). Anal. Calcd for C48H92Cl2P4Ru: C,
59.74; H, 9.61. Found: C, 59.46; H, 9.52. The analytical data is
also in good agreement with that found in the literature.25
Synthesis of Cp*RuCl[P(C6H5)2CH2OH]2 (2a). P(C6H5)2CH2-
OH (0.435 g, 2.01 mmol) was dissolved in THF (2 mL), and the
mixture was added slowly to a THF solution (10 mL) of Cp*RuCl-
(isoprene) (0.345 g, 1.02 mmol). After the mixture was stirred for
36 h at room temperature, the solvent was removed under vacuum.
The obtained residue was washed with n-hexane (5 mL) and ether
(5 mL) to give the analytically pure compound 2a. Yield: 88%
(0.629 g, 0.893 mmol). Orange crystals suitable for X-ray crystal-
lographic analysis were obtained as solvates, Cp*RuCl[P(C6H5)2-
CH2OH]2‚CH2Cl2, by slow diffusion of hexane into their solutions
of in CH2Cl2. mp: 189.6 °C (dec). 1H NMR (300.5 MHz,
2
MHz, CD2Cl2): δ -6.65 (dt, RuH, JHP ) 101.6, 20.6 Hz, 1 H),
3
3
1.97 (td, OH, JHH ) 6.9 Hz, JHP ) 2.7 Hz, 1 H), 3.75 (dd, OH,
3JHH ) 6.9 Hz, 8.0 Hz, 2 H), 4.28 (dd, CH2, JHH ) 6.6 Hz, JHP
) 4.8 Hz, 2 H), 4.54 (m, CH2, 2 H), 4.75-4.89 (m, CH2, 2 H),
7.09-7.44 (m, C6H5, 26 H), 7.74-7.85 (m, C6H5, 4 H). 13C{1H}
NMR (75.6 MHz, CDCl3): δ 61.2 (d, CH2, 1JCP ) 21.4 Hz), 64.6
3
2
4
CD2Cl2): δ 1.21 (t, CH3, JHP ) 1.5 Hz, 15 H), 3.01 (br, OH, 2
H), 4.04 (m, CH2, 4 H), 7.18-7.46 (m, C6H5, 20 H). 13C{1H} NMR
(75.6 MHz, CD2Cl2): δ 9.50 (s, CH3), 64.6 (s, CH2), 89.7 (t, C5-
1
3
(vt, CH2, JCP + JCP ) 15.6 Hz), 128.9-136.1 (m, C6H5), 201.7
(dt, 2JCP ) 15.3, 7.3 Hz). 31P{1H} NMR (121.7 MHz, CD2Cl2): δ
15.5 (t, 2JPP ) 15.6 Hz), 34.5 (d, 2JPP ) 15.6 Hz). IR (cm-1, KBr):
ν 3390 (O-H), 3334 (O-H), 2359 (Ru-H), 1940 (CdO). Calcd
for C40H40ClO4P3Ru: C, 59.01; H, 4.95. Found: C, 59.09; H, 4.85.
Reaction of RuCl2[P(C6H5)3]3 with P(C6H5)213CH2OH. The
reaction of P(C6H5)213CH2OH (0.654 g, 3.01 mmol) with RuCl2-
[P(C6H5)3]3 (0.936 g, 0.976 mmol) was performed in a manner
similar to that given above for unlabeled P(C6H5)2CH2OH. Yield:
32% (0.259 g, 0.317 mmol). The 13C{1H} NMR spectrum of the
product was identical to that obtained in the experiment using
unlabeled phosphine, except that the signals at 61.2, 64.6, and 201.5
ppm were greatly increased in intensity. The 31P resonances at 15.5
and 34.5 ppm were coupled with the labeled 13C atoms of the
carbonyl ligand and hydroxymethyl carbons. 1H NMR (300.5 MHz,
2
(CH3)5, JCP ) 1.9 Hz), 127.9 (m, C6H5), 128.6 (m, C6H5), 129.6
(s, C6H5), 129.9 (s, C6H5), 132.7 (m, C6H5), 134.1 (m, C6H5), 136.0
(m, C6H5), 137.1 (m, C6H5). 31P{1H} NMR (121.7 MHz, CD2Cl2):
δ 33.7 (s). Anal. Calcd for C36H41ClO2P2Ru: C, 61.40; H, 5.87;
Cl, 5.03. Found: C, 60.99; H, 5.93; Cl, 5.12.
Synthesis of Cp*RuCl[PCy(CH2OH)2]2 (2b). PCy2CH2OH
(0.353 g, 2.00 mmol) was dissolved in CH2Cl2 (2 mL), and it was
added slowly to a solution (10 mL) of Cp*RuCl(isoprene) (0.333
g, 0.98 mmol) in the same solvent. After the mixture was stirred
for 14 h at room temperature, the solvent was removed under
vacuum. The residue was washed with ether (10 mL × 3) to give
the analytically pure compound 2b. Yield: 80% (0.490 g, 0.785
mmol). After recrystallization from CH2Cl2/hexane, red crystals
1
were obtained. mp: 145.9 °C (dec). H NMR (300.5 MHz, CD2-
2
2
Cl2): δ 1.13-2.07 (m, C6H11, 22 H), 1.61 (t, CH3, 4JHP ) 1.4 Hz,
15 H), 3.36 (br, OH, 2 H), 3.47 (br, OH, 2 H), 4.05-4.49 (m,
CH2, 8 H). 13C{1H} NMR (75.6 MHz, CD2Cl2): δ 10.2 (s, CH3),
26.3 (s, C6H11), 27.8 (m, C6H11), 29.3 (s, C6H11), 40.0 (vt, CHOH,
CD2Cl2): δ -6.69 (ddt, RuH, JHP ) 101.1 and 21.8 Hz, JHC
)
6.59 Hz, 1 H), 1.93 (br, OH, 1 H), 3.74 (m, OH, 2 H), 4.25 (m,
1
1
CH2, JHC ≈ 149 Hz, 2 H), 4.55 (m, CH2, JHC ≈ 148 Hz, 2 H),
1
4.76 (m, CH2, JHC ≈ 148 Hz, 2 H), 7.06-7.39 (m, C6H5, 26 H),
7.64-7.80 (m, C6H5, 4 H). 31P{1H} NMR (121.7 MHz, CD2Cl2):
3
2
1JCP + JCP ) 9.9 Hz), 60.4 (m, CH2), 88.2 (t, C5(CH3)5, JCP
)
2
1
2
1.9 Hz). 31P{1H} NMR (121.7 MHz, CD2Cl2): δ 34.3 (s). Anal.
Calcd for C26H49ClO4P2Ru: C, 50.03; H, 7.91; Cl, 5.68. Found:
C, 50.07; H, 7.30; Cl, 5.90.
δ 15.5 (tdd, JPP ) 15.6, JCP ) 21.4 Hz, JCP ) 7.6 Hz), 34.5
2
1
2
(ddd, JPP ) 15.6, JCP ) 15.6 Hz, JCP ) 15.3 Hz).
Formation of RuCl2[P(C6H5)2CH2OH]3 by the Ligand Ex-
change of RuCl2(dmso)4 with P(C6H5)2(CH2OH). A solution of
P(C6H5)2CH2OH (2.10 g, 9.71 mmol) in 5 mL of CH2Cl2 was added
to a stirred solution of trans-RuCl2(DMSO)4 (0.484 g, 1.00 mmol)
in 25 mL of CH2Cl2. After the mixture was stirred at 0 °C for 10
min, the solvent was removed under a reduced pressure. The residue
was dissolved in CD2Cl2 and transferred to a NMR tube under Ar.
In the 31P{1H} NMR spectrum, the singlet signals for RuCl2-
Synthesis of Cp*RuCl[P(CH2OH)3]2 (2c). A THF (15 mL)
solution of Cp*RuCl(isoprene) (0.643 g, 1.89 mmol) was added to
P(CH2OH)3 (0.473 g, 3.81 mmol) in THF (15 mL) and stirred at
room temperature for 34 h. The solvent was removed under vacuum,
(25) Moers, F. G.; Thewissen, D. H. M. W.; Steggerda, J. J. J. Inorg. Nucl.
Chem. 1977, 39, 1321-1322.
5796 Inorganic Chemistry, Vol. 46, No. 14, 2007

Ru(II) Complexes with Hydroxymethylphosphines
Table 3. Crystallographic Data for 1, 2a, and 2b
1‚CH2Cl2 2a·CH2Cl2
C41H42Cl3O4P3Ru C37H43Cl3O2P2Ru C26H49ClO4P2Ru
and the obtained residue was washed with cold acetone (3 mL)
and ether (10 mL) to give the analytically pure compound 2c.
Yield: 60% (0.586 g, 1.13 mmol). mp: 161.8 °C (dec).1H NMR
(300.5 MHz, CD2Cl2): δ 1.69 (t, CH3, 4JHP ) 1.5 Hz, 15 H), 3.84
(br, CH2, 6 H), 4.24 (dd, JHP ) 14.4 and 15.7 Hz, 12 H). 13C{1H}
NMR (75.6 MHz, acetone-d6): δ 11.0 (s, CH3), 59.1 (vt, CH2OH,
1JCP + 3JCP ) 13.4 Hz), 89.9 (t, C5(CH3)5, 2JCP ) 2.1 Hz). 31P{1H}
NMR (121.7 MHz, acetone-d6): δ 36.0 (s). Anal. Calcd for C16H33-
ClO6P2Ru: C, 36.96; H, 6.40; Cl, 6.82. Found: C, 36.76; H, 6.26;
Cl, 7.02.
2b
formula
fw
899.13
colorless
173
789.12
orange
193
624.14
orange
193
color
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c (No. 14)
12.699(4)
20.240(6)
15.276(5)
96.060(3)
3904.6(20)
4
monoclinic
P21/n (No. 14)
11.901(6)
17.515(9)
17.487(8)
94.339(7)
3634.6(30)
4
monoclinic
P21/c (No. 14)
20.689(9)
13.894(6)
20.617(10)
102.489(6)
5786.3(45)
8
â (deg)
V (Å3)
Z
X-ray Structure Determinations of 1, 2a, and 2b. All measure-
ments were made on a Rigaku Saturn CCD area detector equipped
with graphite-monochromated Mo KR radiation (λ ) 0.71070 Å)
under a nitrogen stream at 193 K. Indexing was performed from
seven images that were exposed for 3 s. The crystal-to-detector
distance was 45.05 mm. The data were collected to a maximum
2θ value of 54.9°. A total of 720 oscillation images were collected.
A sweep of data was carried out using ω scans from -110.0 to
70.0° in 0.5° steps, at ø ) 45.0° and φ ) 0.0°. A second sweep
was performed using ω scans from -110.0 to 70.0° in 0.5° steps,
at ø ) 45.0° and φ ) 90.0°. The exposure rate was 3.0 s/deg, and
the detector swing angle was -19.86°. Intensity data were collected
for Lorentz-polarization effects as well as absorption. Structure solu-
tion and refinements were performed with the CrystalStructure
program package. The heavy atom positions were determined by a
direct program method (SIR92), and the remaining non-hydrogen
atoms were found by subsequent Fourier techniques (DIRDIF99).
An empirical absorption correction based on equivalent reflections
was applied to all data. All non-hydrogen atoms were refined ani-
sotropically by full-matrix least-square techniques based on F2. The
low-temperature data collection enabled hydrogens attached to the
oxygens and ruthenium center in 1 to be located from the Fourier
difference map and refined isotropically. All other hydrogens either
were not refined or were constrained to ride on their parent atom.
Relevant crystallographic data are compiled in Table 3.
D
calcd (g cm-3
)
1.529
1.442
1.433
F000
1840
1624
7.71
29 079
28 562
[Rint ) 0.071]
449
0.076
0.219
1.003
2624
7.74
46 131
45 061
[Rint ) 0.053]
711
0.049
0.149
µ(Mo KR) (cm-1) 7.71
measured reflns 30 257
unique reflns
29 803
[Rint ) 0.031]
variable params 523
R1a [I>2σ(I)]
wR2b (all data)
GOF on F2
0.039
0.108
0.991
0.885
a R1 ) (∑||Fo| - |Fc||)/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc )2]/∑w(Fo )2]1/2
.
2
2
valve with a syringe pump (ISCO model 260D), and the mixture
was stirred for 30 min. After the mixture reached a steady state,
H2 gas was introduced with the syringe pump up to the total pressure
of 21.0-21.4 MPa. After the mixture was stirred for 15 h, the
reactor was cooled in a bath of methanol with dry ice. The gaseous
matter was vented, and the reactor was slowly warmed to the room
1
temperature. The yields of DMF were determined by H NMR
analyses using durene as an internal standard.
Acknowledgment. This work was financially supported
by a Grant-in-Aid from the Ministry of Education, Culture,
Sports, Science and Technology, Japan (No. 14078209,
17655067, 18065007) and partially supported by The 21st
Century COE Program. Financial support from the Kurita
Water and Environment Foundation is also gratefully ac-
knowledged.
Catalytic Hydrogenative Amidation of CO2. Caution: Opera-
tors of high-pressure equipment should take proper precautions to
minimize the risk of personal injury. A stainless steel reactor was
charged with argon gas and was placed in the oven at 100 °C before
the introduction of reagents. A mixture of [(CH3)2NH2]+-
[OCON(CH3)2]- (24.0 mmol) and ruthenium catalyst (4.7-5.3 ×
10-3 mmol) was transferred into the reactor with a syringe through
an opening against the flow of CO2. Subsequently, the reactor was
charged with CO2 to the pressure of 12.6-12.8 MPa through a
Supporting Information Available: Crystallographic data for
1, 2a, and 2b in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC700470N
Inorganic Chemistry, Vol. 46, No. 14, 2007 5797